Mller Polarimeter Status Update 1.Mller hardware status (detectors and targets) 2.Systematics for SANE 3.Plan Dave Gaskell SANE Collaboration Meeting May 30, 2008 Hall C Mller Polarimeter Superconducting solenoid Brute force out of plane magnetization Scintillators set tune Calorimeter measurement Detectors One dead scintillator on left arm appeared during GEp Scintillators refurbished before G0 Back angle Additional repairs before GEp Targets Present target configuration optimized for high current running 1-2 A At 100 nA, dP/P=1% (stats) would take 2.4 hours on 4 m target (5.9 GeV) SANE Replace 1 m foil with 10 m foil Replace not accessible with 20 m foil and make accessible with new actuator Kicker test target 4 m foil 1 m foil Not accessible GEp Configuration Systematics: G0 Forward Angle SourceUncertaintydAsy./Asy. (%) Beam position x0.5 mm0.15 Beam position y0.5 mm0.03 Beam direction x0.15 mr0.04 Beam direction y0.15 mr0.04 Q1 current2%0.10 Q2 current1%0.07 Q2 position1 mm0.02 Multiple Scattering10%0.12 Levchuk effect10%0.30 Collimator positions0.5 mm0.06 Target temperature50%0.05 B-field direction2o2o B-field strength5%0.03 Spin polarization in Fe0.25 Leakage30 nA0.2 High current extrap.1%/40 uA1.0 Solenoid focusing100%0.1 Elec. DT.100%0.04 Charge measurment0.02 Monte Carlo Statistics0.28 Unknown accelerator changes 0.5 Total1.32 Systematic error budget from G0 Forward Angle expt. dP/P = 1.32% Systematics: SANE SourceUncertaintydAsy./Asy. (%) Beam position x0.5 mm0.15 Beam position y0.5 mm0.03 Beam direction x0.15 mr0.04 Beam direction y0.15 mr0.04 Q1 current2%0.10 Q2 current1%0.07 Q2 position1 mm0.02 Multiple Scattering10%0.12 Levchuk effect10%0.30 Collimator positions0.5 mm0.06 Target temperature50%0.05 B-field direction2o2o B-field strength5%0.03 Spin polarization in Fe0.25 Leakage30 nA0.2 High current extrap.1%/40 uA1.0 Solenoid focusing100%0.1 Elec. DT.100%0.04 Charge measurment0.02 Monte Carlo Statistics0.28 Unknown accelerator changes 0.5 Total No high current extrapolation 2.Leakage more important dP/P < 1.5%? Systematics: SANE It is unlikely Wien will be set for maximum polarization to Hall C during SANE At 5 pass and high energy (5.9 GeV) small changes in the beam energy can impact the polarization in the Hall Example: Wien set for 80% of maximum in Hall C at 5.9 GeV 1 MeV shift in beam energy gives 2.3% change in polarization in Hall Optimum SANE? Hall C Mller during GEp Some hint of dependence of polarization on QE! Collimator Issues General philosophy: Let collimators in front of detectors determine acceptance Collimators between Q1 and Q2 clean up backgrounds do not impact acceptance Collimator Issues At 5.9 GeV, collimators between Q1/Q2 come close to impinging on acceptance Collimators 6&7 can collide may cause reproducibility problems Mller Measurement Plan Measurements desired every 2-3 days Two options: 1.RSS-style general procedure that anyone on shift can follow Can make measurements anytime whenever convenient Results may be a little less reliable 2.G0 Forward-style: small group makes all measurements (small= at least 5-6 people) Measurements need to be scheduled More reliable polarization measurements smaller systematic errors