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User Group Workshop and Annual Meeting, Newport News

P olarize d E lectrons f or P olarized Po sitrons PEPPo @ Jlab Injector. Eric Voutier on behalf of the PEPPo Collaboration. Laboratoire de Physique Subatomique et de Cosmologie Grenoble, France. Motivations Experimental setup Commissioning Asymmetry measurements

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User Group Workshop and Annual Meeting, Newport News

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  1. Polarized Electrons for Polarized Positrons PEPPo @ Jlab Injector Eric Voutier on behalf of the PEPPo Collaboration Laboratoire de Physique Subatomique et de Cosmologie Grenoble, France • Motivations • Experimental setup • Commissioning • Asymmetry measurements • Preliminary results User Group Workshop and Annual Meeting, Newport News June 2-14, 2014

  2. Physics Motivations • Electromagneticformfactors (U,P) • Generalized parton distributions (U,P) • Inclusive structure functions (U,P) • Search for the U-boson of darkmatter (U) • Charge conjugation violation to access C3q (P) • International LinearCollider • Elec(Posi)tron-ion Collider (LHeC, e-RHIC, EIC, MEIC, ENC) • Thermal positron facility 2/25 Newport News, June 2-4, 2014

  3. e-→g→e+ Motivations Eric Voutier Polarized Bremsstrahlung E.G. Bessonov, A.A. Mikhailichenko, EPAC (1996) A.P. Potylitsin, NIM A398 (1997) 395 PEPPo has studied the feasibility of using bremsstrahlung from polarized electrons for the production of polarized positrons. Sustainablepolarizedelectronintensities up to 4 mA have been demonstratedfrom a superlattice photocathode. R. Suleiman et al., PAC’11, New York (NJ, USA), March 28 – April 1, 2011 3/25 Newport News, June 2-4, 2014

  4. Motivations Eric Voutier Polarization Transfer in Bremsstrahlung and Pair Production H. Olsen, L. Maximon, PR 114 (1959) 887 E.A. Kuraev, Y.M. Bystritskiy, M. Shatnev, E. Tomasi-Gustafsson, PRC 81 (2010) 055208 PAIR CREATION BREMSSTRAHLUNG 4/25 Newport News, June 2-4, 2014

  5. Experimental setup Eric Voutier Geant4 Principle of Operation Polarized Electrons (< 10 MeV/c) strike production target Positron Transverse and Momentum PhaseSpace Selection Ee = 6.3 MeV Ie= 1 µA T1 = 1 mm W S1 Pe- PEPPo D e- T1 PAIR PRODUCTION g produce e+e- pairs and transfer Pg into longitudinal (Pe+) and transverse polarization averages to zero • BREMSSTRAHLUNG • Longitudinal e- (Pe-) produce elliptical g whose circular (Pg) component is proportional to Pe- J. Dumas, PhD Thesis (2011) COMPTON TRANSMISSION Polarized e+ convert into polarized g (Pg) whose transmission through a polarized iron target (PT) depends on Pg.PT Pe+ S2 PT D Calorimeter e+ T2 Compton Transmission Polarimeter PEPPomeasured the longitudinal polarization transfer in the 3.07-6.25 MeV/cmomentum range. 5/25 Newport News, June 2-4, 2014

  6. Energy measurement dE/E<0.5% Intensity controls 10 pA – 1 µA Polarization measurement dP/P<3% PEPPo Variable energy 3.1-8.2 MeV/c Polarization controls 30 Hz fast heilicity reversal (delayed) Slow laser polarization reversal (half-wave plate) 4p spin rotator Experimental setup Eric Voutier Experiment Layout • PEPPo ran at the CEBAF injector, taking advantage of the existing beam diagnostics that determine with precision the properties of the polarizedelectron beamentering the PEPPo apparatus. Laser 6/25 Newport News, June 2-4, 2014

  7. Viewers Beam position monitors Solenoid ELEGANT beam optics Viewers Polarized Analyzing Target (7.5 cm Fe) Solenoid Dipoles Corrector magnets Quadrupoles PEPPo branch jonction Faraday Cup Production Target T1 (0.1-1 mm W) Annihilation detector Viewer Positron Selection Device Corrector magnets ReconversionTarget T2 (2 mm W) Compton Transmission Polarimeter Experimental setup Eric Voutier G4PEPPo experiment model 7/25 Newport News, June 2-4, 2014

  8. Commissioning Eric Voutier 8/25 Newport News, June 2-4, 2014

  9. Commissioning Eric Voutier Momentum Calibration S1currentoptimizationat 5.5 MeV/c Cavity gradient calibration Spectrometercurrent calibration Electron beammomentum (MeV/c) Current @ T2 (arbitrary) SRF cavity gradient (MV/m) Spectrometercurrent (A) S1 current (A) • The spectrometercurrent/momentumwascalibratedwith the electronbeam. • The collection and transport solenoidcurrentswereoptimizedwithdegradedelectrons, and confirmedwithproducedpositrons. 9/25 Newport News, June 2-4, 2014

  10. Na22 Commissioning Eric Voutier Positron Signal • Two NaI detectors were used to measure the back-to-back photons emitted by the annihilation of positrons in an insertable target. Target IN Target IN Target OUT Target OUT 4 MeV/c e+ collected from 0.5 nA 7 MeV/c e- on 1 mm W target 10/25 Newport News, June 2-4, 2014

  11. Commissioning Eric Voutier Analyzing Magnet Response • Experimental asymmetries are measured with respect to beam helicity ; they are linearly proportional to the target polarization, itself proportional to the target magnetization. IHWP inserted A. Adeyemi 11/25 Newport News, June 2-4, 2014

  12. Commissioning Eric Voutier Polarization Sensitivity Orientation 4p spin rotator determines e- polarization orientation. (Pe-, 0, 0) (0, 0, Pe-) (0, Pe-, 0) Reverse magnet polarity Reverse beam helicity Pe- = 83.7% ± 2.8%Stat. ± 0.6%Syst. PT= 7.53% ± 0.04%Stat. ± 0.06%Syst. 12/25 Newport News, June 2-4, 2014

  13. AsymmetryMeasurements • Operation • Electron Calibration • Polarized positron measurements 13/25 Newport News, June 2-4, 2014

  14. Asymmetrymeasurements Eric Voutier DAQ Components • CsIcrystalsa (6×6×28 cm3) are coupled to PMTsequipedwith LPSC custom amplified basis to extend the PMT life-time in the high rate environment of PEPPo. • The ~2 µs long and 2 Voptimized signal isfedinto the JLab custom FADC250 thatsampled the signal at250 MHz. Hamamatsu R6236-100 • The flexibility of the FADC250 allows for 3 data taking modes : • Sample (500samples /detector event); • Semi-integrated (1 integral / detector event); • Integrated (1 integral /helicity gate event). FADC 250 14/25 Newport News, June 2-4, 2014

  15. Asymmetrymeasurements Eric Voutier Integrated Mode Operation • The integrated modeoperates for high rate conditions by integration of the PMT signal over the duration of an helicitygate(PEPPofirmwaredevoped by JLab). • Helicityfrequency = 30 Hz • Helicitydelay = 8 windows • Helicity pattern = quartet (+--+ or -++-) h- h+ h+ h- E- E+ E+ E- Simulation 15/25 Newport News, June 2-4, 2014

  16. Asymmetrymeasurements Eric Voutier Electron Compton Asymmetries • Combining experimental asymmetries measured for each analyzing magnet polarity and each laser polarization orientation (IHWP) allows to cancel-out eventual false asymmetries and isolate physics asymmetries. A. Adeyemi 16/25 Newport News, June 2-4, 2014

  17. Asymmetrymeasurements Eric Voutier Charge Particle Trigger Vacuum window Reconversion Target photon C A L O R I M E T E R e+ Trigger Scintillator • The DAQ trigger for positron measurementsconstitutes of a coincidencebetween a thinscintillatorplacedprior the reconversion target, and the central crystal(PMT5). • Drasticreduction of the neutral background. 17/25 Newport News, June 2-4, 2014

  18. Asymmetrymeasurements Eric Voutier Semi-Integrated Mode Operation • For eachcoincidence trigger, the PMT signals are registered in the form of one single valuecorresponding to the signal integrated over 2 µs, and istagged by the helicitystatus of the electronbeam. Simulation Helicityfrequency = 30 Hz Helicitydelay = 0,8 windows Helicity pattern = quartet (+--+ or -++-) • Experimentalasymmetryisdetermined for eachenergy bin and a correspondingpositron polarizationisdeterminedknowingfromcalibrated simulations the energydependence of the positron analyzing power. 18/25 Newport News, June 2-4, 2014

  19. Asymmetrymeasurements Eric Voutier Energy Deposition Spectra e+ Data @ 6.25 MeV/c 511 keVfrom e+ annihilation atrest Time (au) Bremsstrahlung end-point Energy (FADC units) Energy (FADC units) • The location of the 511 keVpeakisused for in-situ monitoring of the effective gain of the read-out chain, and link to radioactive source calibration data. The global accuracy of the photon energymeasurementis2.3%. 19/25 Newport News, June 2-4, 2014

  20. Asymmetrymeasurements Eric Voutier Positron Compton Asymmetries e+ Data @ 6.25 MeV/c PEPPo Preliminary Statisticsonly 20/25 Newport News, June 2-4, 2014

  21. Asymmetrymeasurements Eric Voutier Positron Data Summary • PEPPomeasured the longitudinal polarizationtransferfrom8.19 MeV/ce- to 3.07-6.25 MeV/c e+, and explored influence of the targetthickness. • Two data setfeaturingdifferentshielding configurations. • Threedifferentanalysisschemes : energydependent, energyindependent (helicitygatedscaler), energyintegrated(link to electron calibration). 21/25

  22. PreliminaryResults • Electron analyzing power • Positron polarization 22/25 Newport News, June 2-4, 2014

  23. Preliminaryresults Eric Voutier Electron Analyzing Power • There is a bug in the polarizedtransportionprocessstartingatversion 9.0. • PEPPoisnowusing version 8.3, modified to includepolarizedphoto-electriceffect and bugs fixes or changes in the polarization packagethrough version > 8.3. • The energydependence of the PEPPomeasurements of the electronanalyzing power, isconsistentwithexpectations. • There exists a systematic shiftbetween GEANT4 9.6 simulations and PEPPo data ? R. Suleiman A. Adeyemi 23/25 Newport News, June 2-4, 2014

  24. Preliminaryresults Eric Voutier Positron Polarization Set 1 (Initial Run) Set 2 (Improved Shielding) Set 1 (Initial Run) Set 2 (Improved Shielding) Electron Beam Polarization PEPPo Preliminary Pe+ = AT / k Ae-Pe-PT • Positron polarizationisdeducedusingmeasuredelectronbeam and targetpolarizations, electronanalyzing power, experimentalasymmetry, and estimated e+/e-analyzing power ratio (1.1-1.4). • Significantnon-zeroexperimentalasymmetriesincreasingwith positron momentumsign efficient polarizationtransferfromelectrons to positrons. 24/25 Newport News, June 2-4, 2014

  25. PEPPo Collaboration • P. Aderley1, A. Adeyemi4, P. Aguilera1, M. Ali1, H. Areti1, M. Baylac2, J. Benesch1, • G. Bosson2, B. Cade1, A. Camsonne1, L. Cardman1, J. Clark1, P. Cole5, S. Covert1, • C. Cuevas1, O. Dadoun3, D. Dale5, J. Dumas1,2, E. Fanchini2, T. Forest5, E. Forman1, • Freyberger1, E. Froidefond2, S. Golge6, J. Grames1, P. Guèye4, J. Hansknecht1, • P. Harrell1, J. Hoskins8, C. Hyde7, R. Kazimi1, Y. Kim1,5, D. Machie1, K. Mahoney1, • R. Mammei1, M. Marton2, J. McCarter9, M. McCaughan1, M. McHugh10, D. McNulty5, T. Michaelides1, R. Michaels1, C. Muñoz Camacho11, J.-F. Muraz2, K. Myers12, • Opper10, M. Poelker1, J.-S. Réal2, L. Richardson1, S. Setiniyazi5, M. Stutzman1, • R. Suleiman1, C. Tennant1, C.-Y. Tsai13, D. Turner1, A. Variola3, E. Voutier2, Y. Wang1, Y. Zhang12 1 Jefferson Lab, Newport News, VA, US 2 LPSC, Grenoble, France 3 LAL, Orsay, France 4 Hampton University, Hampton, VA, USA 5 Idaho State University & IAC, Pocatello, ID, USA 6 North Carolina University, Durham, NC, USA 7 Old Dominion University, Norfolk, VA, US 8 The College of William & Mary, Williamsburg, VA, USA 9 University of Virginia, Charlottesville, VA, USA 10 George Washington University, Washington, DC, USA 11 IPN, Orsay, France 12 Rutgers University, Piscataway, NJ, USA 13 Virginia Tech, Blacksburg, VA, USA Manythanks for advice, equipmentloan, GEANT4 modeling support, and funding to SLAC E-166 Collaboration International LinearCollider Project Jefferson Science Association Initiatives Award 25/25 Newport News, June 2-4, 2014

  26. Polarimeter targetpolarization Eric Voutier Analyzing Magnet Characterization E. Froidefond et al., IPAC13, MOPWA079 • The static modelingof the analyzing magnet developed within OPERA-2D is controlled by the measured magnetic map of the fringe field of the solenoid at • ±60 A operational current. Newport News, June 2-4, 2014

  27. Polarimeter targetpolarization Eric Voutier Magnetic Flux Measurement • The iron core target is equipped with 3 pick-up coils measuring the magnetic flux generated upon magnet current variation. • Specific cycling procedures are used during the experiment to monitor the target polarization. < PT > = 7.53% ± 0.04%Coil± 0.06%Opera Newport News, June 2-4, 2014

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