BDS Webex mtg, Dec 3 2008, devoted to g-g parameters for IP, possible staging,
and laser and FEL configuration optimization.
Present:
Valery Telnov, Jeff Gronberg, Deepa Angal-Kalinin, Michael Peskin, Tim Barklow,
Takashi Maruyama, Lew Keller, Ken Moffeit, Cherrill Spencer, John Amann,
Yuri Nosochkov, Andrei Seryi
Motivation:
--The need to define steps for the work on gg IR design planned by GDE and BDS group
--To proceed with IR design, a coherent set of parameters is needed
--The recently suggested low E first gg stage need to be looked at consistently
Discussed:
--The layout slides, with possible explanation of stages,
and the tentative parameters table of the stages
The layouts and parameters are posted here:
http://ilcagenda.linearcollider.org/conferenceDisplay.py?confId=3170
The stages discussed are:
1st: gg 180GeV CM, energy reach ~128GeV
– single DR (always assume 3km perimeter)
– short ~0.3km/side BDS
– site length ~8.8km
2nd: or 3rd: gg 180 GeV CM
– twice Lumi with faster kicker or second DR
4th: e+e- 230 GeV CM
– add e+ source
– lengthen BDS (~0.8km/side) add dedicated collimation
– site length ~12.1km
5th: e+e- 500GeV CM
– lengthen BDS to 1TeV CM layout (~2.2km/side)
– site length ~27.2km
6th: gg 500GeV CM, energy reach ~400 GeV
– lower DR x-emittance four times
– final run before (multi)-TeV energy upgrade
The Luminosity of stages and tentative length of physics
program suggested for discussion was:
1: L~0.25E34, ~2 years
2 or 3: L~0.5E34, ~2 years
4: L~0.9E34, ~3 years
5: L~2E34, ~5 years
6: ~4.5E34, ~2 years
Some of the comments on parameters:
For the first stage, the 180GeV CM was selected (instead of 160GeV
considered earlier), in order to provide an acceptable disruption angle
of the electrons after Compton conversion.
Questions raised in the discussion:
--Why 128GeV energy reach is needed, if Higgs mass assumed 120GeV?
Answer: to scan over the peak and have some margin.
--What is the initial polarization of e-? Answer ~85%.
--What can be done with L~0.25E34 of the first stage?
Answer: Valery's estimation is that the Higgs width could
be measured to ~8% accuracy over 2/3 years.
The physics program of the first stage is however longer.
Evaluation to be continued.
--Discussed FEL and Laser as a driver. The feeling is that FEL
can be built now but may be somewhat more expensive than the laser.
Laser require R&D (which is ongoing). More details will be provided.
--Question was asked why more aggressive x-emittance cannot be
obtained in earlier stages? Answer: need to discuss with DR colleagues.
--Discussed the need to understand the overall schedule of the project,
how such first stages could fit into the overall program.
Next steps & who is responsible:
--Discuss with DR colleagues about lower e_x -- A.S.
--Discuss with Peter G. about overall schedule -- A.S.
--Discuss with FEL experts -- A.S.
--Get more details on Laser and make CAIN simulations -- J.G.
--Make detailed simulations for parameter table -- V.T.
--Follow with physics program evaluation -- T.B., M.P.
