| 3 | Chirping instabilities produced by a runaway electron beam at a spherical tokamak显示文摘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. | 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 | 2023 | Plasma Science and Technology2023，25，7： | 0 |
| 4 | Development of Zeff diagnostic system on the Globus-M(M2) tokamak and the first experimental results显示文摘Studying the behavior of effective ion charge Zeff, which indicates the degree of pollution of plasma and can provide valuable information about many processes taking place in plasma, mechanisms of the releasing impurities, transport, etc is of great interest. This paper describes the development of the Zeff diagnostic system for the Globus-M2 tokamak. The effective ion charge is determined on the basis of measurements of the bremsstrahlung intensity and Thomson scattering data-Te and ne profiles. The results of the first Zeff measurements obtained for several discharges on the Globus-M tokamak are presented in this paper. The results have been validated by simulation using the ASTRA transport code for the same discharges, and it has demonstrated a good agreement with the experimental results. | E A TUKHMENEVA S Yu TOLSTYAKOV G S KURSKIEV V K GUSEV V B MINAEV Yu V PETROV N V SAKHAROV A Yu TELNOVA N N BAKHAREV P B SHEGOLEV E O KISELEV | 2019 | Plasma Science and Technology2019，21，10： | 0 |
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