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Title: Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects

Abstract

This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (T{sub e}) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured T{sub e} and intensity of the signals. How accurate the values are depends on the electron temperature (T{sub e}) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high T{sub e} and a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the T{sub e} in a wide T{sub e} range spanning over two orders of magnitude (0.01–1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the T{sub e} measurements are valid undermore » harsh radiation conditions. This method to obtain T{sub e} can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments.« less

Authors:
; ; ; ;  [1]; ; ; ;  [2]; ; ;  [3]
  1. National Institutes for Quantum and Radiological Science and Technology, 801-1 Mukoyama, Naka 311-0193 (Japan)
  2. National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan)
  3. Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561 (Japan)
Publication Date:
OSTI Identifier:
22597625
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 9; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ACCURACY; APPROXIMATIONS; CALIBRATION; COMPUTERIZED SIMULATION; ELECTRON TEMPERATURE; ELECTRONS; ERRORS; KEV RANGE 01-10; LHD DEVICE; OPTICAL FIBERS; PLASMA; SIGNALS; SPHERICAL CONFIGURATION; TEMPERATURE MEASUREMENT; THOMSON SCATTERING; TOKAMAK DEVICES; VALIDATION; WINDOWS

Citation Formats

Tojo, H., E-mail: tojo.hiroshi@qst.go.jp, Hiratsuka, J., Yatsuka, E., Hatae, T., Itami, K., Yamada, I., Yasuhara, R., Funaba, H., Hayashi, H., Ejiri, A., Togashi, H., and Takase, Y.. Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects. United States: N. p., 2016. Web. doi:10.1063/1.4961476.
Tojo, H., E-mail: tojo.hiroshi@qst.go.jp, Hiratsuka, J., Yatsuka, E., Hatae, T., Itami, K., Yamada, I., Yasuhara, R., Funaba, H., Hayashi, H., Ejiri, A., Togashi, H., & Takase, Y.. Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects. United States. doi:10.1063/1.4961476.
Tojo, H., E-mail: tojo.hiroshi@qst.go.jp, Hiratsuka, J., Yatsuka, E., Hatae, T., Itami, K., Yamada, I., Yasuhara, R., Funaba, H., Hayashi, H., Ejiri, A., Togashi, H., and Takase, Y.. 2016. "Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects". United States. doi:10.1063/1.4961476.
@article{osti_22597625,
title = {Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects},
author = {Tojo, H., E-mail: tojo.hiroshi@qst.go.jp and Hiratsuka, J. and Yatsuka, E. and Hatae, T. and Itami, K. and Yamada, I. and Yasuhara, R. and Funaba, H. and Hayashi, H. and Ejiri, A. and Togashi, H. and Takase, Y.},
abstractNote = {This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (T{sub e}) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured T{sub e} and intensity of the signals. How accurate the values are depends on the electron temperature (T{sub e}) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high T{sub e} and a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the T{sub e} in a wide T{sub e} range spanning over two orders of magnitude (0.01–1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the T{sub e} measurements are valid under harsh radiation conditions. This method to obtain T{sub e} can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments.},
doi = {10.1063/1.4961476},
journal = {Review of Scientific Instruments},
number = 9,
volume = 87,
place = {United States},
year = 2016,
month = 9
}
  • This paper presents an experimental demonstration to determine electron temperature (T{sub e}) with unknown spectral sensitivity (transmissivity) in a Thomson scattering system. In this method, a double-pass scattering configuration is used and the scattered lights from each pass (with different scattering angles) are measured separately. T{sub e} can be determined from the ratio of the signal intensities without knowing a real chromatic dependence in the sensitivity. Note that the wavelength range for each spectral channel must be known. This method was applied to the TST-2 Thomson scattering system. As a result, T{sub e} measured from the ratio (T{sub e,r}) andmore » T{sub e} measured from a standard method (T{sub e,s}) showed a good agreement with <|T{sub e,r}-T{sub e,s}|/T{sub e,s}>= 7.3%.« less
  • A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.
  • We present the first simultaneous measurements of the Thomson scattering and electron cyclotron emission radiometer diagnostics performed at TCABR tokamak with Alfven wave heating. The Thomson scattering diagnostic is an upgraded version of the one previously installed at the ISTTOK tokamak, while the electron cyclotron emission radiometer employs a heterodyne sweeping radiometer. For purely Ohmic discharges, the electron temperature measurements from both diagnostics are in good agreement. Additional Alfven wave heating does not affect the capability of the Thomson scattering diagnostic to measure the instantaneous electron temperature, whereas measurements from the electron cyclotron emission radiometer become underestimates of the actualmore » temperature values.« less
  • By comparison with high-resolution synchrotron x-ray experimental results, we assess several theoretical treatments for the bound-free (core-electron) contribution to x-ray Thomson scattering (i.e., also known as nonresonant inelastic x-ray scattering). We identify an often overlooked source of systematic error in the plane-wave form factor approximation (PWFFA) used in the inference of temperature, ionization state, and free electron density in some laser-driven compression studies of warm dense matter. This error is due to a direct violation of energy conservation in the PWFFA. We propose an improved practice for the bound-free term that will be particularly relevant for XRTS experiments performed withmore » somewhat improved energy resolution at the National Ignition Facility or the Linac Coherent Light Source. Our results raise important questions about the accuracy of state variable determination in XRTS studies, given that the limited information content in low-resolution XRTS spectra does not strongly constrain the models of electronic structure being used to fit the spectra.« less