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.