Status Of the 2 Be Button Testing Cavity

Status Of the 2 Be Button Testing Cavity RF meeting Monday, 11/28/11

History of Testing Ø Ø Ø Ø Testing has been nearly completed with Magnet field of 3 T. About 9 M pulses of be used in the testing, pulse length of 20 us 10 Hz. Multipactoring was observed at the start at 0 T at 0. 57 MV/m. After 2 M pulses, multipactoring stopped during the pulse, but persisted in the decay tail of the pulse at about 0. 57 MV/m. After day shut down the multipactoring would appear again, but disappear after a few thousand pulses. The cavity was RF commissioned upto 27 MV/m after 1 M pulses the sparking rate was less than 1/100, 000. Total number of sparks about 25. At this point the magnet was turned on at 3 T. Multipactor started at 40 MV/m and disappeared after 0. 5 M pulses except for the decay tail. The cavity was RF commissioned upto 26 MV/m with 0. 5 M pulses with a sparking rate of less than 1/100, 000. At this point the cavity was RF commissioned upto 40 MV/m at 0 T because the previous RF commissioning at 0 T was reached nearly the same as the 3 T value (27 vs 26 MV/m respectively) with 2 M pulses and a sparking rate of less than 1/30, 000

History of Testing Ø At this point the magnet was turned on at 3 T and RF commissioning continued upto 31 MV/m with sparking rate of 1/10, 000 with about 3 M pulses. Ø Increasing the gradient at this point to 31. 5 MV/m resulted in a extremely high rate of sparking with many consecutive breakdowns at the beginning of the pulse. This has been the signature of the final limit in a magnetic field. Ø So the safe operating limit for the 2 Be button test is 31 MV/m.

Summary and Future Plans. • We have reached a breakdown limit of 31 MV/m in a 3 T field after RF commissioning with 3 M pulses at low sparking rate 1/10, 000. • We plan to RF commission the cavity again at 31 MV/m to achieve a sparking rate less than 1/100, 000. • At this point we plan on removing the Be button and installing the copper buttons for comparison.