MEMORANDUM

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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, January 12-16, 1998

Date: January 16, 1998

Management

On Jan. 14-15, the Laboratory hosted the first Laser Processing Workshop for 1998. The workshop was attended by 84 partcipants representing 18 universities, 11 industries, NRL, NASA, BNL, DOE and local government. The agenda included an update on the machine status, facility operation planning, upgrade planning, reports from the user working groups on user lab equipment, and reports on collaborative activities with BNL and NASA. The primary focus of the workshop was a series of presentations from teams who have submitted proposals to DOE-BES for basic science applications of the FEL.

On Friday, Jan. 16, Alex Flint and David Gwaltney from the Senate Energy and Water Resources Committee visited the laboratory for a briefing and tour of the laboratory's nuclear physics and FEL programs.

Next week, Fred Bomse from CNA (the Center for Naval Analysis) plans to visit the labortatory for discussions on FEL technology.

Installation Activities

The first 2 reverse bend chambers were installed with the DQ magnets in the west arc, 3F region. for fit-up. Vacuum connections will be made when labor is available.

The electrical leakage path in the straight ahead dump, 2G region, was found and corrected.

RF software is still being modified to make the Injector more robust. The new code is planned to be tested early next week.

Due to higher priorities to modify CEBAF magnet power supplies, testing to find two 8 kW klystrons and a spare for the FEL cryomodule was delayed. After installation, all 8 kW klystrons will be conditioned to 14 kV.

The last DV magnet was delivered to the vault and is ready for installation.

The warm windows on the cryounit have been replaced to allow up to 40 kW of RF power.

The alignment of the cryounit was checked and found to be only about 1 mm high, but an internal valve was found not to be fully open. This may solve the alignment problem that was found earlier with the beam. (See detailed comments below).

The gun cathode was hydrogen cleaned with a mask in place. A bake cycle on the gun was started and will finish early next week.

Many of the cables to control the optical cavities were completed this week. Final testing will be done when the hardware is in place.

The controls for the raster magnet for the Injector dump, 0G, is in checkout.

Commissioning Activities

We made considerable progress on the key tasks that are preparatory to resumption of commissioning. These include the following:

- Prepare for commissioning from the Machine Control Center: MCC operators are projected to turn on CEBAF starting 5 Feb 98. In view of their likely intense activities on CEBAF itself, these operators probably will not be available to the FEL prior to mid-February, but this conclusion is pending success with the main-machine turn-on. Thus, upon resumption of FEL commissioning activities, we expect to operate without augmentation from CEBAF operators. Hardware for the MCC (two workstations and a video system) is still projected to be installed prior to 26 Jan 98.

- Align Injector Components: The cryounit alignment has been verified to be good to within 1 mm, both with respect to the cryostat itself, and with respect to the alignment of the cavities, including tilt, inside the cryostat. However, an internal valve was not completely closed, subtending into the beam aperture a distance somewhere between 0.95 cm and 1.1 cm. During the December runs, this necessitated steering around the blockage, and presently it is thought that the concomitant beam "misalignment" was responsible for the observed distortion of the beam's transverse phase space.

- Complete the Machine Protection System for First Light: Remaining is the need to interface the defocusing quads and raster magnets and finish instrumenting the dumps. Current estimates are that the MPS necessary to run 1.1 mA cw in the injection line to the 0G dump will be in place by month's end, and that needed to run 1.1 mA cw to the straight-ahead (2G) dump will be in place by mid-February, both commensurate with the commissioning schedule.

- Complete First-Light Magnet Field Maps: The field maps in question pertain to the QB and QG quadrupoles. Generic field maps for both are in hand but need to be installed. Their installation is programmed for timely completion.

- Complete Preparations of First-Light Beam Position Monitors: The 4-channel BPMs are certified to be accurate at the 0.1-mm level with 60 pC bunches. They will not be as accurate with 1 pC bunches, for which they can be used as peg points with 0.5-mm-level accuracy. A software rewrite has been done respective to the SEE BPMs (on schedule) that will enable inputting their correct calibration curves.

- Finish and Install Bunch-Length Monitors: Uwe Happek's (Univ. of Georgia) student will be here in early February to do checkout. The student wrote the software for the bunch-length monitors. Their stands are installed, and their boxes are ready, but we don't yet have confirmation from Happek himself that the interferometers will be here soon. We are trying to close this loop.

We began a focused activity to develop strategies for optimizing injector beam quality. The motivation was the high transverse emittance, exceeding 20 mm-mrad, measured on the last shift prior to December shutdown. As noted above, the cause of the bad emittance might have been the valve internal to the cryounit, but the need for an optimization procedure exists nonetheless. The basic plan is 3-fold:

1. Finish alignment checkout (results of which are discussed above),

2. Codify the existing collection of 3D PARMELA runs, of which there is an extensive set of "9,11 MV/m" runs,

3. Set up the injector using the procedures already written, but incorporate adjustments as necessary based on inferences from 1 and 2 above.

Regarding 2, with the installation of new warm windows on the injector cryounit, we probably will be able to run with the "old" nominal cavity gradients of 9 MV/m in the first cavity and 11 MV/m in the second, and so the past runs are useful for planning purposes. Sensitive "knobs" available for 3 above include the solenoids at the gun (especially the first one), the buncher phase (combined with the cryounit cavity phases), the beam spot size, and the cavity gradients. It could conceivably be useful, as a troubleshooting guide, to turn off cavity 1 or 2, successively, and measure the transverse emittance with the multislit diagnostic. Perhaps this would tie undue emittance growth, if it were observed, to one of the cavities. We also could try a solenoid scan in front of the cryounit to check beam quality there, but this technique is probably good only for "zero" bunch charge. This planning activity will continue.