MEMORANDUM

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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, November 3-7, 1997

Date: November 7, 1997

Management

A status report on the FEL Program was given to SURA New and Ongoing Projects Committee at the Fall Meeting of the SURA Board of Trustees held at Vanderbilt University on 5-6 Nov. 97. A request for proposals for experimentation with the IR Demo FEL was extended to university members of SURA. Following the SURA Board Meeting on 7 Nov., a series of meetings was held with various members of the Vanderbilt FEL Center to continue discussion of the joint proposals which are being prepared with several faculty members of Vanderbilt's Physics Department.

Joe Heyman, who heads NASA Langley's Technology Applications Group, visited Jefferson Laboratory on 3 Nov. 97 to discuss NASA participation in the FEL User Facility. A follow-up meeting was set-up for 20 Nov. 97 that will include participation by the heads of the NASA- Langley Divisions of Materials Research, Structure, and Atmospheric Sciences.

Installation Activities

The RF system for the cryomodule was tested and placed in the Personnel Safety System this week, and the waveguides to the cryomodule are being installed this afternoon (7 Nov. 97). Work should be finished this weekend, after which the RF system will be ready to support SRF commissioning of the cryomodule.

The 3 DU dipole magnets for the injection line were mechanically adjusted, hooked up, and powered to 50 A. Additional DU dipoles have been released and are being installed.

As of noon today (7 Nov. 97), the wiggler vacuum chamber was in process of being installed.

Modifications of the low-conductivity-water system, flow restrictors, and electrical isolation for the injector and recirculation dumps were completed.

Commissioning Activities

The leaky vacuum seal for the RF warm window in the cryounit was replaced, and the cryounit was successfully cooled down on Tuesday, 4 Nov. 97. SRF commissioning subsequently commenced. As of this writing (1315, 7 Nov. 97), the exit cavity has been operated at cw gradient in the range 8.0-8.7 MV/m, and at 10.5 MV/m pulsed. CW performance is limited by the IR interlock, and some consideration is being given to whether the IR fault limit should be set less conservatively. Plans are imminently to operate the entrance cavity and determine its maximum useful gradient. There is a possibility that the cavities can be run at, e.g., 12 MV/m and 8 MV/m for the entrance and exit cavity, respectively, rather than the 11 MV/m and 9 MV/m gradients that had been projected based on results from earlier off-line tests in the Injector Test Stand. PARMELA modeling is underway to support SRF commissioning and help determine whether resetting the IR interlock limit is necessary. An ancillary activity was operation of both 50 kW klystrons to supply RF power to the cryounit.

Other commissioning highlights this week include: Vacuum processing of the buncher cavity took place, during which it was operated to 3 kW. A training video was made showing operator screens used to transport beam from the gun to the first viewer. The procedure "Cryomodule Setup -- Set Cavities to Nominal Gradient" was finalized, and the procedure "Beam Transport Setup from Cryomodule to First-Light Dump" was drafted.

Two issues regarding magnet performance are being worked:

- Field measurements of the reverse-bend (DQ) dipoles indicate that they provide a working aperture that is too small, roughly a four-inch good-field region as opposed to the desired eight inches. DIMAD analysis shows consequent orbit variations in the off-momentum beam at the several-percent level, which may or may not prove troublesome during FEL operation, but which should be corrected as far as is reasonable. We are in the process of developing a viable plan in light of the results.

- TOSCA modeling of the injection/extraction (DV) dipoles is ongoing to resolve how to counter unwanted fringe fields across the Y-chambers, but progress has been slower than anticipated. The issue must be resolved within two weeks to support getting tune-up beam to the first-light dump before Christmas. This could conceivably be facilitated by, for example, symmetrizing the DV's field clamp and using a corrector to counter remanent fringe fields. Work is in progress to devise a strategy.