--- NOTES --- (Courtesy S. Verdu)
- [G. Burt] At 3.2 MV, about 0.150 W (rms value) get dissipated in HOM filter assuming thermal conductivity K = f(T) and BCS resistance R = f(T) with Rs = 5 nOhm. [R. Calaga] However, Q-slope does not change significantly when the quench field level is approached.
- [O. Capatina] At 4 K, the niobium will extract heat better than the helium.
- [G. Burt] If dissipated power is 1 W in tip, the helium channel will not be able to extract the heat.
- [B. P. Xiao] Quench level at 2 K and 4 K was 2.8 MV in CW operation for the cold test of cavity 001+HOM. [R. Calaga] What would happen if test is conducted at higher temperature?
- [G. Burt] Showed paper “SRF95F24” with dependence of thermal conductivity on temperature and RRR. [O. Capatina] CERN picked a high RRR bulk niobium in order to ensure a high thermal conductivity in the HOM filter.
- [R. Calaga] How thermal gradient changes with rotation of the hook?
- [I. Ben-Zvi] Presume bad spot with high resistance. This is a more realistic approach than assuming low thermal resistance all over the HOM filter. This bad spot may be the main drive for the thermal behaviour of the HOM filter instead of the k = f(T) and R = f(T) and may explain why quench level is equal at different bath temperatures.
- [R. Calaga] Shall we perform a 600C bake after the 50 um BCP? A 600C bake is usually performed after bulk BCP to degass hydrogen and reduce Q-disease. [Q. Wu] expressed concern about HOM filter changing shape with baking. [O. Capatina] said filter will not change shape with baking.
- [S. Verdu] Shall we perform a light BCP after the 600C bake? A light BCP is usually performed after 600C baking to remove furnace contaminants.
- [B. P. Xiao asked R. Calaga] Surface of spacer exposed to RF fields will be NbTi and use RF seal gaskets.
- [R. Calaga] Why did T. Powers (JLab) used a 10 MHz mixer during the col test of cavity 001+HOM?
- [I. Ben-Zvi] Highlighted the need to work on a HOM filter design with reduced attenuation in the pass band.
- [R. Calaga] CERN cryo team has camara working at 2 K. We could use the camera to look into the cavity. [S. Verdu] We should check the visual angle from HOM2 port to HOM filter tip…
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