New Results on Field Emission Suppression
in EP Multi-Cell Cavities at JLab
Rong-Li GengJefferson Lab
ILC10, March 26-30, 2010, Beijing, China
2
Field Emission On-set Analysis of EP Multi-Cell Cavities at JLab
Rongli Geng ILC10, 3/26-30, 2010, Beijing, Chnia
Gradient at which first X-ray detected above background
ILC10, 3/26-30, 2010, Beijing, Chnia 3
First EP 7-Cell Cavity w/o FE at 35 MV/mthis results directed us to EP 9-cell at lower temperature
Rongli Geng
R.L. Geng et al., LINAC08
ILC10, 3/26-30, 2010, Beijing, Chnia 4
Maximum Gradient in EP Multi-Cell Cavities
Rongli Geng
ILC10, 3/26-30, 2010, Beijing, Chnia 5
Example of EP 9-Cell Cavity w/o FE
Rongli Geng
ILC10, 3/26-30, 2010, Beijing, Chnia 6
Latest EP 9-Cell Result w/o FE at 40 MV/m
Rongli Geng
41 MV/m reached during initial power rise, at which gradient precursor FE startedLater power rise limited to 40 MV/m to prevent explosive emitter activation
ILC10, 3/26-30, 2010, Beijing, Chnia 7
Summary
Rongli Geng
• In more than a dozen of 35-40 MV/m EP multi-cell cavity tests, more than 80% demonstrated FE-free performance.
• Improvements in several aspects of cavity processing, handling and assembly are found beneficial.
• Gradient push beyond 40 MV/m are sometimes stopped in view of pre-cursor FE turn on.
• Further studies needed to fully understand the phenomenon.
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