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.