Crab cavity location for 2-mrad x-ing December 7, 2004 A.S.

Motivation In 2-mrad x-ing probably cannot install crab cavity in FD, because of its transverse size Try to place crab cavity in FF, far from FD For the moment, use NLC beamline and beam parameters, since it was easier to make a quick look

Place crab cavity near QF5 This may be not the best location, since there is dispersion & higher order terms here, but this is just a test NLC optics and nominal beam parameters were used in this test: 250 GeV/beam,  x0 =243nm,  y0 =3nm,  x *=8mm,  y *=0.11mm,  z =0.11mm. Energy spread: Batman distribution with 0.8% full width.

half_cross_angle = 10.0e-3; crab cavity effect not removed:  x /  x0 =  y /  y0 = For crab-cavity near QF5 and half_cross_angle = 10.0e-3; need kick with dangle/dz = e-4 1/m For comparison, for crab cavity 12m from the IP need dangle/dz = e-4 1/m Crab-cavity modeled as a thin element which produce z-x’ kick, including the energy dependence of the kick

half_cross_angle = 10.0e-3;  x /  x0 =  y /  y0 = Do no see any degradation of the beam size

Start to see effect on the beam size when the crossing angle ~50 mrad Half_cross_angle = 0.1  x /  x0 =  y /  y0 =

With 2mrad considered, this simple study show that it should be feasible to place crab-cavity in FF, far from FD. For  z =0.3mm ILC beam the effect may be larger, but even if so, the margin seems to be sufficient Still, location of crab cavity in FF need to be optimized (near QF9?). Also need to consider ILC optics and parameters (may be even easier, smaller energy spread), and any other implications. NLC optics and nominal beam parameters were used in this test: 250 GeV/beam,  x0 =243nm,  y0 =3nm,  x *=8mm,  y *=0.11mm,  z =0.11mm. Energy spread: Batman distribution with 0.8% full width.