14 MeV photons

We are sending 14 MeV phtoton through a 4" thick brick wall collimator. A 4" Al brick in front of the HRRL exit port is used as a FC.

FC: 223B2 NaI: 223B5 Acc Gate: 223B8 GEMtrig: 223B3

Vdrift= 3700 Volt

VGem=3400 IGem=815 microA

The scope trace below shows output when electron beam current is 18 mA.

The scope trace below shows output when electron beam current is 36 mA.

The scope trace below shows output when electron beam current is 9 mA.

Now Max Gain on GEM

Vdrift= 3800 Volt

VGem=3500 IGem=841 microA

The scope trace below shows output when electron beam current is 9 mA.

The scope trace below shows output when electron beam current is 4 mA.

10 MeV photons

The scope trace below shows output when electron beam current is 20 mA.

Peak amplitude is same but rate is much lower