[Tgun] [Revised Logentry] Cathode problems updated - errata

[fhannon at jlab.org]

Logentry Text:
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We have continued to look at the cathode issue. The filament is not shorted - cold - it reads the same resistance as the spare = 1 Ohm. Good news. We put the power supply on it as per instructions, it gets to 6V and ~1.5A as we were before. Resistance changes with heat - so this makes sense. We can see the edge of the cathode through the beam port in the solenoid and see it glowing yellow. All good.

However, when we look at the grid - it is grounded. We checked this with the plug and by inserting a metal rod and just touching the grid contact. So the logical thing is to assume the grid is at ground - and float the filament supply negative to a voltage that pulls current when its on. This didn't work. When we activated the cathode, 3V was enough to see 150mA current. we went to -6V and saw nothing.

I'll change previous entries to reflect errors


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