MEMORANDUM

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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IRFEL Weekly Report, September 22-26, 1997

Date: September 26, 1997

Management

The official milestone date for the completion of the IR Demo construction project is next Tuesday (Sept. 30). This milestone was defined as completion of the FEL User Facility with installed FEL hardware ready for start of commissioning. On Oct. 2-3, representatives from the Navy High Energy Laser Office and the DOE Site Office will be reviewing the close-out of the construction project. The FEL project team thanks all the Jefferson staff, contractors, and collaborators who have helped us reach this important milestone. Readers of this weekly report know that some installation activities will remain after the Sept. 30 milestone, however, these tasks have been staged to not impede start-up of commissioning activities.

Highlights for this week include the first commissioning activities: the application of high voltage (420 kV) to the gun assembly. Other highlights include completion of installation of the optical chicane vacuum chambers; the first fit-up of a reverse-bend vacuum chamber; and the delivery of HeNe laser light through the drive laser optical transport system to gun cathode.

Monthly reports for the month of August for both the IR Demo project and the Demo Commissioning and Upgrade project were completed and distributed. A draft projection for the cost and schedule performance for the last month of the Demo project (September 1997) was completed in preparation for next week's project close-out review.

F. Dylla and a number of LPC collaborators attended this week's workshop (Sept. 21-24) on "Atomic, Molecular and Optical Physics" sponsored by the DOE-BES Program Office. In working sessions on low field, high field, and surface phenomena, the potential use was noted of 3rd and 4th generation light sources (including specific mention of the Jefferson Lab FEL).

On Sept. 23, Jefferson Lab hosted the Virginia Technology Council, which included discussions of continuing support of the FEL User Facility and Applied Research Center in the Commonwealth's "Technology Blueprint": being prepared by CIT and the Council.

Accelerator Systems

Regarding the beam-transport system:

Measurements continue on the Injection/Extraction dipoles. Integral readings on the first DU unit were within the one part in ten thousand specification over the good field region. The DU version of these magnets is "all ends" and shaped like a wedge. We have to refine our analysis techniques in order to create legitimate characterizations. Field integral measurements will continue over the weekend on the remainder of the available population of four magnets as Everson reglues mu metal on two DU poles that were sent back.

No more work was done on the magnetic model of the DV dipole and the 10 MeV line that is adjacent to it due to competion with the gun high voltage commissioning.

Everson shipped the four DX style reverse bends as well as the trial assembly of the 180 degree dipole (after on site inspection by Larry Turlington) while continuing gluing the mu metal and brass on pole tips on the other style of reverse bends, the DQs.

Our plan to install the trial assembly 180 degree magnet as well as two of the unmeasured DX dipoles and the pole tips from a DX and a DQ onto their respective stands in the first arc may come about next week. However, the permeability of the chamber welds became a cause of some concern. The concern temporarily halted welding on the 180 degree chambers. See below.

In the quadrupole and sextupole area, winding of coils and machining cores for the eight Panofsky trim quads reached 65% complete status at Magnet Enterprises International by week's end.

In the corrector area, manufacture of the coils for the phasing dipoles (DGs) continued at MEI with forecast completion at the end of next week. The manufacture of their mu metal cores was started at Magnetic Shield Corp. with completion forecast for 24 October. Materials are on order and tooling in design at Advance Magnet Lab (AML) for fabrication of coils for the reverse bend correctors as well as the air core correctors with completions forecast over the next two months. Two of the four sets of prototype air core correctors needed for the injector line and injector dump line were completed.

The bolted together chambers and the cross for the beam scraper composing the beam tube for the first two reverse bends were placed into position and are awaiting the magnets for a final assessment before cleaning. Welding of ends onto bodies continues on the remaining reverse bend chambers. However, magnetic measurements on two chamber bodies from the arc chambers indicated a greater effect from the weld bead than predicted by the original sample chambers at the level of three parts per ten thousand. Welding on the 180 degree chambers was temporarily halted, David Douglas is constructing a better model to forecast the effect of the magnetic anomaly and we are preparing to use non-magnetic Inconel rod on the local portions of beam tubes to eliminate the problem if David's analysis demands it.

Regarding RF systems:

The 500 kV High Voltage Power Supply and transmission line were successfully high voltage tested to 420 kV this week. The PSS interlocks for the buncher system are ready for testing. The SOP was signed this week. The RF system for the buncher is about 90% complete. The installation of the 50 kW klystron systems for the quarter cryomodule are about 90% complete. Both units were operated and generated RF into waveguide shorts. The first 225 kW variable power supply was successfully high voltage tested with a small load. The RF system for the linac is about 60 % complete. Modified software was installed and partially tested in the linac. The software changes for the Injector were implemented and tested this week.

The gun high voltage power supply was successfully operated at 420 kV for gun conditioning. We had an early failure, due to arcing, of a transmission line center conductor support rod. To correct this, we made minor changes to the rod design and covered the new rods with "Raychem" to help the surface grading. The power supply is now very stable, at least up to the 420 kV level.

For these tests we ran a gas mixture of about 85% SF6 and 15%N2.

Due to a misunderstanding, last week's report incorrectly stated that the buncher cavity was powered with RF in the FEL Facility. Instead, the buncher's RF system was powered last week into shorts. We still need to install the buncher's water skid before running it. Plans are to power the cavity with RF early next week. We are not foreseeing undue difficulties because the cavity has already been successfully operated in the Injector Test Stand.

Regarding instrumentation and control systems:

This week's activities center around the operation of the dump water skid. The instrumentation and control interlocks for all of the fixed and insertable dumps are located in rack FL07B05, in the control room. The interlocks for the skid are operational, the chassis for the three fixed and three insertable dumps will be worked on next week.

FEL Systems

Injector Reinstallation

All components for the drive laser transport are here with the exception of a mirror which will arrive next week. The high voltage power supply system is complete and being used to high voltage process the gun. Final alignment was completed on all components before the cryounit. Correctors were installed before the cryounit as well. All air and water lines before the cryounit were hooked up. A green He-Ne laser was installed to provide a local source of green light for quantum efficiency checks as well as a source for initial beamline checkout.

Wiggler

The wiggler vacuum chamber is leak tight and is being straightened. It will be ready for assembly in its support next week. All parts for the wiggler viewers are in house and the viewers are being assembled.

Optics

Work continued this week on the drive laser optical system. All mirror cans for the system are installed and all of the cans downstairs are aligned to their surveyed positions. The relay telescope has been reinstalled in its vacuum-tight enclosure. The piping between the various mirror cans should be completed tomorrow (9/27). A red He-Ne in the drive laser clean room transmitted by the OTS enters the light box, but is not centered on the photocathode. We plan to complete the alignment on Monday. A green He-Ne (Gre-He) laser was installed on the light box stand and was aligned to transmit a beam onto the photocathode. Once calibrated, this setup provides a convenient check of the photocathode quantum efficiency. The mirror cassette procurement continues, a large number of vacuum components needed to make the bodies arrived this week. The bids for the linear stages closed last week with the award given to Aerotech. Receipt is expected in 8 weeks. Procurement of insertable dump hardware began this week. We worked with I&C and Software personnel to resolve minor problems with the drive laser controls when the IOC was moved to FELSRV; this happened fairly smoothly.

The cameras monitoring the FEL optical transport system mirrors were assembled in their holders, installation will happen next week. The optics for the relay telescope were also cleaned this week, in preparation for the installation.

We hosted a visit on 9/23 by D. Denton and A. Ogloza from NAWC China Lake. They, along with members of their group, have been doing metrology on our cavity mirrors. They toured the facility, and held meetings with the FEL optics group on plans for completing metrology for our 5 and 3 micron mirrors, as well as getting cavity mirrors for high power operation at 6 microns. We also sought their advice on cavity optics for the R5 upgrade.

Commissioning/Operations

Procedures and test plans for starting up the photocathode gun, rough setup of the injector, and setup of the 10 MeV injector dump were polished and posted on the www at http://www.jlab.org/~legg/procedures/Injector_setup_proc.pdf.

The impact of off-normal performance of the injector and full linac is under further consideration because the respective electron-beam energies affect procedures for RF phasing and for setting up the electron-beam transport system. In particular, performance of the injection/extraction (DV) dipole magnets is sensitive to the cryounit performance. We are pondering how to maximize the variability of the beam-transport system for "5 mA, 42 MeV" performance in view of uncertainties in the ultimate linac performance. There is less, but not negligible, concern with "1.1 mA, 38 MeV" first-light beam.

The major commissioning activity of the week has been preparing the gun for extracting electrons off the photocathode. The high-voltage system was completed and tested, including installation of the elbow leading from the stack to the gun. The first attempt to put voltage on the gun occurred Wednesday evening (24 Sep 97). It took only 10 minutes to reach 300 kV, but at that point a large arc occurred, frying one of the G10 supports for the inner conductor in the elbow. The support was replaced and a second attempt was made Thursday evening. That attempt was successful -- the gun reached 420 kV in just 3 hours of processing. Radiation outside the roll-up door to the truck ramp leading into the accelerator vault was measured during the test. This door is presently unshielded until installation activities are complete. Consequently, we are commandeering some portable shielding for the door, and we will subsequently install a boundary rope at the head of the truck ramp to warn of potential radiation. We are prepositioning Lab resources to help with radiation protection during the upcoming cryounit and cryomodule commissioning.