Chirping instabilities produced by a runaway electron beam at a spherical tokamak  

作　　者：I M BALACHENKOV N N BAKHAREV V K GUSEV M V ILIASOVA E M KHILKEVICH P S KORENEV A E KONKOV V B MINAEV Yu V MITRIZHKIN M I PATROV Yu V PETROV N V SAKHAROV A E SHEVELEV O M SKREKEL 

机构地区：[1]Ioffe Institute,Saint-Petersburg 194021,Russia [2]Lomonosov Moscow State University,Moscow 119991,Russia

出　　处：《Plasma Science and Technology》2023年第7期19-24,共6页等离子体科学和技术（英文版）

摘　　要：Two different types of MHD instabilities with rapidly chirping frequency were found to arise in the Globus-M2 spherical tokamak in substantially different frequency ranges.The first type arises at frequencies of an order of 1 MHz in ohmic plasmas at relatively low density(n_(e))<2×10^(19) m^(-3) in a wide range of toroidal magnetic fields and plasma currents.This type of instability was identified as compressional Alfven waves,driven by electrons,accelerated during a sawtooth crush.It was found that the mode frequency is sweeping in time,according to the Berk-Breizman hole-clump nonlinear chirping model.The second type of wave arises in a specific single-swing regime of the central solenoid current with a very narrow plasma column,when the plasma tends to decay at extremely low density(n_(e))<2×10^(18) m^(-3) and,in fact,is an instability of the runaway electron beam.The exited modes cover the whole observed frequency range and are divided into several(two or three)frequency regions:approximately 0-30 MHz,60-120 MHz and sometimes 30-60 MHz.Reconnection of the branches was also observed.Single chirps are more rapid than for 1 MHz Alfven instability and follow an exponential law.This paper,to our knowledge,is the first report of frequency chirping instabilities excited by accelerated electrons at a spherical tokamak.

关 键 词：Alfvén waves chirping instability spherical tokamak runaway electrons 

分 类 号：TL631.24[核科学技术—核技术及应用]