Agenda and Summary:

 1) Linac and BDS simulation with GM model K and feedbacks -- Linda Hendrickson
 2) Scenarios of upgrade from single 14mrad IR to two IRs -- Andrei Seryi
 3) Civil layouts for single 14mrad IR and upgrades to two IRs -- Fred Asiri
 4) Simulations of errant beams in BDS -- Lew Keller
 

Linac and BDS simulation with GM model K and feedbacks :

Linda presented results of simulations of 5Hz feedbacks, which included the linac, BDS and IP feedbacks. The K-model (KEK-model) for ground motion (noisy site) was used and the component jitter (25nm in BDS and 50nm in linac), energy, current, and kicker jitter were included. Several issues need further studies -- e.g. the beam size growth in BDS is rather sensitive to the additional energy spread. The beam jitter was found to be:
                                        All included:            Only ground motion:
    End Linac e- average:    X: 0.03    Y: 0.70        X: 0.01    Y: 0.3
    IP e- average:                X: 0.28    Y: 12.5        X: 0.12    Y: 3.4
    IP avg 2beam diff:          X: 0.33    Y: 15.8        X: 0.17    Y: 3.7
    IP maximum 2beam        X: 1.57    Y: 49.0        X: 0.72    Y: 15.9
    difference:                   (777 nm) (197 nm)
For this noisy ground motion model, the luminosity is only about 70% even with an ideal intratrain feedback.

Scenarios of upgrade from single 14mrad IR to two IRs :

Andrei presented very preliminary scenarios for upgrade of single IR to two IRs with. The assumed single IR baseline with 14mrad can be upgraded to
    A) 14mrad and small angle, min separation between detector;
    B) 14mrad and small angle, larger separation between detectors;
    C) 14mrad and 20mrad (or more) large separation between detectors, OK for gamma-gamma;
The baseline BDS has "stubs" in the tunnel, which help to start building the tunnels for the second IR.

Civil layouts for single 14mrad IR and upgrades to two IRs :

Fred continued discussion of the previous topic and presented civil construction models for single IR upgraded to two IRs. Fred estimated the minimal distance from the IP to the BDS branching point to be
    A) 1.8km with 14m and 13m diameter detectors with only 1m gap between detectors;
    B) 2.3km --//-- with 5m gap between detectors for shielding; 
The 3D models for these cases are being developed.
 

Simulations of errant beams in BDS :

Lew performed studies of several errant beam scenarios in ILC BDS. TRANSPORT was used for optics, and EGS4 for simulation of energy deposition. Lew considered cases when a quad would be moved by a mm in betatron collimation, causing the beam to hit the beampipe hundred meters downstream, and when the bends B1,B2,B5 would be set to a wrong value causing the beam to hit the protection collimator in front of the final doublet. The errant beam in the betatron collimation region would typically cause hundred degrees C temperature rise per bunch, for stainless steel vacuum chamber. The small grazing angle (~400urad) helps in this case. For the final doublet, the grazing angle is even smaller (~76urad) and the beam is distributed over longer distance in z. The temperature rise is just fraction of a degree. Studying the energy deposition in SC coil of QF1 versus the thickness of protection collimator, one can see that the protection collimator does not prevent the quench of QF1 and can actually increase energy deposition in QF1.

Andrei Seryi, 10/13/05