Hall A Compton Polarimeter For Hall A Collaboration Meeting June 23rd 2005

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Hall A Compton Polarimeter For Hall A
Collaboration MeetingJune 23rd 2005

• Sirish Nanda
• Thomas Jefferson National Accelerator Facility
• 12000 Jefferson Ave,
• Newport News, Virginia 23606

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Hall A Compton Polarimeter
Non-intrusive measurement High current capability
- 30 cm deflection chicane - Detection of
backscattered photons and recoil electrons
15 m
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Operational Status

• SRC Experiment
• High current operation
• Beam quality monitoring
• Development tests of integrating DAQ.
• Trouble begins
• Laser Power supply/controller failed.
• Backup power supply incompatible
• Unable to contact manufacturergt PANIC!
• Solution
• Manual calibration of new controller.
• Rework EPICS control algorithm gt Problem Solved.
• We no longer have a spare.

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SRC Expt
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Counting vs. Integrating
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Lightwave 1064nm Laser
Controller/PS (in intensive care!)
Laser Head
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Cavity Lock _at_half power ?
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Compton Upgrade Scope
(Cost 250k)

• Green Laser and Cavity (30 completed)
• Four-fold increase in figure-of-merit
• Larger scattering angles gt possible to detect
  electrons at lower energies
• New Electron detector (5 completed)
• Finer pitch improves energy resolution
• Adjustable distance from beam to improve dynamic
  range
• Integrating Photon DAQ (70 completed)
• Provides redundancy to photon counting
• Improved systematics

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Green Optics Test Setup
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Laser Safety Issues

• Jab Safety Standards require a dedicated Green
  laser room
• Lab management is in the process of get us
  dedicated lab space in the ARC building
• Until then
• We have set up a low power (class II, e.g laser
  pointer) setup in the EEL Lab
• We can study most things at low power
• Get to know the green Laser and cavity
• Test setup is now operational in EEL

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EEL Green Optics lab (Temporary)
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Laser Power Response
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Laser SHG Temp Response
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Green Near field Beam spot
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Green Laser beam profiling
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Green Laser Beam focus
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Turnkey Polarimeter (Thorlabs)
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Prometheus lasers beam pol
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Polarization after FOI/45
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After QWP
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Circular Polarization for cavity injection
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Deepas Prototype cavity
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Cavity Mirror Mount
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Beam Injection to Cavity
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Green beam!
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Conclusion

• The present IR Compton laser/cavity is operating
  ok. But needs a functional backup laser, just in
  case
• The integrating Compton DAQ has made great
  progress. Needs better understanding of
  systematic errors
• The Green Compton project is moving well. But
  needs help.
• It desperately needs a dedicated Green Laser lab.
  
• I hope to complete the Green Compton Project by
  2007.