møller polarimeter status update

Møller Polarimeter Status Update

1. Møller hardware status (detectors and targets)

2. Systematics for SANE

3. Plan

Dave Gaskell

SANE Collaboration Meeting

May 30, 2008

Hall C Møller 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)

SANEReplace 1 m foil with 10 m foilReplace “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 AngleSource Uncertainty dAsy./Asy. (%)

Beam position x 0.5 mm 0.15

Beam position y 0.5 mm 0.03

Beam direction x 0.15 mr 0.04

Beam direction y 0.15 mr 0.04

Q1 current 2% 0.10

Q2 current 1% 0.07

Q2 position 1 mm 0.02

Multiple Scattering 10% 0.12

Levchuk effect 10% 0.30

Collimator positions 0.5 mm 0.06

Target temperature 50% 0.05

B-field direction 2o 0.06 0.37

B-field strength 5% 0.03

Spin polarization in Fe 0.25

Leakage 30 nA 0.2

High current extrap. 1%/40 uA 1.0

Solenoid focusing 100% 0.1

Elec. DT. 100% 0.04

Charge measurment 0.02

Monte Carlo Statistics 0.28

Unknown accelerator changes 0.5

Total 1.32

Systematic error budget from G0 Forward Angle expt.

dP/P = 1.32%

Systematics: SANESource Uncertainty dAsy./Asy. (%)

Beam position x 0.5 mm 0.15

Beam position y 0.5 mm 0.03

Beam direction x 0.15 mr 0.04

Beam direction y 0.15 mr 0.04

Q1 current 2% 0.10

Q2 current 1% 0.07

Q2 position 1 mm 0.02

Multiple Scattering 10% 0.12

Levchuk effect 10% 0.30

Collimator positions 0.5 mm 0.06

Target temperature 50% 0.05

B-field direction 2o 0.06 0.37

B-field strength 5% 0.03

Spin polarization in Fe 0.25

Leakage 30 nA 0.2

High current extrap. 1%/40 uA 1.0

Solenoid focusing 100% 0.1

Elec. DT. 100% 0.04

Charge measurment 0.02

Monte Carlo Statistics 0.28

Unknown accelerator changes 0.5

Total 1.32

1. 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

OptimumSANE?

Hall C Møller 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

Møller 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