Progress on Photon Beam and Simulation

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Progress on Photon Beam and Simulation
GlueX collaboration meeting May 20-22, 2004,
Bloomington
Richard Jones, University of Connecticut
Part 1 active collimator Part 2 physics
simulations
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Photon Beam open issues for the TDR

• photon source
• deformation of thin crystals
• improved mounting technique
• tagging spectrometer
• conceptual design under revision talk by J.
  Kellie
• detailed field calculations available P.
  Brindza
• possible advance-purchase item
• photon tagger instrumentation
• tagging microscope
• photon beam instrumentation
• beam line shielding
• beam position control
• photon beam polarimetry

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I. Active collimator prototype

• Tungsten pin-cushion detector
• used on SLAC coherent bremsstrahlung beam line in
  1970s
• technology developed at SLAC through several
  iterations, refined construction method
• reference Miller and Walz, NIM 117 (1974) 33-37
• SLAC experiment E-160 (ca. 2002, Bosted et.al.)
  still uses them, required building new ones
• performance is known

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Design was part of the senior project of
Connecticut undergraduate Chris Gauthier
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Basic design tungten pins on tungsten wedges
12 cm
5 cm
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Manufacturing challenge cutting the pins

• challenges to overcome
• choice of material
• too soft, pins bend and break during tool
  extraction
• too hard, pins are brittle and break off
• how to mount pins in base plate
• tungsten wire forced into holes SLAC method 1
• machined out of one piece using EDM SLAC method
  2
• to the rescue FSU physics machine shop
• have their own in-house EDM machine
• willing to try new things, come up with their own
  ideas
• based on drawings from Connecticut, built 2
  wedges
• raw tungsten too brittle, pins too fragile
• machinable tungsten (95W, 5NiCu) excellent
  result!

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Courtesy of P. Eugenio
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Prototype status and plans

• Parts for a working prototype are assembled
• aluminum housing made in Connecticut machine shop
• one tunsten pin quadrant delivered by FSU
• data acquisition computer
• electronics purchased by Jlab and delivered to
  Connecticut
• 8-channel sampling ADC card (pci)
• special preamplifier with pA sensitivity (2
  channels)
• Still needed to complete project
• tungsten pins to instrument opposing quadrant
  (from FSU)
• boron nitride insulating support (ordered by
  Jlab, expected 7/04)
• software to read out currents and filter noise
  (student project 7/04)
• couple days of parasitic time in Hall B during
  photon running

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II. Physics simulations

• Hardware development
• built and commissioned new GlueX simulations
  cluster at UConn
• Software development (more about this on Friday)
• upgraded XML geometry database tools to Apache
  XERCES 2
• worked with Curtis to update geometry description
  of CDC
• new tools to support use of XML schemas in place
  of DTDs
• Background studies
• prior background studies have focused on region
  upstream of target
• new information needed to assess design choices
  for vertex counter
• geometry for simulations proposed by Werner
• new results as of this week more about this
  from Werner

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GlueX simulation cluster

• parts purchased by Jlab (GlueX RD funds)
• 16 AMD 2800 processors
• 8 AMD 64-bit opteron processors
• 1 GB ram per node
• 20 GB local disk storage per node
• 5 TB of shared disk storage
• 28K total cost (incl. rack UPS)
• collaboration access
• uses web interface (no logins)
• uses certificates for security
• browse results with paw
• ROOT support coming

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Electromagnetic background study preliminary
results
photon beam
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background study preliminary results
photon beam
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background study impact profile
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background study origin of charges hitting vtx
cylinder
inner surface impacts
outer surface impacts
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background study preliminary
endcap impacts
all charged hits over 1 MeV
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background study preliminary

• Latest results are new
• still have to be carefully checked
• removed vacuum pipe from region downstream of
  target
• accidentally the air that replaced it has no
  magnetic field!
• Rates are very high downstream of target
• most important around hole in FDC, Cerenkov, TOF
  and LGD
• will set an upper limit on the attainable beam
  intensity
• rates far downstream of target sensitive to
  magnetic field, but
• Werners result is probably accurate for the
  vertex counter
• Backgrounds in each forward detector must be
  checked
• important information for the TDR
• may affect design choices in VTX, FDC and Cerenkov