To: J. Cook, D. Helms, W. Skinner

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, September 14-18, 1998

Date: September 18, 1998

Management

This week was devoted to completion of maintenance activities and start-up of system check-out for operation. Highlights for the week include: (1) completion of the bakeout and imminent start (Saturday a.m.) of HV conditioning of the photogun; (2) successful checkout of the new beam viewers in the east recirculation arc.

The laboratory hosted the annual SURA/DOE review of JLab's science and technology programs on Sept. 15-17. A review of the status of the FEL project and a summary of near term user applications was presented. The review committee included representatives from the nuclear physics, accelerator physics, light source and materials science communities. The FEL project was given excellent marks by the committee, a result which should help the on-going funding initiatives.

FEL Installation/Maintenance Activities

Work on the FEL systems this week included installation of a low power pickoff on the FEL beam to allow for calibration of the optical transport losses. The optical collimator was cleaned, two non-functional picomotors were replaced, and the system realigned and pumped down. The alignment of the optical cavity fiducials was reset and the position of the OTR apertures in the wiggler readjusted. Finally the wiggler itself was moved by 250 microns to bring it in line with the magnetic quadrupoles. Measurements of the high power 3 micron mirrors are underway at China Lake.

The following additional tasks were completed this week:

Installed a photo diode in the light box for the drive laser stabilities studies.

Provided a two-button "close-all" vacuum valve capability and a display of vacuum valves pending requests to the control system.

A new digital input CMAC card was installed in zone 2 to monitor the 8 kW klystrons.

The Digitel ion pump readouts (in torr) were added to the vacuum screens in the control system.

A one-button unmask command for all BLMs was added to the software.

A BLM was added for the beam scrapper.

FEL Commissioning Activities

The gun was baked this week. This morning (Friday, 18 Sept. 98) it is being configured for high-voltage processing, which should start early tomorrow (Saturday) morning and last through the weekend. Plans are carefully to ramp up the voltage to 420 kV and let the gun soak for many hours at that voltage. Hot system checks will also begin this afternoon once the vault is in Beam Permit.

As presently envisioned, on Monday Day Shift the cathode will undergo heat treatment and cesiation, the drive laser will be aligned, and final hot system checks will be done. Injector setup and checkout will follow over the next three shifts. Straight-ahead cw lasing is slated for Tuesday Swing Shift to check the setup and to calibrate losses in the optical transport system. Subsequent activities will focus on systematically working through the augmented High-Power Setup Procedure that was finalized this week.

During this extended shutdown, the principal hardware updates that bear on commissioning consist of: configuring the viewers in the 180-degree dipole magnets so that they now work; installing two new viewers in the second recirculation arc; installing the beam scraper in the first recirculation arc; modifying various drive-laser subsystems for increased power and better stability of low-power rf; adjusting the 60 Hz raster magnets in the injector and energy-recovery dump lines (the raster currents will need to be reset prior to going cw); and upgrading the gun for increased pumping speed, faster baking, improved heating of the cesiator, and faster exchange of the conditioning and running resistors. All of these upgrades should prove useful in the coming weeks. In addition, there have been numerous updates to the software to accommodate the new hardware on the control screens as well as to make the Analog Monitoring System functional. The latter will be commissioned as we renew our running the FEL.

A meeting was held yesterday (17 Sept. 98) to discuss plans for a beam-breakup experiment that will benchmark the code TDBBU so we can have more confidence about designs of future FEL upgrades for higher-power light. Plans were made to check the compatibility of available beam-kicker and pickup hardware with the existing beamline configuration. Based on the findings, a more detailed plan of the experiment will be formulated, and eventually the effort will be presented to Accelerator Division management for formal approval as a FY99 task.