WG-A meeting, July 30.
Present: Gaddi, Herve, Parker, Borrows, Weisend, Buesser, Meyners, Sanuki, Seryi, Kozanecki, Sugimoto, Sanami, Yamamoto, Markiewicz (+possibly, other colleagues)
First, discussed the interface document with comments added by Alain Herve (see red text in the attached document).
In particular, the following points were highlighted or would need further discussion:
Suggest 20-40t crane in the hall and 2000k crane on surface. The 400-500t crane in the hall leads to a lot of disadvantages and problems (like larger hall, the need for support pillars, etc.)
The thick shaft cover could be shared between two shafts; as well as the gantry crane -- it could be shared too (and could move between shafts in a week, if needed). Buildings on surface could be rearranged to allow this scheme.
Sugimoto-san mentioned that joined GLD-LDC may be smaller and could have barrel less than 6000t and with three segments may be possible to use pure CMS style. But needed to have large crane to move shielding. The latter was met with skepticism, and was suggested that smaller shielding blocks could be used, and could be moved on air-pads.
The detailed optimization of shielding is needed and fine tuning of crane capacity is needed.
Hitoshi said that GLD-LDC will launch the merging working group in a month. Output from IRENG07 will be certainly used by this group.
Continuing discussion of the interface document, Alain and other CERN colleagues suggested that two service caverns (maybe smaller, and possibly with smaller, 6-9m shafts) may be more suitable. In present scheme there are elevators and stairs in the main large shafts, but this create interference in the hall, and some hall area become unavailable due to this. The access shafts in the service caverns will solve this. That would mean one more shaft, however. Accommodation of such suggestion would be possible if optimization of hall sizes and other systems would prove the cost effectiveness.
The escape safety also need to be taken into account: in Europe (CERN & DESY) the rule applicable to collider hall requires to have less than 40m distance to the exit. The size of ILC collider hall may need to be considered from this point of view.
Alain continued discussion and said that one need to consider how detector is open (for TPC extraction, for example) in the garage position. There could be several solutions, e.g. to have an alcove in the hall, just in the place where detector is opened (local widening of the hall), or to have the detector not centered in the hall, to have larger space on one side.
In discussion it was then also suggested to consider rotating the detector along the hall, in garage position (the services connection and the moving system become more difficult then); and to consider if the detector platform would move not exactly along the hall, but at small angle, so that in garage position it end up closer to one of the walls.
Vaccum requirements were discussed, and one of the questions was where is the first pump, is there NEG coating in vacuum chamber, what is pressure requirement for the drift between faces of QD0 cryostats, etc.
The magnetic field requirements were discussed. The present 50Gs (placeholder) limit was questioned. In comparison, for CMS the field outside of the yoke could be 700-800Gs. In terms of human presence, 2kGs is allowed by CERN rules (trained personnel; while for general public the limit is 5Gs). Mechanical safety (objects moving in magnetic field) is difficult if the field is more than few hundred Gauss. This issue is to be followed -- field may need to be specified separate in different regions, e.g. along beamline, outside of barrel, etc.
The questionnaire from CFS colleagues (attached) was discussed. It was noted that detectors groups are fragmented and it is hard to get the overall summary numbers of power and other requirements. To start with, it was suggested to prepare tables for CMS, SLD and possibly other detectors, and use it to start discussion with detector colleagues.
Alain continued discussion with remarks about fire safety.
Below is the extract from Alain's email that was discussed at the meeting:
"One point in your list I would like to be more specific about is fire safety. We have concluded at CERN, for the LHC experiments, that the main risk for underground experiments of losing investment and mission is fire, and we have taken measures early on.
Thus I think some requirements MUST be imposed to detectors from the beginning to prevent arguing later on.
- no flammable gas mixure should be used underground.
- smoke detection, Vesda type, with sufficient granularity inside the subdetectors should be mandatory.
- as it is long to maneuver the heavy doors of detectors, the inner volume of vacuum tanks must be maintained at low oxygen content.
- outside the detectors fire fighting systems must be foreseen, suppression gases and sprinkler or foam.
_ exclusive use of halogen free cables (this decision was seen as difficult to apply when decided here, but finally people have succeeded to procure correct cables, but this needs effort and has to be considered very early on in the game). "
It was agreed to include these suggestions into the interface document.
For the next WG-A meeting (on Aug.6), the discussion items would be:
1) Schemes to open detector in garage position -- CERN colleagues would prepare some sketches.
2) Andrea Gaddi would put together CMS fto fill in CFS questioonaire.
3) GLD would present discussion what would be needed to use pure CMS style assembly, and also discuss if non-split door can be used -- Sugimoto-san et al.
4) Magnetic field safety document from CERN will be distributed and discussed.
5) Vacuum and pumping, how it is done at CMS -- Alain Herve at al.
6) Discuss two cervice caverns (with decreased size of access shafts) -- Alain et al.
7) Scheme with shared 2000t crane and shaft cover and 20-40t crane in the hall will be prepared for discussion -- Alain et al.
