Transcript Beam Line Design & Status - International Muon Ionization

MICE Beamline Analysis
JUNE04
Including a proposal for a JUNE04A
Configuration
Update – August 03, 2004 (new slides at end)
Tom Roberts
Illinois Institute of Technology
TJR August 2, 2004
MICE Beamline Analysis
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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
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JUNE04 Layout
ISIS
Bea
m
TOF0
TOF1
Ckov1
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Diffuser
Iron
Shield
TOF2
Ckov
2Cal
3
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
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Observations on overall beam distributions, JUNE04
☺
Average Momentum After Diffuser: 250MeV/c => ~ 236.5MeV/c
Good for Amplitude
vs p correlation
Narrow-momentum (+/-1% ~ 236.5MeV/c): Beam OK
☺
Narrow-momentum
Beam OK
   yRMS / y'RMS  0.40 m
  RMS  ( ) yRMS y'RMS  6.1 mm rad
Narrow momentum
region
yy' 6pi & well matched
xx' larger distribution
(improvable with quad optics)
Overall beam distribution: Suffers from a few aberrations

Full beam
Still needs
attention
Peak Momentum
> 236.5MeV/c !
TJR August 2, 2004
236.5MeV/c
yy' ≥10pi & not well
matched
xx' large distribution,
<x> ≠ 0 & not well matched
MICE Beamline Analysis
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Suggested Improvements
 Raise the pion momentum in the beamline
o improve π/μ separation in B2
o Reduce TOF0 singles by eliminating πs
o Slight increase in pion production
 Move TOF0 downstream of Q5, or downstream of Q6
o Reduce TOF0 singles
o Reduce effect of multiple scattering in TOF0
o 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 TOF0
o Perhaps also DFD in Q7-9
o 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
TJR August 2, 2004
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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 elements
B. Target heating
C. Singles in TOF0
D. 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.
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Proposed JUNE04A Layout
Pπ =
425
MeV/c
Moved,
Thinner,
TOF0
TJR August 2, 2004
Moved,
Thinner,
TOF1
MICE Beamline Analysis
New
Iron
Shiel
d
(TOF1 and its
iron shield are
symmetrical with
TOF2, except for
the Diffuser)
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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.
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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
•
•
•
•
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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)
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Estimated TOF and Tracker Resolutions
• 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.
• The resolution in Pz depends
strongly on Pperp, and is given
in Fig 3.9 of the proposal; it is
modeled here:
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JUNE04A π/μ/e Discrimination, with Estimated
Gaussian Resolutions in Pperp, Pz, and TOF
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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)
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Comment on MICE Targeting
Current Baseline
Possible Change
ISIS
Beam
ISIS
Beam
Ti
1 mm wide,
10 mm thick,
variable depth
•
•
•
•
•
10 mm wide,
1 mm thick,
variable depth
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.
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Comparison of 1mm and 10mm Target
Thicknesses
Multiple Scattering
Energy Loss
• 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.
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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
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TOF1-TOF2, TOF0 after Q6, TOF1 after Q8
NOTE:
There is 1 pi+
event that is
close to the
mu+ band.
This is NOT
a pi+ decay
(decays are
disabled).
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TOF1-TOF2, Comparison
JUNE04A (except TOF1 position)
TOF1 after Q8
No Upstream Iron Shield
TOF1 after Q9
With Upstream Iron Shield
Note the different time scales (y axis)
σ(Pperp) = 0.12 MeV/c (should be 3 MeV/c – see below)
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TOF1-TOF0, 290 < Ptot(meas) < 300 MeV/c
σ(Pperp) = 0.12 MeV/c (should be 3 MeV/c – see below)
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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.
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Evaluation Matrix - 1
TOF0 located after the Quad in the column heading.
TOF1 located between Q8 and Q9.
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
JUNE04A value (TOF1 moved after Q9, add upstream Iron Shield):
6.5
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Evaluation Matrix - 2
TOF0 located after the Quad in the column heading.
TOF1 located between Q8 and Q9.
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
JUNE04A values (TOF1 moved after Q9, add upstream Iron Shield):
TOF0 singles: 3831 good-mu: 591
TJR August 2, 2004
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