Beamline Commissioning Ideas
Kevin Tilley, CM19
1. ISIS Beam loss, detector calibrations, Particle production
2. Upstream optics commissioning
3. Downstream optics commissioning
Caveats:- the presenter!, These ideas would benefit from more time for consideration!
:
….but a number of people have provided me with some very useful help.
1. Beamloss / Calibration / Particle production:
0. Ascertain acceptable ISIS beam loss / target position.
1a. Calibrate TOF0,1,Ckov1,Trckr? Detectors.
Use basic beamline ie: Q1-Q3off, DecaySolenoid & Q4-Q9 off.
P(B1=B2).
Momentum = Low setting of 50MeV/c for electrons?
(maybe could use quads/sol on? No steering in fact for difft
momenta.
Question: we calibrate against the same thing we will attempt to
measure later??? No – since is different particles? )
1b. Characterise pion production from target versus momentum??
[useful for determining maximum yields and extrapolating to likely
fluxes at MICE?]
Here, uses basic beamline ie just B1=B2 on – to ensure measuring
[production] only & not [ production x beamline transport. ]
For flux of pion-‘s – do bl for 350MeV/c – st out of electron
contamination etc
Note we will only know exact flux at MICE when beamline optics
is finally setup.
2. Upstream beamline optics
Optics. Goal (proposed)= max pion flux at D1, minimum spot size.
On-axis beam.
2. Set B1 for design momentum (expected to be near maximum ~ 444.71)
3. Check basic optics of Q1/2/3 ie. Off/off/on etc & measure intensity
/beamsize /position change at U1. (could fit model ie. eff lengths of Q1Q3 or misalignment of target to optic axis to fit measurement)
Insert study to check if effect of Q1/Q2/Q3 on/off/off easily visible at U1.
4. Fix eg Q1 fixed field. Change(reduce) target dip. Measure vertical
centre changes at U1. Again, could fit model for misalignment of
target/optic axis.
clown Study for misaligned input beam & % chg to (Q1,2,3).
Measurements at U1 /MICE
U1
MICE
Target/optic axis vertical alignment:
Aligned:
Misaligned by 10mm
Normal optic
Nml optic Q123+10% Q123+15%
0
4.8
5.4
5.8
1.2
1.7
1.7
?
5. Set design optics for Q1,2,3 & for Decay Solenoid.
Set momentum (B2=B1)
6. Check basic optics of Decay Solenoid –
eg. phase advance & final beamsize = a nice measurement. Measure
beamsize/position change at D1.
7. Set design optics & optimise.
Aim is:- Ensure decent focus at U1 into solenoid. Aim for highest pion
flux at D1 & smallest spot size. Measure beam centre at U1,
watch if beam centre moves at D1.
7 ctd.. Optimisation methods:- scale (Q1,2,3) as single unit, scale Decay Solenoid
Example of scaling (Q1,2,3) as unit:Q
1
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Q
2
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Q
3
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Q
1
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IAB
WIW
iRi
n n
Q
2
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Q
3
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Q
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IAB
WIW
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Q
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- after optimal found with (Q1,2,3) & Decay Solenoid, can make
finer tuning via:- decouple Q1, tune 3 params: (Q1, (Q2,3), Decay Solenoid) etc
until each parameter decoupled & tuned.
Downstream beamline optics
Note assume magnetic alignment to be ok.
(having made measurements of Q4-Q9 magnetic axis & set positions of
magnets accordingly. This can start ~ Nov 1st, but if wish to complete
this, will need assistance. Awaiting alignment tolerance at MICE.
So, with well aligned input-beam at central energy – beam should remain
well aligned through downstream section.
No collimation in Phase I – no beam based alignment procedures.
At this stage decide if use momentum(B2=B1) for d/stream optics.
-------------------------------------------------------Recommended by some:If B2=B1 – is it sufficiently useful to help us setup the later muon optics?
Postulated advantages:
- optics solution for pions is same as for muons. (source?!)
- fluxes of pions higher:- aiding tuning speed. Useful at least
for basic optics checks if muon flux impractically low
- backgrounds (eg. large muon/pion background) much lower.
If so, use pion- (~2:1) or pion+ (~3:1)
(range out protons since energy drops/scattering v. difft)
(could easily confirm by putting pions through scaled up downstream
section & checking beam at exit. Also are solutions scaleable to different
muon energies?
Insert Study here from TTl (RIKEN or old beamline).
If choose (B1=B2), scale B2,Q4,5,6,7,8,9 for pion momentum (444.71) &
tune as below from 11 onwards.
------If B2=/=B1, set as muon transport.:8. Check basic optics with B2: explore backward muon momentum edge
(there exists a maximum flux point just above end point where emittance
is minimum)
9. Set B2 to design field.
Optics. Proposed Goal = specific beamsize & waist at MICE still.
(still holds, given diffuser thickness fixed? But requires calcn)
10. Check basic optics: Q4/Q5/Q6 off/off/on & measure change at D4b /
TOF0?
Insert Study here if TOF0 has suitable resolution.
11. Set design optics for Q4/Q5/Q6. Measure D4b/ TOF0. (check centred
into Q789 using D4b if pions.?)
12. Check basic optics: Q7/8/9 off/off/on & measure change at D5 /
(TOF1/Tracker)?
(as before).
Insert study here if TOF1 has suitable resolution/if Tracker is suitable
after TOF1
13. Set design optics for Q7/Q8/Q9. Measure D5 / (TOF1/Tracker)?
14. Measure natural emittance: εo
Postulate: need to calculate desired beamsize waist for match,
given fixed diffuser.
15: Optimisation:Q: ? Optimise Q4/Q5/Q6 initially for maximum flux capture into
triplet lattice? D4b/TOF0? (?inconsistent?)
Optimise Q 4 - 9 for desired optical functions/beamsize at
Tracker:-via single lens scaling of (Q4,5,6) and (Q7,8,9), then decouple
and tune manually.
- via: Transport envelope fitting: to obtain input beam after
TOF0, then use Transport to derive Q7,8,9 for 3 parameters at
MICE (or best fit for 4 parameters). (simulation to confirm
utility or not)
Generally thick diffuser for achieving good 4th parameter.
q
7
C
k
1
q
8
q
9
t
1
x
x
- Via: Response matrix. Everyones “at it” nowadays: ISIS, PSI…
etc etc.
eg. Derive d(optic function)/dK(Quad_n) (simulation to
confirm) eg.
-
 x

 Q1
 x
 Q1




x
Q 2
 x
Q 2
x
Q3 .
.


.






Although these may not be the right parameters – may want
beamsize, or indeed beamsize^2 etc etc.
- Via more involved (controlled) optimiser. (CR etc?)
point 15 assumes a number of things ie. know what optics
functions to furnish. (depends on incoming emittance/diffuser.
Scan?).
- also that we can measure what we want to change:ie. want to tune only on a certain momentum cut.
May require kit arriving in Step II eg. Solenoid + tracker for good
p-resolution.
Solenoid available for optics functions May08.