MEMORANDUM

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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IRFEL Weekly Report, March 31-April 4, 1997

Date: April 4, 1997

Management

At Senator Warner's request, a briefing on the Jefferson Lab FEL Project was held on 1 April for staff members from the Virginia congressional delegation and several staff members from the Senate and House Defense Authorization Committees. D. Barnes, Adm. Baciocco (MTAC Chair) and F. Dylla gave brief presentations on the present project, planned upgrades, and the recent MTAC Review of the project.

Initial plans were made for the Navy Program Office review of the project which will be held on 15 April 1997. WBS managers will provide summary sheets of the present status and open issues with respect to the WBS deliverables during tours of the project hardware in the Test Lab, CHL and FEL Buildings. The tour will be followed by a management wrap-up of cost and schedule based on the March project data.

A draft flow chart was prepared delineating responsibilities among Accelerator Division groups for commissioning the IR FEL. The chart and a proposed list of principal investigators for implementation of the commissioning test plans will be reviewed over the next several weeks by Division management.

Key activities this week included startup of bakeout activities of the photocathode gun and beamline in the Injector Test Stand, successful completion of a review of the PSS/LSS systems, further analysis of the critical-path tasks in electron-beam-transport hardware, and FEL Facility installation activities.

Injector Test Stand

The photocathode gun and beamline was configured for bake-out and is now baking. In addition, the injector cryounit was cooled down and filled with 2 K liquid in the ITS cave. Checkout of systems is underway to support off-line commissioning of the cryounit. The software for the cryounit has been completely upgraded and tested with interlocks. A new feature was added so the rf module can track the high-power amplifier when it is in the "local" control mode of operation. This will enable us to switch between "local" and "remote" control modes without having to go back to the "idle" state and then wait 10 minutes for the filaments to heat up again. Also, with all interlocks properly made, the cryounit will be able to progress to the "rf on" state with a single command.

The drive laser's lamps were replaced. A few minutes after start up, one shattered. Fortunately, only one piece separated from the lamp envelope, and it was recovered after some effort. The laser output is stable with the new lamps. A new camera mount that bolts onto the gun, rather than being placed on a tripod, was tested and found to be satisfactory. Our Machine Shop fabricated several parts needed for resumed operation of the gun.

Accelerator Systems

Regarding the beam-transport system:

Fabrication of the optical-chicane dipole magnets started in earnest. The first layer of coil was wound at Magnet Enterprises International. A trip to view the first article is planned for 14 Apr 97, one week ahead of schedule. Everson Electric has cut the steel we supplied them into the pieces needed for production, and is aiming for a first-article core by 18 Apr 97.

Magnet Enterprises International won the bid for coils for the 180-degree and reverse-bend dipoles, promising 11 and 10 week deliveries, respectively, which are considerably better than the requested 16 and 12 week deliveries, respectively, and we placed the contract with them. Bidders for the cores were given one more day because of some questions that had to be cleared up. Contract award for the cores is slated for early next week.

Bids for the injection-chicane dipoles are due 11 Apr 97.

We have had difficulty deconvolving the magnetic measurement data on the rectangular-style prototype trim quadrupole. After a last try today (4 Apr 97), we will decide on an action plan that may revert to a more easily characterized square Panofsky-style quad with field clamps.

Hospitalization of the designated designer prevented bringing the sextupole drawing package up to production grade. An alternate designer, who drew the original prototype drawings, will take over, but we have lost a week.

Specifications for the field quality of the air-core correctors are more stringent than can be obtained with the simple ski-end-style coils used in the nuclear-physics machine. We are planning some magnetostatic calculations to obtain the required field accuracy at the first try without a series of prototype cycles. This task might not be as simple as once believed. Design of these magnets has been placed at the end because they are simply installed over the preinstalled beam tubes, but it looks like the designs will come in just under the wire.

Multipole measurements on the six QB quadrupoles retrieved from the nuclear-physics machine were planned so that the quads could be mounted to the optical-chicane girders. At the same time four more QG quads arrived to bring the total received to 16 of the 22 ordered.

We requested final pricing details for the power supplies that will drive the injection/extraction dipoles given their simpler 50 V requirement. Contract award awaits the vendor's reply. The first of the upgraded power supplies for the nuclear-physics machine went through a trial run. This is noteworthy because their installation will free up two supplies as surplus for use in the FEL. Delivery of the second supply was authorized. The three shunts necessary for the dipole strings are being assembled. Work on the temperature-switch chassis was delayed by higher-priority work, but it is being reassigned.

In the vacuum area, layout of the chambers for the optical-chicane dipoles is complete, and the chambers are ready for detailing. The design concept for the reverse-bend chambers is being readied. The requisition for vacuum pumps was sent to our Procurement Department as a sole- source purchase. Delivery is expected in six weeks. Design of the chambers for the 180-degree dipoles is nearing sign-off.

Parts were received for the X-chamber that connects the injection line to the recirculation loop. Bids were received on the Y-chamber that leads to the recirculation dump. Design continued on the remaining stands, brackets, and girders needed in the injection line and dump. Contracts are near award point for stands and girders needed for first light and for back-leg girders. Stands originally bound for the 10 MeV Injector Test Stand dump were sent to the shop for modification to accommodate the FEL Facility's lower 27-inch beam height.

Purchase was authorized for the magnet-measurement system based on a rotating-coil probe that is described below under "Operations/Commissioning".

Regarding cryomodule fabrication:

We continued assembly of the first cryounit and cavity pair for the cryomodule, and this assembly is progressing on track. The second cavity pair underwent testing in the Vertical Test Assembly but failed acceptance criteria. It is being retested today (4 Apr 97) but almost certainly will have to be reprocessed. Cryounit shield #3 has been received from the vendor and initial inspection results are positive. The shields we received to date have been excellent.

Regarding electron-beam instrumentation and controls (I&C):

The combined review of Personnel Safety System and Laser Safety System was held on 1-2 Apr. A very favorable report was issued. The most important concern identified by the Review Committee was the containment of the high-power FEL beam within the optical labs. The draft report of the Review Committee lists several detailed recommendations, all of which are straightforward to implement.

Enclosures for charge-coupled-device (CCD) cameras are being fabricated in our Machine Shop. They use a high-resolution but low-cost "bare board" camera. We will simply replace these boards were they to become damaged by radiation. Also, the CCD camera lenses and spacers arrived.

The button beam-position monitors arrived. They are now awaiting vacuum chamber design and

fabrication.

The video multiplexers have arrived from Hewlett-Packard. They are 4:1 multiplexers that will be used to distribute video signals in the Machine Control Center as well as in the FEL Facility control room.

The racks in the FEL Facility have been moved to their approximate final location and have been labeled. Work has begun on setting the racks up for the control chassis.

Regarding rf systems:

The 1427 MHz drive amplifier originally envisioned for the master-oscillator (MO) system cannot be ready for installation this summer. Instead we decided to purchase an amplifier that will satisfy IRFEL requirements, and then either build or purchase a higher-power amplifier when we upgrade the machine. This will save about 20 k$ now and keep us on schedule. Specifically, the amplifier will be an "off-the-shelf" design with about 30-day delivery time. The MO distribution cables supporting the full suite of three cryomodules will be installed on the low-contamination-water lines this spring.

An aluminum rack base for the 8 klystron high-power amplifier (HPA) is in fabrication for delivery next week. This will allow cables to pass freely between the HPA and low-level racks.


FEL Systems

Wiggler

Detailed drawings for the wiggler vacuum chamber and its support are being checked. The final assembly drawings for the wiggler support are nearly complete.

Optics

We placed orders for all vacuum hardware needed for the mirror cans. A procurement request for the fabrication of the mirror cans is out for budgetary estimates and should be awarded soon. Small optical rails are being installed in the accelerator enclosure near the mirror-can positions to aid alignment of the transport pipe. A mirror mount with New Focus picomotors (the stepper motor we plan to use in the optical-transport mirror cans), arrived and will be given to our Software Group so an EPICS driver can be written for it.

Optical diagnostics progressed with an order placed for the vacuum components for the Brewster-window pick-off that will be used as part of optical control. The fabricated parts are being built by the Jefferson Lab Machine Shop. A designer was hired this week, so we'll begin formal design activities next week. Having received some new parts, the optical-cavity components are coming together. We plan to give the downstream assembly containing the gimbal mounts, the linear stage, and the linear variable differential transformers to the software engineer by mid-month to permit testing the controls software.

Work continued on the optical interferometer to validate the sensitivity and control available on our cavity-length diagnostic. Early results look promising.

Operations/Commissioning

Additional simulation results from 350 kV gun up to the wiggler were generated. We now have simulations for a "long gun" (spacer in place) for first light (60 pC), and a "short gun" (spacer removed, as in the new gun configuration now in the ITS) for full-power operation (135 pC). The second cryounit cavity needs to be operated off-crest to get the target transverse emittance. There are, however, two puzzling results. First, there is large emittance growth in the cryomodule for unknown reasons (but the target emittance of 13 mm-mrad for full-power operation is achieved). The degradation seems to be sensitively dependent on the beam shape at the entrance to the cryomodule. Skew quads were ignored; including them may help. Second, the PARMELA space-charge code doesn't seem to simulate transport through bending magnets correctly. Its results with space charge turned off disagree significantly with DIMAD, again for unknown reasons. Plans are to examine other machine settings that give a more favorable beam shape entering the cryomodule and thereby reduce the emittance degradation in the cryomodule.

Detailed plans were developed for putting the Accelerator Readiness Review (ARR) process on the www. The basic idea is to have just one ARR sometime around Jan 98. Web pages have been drafted, and they include prompts for inputs from line managers (usually WBS managers) concerning whether all required resources, both hardware and people, are available. It will take about a month to get the material on www. Our next step is formally to approach the DOE site office for approval of the strategy. We already have done so informally.

We decided to procure a self-calibrating system based on a rotating-coil probe for use in nulling the dipoles at the switch points leading to the injector dump and the straight-ahead dump, as well as for field measurement at the recirculation-dump-chicane dipole needed for energy calibration of the cavities. Interface to the control system is the next step.

Facility

Work in the FEL Facility continued at a rapid pace except for Monday and Tuesday when high winds forced a curtailment of some effort on the roof and exterior walls. Roofing was two-thirds complete by the end of the week. Exterior panels were placed completing the south wall. Work is proceeding on enclosing the utility room (a key step since its enclosure will allow us to hook up power downstairs). Wall bases were being set along the north wall. Inside the second floor the HVAC ducting was having the vents cut in and preparations made for hookup of the compressor units. Chilled water piping is >50% complete around the interior. Studs were being placed for the interior lab walls. The area around the electrical switchgear was drywalled so that switchgear placement and hookup of the electrical circuitry can begin. The roof drains were >80% complete. Many door frames and window frames were set in position. Jefferson Lab crews set survey monuments upstairs. Downstairs the welding of the helium transfer lines is proceeding as planned. An interfering sprinkler line was moved out of the way of the optical-transport line. A tour of the Facility was held by the Personnel Safety System Design Review Committee. A couple of issues regarding oxygen-deficiency-hazard safety were identified: a lintel needs to be installed at the exit stair, and the HVAC ducting needs to be examined regarding its performance during a helium incident. We will deal with these in the coming weeks. The contractor for the photocathode drive laser clean room came for a site review. Several installation issues were clarified or resolved.

The design of the gas-filled transmission line is almost complete, including the elbow and the components internal to the photocathode gun's high-voltage tank that will be installed in the Facility. We have ordered the spinnings for the elbow and mid-voltage corona ring, anticipating about four weeks for delivery. The new toroids for the high-voltage power supply (HVPS) were ordered. Delivery is scheduled for May 9. Design work for the other HVPS components continues.