WG-D meeting, August 15, 2007.
Present: Seryi, Maruyama, Burrows, Parker, Damerell, Kozanecki, Sugimoto, White, Oriunno,
Abe, Malyshev, Mokhov, Keller, Nosochkov, Sullivan, Markiewicz, Angal-Kalinin, Mau, Pei
(+possibly other colleagues)
Very brief minutes. Only selected questions/discussion are written below.
Nikolai Mokhov presented tolerances for detector to background. See slides for details.
Comment: 0.2 hit/mm^2/train is specific for Si tracker, not TPC (slide 5).
Question: are muons in calorimeter an issue?
Comment: considering PFA, the detector should be robust to muons.
Chris Damerell's comment: VX based on ccd are indeed sensitive to radiation
damage. The mentioned earlier LHC-like VX detectors are indeed much more
resistant to rad damage, but their pixel size is ~25 times larger.
But there are other designs considered that promise to be much more
resistant.
Takashi Maruyama presented background driven design decisions in SiD. See slides.
Comment: with respect to the question do we need an M2 mask, suggested
to apply background tolerances presented in the previous talk and based
on that give recommendation if M2 is needed or not.
Witold: for evaluation of collimation depth and available margin,
need to include possible misalignment of the elements.
With respect to neutrons, it was pointed that beamcal act as collimator,
and if it is opened, there are a lot more neutrons hitting vertex.
(Results by Siva Darbha et al). This may need to be studies further.
Lew Keller presented vacuum requirements from beam-gas point of view.
See a summary slide and a linked ILC-note.
Requiremants are 1ntorr up to 200m from IP, 10ntorr from 200m to 800m.
In the IP drift the pressure could be larger than 1ntorr -- thus from
beam gas point of view there is no need to have a pump in the IR region.
Question from Malyshev: what gas composition was used? Lew: similar
to the one measured in SLC arc. Comment: in the environment with cryo-cold
bore the gas composition could be different.
Andrei presented first draft of requirements on magnetic field along the
detector beamline from the beam dynamics point of view. See slides.
The limits can be set only on variation of the field in time, not on on static value
(which may need to be limited by safety or other consideration).
For further studies of collimation, suggested to look at inperfect
conditions, like increased emittances, opened gaps, not perfectly
tuned lattice, and see how big a safety margin there is in the system
and how it could be improved.
Suggestion to look at PEP-II design and consider if its experience
is relevant.
