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Liu X, Domier CW, Dannenberg J, Zhu Y, Sirigiri JR, Ren Y, Stratton B, Luhmann NC. The National Spherical Torus Experiment-Upgrade poloidal high-k scattering system pitch angle design modifications. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:103509. [PMID: 36319363 DOI: 10.1063/5.0099912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 08/23/2022] [Indexed: 06/16/2023]
Abstract
A 693 GHz, eight-channel, poloidal high-k (k refers to wavenumber) collective scattering system is under development for the National Spherical Torus Experiment-Upgrade device. It will replace the previous 280 GHz, five-channel, tangential scattering system to study high-k electron density fluctuations, thereby providing a measurement of the kθ-spectrum of both electron temperature gradient and ion temperature gradient modes. A tool is under development to calculate the wavenumber that exists in the presence of strong magnetic pitch angles. We use this tool to motivate a new receiver optical design for significantly improved performance, details of which are presented herein.
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Affiliation(s)
- X Liu
- University of California at Davis, 1 Shields Ave., Davis, California 95616, USA
| | - C W Domier
- University of California at Davis, 1 Shields Ave., Davis, California 95616, USA
| | - J Dannenberg
- University of California at Davis, 1 Shields Ave., Davis, California 95616, USA
| | - Y Zhu
- University of California at Davis, 1 Shields Ave., Davis, California 95616, USA
| | - J R Sirigiri
- Bridge 12 Technologies, Inc., 37 Loring Drive, Framingham, Massachusetts 01702, USA
| | - Y Ren
- Princeton Plasma Physics Laboratory, 100 Stellarator Rd., Princeton, New Jersey 08540, USA
| | - B Stratton
- Princeton Plasma Physics Laboratory, 100 Stellarator Rd., Princeton, New Jersey 08540, USA
| | - N C Luhmann
- University of California at Davis, 1 Shields Ave., Davis, California 95616, USA
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Barchfeld R, Domier CW, Ren Y, Ellis R, Riemenschneider P, Allen N, Kaita R, Stratton B, Dannenberg J, Zhu Y, Luhmann NC. The high- k poloidal scattering system for NSTX-U. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:10C114. [PMID: 30399655 DOI: 10.1063/1.5035410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 06/25/2018] [Indexed: 06/08/2023]
Abstract
An 8-channel, high-k poloidal far-infrared (FIR) scattering system is under development for the National Spherical Torus eXperiment Upgrade (NSTX-U). The 693 GHz poloidal scattering system replaces a 5-channel, 280 GHz high-k toroidal scattering system to study high-k electron density fluctuations on NSTX-U. The FIR probe beam launched from Bay G is aimed toward Bay L, where large aperture optics collect radiation at 8 simultaneous scattering angles ranging from 2° to 15°. The reduced wavelength in the poloidal system results in less refraction, and coupled with a new poloidal scattering geometry, extends measurement of poloidal wavenumbers from the previous limit of 7 cm-1 up to >40 cm-1. Steerable launch optics coupled with receiver optics that can be remotely translated in 5 axes allow the scattering volume to be placed from r/a = 0.1 out to the pedestal region (r/a ∼ 0.99) and allow for both upward and downward scattering to cover different regions of the 2D fluctuation spectrum.
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Affiliation(s)
- R Barchfeld
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - C W Domier
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - Y Ren
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Ellis
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - P Riemenschneider
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N Allen
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Kaita
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - B Stratton
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - J Dannenberg
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - Y Zhu
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N C Luhmann
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
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Shi P, Chen J, Gao L, Liu Y, Liu H, Zhou YN, Zhuang G. Far-forward collective scattering measurements by FIR polarimeter-interferometer on J-TEXT tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:11E110. [PMID: 27910372 DOI: 10.1063/1.4960067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The multi-channel three-wave polarimeter-interferometer system on J-TEXT tokamak has been exploited to measure far-forward collective scattering from electron density fluctuations. The diagnostic utilizes far infrared lasers operated at 432 μm with 17-channel vertical chords (3 cm chord spacing), covering the entire cross section of plasma. Scattering laser power is measured using a high-sensitivity Schottky planar diode mixer which can also detect polarimetric and interferometric phase simultaneously. The system provides a line-integrated measurement of density fluctuations with maximum measurable wave number: k⊥max ≤ 2 cm-1 and time response up to 350 kHz. Feasibility of the diagnostic has been tested, showing higher sensitivity to detect fluctuation than interferometric measurement. Capability of providing spatial-resolved information of fluctuation has also been demonstrated in preliminary experimental applications.
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Affiliation(s)
- P Shi
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - J Chen
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - L Gao
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Y Liu
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - H Liu
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Y N Zhou
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - G Zhuang
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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Lee W, Park HK, Lee DJ, Nam YU, Leem J, Kim TK. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:043501. [PMID: 27131668 DOI: 10.1063/1.4944834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm(-1). The upper limit corresponds to the normalized wavenumber kθρe of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.
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Affiliation(s)
- W Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - D J Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - Y U Nam
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - J Leem
- Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - T K Kim
- Kyunpook National University, Daegu 41566, South Korea
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The Dynamics of Core and Outer Micro-turbulence During the L–I–H Confinement Transition on the EAST Superconducting Tokamak. JOURNAL OF FUSION ENERGY 2015. [DOI: 10.1007/s10894-015-9949-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Cao GM, Li YD, Li Q, Zhang XD, Sun PJ, Wu GJ, Hu LQ. The Dynamics of Short-Scale Turbulent Fluctuations During The H–L Back Transition in The EAST Superconducting Tokamak. JOURNAL OF FUSION ENERGY 2015. [DOI: 10.1007/s10894-015-9861-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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A tangential CO 2 laser collective scattering system for measuring short-scale turbulent fluctuations in the EAST superconducting tokamak. FUSION ENGINEERING AND DESIGN 2014. [DOI: 10.1016/j.fusengdes.2014.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Ding WX, Lin L, Duff JR, Brower DL, Sarff JS. Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E302. [PMID: 23126962 DOI: 10.1063/1.4728098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The multichannel polarimeter-interferometer system on the MST reversed-field pinch can be utilized to measure far-forward collective scattering from electron density fluctuations. The collective scattering system has 11 viewing chords with ∼8 cm spacing. The source is a 432 μm (694 GHz) far infrared laser and the scattered power is measured using a heterodyne detection scheme. Collective scattering provides a line-integrated measurement of fluctuations within the divergence of the probe beam covering wavenumber range: k(⊥) < 1.3 cm(-1), corresponding k(⊥)ρ(s) < 1.3 (ρ(s) is the ion-sound Larmor radius), the region of primary interest for turbulent fluctuation-induced transport. The perpendicular wavenumber consists of toroidal, poloidal, and radial contributions, which vary with chord position. Coherent modes associated with tearing instabilities and neutral-beam driven fast particles are observed along with broadband turbulence at frequencies up to 500 kHz. Changes in frequency are consistent with a Doppler shift due to parallel plasma flow.
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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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Ren Y, Kaye SM, Mazzucato E, Guttenfelder W, Bell RE, Domier CW, LeBlanc BP, Lee KC, Luhmann NC, Smith DR, Yuh H. Density gradient stabilization of electron temperature gradient driven turbulence in a spherical tokamak. PHYSICAL REVIEW LETTERS 2011; 106:165005. [PMID: 21599377 DOI: 10.1103/physrevlett.106.165005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Indexed: 05/30/2023]
Abstract
In this Letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k(⊥)ρ(s) ≲ 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of 2 decrease in the plasma effective thermal diffusivity.
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Affiliation(s)
- Y Ren
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
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Guttenfelder W, Candy J, Kaye SM, Nevins WM, Wang E, Bell RE, Hammett GW, LeBlanc BP, Mikkelsen DR, Yuh H. Electromagnetic transport from microtearing mode turbulence. PHYSICAL REVIEW LETTERS 2011; 106:155004. [PMID: 21568568 DOI: 10.1103/physrevlett.106.155004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Indexed: 05/30/2023]
Abstract
This Letter presents nonlinear gyrokinetic simulations of microtearing mode turbulence. The simulations include collisional and electromagnetic effects and use experimental parameters from a high-β discharge in the National Spherical Torus Experiment. The predicted electron thermal transport is comparable to that given by experimental analysis, and it is dominated by the electromagnetic contribution of electrons free-streaming along the resulting stochastic magnetic field line trajectories. Experimental values of flow shear can significantly reduce the predicted transport.
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Affiliation(s)
- W Guttenfelder
- Princeton Plasma Physics Laboratory, Princeton New Jersey 08543, USA
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Smith DR, Kaye SM, Lee W, Mazzucato E, Park HK, Bell RE, Domier CW, Leblanc BP, Levinton FM, Luhmann NC, Menard JE, Yuh H. Observations of reduced electron Gyroscale fluctuations in national spherical torus experiment H-mode plasmas with large ExB flow shear. PHYSICAL REVIEW LETTERS 2009; 102:225005. [PMID: 19658873 DOI: 10.1103/physrevlett.102.225005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Indexed: 05/28/2023]
Abstract
Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.
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Affiliation(s)
- D R Smith
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
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