1 / 22

Hall A Compton Polarimeter Upgrade

Hall A Compton Polarimeter Upgrade. Sirish Nanda Jefferson Laboratory PRex Collboration Meeting July 28, 2006. Compton Polarimeter Upgrade. Motivation:.

tyne
Download Presentation

Hall A Compton Polarimeter Upgrade

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hall A Compton Polarimeter Upgrade Sirish Nanda Jefferson Laboratory PRex Collboration Meeting July 28, 2006

  2. 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

  3. Expected Performance Simulation by David Lhuillier < 1% error @0.85 GeV obtained in about 4 hrs with 50 uA beam

  4. Optical Setup • Laser frequency is continuosly tuned to lock to Fabry-Perot Cavity

  5. New Compton Lab • Compton Polarimetry Lab • New green laser lab (shared by Halls A & C) • In ARC Building Rooms L310 and L312 • L310 is laser controlled area, L312 is office/control room • Lab Status • Occupancy in Nov 05 • Infrastructure completed in May 06 • Cleared for Laser Safety (LSOP approval) June 06 The CPL is now fully Operational

  6. The Compton Team

  7. Prometheus Green Laser • Manufacturer: Innolight GmbH, Germany • 708 nm Pump Diodes (2) • 1064 nm Nd:YAG • 532 nm SHG via PPKTP 1064 nm @ 2 W 532 nm @ 0.1 W

  8. 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

  9. Production Cavity

  10. Cavity Mirror Mount

  11. Fabry-Perot basics • Wave equation looks like harmonic oscillator: • Solutions for x and y are Hermite-Gauss polynomials • Longutunal Modes • Transverse Mode

  12. Resonances in Prototype Cavity Resonance Scan • Tunable laser  Slow thermal mode • Tuning Coefficient  -6 GHz/K • Injection Power  20 mW • External ramp voltage  10 mHz, 110 mVPP • Laser temperature varied 28.32C to 28.38C • TEM00 Resonance observed at every 3.5s Transmission Photodiode signal Frequency Ramp Finesse Measurement F=FSR/dn <Finesse> 54524 + 10504 Meets requirement

  13. Transverse Modes of the Cavity Setup Injection Power 20mW Thermal Frequency Scan With 20 mHz 80 mV TEC voltage ramp Imager: Spiricon LBA camera • Strong TEM00 modes • However, many high order modes…

  14. Optics Summary • Laser • Laser characterization (profile, intensity, stability, noise) completed (Alex Jousse/Xiaochao) • Unfortunately, the prometheus laser reaches only 25% of rated power • The beam is multi-mode and highly elliptic:( Alex is working on “beam circularization” • The laser is to be returned to Innolight (Germany) to bring it back to factory specs => 4 - 6 Weeks down time. • Alignment • Cavity mirror alignment with red HeNe laser works • High resolution motorized mirror alignment and beam steering implemented (David Jacobs) • LabView control interface developed • Cavity • Prototype Cavity demonstrates strong TEM00 resonance • Production cavity being assembled and vacuum tested (Greg Marble) • PDH Lock • Software Slow ramp frequency scan implemented (Sue Witherspoon) • Frequency modulation tests in progress

  15. Prometheus Laser Power • We have done a complete scan of Pump Diode current, Nd:YAG temp and PP-KTP temp • The best power we could achieve is around 20-30 mW.

  16. Prometheus Beam Profile (Jousse) Not 100% TEM00, significant ellipticity

  17. Motorized Mirror Control (Jacobs) LabView Interface to Newfocus Picomotor Drives Note: this is the motion System in the final cavity

  18. New Electron Detector • Electron Detector (Bernard Michelle) • New MOU with LPC Clermont-Ferrand signed • LPC takes responsibility for a new high resolution electron detector • Will 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 (M. Brossard) • New DAQ Software (Alex Camsonne)

  19. Electron Detector Status Detector • Silicon micro-strip design finalized • RFQ from Canberra systems for procurement in progress Mechanical • Preliminary mechanical design completed • Interference with photon detector being addressed • Installation plan with AES in development

  20. Photon Detector • Issues • Present calorimeter is 5x5 array of PbWo crystals. Each crystal now is 2x2x23 cm. Not have enough Mollier width to catch the whole shower in one crystal => Complicated response function analysis. • The crystals matrix is housed in a temp. controlled enclosure taking up precious real estate. Temp stabilization is not used. • New electron detector chamber interferes with present photon calorimeter • Moving the photon calorimeter upstream by 40 cm will work for 6GeV program, but a logistical nightmare • For 12 GeV operation, the photon detector will move up by 10 cm. The present calorimeter will interfere with beam line in addition to electron detector. • New Photon Calorimeter • Single block with 3 or 4 Mollier radius wide and 22 rad length deep and a single PMT. • Preserve counting capabilities. Time response has to be less than 120 ns • 8x8x23 cm single block PbWo in a compact enclosure and side coupled PMT • Study and conceptual design required • Integrating DAQ for improved systematic errors • Flash ADC in lieu of analog electronics under evaluation • Bob Michaels and Rich Holmes are working on the FADC DAQ prototype

  21. Compton Detectors

  22. Summary The Hall A Green Compton Polarimeter Upgrade Project is on track to be operational in early 2008 - Action Items: Simulation to determine optimal electron detector plane separation New compact photon detector conceptual design Grad student participation in 2007.

More Related