The RF control module for the drive laser was removed and is being calibrated. Differences were noted with a replacement unit and will be checked. The software installation was finished and tested for automatic arc detector testing.

IOCs were rebooted to install bug fixes and new features.

Alignment was completed on the 0G region and will be completed on the 3F and 5F regions on Monday.

Commissioning Activities

To take full advantage of the availability of people to complete the entire vacuum system for the FEL, we did not run electron beam this week. By week's end, the entire machine was under vacuum, and numerous installation activities were completed (see above). One can no longer walk through the beamline! We also heat treated the photocathode this week and subsequently subjected it to high-voltage processing and recesiation. All seemed to go well, but at this writing (1500, 26 Jun 98) the final state of the cathode was unknown. It is a matter of concern in principle because the last two heat treatments contaminated the cathode and resulted in the need to replace the wafer, a process that takes two weeks. Yet, the need for a good heat-treatment procedure cannot be circumvented because the cathode must periodically be rejuvenated.

Regarding matters of commissioning, we spent a good fraction of the week planning how to attempt kilowatt operation this summer. Our foremost goal during the summer will be to achieve the kilowatt, and we will interleave the associated commissioning activities with a nominal effort to support user experiments. The top-level elements of the approach are:
-Optimize lasing at 5 µm (commission laser diagnostics; do first user experiment -- thought to be the Shinn/ODU experiment in that it accepts 5 µm wavelength),
-Choose wavelength for kW operation (probably 3.2 µm for Armco Metals experiment; also, it is easier to recirculate with higher-energy electron beam),
-Interleave recirculation/energy recovery with user experiment(s).
Though the matter remains to be sorted out later, preliminary thinking is to set the electron beam at higher energy, about 47 MeV, to support 3.2 µm lasing, and recirculate at that energy, typically with the laser turned on. Plans are to explore the implications by doing a couple of shifts of electron-beam energy scans with the linac to see what complications might arise. For example, it might be prudent to remove the wiggler for initial attempts at setting up the electron beam and recirculating. If so, both removal and reinstallation of the wiggler each only takes 2-3 hours.

Once the electron beam is set up, commissioning of the recirculation arc and energy recovery will proceed generally in pulsed mode with 60 pC bunch charge. Initially the process will involve 18.7 MHz beam, after which the frequency will be doubled to the full 37.4 MHz, corresponding in cw mode to 2.2 mA average current. Finally, the bunch charge will be raised until kilowatt lasing is