Recent performance of the SNS H(-) ion source and low-energy beam transport system

Recent measurements of the H(-) beam current show that SNS is injecting about 55 mA into the RFQ compared to ∼45 mA in 2010. Since 2010, the H(-) beam exiting the RFQ dropped from ∼40 mA to ∼34 mA, which is sufficient for 1 MW of beam power. To minimize the impact of the RFQ degradation, the service...

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Bibliographic Details
Published in:Review of scientific instruments 2014-02, Vol.85 (2), p.02B137-02B137
Main Authors: Stockli, Martin P, Ewald, K D, Han, B X, Murray, Jr, S N, Pennisi, T R, Piller, C, Santana, M, Tang, J, Welton, R
Format: Article
Language:English
Subjects:
BEAM CURRENTS
BEAM TRANSPORT
CORONA DISCHARGES
ELECTRIC POTENTIAL
ELECTRODES
ELECTRONS
HEATING LOAD
ION SOURCES
LENSES
PARTICLE ACCELERATORS
START-UP
THERMOCOUPLES
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Summary:Recent measurements of the H(-) beam current show that SNS is injecting about 55 mA into the RFQ compared to ∼45 mA in 2010. Since 2010, the H(-) beam exiting the RFQ dropped from ∼40 mA to ∼34 mA, which is sufficient for 1 MW of beam power. To minimize the impact of the RFQ degradation, the service cycle of the best performing source was extended to 6 weeks. The only degradation is fluctuations in the electron dump voltage towards the end of some service cycles, a problem that is being investigated. Very recently, the RFQ was retuned, which partly restored its transmission. In addition, the electrostatic low-energy beam transport system was reengineered to double its heat sinking and equipped with a thermocouple that monitors the temperature of the ground electrode between the two Einzel lenses. The recorded data show that emissions from the source at high voltage dominate the heat load. Emissions from the partly Cs-covered first lens cause the temperature to peak several hours after starting up. On rare occasions, the temperature can also peak due to corona discharges between the center ground electrode and one of the lenses.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4862205