Transcript Camsonne-compton-jan-5-2006 - Hall A

Compton Polarimeter Status
Report
Alexandre Camsonne
Hall 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:
Improve accuracy of experiments by providing 1% beam polarimetery down
to 1 GeV. High precision Parity violating experiments are feasible with this
upgrade
Scope:
New Electron Detector
High resolution silicon microstrips to
improve tracking resolution
Integrating Photon Detector
Improve systematic uncertainties
experienced in the counting method
1.5kW Green Fabry-Perot Cavity
Twice the Analyzing power of present IR cavity
Four-fold increase in Figure-of-Merit
Participating Institutions: Jefferson Lab, Saclay, Syracuse, Clermont-Ferrand, Uva, Duke
Hall A Collaboration meeting
January 5th 2007
A. Camsonne
Expected Performance
Simulation by
David Lhuillier
< 1% error @0.85 GeV
obtained 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
Manufacturer: Innolight GmbH, Germany
• 708 nm Pump Diodes (2)
• 1064 nm Nd:YAG
• 532 nm SHG via PPKTP
1064 nm
@2W
Hall A Collaboration meeting
January 5th 2007
532 nm
@ 0.1 W
A. Camsonne
Green Fabry-Perot Cavity
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.
• Fixed mirror distance
• 2 Axis adjustable mirror mount
• 2 Axis adjustable stands
• UHV compatible
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 mm pitch silicon mstrips
• 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)
•
•
•
•
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)
•
•
•
Silicon microsrtip final design completed
Four planes have been ordered from Canberra-Eurisys system
Delivery of first plane expected late December
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
Setup
FADC
Amplifier
Upstairs counting house
Experimental hall
Amplifier
Fan in/out
New base
PMT
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
Hall A Collaboration meeting
January 5th 2007
A. Camsonne