May 22, 2008 TJRMICE Beamline Collimation and Correction 1 Tom Roberts Carol Johnstone Muons, Inc.

May 22, 2008 TJRMICE Beamline Collimation and Correction 2 Pion Segment Before D1, the beam contains all momenta and is purely aperture limited. There is little or nothing to be gained by putting either collimators or trim magnets in the pion segment. –The whole point is to maximize muon production, and basic geometry will do that –While collimators could be used to reduce intensity when necessary, it is much better to do that by adjusting the target. If they were installed, there’s no way to tune them – monitors are not useful until collimators or apertures define the momentum and transverse emittance.

May 22, 2008 TJRMICE Beamline Collimation and Correction 3 Muon Segment Collimators Collimation to limit momentum spread –Should be at a momentum-dispersed focus –Only possibility is midway between Q6 and Q7 Collimation to limit transverse emittance –Ideal: two pairs of H and V collimators separated by an odd-integer of π/2 phase advance Should be at low dispersion –Possible: Vertical collimator should be ahead of Q4 (avoid quad apertures giving a beta-dependent collimation) Horizontal collimator must be ahead of D2 (low dispersion) Only possibility is inside D2 The horizontal dispersion after D2 precludes any transverse- emittance collimation A vertical collimator midway between Q6 and Q7 is appropriate

May 22, 2008 TJRMICE Beamline Collimation and Correction 4 Muon Segment Trims Ideal: –Trims come in pairs separated by some distance, so both position and angle of the beam can be controlled –Trims are placed just after collimators Horizontal Trims –Useless before momentum collimation (just mimics D2) –Between momentum collimator and Q7 –Possibly another between Q9 and Tracker1 Vertical Trims –After each vertical collimator The one between D2 and Q4 may be difficult (access path) Possibly another between Q9 and Tracker1

May 22, 2008 TJRMICE Beamline Collimation and Correction 5 Current thinking, based on optics H and V Collimators (inside D2) V Trim (if possible) H and V Collimators H and V Trims H and V Trims (if possible)

May 22, 2008 TJRMICE Beamline Collimation and Correction 6 Next Steps Pair of collimators inside D2 –Determine detailed requirements –Mechanical design Pair of collimators between Q6 and Q7 –Consider interaction with beam stop, shielding, and quads –Look for existing units Pair of trims between collimators and Q7 –Consider interaction with beam stop, shielding, and quads –Look for existing magnets Other suggested components: –Check MICE drawings to consider possibilities Put these new elements into G4beamline and investigate their performance.