2012AnnihCountrRateEstimate
Commissioning Plans
Prior to a beam commissioning run, the detector system will be calibrated in the Tunnel using a Na-22 and Co-60 source. The annihilation counter will also be tested during initial tuning with an electron beam. Once a positron beam is established the annihilation counter background will be measured using a series of target in/out rate measurements and additional shielding will be added in the form of Pb blankets wrapped around the detector if necessary. The first measurements using positrons will be done requiring a coincidence between the two NaI detector in order to optimize the signal to noise ratio for detecting the back-to-back 511 keV photons from positron annihilation. The same coincidence measurements will be repeated using an electron beam after the measurements with a positron beam.
Rate Estimates
Previous experiment at the IAC
NaI rate Ratio of positron to electron beam
Assumed Geometry
Assume a 2 mm thick Tungsten target that is 1" square
The target is located at -80 < Z < -80.2 The NaI crystal is 2.32" or 56.49 mm in diameter The NaI crystal is 8" from the target then the opening angle is atan(2.32/8/2) = 8.25 degrees