Green%20Compton%20Polarimeter%20Upgrade%20For%20Hall%20A%20Collaboration%20Meeting%20December%2016th%202004

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Green Compton Polarimeter UpgradeFor Hall A
Collaboration MeetingDecember 16th 2004

• Deepa
• Graduate Student _at_ Old Dominion University
• Graduate Student Research Associate
• Thomas Jefferson National Accelerator Facility
• 12000 Jefferson Ave,
• Newport News, Virginia 25606
• deepa_at_jlab.org

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Preview of presentation

• Compton Upgrade
• Review
• Status
• Future plan

• Present Compton
• Review
• Status

Review of Compton
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Review of Compton
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Status of present Compton
Cavity locking problems during HAPPEX - Problem
Fixed
EPICS transferred to Accelerator Division
Minor software related problems else smooth
operation
Laser standard operating procedure (LSOP) updated
Liquid Crystal Variable Retarder (LCVR)
under Evaluation Credit to Lingyan Zhu
Compton Operators trained
Operations Manual updated
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Green Compton Upgrade
Comparison of Compton Parameters
Present Upgrade
Wavelength (nm) 1064 532
Intra-cavity power (W) 1500 3000
Cavity Q 1.0x1011 1.8x1011
Luminosity _at_50µA(µ b.s)-1 0.26 0.26
FOM (s.A2) _at_0.85GeV 0.57 2.2
Energy Range (GeV) 2- 6 0.8 6
dPe/pe _at_0.85GeV - 1
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Optical Layout
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Cavity Specifications
Parameters Values Symbol
Finesse 49000 F
Power Gain 14990 G
Q-Factor 1.8x1011 Q
Length 0.98m L
Free Spectral Range 153MHz ??FSR
Cavity Bandwidth 3.12kHz d?Cav
Beam Waist Size 60µm s
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Laser Specifications
Parameters Values Units
Wavelength 532 nm
Output power 200 mW
Mode TEM00
Beam roundness lt1.1
Beam Diameter 0.38 mm
Beam Divergence 2.8 mrad
Polarization gt 1001
Thermal Tuning Coefficient -6 GHz/K
Thermal tuning range 60 GHz
Thermal response bandwidth 1 Hz
PZT tuning coefficient 2 MHz/V
PZT tuning range 200 MHz
PZT response bandwidth 100 kHz
Spectral line width 1 kHz/100ms
Coherence length gt1 km
Frequency drift 2 MHz/min
Relative Intensity Noise (RIN) gt-90 dB/Hz
Noise eater option RIN gt-140 db/Hz
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Mirror Specifications
Parameters Values Symbol
Type Plano-concave
Substrate BK7
Radius of curvature 0.5m ?
Diameter 7.75mm d
Thickness 4mm t
Coating HR _at_ 532nm, 0 concave face AR for planar face
Reflectivity 99.9936 R
Loss lt5ppm A
Damage Threshold 10kW/mm ², CW
Axis edging lt0.015o
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Status of Upgrade

• Laser
• Delivered
• LSOP under development
• Test area in He3 target lab (scheduled from
  January 2005)

• 2. Mirrors
• Ordered - Research Electro Optics (REO)
• Status in Fabrication
• Confirmed delivery date two weeks from now

• 3. Cavity
• Adapt basic design from SACLAY
• Study improvements to mirror mounts
• FEM analysis with IDEAS

• 4. Servo electronics
• Adaptation of the PVLAS design
• Built by SACLAY
• New set of locking electronics shipped from SACLAY

• 5. Transport optics
• Standard elements
• Being ordered
• Estimated delivery date end of January

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Optical Studies
Phase 2 Cavity Characterization
Phase 1 Laser Characterization
Phase 3 PDH Characterization
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Future Plans
Polarization of present cavity
Laser Studies
Q1 - 2005
Cavity Prototype
Q2 - 2005
Mirror Finesse Measurement
Q3 - 2005
Cavity locking - PDH
Q4 - 2005 Q2 2006
Polarization Studies
Installation in Hall A
Q3 - 2006
Q4 2006
Green Compton growth 2005 - 2006
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End of Presentation
Thank you