||While degassing hydrogen at an
elevated temperature (>600 C) can reduce the chance of Q degradation
(Q disease), eliminating this process would significantly reduce the
production cost and time of cavities. Past published data
elsewhere have shown significant Q disease at relatively low
frequencies such as the 130 MHz quarter-wave resonator at JAERI despite
general observation of insignificant effect on low-frequency cavities.
We have tested our 350 MHz spoke cavities and found that these
cavities do not show any Q disease after up to 24 hours of holding at
100 K, but show the disease with longer holding time, although the
extent of the degradation was different between the two cavities.
Elastic Recoil Detection Analyses (ERDA) data on the hydrogen
content and the depth profile in niobium used for the fabrication of
our spoke cavities will also be shown with various surface treatments.
Finally, insights from these studies into what is the best way to
treat cavity to avoid high-temperature degassing will be drawn.