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Offeddu N, Wüthrich C, Han W, Theiler C, Golfinopoulos T, Terry JL, Marmar E, Galperti C, Andrebe Y, Duval BP, Bertizzolo R, Clement A, Février O, Elaian H, Gönczy D, Landis JD. Gas puff imaging on the TCV tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:123504. [PMID: 36586925 DOI: 10.1063/5.0126398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/04/2022] [Indexed: 06/17/2023]
Abstract
We present the design and operation of a suite of Gas Puff Imaging (GPI) diagnostic systems installed on the Tokamak à Configuration Variable (TCV) for the study of turbulence in the plasma edge and Scrape-Off-Layer (SOL). These systems provide the unique ability to simultaneously collect poloidal 2D images of plasma dynamics at the outboard midplane, around the X-point, in both the High-Field Side (HFS) and Low-Field Side (LFS) SOL, and in the divertor region. We describe and characterize an innovative control system for deuterium and helium gas injection, which is becoming the default standard for the other gas injections at TCV. Extensive pre-design studies and the different detection systems are presented, including an array of avalanche photodiodes and a high-speed CMOS camera. First results with spatial and time resolutions of up to ≈2 mm and 0.5 µs, respectively, are described, and future upgrades of the GPI diagnostics for TCV are discussed.
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Affiliation(s)
- N Offeddu
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - C Wüthrich
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - W Han
- MIT, Plasma Science and Fusion Center (PSFC), Cambridge, Massachusetts 02139, USA
| | - C Theiler
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - T Golfinopoulos
- MIT, Plasma Science and Fusion Center (PSFC), Cambridge, Massachusetts 02139, USA
| | - J L Terry
- MIT, Plasma Science and Fusion Center (PSFC), Cambridge, Massachusetts 02139, USA
| | - E Marmar
- MIT, Plasma Science and Fusion Center (PSFC), Cambridge, Massachusetts 02139, USA
| | - C Galperti
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - Y Andrebe
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - B P Duval
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - R Bertizzolo
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - A Clement
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - O Février
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - H Elaian
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - D Gönczy
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
| | - J D Landis
- EPFL, Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
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Feng D, Diallo A, Shneider MN. Two-color scattering for the measurement of neutrals at the edge of fusion devices. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:063515. [PMID: 34243505 DOI: 10.1063/5.0027481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 05/26/2021] [Indexed: 06/13/2023]
Abstract
Laser two-color scattering (TCS) is proposed to detect the neutral species in the edge of fusion devices, namely, tokamaks. TCS uses two wavelengths to probe both the laser Rayleigh scattering and Thomson scattering of the neutral-electron bath, with emphasis on neutral density measurements such as that of hydrogen and deuterium. Modeling of the Rayleigh scattering of tokamak neutral species under various plasma conditions (electron density and temperature) shows that, with an appropriate filtering of the Thomson signal and by going to ultraviolet-region wavelengths, identification of the Rayleigh signal can be achieved. Photon count and signal fractions are calculated in two test cases, one in the midplane region of the National Spherical Torus Experiment and one in the divertor region of DIII-D. An uncertainty analysis and discussion of the feasibility of the TCS diagnostic is also presented.
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Affiliation(s)
- David Feng
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Ahmed Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08544, USA
| | - Mikhail N Shneider
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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Stotler D, Ku S, Zweben S, Chang C, Churchill R, Terry J. Shadowing effects in simulated Alcator C-Mod gas puff imaging data. NUCLEAR MATERIALS AND ENERGY 2019. [DOI: 10.1016/j.nme.2019.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Churchill RM, Theiler C, Lipschultz B, Dux R, Pütterich T, Viezzer E. Development of the gas puff charge exchange recombination spectroscopy (GP-CXRS) technique for ion measurements in the plasma edge. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:093505. [PMID: 24094058 DOI: 10.1063/1.4821084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A novel charge-exchange recombination spectroscopy (CXRS) diagnostic method is presented, which uses a simple thermal gas puff for its donor neutral source, instead of the typical high-energy neutral beam. This diagnostic, named gas puff CXRS (GP-CXRS), is used to measure ion density, velocity, and temperature in the tokamak edge/pedestal region with excellent signal-background ratios, and has a number of advantages to conventional beam-based CXRS systems. Here we develop the physics basis for GP-CXRS, including the neutral transport, the charge-exchange process at low energies, and effects of energy-dependent rate coefficients on the measurements. The GP-CXRS hardware setup is described on two separate tokamaks, Alcator C-Mod and ASDEX Upgrade. Measured spectra and profiles are also presented. Profile comparisons of GP-CXRS and a beam based CXRS system show good agreement. Emphasis is given throughout to describing guiding principles for users interested in applying the GP-CXRS diagnostic technique.
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Affiliation(s)
- R M Churchill
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
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