GEM TOMOGRAPHIC MEASUREMENTS FOR WEST AND VALIDATION STRATEGIES 2 nd IAEA TM FDPVA 30 May-2 June 2017 Boston (USA) D.Mazon Many thanks to A. Jardin PAGE 1
GENERAL INTRODUCTION The tomographic SXR project for WEST is developed in collaboration with IPPLM (Poland) and Warsaw University IPPLM realize and provides the GEM detectors CEA is in charge of the integration of the GEM on Tore Supra Tests and calibration are realized jointly at IPPLM and CEA laboratories ER 2014 then 2015-18 project Team involved: Didier Mazon, Axel. Jardin, C. Coston, Philippe Malard, F. Faisse, J.M. Verger, S. Larroque, A. Bec, CEA, Cadarache, France Maryna Chernyshova, Tomasz Czarski, Karol Malinowski, Ewa Kowalska- Strzęciwilk, Sławomir Jabłoński, Barbara Bieńkowska, Rafał Prokopowicz, Adam Ziółkowski, Waldemar Figacz, Janina Pokorska IPPLM, Warsaw, Poland Krzysztof Poźniak, Grzegorz Kasprowicz, Wojciech Zabołotny, Andrzej Wojeński, Adrian Byszuk, Paweł Zienkiewicz, Rafał Krawczyk, Piotr Kolasiński WUT, Warsaw, Poland Marek Polasik, Katarzyna Słabkowska, Łukasz Syrocki UNC, Toruń, Poland
OUTLINE Introduction: motivations New WEST SXR tomographic system GEM synthetic diagnostics and validation W distribution reconstruction from tomographic inversion and domain of validity? Conclusions and perspectives
A NEW SOFT X-RAY (SXR) DIAGNOSTIC FOR WEST: MOTIVATION WEST (Tungsten (W) Environment in Steady-state Tokamak) is a test bed for ITER divertor components in long pulse operation. In this context, radiative cooling of impurities like tungsten (W) in the Soft X-Ray (SXR) range [0.1keV; 20keV] is a critical issue for the plasma core performances. Thus reliable tools are needed to monitor W density and avoid accumulation. The SXR diagnostic of WEST is composed of 2 new GEM (Gas Electron Multiplier) based cameras to perform 2D tomographic reconstructions with spectral resolution in tunable energy bands, useful for tungsten (W) transport studies in the plasma core. Ignition curves in presence of W [1] [1] T. Pütterich et al, 2010 Nucl. Fusion 50 025012 PAGE 4
GAS ELECTRON MULTIPLIER PRINCIPLE Gas: Ar/CO 2 Mylar foil no~e/30 Width 50 mm (Kapton) Q=no G e- PAGE 5
GEM TOMOGRAPHIC SYSTEM FOR WEST PAGE 6
GEM WEST DATA ACQUISITION NETWORK PAGE 7
FIRST PLASMA TESTS (PROTOTYPE) Remote connection works and first signals acquired! PAGE 8
SXR RADIATION OF IMPURITIES & INFLUENCE OF TRANSPORT PAGE 9
SXR RADIATION OF IMPURITIES & INFLUENCE OF TRANSPORT PAGE 10
GEM SYNTHETIC DIAGNOSTIC - STRATEGY FOR W RECONSTRUCTION PAGE 11
GEM SYNTHETIC DIAGNOSTIC - STRATEGY FOR W RECONSTRUCTION PAGE 12
MODEL VALIDATION: FE 55 [3] M. Chernyshova et al, Rev. Sci. Instrum. 87, 11E325 (2016) PAGE 13
INFLUENCE OF W CONCENTRATION ON ACQUIRED SPECTRUMS The WEST Physics Basis standard scenario with I p = 0.6 MA and heating power of P = 12 MW is used to predict the plasma SXR radiation for 3 different tungsten (W) concentrations: c W = 0 / 10 5 / 10 4 PAGE 14
2D SXR TOMOGRAPHY USING THE MINIMUM FISHER INFORMATION PAGE 15
W DENSITY RECONSTRUCTION STUDIES FOR WEST PAGE 16
W DENSITY RECONSTRUCTION STUDIES FOR WEST PAGE 17
CONCLUSIONS AND PERSPECTIVES WEST will be the first tokamak to use the GEM technology as SXR diagnostic for plasma tomography. The GEM will allow poloidal tomography with resolution in energy bands. Agreement between experimental and simulated acquisitions of a Fe 55 source that will be used on WEST for in situ calibration. W core density reconstruction is studied, in particular in presence of ICRH. In this work, the GEM spectral response is modelled and parametrized in a simple way thanks to the progam Magboltz. Preliminary studies on a WEST case including particle transport show that transport has a limited but potentially non negligeable impact on the W cooling factor and W density reconstruction. MORE TO COME PAGE 18
PAGE 19 J. Bucalossi - Organisation WEST 7 MARS 2013 Commissariat à l énergie atomique et aux énergies alternatives Centre de Cadarache 13108 Saint Paul Lez Durance Cedex T. +33 (0)4 42 25 46 59 F. +33 (0)4 42 25 64 21 Etablissement public à caractère industriel et commercial RCS Paris B 775 685 019 DSM
LORENTZ ANGLE PRINCIPLE: EXB DRIFT T = 30 C P = 1bar Deflection limit ~ 1 pixel length ~ 2mm ~ 10 Lorentz Angle PAGE 20
EFFECT OF EXB ON GEM MEASUREMENTS Results of MAGBOLTZ simulations: The code Magboltz uses a Monte-Carlo integration technique developed by CERN. Magboltz solves the Boltzmann transport equations for electrons in gas mixtures under the influence of electric and magnetic fields. Gas mixture: 45% Argon, 15% CO 2, 40%CF4 Temperature: 30 C Pressure: 1bar E min = 1kV/cm B max = 0.3T, at 90 (worst scenario) Lorentz Angle VS Magnetic field [T] Lorentz Angle VS ExB angle [ ] worst case Limit = 10 Extreme WEST scenario Lorentz angle max ~7 < 10 PAGE 21
EFFECT OF EXB ON GEM MEASUREMENTS Results of MAGBOLTZ simulations: Gas mixture: 45% Argon, 15% CO 2, 40%CF4 Temperature: 30 C Pressure: 1bar E min = 1kV/cm B max = 0.3T, at 90 (extreme scenario) Normal conditions Normal conditions Lorentz Angle VS Gas Pressure [bar] Lorentz Angle VS Temperature [C] Lorentz Angle stable enough to (T,P) changes PAGE 22