Measurement of particle
production from the MICE target
Kenny Walaron, Paul Soler
University of Glasgow
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Goals of the test
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Target test carried out 1-2 Nov 2006 in ISIS ring.
Main goal: demonstration of a working target dipping into
ISIS
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1st prototype run with slower acceleration
Target design and performance covered by target summary (see P.
Smith plenary talk).
Bias of this talk is particle production: relationship between
singles production into MICE and ISIS losses
Compare singles/p.o.t calculated from Monte Carlo (used
for beam normalisation) and data.
Investigate singles production as a function of average
target depth in final 2ms before extraction
All essential unknowns for MICE previously not studied
Many thanks to everyone who took part in test (ie.
Sheffield and RAL people working on target etc.)
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Target test set-up
Target installed in ISIS
• 2 sets of detectors:
1 shielded pair of scint.+PMTS (MUSCAT) with HV
1 unshielded pair of detectors (Glasgow)+Low V.
• Scope DAQ and readout to Linux PC via GPIB
• Signals from ISIS and target
Schematic of unshielded detectors
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Signals and DAQ
•Thanks to Bill Murray for writing DAQ!
•Non-detector signals to DAQ were: Total beam loss, beam loss from superperiod 7, target position, ISIS beam current
•“Slow” signals did not require fine grained resolution. More important to
sample over entire injectionextraction + a little extra each side
•Detector signals need finer resolution such that one can resolve individual
pulses. Borrowed LeCroy “super-scope” able to provide the 10 ns resolution
and memory depth to sample whole 10ms
•All slow signals and detector signals recorded to ROOT histograms per run
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Simulations of target-test
•Motivation: To compare
singles/p.o.t into MICE angular
acceptance
•MARS and GEANT4 distributions
from target weighted into area
twice MICE acceptance. GEANT4
tracking through air and plastic
using Monte Carlo distributions as
input.
•Simulations were 10 Million,
800MeV/c KE protons incident on
MICE target . This energy
corresponds to proton energy at
extraction
•These are the same target
distributions used to normalise
beam rates along beamline
MARS target distribution in 1600 cm2
GEANT4 target distribution in 1600 cm2
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MARS momentum distributions of
particle species at U/S face of scintillator
Unshielded
shielded
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GEANT4 momentum distributions of
particle species at U/S face of scintillator
Unshielded
shielded
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Charged particle detection efficiency
•To give an estimation of the efficiency of detecting charged particles
we look at number of particles which pass through both scintillators.
•Charge particle efficiency in simulations is defined to be % of singles
incident on upstream face that are present on downstream face
•Vast majority of charged particles are protons. Efficiencies for other
charged species have very low statistics.
MARS target distribution
GEANT4 target distribution
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Neutron detection efficiency
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Non-thermal neutron cross-sections very small
We calculated from parameterisations found in Knoll that detection
efficiency at 30 MeV = 1.4% through 1cm of plastic. Knock on
proton efficiency from previous work roughly >95%
Accurate to
3% in
0<En<30
MeV range
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From simulations (GEANT4=119 MARS=195) neutrons below 30MeV.
X-sect is rapidy falling even a 30MeV/c, at > it is negligibly small
Hence in our MC samples we effectively remove all neutrons when
estimating detector response
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Run summary
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Data recorded for stationary (fixed position) target and
pulsed target (varying delay on start of pulse)
Statistics fairly small.
Second target run in
December was cancelled
Static target stats too low
to say anything
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Detector Analysis 1
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Code written to convert oscilloscope trace files
to more useful ROOT Trees.
Different time bases on scopes complicate
things: expanded “slow” scope signals to match
finer resolution of LeCroy scope. No loss of
information.
Discrimination of PMT signals implemented:
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Discriminator level taken from noise distributions for
each individual PMT: 3s level chosen.
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Detector Analysis 2
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Clusterisation algorithm: consecutive signals above
discriminator level constitute a cluster in data.
All 4 PMT channels discriminated and “clusterised”.
Coincident hits in detectors determined as those clusters
which match to a tolerance of +/- 10ns. Determined by
inspection of data.
Additional analysis performed to try to identify protons vs
MIPS. Reconstruction of saturated pulse heights by fitting
to tail, total voltage (hence charge) of pulse distributions,
pulse length distributions calculated. No features evident
to use as PID handle.
Discrimination level moved to 5s to check effect. No
reduction in number of coincidences. 2s level showed
reduction
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Total coincident hits
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Total number of coincident hits for both
detectors over all target conditions. Red =
pulsed runs, blue = held runs
Unshielded detectors
Shielded detectors
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The last 2ms
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Last 2ms is when MICE target
will be inserted during proper
running so we focus on this
Measured mean number of
coincidences in last 2ms for
both detectors.
Measured average beam-loss
in straight7 in last 2ms
(monitors which will limit
MICE).
Calculated mean kinetic energy
in last 2ms (778+22-64 MeV)
Mean target depth in last 2ms
These quantities are calculated
for each dip-condition.
P (MeV/c)
K.E (MeV)
Time spill (s)
Momentum evolution (blue, MeV/c)
and K.E evolution (red, MeV) over
10ms
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Relationship between singles detected
and beam loss
• Calculated mean number of hits per target dip for all 7 target
conditions in the last 2ms. Remember, different target delay = different
ISIS beam interception
• Calculated the mean total beam loss in the last 2ms for each of these
target conditions (50 mV beam loss trips ISIS!).
Unshielded detector
Shielded detector
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Relationship between singles into MICE
acceptance and beam loss
•Detector angular acceptance scaled to the MICE angular acceptance
•Important result as we now have a measure of how much ISIS beam we
can reasonably take before we trip ISIS and how this translates to
particle yields
Unshielded detector
Shielded detector
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Conclusion 1: Coupling of MICE to ISIS
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The results of least squares linear fits to the data give the
following relations:
These relations are important as they provide first actual coupling
of MICE to ISIS.
They can be used to quantify actual yields from the target into
MICE beamline in terms of the effect on ISIS
Can (although not in this talk) be used as input into run planning
etc. as we now have an upper limit of charged singles into MICE
in last 2ms
At 50mV* beam loss we expect 2.5 x10^5 charged singles into
MICE acceptance
*ISIS BL limit applicable to MICE
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Comparison of singles per proton on
target from simulation and data
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To normalise beam rates along MICE beamline we use the GEANT4
and MARS target simulations
Monte Carlo consists of 10 Million p.o.t. from which we calculate the
number of singles/p.o.t into MICE
A huge amount rests on this. Detector rates, good mu+, run
schedule etc.
Codes show some discrepancy and we believe the average of these
numbers blindly (or at least with cloudy vision). Both numbers could
be out by some factor.
We will try to calculate this number from data and compare to
simulation
This will benchmark our assumptions and see if we can provide
some spectacles.
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Singles/p.o.t calculation
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In simulations, calculation is the pure Monte Carlo truth singles
intecepting detector x efficiency of detection normalised to 10Million
p.o.t
From the data the number of singles is the number of coincident
hits following the event selection of clusters etc/p.o.t
We get number of ISIS protons intercepting target from beam loss
in super-period 7.
Calibration of number of protons lost  signal at SP7 monitors via
communication with Di Wright.
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At 780 MeV (9ms) = 3.5x10^14 Vs/p, At 800 MeV (10ms) =
3.8x10^14Vs/p
If one takes value at 9ms one can calculate number of protons
hitting beam under assumption every proton lost intercepts target.
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Conclusion 2: Singles per p.o.t
comparison:- Validating codes
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Results given below.
Statistical errors only (Poisson) in Monte Carlo
Error in data: combination of statistical error and 8% calibration
error (from assumption of value at 9ms)
Singles/pot
(Unshielded)(x10-8)
Singles/pot
(Shielded)(x10-8)
MARS
1.70+-0.10
1.52+-0.10
GEANT4
2.47+-0.12
1.61+-0.10
DATA
1.59+-0.27
1.29+-0.24
PRELIMINARY!
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Excellent agreement between data and MARS.
Worse agreement with GEANT4
Result from data determined independently to Monte Carlo
Validation of charged singles yield at MICE production angle.
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Mean target position in last 2ms as
function of target depth
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ISIS transverse profile previously not known
We try to obtain an estimate of this from the measured beam loss
for different target trajectories
We try to establish firstly a relationship between beam loss and
mean target depth.
Translate this into a relationship between charged particle singles
into MICE acceptance as a function of target depth
Not ideal as we can only give the beam loss and hence particle yield
assuming an average target depth over the entire 2ms.
Compared to the amount of information available previously (ZERO)
this is still useful
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Mean target position in last 2ms as
function of target depth
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One can see sharp ISIS transverse beam profile
Also shown is the charged particle yield into the MICE acceptance
assuming target is held at the depths shown for the entire 8-10ms
Important as it shows how sensitive the rate into the MICE
acceptance is on target depth.
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Summary
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Target test very useful
Established relationship between beam loss and particle
production into MICE beamline
Validated Monte Carlo simulations used for calculating
beamline rates and “good mu+” rates into MICE
Imaged ISIS transverse profile in the final 2ms and
investigated relationship between target insertion and
particle yields into MICE
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