A Scintillating Fibre Tracker for MICE

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A Scintillating Fibre Tracker for MICE

• Research Techniques Seminar
• Fermilab
• 27th July 2005

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Muon Cooling

• Strong motivation to produce intense beams of
  muons (e.g. Neutrino Factory).
• Conventional cooling techniques will not work due
  to the short muon life-time.
• Proposed solution Ionisation Cooling.

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Muon Ionisation Cooling Experiment

• Aims
• Design, build, commission and operate a realistic
  section of a cooling channel.
• Measure its performance in a variety of modes of
  operation and beam conditions.
• The results from MICE will allow optimisation of
  a full scale cooling channel.
• MICE
• 3 Continents
• 7 Countries
• 140 Engineers, Particle and Accelerator Physicists

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MICE Channel and Instrumentation
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Rutherford Appleton Lab
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Muon beam from ISIS
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m
Step I Spring 2007
Study Systematically
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Emittance and Cooling

• Transverse Emittance
• Cooling
• Maximise cooling and minimise heating by using
  strong focussing and Liquid Hydrogen.
• In MICE

Cooling Term
Heating Term
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Measure heating cooling
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Goal
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Map curve of ?? vs ?in (heating part as well as
cooling part)
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MICE Tracker

• MICE requires two identical trackers to measure
  each muon individually as it enters and exits the
  cooling channel.
• Tracker needs to safely operate next to the
  liquid Hydrogen absorbers and in the presence of
  the strong background (RF and X-rays/conversions)
  from the RF cavities.
• Solution Scintillating Fibres readout with
  Visible Light Photon Counters (VLPCs).

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RF Background

• Dark current measurements with an 805 MHz cavity
  (lab G FNAL) in a magnetic field with 1mm fibres.
• Extrapolation to MICE (201 MHz) gives 0.8
  kHz/cm2 per SciFi plane.
• Very large uncertainty!

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A MICE Tracker
A Station
Carbon Fibre Support
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Fibre Plane (Doublet/Ribbon)
Active Area
Radius gt 15cm

• 350 mm scintillating fibres are arranged in two
  overlapping rows to form a sheet of fibre.
• Active area has a diameter of 30 cm.
• Small fibre minimises radiation length in
  direction of muon passage.

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Tracker Design

• Each tracker has five measurement stations
• A station consists of 3 planes
• Each plane has over 1400 fibres.
• Light from groups of seven neighbouring fibres
  are read out on a single VLPC channel.

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Scintillating Fibre

• Fibre supplied by Kurrary.
• 350 micron diametre, double clad.
• Polystyrene core is doped with 1 p-terphenyl
  (PTP).
• Prototype is being used to study varying
  concentrations of 3-hydroxyflavone (3HF).
• Output light well matched to VLPC response.

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VLPCs

• Operate at 9K
• High QE
• Low noise
• High rate

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Tracker Validation

• In order to validate the choice of tracker, work
  has been carried out in a number of areas
• Construction and operation of a prototype
• RF testing to asses vulnerability of VLPCs and
  associated readout electronics.
• Simulation of the performance of the full tracker
  and analysis of the emittance resolution.

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Prototype(s)

• A three station prototype was constructed in a
  few months at the end of 2003.
• Different concentrations of 3HF were used in the
  planes to study optimum light yield.
• Operated at Fermilab using a test VLPC system
  (D0) in two runs, taking cosmic rays.
• Currently preparing a modified version at D0 for
  a test-beam at KEK in September.

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Prototype Performance

• Most probable light yield 10.0 10.5 P.E.
• Expectation based on D0 experience 10
• Resolution 442 4 (stat) 27 (syst) ?m
• Expectation from fibre geometry 424 465
  ?m(single fibre bunch or two fibre bunch)
• Single Plane Efficiency (99.7 0.2)
• Poisson expectation for 10 P.E. signal 99.7
• Dead channels 0.2 (two channels)
• 0.25 assumed in G4MICE simulation based on D0
  experience

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Light Yield Dead Channel
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RF Test

• RF supply used to transmit 201 MHz RF at VLPC
  cryostat and readout electronics.
• Antenna calibrated at Lab G used to record power
  at VLPC cryostat.
• RF power generated up to many times that expected
  from Lab G extrapolation.
• No large signal hits were observed.
• Pedestal width studied.

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Effect of RF

• Mean pedestal width increased by 0.5 ADC count in
  worst case.
• 0.5 ADC count is 0.033 PE.
• Estimated RF power in MICE

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G4MICE

• Software suite for MICE includes
• Simulation and Digitisation (GEANT4)
• Reconstruction and Analysis tools
• Visualisation
• MICE has recently become a VO on the LCG and the
  software has been tested on the GRID.
• A number of analyses have been performed to
  determine
• Efficiency and purity in the presence of 100x
  expected background
• Spatial and momentum resolution
• Emittance Resolution

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Simulation of the Sci Fi Tracker

• The description of the tracker in G4MICE is quite
  detailed and includes
• Individual scintillating fibres inside a layer of
  glue (active core and cladding simulated).
• Dead material including the carbon fibre support.
• The parameterisation of the Sci Fi response was
  based on experience from D0 and has been improved
  to reflect the performance of the prototype
  tracker.

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RF Background Simulation

• A special production was made to simulate the
  emission of X-rays from the RF cavities and
  propagate them towards the two trackers.
• Simulation uses the best available data, but due
  to uncertainty a safety factor of 100x is
  considered.
• Due to the high CPU cost of the RF simulation,
  statistics are currently limited.

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Efficiency and Purity

• Nominal RF rate
• No significant change with 100X nominal RF
  background rate.

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Tracking Resolution

• Emittance measurement is effectively measuring
  the width of the beam in 6 dimensions X, Y, PX,
  PY, T, E
• A finite resolution in a real-world detector will
  result in an error in the measured width, and
  hence bias in the measured emittance.
• Figure of merit was determined that a tracker for
  MICE must measure the relevant parameters to
  better than 10 of the RMS of beam width at
  equilibrium (2.5 p mm rad).
• The Sci Fi tracker has been shown to meet this
  criteria.

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Emittance Resolution

• Analysis code has been developed that allows the
  emittance of an ensemble of particles to be
  calculated using Monte Carlo truth or
  reconstructed track information.
• The emittance bias and resolution have been
  studied.
• A method that allows the bias introduced by the
  detector to be calculated and removed has been
  demonstrated and applied on simulated data.

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Uncorrected 4D Emittance
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Corrected 4D Emittance
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Uncorrected 2D Emittance
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Corrected 2D Emittance
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Emittance Resolution
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Cooling Measurement
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Tracker Validated Next Steps

• The tracker choice and design has been validated
  by MICE, however there is still much more work to
  do
• Develop Quality Assurance techniques.
• Develop complete VLPC/cryostat system that can be
  operated away from Fermilab.
• Optimise design (e.g. station spacing) using
  G4MICE.
• Construct three full trackers and commission at
  RAL...

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Quality Assurance

• Techniques are being developed to allow the
  accuracy of fibre bundling and station assembly
  to be tested.
• A technique under evaluation involves
  illuminating a fibre with a low power UV LED.
• Alignment information will be obtained from a
  Coordinate Measuring Machine.
• Plan to build sufficient stations to build 3
  complete trackers, and chose the best 10 for the
  two MICE trackers.

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Scanning Stage at Brunel
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CMM Measurements
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Second Prototype

• The first prototype has been mounted on a new
  carbon fibre support structure.
• An additional station, made to updated
  specifications, has been added.
• At Fermilab, a new cryostat for MICE has been
  built and is being operated with a Sumitomo
  cryo-cooler.
• Currently testing and debugging readout
  electronics in preparation for a cosmic ray test
  before shipping the complete system to Japan.

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VLPC Cryo System

• Complete and operating to spec at D0.
• Uses a Sumitomo SRDK-415D cryo-cooler.
• With heaters off, temperature is 5.3 K
• Can easily control to 9K.

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Electronics

• Using AFEII boards. Eventually will use Trip-T
  chips for timing information.
• 8 AFEII boards have been tested.

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DAQ Development

• Readout scheme for MICE based on that for D0, but
  modified for MICE needs
• Avnet board used to provide timing and trigger
  control.
• VLSB board (developed at FNAL) will be used to
  readout AFE boards through VME.
• C/Linux based DAQ code under development and test
  for use as first version of the MICE tracker DAQ
  system.

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Future

• Finish debugging and preparation of stand-alone
  system at FNAL.
• Operate prototype in test-beam at KEK.
• Finalise design and quality control procedures.
• Construct and commission full trackers.
• Measure Ionisation Cooling!