Shintakemonitor and the background estimation

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Shintake-monitorand the background estimation
Taikan SUEHARA (The University of Tokyo)
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Shintake-monitor upgrade

• Shorter wavelength
• Use 2nd harmonics of YAG laser (532nm)
• FFTB used 1st YAG (1064nm)
• Fringe stabilization
• In FFTB, 17 nm jitter in 6 sec. 22 nm in 25
  sec.
• Some feedback system ?
• Moving fringe pattern
• in FFTB, they moved electron beam instead of
  fringe.
• Use pockels cells or delay line (planning)
• ?-ray detector
• Compton energy is very low (28MeV max.)
• Background is more severe

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Schedule

• The FFTB Shintake-monitor arrival from SLAC (June
  05)
• Background study _at_ ATF ext. line (June 05)
• Shintake-monitor optics electronics test
  (August 05)
• Shintake-monitor upgrade (fall 05)
• Install on beam line (summer 06 ??)
• Beam ON (?)

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Interaction of beam halo with beam pipe

• Charge distribution of the beam (x y)
• Center of the beam gaussian
• Beam tail also gaussian ?
• If gaussian, interaction is negligibly small
  (with proper distance of materials from beam
  line)
• Measurement of charge of beam halo_at_ ATF ext.
  line
• Using wire scanner
• Measure charge of 5 10 s
• We use s as that of center of the beam(gaussian
  fit)

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Beam halo meas. result
Gaussian distribution damps a factor of 1000 for
every sigma, but it only damps s-4
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Integral beam halo estimation
Beam halo seems not to be negligible, We need
some beam collimeter optics ! (they did in FFTB)
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Radiation from beam dump

• Background measurement from beam dump
• Using CsI calorimeters installed around dump.
• Time distribution monitored via oscilloscope and
  compared with Monte Carlo simulation.
• Distance and angle dependence of charge and
  timing of signal also checked.

Detector position
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Raw signal
100ns grid
Beam timing
CsI output
PMT without CsI
Prompt Peak
Delayed Peak
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Monte Carlo simulation(GEANT4)
prompt peak
delayed peak
Prompt delayed peak observed in both
measurement and simulation.
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Position dependenceof each signal

• Prompt signal
• Bigger signal near beam dump
• Timing is faster at upstream of beam line
• ?Combination of photons from beam line and
  beam dump
• Delayed signal
• Delay is larger at detector far from dump
• Interaction of slow neutron around detector
• Not affect for Shintake-monitorbecause of large
  time delay(we can easily eliminate this by
  timing gate)

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Next beam time (6/6)

• To measure beam halo (confirmation)
• Distribution of vertical beam halo
• Energy of beam halo no idea
• Outside 10 sigma Inside 5 sigma
• Difference between MW(04)X
• Dependence of beam parameter(Charge,Beam size, )

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Next beam time (6/6)

• To understand signal around beam line beam dump
• Timing separation of prompt signal
• Plastic scintillator ? (use XTFs ?)
• Air-cherenkov detector ?
• Lead glass detector ?
• Beam line signal (far from dump)
• Attenuation of distance
• Direction of particle
• Simulation
• Effect of shield
• Position dependence on prompt signal