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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, January 18-22, 1999

Date: January 22, 1999

Management

Jefferson Lab made its pitch to the DOE-BES "Panel on Novel and Coherent Light Sources" held this week in Gaithersburg, MD. The panel has been asked to make its recommendations on the priorities for advanced light source development to DOE on Feb. 24th. The FEL team appreciates the support that was provided by Bill Cooke (CWM), Kevin Lehmann (Princeton) and Len Feldman (Vanderbilt) for their presentations to the panel.

By invitation, C. Bohn gave a presentation on the commissioning of JLab's FEL to the accelerator staff of Rossendorf Laboratory, Dresden, Germany. Rossendorf is just beginning the process of building a superconducting FEL conceptually like our straight-ahead machine. Bohn provided advice on their design and also checked on the status of the superconducting rf gun, the development of which Rossendorf is coordinating.

FEL Installation/Maintenance Activities

The following maintenance items were completed this week:

The gun was vacuum-baked after replacement of the photocathode. It is ready for high-voltage processing and cesiation which are scheduled to take place the first part of next week. The drive- laser pulse controller was modified to enable production of 75 MHz beam. It will permit us to reach an average cw current of 4.4 mA with 60 pC pulses, thereby providing a perhaps expeditious path toward higher FEL power.

All four beam-current-monitor cavities were tuned.

Metal screens have been installed on the cryomodule infrared sensors to keep rf from higher- order-modes from causing the detectors to fault erroneously. The cryomodule had to be warmed to room temperature to permit installation of the screens; it is presently being cooled back down to 2 K.

Resistors have been added to the straight-ahead and energy-recovery dumps to provide current signals during pulsed operation.

FEL Commissioning Activities

Regarding the status of both hardware and software tasks during the January down, basically the MUSTs either are, or will be, complete by early next week, and many of the SHOULDs and LIKEs will also be done. Collectively they should make further commissioning easier. Some examples include: the addition of a software screen that will provide beam current at both the straight-ahead and energy-recovery dumps and at the first beam-current-monitor cavity, both for pulsed and cw beam. Consequently we should be able to identify easily the presence of beam loss, and to some extent isolate its location. We can now run 75 MHz beam, control the new beam viewers, see the recirculated beam more clearly after the cryomodule, do a Golden Orbit Save/Restore, and we have a more capable AMS, just to name some of the key accomplishments.

D. Douglas not only revised the "High-Power Setup Metaprocedure", but he also wrote a new "FEL Driver Recovery Procedure/Optimization Test Plan" as a guide to recovering the "15 Dec 98" machine. Upon resumption of commissioning, the strategy is to recover the Dec machine and then work from there to get rid of beam loss in the reinjection region.

In addition, G. Biallas, with the aid of an "Injector Setup Team", has formulated a systematic plan for improving the injector setup. We will invoke the plan if and when we have difficulty pushing up the average current. In the meantime, Biallas and company will continue to flesh out the details.