| Paper | Title | Page |
|---|
| WEP28 | Latest Results of ILC High-Gradient R&D 9-cell Cavities at JLAB | 525 |
| | - R. L. Geng, R. Afanador, A. C. Crawford, G. K. Davis, D. Forehand, C. Dreyfus, C. Grenoble, B. Golden, R. Johnson, P. Kushnick, K. Macha, J. Mammosser, J. Saunders, A. Wu
JLab - D. Bice, D. A. Sergatskov
Fermilab
| |
| | It has been over a year since JLAB started processing
and testing ILC 9-cell cavities in the frame work of
ILC high-gradient cavity R&D, aiming at the goal of a
35 MV/m gradient at a Q0 of 1E10 with a yield of 90%.
The necessary cavity processing steps include field flatness
tuning, electropolishing (EP), hydrogen out-gassing under
vacuum, high-pressure water rinsing, clean room assembly,
and low temperature bake. These are followed by RF
test at 2 Kelvin. Ultrasonic cleaning with Micro-90, an effective
post-EP rinsing recipe discovered at JLAB, is routinely
used. Seven industry manufactured 9-cell TESLAshape
cavities are processed and tested repeatedly. So far,
33 EP cycles are accumulated, corresponding to more than
65 hours of active EP time. An emphasis put on RF testing
is to discern cavity quench characteristics, including its nature
and its location. Often times, the cavity performance is
limited by thermal-magnetic quench instead of field emission.
The quench field in some cavities is lower than 20
MV/m and remains unchanged despite repeated EP, implying
material and/or fabrication defects. The quench field
in some other cavities is high but changes unpredictably
after repeated EP, suggesting processing induced defects.
Based on our experience and results, several areas are identified
where improvement is needed to improve cavity performance
as well as yield. | |