Minutes of FEL Gun Committee Meeting

Thursday, 10 Dec 98
Recorder: C. Bohn

Next Meeting


Date: 17 Dec 98
Time: 1500-1600
Place: FEL Facility Break Room

Agenda for Next Meeting


Group activity to schedule tasks for planned January wafer change-out.

This Week's Attendees


C. Bohn, J. Fugitt, J. Gubeli, K. Jordan, G. Neil, L. Phillips, T. Siggins

Discussion


The bulk of the meeting was dedicated to reviewing wafer history data. T. Siggins presented the data from two successful wafers dating back to early this year. One was not anodized, and the other was anodized. Siggins' notation and presentation of the histories was concise, clear, and well done. He will continue by looking at the histories of other wafers.

The general trend suggested by the data presented is that high-voltage processing needs to be done not at ~420 kV, as was done on these early cathodes with, at best, mixed success, but rather at ~500 kV, as done on recent cathodes with apparent success. Also, the early histories reflect inconsistency in the choice of HV-processing voltage; it was "hunt and peck". The final version of our HV Processing Procedure needs to rectify this matter and provide guidance on when specifically to stop ramping up the processing voltage.

The second main topic of discussion was a presentation by J. Gubeli and K. Jordan concerning the status of the cathode scanner. The software now permits use of the mouse to decipher quantum efficiency and current versus position on a given scan pattern. The current has been calibrated, and the QE is derived from the current. Gubeli and Jordan are now considering how to set up to do remote scans, i.e., without having to enter the FEL vault. An interesting observation from scans of the present wafer: they reflect no evidence of degradation at the location of the drive-laser spot despite the many hours of cw runs done with fixed DL spot location. This cathode scanner is good work!

Lastly, the Committee considered a memo on "Near-Term Improvements to the Present FEL Gun" provided by C. Sinclair, who was unable to attend. Bohn will have the memo distributed to all Committee members.

Closed Action Items


New Action Items


Old Action Items