Speaker
Description
J-PARC 3 GeV rapid cycling synchrotron (RCS) is one of the highest beam power proton accelerator, which accelerates 8.3 x 10^13 protons at 25 Hz up to 3 GeV, corresponding 1 MW beam power. Challenges for achieving low pressure region of ultrahigh vacuum (UHV) less than 10^-5 Pa in RCS beam line are the following outgassing source.
1. Outgassing from large surface area of beam pipes and other vacuum devices due to large aperture to accept the burst number of protons.
2. Outgassing of water due to unbakeable beam line to prevent ceramics beam pipes from breaking by excessive stress due to thermal expansion of nearby beam pipes.
3. Additional outgassing originated from high power beam: thermal outgassing due to beam hit to a charge exchange foil or collimators; molecules desorption from vacuum surface by hitting of ionized residual gas.
We focused turbo molecular pump (TMP) as main pump because TMP can evacuate such continuous and additional outgassing with large pumping speed in wide pressure range. It is also possible to evacuate from low vacuum to UHV with only a few hours by using TMP, which ensures users’ experimental time after vacuum device maintenance. TMP During more than 10 years operation of the vacuum system, many experiences have been accumulated about the usage of TMP in RCS. In this presentation, we discussed about validity of TMS as main pump in high power proton accelerator by showing the performance of the beam line pressure during the beam operation, few troubles, ease of operation, etc. Further, in anticipation of upgrade higher beam power more than 1 MW, where lower pressure should be required, validity of a combination of TMP and NEG pump will be mentioned.
