1:30pm-2:00pm, Standard BDS meeting
Agenda: Status Report on the Design and Fabrication of 29 quads for ATF2 -- Cherrill Spencer
2:00pm-3:00pm PST, Phone meeting of WG4 representatives to discuss BCD/ACD
Agenda: Discussion of ranking of BDS configs;
Summary of discussion from ECFA meeting;
Discussion following the GDE recommendations.
In the first part of the meeting, we discussed the status of design and
production of quadrupoles for ATF2. There are 29 quads which are being
built for ATF2 by (IHEP) in Beijing. The specifications for the design,
standards and materials to be used have been discussed and decided upon.
Drawings have been reviewed. Winding of first coils and manufacturing of first
poletips is planned for early December. Assembly will be done in mid December,
followed by quality control with core measured with CMM to check the tolerances.
Magnetic measurements are planned to start in mid-January.
Phone meeting of WG4 representatives devoted to discussion of BDS BCD/ACD.
Deepa Angal-Kalinin, Philippe Goudket - Daresbury, UK
Shigeru Kuroda, Toshiaki Tauchi - KEK, Japan
Hitoshi Yamamoto - Tohoku University, Japan
Brett Parker - BNL, USA
Eric Torrence - University of Oregone, USA
Jerry Aarons, Fred Asiri, Lew Keller, Tom Markiewicz, Takashi Maruyama, Tom Mattison, Ken Moffeit, Yuri Nosochkov, Nan Phinney, Andrei Seryi, Dieter Walz, Lanfa Wang, Mark Woodley - SLAC, USA
One of the questions remaining from previous meeting was whether the
considered IR configurations can work for all parameters. Losses of disrupted
beam in 2mrad extraction line (version August 9, 2005) were presented. Radiative
Bhabhas were not included. Using criteria of loss in Final Doublet < 10W,
preliminary look suggests that the 2mrad version August 9 seems to be fine with
Nominal 500GeV CM
Low Q 500GeV CM (not evaluated)
Large Y 500GeV CM
Low Q 1TeV CM (not evaluated)
Nominal 1TeV CM
And it seems to have problems for
Low P 500GeV CM
High Lum 500GeV
Large Y 1TeV CM
Low P 1TeV CM
High Lum 1TeV CM
High Lum Altern.1 1TeV CM
High Lum Altern.2 1TeV CM
One need to consider a more accurate power density criteria as well.
Simulations of beam losses in 2mrad will be also done by Rob Appleby (disrupted beam and radiative Bhabhas) and will be done by KEK group using Jupiter. Tauchi san have said that losses from pairs in QD0 are below 1W for all cases except 1TeV High Lumi where it is about 2W.
Yuri Nosochkov mentioned that 14/20mrad extraction design works for for all nominal and high-L parameters except for original High Lumi 1TeV (see draft paper for Nanobeam). The Low P options was not specifically studied but will be checked.
Andrei summarized yesterday's phone conversation with Grahame Blair and Tomo
Sanuki, in particular, Grahame's summary of the outcome of ECFA workshop and
discussion of BCD happened at Vienna. The most important was suggestion to
elevate rank of crab-cavity system to rank 1, as it could affect luminosity as
"single point failure". The definition of rank 1 was correspondingly changed, to
include single point failure criteria, and rank 2 items were reviewed.
Correspondingly, both crab-cavity and fast intratrain feedback were elevated to
rank 1. The group is now happy with this ranking.
One of the issues mentioned in Grahame's summary from ECFA workshop is that gamma-gamma is compromised if angle is below 25mrad. This limitation occur, however, for most aggressive gg parameters, which may not be feasible. Also, increase of L* may be needed for gg, which can reduce the angle. It was argued that the optimization need to be done for e+e-.
Tom Markiewicz noted that it was discussed at Vienna that 14/20mr would be rebuilt for gg 25mr. What would it take? White paper states that this is possible. It was argued that it would be difficult to rebuild 14mr to 25mr. The civil group will estimate cost impact of such modification.
Earlier today, results of parasitic beam crossing in head-on scheme were sent by Olivier Napoly. In Olivier's absence, details could not be discussed. For nominal bunch separation, the scheme seem to be just below the instability threshold. For halved bunch spacing the effect will be severe. Results will be cross checked analytically and will be included in feedback simulations by Glen White. Effect of non-point charge will be evaluated (see plot by Lew Keller).
With respect to comments sent earlier by Philip Bambade on polarization
precision vs angle at the IP, Ken Moffeit mentioned that he replied to Philip
and Klaus Moenig that spin angle misalignment of <25mrad (corresponds to angular
alignment ~50 microradians at 250GeV) can be done. Ken also mentioned that Mike
Woods pointed out that earlier studies have the spin angle misalignment and
offset in the horizontal plane. However, the angle at the IP and the spin angle
misalignment is in the vertical. The polarization systematic uncertainties is
less sensitive to the vertical plane than horizontal. Studies need to be
repeated in the vertical plane.
GDE decisions presented at closeout meeting at SLAC on November 18 were summarized and discussed. The group will proceeds with two IR baseline, but should do the work and costing needed to be able to choose a single IR configuration and crossing angle in six month.
With respect to GDE decision on curved linac and straight BDS, Fred Asiri mentioned that conventional facility group assumes +-2.5km as total length of BDS which should be straight. This was agreed to be correct as a first approximation.
With respect to selection in six month of a single IR configuration, Tom Markiewicz suggested that it should be minimum cost, should have small collider hall, sized for one detector, not push-pull, tunnels may have stubs for upgrade. If minimum project cost is approved, adding 2nd collider hall to the project could be considered via project scope increase, as a separate decision. Hitoshi Yamamoto also mentioned that push-pull design meets strong critics in detector community.
In conclusion of the meeting we agreed that ranking of BDS configurations is fine, and we need to plan and proceed with work which will allow us to make an IR configuration choice and evaluate the cost in six month.
Andrei Seryi, 12/01/05