Hall A Collaboration meeting January 5 th 2007 A. Camsonne Compton Polarimeter Status Report Alexandre Camsonne Hall A Collaboration Meeting January 4 th 2007
Mar 27, 2015
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Compton Polarimeter StatusReport
Alexandre CamsonneHall A Collaboration Meeting
January 4th 2007
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Status in 2006
• Not very big year for Compton since most running was low energy
•Data taken at 2 GeV
•Gen
•He4 polarisation ( test data )
•Current status
•Problem with electron detector seems to have been damaged
•Upgrade developments on going to allow low energy running and better systematics
Hall A Collaboration meeting January 5th 2007 A. Camsonne
The Hall A Compton Polarimeter Upgrade
Motivation:
1.5kW Green Fabry-Perot Cavity Twice the Analyzing power of present IR cavityFour-fold increase in Figure-of-Merit
Improve accuracy of experiments by providing 1% beam polarimetery down to 1 GeV. High precision Parity violating experiments are feasible with this upgrade
New Electron Detector High resolution silicon microstrips to improve tracking resolution
Integrating Photon Detector Improve systematic uncertainties experienced in the counting method
Participating Institutions: Jefferson Lab, Saclay, Syracuse, Clermont-Ferrand, Uva, Duke
Scope:
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Expected Performance
Simulation byDavid Lhuillier
< 1% error @0.85 GeVobtained in about 4 hrs with 50 uA beam
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Optical Setup
• Laser frequency is continuosly tuned to lock to Fabry-Perot Cavity
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Prometheus Green Laser
1064 nm@ 2 W
532 nm@ 0.1 W
Manufacturer: Innolight GmbH, Germany
• 708 nm Pump Diodes (2)• 1064 nm Nd:YAG• 532 nm SHG via PPKTP
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Green Fabry-Perot Cavity
• Fixed mirror distance• 2 Axis adjustable mirror mount• 2 Axis adjustable stands• UHV compatible
Intra-cavity power 1.5 kW
The Mirrors (source Research Electo Optics)• Dielectric HR @532 super mirrors Reflectivity > 99.9937 %• Finesse > 50,000• Loss < 20 ppm• ROC 50 cm
Design Goal: Improve upon Saclay IR cavity non-adjustable mirror design, while keeping mirror distance fixed.
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Assembled Cavity
Photograh: Alan Gavalya
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Cavity Mirror Mount
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Optics Summary• Laser
• The Prometheus laser lost power dramatically and developed large intensity noise within a few moths of operation• Sent back to Innolight, Germany for repairs. 2 month down time and 9K$• After repairs (replacing the pump diodes and realignment) the power is back to over 100 mW exceeding
specification.• However, Botao’s profiling finds that the beam is still 70% elliptic. We will try to solve it with optical circularization.• Intensity noise suppression electronics now installed on the laser. 4k$• Polarization transfer function has been fully characterized (Xiaochao)• Mode matching solution developed (Alex Jousse and Botao Jia)
• Alignment• Cavity mirror alignment with red HeNe laser works nicely• High resolution motorized mirror alignment and beam steering implemented (David
Jacobs) EPICS interface under way (Sue Witherspoon)• Position sensitive photo-detectors installed
• Cavity• The cavity is mechanically stable and responsive to mirror alignment ( Joyce and Ravi)• In 10-8 Torr vacuum (Greg Marble and Ed Folts)• The cavity demonstrates strong TEM00 resonance• However, laser-to-cavity coupling is poor (30%) -> improve mode matching
Hall A Collaboration meeting January 5th 2007 A. Camsonne
New Electron Detector
• Electron Detector (Bernard Michel)• MOU with LPC Clermont-Ferrand• LPC takes responsibility for a new high resolution electron detector• Contribute 1 physicist, 1 engineer, 2 designer/techs• The new detector will be compatible with “12 GeV” machine upgrade
• Specification• 768 ch 240 m pitch silicon strips• 4 Planes, 192 strips/plane, 1 cm spacing between planes• 120 mm Vertical motion to allow full coverage of Compton Edge from
0.8-11 GeV• New custom front-end, FPGA trigger module (ETROC)• New DAQ and Analysis Software
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Electron Detector Status
• Silicon Microstrips (Michel Brossard)
• Silicon microsrtip final design completed • Four planes have been ordered from Canberra-Eurisys system• Delivery of first plane expected late December
• Mechanical (Francois Daudon, Alan Gavalya, Joyce Miller, Chris Curtis)
• Vacuum chamber final design completed, fabrication to begin soon• Survey and alignment scheme finalized • Vertical motion system design in progress• Installation plan in development with AES (Tim Whitlatch)
• DAQ/Analysis (Alex Camsonne)
• Working on CODA interface for new ETROC• Need new electron event analyzer
• Control System (Sue Witherspoon)
• Motion Control EPICS interface• Beam shut-down safety interlock
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Silicon Microstrip Plane
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Electron Detector Assembly Drawing
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Silicon Microstrip Mount
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Compton photon integrating method
• A couple of shifts dedicated to the Compton tune during E03-104 ( Special thanks to S. Strauch and R. Ent )
• Test Flash ADC integrating method• Beam tuning to get a reasonable signal over background ratio• First test with DC coupled base for the PMT of the central crystal• Commissionning of the Flash ADC• Production data ( invasive because of bad injector tune)
Low current running
First Compton events in FADC
Hall A Collaboration meeting January 5th 2007 A. Camsonne
PMTFan in/outAmplifier
Upstairs counting house
Experimental hall
FADCAmplifier
Setup
New base
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Signal from Flash ADC
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Signal from Flash ADC
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Compton events
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Compton signal
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Compton signal
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Measurement principle
• Compton asymmetry ?
Hall A Collaboration meeting January 5th 2007 A. Camsonne
Concluding Remarks
The Hall A Green Compton Polarimeter Upgrade Project is on track to be operational in 2008
- Issues and concerns:
The Prometheus laser’s short lifetime is a concern
Alternative single pass PPLN based green laser is important backup to be studied
Coupling efficiency of the laser to the cavity is rather low at 20%.
More work is needed to improve coupling efficiency.
Locking servo electronics needs more effort and interaction with the manufacturer. An electronics engineer/student is needed.
- On going developments for 2007 :
Electron detector
Cavity
Photon detector integrating method