Dissipative Drift Instability Driven by Neutral Particles in the Edge Plasma of Tokamaks

Abstract

S (a) 1.V.Kurchatov Inmtitute, Momcow, USSR ( b ) Central Inmtitute of Electrun Phymicm, Academy of S c i m c e m o f the GDR, Berlin 1. Introduction It im u e l l known that in the edge plamaa of tokarakm m t r o n g d m m i t y and potential fluctuations exist which can lead to a n o m a l w s tranmport p h m o r e n a /I/. There are mreamonm to suppome that the level o f theme fluctuationm im c o n n u t e d with neutral particle fluxes penetrating into the plamaa due to gampufting or recycling procesmem. The dimmipative drift d e i m one o f the momt important rodem in the collimion dominated ed9r plamma /2-41. We investigate the influence o f neutral particlcm on the bchavioClr o f theme nodem. We s h o w that their mtability criteria may br changed mignificantly by taking into conmidrration the ionization o f the n wtral particle. and charge-exchange proccmmes. It i m knoun that in the abmence o f neutralm the ragnetic m h e a r mtabilirem the dimmipative drift modem in the mlab approximation /3/. Our calculationm m h o u that theme modem may become unstable owing to ionization procermem if the concentration o f the neutral particlrm e x c w d m m o m s critical value, wheream the charge-exchange doem not affect the mtability. In the toroidal geometry theme nodem conserve their main proprtiem, but the value of the critical neutral denmity i m mlightly m o d i f i d . On the other hand, mome unmtable molutionm of the eigenvalucequation f o r the drift waves exist in the a b m m c e of neutral prrticlem, which arc connected with the mtrong toroidal rode coupling. They dirmappear in the plamma mlab limit / 4 / . The incr-t o f t h s e nodes is modified significantly both by ionization and charge-exchange. The i'onization of the neutral particles leads always to an increasing of the increment. The influence of charge-exchange procesmem on the time b e h a v i w r of the drift waves dependm on their frequcnciem. A C o n t r i b . Plasma Phys. 30 (1990)1. 31-35 /1/ P.C.Li-r, Nuc1.Fusion 23 (1985) 543 /2/ B.B.Kadoatsev, 0.P.Pogutse. "Voprosy teorii plasma-, vyp. 3 Atomizdat,'Moscou 1971

Novel test-bed facility for PSI issues in fusion reactor conditions on the base of next generation QSPA plasma accelerator

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