Electron heating, time evolution of bremsstrahlung and ion beam current in electron cyclotron resonance ion sources
This thesis is a study of Electron Cyclotron Resonance Ion Source (ECRIS) plasmas and their properties. The focus has been on time evolution studies of bremsstrahlung emission, ion beam current production and numerical studies of electron heating in ECRIS plasmas. The time scales for reaching steady state bremsstrahlung production at electron energies greater than 30 keV is shown to be on the order of several hundreds of milliseconds. The ion beam currents of different elements are shown to reach steady state before the bremsstrahlung production. It is also demonstrated that by tuning the RF pulse patterns, the so-called preglow transient ion beam currents can be utilized while the amount of bremsstrahlung radiation can be significantly reduced. In numerical work it has been found, for example, that the number of high energy electrons decreases when the microwave power absorption has been modeled. The thesis is divided in the following way: Chapter 1 is a short introduction to the ECR ion source field including motivation to electron heating studies; Chapter 2 contains basic properties of plasma physics that are needed to understand the behaviour of plasmas; Chapter 3 introduces the reader to ECR ion sources, operational principles and mechanisms dictating the production of highly-charged ions; Chapter 4 concentrates on electron heating via microwaves, describing limitations in the heating processes. The model for the electromagnetic (EM) wave absorption and the description of the simulation code developed in this thesis work are presented. In addition, properties of some of the existing electron heating / ECRIS codes are discussed. Chapter 5 deals with the bremsstrahlung production, discusses some of the previous bremsstrahlung measurements and presents the experimental apparatus. Chapter 6 contains the summary of the numerical and experimental results, and Chapter 7 concludes the thesis. ...
PublisherUniversity of Jyväskylä
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Plasma response to amplitude modulation of the microwave power on a 14 GHz electron cyclotron resonance ion source Neben, Derek; Tarvainen, Olli; Kronholm, Risto; Koivisto, Hannu; Kalvas, Taneli; Machicoane, Guillaume; Leitner, Daniela (AIP Publishing, 2018)This paper reports the effects of sinusoidal microwave power Amplitude Modulation (AM) on the performance of Electron Cyclotron Resonance (ECR) ion sources. The study was conducted on the 14 GHz ECR ion source ECR2 at the ...
Effect of double frequency heating on the lead afterglow beam currents of an electron cyclotron resonance ion source Toivanen, V.; Bellodi, G.; Küchler, D.; Wenander, F.; Tarvainen, Olli (American Physical Society, 2017)The effect of double frequency heating on the performance of the CERN GTS-LHC 14.5 GHz Electron Cyclotron Resonance (ECR) ion source in afterglow mode is reported. The source of the secondary microwave frequency was operated ...
Tarvainen, Olli; Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Laulainen, Janne; Izotov, I.; Mansfeld, D.; Skalyga, V.; Toivanen, V. (Institute of Applied Physics of the Russian Academy of Sciences, 2014)Experimental observation of cyclotron instabilities in electron cyclotron resonance ion source plasma operated in cwmode is reported. The instabilities are associated with strong microwave emission and a burst of energetic ...
Transverse distribution of beam current oscillations of a 14 GHz electron cyclotron resonance ion source Tarvainen, Olli; Toivanen, Ville; Komppula, Jani; Kalvas, Taneli; Koivisto, Hannu (American Institute of Physics, 2014)The temporal stability of oxygen ion beams has been studied with the 14 GHz A-ECR at JYFL (University of Jyvaskyla, Department of Physics). A sector Faraday cup was employed to measure the distribution of the beam current ...
High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source Skalyga, V.; Izotov, I.; Golubev, S.; Sidorov, A.; Razin, S.; Strelkov, A.; Tarvainen, Olli; Koivisto, Hannu; Kalvas, Taneli (American Institute of Physics, 2015)In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with ...