Proposal for PrimEx Pair Spectrometer G8 Commissioning Plan
D. Lawrence
7/12/2001
Linearity mapping
Measure the P.S. coincidence rates as a function of beamline devices to check its linearity:
P.S. vs. Tagger rates
Use 2x10-5 r.l. radiator to access low photon beam flux
Set dipole current to nominal (800A?)
Beam currents ranging from 50pA to 30nA
Beam current changes in 100pA steps up to 2nA
Beam current changes in 2nA steps up to 30nA
Take P.S. triggered data for approximately 1min. per point
P.S. vs. Converter thickness
Use diamond radiator
Beam current should be chosen such that the P.S. rate with the 10-2 r.l. converter is close to that of G8 production running.
Set dipole current to nominal (800A?)
Take P.S. triggered data for approximately 3 min. using each of three converters:
10-4 r.l.
10-3 r.l.
10-2 r.l.
Dipole current optimization
Maximize the P.S. coincidence rates by varying the dipole current:
Degauss magnet to establish point on hysteresis
Establish G8 production running conditions
Set dipole current to successively higher values until the E-counters in coincidence with the P.S. are the same as those in the middle of the coherent bremstrahlung peak
Beam position monitoring
Measure the correlation between beam position and rates in P.S.:
Establish nominal G8 production running
Vary collimator position in 0.5mm steps from -5mm to +5mm of beam center.
Take P.S. triggered data for approximately 3 min. per point