Agenda and Summary:
1) Updates on SC quads -- B.Parker
2) Continue discussion of IR civil issues (push-pull, etc) -- C.Corvin, T.Markiewicz
3) SiD tracker issues affecting detector mechanical design, assembly, etc. -- B.Cooper
4) Earlier unreported work, ff for 4.5L* & e-e- optics in 2mrad -- A.Seryi
Updates on SC quads :
Brett presented an updated design of self-shielded compact SC quad compatible with crossing angle 14mrad with L*=3.5m (cold extraction beampipe). This is to be compared with design of the last week (September 13, 2005 meeting), where design for 15.4mrad at L*=3.5m was presented. The angle was decreased by reducing number of layers for compensation coil from two to one, reducing extraction aperture from r=13mm to r=12mm, reducing space for helium, etc. The achieved 49mm beam separation (which gives 14mrad at 3.5m) is the minimum which seems reasonable without pushing the technology too far. Smaller crossing angle can be achieved with proportionally longer L*. The corresponding version with warm extraction beampipe get to 14mrad at L*=4.5m. Brett also presented design of first extraction quad, also based on self-shielded concept, as well as design of the self-shielded prototype which soon will be wound and tested at BNL.
Continue discussion of IR civil issues (push-pull, etc):
Clay presented several versions of collider hall layout: 1) two independent
halls shifted longitudinally by >100m, 30m*60m each; 2) single IR hall with two
push pull detectors on two beams, 35m*149m; 3) single IR hall with two push pull
detectors on single beam, 35m*120m. Applying the same cost per square meter, the
cost figures rise in the order 1)-3)-2). One need to discuss further the hall
area really needed for detector construction and maintenance, since the
assumptions on hall sizes in cases 2)-3) may have been rather generous depending
on the assembly-operation scenario chosen for the baseline.
Tom suggested to think about civil layout and construction that would make it more flexible and would allow to postpone decisions on IR layout or crossing angle. For example, single long collider hall, or wider tunnels for extraction may help to provide such flexibility and need to be discussed further.
SiD tracker issues affecting detector mechanical design, assembly:
Bill discussed the SiD concept for servicing the vertex detector, in which the central tracker moves out longitudinally by about 2.6m. This result in certain requirements on the external sizes of FD elements up to about 9m from IP. The present SiD assumption for the external size of FD is r=20cm. One need to watch this dimension for consistency with evolving design of FD for 20mrad, 2mrad or intermediate crossing angle cases. Another interface issue to discuss is design of bellows which are placed between conical beampipe coming from IP and FD. Several technologies under consideration for vertex require operation below room temperature, some at -90 C degrees. For those technologies, these bellows, in particular, allow for contraction of vertex. To provide 0.5mm/10m alignment of VXD, these bellows should be guided, flexible longitudinally and constrained transversely. Questions such as rf shielding, fingers, and whether two or just one bellow needed, should be studied.
ff for 4.5L* & e-e- optics in 2mrad:
The work on ff design for 2mrad IR with L*=4.5m and considerations for e-e- in 2mrad case were done earlier, on August 11-12, and referenced, for example, in Snowmass optics summary talk. But the files were not posted. Here they are now. The associated optics files are also here.
Andrei Seryi, 09/21/05