Agenda and Summary:
1) Energy deposition in SC QD0 for 2mrad -- Lew Keller, Takashi Maruyama
2) Updated ATF2 optics -- Mark Woodley
3) Cross-check of solenoid effects in BDSIM/DIMAD and plans -- John Carter
4) Effect of upstream photons on extraction line E deposition -- Mikhail Kostin
5) Alternative 1TeV high luminosity parameters -- Andrei Seryi
6) Updated DID fields for SiD, LDC, GLD -- Brett Parker, Andrei Seryi
Energy deposition in SC QD0 for 2mrad:
Takashi and Lew considered energy deposition in SC QD0 for 2mrad due to radiative Bhabhas. These particles are deposited along the QD0, primarily in the horizontal plane, in a very narrow vertical stripe, so that the energy density exceeds the safe limit of 0.5mW/g by about a factor of three, for the nominal 500GeV CM parameters, reaching 1.5mW/g (for short FD). For the long FD or 1TeV nominal case the density is ~2 higher. Solution to this issue has been suggested: use 3mm thin tungsten liner, which reduces the energy density by about a factor of ten.
Updated ATF2 optics:
Mark presented updated version of ATF2 optics with redesigned diagnostics section. In this case, the diagnostics section was shortened by about 5m in comparison with previous version, in order to increase space between IP and beam dump (to decrease background at the beam size monitor). Mark also shortened the skew quad section and lengthened the wire scanner section, in order to increase the beam size on wires to about 10microns, which would be easier to measure with 10micron carbon wires (installation of 4micron wires should also be considered). The FF bandwidth need to be reoptimized and work on post-IP optics need to be continued.
Cross check of solenoid effects in BDSIM:
John performed cross check of earlier DIMAD tracking with BDSIM tracking for the case of SiD detector solenoid which overlaps with final doublet. Tracking results agree quite well. John is also continuing development of 2mrad geometry in BDSIM, has build a pocket coil QF1 model, and evaluating collimation depth comparing it with envelope tracking results by Frank Jackson. BDSIM results shows the need for somewhat smaller collimation depth than envelope tracking. Studies continue.
Effects of upstream SR photons on extraction line:
Mikhail performed simulations to respond to the question asked at the previous meeting: what is the effect of upstream SR photons on the extraction line? Mikhail evaluated SR photons from the beam core and found that they do not contribute to losses in the extraction line. However, one also need to evaluate SR photons generated upstream of the IP by the beam halo. These studies will continue.
Alternative 1TeV high luminosity parameters:
Andrei presented an alternative parameter set for 1TeV High Luminosity case. One of the criteria was to reduce the low energy tail of the disrupted beam, in order to match to the energy acceptance of the extraction beamline. It is suggested that the energy, below which the power is 10W, should be at least 30% of the nominal energy. To satisfy this criteria, it is necessary to go back to 300um bunch, increase horizontal beam size, (it also helps to increase N by 20% if possible). One also has to rely on smaller vertical emittance: 23nm at IP and 18nm extracted from DR, with 5nm left for LET emittance dilution, which is tight but may be feasible. Advantages -- extraction which may actually work, reduced beamstrahlung, less incoherent and much less of coherent pairs, etc. Two sets of 1TeV High Luminosity parameters were suggested, with luminosity of 5.7E34 (twice the nominal 1TeV luminosity) and 4.6E34 (factor of 1.6 of the nominal 1TeV luminosity). The latter does not rely on increased beam charge. These sets need to be discussed.
Updated DID fields for SiD, LDC, GLD:
Andrei and Brett presented field shapes for the Detector Integrated Dipole for SiD, LDC and GLD detectors. The files with the field [z(m), BzSolenoid(T), BxDID(T)] are posted (see links on the left).
Andrei Seryi, 07/26/05