Critical Issues for MICE Chris Rogers MICE CM 15

Aim Aim is to suggest ways MICE can fail Look with a critical eye at all MICE systems From an Analysis/emittance measurement standpoint A personal view of the associated risk/impact Dependent on my knowledge of the subsystem Incomplete by definition

What can go wrong? Detectors Detectors are insufficiently calibrated Detectors have insufficient resolution PID accuracy is insufficient Event rates issues Apertures are too small Beam Beamline doesn’t fill phase space/match adequately/consistently Beamline is too impure Event rates issues Analysis/Optics Beam heating is dominated by optics Beam weighting is too difficult Systematics reduction is too difficult

Detectors

TOF Resolution Required to measure bunch length ~ 0.5 ns RMS from RF Bucket size For 1e-3 emittance measurement resolution of TOF should be <14%*0.5 ns ~ 70 ps At tracker reference plane Vs RF zero crossing Including materials effects and tracker energy resolution between TOF and tracker Diffuser between TOF I and upstream tracker Is this possible? Requirement/consideration also needed for correlations Between t and x,y,px,py,pz

Tracker Resolution Pz resolution of tracker should be ~ 2.5 MeV Marginal at low Pt Contingency - weaken the tracker field? Serious knock on for optics & beamline Tracker field TRD says 4T/240, 4T/200, 3.4T/170, 2.8T/140 Is this the final word? Knock on for optics & beamline Requires some planning to change these values Light loss RF Background

Detector Calibration (Hardware) Requirement For 1e-3 emittance measurement detectors must be calibrated to 10% of RMS Example Tracker must be aligned to ~ 10% * 2 MeV/c ~ 0.2 MeV/c 0.2 MeV/c ~ 1 mrad * 200 MeV/c This is comparable to solenoid distortion (!) Example Timing measurement must be calibrated to 7 ps At the tracker reference plane Including materials effects and tracker p z I have not seen a full demonstration/plan for this calibration accuracy either for Tracker or TOF The 10% requirement is historical and may need to be updated

Vessel & Support FEA Results (S. Virostek LBNL CM13) 50 ton, uniform axial load on vessel; fully fixed at support stand base Max deflection: 1mm

Detector Aperture Scraping is a significant effect if we want to predict the number of muons in a nufact acceptance Beta-tapering means scraping continues down the beamline First order? We should measure it But it is unlikely that we will be able to measure the full acceptance of the cooling cell

PID Resolution PID looks capable of achieving <1e-3 impurity downstream I have no feel for upstream detectors Depends on a high purity muon beam Impurity/efficiency requirements ignore position of mis-pid in the beam Mis-pid at high “emittance” will bias the measurement more

Beam

Beam Matching Cooling is dependent on a well-matched beam A direct measurement of cooling with minimal beam weighting is highly desirable Much stronger argument Challenging conditions to work under Quadrupoles, material, scraping, high emittances Worry about RMS’s and mean Matched beams below 6  are high risk No/thin diffuser removes a d.o.f. from the optics Requirement for tight focussing is looking highly challenging Collimation will leave a nasty beam, more susceptible to emittance growth

Beam Purity Given uncertainties in the beamline, beam purity is also uncertain Although indications are it should be quite good If the upstream PID is not so good this will become important

Event Rate Number of  /sec depends on several potential limiting factors Number of protons on target Number of  /proton on target Max rate at TOF 0 / Ckov I  efficiency from TOF 0, Ckov I to tracker Max rate at tracker 600  => 250 good  => Issues How far can we dip into ISIS? How efficient is the beamline matching section With collimators for low emittance Assuming the 600 vs 250  at tracker resolved?

Analysis/Optics

Optical heating Optical heating/cooling is a serious effect If we are to claim cooling, we have to understand it to the 1e-3 level This is poorly understood at present Transverse Transverse heating can be countered by selecting different beta functions for the beam at different momenta Longitudinal Longitudinal heating tends to be worse as there is no longitudinal focussing (RF at 90 o ) Even with RF at 40 o significant heating in the gap between the TRP and the linac

Beam Weighting Beam weighting in a 6D phase space is not easy problem Working in 6D In the presence of detector errors Amplitude Momentum correlation? Momentum dependent beta function? Required for both bunch emittance and single particle emittance analyses Important if beamline fails to deliver matched beam

Cooling Channel Measurements Measuring B-fields and LH 2 looks okay RF measurement looks hard No obvious strategy Particle-based measurements will be difficult Run the RF Compare with tracking code? This will be used to calibrate the measurement But not needed directly for the emittance measurement

Systematics Reduction Emittance Measurement Take calibration Feed it into G4MICE Use it to predict systematic error on experiment from detector resolution What constraints/requirements does this place on G4MICE? Accuracy of tracking Accuracy of physics processes e.g. MuScat in the SciFi Accuracy of geometric model e.g. material between TOF and SciFi Accuracy of digitisation For TOF

Personal View - Risk Analysis (1) IssueRiskImpactRemedy/Comment Tracker CalibrationMedHighTracker group -> how accurate is the calibration? Timing CalibrationHighMedCan we accurately measure time at the TRP? Transverse Resolution LowHighokay Longitudinal resolution HighMedLongitudinal emittance resolution will probably be poor PID resolutionMed No clue about upstream PID RateMedLowRun for longer AperturesHighLowAccept poor PID in scraping region? Beamline matchHighMedMore manpower in beamline or beam weighting Beamline purityLowMedMore manpower in beamline

Personal View - Risk Analysis (2) IssueRiskImpactRemedy/Comment Transverse beam heating MedHighStudy non-linear dynamics of cooling channel Longitudinal beam heating HighMedStudy non-linear dynamics of cooling channel Showing 6D cooling looks difficult at present Beam weightingMedHighCrucial if the beamline is poorly matched Channel calibrationMed Demonstrate a method for measuring RF Resolution Red.Med Need constraints on G4MICE accuracy