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Laggner FM, Bortolon A, Rosenthal AM, Wilks TM, Hughes JW, Freeman C, Golfinopoulos T, Nagy A, Mauzey D, Shafer MW. Absolute calibration of the Lyman-α measurement apparatus at DIII-D. Rev Sci Instrum 2021; 92:033522. [PMID: 33820112 DOI: 10.1063/5.0038134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 01/13/2021] [Indexed: 06/12/2023]
Abstract
The LLAMA (Lyman-Alpha Measurement Apparatus) diagnostic was recently installed on the DIII-D tokamak [Rosenthal et al., Rev. Sci. Instrum. (submitted) (2020)]. LLAMA is a pinhole camera system with a narrow band Bragg mirror, a bandpass interference filter, and an absolute extreme ultraviolet photodiode detector array, which measures the Ly-α brightness in the toroidal direction on the inboard, high field side (HFS) and outboard, low field side (LFS). This contribution presents a setup and a procedure for an absolute calibration near the Ly-α line at 121.6 nm. The LLAMA in-vacuum components are designed as a compact, transferable setup that can be mounted in an ex situ vacuum enclosure that is equipped with an absolutely calibrated Ly-α source. The spectral purity and stability of the Ly-α source are characterized using a vacuum ultraviolet spectrometer, while the Ly-α source brightness is measured by a NIST-calibrated photodiode. The non-uniform nature of the Ly-α source emission was overcome by performing a calibration procedure that scans the Ly-α source position and employs a numerical optimization to determine the emission pattern. Nominal and measured calibration factors are determined and compared, showing agreement within their uncertainties. A first conversion of the measured signal obtained from DIII-D indicates that the Ly-α brightness on the HFS and LFS is on the order of 1020 Ph sr-1 m-2 s-1. The established calibration setup and procedure will be regularly used to re-calibrate the LLAMA during DIII-D vents to monitor possible degradation of optical components and detectors.
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Affiliation(s)
- F M Laggner
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - A Bortolon
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - A M Rosenthal
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - T M Wilks
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - J W Hughes
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - C Freeman
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - T Golfinopoulos
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - A Nagy
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - D Mauzey
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - M W Shafer
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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2
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Wang L, Wang HQ, Ding S, Garofalo AM, Gong XZ, Eldon D, Guo HY, Leonard AW, Hyatt AW, Qian JP, Weisberg DB, McClenaghan J, Fenstermacher ME, Lasnier CJ, Watkins JG, Shafer MW, Xu GS, Huang J, Ren QL, Buttery RJ, Humphreys DA, Thomas DM, Zhang B, Liu JB. Integration of full divertor detachment with improved core confinement for tokamak fusion plasmas. Nat Commun 2021; 12:1365. [PMID: 33649306 PMCID: PMC7921092 DOI: 10.1038/s41467-021-21645-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 01/29/2021] [Indexed: 11/24/2022] Open
Abstract
Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation of fusion reactors. Here, we demonstrate the excellent compatibility of actively controlled full divertor detachment with a high-performance (βN ~ 3, H98 ~ 1.5) core plasma, using high-βp (poloidal beta, βp > 2) scenario characterized by a sustained core internal transport barrier (ITB) and a modest edge transport barrier (ETB) in DIII-D tokamak. The high-βp high-confinement scenario facilitates divertor detachment which, in turn, promotes the development of an even stronger ITB at large radius with a weaker ETB. This self-organized synergy between ITB and ETB, leads to a net gain in energy confinement, in contrast to the net confinement loss caused by divertor detachment in standard H-modes. These results show the potential of integrating excellent core plasma performance with an efficient divertor solution, an essential step towards steady-state operation of reactor-grade plasmas.
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Affiliation(s)
- L Wang
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | - H Q Wang
- General Atomics, San Diego, CA, USA.
| | - S Ding
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
- Oak Ridge Associated Universities, Oak Ridge, TN, USA
| | | | - X Z Gong
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | - D Eldon
- General Atomics, San Diego, CA, USA
| | - H Y Guo
- General Atomics, San Diego, CA, USA
| | | | | | - J P Qian
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | | | | | | | - C J Lasnier
- Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - J G Watkins
- Sandia National Laboratories, Livermore, CA, USA
| | - M W Shafer
- Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - G S Xu
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | - J Huang
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | - Q L Ren
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | | | | | | | - B Zhang
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
| | - J B Liu
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
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Wilcox RS, Shafer MW, Ferraro NM, McKee GR, Zeng L, Rhodes TL, Canik JM, Paz-Soldan C, Nazikian R, Unterberg EA. Evidence of Toroidally Localized Turbulence with Applied 3D Fields in the DIII-D Tokamak. Phys Rev Lett 2016; 117:135001. [PMID: 27715095 DOI: 10.1103/physrevlett.117.135001] [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: 04/12/2016] [Indexed: 06/06/2023]
Abstract
New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines. This modeling agrees qualitatively with the measurements. The observed gradient and fluctuation asymmetries are proposed as a mechanism by which global profile gradients in the pedestal could be relaxed due to a local change in the 3D equilibrium. These processes may play an important role in pedestal and scrape-off layer transport in ITER and other future tokamak devices with small applied 3D fields.
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Affiliation(s)
- R S Wilcox
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, USA
| | - M W Shafer
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, USA
| | - N M Ferraro
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 05764, USA
| | - G R McKee
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L Zeng
- University of California Los Angeles, Los Angeles, California 90095, USA
| | - T L Rhodes
- University of California Los Angeles, Los Angeles, California 90095, USA
| | - J M Canik
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, USA
| | - C Paz-Soldan
- General Atomics, San Diego, California 92121, USA
| | - R Nazikian
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 05764, USA
| | - E A Unterberg
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, USA
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4
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Nazikian R, Paz-Soldan C, Callen JD, deGrassie JS, Eldon D, Evans TE, Ferraro NM, Grierson BA, Groebner RJ, Haskey SR, Hegna CC, King JD, Logan NC, McKee GR, Moyer RA, Okabayashi M, Orlov DM, Osborne TH, Park JK, Rhodes TL, Shafer MW, Snyder PB, Solomon WM, Strait EJ, Wade MR. Pedestal bifurcation and resonant field penetration at the threshold of edge-localized mode suppression in the DIII-D Tokamak. Phys Rev Lett 2015; 114:105002. [PMID: 25815938 DOI: 10.1103/physrevlett.114.105002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Indexed: 06/04/2023]
Abstract
Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge-localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal that reduces the perpendicular electron flow there to near zero. These events occur simultaneously with an increase in the inner-wall magnetic response. These observations are consistent with strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearinglike structures as the plasma transitions out of ELM suppression.
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Affiliation(s)
- R Nazikian
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - C Paz-Soldan
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - J D Callen
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - J S deGrassie
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - D Eldon
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - T E Evans
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - N M Ferraro
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - B A Grierson
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - R J Groebner
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - S R Haskey
- Plasma Research Laboratory, Australian National University, Canberra, ACT 0200, Australia
| | - C C Hegna
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - J D King
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - N C Logan
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - G R McKee
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - R A Moyer
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - M Okabayashi
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - D M Orlov
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - T H Osborne
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - J-K Park
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - T L Rhodes
- University of California, Los Angeles, Los Angeles, California 90095, USA
| | - M W Shafer
- Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, Tennessee 37831, USA
| | - P B Snyder
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - W M Solomon
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - E J Strait
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - M R Wade
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
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5
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Paz-Soldan C, Nazikian R, Haskey SR, Logan NC, Strait EJ, Ferraro NM, Hanson JM, King JD, Lanctot MJ, Moyer RA, Okabayashi M, Park JK, Shafer MW, Tobias BJ. Observation of a multimode plasma response and its relationship to density pumpout and edge-localized mode suppression. Phys Rev Lett 2015; 114:105001. [PMID: 25815937 DOI: 10.1103/physrevlett.114.105001] [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: 10/15/2014] [Indexed: 06/04/2023]
Abstract
Density pumpout and edge-localized mode (ELM) suppression by applied n=2 magnetic fields in low-collisionality DIII-D plasmas are shown to be correlated with the magnitude of the plasma response driven on the high-field side (HFS) of the magnetic axis but not the low-field side (LFS) midplane. These distinct responses are a direct measurement of a multimodal magnetic plasma response, with each structure preferentially excited by a different n=2 applied spectrum and preferentially detected on the LFS or HFS. Ideal and resistive magneto-hydrodynamic (MHD) calculations find that the LFS measurement is primarily sensitive to the excitation of stable kink modes, while the HFS measurement is primarily sensitive to resonant currents (whether fully shielding or partially penetrated). The resonant currents are themselves strongly modified by kink excitation, with the optimal applied field pitch for pumpout and ELM suppression significantly differing from equilibrium field alignment.
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Affiliation(s)
- C Paz-Soldan
- General Atomics, San Diego, California 92121, USA
| | - R Nazikian
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - S R Haskey
- Plasma Research Laboratory, Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - N C Logan
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - E J Strait
- General Atomics, San Diego, California 92121, USA
| | - N M Ferraro
- General Atomics, San Diego, California 92121, USA
| | - J M Hanson
- Columbia University, New York, New York 10027, USA
| | - J D King
- General Atomics, San Diego, California 92121, USA
| | - M J Lanctot
- General Atomics, San Diego, California 92121, USA
| | - R A Moyer
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - M Okabayashi
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - J-K Park
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - M W Shafer
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6169, USA
| | - B J Tobias
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
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6
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Abstract
ABSTRACTSilica gels were prepared by two methods; from the alkoxides under conditions where moderate degrees of crosslinking are expected and from LUDOX - alkaline silicate sols from which the alkali was subsequently removed. By selective thermal treatment from 300 to 850°C, pore diameters (excluding micropores) in the range 35Å to 400Å are seen. The pore size increased with temperature while the surface area and total porosity remained essentially constant. Extensive high resolution TEM analyses showed both colloid and polymeric structures with particle sizes between 60Å and 250Å which decreased on heating. An intra particle structure, presumably micropores of 10Å to 30Å is also seen. By using a shadow cast Pt-C replica technique, stereoimages show the particles to have a filamentry type structure.
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Abstract
The formation and characterization of thin ceramic coatings is currently an active area in materials science. Specifically, there has been increased interest in these materials as dielectric and optical layers for advanced microelectronic circuitry [1]. This is in addition to their continued use and evaluation as protective coatings in a variety of applications [2]. One method of forming these coatings is via the sol-gel technique. However, only a few papers have been published in this area [3–7]. Dense silicon dioxide, aluminium oxide and various glass compositions have been deposited in thin film form on various substrates. Further, silicon dioxide films, formed by the sol-gel method, have been nitrided in ammonia at high temperatures and partially converted to an oxynitride [8–11]. These films were shown to be highly non-homogeneous, with a predominance of nitrogen at the surface. Despite the desirability of dense uniform well bonded coatings of the nitrided ceramics, i.e. Si3N4 and the oxynitrides, no method yet exists for the formation of nitrides by the sol-gel method.
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McKee GR, Fonck RJ, Shafer MW, Uzun-Kaymak IU, Yan Z. Wide-field turbulence imaging with beam emission spectroscopy. Rev Sci Instrum 2010; 81:10D741. [PMID: 21033932 DOI: 10.1063/1.3495788] [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: 05/30/2023]
Abstract
Imaging of the size, shape, time-averaged, and time-resolved dynamics of long-wavelength density turbulence structures is accomplished with an expanded, high-sensitivity, wide-field beam emission spectroscopy (BES) diagnostic on DIII-D. A 64-channel BES system is configured with an 8×8 grid of discrete channels that image an approximately 7×9 cm region at the outboard midplane. The grid covers multiple correlation lengths and each channel shape matches the measured radial-poloidal correlation length asymmetry of turbulent eddies. The wide field 8×8 imaging capability allows for sampling of essentially the full two-dimensional spatial correlation function for typical plasma conditions. The sampled area can be radially scanned over 0.4<r/a<1, including the core (ñ/n<1%), pedestal, and scrape-off-layer. The resulting time-resolved visualizations of turbulence and flows provide critical data on turbulence dynamics.
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Affiliation(s)
- G R McKee
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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9
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Shafer MW, Battaglia DJ, Unterberg EA, Evans TE, Hillis DL, Maingi R. 2D soft x-ray system on DIII-D for imaging the magnetic topology in the pedestal region. Rev Sci Instrum 2010; 81:10E534. [PMID: 21034061 DOI: 10.1063/1.3481166] [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
A new tangential two-dimensional soft x-ray imaging system (SXRIS) is being designed to examine the edge island structure in the lower X-point region of DIII-D. Plasma shielding and/or amplification of the calculated vacuum islands may play a role in the suppression of edge-localized modes via resonant magnetic perturbations (RMPs). The SXRIS is intended to improve the understanding of three-dimensional (3D) phenomena associated with RMPs. This system utilizes a tangential view with a pinhole imaging system and spectral filtering with beryllium foils. SXR emission is chosen to avoid line radiation and allows suitable signal at the top of a H-mode pedestal where T(e)∼1-2 keV. A synthetic diagnostic calculation based on 3D SXR emissivity estimates is used to help assess signal levels and resolution of the design. A signal-to-noise ratio of 10 at 1 cm resolution is expected for the perturbed signals, which are sufficient to resolve most of the predicted vacuum island sizes.
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Affiliation(s)
- M W Shafer
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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10
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Battaglia DJ, Shafer MW, Unterberg EA, Bell RE, Hillis DL, LeBlanc BP, Maingi R, Sabbagh S, Stratton BC. Simulation of a tangential soft x-ray imaging system. Rev Sci Instrum 2010; 81:10E533. [PMID: 21034060 DOI: 10.1063/1.3478883] [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
Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucidate the static edge magnetic structure during the application of 3D perturbations. To support the design of the proposed diagnostics, a synthetic diagnostic model was developed using the CHIANTI database to estimate the SXR emission. The model is shown to be in good agreement with the measurements from an existing tangential SXR camera diagnostic on NSTX.
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Affiliation(s)
- D J Battaglia
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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11
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Shafer MW, McKee GR, Austin ME, Burrell KH, Fonck RJ, Schlossberg DJ. Localized turbulence suppression and increased flow shear near the q=2 surface during internal-transport-barrier formation. Phys Rev Lett 2009; 103:075004. [PMID: 19792652 DOI: 10.1103/physrevlett.103.075004] [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: 01/28/2009] [Indexed: 05/28/2023]
Abstract
Broadband turbulent fluctuations in the plasma density are transiently suppressed when low-order rational q surfaces first appear in negative central magnetic shear plasmas on the DIII-D tokamak, which can lead to the formation of internal transport barriers. Increased localized flow shear is simultaneously observed. It transiently exceeds the measured turbulence decorrelation rate, providing a mechanism to trigger the formation of the transport barrier. This increased flow shear and turbulence suppression propagates radially outward, following the q=2 surface.
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Affiliation(s)
- M W Shafer
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin, 53706, USA
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12
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White AE, Schmitz L, Peebles WA, Carter TA, Rhodes TL, Doyle EJ, Gourdain PA, Hillesheim JC, Wang G, Holland C, Tynan GR, Austin ME, McKee GR, Shafer MW, Burrell KH, Candy J, DeBoo JC, Prater R, Staebler GM, Waltz RE, Makowski MA. A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations. Rev Sci Instrum 2008; 79:103505. [PMID: 19044712 DOI: 10.1063/1.2981186] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [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 correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices. For the first time, the radial profiles of electron temperature and density fluctuations are compared to nonlinear gyrokinetic simulations. The CECE diagnostic at DIII-D uses correlation radiometry to measure the rms amplitude and spectrum of the electron temperature fluctuations. Gaussian optics are used to produce a poloidal spot size with w(o) approximately 1.75 cm in the plasma. The intermediate frequency filters and the natural linewidth of the EC emission determine the radial resolution of the CECE diagnostic, which can be less than 1 cm. Wavenumbers resolved by the CECE diagnostic are k(theta) < or = 1.8 cm(-1) and k(r) < or = 4 cm(-1), relevant for studies of long-wavelength turbulence associated with the trapped electron mode and the ion temperature gradient mode. In neutral beam heated L-mode plasmas, core electron temperature fluctuations in the region 0.5 < r/a < 0.9, increase with radius from approximately 0.5% to approximately 2%, similar to density fluctuations that are measured simultaneously with beam emission spectroscopy. After incorporating "synthetic diagnostics" to effectively filter the code output, the simulations reproduce the characteristics of the turbulence and transport at one radial location r/a = 0.5, but not at a second location, r/a = 0.75. These results illustrate that measurements of the profiles of multiple fluctuating fields can provide a significant constraint on the turbulence models employed by the code.
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Affiliation(s)
- A E White
- University of California-Los Angeles, Los Angeles, California 90095, USA
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13
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McKee GR, Schlossberg DJ, Shafer MW. Ultrafast ion temperature and toroidal velocity fluctuation spectroscopy diagnostic design. Rev Sci Instrum 2008; 79:10F528. [PMID: 19044671 DOI: 10.1063/1.2974808] [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
High sensitivity measurements of localized, long-wavelength ion temperature, and toroidal velocity fluctuations (T(i)/T(i),v(parallel)/v(parallel)) are required to address critical issues pertaining to turbulent transport. This diagnostic design exploits emission from charge exchange recombination between neutral beam atoms and the intrinsic carbon impurity. The n=8-7 transition of C VI at lambda(0)=529.05 nm will be measured. The key difference between this diagnostic design and conventional charge exchange spectrometers is the use of high-efficiency prism-coupled transmission gratings, avalanche photodiode detectors, and high-throughput collection optics. The spectrometer achieves a spectral resolution of 0.25 nm, and observes 528.0-530.0 nm with eight discrete spectral channels, with an entrance throughput of 1.6 mm(2) sr, two orders of magnitude larger than conventional charge exchange system. The diagnostic will achieve a turbulence-relevant time resolution of 1 micros. System modeling demonstrates a sensitivity of T(i)/T(i) < or = 1%.
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Affiliation(s)
- G R McKee
- University of Wisconsin-Madison, 1500 Engineering Dr., Madison, Wisconsin 53706, USA.
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14
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Shafer MW, McKee GR, Schlossberg DJ. Singular value decomposition filtering for enhanced signal extraction from two-dimensional beam emission spectroscopy measurements. Rev Sci Instrum 2008; 79:10F534. [PMID: 19044676 DOI: 10.1063/1.2979879] [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: 05/27/2023]
Abstract
The signal-to-noise ratio (SNR) of extracted turbulence features from beam emission spectroscopy (BES) data is significantly enhanced via application of singular value decomposition (SVD) methods. BES measures two-dimensional localized density fluctuations in DIII-D. The SNR of core turbulence characteristics is typically limited by noise arising from electronic noise, photon noise, and fluctuations in the observed neutral beam. SVD filtering has led to a significant enhancement in the SNR, reducing errors in time-resolved measurements of core turbulence characteristics, including correlation lengths, decorrelation rates, and group velocities. The SVD filtration technique is applied to BES data by combining multiple physically adjacent sampling locations to extract spatially correlated signals while partially removing unwanted incoherent noise. Using approximately half of the singular value weighted modes to reconstruct turbulence signals is found to improve SNR by up to a factor of 4, while maintaining the spatial structure of the turbulence. Unique aspects of application of SVD to broadband turbulence data are discussed.
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Affiliation(s)
- M W Shafer
- University of Wisconsin, Madison, Wisconsin 1500 Engineering Dr., Madison, Wisconsin 53706, USA
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Holland C, Candy J, Waltz RE, White AE, McKee GR, Shafer MW, Schmitz L, Tynan GR. Validating simulations of core tokamak turbulence: current status and future directions. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/125/1/012043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Gupta DK, Fonck RJ, McKee GR, Schlossberg DJ, Shafer MW. Detection of zero-mean-frequency zonal flows in the core of a high-temperature tokamak plasma. Phys Rev Lett 2006; 97:125002. [PMID: 17025976 DOI: 10.1103/physrevlett.97.125002] [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] [Received: 03/24/2006] [Indexed: 05/12/2023]
Abstract
A low-frequency, spectrally broad (Deltaf approximately 10 kHz) poloidal flow structure that peaks near zero frequency is observed in time-resolved measurements of the turbulence velocity field in the core region (r/a approximately 0.6-0.9) of DIII-D tokamak plasmas. These flows exhibit a long poloidal wavelength (low m) and a short radial coherence length comparable to the ambient turbulence decorrelation length. Characteristics of these observed poloidal flows are consistent with the theoretically predicted residual or zero-mean-frequency zonal flows.
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Affiliation(s)
- D K Gupta
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA
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Drube W, Himpsel FJ, Chandrashekhar GV, Shafer MW. Empty states near the Fermi level in Bi2Sr2CaCu2O8. Phys Rev B Condens Matter 1989; 39:7328-7331. [PMID: 9947401 DOI: 10.1103/physrevb.39.7328] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Burns G, Strobel P, Chandrashekhar GV, Dacol FH, Holtzberg F, Shafer MW. Raman-active phonons in the high-temperature superconductors and results in Bi2Sr2CuO6. Phys Rev B Condens Matter 1989; 39:2245-2250. [PMID: 9948460 DOI: 10.1103/physrevb.39.2245] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Collins RT, Schlesinger Z, Chandrashekhar GV, Shafer MW. Infrared study of anisotropy in single-crystal La2-xSrxCuO4. Phys Rev B Condens Matter 1989; 39:2251-2254. [PMID: 9948461 DOI: 10.1103/physrevb.39.2251] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Shafer MW, Penney T, Olson BL, Greene RL, Koch RH. Hole concentrations, Hall number, and Tc relationships in substituted YBa2Cu3Oy. Phys Rev B Condens Matter 1989; 39:2914-2917. [PMID: 9948577 DOI: 10.1103/physrevb.39.2914] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Himpsel FJ, Chandrashekhar GV, McLean AB, Shafer MW. Orientation of the O 2p holes in Bi2Sr2Ca1Cu2O8. Phys Rev B Condens Matter 1988; 38:11946-11948. [PMID: 9946110 DOI: 10.1103/physrevb.38.11946] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Fein AP, Kirtley JR, Shafer MW. Tunneling measurements of the dependence of the energy gap on critical temperature in La2-xSrxCuO4-y. Phys Rev B Condens Matter 1988; 37:9738-9741. [PMID: 9944368 DOI: 10.1103/physrevb.37.9738] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Burns G, Dacol FH, Kliche G, Konig W, Shafer MW. Raman and infrared studies of Sr2TiO4: A material isomorphic to (La,Sr)2CuO4 superconductors. Phys Rev B Condens Matter 1988; 37:3381-3388. [PMID: 9944929 DOI: 10.1103/physrevb.37.3381] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Schlesinger Z, Collins RT, Shafer MW, Engler EM. Normal-state reflectivity and superconducting energy-gap measurement of La2-xSrxCuO4. Phys Rev B Condens Matter 1987; 36:5275-5278. [PMID: 9942163 DOI: 10.1103/physrevb.36.5275] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Penney T, Shafer MW, Olson BL, Plaskett TS. Comparisons of Transport Properties, Electron Deficiency and Superconducting Tcin the La2-xSrxCuO4-δsystem and YBa2Cu3O9-δ. ACTA ACUST UNITED AC 1987. [DOI: 10.1111/j.1551-2916.1987.tb00121.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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DiMarzio D, Croft M, Sakai N, Shafer MW. Effect of pressure on the electrical resistance of EuO. Phys Rev B Condens Matter 1987; 35:8891-8893. [PMID: 9941284 DOI: 10.1103/physrevb.35.8891] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Schlesinger Z, Collins RT, Shafer MW. Observation of a low-energy infrared anomoly in superconducting La1.85Sr0.15CuO4. Phys Rev B Condens Matter 1987; 35:7232-7234. [PMID: 9941010 DOI: 10.1103/physrevb.35.7232] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Kirtley JR, Tsuei CC, Park SI, Chi CC, Rozen J, Shafer MW. Local tunneling measurements of the high-Tc superconductor La2-xSrxCuO4-y. Phys Rev B Condens Matter 1987; 35:7216-7219. [PMID: 9941006 DOI: 10.1103/physrevb.35.7216] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Warnock J, Awschalom DD, Shafer MW. Orientational behavior of molecular liquids in restricted geometries. Phys Rev B Condens Matter 1986; 34:475-478. [PMID: 9939291 DOI: 10.1103/physrevb.34.475] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Mehran F, Stevens KW, Shafer MW, Fitzpatrick WJ. Electron paramagnetic resonance of the incommensurate cooperative Jahn-Teller compound Tl2PbCu(NO2)6. Phys Rev B Condens Matter 1985; 32:7083-7090. [PMID: 9936846 DOI: 10.1103/physrevb.32.7083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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