CERN Accelerating science

Article
Report number	CERN-ATS-2013-016
Title	Operation and Thermal Modeling of the ISIS H– Source from 50 to 2 Hz Repetition Rates
Author(s)	Pereira, H (CERN) ; Faircloth, D (Rutherford) ; Lettry, J (CERN)
Publication	2013
Imprint	25 Jan 2013
Number of pages	8
In:	AIP Conf. Proc. 1515 (2013) 114-120
In:	3rd International Symposium on Negative Ions, Beams and Sources, Jyväskylä, Finland, 3 - 7 Sep 2012, pp.114-120
DOI	10.1063/1.4792777
Subject category	Accelerators and Storage Rings
Free keywords	Linac4 ; ISIS ; H− ; ion source ; low repetition rate ; thermal model
Abstract	CERN’s Linac4 accelerator H− ion source, currently under construction, will operate at a 2 Hz repetition rate, with pulse length of 0.5 ms and a beam current of 80 mA. Its reliability must exceed 99 % with a mandatory 3 month uninterrupted operation period. A Penning ion source is successfully operated at ISIS; at 50 Hz repetition rate it reliably provides 55 mA H− pulses of 0.25 ms duration over 1 month. The discharge plasma ignition is very sensitive to the temperatures of the discharge region, especially of its cathode. The investigation by modeling and measurement of operation parameters suitable for arc ignition and H− production at 2 Hz is of paramount importance and must be understood prior to the implementation of discharge ion sources in the Linac4 accelerator. In its original configuration, the ISIS H− source delivers beam only if the repetition rate is above 12.5 Hz, this paper describes the implementation of a temperature control of the discharge region aiming at lower repetition rate operation. The experimental results of the modified source successfully operated down to 1.6 Hz and providing 30 mA H− pulses of 0.75 ms duration are presented. A thermal modeling of the ISIS ion source gives insight to the relevant parameters. The analysis demonstrates the adaptability of discharge sources for the operating conditions of the Linac4.

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