Focal%20Plane%20Scanner

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Focal Plane Scanner

• Jeff Martin
• University of Winnipeg
• with Jie Pan, Peiqing Wang, David Harrison

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Motivation

• Q2 determination, background studies, all done at
  10 nA using tracking system.
• Region III operable up to 100 nA.
• Qweak production running 180 ?A.
• Need a way to extrapolate over 3 orders of
  magnitude.

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Qweak Focal Plane Scanner

• A scanning detector with small active area to
  sense high-energy electrons, operable at any beam
  current.
• Similar technique used in E158 and HAPPEx.
• For E158, it was used to determine optics
  parameters, confirm Monte Carlo predictions of
  rates.

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Scanner Principle
pre-rad
quartz radiator

• Design criteria
• 1 cm2 active area.
• 1 MHz max rate allows operation in counting mode
  with two PMTs.
• operable at both high and low current.

C
scattered electrons
air-core light pipe
PMT
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Scanner Concept
scattered electrons
beam view
side view
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Implementation in Qweak
C-bar
y-axis motion
x-axis motion

• 2D motion assy scans behind C-bar
• Mount in any one octant at a time
• Attach to fixed support structure
• Motion assy mounted inside C-bars

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Recent Progress on Scanner

• 3/06 Approval from CFI received (detector lab)
• 4/06 Funding from NSERC received (scanner)
• Report for today
• Start of prototyping tests related to detector
  performance.
• Simulation of detector performance.
• Mechanical design
• Mounting and 2D motion assy.
• Detector assy.

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Prototyping Tests
(Pan, Wang, Harrison)

• 2 tube lined with Alzak sheet (aluminum sheet
  with PVD aluminum on top, and clear anodized)

Anomet
MIRO 2
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Prototyping Tests Cosmics Testing
upper trigger
test detector
lower trigger
inside Alzak tube is a small test scint mounted
on a plunger
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Prototyping Tests

• MCA reads out shaped pulse height.
• Begun work with small scintillator samples.
  (Plan to transition to quartz)
• Begun work with high reflectivity light pipes.
• Electronics to be replaced with CFI funded
  detector lab.

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Simulation

• Builds on QweakSim (K. Grimm, M. Gericke)
• Currently at stage of benchmarking vs. E158 NIM
  article.

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Simulation comparisons to E158 NIM
Jie Pan
E158

• work in progress
• q.e. model not right, etc.

different prerad
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Mechanics

• support structure (P. Medeiros, G. Smith)
• 2D motion assy.
• detector assy. (P. Wang and G. Mollard _at_ UM)

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Mechanics

• support structure
• early 2006, decision to not use R3 rotator
• plan now is to mount to fixed Cherenkov-bar
  support structure, most of device in towards
  beamline.
• motion octant-to-octant possible by bolting
  device in place
• need drawings!
• 2D motion assy.
• budgetary quote from Bosch-Rexroth.
• no progress other than some discussions with P.
  Decowski (E158 scanner) on rad hardness.

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Mechanics

• detector assy.
• initial 2D CAD drawings
• begun 3D SolidWorks model (P. Wang)
• eventually, support from UM shop (G. Mollard)

starting on SolidWorks design
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Summary and to-do list

• Answer prototyping/simulation questions
• radiator design (quartz? scint? size? tilt angle?
  prerad?)
• tube diameter (backgrounds)
• two-tube layout (backgrounds and fiducial area)
• establish viability of coincidence technique
  (rates)
• Mechanics
• support structure need P. Medeiros time.
• purchase 2D motion assy. and program it.
• design and build a mechanical mock-up of detector
  assy and then a realistic detector

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Additional Usesof a Scanner Detector

• Scan over large fiducial region, into inelastic
  region, over Cherenkov bar light guides, to get
  additional confidence in backgrounds.
• Light map can be compared to simulation.
• Q2 extrapolation/determination
• mini-torus setting during production running?
• gas vs. liquid target extrapolation?
• at least, complementary to region III.

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Implementation in Qweak
C-bar
y-axis motion
x-axis motion

• 2D motion assy scans behind the C-bar
• Mount in one octant, attach to fixed support
  structure

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Implementation in Qweak
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Implementation in Qweak
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Implementation in Qweak
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Implementation in Qweak
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• Expected rates at 180 ?A

courtesy J. Mammei

• Max rate 1 MHz

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Procedure

• Measure light distribution with scanner at low
  beam current acceptable to region III and
  Cherenkov bar coincidence.
• Measure light distribution with scanner at 180
  uA.
• If they are the same, region III/Cherenkov light
  distribution believable at 180 uA to high
  confidence.
• Note scanner light map will not be the same as
  the region III/Cherenkov bar coincidence map.