Stony BrookUpdate Tent Crew Feb 26, 2008
Post-CsI, Frankenstein Stack (4,254,165) Vin=3800V Vin=3700V • Homemade lemo feedthrough was removed from gain box. • GEMs seem more stable (although not in this plot… just wait!) • “Frankenstein” stack was installed on Thursday • After continuous tripping at 3800V, voltage was lowered to 3700V for the night.
Post-CsI, Frankenstein Stack (4,254,165) Vin=3800V • On Friday, voltage was raised back to 3800V. • Bizarre: 88 trips in 3 hrs overnight… ??? (no P/T correlation) • Then relatively stable for the next 1.5 days.
Post-CsI, Frankenstein Stack (4,254,165) • On Sunday a final test was initiated at 3800V. • 0 trips in 20 hours. • Installed in WS4 Monday afternoon.
Reminder • The second-to-last CsI deposition was one we wanted to keep an eye on. • 25% decrease in WN4 after CsI was evaporated • (although the QE test looked just fine)
An interesting observation… • While there was no other stack from that evaporation that didn’t develop a short, there was one other stack that we were able to test before it went bad. • This other stack also showed ~25% lower gain. • pre-CsI(dV=511V) ~11000, post-CsI(dV=511V) ~8000. • Was something wrong with this evaporation???
Status • After removing the homemade lemo feedthrough from the gain test box, stacks are stable again. • “Frankenstein” stack (4,254,165) installed, WS4. • Test stack #12 was stable late yesterday evening @ 3800V • Currently undergoing gain test. • On the only two stacks from Evaporation “shot 308” that were tested, both showed ~25% drop in gain. • All other stacks from all other shots have a post-CsI gain ~30000. • Is this a cause for concern???