the hall a compton polarimeter upgrade
DESCRIPTION
The Hall A Compton Polarimeter Upgrade. Sirish Nanda Jefferson Laboratory Parity Collaboration Meeting July 22, 2008. The Hall A Compton Polarimeter Upgrade. Goal:. Provide 1% beam polarimetry from 1 to 11 GeV. - PowerPoint PPT PresentationTRANSCRIPT
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 1
The Hall A Compton Polarimeter Upgrade
Sirish Nanda Jefferson Laboratory
Parity Collaboration Meeting July 22, 2008
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 2
The Hall A Compton Polarimeter Upgrade
Goal:
High Power Green Fabry-Perot Cavity Twice the Analyzing power of present IR cavityIncreased in Figure-of-Merit
Provide 1% beam polarimetry from 1 to 11 GeV. High precision Parity violating experiments are feasible with this upgrade
New Electron Detector - High resolution silicon microstrips to improve systematic errors- Movable in dispersive plane for wide energy coverage
New Photon Detector - Large single crystal GSO calorimeter - Integrating FADC for improved accuracy- Preserve counting abilities
Participating Institutions: Jefferson Lab, Saclay, Syracuse, Clermont-Ferrand, Uva,
Duke, Carnegie-Mellon, William & Mary
Scope:
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 3
Electron Detector LPC Clermont-Ferrand
• Scope• 768 ch 240 m pitch silicon strips• 4 Planes, 192 strips/plane, 1 cm spacing between planes• 120 mm Vertical motion to allow coverage of Compton edge from 0.8-11 GeV• New custom front-end, FPGA trigger module (ETROC)• New DAQ and Analysis Software
Installation in Aug-Sep 08. Commissioning during the Transversity expt Oct 08-Jan 09
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 4
Electron Detector Plans
• Installation• Installation of e-detector in Aug/Sep 08• Mechanical design complete (Miller/Gavalya). Fabrication of parts in progress.• Neil Wilson (Jlab) and Francois Daudon (Clermont) heading installation activities• Survey and Alignment plans (Curtis) in place
• Checkout• Control system interface (Segal/Witherspoon) in progress• DAQ (Camsonne/Brossard) developed
• Commissioning• First beam during Transversity Expt in Oct 08. • Pressing need: New Electron Event Analyzer!! Requires collaboration help
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 5
Photon DetectorCarnegie-Mellon University
• Calorimeter
• Single crystal GSO, 6x15 cm cylinder, Single PMT• High light output, fast decay time (less than 60 ns) • Can do triggered counting as well as integration. • GSO Crystal procured from Hitachi, under test at CMU• Mechanical support/electronics in design
• Integrating DAQ
• Required for 1% polarimetry @1Gev• New Flash ADC’s beam tested in Feb 08• Further tests planned this fall/winter
• Installation • Installation planned for Spring 09
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 6
Green Fabry-Perot CavityJefferson Lab, Syracuse U
• Specification
• Intra-cavity power 1.5 kW • Wavelength 532 nm• Mode CW, TEM00
• CIP Spot size () 65 m• Locking PDH
• Solutions• Primary: Prometheus Laser + PPLN Doubler -> High Finesse cavity
» PDH Feedback to laser for TEM00 mode lock
• Alternate: Lightwave IR laser + IPG fiber Amplifier + PPLN doubler -> Medium
Finesse Cavity
» PDH Feedback to laser
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 7
Optical Setup
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 8
Cavity in the Compton Lab
Photograh: Alan Gavalya
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 9
Cavity Progress
• Power• So far we are doing <100 Watts in intra-cavity power. Need more that an
order of magnitude improvement!
• Progress• Laser, Optics, Mechanics well understood• Home made Cavlock feedback solution is successful in locking• On demand stable locking demonstrated at low power (Abdurahim)• High power locking in development
• Cavlock production version in implementation (Dan Sexton)• Electronic noise issues being chased (Lawrence Lee)
• Problems• Our cavity mirrors are too lossy, limiting power gain• Need new mirrors with < 10 ppm scatter and absorption loss. • Need clean-room to maintain low loss in mirrors
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 10
Cavity Plans
• New Mirrors• We need new low loss mirrors!• Mirror substrates with <0.5 Angstrom surface finish ordered from
General Optics Corp. Delivery in Oct/Nov• In talks with General Optics, Advanced Thin Flims (ATF), Research
Electro Optics (REO), and Layertec for low loss mirror coatings• Hope to finalize mirror coating contract soon
• Mirror Characterization• MOU in development with ODU to surface map high finesse mirrors to
provide SEM, AFM, and Diffusion Scatter studies of mirrors.• Will give us quantitative measure of losses in cavity mirrors
• Existing IR Cavity• Losing Power, presently at ~450 Watts• Plan to replace 230 mW laser with 700 mW• Boost power to ~1.3kW
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 11
PPLN Frequency Doubler
• Passive SHG with periodically poled (PP) Lithium Niobate (LN)• Use IR Nd:YAG laser as 1064 nm pump• Double frequency with Quasi-phase matching (QPM) of non-linear crystals e.g KTP or LN• LN is more efficient that KTP
• Our accomplishments with PPLN Doubling• QPM is sensitive to temperature• We have achieved temp stabilization ~ 10 mK with home made TEC temp control• Better than 20 mK temp uniformity along a 50 mm crystal• Better optical mode matching of pump IR beam
>> We have achieved >12%/W SHG conversion efficiency. >> Demonstrated 1 watt green power with 2.9 watt IR pump
• Plans
• Go to higher power• Demonstrate locking capabilities of the PPLN Laser• Progress recently stalled due do lack of man power• Brian Han (W&M) is now ramping up the effort
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 12
Schedule
Aug-Sept 08Aug-Sep 08
March 09
Jan-Feb 10
2008 2009 2010
June-Aug 09
Thomas Jefferson National Accelerator FacilityS. Nanda, July 22, 2008 13
Summary
• Electron detector ready for Installation in Aug 08
• Photon detector development proceeding well, installation in March 09
• Progress with Green FP cavity
• Robust cavity lock at low power has been achieved• High power lock-in in development• New low loss mirrors on order• Cleanroom infrastructure under implementation• PPLN laser @1 watt demonstrated. Further development necessary
• Aiming for installation of green cavity in Winter 09