MICE -- what running strategy?
disclaimer:
of course the running strategy will evolve as problems arise;
nevertheless think about it ahead of time
to set goals to be achieved
raise issues that may influence design features
The discussion here is triggered by the need to engineer the diffuser
and to freeze the beam line design.
MICE Collaboration meeting Alain Blondel 24 October 2005
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PHASE I
m
-
STEP I:
April 2007
STEP II:
October 2007
STEP III: 2008
PHASE II
STEP IV: 2008
STEP V
2008?
STEP VI
2009?
MICE Collaboration meeting Alain Blondel 24 October 2005
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m
-
STEP 1
STEP 2
Establish beam match and
whether we have all knobs
necessary to draw
emittance vs. transmission
curve. Measure emittance
I will not consider this for now. This will only be interesting if
the Spectrometer Solenoid 2 is very substantially delayed.
STEP 2.5
Split tracker in two
parts and measure
against each other
(systematics)
Insert absorber (solid)
between the two halves
STEP 2.6 and
measure pt & E
distribution and
emittance change
 Publishable result!
These are mostly questions for beam design and matching to and within solenoid.
MICE Collaboration meeting Alain Blondel 24 October 2005
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Step 1 and 2 already require from the beam line to have a number of basics:
1. statistics
Assume 600 good muons per 1ms spill.
This takes 4166 spills= 1h10 for 1spill per second.
(a large factor less (~10) if one measures e.g. eout/ein to 10-3)
However
- DAQ limit of, say 300 particles per ms spill  X2
- applies to *all* particles that have been triggered
- ratio of good muon per trigger? X2 *?*
- beam and MICE efficiency will not be 1.
+ in step 1-4 we are *not* limited to 1 spill per second and ISIS permitting,
we could certainly envisage a few spills (5?) per second and recover
some of the factors listed above. heating!
time spread due to muon decay channel: 5m*(0.95-0.85)*3.3~=1.5ns.
MICE Collaboration meeting Alain Blondel 24 October 2005
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beam aligned?
question 1:
how well should the <x> <x’> and <y> <y’> be =0
for beam to be considered aligned?
answer (Chris Rogers) : assume we want to reweight the beam
with factor per particle of no more than 10% leads to alignment of better than
dx ~< 0.035 sx (C.R., to be verified) and similarly in the other dimensions.
this will require about ~1000 muons only
-- easy. – if one has the knobs to do the tune!
MICE Collaboration meeting Alain Blondel 24 October 2005
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WHICH KNOBS?
1. bias in quadrupoles (to generate dipole effect) -- or
2. recover dipole correctors from e.g. LEP and place them at
90(*2k+1) and 180(*k) degrees from diffuser at entrance of MICE in each plane
since there will be different optics for different emittance generations,
it is not automatic to assume that the phase relations will remain always correct.
If the knobs are not independent …
X5 (assume 5-point scans) for each dimension and a fitting programme.
With our statistics, this will take 1 second per point,
thus requires an automatic procedure!
doing this by hand will take several minutes per point thus more than an hour,
and obviously needs to be done at least once per point.
IN STEP I a first alignment in (x,y) can be obtained from TOF1 – however
there will be no measurement of x’
Q: could we use a tracker prototype for this?
and there will be no measurement of p.
MICE Collaboration meeting Alain Blondel 24 October 2005
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beam matched?
we will want to generate matched beam: sx2 = e.b sx’2 = e/b
with no dispersion.
but perhaps a particular relation between amplitude and energy
question 2:
what precision is needed on this match to satisfy cooling measurements?
question 3:
can the beam gnerate the energy-amplitude relation
or should the analysis do it?
beam intensity?
Obtaining the ‘right’ number of muons per spill
at 140 MeV/c or 240 MeV/c
will require different tuning of the target dip depth -- or collimation.
Which is more desirable?
 many knobs to scan for a given diffuser setting.
what precision needed  how many muons will be needed to do this?
Once the baseline setting is matched and understood, will want to repeat the
exercize for various momenta and various diffuser to check that we can
really generate all beams we need/want from 1 to 10 mm emittance.
MICE Collaboration meeting Alain Blondel 24 October 2005
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Bob Palmer:
p+
p0
p-
in MICE, the diffuser does not generate this kind of correlations,
and we may want to scan momentum to ensure good population
of phase space in the corners.
MICE Collaboration meeting Alain Blondel 24 October 2005
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Ancillary data and measurement
We will also need data to do the initial alignment/calibration/characterization
of the detectors.
Without and with mag field, vs momentum etc…
I think the detector experts should think about it and define their needs.
Do we need for instance a muon beam with small momentum spread?
– I think it could be very useful in step I
Do we need a beam enhanced in electrons or pions in order to tune up
the PID detectors?
We will also need to establish the beam momentum scale … (wrt TOF?)
MICE Collaboration meeting Alain Blondel 24 October 2005
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Step 3 and beyond
from step 3 onwards, we will also go through changes of MICE optics
flip/no-flip
and from step 4 onwards we will go through changes in absorbers
and changes in beta-function
A first study of the number of points and changes was made by Rob Edgecock
at the collaboration meeting 5 (CERN; March 2003)
The only change to his list would be that we may need to scan both over
-- nominal momentum of MICE optics
-- beam central momentum.
ex: if MICE is set to cool best at 200 MeV/c
(i.e. MICE magnets set to this momentum)
we may need to run central beam momentum at
(i.e. beam magnets set to)
e.g. 160, 200, 240 MeV/c
to cover well the momentum width of a real beam, or the amplitude momentum
correlations etc..
MICE Collaboration meeting Alain Blondel 24 October 2005
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from Rob Edgecock
-- add beam momentum with three points and end up
with 65600 points.
-- it is clear that some paramenters need to be
factorized (RF volts for instance?)
MICE Collaboration meeting Alain Blondel 24 October 2005
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my own list for e.g. step 4,5 is similar:
MICE momentum
4 (140, 170, 200, 240)
beam momentum
3 (P+,P-,P0)
emittances
5 (1,2,3,6,10) (focus on low to measure eq.emittance)
beta
4 (42cm, 25 cm, 15cm, 7 cm)
flip and non-fip
2
repeat with a few absorbers. 4
we end up with 2*4*3*5*4 *4 ~1920
no so different…
People will come up with their own pet ideas, for sure. some may be good ones,
and better than this kind of brute-force ‘scan-it-all’ attitude.
+ interleave data with RF off
MICE Collaboration meeting Alain Blondel 24 October 2005
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NB: I would not know how to do the measurement related to this curve:
MICE Collaboration meeting Alain Blondel 24 October 2005
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the next question to understand is how to nest these loops
(which procedure do we do more often, which less)
beam momentum change
MICE momentum change
diffuser interchange
MICE optics
flips
absorbers
in order of my perceived potential damage involved.
the natural tendency would be to do what is written in proposal, i.e.
to perform emittance scan for given MICE and beam settings.
This requires interchanging the diffuser very often.
Is this the best thing to do from the point of view of
running efficiency and systematics?
MICE Collaboration meeting Alain Blondel 24 October 2005
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How do we measure transmission?
this would need a trigger like
TOF0*TOF1 (*tracker1?)
MICE Collaboration meeting Alain Blondel 24 October 2005
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here the following questions arise:
-- how bad is it to modify the MICE optics settings,
or turn off MICE magnets,
with very large forces at play?
should we thrive to minimize how often we do it?
-- does a change in beam momentum require a change in diffuser?
preliminary answer from Kevin et al: approx: NO
but what about the fact that beta (spectrometer) changes?
-- does a change in beam momentum require a whole cycle of
1. beam tuning
2. beam magnet cycling
how long would this take and how reproducible can this be?
-- how long does it take to change the diffuser?
-- how long does it really take to collect enough statistics?
MICE Collaboration meeting Alain Blondel 24 October 2005
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Given these uncertainties I would advocate that the diffuser change over time
should be as fast as possible, (30 minutes was given as specification)
and should avoid turning off MICE, if we can avoid it,
as this would take several hours.
MICE Collaboration meeting Alain Blondel 24 October 2005
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Conclusions
1. we will have a lot of fun running MICE.
2. We need to think of a number of issues
-- beam correctors and adjustment procedures
-- trigger for transmission
-- think of what we want (and factorization) as data points.
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MICE Collaboration meeting Alain Blondel 24 October 2005
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