tom roberts illinois institute of technology

TJR August 2, 2004 MICE Beamline Analysis 1

MICE Beamline AnalysisJUNE04

Including a proposal for a JUNE04A Configuration

Update – August 03, 2004 (new slides at end)

Tom Roberts

Illinois Institute of Technology


JUNE04 Beamline Design

• Same basic physical layout as MAR04, with minor changes (e.g. downstream iron shield)

• Corrects many deficiencies of earlier designs• JUNE04 still has problems:

– Beam distributions are not all as desired (see below)– TOF0 singles rate is ~10 MHz– Good mu+ rate is less than half of the desired 600 ev/sec

• This talk discusses my analysis of a number of suggestions to address these problems.

• I propose a JUNE04A design that both reduces the TOF0 singles rate and increases the good mu+ rate


JUNE04 Layout

TOF0 TOF1

Ckov1

IronShield

TOF2Ckov2

Cal

ISISBeam

Diffuser


JUNE04 Beamline Design – Properties

Attribute Value

pion momentum 350 MeV/c

muon momentum 250 MeV/c

Diffuser Thickness (Pb) 8 mm

Design emittance after Diffuser,

for 1% Δp/p

y-y’ 6 π mm-rad

x-x’ >10 π mm-rad

g4bl/ecalc9f emittance after Diffuser,

full momentum interval

14.8 π mm-rad

Good mu+ rate 261 ev/sec (correction)

TOF0 Singles 9.9 MHz


Observations on overall beam distributions, JUNE04Average Momentum After Diffuser: 250MeV/c => ~ 236.5MeV/c

Narrow-momentum (+/-1% ~ 236.5MeV/c): Beam OK

myy RMSRMS 40.0'/ radmmyy RMSRMSRMS 1.6')(

myy RMSRMS 40.0'/ radmmyy RMSRMSRMS 1.6')(

yy' 6pi & well matchedxx' larger distribution

(improvable with quad optics)

236.5MeV/cPeak Momentum > 236.5MeV/c !

☺

yy' ≥10pi & not well matched

xx' large distribution, <x> ≠ 0 & not well matched

Good for Amplitude vs p correlation

Overall beam distribution: Suffers from a few aberrations

Narrow-momentum Beam OK

Full beam Still needs attention

☺

Narrow momentum region


Suggested Improvements Raise the pion momentum in the beamline

o improve π/μ separation in B2o Reduce TOF0 singles by eliminating πso Slight increase in pion production

Move TOF0 downstream of Q5, or downstream of Q6o Reduce TOF0 singleso Reduce effect of multiple scattering in TOF0o Requires moving TOF1 downstream of Q9, and an analysis that the

pi/mu discrimination is still OK (below) Use thinner counters for TOF0 and TOF1

o Reduce effect of multiple scattering in TOF0 and TOF1- Consider changing the tune from FDF in Q4-6 to DFD

o Steer more pions into the Q4 iron, and away from TOF0o Perhaps also DFD in Q7-9o May be able to better balance the vertical and horizontal emittances

(better horizontal aperture control of the beam?)

Included in this analysis and proposal for JUNE04A


Evaluation Criteria• At present we don’t know the targeting parameters we will achieve,

and basically must make an educated guess of what the overall rates will be.

• In practice, the target will have an adjustable insertion depth into the ISIS beam, and we will insert it until we are limited by one of the following:

A. ISIS beam losses / activation of beamline elementsB. Target heatingC. Singles in TOF0D. Tracker or DAQ event rate capacity

• The beamline design and tune cannot affect A, B, or D, and can only hope to optimize the good mu+ rate relative to TOF0 singles.

The criteria I have used is to maximize the good-μ+ rate and to minimize TOF0/good-μ+, both for a given set of 10M target π+.

Remarkably, these two criteria are compatible.


Proposed JUNE04A Layout

Moved, Thinner,

TOF0

NewIron

Shield

(TOF1 and its iron shield are

symmetrical with TOF2, except for

the Diffuser)

Pπ = 425

MeV/c

Moved, Thinner,

TOF1


Comparison of JUNE04 and Proposed JUNE04A

Attribute JUNE04 JUNE04A

π momentum (B1) 350 MeV/c 425 MeV/c

μ momentum (B2) 250 MeV/c 250 MeV/c

TOF0 position Downstream of Q4 Downstream of Q6

TOF1 Position Downstream of Q8 Downstream of Q9

TOF total thickness 2 inches 1 inch

Upstream iron shield None Same as downstream

TOF0 to TOF1 distance 8.5 meters 7.8 meters [1]

TOF0 Singles 9.9 MHz 3.8 MHz

Good μ+ rate 261 ev/sec (correction) 591 ev/sec (correction)

Design Emittance 6 π mm-rad [2] 6 π mm-rad [2]

g4bl/ecalc9f emittance 14.8 π mm-rad 11.9 π mm-rad

[1] π/μ/e discrimination in TOF1-TOF0 presented below.[2] Narrow-momentum beam, no multiple-scattering from TOF0 and TOF1,

horizontal emittance much larger. Reasonably consistent with ecalc9 value.


JUNE04A π/μ/e Discrimination in TOF1-TOF0

• A major change in the JUNE04A design is the reduction in distance between TOF0 and TOF1, so we must verify that π+ can still be cleanly separated from μ+

• There are no protons – TOF0 stops >99% of them in this momentum range

• Using Tracker1 to measure Ptot, the perfect-resolution graph looks fine:

Perfect TOF and Tracker Resolution

• A Q4-filling Gaussian beam with equal numbers of π+, μ+ and e+

• No correction for Eloss in the

Diffuser• GoodParticle = TOF0 & TOF1 &

Tracker1• Still present:

– Variations in path length– Variations in Eloss (Diffuser)


Estimated TOF and Tracker Resolutions

• The resolution in Pz depends

strongly on Pperp, and is given

in Fig 3.9 of the proposal; it is modeled here:

• From the proposal, TOF0 and TOF1 are estimated to have resolutions of 50 ps, giving a resolution of 70.7 ps for TOF1-TOF0.

• From the proposal, Tracker1 is estimated to have a resolution in Pperp of 0.12 MeV/c.


JUNE04A π/μ/e Discrimination, with Estimated Gaussian Resolutions in Pperp, Pz, and TOF


Conclusions about JUNE04A

• Straightforward modifications to JUNE04 provide significant improvements in performance:– TOF0 singles reduced by a factor of ~2.5– Good μ+ rate increased by a factor of ~1.5– Input emittance slightly reduced

• The reduction in TOF0 to TOF1 distance is OK – we still have good π/μ/e discrimination

• Reducing TOF0 and TOF1 to 1 inch total thickness improves the rate of good μ+

• Still need a design iteration:– Improve horizontal distributions– Correct the overall emittance– Tune the Decay Solenoid field (better π focusing and separation

from μ)


Comment on MICE Targeting

Ti

1 mm wide, 10 mm thick,

variable depth

10 mm wide, 1 mm thick,

variable depth

Current Baseline Possible Change

• There clearly is a multiple-scattering angle, and an energy loss, below which protons intersecting the target will not be lost.

• Because of this, it may be appropriate to rotate the target 90 degrees, so it is 10 mm wide and 1mm in length.

• While ~10 times more protons will intersect the target, perhaps only those that strongly interact will be lost.

• With everything else equal, we will adjust the depth so the number of strongly-interacting protons will be the same, independent of orientation.

• This might reduce ISIS losses, while not significantly affecting either the target heating or the MICE muon rates.

ISISBeam

ISISBeam


Comparison of 1mm and 10mm Target Thicknesses

• Clearly the 1mm-thick orientation has much less impact on individual ISIS protons than does the 10mm-thick orientation.

• Evaluating whether or not this target rotation will reduce ISIS losses requires an analysis using the ISIS beam properties and lattice.

Multiple Scattering Energy Loss


Update August 03, 2004• I was asked to provide three updates:

– An analysis of TOF1-TOF0 pi/mu separation, moving just TOF0 (i.e. TOF1 remains between Q8 and Q9), fixing the resolution in Pperp.

– A histogram of TOF1-TOF0 timing for a narrow momentum cut.– The evaluation matrix I used to determine the basic features of

JUNE04A

• In the process, I discovered two errors in the original presentation – both had the effect of making JUNE04A look like less of an improvement that it really is:– For JUNE04 ev/sec, I transcribed (excel=>powerpoint) the momentum

(350) instead of the ev/sec (261)– I used the selected entry in my evaluation matrix for JUNE04A, rather

than the correct JUNE04A – the matrix had TOF1 between Q8 and Q9 (note the TOF1-TOF2 analysis had TOF1 located correctly, after Q9)

– I have made the corrections above, highlighted in red


TOF1-TOF2, TOF0 after Q6, TOF1 after Q8

NOTE:There is 1 pi+event that isclose to themu+ band.This is NOTa pi+ decay(decays aredisabled).


TOF1-TOF2, ComparisonJUNE04A (except TOF1 position)

TOF1 after Q8No Upstream Iron Shield

TOF1 after Q9With Upstream Iron Shield

Note the different time scales (y axis)

σ(Pperp) = 0.12 MeV/c (should be 3 MeV/c – see below)


TOF1-TOF0, 290 < Ptot(meas) < 300 MeV/c

σ(Pperp) = 0.12 MeV/c (should be 3 MeV/c – see below)


TOF1-TOF2, Comparison of σ(Pperp) values

JUNE04A (except TOF1 between Q8 and Q9)σ(Pperp) = 0.12 MeV/c σ(Pperp) = 3.0 MeV/c

Note: for σ=3.0 there are a few more pi and mu in “no-man’s land”.I’m a bit surprised there was so little change in the plot.


Evaluation Matrix - 1TOF0 located after the Quad in the column heading.

TOF1 located between Q8 and Q9.

JUNE04A value (TOF1 moved after Q9, add upstream Iron Shield): 6.5

Decision Criterion

Ratio, TOF0 singles / Good mu+ -- 2 inch TOFs

Ppi Q4 Q5 Q6

350 38.2 32.0 22.5

400 34.8 28.1 10.3

425 17.6 14.3 8.8

Ratio, TOF0 singles / Good mu+ -- 1 inch TOFs

350 29.3 24.6 17.9

400 25.7 19.4 7.8

425 13.8 11.1 7.5


Evaluation Matrix - 2

Normalized rates, ev/sec or singles in kHz

TOF0 Singles, 2" TOFs Good mu+, 2" TOFs

Ppi Q4 Q5 Q6 Ppi Q4 Q5 Q6

350 9963 7856 7137 350 261 245 317

400 11773 8057 4356 400 338 287 423

425 6215 4498 3831 425 352 315 437

TOF0 Singles, 1" TOFs Good mu+, 1" TOFs

Ppi Q4 Q5 Q6 Ppi Q4 Q5 Q6

350 9945 7851 7138 350 340 319 398

400 11761 8053 4357 400 457 414 562

425 6202 4498 3831 425 449 406 512

TOF0 located after the Quad in the column heading.TOF1 located between Q8 and Q9.

JUNE04A values (TOF1 moved after Q9, add upstream Iron Shield):TOF0 singles: 3831 good-mu: 591

tom roberts illinois institute of technology

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