Agenda

Agenda:

Attendance

David, Elham, Kate, Dustin

GEANT 4 results from Tristan Hurst (W&M senior undergrad) show that putting an active detector (i.e. what would be a pion scintillator) directly downstream of the pion detectors aids in counting-mode ability to distinguish pion/muon from Moller events; the pi/mu events are more likely to exit the lucite and enter the scintillator than are the low-energy electrons from the Moller events. Tristan is optimizing the radial extent of this pion scintillator. Initial results, however, show no real correlation between where (in azimuth) a charged article hits the scintillator and how much light the lucite PMT measured. This suggests (at least initially) that we would not gain anything by using a position-sensitive detector (i.e. a GEM) as well behind the pion detectors. This study is ongoing.

Elham finds that the detector prototype, with vertical through-going cosmics shows consistently about 30 ADC units for a peak that appears to be single PE peak. Concern is that this peak may be noise and not single PEs. However David argues that since the rate of these events increases sharply when more light is admitted (unwrapped detector in a dark box with a small hole for "light leak", compared to dark box with no hole, and to a well-wrapped detector) then this cannot be electronic noise (which would not change rate with admission of light), and so is likely the single PEs. High voltage was 1500 V. Should see if the mean value of the peak changes when high voltage is raised (max for this tube is 1650 V) or lowered. However, if we take this as the single PE peak, then the cosmic data taken with the same high voltage, same dynamic range and digitizer settings (peak value 2100 ADC units) indicates a healthy 70 PEs per muon.

Why is there no 2-PE or 3-PE peak seen in the histograms? David argues that, unlike the case for a charge-sensitive ADC which integrates the charge during an ADC gate window, the CANE digitizer will not sum the signals from two PEs that are arriving at exactly the same time, rather would simply record the pulse-height associated with the first-arriving PE, so one is very unlikely to see a 2 PE peak in a spectrum from light-leaks.

Elham/Wouter will take prototype to Mainz for beam tests in November. Dustin offers to help at Mainz.

Simona Malaca has offered to help calibrate (at Jlab) the single PE output/gain for the PMTs being used at U. Manitoba.