The ITER Thomson scattering core LIDAR diagnostic

Naylor, G.; Scannell, R.; Beurskens, M.; Walsh, Mike; Pastor, I.; Donné, Ajh Tony; Snijders, B.; Biel, W.; Mészáros, B.; Giudicotti, L.; Pasqualotto, R.; Marot, L.

doi:10.1088/1748-0221/7/03/c03043

Cited by 11 publications

(12 citation statements)

References 16 publications

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“…This has the key advantage of separating the requirements for high power handling of the laser mirror from wide spectral bandwidth for the collection mirror [26][27][28]. This also avoids the synergistic effect presented in this paper.…”

Section: Samplementioning

confidence: 96%

Synergistic effects of hydrogen plasma exposure, pulsed laser heating and temperature on rhodium surfaces

Marot

Temmerman

Doerner

et al. 2013

Journal of Nuclear Materials

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Section: Samplementioning

confidence: 96%

Synergistic effects of hydrogen plasma exposure, pulsed laser heating and temperature on rhodium surfaces

Marot

Temmerman

Doerner

et al. 2013

Journal of Nuclear Materials

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“…To improve this situation, here we adopt a design with two different laser wavelengths to expand the accessible temperature range. Such solutions have been proposed for conventional ITER TS systems [6] as well as for the ITER LIDAR TS [7,8]. This measure could be used for recalibration of the spectral transmission of the collection optics, too.…”

Section: Overview Of the Proposed Lidar Ts Systemmentioning

confidence: 99%

“…However, in [7,8] no description of a possible experimental realisation is given. In case of a LIDAR TS system the situation is different from a conventional system, where the two lasers are just fired within a few microseconds, a time delay within which the plasma profile does not change but the registration system is ready again.…”

Section: Overview Of the Proposed Lidar Ts Systemmentioning

confidence: 99%

LIDAR TS for ITER core plasma. Part I: layout & hardware

Salzmann¹,

Gowers

Nielsen

2017

J. Inst.

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The original time-of-flight design of the Thomson scattering diagnostic for the ITER core plasma has been shown up by ITER. This decision was justified by insufficiencies of some of the components. In this paper we show that with available, present day technology a LIDAR TS system is feasible which meets all the ITER specifications. As opposed to the conventional TS system the LIDAR TS also measures the high field side of the plasma.The optical layout of the front end has been changed only little in comparison with the latest one considered by ITER. The main change is that it offers an optical collection without any vignetting over the low field side. The throughput of the system is defined only by the size and the angle of acceptance of the detectors. This, in combination with the fact that the LIDAR system uses only one set of spectral channels for the whole line of sight, means that no absolute calibration using Raman or Rayleigh scattering from a non-hydrogen isotope gas fill of the vessel is needed. Alignment of the system is easy since the collection optics view the footprint of the laser on the inner wall.In the described design we use, simultaneously, two different wavelength pulses from a Nd:YAG laser system. Its fundamental wavelength ensures measurements of 2 keV up to more than 40 keV, whereas the injection of the second harmonic enables measurements of low temperatures.As it is the purpose of this paper to show the technological feasibility of the LIDAR system, the hardware is considered in Part I of the paper. In Part II we demonstrate by numerical simulations that the accuracy of the measurements as required by ITER is maintained throughout the given plasma parameter range. The effect of enhanced background radiation in the wavelength range 400 nm–500 nm is considered. In Part III the recovery of calibration in case of changing spectral transmission of the front end is treated. We also investigate how to improve the spatial resolution at the plasma edge.

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“…Both scattering angle and incident laser polarization are important parameters for Thomson scattering diagnostics. Most diagnostics operate with scattering angles near θ = π/2 but covering a wide range, while the LIDAR Thomson system proposed for ITER would operate near θ = π [8]. Universal (to our knowledge) use of linearly polarized incident light with the electric field aligned perpendicular to the scattering plane (parallel to the toroidal axis) originates in the simplicity offered to scattering spectrum calculation as well as optimization of scattered intensity for cold electrons.…”

Section: Diagnostic Implicationsmentioning

confidence: 99%

A polarization-based Thomson scattering technique for burning plasmas

2014

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The traditional Thomson scattering diagnostic is based on measurement of the wavelength spectrum of scattered light, where electron temperature measurements are inferred from thermal broadening of the scattered laser light. At sufficiently high temperatures, especially those predicted for ITER and other burning plasmas, relativistic effects cause a change in the polarization state of the scattered photons. The resulting depolarization of the scattered light is temperature dependent and has been proposed elsewhere as a potential alternative to the traditional spectral decomposition technique. Following similar work, we analytically calculate the degree of polarization for incoherent Thomson scattering. For the first time, we obtain exact results valid for the full range of incident laser polarization states and electron temperatures. While previous work focused only on linear polarization, we show that circularly polarized incident light optimizes the degree of depolarization for a wide range of temperatures relevant to burning plasmas. We discuss the feasibility of a polarization based Thomson scattering diagnostic for ITER-like plasmas with both linearly and circularly polarized light and compare to the traditional technique.

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The ITER Thomson scattering core LIDAR diagnostic

Cited by 11 publications

References 16 publications

Synergistic effects of hydrogen plasma exposure, pulsed laser heating and temperature on rhodium surfaces

Synergistic effects of hydrogen plasma exposure, pulsed laser heating and temperature on rhodium surfaces

LIDAR TS for ITER core plasma. Part I: layout & hardware

A polarization-based Thomson scattering technique for burning plasmas

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