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Tarvainen O, Orpana J, Kronholm R, Kalvas T, Laulainen J, Koivisto H, Izotov I, Skalyga V, Toivanen V. The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source. Rev Sci Instrum 2016; 87:093301. [PMID: 27782615 DOI: 10.1063/1.4962026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The efficiency of the microwave-plasma coupling plays a significant role in the production of highly charged ion beams with electron cyclotron resonance ion sources (ECRISs). The coupling properties are affected by the mechanical design of the ion source plasma chamber and microwave launching system, as well as damping of the microwave electric field by the plasma. Several experiments attempting to optimize the microwave-plasma coupling characteristics by fine-tuning the frequency of the injected microwaves have been conducted with varying degrees of success. The inherent difficulty in interpretation of the frequency tuning results is that the effects of microwave coupling system and the cavity behavior of the plasma chamber cannot be separated. A preferable approach to study the effect of the cavity properties of the plasma chamber on extracted beam currents is to adjust the cavity dimensions. The results of such cavity tuning experiments conducted with the JYFL 14 GHz ECRIS are reported here. The cavity properties were adjusted by inserting a conducting tuner rod axially into the plasma chamber. The extracted beam currents of oxygen charge states O3+-O7+ were recorded at various tuner positions and frequencies in the range of 14.00-14.15 GHz. It was observed that the tuner position affects the beam currents of high charge state ions up to several tens of percent. In particular, it was found that at some tuner position / frequency combinations the plasma exhibited "mode-hopping" between two operating regimes. The results improve the understanding of the role of plasma chamber cavity properties on ECRIS performances.
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Affiliation(s)
- O Tarvainen
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - J Orpana
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - R Kronholm
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - T Kalvas
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - J Laulainen
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - H Koivisto
- Department of Physics (JYFL), University of Jyväskylä, 40500 Jyväskylä, Finland
| | - I Izotov
- Institute of Applied Physics, RAS, 46 Ul'yanova St., 603950 Nizhny Novgorod, Russian Federation
| | - V Skalyga
- Institute of Applied Physics, RAS, 46 Ul'yanova St., 603950 Nizhny Novgorod, Russian Federation
| | - V Toivanen
- European Organization for Nuclear Research (CERN), 1211 Geneva 23, Switzerland
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