WG-B, August 2, 2007
Present: K.C.Wu, Andy Marone, Brett Parker, Tsuchiya, Weisend, Jeremie, Seryi, Oriunno, Malyshev, Pattalwar, Pei, Tauchi, Markiewicz, Kozanecki, Morse, Burrows, Meyners, Amann
Brett discussed IR model focusing in particular on issues relevant to cryo and vacuum design (see slides). The drawings are also posted, to provide information to other groups, however they are obsolete. The design work is ongoing, in particular to remove the step on the back of the QD0 cryostat.
"Cavity" in the cold-warm transition in the IP side of QD0 cryostat need to be investigated in terms of RF losses and conductivity of heat into the 2K system. In principle, the two beamlines could be continued through this "cavity" region, provided they are not touching the outer wall of the cryostat, or do so via some RF fingers.
Oleg Malyshev gave some comments about vacuum issues that need to be understood. In particular, Hydrogen would be of most concern in terms of forming a mono-layer on cold surface, since it has the least bonding energy with surface, and could be most easily detached when affected by SR or pairs. While water should be of smaller concern, since its bonding to cold surface is much stronger. This comment is based on experiments performed for SSC. However photon energy used at this experiments was about 300eV and in ILC case the energy can be larger. To proceed with vacuum system design, one need to know the geometry (given in the drawings) and flux for SR and pairs.
Tom Markiewicz touched on neutron flux and how it relates to extraction quad aperture. A question to follow-up is to understand if the extraction quad material (which is not much) does indeed reduce neutron flux to vertex noticeably.
Bill Morse mention if Boron could be added to beam dump water to capture neutrons -- this however may created corrosion and other issues that could not be tolerated.
John Amann have shown preliminary 3d model of pacman which demonstrates that pacman can be opened despite the knee-like geometry of the cryo-line. Further optimization of pacman will proceed.
Expected at the next meeting
-- more detailed design of QD0 cryostat (without a step at the back end), maybe more definite sizes;
Actions:
-- provide geometry and flux information to vacuum experts.
