The Joint Accelerator Conferences Website (JACoW) is an international collaboration that publishes the proceedings of accelerator conferences held around the world.
TY - UNPB AU - Izotov, I. AU - Kalvas, T. AU - Koivisto, H. A. AU - Komppula, J. AU - Kronholm, R.J. AU - Laulainen, J.P. AU - Mansfeld, D. AU - Skalyga, V. AU - Tarvainen, O.A. ED - Schaa, Volker RW TI - Broadband Microwave Emission Spectrum Associated With Kinetic Instabilities in ECR Plasmas J2 - Proc. of ECRIS2016, Busan, Korea, August 28 - September 1, 2016 C1 - Busan, Korea T2 - International Workshop on ECR Ion Sources T3 - 22 LA - english AB - ECRISs are susceptible to kinetic instabilities due to resonance heating mechanism forming an anisotropic electron velocity distribution function. Well-known and frequently observed extracted ion beam current oscillations in case of high heating power and/or low magnetic field gradient are proven to be caused by the instabilities of cyclotron type leading to a notable reduction of highly-charged ion beam intensities. It has been shown recently that heating power level and magnetic field gradient affect the spectrum of microwave emission of plasma related to cyclotron instabilities, being in the frequency range of 8-14 Ghz. More detailed study of microwave emission spectrum of ECR plasma conducted with an improved setup is presented in this work. It was found that frequencies of microwaves emitted by the plasma can be far beyond the primary heating frequency (14 GHz) and up to 25 GHz. Moreover, a threshold transition from periodic pulsed emission to a CW emission has been observed in the experiment for the first time, as was predicted theoretically*. The transition occurs at certain threshold levels of heating microwave power and magnetic field gradient. PB - JACoW CP - Geneva, Switzerland ER -