[Tgun] [New Logentry] T-Gun Cathode Activation

[mstefani at jlab.org]

Logentry Text:
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The cathode activation process was completed as described by the activation schedule we received for YU-171 cathode. Note: All cathodes follow the same activation schedule. Initial Pressure was 1.9e-9 torr. Well below the required 1e-7 torr. increasing voltage in 0.5 V increments in 15 minute intervals caused the desired out-gassing with vacuum peaking around 2.2e-7 torr  between 3-5 V. Beyond this applied voltage the pressure began dropping eventually reaching 1.6e-8 torr range indicating the cathode is out-gassed. 

the cathode the"aged" for 30 minutes at 6.5 V as prescribed in the activation schedule.

Applying -3 V bias on the cathode, with the grid being grounded, did produce the predicated 50 mA of current and this was held for 15 minutes as prescribed in the activation schedule.

The cathode bias was then set to -6 V to produce 150 mA and held for 30 minutes. 

Following this the applied voltage to the heater was lowered to test the threshold of emission without high voltage and it was found that at values below 6.2 V the emission from the cathode dropped.




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