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Effects of externally-generated electrons on pressure measurements of inverted magnetron gauges at Diamond

DOI: 10.1016/j.vacuum.2009.04.019 DOI Help

Authors: Hugo Shiers (Diamond Light Source) , Bastien Boussier (ITER Organisation) , Stephen Bryan (Diamond Light Source) , Brian Macdonald (Diamond Light Source) , Andrew Wolfenden (Diamond Light Source) , Matthew Cox (Diamond Light Source)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: 12th Joint Vacuum Conference (JVC-12)
Peer Reviewed: Yes

State: Published (Approved)
Published: April 2009

Abstract: Diamond Light Source (Diamond) utilises a large number of Inverted Magnetron Gauges (IMGs) for both monitoring the vacuum and as a source of interlocks for protection of the machine. During storage ring operation it has been found that, in the presence of the stored electron beam, charged particles, assumed to be electrons, impinging on some of the gauges cause the pressures indicated by the gauges to drop to zero which causes problems with the operation of the storage ring. Diamond has designed and fitted a magnetic filter at the neck of each affected gauge port to eliminate this problem. This paper reports on and discusses experiments and proposed experiments with an electron flood gun and IMGs from two different manufacturers (MKS Instruments and Pfeiffer Vacuum) aimed at obtaining a better understanding of the effect. Externally-generated electrons from the flood gun can cause serious errors in the pressures indicated by the gauges; the error can be positive or negative depending on the gauge current-measuring circuit. Methods aimed at eliminating these spurious pressure readings, such as magnetic filters, bias voltages within the gauges and the use of earth meshes and baffles are also discussed.

Journal Keywords: Vacuum; Pressure Measurement; Electrons; Synchrotron; Storage Ring

Subject Areas: Physics

Technical Areas: Vacuum