Polarimetric Thomson scattering for high T e fusion plasmas

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A: JT-60SA will complement ITER in resolving key issues to finally decide an acceptable DEMO design. Diagnostics play a key role in this mission. The electron temperature and density profiles are measured by a core and an edge Thomson scattering (TS) diagnostics with high spatial resolution, needed to identify the pedestal parameters and small profile structures. The two systems use a common tangential Nd:YAG laser beam path in the plasma equatorial plane. The collection optics for the edge system (low field side) is hosted in a lower oblique port and that for the core system in a horizontal port. The optics fit in the port plug tube and image the scattering volumes into an array of fiber bundles. They both are exposed to a high neutron dose of 10 16 n/cm 2 over 13 years of operation. The optics are supported by a mechanical structure decoupled from the cryostat. A set of filter polychromators with avalanche photodiode (APD) detectors spectrally analyze the 1Corresponding author.

Section: Performance Simulationmentioning

confidence: 99%

Section: Performance Simulationmentioning

confidence: 99%

Conceptual design of JT-60SA edge Thomson scattering diagnostic

Pasqualotto

Tojo

Fassina³

et al. 2020

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“…To calculate the plasma light background we followed the same method as used for ITER [14]. First we have generated 2D T e and n e maps in the plasma poloidal cross section, associating to each (R, Z) point of the flux computational grid the T e and n e values determined by interpolating the 1D T e and n e profiles in correspondence of the local value of the poloidal flux.…”

Section: The Dtt Core Thomson Scattering Systemmentioning

confidence: 99%

Design of Thomson scattering diagnostics for the Divertor Tokamak Test (DTT) facility

Giudicotti¹,

Fassina²,

Pasqualotto³

et al. 2020

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In the Divertor Tokamak Test (DTT) facility two Thomson scattering (TS) systems are under design for the measurements of T e and n e in the core plasma region and in the divertor respectively. The divertor TS system under study is a conventional TS system based on a Nd:YAG laser source, a fiber optic based light collection system and a set of filter polychromators equipped with Si APD detectors. The laser beam and the collection optics share an aperture between adjacent cassettes of the lower divertor and the scattering signal is collected from a set of scattering volumes close to one of the divertor legs by a collection optics system located under the divertor dome and is carried to the polychromators by fiber optic bundles. The filter polychromators are designed to measure T e as low as 1 eV. Measurements with a spatial resolution of 10 mm are possible, with accuracy limited by the plasma n e and the background light. For the core TS system, two options are under consideration: a conventional system, similar to that designed for the ITER core TS, in which T e and n e are measured along a large fraction of a laser beam crossing the plasma near the equatorial plane and the detection system is again based on fiber optic coupled filter polychromators. The spatial resolution is 5 cm in the central region and 1 cm at the plasma edge. Alternatively a TS system based on the LIDAR concept, previously implemented in JET, is under consideration. Recent advancements in laser and detector technology allow achieving a spatial resolution similar to that of a conventional system, but with a simpler and reliable experimental set-up and possibly at a lower cost. K: Plasma diagnostics -interferometry, spectroscopy and imaging; Nuclear instruments and methods for hot plasma diagnostics 1Corresponding author.

“…[19] the solutions became a subject of a thorough verification by the Italian group headed by Prof. L. Giudicotti. The purpose of their work was to benchmark the expressions (2.14) with the purely numerical 3D integration code independently developed by this group for TS polarization analysis [22]. The main steps and results of the verification are decribed below.…”

Section: Verification Of the Frequency-resolved Solutionsmentioning

confidence: 99%

Relativistic electron kinetic effects on laser diagnostics in burning plasmas

Mirnov

Hartog

2018

Toroidal interferometry/polarimetry (TIP), poloidal polarimetry (PoPola), and Thomson scattering systems (TS) are major optical diagnostics being designed and developed for ITER. Each of them relies upon a sophisticated quantitative understanding of the electron response to laser light propagating through a burning plasma. Review of the theoretical results for two different applications is presented: interferometry/polarimetry (I/P) and polarization of Thomson scattered light, unified by the importance of relativistic (quadratic in v T e /c) electron kinetic effects. For I/P applications, rigorous analytical results are obtained perturbatively by expansion in powers of the small parameter τ = T e /m e c 2 , where T e is electron temperature and m e is electron rest mass. Experimental validation of the analytical models has been made by analyzing data of more than 1200 pulses collected from high-T e JET discharges. Based on this validation the relativistic analytical expressions are included in the error analysis and design projects of the ITER TIP and PoPola systems. The polarization properties of incoherent Thomson scattered light are being examined as a method of T e measurement relevant to ITER operational regimes. The theory is based on Stokes vector transformation and Mueller matrices formalism. The general approach is subdivided into frequencyintegrated and frequency-resolved cases. For each of them, the exact analytical relativistic solutions are presented in the form of Mueller matrix elements averaged over the relativistic Maxwellian distribution function. New results related to the detailed verification of the frequency-resolved solutions are reported. The precise analytic expressions provide output much more rapidly than relativistic kinetic numerical codes allowing for direct real-time feedback control of ITER device operation. K: Plasma diagnostics -interferometry, spectroscopy and imaging; Analysis and statistical methods 1Corresponding author.