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Leppink E, Lau C, Lin Y, Wukitch SJ. Evaluation of the Abel inversion integral in O-mode plasma reflectometry using Chebyshev-Gauss quadrature. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:063506. [PMID: 37862546 DOI: 10.1063/5.0132246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 06/15/2023] [Indexed: 10/22/2023]
Abstract
The Abel transform is often used to reconstruct plasma density profiles from O-Mode polarized reflectometry diagnostics. However, standard numerical trapezoidal evaluation of the Abel inversion integral can be computationally expensive for a large number of evaluation points, and an endpoint singularity exists on the upper-bound of the integral, which can result in an increased error. In this work, Chebyshev-Gauss quadrature is introduced as a new method to evaluate the Abel inversion integral for the problem of O-Mode plasma reflectometry. The method does not require numerical evaluation of an integral singularity and is shown to have similar accuracy compared to existing methods while being computationally efficient.
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Affiliation(s)
- E Leppink
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - C Lau
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Lin
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - S J Wukitch
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
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Wen J, Shi ZB, Zhong WL, Yang ZC, Yang ZJ, Wang B, Jiang M, Shi PW, Hillesheim JC, Freethy SJ, Shi P, Liang AS, Tong RH, Fang KR, Deng WC, Liu Y, Yang QW, Ding XT, Xu M. A remote gain controlled and polarization angle tunable Doppler backward scattering reflectometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:063513. [PMID: 34243534 DOI: 10.1063/5.0043676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 05/15/2021] [Indexed: 06/13/2023]
Abstract
Remote control of the diagnostic systems is the basic requirement for the high performance plasma operation in a fusion device. This work presents the development of the remote control system for the multichannel Doppler backward scattering (DBS) reflectometers. It includes a remote controlled quasi-optical system and a remote intermediate frequency (IF) amplifier gain control system. The quasi-optical system contains a rotational polarizer, its polarization angle is tunable through a remote controlled motor, and it could combine the microwave beams with a wide frequency range into one focused beam. The remote IF gain control system utilizes the digital microcontroller (MCU) technique to regulate the signal amplitude for each signal channel. The gain parameters of amplifiers are adjustable, and the feedback of working status in the IF system will be sent to MCU in real time for safe operation. The gain parameters could be controlled either by the Ethernet remote way or directly through the local control interface on the system. Preliminary experimental results show the effectiveness of the remote controlled multichannel DBS system.
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Affiliation(s)
- J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z J Yang
- Huazhong University of Science and Technology, Wuhan 430074, China
| | - B Wang
- University of Electronic Science and Technology of China, Chengdu 610054, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J C Hillesheim
- Culham Centre for Fusion Energy, Abingdon, Oxon OX14 3DB, United Kingdom
| | - S J Freethy
- Culham Centre for Fusion Energy, Abingdon, Oxon OX14 3DB, United Kingdom
| | - P Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - A S Liang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - R H Tong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - K R Fang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W C Deng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Q W Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X T Ding
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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Bogar O, Zajac J, Zacek F, Varavin M, Hron M, Panek R, Silva A. Microwave reflectometer for density profile and turbulence measurements on the COMPASS tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:013515. [PMID: 32012635 DOI: 10.1063/1.5099345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 01/07/2020] [Indexed: 06/10/2023]
Abstract
The fast microwave reflectometer system on the COMPASS tokamak consists of an O-mode polarized K-band (18 GHz-26 GHz), Ka-band (26 GHz-40 GHz), and a part of U-band (40 GHz-54 GHz). The plasma density profile from the edge plasma area is measured using a fast sweeping rate up of to 6 µs of the probing wave. The processing of the reflected signal is realized by the heterodyne detection configuration based on the I/Q modulator. Two different methods of dynamic calibration of the required linear sweep frequency, together with static frequency and dispersion calibration, were used. The electron density profile was reconstructed by a spectrogram-based method with four sweeps on average. The system has the capability to measure the mid-plane low-field side electron density profile in the density range from 4 × 1018 m-3 to 3.6 × 1019 m-3. Experimental results obtained on COMPASS discharges are presented to demonstrate the performance of the diagnostics.
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Affiliation(s)
- O Bogar
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - J Zajac
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - F Zacek
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - M Varavin
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - M Hron
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - R Panek
- Institute of Plasma Physics, The Czech Academy of Sciences, 182 00 Prague, Czech Republic
| | - A Silva
- Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico da Universidade de Lisboa, 1049-001 Lisboa, Portugal
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Molina Cabrera P, Coda S, Porte L, Smolders A. V-band nanosecond-scale pulse reflectometer diagnostic in the TCV tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:123501. [PMID: 31893830 DOI: 10.1063/1.5094850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 10/11/2019] [Indexed: 06/10/2023]
Abstract
This article describes the realization of a novel approach to short pulse (∼1 ns) reflectometry (SPR) recently implemented in the tokamak configuration variable tokamak. Taking advantage of a fast arbitrary waveform generator and vector-network-analyzer extension modules, the design offers flexibility regarding pulse output frequency, duration, and repetition rate. Such flexibility allows the instrument to overcome traditional SPR spatial sampling limitations while reducing hardware complexity. In order to measure the group-delay of nanosecond-scale pulses, both traditional analog and novel digital sampling techniques have been explored. A group-delay range resolution of 17 ps (2.6 mm) in average over the V-band has been achieved with both timing techniques against a waveguide mirror featuring 10 dB power fluctuations. Direct pulse sampling during L-mode plasmas shows that reflected pulse widths increase only by 4% in average. However, pulse width dispersion does occur in L-mode plasmas and leads to an increase in the group-delay uncertainty up to 40 ps (6 mm). Raw histograms of group-delay data show interesting qualitative changes from the L mode to the H-mode. Frequency spectra of group-delay data allow the identification of macroscopic density fluctuations as well as edge quasicoherent modes during edge-localized mode-free H-modes. Finally, fast changes to the density profile have been measured with microsecond time resolution and subcentimeter spatial resolution in both O and X-mode polarizations.
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Affiliation(s)
- P Molina Cabrera
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center(SPC), CH-1015 Lausanne, Switzerland
| | - S Coda
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center(SPC), CH-1015 Lausanne, Switzerland
| | - L Porte
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center(SPC), CH-1015 Lausanne, Switzerland
| | - A Smolders
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center(SPC), CH-1015 Lausanne, Switzerland
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Sabot R, Giacalone JC, Nam Y, Berne A, Brun C, Elbèze D, Faisse F, Gargiulo L, Kim M, Lee W, Lotte P, Park HK, Santraine B, Yun G. Development of Microwave Imaging Diagnostics for WEST Tokamak. JOURNAL OF FUSION ENERGY 2019. [DOI: 10.1007/s10894-019-00216-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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