SRF2011 - List of Authors (Nakamura, N.)

Paper	Title	Page
TUPO005	High Power Tests of KEK-ERL Input Coupler for Main Linac Under LN2 Condition	356
	H. Sakai, T. Furuya, N. Nakamura, K. Umemori KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	We fabricated the prototype of an input coupler, which has two ceramic windows to keep the inside of the superconducting cavity clean, for ERL main linac and performed the high power test. Required input power is about 20kW with standing wave condition for the cavity acceleration field of 20MV/m. In this high power test, the one ceramic window, named as a cold window, was installed into the vacuum insulating chamber and cooled by liquid Nitrogen. First, the multipacting at 10kW level prevented the power increasing. By using the pulse processing method for 8 hours, power finally reached the 25kW with standing wave condition. We could also keep feeding 20kW power into coupler for 16 hours. The maximum measured temperature rises under feeding the 20 kW power to coupler were 120K near the bellows parts and these are not so severe values to operate ERL main linac. After power test, the thermal cycle test of cold window of coupler was done. After 10-times thermal cycle tests between the room temperature and liquid Nitrogen temperature, no leaks and cracks were observed. From these results of high power test, this prototype coupler satisfied our thermal and RF requirements.

Paper

Title

Page

High Power Tests of KEK-ERL Input Coupler for Main Linac Under LN2 Condition

356

H. Sakai, T. Furuya, N. Nakamura, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

We fabricated the prototype of an input coupler, which has two ceramic windows to keep the inside of the superconducting cavity clean, for ERL main linac and performed the high power test. Required input power is about 20kW with standing wave condition for the cavity acceleration field of 20MV/m. In this high power test, the one ceramic window, named as a cold window, was installed into the vacuum insulating chamber and cooled by liquid Nitrogen. First, the multipacting at 10kW level prevented the power increasing. By using the pulse processing method for 8 hours, power finally reached the 25kW with standing wave condition. We could also keep feeding 20kW power into coupler for 16 hours. The maximum measured temperature rises under feeding the 20 kW power to coupler were 120K near the bellows parts and these are not so severe values to operate ERL main linac. After power test, the thermal cycle test of cold window of coupler was done. After 10-times thermal cycle tests between the room temperature and liquid Nitrogen temperature, no leaks and cracks were observed. From these results of high power test, this prototype coupler satisfied our thermal and RF requirements.