1) Downstream diagnostics in 2 and 20mrad extraction - K.Moffeit
2) Update on power needs for extraction line magnets - C.Spencer
3) Radiation studies on the BDIR, etc - N.Mokhov, N.Nakao
4) Parameters optimization for crossing angle - P.Raimondi, M.Pivi, A.Seryi
Ken presented results of evaluation of diagnostics in extraction line for 20
and 2mrad IR. It looks that
-- precision of 0.25% for polarization can be achieved in both designs;
-- losses are ~2e-4 in 2mrad and ~1e-7 in 20mrad;
-- Compton IP luminosity is ~3times higher for 20mrad ;
-- There is background from secondaries in 2mrad, but signal/noise seems sufficient;
-- Beam energy loss due to SR is 110MeV in 20mrad and 850MeV in 2mrad;
-- Due to horizontal bends, distribution of SR in Cherenkov detector is more favorable in 2mrad;
-- A collimator is needed in 20mrad to protect the Cherenkov detector;
Evaluation of diagnostics at 500GeV/beam was not done, but certainly would represent larger challenge in 2mrad due to increased SR losses.
Cherrill presented results of design bend magnets for 2mrad extraction line (see Excel file). At 1TeV CM these bends would take 14MW per beamline (28MW total for e+ and e-). For comparison, the bends in 20mrad extraction take 1.2MW per beamline. This certainly warrants studies of possible improvements, such as to consider use of HTS magnets.
Nikolai Mokhov, Noriaki Nakao and Sergei Striganov presented results of
ongoing Radiation studies at Fermilab for BDS and also studies for Linac and
Described studies include machine induced background in BDS, residual activity in beam dump, performance studies of extraction beamlines, etc.
A bent crystal experiment has been suggested for ATF to improve IP background in ATF2 (important for Shintake monitor).
Radiation in linac cryomodule was studied, the source need further clarification.
Shielding for NIU facility is under design.
One of the action items for BDS design is distribute information about radiation levels in BDS to Magnet and other technical groups.
Pantaleo, Mauro and Andrei discussed possibilities to optimize ILC parameters
if crossing angle is taken as advantage. This is inspired by new parameter set
suggested by P.Raimondi for Super-B factory, where crossing angle, combined with
crabbed waist allow to focus beam to very small size and reduce beam-beam
induced emittance growth to 1E-3 per collision, resulting in luminosity of
Reoptimization of ILC parameters for crossing angle case seem to be possible, and about the same luminosity can be achieved, with the same or better luminosity spectrum, even without crab cavity compensation. Several possible parameter sets were discussed.
Reoptimized parameters require tighter focusing in Y (beam size smaller, stability may need to be tighter, etc). Increased betaX (to reduce energy spread) is beneficial since it relaxes the collimation depth which is most tight in horizontal plane.
Andrei Seryi, 06/27/06