C. Rogers, ASTeC Intense Beams Group Rutherford Appleton Laboratory MICE Descope - Options C. Rogers, ASTeC Intense Beams Group Rutherford Appleton Laboratory

MICE Descope

MICE Descope Options SS2 in downstream, no SS1 Measurement can be a difference measurement, i.e. absorber in vs absorber out Upstream diagnostics for beam sampling or to control systematic due to instability in input beam SS2 in upstream, no SS1 Tracker straight tracks for x, x', y, y' EMR range for pz TOF12 augments downstream PID and downstream pz Use SS1 and SS2 Largely ruled out on grounds of risk Should establish existence of viable optics

SS2 in downstream Questions Can we find a viable optics to match to FCU? ? Can we reconstruct well enough in the Quads+diffuser OR do a difference (absorber in vs out) measurement? Durga

SS2 in upstream Questions Can we get sufficient downstream detector performance? Rogers/Francois Does the beam scrape too much in TKD? Rogers

SS2 in upstream Questions Can we get a reasonable optics? Is the risk of further issues with SS1 too great?

Timescales Decision point is 27th May Need to have main physics inputs ~ 20th May Would like to see some convergence by ~ 13th May

C. Rogers, ASTeC Intense Beams Group Rutherford Appleton Laboratory SS2 Upstream Option C. Rogers, ASTeC Intense Beams Group Rutherford Appleton Laboratory

SS2 in upstream position

Revised TKD In primary absorber coordinate system: Secondary absorber z = 1938 to 1976 mm Stations at z = 2000, 2100, 2200 mm Is more space needed (e.g. radiation shutters? He window?) 100 mm station spacing 500 micron spatial resolution 5 mrad scattering * 100 mm => 500 micron width for projected scattering distribution x' resolution ~ 5 mrad * sqrt(2) = ~7 mrad Straight tracks => 2 stations to make a straight track, 3rd station for redundancy/noise rejection Is this sufficient redundancy? Nb stations downstream see more scattering due to upstream stations How much RF noise? Do we need extra shielding? Use TOF2 and especially EMR for noise rejection Very clear time resolved tracks in EMR...

Energy straggling in TOF2 F. Drielsma F. Drielsma Energy straggling through TOF2 makes noise on pz measurement in EMR Gives ~ 1.4 MeV/c RMS for pz > 150 MeV/c Gives ~ 2-4 MeV/c RMS for pz in range 100 – 150 MeV/c One could remove TOF2; but energy straggling is not so big and it provides a nice redundancy/validation

Energy straggling in KL F. Drielsma F. Drielsma Energy straggling through KL makes noise on pz measurement in EMR Gives ~ 4.1 MeV/c RMS for pz > 150 MeV/c Plan to use KL to characterise the beam Consider KL-less arrangement for measurements which require improved pz resolution

Pz Reconstruction in EMR F. Drielsma F. Drielsma Pz reconstruction width < 2 % for pz > 100 MeV/c Compares well with tracker pz resolution at 4 T

Optics Using modified version of 200 MeV/c Demo lattice RF RF TKD SA FC PA FC SA Using modified version of 200 MeV/c Demo lattice Remove SSD, keep currents/etc same Nb some residual field in TKD Can certainly optimise e.g. FCD Asymmetry in the lattice optics Could recover a bit by tweaking FC optics RMS beam radius < 80 mm in TKD region

Optics Radial distribution at TKD 93 % of beam is transported to TKD 85 % of beam is transported through TKD fiducial cut Again, could tweak the FC to move the focus back a bit

Emittance Reduction Descope Baseline RF RF TKD TKD SA FC PA FC SA Descope Baseline See expected good emittance reduction in upstream region No longer see emittance reduction in downstream secondary absorber Beta is too high here?

Amplitude change Descope Baseline Number of muons in each amplitude bin Green – upstream Blue - downstream

Ratio Descope Baseline Histogram Consider the number of muons in each amplitude bin, n Histogram is n(downstream)/n(upstream) Line Consider the number of muons with amplitude <= bin edge, N Line is N(downstream)/N(upstream)

Effect of tracker radius No radius cut Radius cut Tracker radius has little effect on core emittance reduction Line has very similar trajectory

ToDo Reoptimise focus coil to move focus downstream Does this “break” the lattice/cell argument? Full resolution analysis/emittance calculation Doing combined detector fit? Etc.