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Møller Polarimeter Status Update. Møller hardware status (detectors and targets) Systematics for SANE Plan Dave Gaskell SANE Collaboration Meeting May 30, 2008. Hall C Møller Polarimeter. Superconducting solenoid  Brute force out of plane magnetization. Scintillators  set “tune”

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m ller polarimeter status update

Møller Polarimeter Status Update

Møller hardware status (detectors and targets)

Systematics for SANE


Dave Gaskell

SANE Collaboration Meeting

May 30, 2008

hall c m ller polarimeter
Hall C Møller Polarimeter

Superconducting solenoid

 Brute force out of plane magnetization

Scintillators  set “tune”

Calorimeter  measurement


Scintillators refurbished before G0 Back angle

 Additional repairs before GEp

One dead scintillator on left arm appeared during GEp

GEp Configuration

Kicker test target

4 mm foil

1 mm foil

Not accessible


Present target configuration optimized for “high current” running  1-2 mA

At 100 nA, dP/P=1% (stats) would take 2.4 hours on 4 mm target (5.9 GeV)


Replace 1 mm foil with 10 mm foil

Replace “not accessible” with 20 mm foil and make accessible with new actuator

systematics g0 forward angle
Systematics: G0 Forward Angle

Systematic error budget from G0

Forward Angle expt.

dP/P = 1.32%

systematics sane
Systematics: SANE
  • No “high current extrapolation”
  • Leakage more important

dP/P < 1.5%?

systematics sane1
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



hall c m ller during gep
Hall C Møller during GEp

Some hint of dependence of polarization on QE!

collimator issues
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 issues1
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

m ller measurement plan
Møller Measurement Plan

Measurements desired every 2-3 days

Two options:

  • RSS-style general procedure that anyone on shift can follow
    • Can make measurements anytime – whenever convenient
    • Results may be a little less reliable
  • 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