IAC 1-7-08

Accelerator: 100 ns, 60 Hz, 15 MeV

Configuration: Collimated rear scint + 2" Aluminum brick

Rates:

Coinc both PMTs =484/4min = 121/min

PMT Coinc Both PMTs & DC =25/4min = 6/min

Configuration: Collimated rear scint

Rates:

PMT Coinc both PMTs = 308/2min = 154/min

PMT Coinc Both PMTs & DC =17/2min = 8/min

The ratio of double/triple =36/1054 = 3.1%

Configuration: Collimated rear scint+ 2" Aluminum brick + 2" lead brick

Rates:

PMT Coinc both PMTs=105/10min = 10/min

PMT Coinc Both PMTs & DC =4/10min = 0.5/min

We see a lot of events in the Scintillator and very few in the Chamber. There is no clear electron signal so let's debug the beamline.

Our tests on Friday showed that inserting an Aluminum brick in front of our first collimator decreased the first scintillator's count rate by approximately 60 %. A 15 MeV electron should stop in 2cm of Aluminum. We believe our 2" (5 cm) thick Aluminum brick will stop electrons but not photons. We do not observed the same change in rate when we insert the Aluminum brick in front of the rear scintillator. We believe our collimation system is blocking most of the electrons.

We will move the Aluminum brick in front of the first scintillator. Rates:

First PMT singles =min = /min

PMT Coinc Both PMTs & DC =min = /min

Aluminum block in front of first scintillator between experimental side wall and large scintillator.

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