1
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Major MR, McKee GR, Geiger B, Hartog DJD, Jaehnig K, Seyfert C, Smith DR, Stewart SD, Yan Z. Pedestal fluctuation measurements with charge exchange imaging at the DIII-D tokamak. Rev Sci Instrum 2022; 93:113503. [PMID: 36461537 DOI: 10.1063/5.0101844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 09/20/2022] [Indexed: 06/17/2023]
Abstract
A new high radial resolution 2D multichannel Charge eXchange Imaging (CXI) diagnostic is under development for deployment at DIII-D. The diagnostic system will measure low-to-intermediate radial wavenumber carbon density fluctuations by observing the n = 8 - 7 (λ = 529.06 nm) C-VI emission line, resulting from charge exchange collisions between heating neutral beam atoms and the intrinsic carbon ion density. The new CXI diagnostic will provide measurements with ΔR ∼ 0.4 cm to access higher kr instabilities (kr < 8 cm-1) predicted to arise in the steep-gradient region of the H-mode pedestal. The CXI system will feature 60 fiber bundles in a 12 × 5 arrangement, with each bundle consisting of four 1 mm fibers. A custom optical system has been designed to filter and image incoming signals onto an 8 × 8 avalanche photodiode array. Additionally, a novel electronics suite has been designed and commissioned to amplify and digitize the relatively low-intensity carbon signal at a 2 MHz bandwidth. Forward modeling results of the active C-VI emission suggest sufficient signal to noise ratios to resolve turbulent fluctuations. Prototype measurements demonstrate the ability to perform high frequency pedestal measurements.
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Affiliation(s)
- M R Major
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - G R McKee
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - B Geiger
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - K Jaehnig
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - C Seyfert
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - D R Smith
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - S D Stewart
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
| | - Z Yan
- University of Wisconsin-Madison, Madison, Wisconsin 53707, USA
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2
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Funaba H, Yasuhara R, Uehara H, Yamada I, Sakamoto R, Osakabe M, Den Hartog DJ. Electron temperature and density measurement by Thomson scattering with a high repetition rate laser of 20 kHz on LHD. Sci Rep 2022; 12:15112. [PMID: 36068266 PMCID: PMC9448754 DOI: 10.1038/s41598-022-19328-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 08/29/2022] [Indexed: 11/30/2022] Open
Abstract
Thomson scattering measurements with a high-repetition-rate laser have commenced in the Large Helical Device. As an example of the fast phenomena captured by this diagnostic system, measurements at a 20 kHz repetition-rate in hydrogen pellet-injected plasmas are presented. Signal processing methods for this measurement have been developed and electron temperature profiles with almost 70 spatial points were evaluated at time intervals of 50 [Formula: see text]s. After Raman scattering calibration, electron density profiles were derived. Fast changes in the electron temperature and density profiles within 1 ms were observed.
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Affiliation(s)
- H Funaba
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan.
| | - R Yasuhara
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan.
| | - H Uehara
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan
| | - I Yamada
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan
| | - R Sakamoto
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan
| | - M Osakabe
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu, 509-5292, Japan
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706-1390, USA
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3
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Kenmochi N, Ida K, Tokuzawa T, Yasuhara R, Funaba H, Uehara H, Den Hartog DJ, Yamada I, Yoshinuma M, Takemura Y, Igami H. Preceding propagation of turbulence pulses at avalanche events in a magnetically confined plasma. Sci Rep 2022; 12:6979. [PMID: 35577787 PMCID: PMC9110360 DOI: 10.1038/s41598-022-10499-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/11/2022] [Indexed: 11/09/2022] Open
Abstract
The preceding propagation of turbulence pulses has been observed for the first time in heat avalanche events during the collapse of the electron internal transport barrier (e-ITB) in the Large Helical Device. The turbulence and heat pulses are generated near the foot of the e-ITB and propagate to the peripheral region within a much shorter time than the diffusion timescale. The propagation speed of the turbulence pulse is approximately 10 km/s, which is faster than that of the heat pulse propagating at a speed of 1.5 km/s. The heat pulse propagates at approximately the same speed as that in the theoretical prediction, whereas the turbulence pulse propagates one order of magnitude faster than that in the prediction, thereby providing important insights into the physics of non-local transport.
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4
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Delgado-Aparicio LF, VanMeter P, Barbui T, Chellai O, Wallace J, Yamazaki H, Kojima S, Almagari AF, Hurst NC, Chapman BE, McCollam KJ, Den Hartog DJ, Sarff JS, Reusch LM, Pablant N, Hill K, Bitter M, Ono M, Stratton B, Takase Y, Luethi B, Rissi M, Donath T, Hofer P, Pilet N. Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST. Rev Sci Instrum 2021; 92:073502. [PMID: 34340413 DOI: 10.1063/5.0043672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 04/26/2021] [Indexed: 06/13/2023]
Abstract
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.
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Affiliation(s)
| | - P VanMeter
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - T Barbui
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - O Chellai
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - J Wallace
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - H Yamazaki
- National Institutes for Quantum and Radiological Science and Technology, Naka, Ibaraki 311-0193, Japan
| | - S Kojima
- Kyushu University, Kasuga-kouen 6-1, Kasuga, Japan
| | - A F Almagari
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - N C Hurst
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - B E Chapman
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - K J McCollam
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L M Reusch
- Edgewood College, Madison, Wisconsin 53711, USA
| | - N Pablant
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - K Hill
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - M Bitter
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - M Ono
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B Stratton
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - Y Takase
- The University of Tokyo, Kashiwa 277-8561, Japan
| | - B Luethi
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - M Rissi
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - T Donath
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - P Hofer
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - N Pilet
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
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5
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Eckart ME, Beiersdorfer P, Brown GV, Den Hartog DJ, Hell N, Kelley RL, Kilbourne CA, Magee EW, Mangoba AEY, Nornberg MD, Porter FS, Reusch LM, Wallace JP. Microcalorimeter measurement of x-ray spectra from a high-temperature magnetically confined plasma. Rev Sci Instrum 2021; 92:063520. [PMID: 34243585 DOI: 10.1063/5.0043980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/29/2021] [Indexed: 06/13/2023]
Abstract
A NASA-built x-ray microcalorimeter spectrometer has been installed on the MST facility at the Wisconsin Plasma Physics Laboratory and has recorded x-ray photons emitted by impurity ions of aluminum in a majority deuterium plasma. Much of the x-ray microcalorimeter development has been driven by the needs of astrophysics missions, where imaging arrays with few-eV spectral resolution are required. The goal of our project is to adapt these single-photon-counting microcalorimeters for magnetic fusion energy research and demonstrate the value of such measurements for fusion science. Microcalorimeter spectrometers combine the best characteristics of the x-ray instrumentation currently available on fusion devices: high spectral resolution similar to an x-ray crystal spectrometer and the broadband coverage of an x-ray pulse height analysis system. Fusion experiments are increasingly employing high-Z plasma-facing components and require measurement of the concentration of all impurity ion species in the plasma. This diagnostic has the capability to satisfy this need for multi-species impurity ion data and will also contribute to measurements of impurity ion temperature and flow velocity, Zeff, and electron density. Here, we introduce x-ray microcalorimeter detectors and discuss the diagnostic capability for magnetic fusion energy experiments. We describe our experimental setup and spectrometer operation approach at MST, and we present the results from an initial measurement campaign.
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Affiliation(s)
- M E Eckart
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - P Beiersdorfer
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - G V Brown
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D J Den Hartog
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - N Hell
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - R L Kelley
- X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
| | - C A Kilbourne
- X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
| | - E W Magee
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - A-E Y Mangoba
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M D Nornberg
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - F S Porter
- X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
| | - L M Reusch
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J P Wallace
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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6
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VanMeter PD, Delgado-Aparicio LF, Reusch LM, Den Hartog DJ. Robust analysis of space-, time-, and energy-resolved soft x-ray measurements of magnetically confined fusion plasmas (invited). Rev Sci Instrum 2021; 92:053549. [PMID: 34243280 DOI: 10.1063/5.0043787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/03/2021] [Indexed: 06/13/2023]
Abstract
A novel compact multi-energy soft x-ray (ME-SXR) diagnostic based on the PILATUS3 100K x-ray detector has been developed in collaboration between the Princeton Plasma Physics Laboratory and the University of Wisconsin-Madison and tested on the Madison Symmetric Torus (MST) reversed-field pinch. This solid-state photon-counting detector consists of a two-dimensional array of ∼100 000 pixels for which the lower photon absorption cutoff energy can be independently set, allowing it to be configured for a unique combination of simultaneous spatial, spectral, and temporal resolution of ∼1 cm, 100 eV, and 500 Hz, respectively. The diagnostic is highly versatile and can be readily adapted to diverse plasma operating conditions and scientific needs without any required downtime. New results from improved-confinement and quasi-single helicity plasmas in the MST demonstrate how the detector can be applied to study multiple aspects of the evolution of magnetically confined fusion-grade plasmas. These include observing the evolution of thermal emissivity, characterizing the energy of mid-Z excitation lines, extracting the Te profile, and observing the evolution of non-thermal populations. A technique for integrating the ME-SXR diagnostic into an integrated data analysis framework based on Bayesian inference is also presented. This allows ME-SXR measurements to be combined with data for complementary diagnostics in order to simultaneously infer Te and nZ from all available information.
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Affiliation(s)
- P D VanMeter
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | | | - L M Reusch
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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7
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Nishizawa T, Nornberg MD, Boguski J, Den Hartog DJ, Sarff JS, Williams ZR, Xing ZA, Craig D. Measurements of Impurity Transport Due to Drift-Wave Turbulence in a Toroidal Plasma. Phys Rev Lett 2018; 121:165002. [PMID: 30387678 DOI: 10.1103/physrevlett.121.165002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/11/2018] [Indexed: 06/08/2023]
Abstract
The first direct measurements of an impurity particle flux driven by drift-wave turbulence in a toroidal magnetized plasma are reported. The correlation between the impurity density and radial velocity fluctuations is measured using ion Doppler spectroscopy. The small, very fast radial velocity fluctuation is resolved with the aid of a new linearized spectrum correlation analysis method that rejects uncorrelated noise as the sample size increases. The measured C^{2+} turbulent impurity flux in the edge of the plasma is directed inward and is consistent with impurity density measurements. This is also the first direct evidence for fluctuation-induced transport due to trapped-electron-mode turbulence in reversed field pinch plasmas.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Boguski
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z R Williams
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z A Xing
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D Craig
- Department of Physics, Wheaton College, Wheaton, Illinois 60187, USA
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8
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Reusch LM, Nornberg MD, Goetz JA, Den Hartog DJ. Using integrated data analysis to extend measurement capability (invited). Rev Sci Instrum 2018; 89:10K103. [PMID: 30399657 DOI: 10.1063/1.5039349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/12/2018] [Indexed: 06/08/2023]
Abstract
The analysis approach called integrated data analysis (IDA) provides a means to exploit all information present in multiple streams of raw data to produce the best inference of a plasma parameter. This contrasts with the typical approach in which information (data) from a single diagnostic is used to measure a given parameter, e.g., visible bremsstrahlung → Z eff. Data from a given diagnostic usually contain information on many parameters. For example, a Thomson scattering diagnostic is sensitive to bremsstrahlung and line emission in addition to electron temperature. This background light is typically subtracted off and discarded but could be used to improve knowledge of Z eff. IDA encourages explicit awareness of such information and provides the quantitative framework to exploit it. This gives IDA the ability to increase spatial and temporal resolution, increase precision and accuracy of inferences, and measure plasma parameters that are difficult or impossible to measure using single diagnostic techniques. One example is the measurement of Z eff on Madison symmetric torus using IDA since no single diagnostic can provide a robust measurement. As we enter the burning plasma era, application of IDA will be critical to the measurement of certain parameters, as diagnostic access in the harsh fusion environment will be extremely limited.
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Affiliation(s)
- L M Reusch
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J A Goetz
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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9
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Reusch LM, Franz P, Den Hartog DJ, Goetz JA, Nornberg MD, VanMeter P. Model Validation for Quantitative X-Ray Measurements. Fusion Science and Technology 2018. [DOI: 10.1080/15361055.2017.1404340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- L. M. Reusch
- University of Wisconsin–Madison, Department of Physics, Madison, Wisconsin 53706
| | - P. Franz
- Consorzio RFX, EURATOM-ENEA Association, Padova, Italy
| | - D. J. Den Hartog
- University of Wisconsin–Madison, Department of Physics, Madison, Wisconsin 53706
| | - J. A. Goetz
- University of Wisconsin–Madison, Department of Physics, Madison, Wisconsin 53706
| | - M. D. Nornberg
- University of Wisconsin–Madison, Department of Physics, Madison, Wisconsin 53706
| | - P. VanMeter
- University of Wisconsin–Madison, Department of Physics, Madison, Wisconsin 53706
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10
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Nornberg MD, Den Hartog DJ, Reusch LM. Incorporating Beam Attenuation Calculations into an Integrated Data Analysis Model for Ion Effective Charge. Fusion Science and Technology 2018. [DOI: 10.1080/15361055.2017.1387008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- M. D. Nornberg
- University of Wisconsin-Madison, Department of Physics, Madison, Wisconsin 53706
| | - D. J. Den Hartog
- University of Wisconsin-Madison, Department of Physics, Madison, Wisconsin 53706
| | - L. M. Reusch
- University of Wisconsin-Madison, Department of Physics, Madison, Wisconsin 53706
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11
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Anderson JK, Almagri AF, Chapman BE, Davydenko Y, Deichuli P, Den Hartog DJ, Forest CB, Fiksel G, Ivanov A, Liu D, Nornberg MD, Sarff JS, Stupishin N, Waksman J. Majority Ion Heating by Neutral Beam Injection and Confinement of Fast Ions in the Madison Symmetric Torus Reversed Field Pinch. Fusion Science and Technology 2017. [DOI: 10.13182/fst11-a11567] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | | | | | - y Davydenko
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - P. Deichuli
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | | | | | - G. Fiksel
- University of Wisconsin, Madison WI 53706 USA;
- Laboratory for Laser Energetics, University of Rochester, Rochester NY 14610, USA
| | - A.A. Ivanov
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - D. Liu
- University of Wisconsin, Madison WI 53706 USA;
| | | | - J. S. Sarff
- University of Wisconsin, Madison WI 53706 USA;
| | - N. Stupishin
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - J. Waksman
- University of Wisconsin, Madison WI 53706 USA;
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12
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Nishizawa T, Nornberg MD, Den Hartog DJ, Sarff JS. Linearized spectrum correlation analysis for line emission measurements. Rev Sci Instrum 2017; 88:083513. [PMID: 28863643 DOI: 10.1063/1.4999450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A new spectral analysis method, Linearized Spectrum Correlation Analysis (LSCA), for charge exchange and passive ion Doppler spectroscopy is introduced to provide a means of measuring fast spectral line shape changes associated with ion-scale micro-instabilities. This analysis method is designed to resolve the fluctuations in the emission line shape from a stationary ion-scale wave. The method linearizes the fluctuations around a time-averaged line shape (e.g., Gaussian) and subdivides the spectral output channels into two sets to reduce contributions from uncorrelated fluctuations without averaging over the fast time dynamics. In principle, small fluctuations in the parameters used for a line shape model can be measured by evaluating the cross spectrum between different channel groupings to isolate a particular fluctuating quantity. High-frequency ion velocity measurements (100-200 kHz) were made by using this method. We also conducted simulations to compare LSCA with a moment analysis technique under a low photon count condition. Both experimental and synthetic measurements demonstrate the effectiveness of LSCA.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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13
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Jacobson CM, Borchardt MT, Den Hartog DJ, Falkowski AF, Morton LA, Thomas MA. Identification and mitigation of stray laser light in the Thomson scattering system on the Madison Symmetric Torus (MST). Rev Sci Instrum 2016; 87:11E511. [PMID: 27910553 DOI: 10.1063/1.4960063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Thomson scattering diagnostic on the Madison Symmetric Torus (MST) records excessive levels of stray Nd:YAG laser light. Stray light saturates the 1064 nm spectral channel in all polychromators, which prevents absolute electron density measurements via Rayleigh scattering calibration. Furthermore, stray light contaminates adjacent spectral channels for r/a ≥ 0.75, which renders the diagnostic unable to make electron temperature measurements at these radii. In situ measurements of stray light levels during a vacuum vessel vent are used to identify stray light sources and strategies for reduction of stray light levels. Numerical modeling using Zemax OpticStudio supports these measurements. The model of the vacuum vessel and diagnostic includes synthetic collection optics to enable direct comparison of measured and simulated stray light levels. Modeling produces qualitatively similar stray light distributions to MST measurements, and quantifies the mitigation effects of stray light mitigation strategies prior to implementation.
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Affiliation(s)
- C M Jacobson
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - M T Borchardt
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - A F Falkowski
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - L A Morton
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - M A Thomas
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
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14
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VanMeter PD, Franz P, Reusch LM, Sarff JS, Den Hartog DJ. A comparison between soft x-ray and magnetic phase data on the Madison symmetric torus. Rev Sci Instrum 2016; 87:11E322. [PMID: 27910686 DOI: 10.1063/1.4960492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Soft X-Ray (SXR) tomography system on the Madison Symmetric Torus uses four cameras to determine the emissivity structure of the plasma. This structure should directly correspond to the structure of the magnetic field; however, there is an apparent phase difference between the emissivity reconstructions and magnetic field reconstructions when using a cylindrical approximation. The difference between the phase of the dominant rotating helical mode of the magnetic field and the motion of the brightest line of sight for each SXR camera is dependent on both the camera viewing angle and the plasma conditions. Holding these parameters fixed, this phase difference is shown to be consistent over multiple measurements when only toroidal or poloidal magnetic field components are considered. These differences emerge from physical effects of the toroidal geometry which are not captured in the cylindrical approximation.
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Affiliation(s)
- P D VanMeter
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Franz
- Consorzio RFX, Padova, Italy
| | - L M Reusch
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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15
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Feng X, Nornberg MD, Craig D, Den Hartog DJ, Oliva SP. Spectroscopic determination of the composition of a 50 kV hydrogen diagnostic neutral beam. Rev Sci Instrum 2016; 87:11E543. [PMID: 27910452 DOI: 10.1063/1.4961269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A grating spectrometer with an electron multiplying charge-coupled device camera is used to diagnose a 50 kV, 5 A, 20 ms hydrogen diagnostic neutral beam. The ion source density is determined from Stark broadened Hβ emission and the spectrum of Doppler-shifted Hα emission is used to quantify the fraction of ions at full, half, and one-third beam energy under a variety of operating conditions including fueling gas pressure and arc discharge current. Beam current is optimized at low-density conditions in the ion source while the energy fractions are found to be steady over most operating conditions.
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Affiliation(s)
- X Feng
- Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA
| | - D Craig
- Wheaton College, Wheaton, Illinois 60187, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA
| | - S P Oliva
- Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA
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16
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Baltzer MM, Craig D, Den Hartog DJ, Nishizawa T, Nornberg MD. Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system. Rev Sci Instrum 2016; 87:11E509. [PMID: 27910359 DOI: 10.1063/1.4955491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.
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Affiliation(s)
- M M Baltzer
- Department of Physics, Wheaton College, Wheaton, Illinois 60187, USA
| | - D Craig
- Department of Physics, Wheaton College, Wheaton, Illinois 60187, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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17
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Reusch LM, Den Hartog DJ, Franz P, Goetz J, McGarry MB, Stephens HD. Calibration of a two-color soft x-ray diagnostic for electron temperature measurement. Rev Sci Instrum 2016; 87:11E332. [PMID: 27910453 DOI: 10.1063/1.4961281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The two-color soft x-ray (SXR) tomography diagnostic on the Madison Symmetric Torus is capable of making electron temperature measurements via the double-filter technique; however, there has been a 15% systematic discrepancy between the SXR double-filter (SXRDF) temperature and Thomson scattering (TS) temperature. Here we discuss calibration of the Be filters used in the SXRDF measurement using empirical measurements of the transmission function versus energy at the BESSY II electron storage ring, electron microprobe analysis of filter contaminants, and measurement of the effective density. The calibration does not account for the TS and SXRDF discrepancy, and evidence from experiments indicates that this discrepancy is due to physics missing from the SXRDF analysis rather than instrumentation effects.
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Affiliation(s)
- L M Reusch
- University of Wisconsin - Madison, Madison, Wisconsin 53703, USA
| | - D J Den Hartog
- University of Wisconsin - Madison, Madison, Wisconsin 53703, USA
| | - P Franz
- Consorzio RFX, Padova, Italy
| | - J Goetz
- University of Wisconsin - Madison, Madison, Wisconsin 53703, USA
| | - M B McGarry
- University of Wisconsin - Madison, Madison, Wisconsin 53703, USA
| | - H D Stephens
- University of Wisconsin - Madison, Madison, Wisconsin 53703, USA
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18
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Nishizawa T, Nornberg MD, Den Hartog DJ, Craig D. Upgrading a high-throughput spectrometer for high-frequency (<400 kHz) measurements. Rev Sci Instrum 2016; 87:11E530. [PMID: 27910690 DOI: 10.1063/1.4960073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. The transimpedance amplifier's cutoff frequency was increased based upon simulations comparing the change in the measured photon counts for time-dynamic signals. We modeled each signal-processing stage of the diagnostic and scanned the filtering frequency to quantify the uncertainty in the photon counting rate. This modeling showed that uncertainties can be calculated based on assuming each amplification stage is a Poisson process and by calibrating the photon counting rate with a DC light source to address additional variation.
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Affiliation(s)
- T Nishizawa
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D Craig
- Wheaton College, Wheaton, Illinois 60187, USA
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19
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Kubala SZ, Borchardt MT, Den Hartog DJ, Holly DJ, Jacobson CM, Morton LA, Young WC. Upgrades to improve the usability, reliability, and spectral range of the MST Thomson scattering diagnostic. Rev Sci Instrum 2016; 87:11E547. [PMID: 27910649 DOI: 10.1063/1.4962251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Thomson scattering diagnostic on MST records both equilibrium and fluctuating electron temperature with a range capability of 10 eV-5 keV. Standard operation with two modified commercial Nd:YAG lasers allows measurements at rates of 1 kHz-25 kHz. Several subsystems of the diagnostic are being improved. The power supplies for the avalanche photodiode detectors (APDs) that record the scattered light are being replaced to improve usability, reliability, and maintainability. Each of the 144 APDs will have an individual rack mounted switching supply, with bias voltage adjustable to match the APD. Long-wavelength filters (1140 nm center, 80 nm bandwidth) have been added to the polychromators to improve capability to resolve non-Maxwellian distributions and to enable directed electron flow measurements. A supercontinuum (SC) pulsed white light source has replaced the tungsten halogen lamp previously used for spectral calibration of the polychromators. The SC source combines substantial brightness produced in nanosecond pulses with a spectrum that covers the entire range of the polychromators.
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Affiliation(s)
- S Z Kubala
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M T Borchardt
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Holly
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - C M Jacobson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L A Morton
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W C Young
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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20
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Mirnov VV, Brower DL, Den Hartog DJ, Ding WX, Duff J, Parke E. Electron kinetic effects on interferometry, polarimetry and Thomson scattering measurements in burning plasmas (invited). Rev Sci Instrum 2014; 85:11D302. [PMID: 25430162 DOI: 10.1063/1.4891176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
At anticipated high electron temperatures in ITER, the effects of electron thermal motion on Thomson scattering (TS), toroidal interferometer/polarimeter (TIP), and poloidal polarimeter (PoPola) diagnostics will be significant and must be accurately treated. The precision of the previous lowest order linear in τ = Te/mec(2) model may be insufficient; we present a more precise model with τ(2)-order corrections to satisfy the high accuracy required for ITER TIP and PoPola diagnostics. The linear model is extended from Maxwellian to a more general class of anisotropic electron distributions that allows us to take into account distortions caused by equilibrium current, ECRH, and RF current drive effects. The classical problem of the degree of polarization of incoherent Thomson scattered radiation is solved analytically exactly without any approximations for the full range of incident polarizations, scattering angles, and electron thermal motion from non-relativistic to ultra-relativistic. The results are discussed in the context of the possible use of the polarization properties of Thomson scattered light as a method of Te measurement relevant to ITER operational scenarios.
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Affiliation(s)
- V V Mirnov
- Physics Department, University of Wisconsin - Madison and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
| | - D L Brower
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - D J Den Hartog
- Physics Department, University of Wisconsin - Madison and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
| | - W X Ding
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - J Duff
- Physics Department, University of Wisconsin - Madison and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
| | - E Parke
- Physics Department, University of Wisconsin - Madison and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
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21
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Young WC, Den Hartog DJ. Operation and beam profiling of an up to 200 kHz pulse-burst laser for Thomson scattering. Rev Sci Instrum 2014; 85:11D808. [PMID: 25430221 DOI: 10.1063/1.4885539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A new, high-repetition rate laser is in development for use on the Thomson scattering diagnostic on the Madison Symmetric Torus. The laser has been tested at a rate of 200 kHz in a pulse-burst operation, producing bursts of 5 pulses above 1.5 J each, while capable of bursts of 17 pulses at 100 kHz. A master oscillator-power amplifier architecture is used with a Nd:YVO4 oscillator, four Nd:YAG amplifiers, and a Nd:glass amplifier. A radial profile over the pulse sequence is measured by using a set of graphite apertures and an energy meter, showing a change in beam quality over a pulsing sequence.
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Affiliation(s)
- W C Young
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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22
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Reusch LM, Galante ME, Franz P, Johnson JR, McGarry MB, Stephens HD, Den Hartog DJ. An integrated data analysis tool for improving measurements on the MST RFP. Rev Sci Instrum 2014; 85:11D844. [PMID: 25430257 DOI: 10.1063/1.4886957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Many plasma diagnostics contain complementary information. For example, the double-foil soft x-ray system (SXR) and the Thomson Scattering diagnostic (TS) on the Madison Symmetric Torus both measure electron temperature. The complementary information from these diagnostics can be combined using a systematic method based on integrated data analysis techniques, leading to more accurate and sensitive results. An integrated data analysis tool based on Bayesian probability theory was able to estimate electron temperatures that are consistent with both the SXR and TS diagnostics and more precise than either. A Markov Chain Monte Carlo analysis to increase the flexibility of the tool was implemented and benchmarked against a grid search method.
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Affiliation(s)
- L M Reusch
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M E Galante
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Franz
- Consorzio RFX, EURATOM-ENEA Association, Padova, Italy
| | - J R Johnson
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M B McGarry
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - H D Stephens
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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23
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McGarry MB, Franz P, Den Hartog DJ, Goetz JA, Johnson J. Note: Effect of photodiode aluminum cathode frame on spectral sensitivity in the soft x-ray energy band. Rev Sci Instrum 2014; 85:096105. [PMID: 25273791 DOI: 10.1063/1.4894656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Silicon photodiodes used for soft x-ray detection typically have a thin metal electrode partially covering the active area of the photodiode, which subtly alters the spectral sensitivity of the photodiode. As a specific example, AXUV4BST photodiodes from International Radiation Detectors have a 1.0 μm thick aluminum frame covering 19% of the active area of the photodiode, which attenuates the measured x-ray signal below ~6 keV. This effect has a small systematic impact on the electron temperature calculated from measurements of soft x-ray bremsstrahlung emission from a high-temperature plasma. Although the systematic error introduced by the aluminum frame is only a few percent in typical experimental conditions on the Madison Symmetric Torus, it may be more significant for other instruments that use similar detectors.
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Affiliation(s)
- M B McGarry
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Franz
- Consorzio RFX, Associazione Euratom-ENEA per la Fusione, Padova, Italy
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J A Goetz
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Johnson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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24
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Ding WX, Lin L, Brower DL, Almagri AF, Chapman BE, Fiksel G, Den Hartog DJ, Sarff JS. Kinetic stress and intrinsic flow in a toroidal plasma. Phys Rev Lett 2013; 110:065008. [PMID: 23432267 DOI: 10.1103/physrevlett.110.065008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Indexed: 06/01/2023]
Abstract
A new mechanism for intrinsic plasma flow has been experimentally identified in a toroidal plasma. For reversed field pinch plasmas with a few percent β (ratio of plasma pressure to magnetic pressure), measurements show that parallel pressure fluctuations correlated with magnetic fluctuations create a kinetic stress that can affect momentum balance and the evolution of intrinsic plasma flow. This implies kinetic effects are important for flow generation and sustainment.
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Affiliation(s)
- W X Ding
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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25
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McGarry MB, Franz P, Den Hartog DJ, Goetz JA, Thomas MA, Reyfman M, Kumar STA. High-performance double-filter soft x-ray diagnostic for measurement of electron temperature structure and dynamics. Rev Sci Instrum 2012; 83:10E129. [PMID: 23126950 DOI: 10.1063/1.4740274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A new soft x-ray (SXR) T(e) and tomography diagnostic has been developed for MST that can be used for simultaneous SXR spectrum measurement, tomographically reconstructed emissivity, and reconstructed and line-of-sight electron temperature. The diagnostic utilizes high-performance differential transimpedance amplifiers (gain 10(5)-10(9)) to provide fast time response (up to 125 kHz), allowing for the study of plasma structure dynamics. SXR double-foil T(e) measurements are consistent with Thomson scattering. SXR brightness through a variety of filter thicknesses has been combined with charge exchange recombination spectroscopy (CHERS) impurity density measurements to determine the plasma energy spectrum. Magnetic pickup from the fluctuating magnetic fields in the plasma (B̃∼20 gauss at 10-20 kHz) has been dramatically reduced by improving the detector and housing design, so that nanoampere diode currents are now measured without interference from the substantial fluctuating magnetic field incident on the plasma facing surface of the probe.
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Affiliation(s)
- M B McGarry
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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26
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Parke E, Den Hartog DJ, Morton LA, Stephens HD, Kasten CP, Reusch JA, Harris WH, Borchardt MT, Falkowski AF, Hurst NC, Plunkett A, Goglio J. Improvements to the calibration of the MST Thomson scattering diagnostic. Rev Sci Instrum 2012; 83:10E324. [PMID: 23126982 DOI: 10.1063/1.4733566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Calibration of the Madison Symmetric Torus Thomson scattering system has been refined to improve temperature fluctuation measurements. Multiple avalanche photodiodes have been directly calibrated for use as reference detectors during calibration, improving accuracy and ease of use. From the absolute calibration we calculate corrections to the gain for variation in detector operating temperature. We also measure the spatial uniformity of detector responsivity for several photodiodes, and present a method of accounting for non-uniformity in the calibration process. Finally, the gain and noise enhancement are measured at multiple wavelengths to improve temperature and uncertainty measurements.
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Affiliation(s)
- E Parke
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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27
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Kumar STA, Den Hartog DJ, Caspary KJ, Magee RM, Mirnov VV, Chapman BE, Craig D, Fiksel G, Sarff JS. Classical impurity ion confinement in a toroidal magnetized fusion plasma. Phys Rev Lett 2012; 108:125006. [PMID: 22540593 DOI: 10.1103/physrevlett.108.125006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2011] [Indexed: 05/31/2023]
Abstract
High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.
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Affiliation(s)
- S T A Kumar
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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28
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Reusch JA, Anderson JK, Den Hartog DJ, Ebrahimi F, Schnack DD, Stephens HD, Forest CB. Experimental evidence for a reduction in electron thermal diffusion due to trapped particles. Phys Rev Lett 2011; 107:155002. [PMID: 22107297 DOI: 10.1103/physrevlett.107.155002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Indexed: 05/31/2023]
Abstract
New high time resolution measurements of the electron thermal diffusion χ(e) throughout the sawtooth cycle of the Madison Symmetric Torus reversed-field pinch have been made by utilizing the enhanced capabilities of the upgraded multipoint, multipulse Thomson scattering system. These measurements are compared to the χ(e) due to magnetic diffusion predicted by using information from a new high spectral resolution zero-β nonlinear resistive magnetohydrodynamic simulation performed, for the first time, at the Lundquist number of high current Madison Symmetric Torus plasmas (S≈4×10(6)). Agreement between the measured and predicted values is found only if the reduction in thermal diffusion due to trapped particles is taken into account.
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Affiliation(s)
- J A Reusch
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA.
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29
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Magee RM, Den Hartog DJ, Kumar STA, Almagri AF, Chapman BE, Fiksel G, Mirnov VV, Mezonlin ED, Titus JB. Anisotropic ion heating and tail generation during tearing mode magnetic reconnection in a high-temperature plasma. Phys Rev Lett 2011; 107:065005. [PMID: 21902334 DOI: 10.1103/physrevlett.107.065005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Indexed: 05/31/2023]
Abstract
Complementary measurements of ion energy distributions in a magnetically confined high-temperature plasma show that magnetic reconnection results in both anisotropic ion heating and the generation of suprathermal ions. The anisotropy, observed in the C(+6) impurity ions, is such that the temperature perpendicular to the magnetic field is larger than the temperature parallel to the magnetic field. The suprathermal tail appears in the majority ion distribution and is well described by a power law to energies 10 times the thermal energy. These observations may offer insight into the energization process.
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Affiliation(s)
- R M Magee
- Department of Physics, University of Wisconsin-Madison, 53706, USA.
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30
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Lizunov AA, Den Hartog DJ, Donin AS, Ivanov AA, Prikhodko VV. Note: Multi-point measurement of |B| in the gas-dynamic trap with a spectral motional Stark effect diagnostic. Rev Sci Instrum 2011; 82:086105. [PMID: 21895283 DOI: 10.1063/1.3624742] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
An upgraded spectral motional Stark effect diagnostic has been installed on the gas-dynamic trap (GDT) experiment to enable spatially resolved measurement of |B|. A new low-noise charge-coupled device detector, combined with enhancements of the diagnostic neutral beam, allows single-shot profile measurements. Previously only single-point motional Stark effect measurements were possible, and detector noise severely limited measurement precision, requiring multi-shot averaging. The plasma pressure profile in GDT is derived from the measured diamagnetic modification of |B| and used to examine the conditions of stable plasma confinement at high plasma pressure.
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Affiliation(s)
- A A Lizunov
- Budker Institute of Nuclear Physics, Novosibirsk, Russia.
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31
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Den Hartog DJ, Ambuel JR, Borchardt MT, Caspary KJ, Hartog EAD, Falkowski AF, Harris WS, Ko J, Pablant NA, Reusch JA, Robl PE, Stephens HD, Summers HP, Yang YM. Advances in Time-Resolved Measurement of Magnetic Field and Electron Temperature in Low-Magnetic-Field Plasmas. Fusion Science and Technology 2011. [DOI: 10.13182/fst11-a11589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- D. J. Den Hartog
- University of Wisconsin–Madison, Madison, WI 53706 USA
- Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas
| | - J. R. Ambuel
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | | | - K. J. Caspary
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | | | | | - W. S. Harris
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | - J. Ko
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | - N. A. Pablant
- University of California–San Diego, La Jolla, CA 92093 USA
| | - J. A. Reusch
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | - P. E. Robl
- University of Wisconsin–Madison, Madison, WI 53706 USA
| | | | | | - Y. M. Yang
- University of Wisconsin–Madison, Madison, WI 53706 USA
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32
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Golingo RP, Shumlak U, Den Hartog DJ. Note: Zeeman splitting measurements in a high-temperature plasma. Rev Sci Instrum 2010; 81:126104. [PMID: 21198059 DOI: 10.1063/1.3509400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The Zeeman effect has been used for measurement of magnetic fields in low-temperature plasma, but the diagnostic technique is difficult to implement in a high-temperature plasma. This paper describes new instrumentation and methodology for simultaneous measurement of the entire Doppler-broadened left and right circularly polarized Zeeman spectra in high-temperature plasmas. Measurements are made using spectra emitted parallel to the magnetic field by carbon impurities in high-temperature plasma. The Doppler-broadened width is much larger than the magnitude of the Zeeman splitting, thus simultaneous recording of the two circularly polarized Zeeman line profiles is key to accurate measurement of the magnetic field in the ZaP Z-pinch plasma device. Spectral data are collected along multiple chords on both sides of the symmetry axis of the plasma. This enables determination of the location of the current axis of the Z-pinch and of lower-bound estimates of the local magnetic field at specific radial locations in the plasma.
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Affiliation(s)
- R P Golingo
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington 98195-2250, USA.
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33
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McGarry MB, Franz P, Den Hartog DJ, Goetz JA. A new double-foil soft x-ray array to measure T(e) on the MST reversed field pinch. Rev Sci Instrum 2010; 81:10E516. [PMID: 21034044 DOI: 10.1063/1.3481167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A soft x-ray (SXR) diagnostic to measure electron temperature on the Madison Symmetric Torus using two complementary methods is presented. Both methods are based on the double-foil technique, which calculates electron temperature via the ratio of SXR bremsstrahlung emission from the plasma in two different energy ranges. The tomographic emissivity method applies the double-foil technique to a tomographic reconstruction of SXR emissivity, creating a two-dimensional map of temperature throughout the plasma. In contrast, the direct brightness method applies the double-foil technique directly to the measured brightness and generates vertical and horizontal radial profiles. Extensive modeling demonstrates advantages and limitations in both techniques. For example, although the emissivity technique provides a two-dimensional mapping of temperature, its reliance on multiple tomographic inversions introduces some artifacts into the results. On the other hand, the more direct brightness technique avoids these artifacts but is only able to provide a radial profile of electron temperature.
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Affiliation(s)
- M B McGarry
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Harris WS, Den Hartog DJ, Hurst NC. Initial operation of a pulse-burst laser system for high-repetition-rate Thomson scattering. Rev Sci Instrum 2010; 81:10D505. [PMID: 21033860 DOI: 10.1063/1.3466901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A pulse-burst laser has been installed for Thomson scattering measurements on the Madison Symmetric Torus reversed-field pinch. The laser design is a master-oscillator power-amplifier. The master oscillator is a commercial Nd:YVO(4) laser (1064 nm) which is capable of Q-switching at frequencies between 5 and 250 kHz. Four Nd:YAG (yttrium aluminum garnet) amplifier stages are in place to amplify the Nd:YVO(4) emission. Single pulses through the Nd:YAG amplifier stages gives energies up to 1.5 J and the gain for each stage has been measured. Repetitive pulsing at 10 kHz has also been performed for 2 ms bursts, giving average pulse energies of 0.53 J with ΔE/E of 4.6%, where ΔE is the standard deviation between pulses. The next step will be to add one of two Nd:glass (silicate) amplifier stages to produce final pulse energies of 1-2 J for bursts up to 250 kHz.
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Affiliation(s)
- W S Harris
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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35
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Magee RM, Den Hartog DJ, Fiksel G, Kumar STA, Craig D. Toroidal charge exchange recombination spectroscopy measurements on MST. Rev Sci Instrum 2010; 81:10D716. [PMID: 21033909 DOI: 10.1063/1.3478665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Charge exchange recombination spectroscopy measurements of the poloidal component of the C(+6) temperature and flow in the Madison Symmetric Torus have been vital in advancing the understanding of the ion dynamics in the reversed field pinch. Recent work has expanded the diagnostic capability to include toroidal measurements. A new toroidal view overcomes a small signal-to-background ratio (5%-15%) to make the first localized measurements of the parallel component of the impurity ion temperature in the core of the reversed field pinch. The measurement is made possible through maximal light collection in the optical design and extensive atomic modeling in the fitting routine. An absolute calibration of the system allowed the effect of Poisson noise in the signal on line fitting to be quantified. The measurement is made by stimulating emission with a recently upgraded 50 keV hydrogen diagnostic neutral beam. Radial localization is ∼4 cm(2), and good temporal resolution (100 μs) is achieved by making simultaneous emission and background measurements with a high-throughput double-grating spectrometer.
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Affiliation(s)
- R M Magee
- University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
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Ko J, Den Hartog DJ, Caspary KJ, Den Hartog EA, Pablant NA, Summers HP. Two-point motional Stark effect diagnostic for Madison Symmetric Torus. Rev Sci Instrum 2010; 81:10D702. [PMID: 21033895 DOI: 10.1063/1.3461995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A high-precision spectral motional Stark effect (MSE) diagnostic provides internal magnetic field measurements for Madison Symmetric Torus (MST) plasmas. Currently, MST uses two spatial views--on the magnetic axis and on the midminor (off-axis) radius, the latter added recently. A new analysis scheme has been developed to infer both the pitch angle and the magnitude of the magnetic field from MSE spectra. Systematic errors are reduced by using atomic data from atomic data and analysis structure in the fit. Reconstructed current density and safety factor profiles are more strongly and globally constrained with the addition of the off-axis radius measurement than with the on-axis one only.
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Affiliation(s)
- J Ko
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Den Hartog DJ, Ambuel JR, Borchardt MT, Falkowski AF, Harris WS, Holly DJ, Parke E, Reusch JA, Robl PE, Stephens HD, Yang YM. Pulse-burst laser systems for fast Thomson scattering (invited). Rev Sci Instrum 2010; 81:10D513. [PMID: 21033868 DOI: 10.1063/1.3475723] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to "pulse-burst" capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.
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Affiliation(s)
- D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA.
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Ding WX, Brower DL, Fiksel G, Den Hartog DJ, Prager SC, Sarff JS. Magnetic-fluctuation-induced particle transport and density relaxation in a high-temperature plasma. Phys Rev Lett 2009; 103:025001. [PMID: 19659214 DOI: 10.1103/physrevlett.103.025001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Indexed: 05/28/2023]
Abstract
The first direct measurement of magnetic-fluctuation-induced particle flux in the core of a high-temperature plasma is reported. Transport occurs due to magnetic field fluctuations associated with global tearing instabilities. The electron particle flux, resulting from the correlated product of electron density and radial magnetic fluctuations, accounts for density profile relaxation during a magnetic reconnection event. The measured particle transport is much larger than that expected for ambipolar particle diffusion in a stochastic magnetic field.
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Affiliation(s)
- W X Ding
- Department of Physics, University of California Los Angeles, Los Angeles, California 90095, USA
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Reusch JA, Borchardt MT, Den Hartog DJ, Falkowski AF, Holly DJ, O'Connell R, Stephens HD. Multipoint Thomson scattering diagnostic for the Madison Symmetric Torus reversed-field pinch. Rev Sci Instrum 2008; 79:10E733. [PMID: 19044549 DOI: 10.1063/1.2956742] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The multipoint Thomson scattering diagnostic on the Madison Symmetric Torus (MST) is now fully operational with 21 spatial points, which cover the entire minor radius. Four full electron temperature profiles can be obtained during each MST discharge, with a variable delay between each profile. This system overcomes challenges that arise from the unique machine design, location, and plasma characteristics of MST. The machine design limits the maximum porthole diameter to 11.4 cm, requiring a compact, re-entrant, seven element lens for scattered light collection. Limited space near MST necessitates a long beam path for the two Nd:YAG lasers requiring a remote beam line adjustment system to suppress drift in the beam position due to thermal expansion of the building. Due to the remote location of the laser head, substantial design effort was put into the creation of a set of safety interlocks for the laser system. The dynamic nature of MST plasmas and the wide range of operating space require a versatile scattered light detection system consisting of filter polychromators with temperature controlled avalanche photodiode detectors. We also implement an insertable integrating sphere, which travels along the laser beam path through the vacuum vessel, for the alignment of both the fiber optics and the lasers.
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Affiliation(s)
- J A Reusch
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA.
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O'Connell R, Den Hartog DJ, Borchardt MT, Holly DJ, Reusch JA, Stephens HD. Optimizing a Thomson scattering diagnostic for fast dynamics and high background. Rev Sci Instrum 2008; 79:10E735. [PMID: 19044551 DOI: 10.1063/1.2957844] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The Madison Symmetric Torus (MST) presents challenging conditions for Thomson scattering (TS) measurements. The MST plasmas are reversed-field pinches (RFPs) with electron density n(e)<3x10(13) cm(-3), typically 1x10(13) cm(-3). The TS system was designed to measure from 10 eV to 2 keV; however, six polychromators were upgraded from four to eight spectral channels to resolve to 10 keV. There is no diverter or vertical field, so wall interaction results in high background light both from ion and neutral bremsstrahlungs and from line radiation. Also during standard plasmas, the RFP exhibits regular reconnection sawteeth events during which the plasma current, density, and temperature profiles are flattened. These events are of interest both due to the reconnection physics and to their contribution to the MST equilibrium and confinement. These events occur over 100 microS and exhibit large changes in background light and fast changes in temperature. During improved confinement plasmas, there are no sawteeth; the background is low but the temperature can be over an order of magnitude higher. Data analysis of the system has been developed to accommodate both the large dynamic range of the temperature, the fast dynamics, and the fast changing, high amplitude background. Special attention has been paid to the sources of error, in particular, the contribution of the background. A response-function method reduces the measured uncertainty by a factor of 2. Numerical techniques have been developed which are extremely robust. Two methods are used, a conventional chi(2) minimization using a Levenberg-Marquardt algorithm coupled with Monte Carlo modeling for the error bar and a Bayesian statistics method. The Bayesian method computes the probability distribution for the measured photons and electron temperature and this information can be used to ensemble data and will allow future integrated data analysis efforts.
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Affiliation(s)
- R O'Connell
- University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
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Stephens HD, Borchardt MT, Den Hartog DJ, Falkowski AF, Holly DJ, O'Connell R, Reusch JA. Calibration of a Thomson scattering diagnostic for fluctuation measurements. Rev Sci Instrum 2008; 79:10E734. [PMID: 19044550 DOI: 10.1063/1.2964229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Detailed calibrations of the Madison Symmetric Torus polychromator Thomson scattering system have been made suitable for electron temperature fluctuation measurements. All calibrations have taken place focusing on accuracy, ease of use and repeatability, and in situ measurements wherever possible. Novel calibration processes have been made possible with an insertable integrating sphere (ISIS), using an avalanche photodiode (APD) as a reference detector and optical parametric oscillator (OPO). Discussed are a novel in situ spatial calibration with the use of the ISIS, the use of an APD as a reference detector to streamline the APD calibration process, a standard dc spectral calibration, and in situ pulsed spectral calibration made possible with a combination of an OPO as a light source, the ISIS, and an APD used as a reference detector. In addition a relative quantum efficiency curve for the APDs is obtained to aid in uncertainty analysis.
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Affiliation(s)
- H D Stephens
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Den Hartog DJ, Jiang N, Lempert WR. A pulse-burst laser system for a high-repetition-rate Thomson scattering diagnostic. Rev Sci Instrum 2008; 79:10E736. [PMID: 19044552 DOI: 10.1063/1.2965733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A "pulse-burst" laser system is being constructed for addition to the Thomson scattering diagnostic on the Madison Symmetric Torus (MST) reversed-field pinch. This laser is designed to produce a burst of up to 200 approximately 1 J Q-switched pulses at repetition frequencies 5-250 kHz. This laser system will operate at 1064 nm and is a master oscillator, power amplifier. The master oscillator is a compact diode-pumped Nd:YVO(4) laser, intermediate amplifier stages are flashlamp-pumped Nd:YAG, and final stages will be flashlamp-pumped Nd:glass (silicate). Variable pulse width drive (0.3-20 ms) of the flashlamps is accomplished by insulated-gate bipolar transistor switching of large electrolytic capacitor banks. The burst train of laser pulses will enable the study of electron temperature (T(e)) and electron density (n(e)) dynamics in a single MST shot, and with ensembling, will enable correlation of T(e) and n(e) fluctuations with other fluctuating quantities.
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Affiliation(s)
- D J Den Hartog
- Department of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Gangadhara S, Craig D, Ennis DA, Hartog DJD, Fiksel G, Prager SC. Spatially resolved measurements of ion heating during impulsive reconnection in the Madison Symmetric Torus. Phys Rev Lett 2007; 98:075001. [PMID: 17359029 DOI: 10.1103/physrevlett.98.075001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Indexed: 05/14/2023]
Abstract
The impurity ion temperature evolution has been measured during three types of impulsive reconnection events in the Madison Symmetric Torus reversed field pinch. During an edge reconnection event, the drop in stored magnetic energy is small and ion heating is observed to be limited to the outer half of the plasma. Conversely, during a global reconnection event the drop in stored magnetic energy is large, and significant heating is observed at all radii. For both kinds of events, the drop in magnetic energy is sufficient to explain the increase in ion thermal energy. However, not all types of reconnection lead to ion heating. During a core reconnection event, both the stored magnetic energy and impurity ion temperature remain constant. The results suggest that a drop in magnetic energy is required for ions to be heated during reconnection, and that when this occurs heating is localized near the reconnection layer.
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Affiliation(s)
- S Gangadhara
- University of Wisconsin, Madison, Wisconsin and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
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Craig D, Den Hartog DJ, Ennis DA, Gangadhara S, Holly D. High throughput spectrometer for fast localized Doppler measurements. Rev Sci Instrum 2007; 78:013103. [PMID: 17503903 DOI: 10.1063/1.2424450] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
A new custom-built duo spectrometer has been commissioned for fast localized Doppler measurements of plasma ions in the Madison Symmetric Torus. The instrument combines very high optical throughput (transmission efficiency of 6% and etendue of 0.80 mm(2) sr divided into two simultaneous measurements) with good resolution (lambda/Deltalambda=5600). The design is a double grating variant of the Czerny-Turner layout and has been carefully optimized for fast (100 kHz) measurements of the C VI line at 343.4 nm. The instrument is currently being applied for high speed charge exchange recombination spectroscopy measurements.
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Affiliation(s)
- D Craig
- The Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, 1150 University Avenue, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Fiksel G, Hudson B, Den Hartog DJ, Magee RM, O'Connell R, Prager SC, Beklemishev AD, Davydenko VI, Ivanov AA, Tsidulko YA. Observation of weak impact of a stochastic magnetic field on fast-ion confinement. Phys Rev Lett 2005; 95:125001. [PMID: 16197080 DOI: 10.1103/physrevlett.95.125001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Indexed: 05/04/2023]
Abstract
Fast ions are observed to be very well confined in the Madison Symmetric Torus reversed field pinch despite the presence of stochastic magnetic field. The fast-ion energy loss is consistent with the classical slowing down rate, and their confinement time is longer than expected by stochastic estimates. Fast-ion confinement is measured from the decay of d-d neutrons following a short pulse of a 20 keV atomic deuterium beam. Ion confinement agrees with computation of particle trajectories in the stochastic magnetic field, and is understood through consideration of ion guiding center islands.
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Affiliation(s)
- G Fiksel
- Department of Physics, University of Wisconsin--Madison and Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA
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Abdrachitov G, Bagryansky P, Den Hartog DJ, Ivanov A, Korepanov S, Lizunov A, Fiksel G, Khilchenko D. Motional Stark Effect Diagnostic for Multi-Chord Measurements of Plasma Beta in GDT. Fusion Science and Technology 2005. [DOI: 10.13182/fst05-a629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- G.F. Abdrachitov
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - P.A. Bagryansky
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - D. J. Den Hartog
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - A.A. Ivanov
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - S.A. Korepanov
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - A.A. Lizunov
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - G. Fiksel
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
| | - D.A. Khilchenko
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia, e-mail:
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Hartog DJD, Golingo RP, Jackson SL, Nelson BA, Shumlak U. The ZaP Flow Z-Pinch: Plasma Flow Shear and Stability. Fusion Science and Technology 2005. [DOI: 10.13182/fst05-a624] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- D. J. Den Hartog
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, U.S.A.
| | - R. P. Golingo
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, U.S.A.
| | - S. L. Jackson
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, U.S.A.
| | - B. A. Nelson
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, U.S.A.
| | - U. Shumlak
- Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, U.S.A.
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48
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O'Connell R, Den Hartog DJ, Forest CB, Anderson JK, Biewer TM, Chapman BE, Craig D, Fiksel G, Prager SC, Sarff JS, Terry SD, Harvey RW. Observation of velocity-independent electron transport in the reversed field pinch. Phys Rev Lett 2003; 91:045002. [PMID: 12906668 DOI: 10.1103/physrevlett.91.045002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2002] [Indexed: 05/24/2023]
Abstract
Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas in the Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have been used to determine the velocity dependence of the electron diffusion coefficient, utilizing computational solutions of the Fokker-Planck transport equation. With improved-confinement, the fast electron diffusivity drops by 2 orders of magnitude and is independent of velocity. This suggests a change in the transport mechanism away from stochastic magnetic field diffusion.
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Affiliation(s)
- R O'Connell
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Ivanov AA, Anikeev AV, Bagryansky PA, Deichuli PP, Korepanov SA, Lizunov AA, Maximov VV, Murakhtin SV, Savkin VY, Den Hartog DJ, Fiksel G, Noack K. Experimental evidence of high-beta plasma confinement in an axially symmetric gas dynamic trap. Phys Rev Lett 2003; 90:105002. [PMID: 12689003 DOI: 10.1103/physrevlett.90.105002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2002] [Indexed: 05/24/2023]
Abstract
In the axially symmetric magnetic mirror device gas dynamic trap (GDT), on-axis transverse beta (ratio of the transverse plasma pressure to magnetic field pressure) exceeding 0.4 in the fast ion turning points has been first achieved. The plasma has been heated by injection of neutral beams, which at the same time produced anisotropic fast ions. Neither enhanced losses of the plasma nor anomalies in the fast ion scattering and slowing down were observed. This observation confirms predicted magnetohydrodynamic stability of plasma in the axially symmetric mirror devices with average min-B, like the GDT is. The measured beta value is rather close to that expected in different versions of the GDT based 14 MeV neutron source for fusion materials testing.
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Affiliation(s)
- A A Ivanov
- Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia.
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Chapman BE, Anderson JK, Biewer TM, Brower DL, Castillo S, Chattopadhyay PK, Chiang CS, Craig D, Den Hartog DJ, Fiksel G, Fontana PW, Forest CB, Gerhardt S, Hansen AK, Holly D, Jiang Y, Lanier NE, Prager SC, Reardon JC, Sarff JS. Reduced edge instability and improved confinement in the MST reversed-field pinch. Phys Rev Lett 2001; 87:205001. [PMID: 11690477 DOI: 10.1103/physrevlett.87.205001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2001] [Indexed: 05/23/2023]
Abstract
Improved confinement has been achieved in the MST through control of the poloidal electric field, but it is now known that the improvement has been limited by bursts of an edge-resonant instability. Through refined poloidal electric field control, plus control of the toroidal electric field, we have suppressed these bursts. This has led to a total beta of 15% and a reversed-field-pinch-record estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exceeds the confinement scaling that has characterized most reversed-field-pinch plasmas.
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Affiliation(s)
- B E Chapman
- University of Wisconsin, Madison, Wisconsin 53706, USA.
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