Highlights for the week include another round of gun high voltage processing (adding to our database) and a good start on the analysis of scenario plans for staging the upgrade.

The Laser Safety System for User Lab 3 (the "Metals Lab") was checked out last week; punch-list items were rectified this week. Final certification awaits delivery of a laser beam.

A camera and shutter were installed on the upstream table to image the spontaneous radiation from the center of the wiggler reimaged back to the wiggler center from the downstream mirror.

In last week's report, another round of high-voltage processing of the gun was documented. As stated, the gun was processed to 430 kV with the cathode retracted into the stalk to preserve its quantum efficiency. A scan late last Friday of the cesiated cathode did indeed show a "good" (~2%) quantum efficiency and a low red-to-white-light response indicative of a clean wafer.

On Monday we attempted to raise the gun to 330 kV. Unfortunately, we were unsuccessful, as the gun began field-emitting copiously at around 250 kV. This is consistent with the two most recent wafers that we had tried processing to 430 kV (as opposed to >500 kV) with the cathode inserted; these "guns" also field-emitted at ~250 kV. So, there is "good news" that the field- emission behavior is reproducible. Likewise, there is bad news that it is completely unacceptable.

Upon Monday's failure, we decided to revert back to our now-canonical procedure of processing the gun to 520 kV (for quiet behavior at 510 kV), then doing a long heat clean of the wafer (8 hours at 675 C), and then recesiating. Processing proceeded slowly all week. At this writing (1145 Friday, 7 May 99), processing is continuing and should be complete by the end of the day. On Monday we will cesiate and try again to bring the gun to 330 kV. If we get somewhere between ~260-330 kV, we will try to set up good beam and run. Hopefully the quantum efficiency will be adequate to support an attempt to lase at 1 kW; the fact that we have more drive-laser power now (6 W vs. 4.5 W earlier) is a help.

On another front, we worked toward crystallizing our thinking concerning the FEL Upgrade. We sketched out defensible plans both in the case that we proceed incrementally in parallel with incremental funding, or in the case that we go directly to a 10 kW-level device in parallel with lump-sum funding. In either case, gun improvements would proceed from the beginning, and a comprehensive user program would be sustained.