DC HV and Gas

90/10 ArCo2

Beam tuning

The gun voltage was turned to zero and we saw no events in the rear scintillator associated with the gun pulse. We believe there are no electrons from the cavities (Field Emission).
The gun voltage was put 0.35 and only single electrons were seen in the PMT based on looking at the scope trace.
The gun voltage was put 0.4 and saw 10% of the pulses may be multiple electrons were seen in the PMT based on looking at the scope trace.
The gun voltage was put 0.45 and saw 10% of the pulses may be multiple electrons were seen in the PMT based on looking at the scope trace.
The gun voltage was put 0.5 and saw 10% of the pulses may be multiple electrons were seen in the PMT based on looking at the scope trace.
The gun voltage was put 0.8 and started to see increase in multiple electrons were seen in the PMT based on looking at the scope trace.

Now turn the magnet in front of the scintillator to bend electrons away from the paddle.

The Trigger rate of Scintillator in coincidence with the paddle was

19:21:15 -> 19:26:44 gave 70 event => 70 events / 329 sec = 766 events/hour

Now turn the magnet in front of the scintillator to bend electrons towards the paddle.

The Trigger rate of Scintillator in coincidence with the paddle was

19:32:54 -> 19:37:16 gave 164 event => 164 events / 262 sec = 2253 events/hour

We get a factor of 3 more coincidence events with the magnet bending charged particles towards the scintillator.

Run 420: Beam 3" away from the feedthrough, Translator Motor left off

Run 421:Beam 0.25" away from the feedthrough, Translator Motor left on