Critical Issues for MICE

Chris RogersMICE 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 pz

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 90o) Even with RF at 40o 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 LH2 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)

Issue Risk Impact

Remedy/Comment

Tracker Calibration

Med High Tracker group -> how accurate is the calibration?

Timing Calibration

High Med Can we accurately measure time at the TRP?

Transverse Resolution

Low High okay

Longitudinal resolution

High Med Longitudinal emittance resolution will probably be poor

PID resolution Med Med No clue about upstream PID

Rate Med Low Run for longer

Apertures High Low Accept poor PID in scraping region?

Beamline match High Med More manpower in beamline or beam weighting

Beamline purity Low Med More manpower in beamline

Personal View - Risk Analysis (2)

Issue Risk Impact

Remedy/Comment

Transverse beam heating

Med High Study non-linear dynamics of cooling channel

Longitudinal beam heating

High Med Study non-linear dynamics of cooling channelShowing 6D cooling looks difficult at present

Beam weighting Med High Crucial if the beamline is poorly matched

Channel calibration

Med Med Demonstrate a method for measuring RF

Resolution Red. Med Med Need constraints on G4MICE accuracy