IR FEL Monthly Report for August 1996

Navy IR Demo Contract WBS Elements

WBS 1 Project Management

August 1996 was the second full month of activities for the IR Demo project funded by the Navy. A total of $992k of costs have been obligated. With respect to the planned accrual of project costs by August ($753k), $671k was accrued which accounts for 8% of the project completed. The actual costs accrued through August totals $545k. This results in a negative cost schedule variance of $82k and a positive cost variance of $126k. For the $3.5M FEL Facility, $564k of costs have been accrued and this task is 13% complete.

Several papers were presented by team members at the 18th International FEL Conference and Applications Workshop held on August 26-30 in Rome. S. Benson presented a status paper on the IR Demo project and a paper on user facility design issues. C. Bohn presented a paper on coherent synchrotron radiation effects and Alan Todd (from Northrop Grumman) presented a paper on FEL micromachining applications on behalf of the Laser Processing Consortium.

Planning continued for two workshops to be held in Sept. 1996 hosted by the Jefferson Lab. On Sept. 9-10, the LPC will discuss the FEL User Facility fit-up and planned experiments, and on Sept. 24-25, a workshop will be held to discuss the technical issues that affect scale up of FELs to considerably higher power (MW) than the IR Demo.

WBS 5.0 Instrumentation & Controls

The contract with University of Georgia for two bunch length monitoring systems has been awarded. The first unit will be delivered for testing in the injector test stand. The 2 inch round Beam Position Monitor mechanical design is in prototyping. The design for the 5 inch wide chamber devices has begun. The 1 1/2 inch diameter shielded beam viewer parts are complete and are being assembled. The 2 inch shielded beam viewer parts are being procured.

The hazard assessment for the Personnel Safety System is proceeding as well as the procurements for this system.

The software required for the IR FEL is being written for use in the Injector Test Stand (ITS). The emmitance measurement software has been tested with beam and is operational. The beam viewer software is functional and much progress has been made with the video imaging hardware and software which will output a position from the spot on the beam viewer.

Drive laser remote instrumentation and control has been specified. The design for the interlocks, monitoring instrumentation and control is progressing. A hardware interlock has been built to protect the laser against variations in RF power from the control modules.

The vacuum controls are also progressing. The procurements for the ion pump power supplies are nearly complete, assembly will begin in September.

WBS 6 -- Cryogenic Distribution

The pipe procurement is 100% complete. The major bellows procurement for the cryogenic distribution system was released. Quad transfer line (TL) fabrication is proceeding very well, and is 40% complete. Fabrication of the FEL/CHL TL Bayonet Can for the CHL was started on July 1. Fabrication of the TL anchor at the CHL is complete. Detailed design of FEL Building Supply and Return transfer lines is 75% complete. Detailed design of the CHL Header Extensions is in review. Detailed design of the CHL U-tubes has started.

WBS 7 -- Beam Transport

WBS 7 is currently about a month behind its published schedule, but at this slippage is recoverable before the installation milestone. With regard to magnets:

The prototype reverse-bend dipole was assembled and readied for testing. Design of the 180-degree dipoles commenced at Northrop Grumman. Copper for the major dipoles was ordered. Testing of the prototype main quadrupole vs. the CEBAF-standard QB run within a low current hysterics loop revealed that the QB meets requirements. We are going ahead with procurement of quads with solid QB-style cores and inexpensive coils. The design for the prototype trim quadrupole was defined and initiated.

The dump beam lines were defined up to the first diagnostic. Two units of a relatively simple, new style of magnet were added to the dump chicane to aid in phasing the linac's rf cavities.

The major concerns in this WBS include: (1) recovering the schedule slippage in creating the designs for the injection dipoles and finalizing the major dipoles after the prototype reverse bend is measured; (2) finalizing the trim quad after prototyping; and (3) reducing the cost from the increases in scope.

WBS 8 -- RF Systems

The high-gradient buncher cavity was installed in the ITS. The waveguide was connected and the water skid has regulated the temperature to the required 119 degrees F. Full-power RF tests are scheduled next month after the safety system is installed and checked out. The high-power waveguides for the injector cryounit are complete into the test cave. Preliminary RF software is running for the drive laser, chopper cavity, buncher cavity, and the cryounit. New drive probes for the chopper cavity are designed and are expected in September. The arc detector system has been installed and tested for the 50 kW klystrons and circulators. The balance of the system is ready for installation with the cryounit.

Work is progressing smoothly on the cryomodule control racks for the linac section of the IR FEL, and procurement has started for the required large (225 kW) variable DC power supply.

Standard CEBAF klystrons have now been operating without difficulty in a test at 8 kW for the past 2 weeks. Klystron and circulator testing will continue in September.

WBS 9.2 Injector Move

A conceptual design for the high voltage power supply has been developed and passed on to the designers. Design issues to be resolved at this point involve the details of the power supply modifications and the gas mixture to be used in the high voltage tank.

WBS 9.4 Wiggler

STI Optronics resolved all the magnetic issues raised in the magnet design review held in July with the exception of two mechanical design questions and the issue of how to deal with the ambient field correction. These issues will be settled at the mechanical design review to be held on Sept. 13 at STI Optronics.

Jefferson Lab has given STI Optronics the approval to purchase magnets from Shin-Etsu, and pole pieces from Vacuum Schmeltze. The end correction design is quite elegant and achieves a non-displaced trajectory with little waste of periods. The effective number of periods should therefore be greater than 40 with zero beam displacement at either end.

One of the requested items from the magnet design review is sample data from the U27 wiggler at APS and the analysis algorithms for the measurement data. This is being studied so that the data for the IR Demo wiggler can be analyzed in parallel with STI Optronics.

WBS 9.6 -- Optics

In the optics WBS element progress was made in the following areas:

Work began on the computer interfacing of the Mach-Zehnder interferometer for the optical cavity length measurement. This will become a major deliverable of a contract under the direction of Dr. M. Buoncristiani at Christopher Newport University.

Our tests of the applicability of an in-house spectrometer and PDA to rapidly acquire spontaneous emission spectra suggest that this would be very difficult at the fifth harmonic (~600nm), but should be achievable at the third harmonic (~ 1000 nm).

Finite-element analysis of the temperature distribution in various optics was slowed by problems with the remote computer that executes the code, but this is back on line generating results that will be used to refine our input to our physical optics code.

The design of the optical cavity and its supports has progressed to the point where they are undergoing our internal check-off procedure. Procurement of major optical components is proceeding, such as the pyroelectric camera that will be used for beam profile and beam quality measurements.

Low (a few mW) and high (~1 W) power laser radiation has been transported from the adjacent Clean Room to the photocathode in the Injector Test Stand. The incident beam is spatially stable and of good beam quality, as evidenced by the resulting electron beam.

Injector, SRF, Facility, and Other Activities Outside Navy IR Demo Contract

Injector Test Stand

The ITS started operations this month with the production of 250 keV beam from the photocathode gun. The gun operated over a two-week period, and its beamline was commissioned. The highlight was production of a 1 mA cw beam with 0.41 W of optical power from the Nd:YLF drive laser for a 26-minute interval. During this time, 1.5 C of charge propagated to the dump without recesiating the photocathode and without any measurable cathode degradation. Because we knew the cathode was misaligned, we then decided to cease operation in order to replace it. Upon disassembling the gun, we found the cathode to be mismounted, and in turn we modified the mounting procedure. New beam tests are slated for early September.

Development of a new high-voltage stack proceeded apace. LBL began ion implantation of coupons of alumina to parameterize the process. A source was identified for brazing the Kovar ring. Jefferson Lab's machine shop has started fabrication of a new cathode-support tube that is slated to receive an anti-field-emission coating.

WBS 3 -- Cryomodule

Assembly of the FEL cryounit for the injector is 70 % complete. Acceptance testing is scheduled to start 1 October. Final modifications to the design of the CEBAF cryomodule to accommodate the IR FEL specifications will follow the cryounit's acceptance testing. Procurement of non standard hardware for the higher currents in the FEL linac are proceeding: qualification tests for three inch isolation valves have been completed and the required valves have been ordered; drawings for three inch shielded bellows have been completed and signed off. Drawings for the HOM sub-assemblies have also been completed and signed off.

WBS 2 -- Beam Physics

In answer to one question that arose during the July IR Demo Commissioning Workshop, cursory simulations of the IR FEL with a 250 kV gun indicates that achievement of first light would be possible (with charge-per-bunch of 30 pC), but that operation at full current (with charge-per-bunch of 135 pC) is suspect, requiring at a minimum a reoptimization of the beamline. Plans are to look no further at this question unless the new high-voltage stack, slated to be installed in the gun in early November, were to yield no significant improvement.

Theoretical modeling of the multislit apparatus for transverse-emittance measurements of the "10 MeV" space-charge-dominated beam are nearing completion. This activity will result in (1) a multislit geometry that minimizes measurement uncertainties, and (2) a data-reduction algorithm.

Calculation of impedances of FEL beamline components is a continually ongoing activity. A table of impedances of beamline components is in production. Thus far, no significant impedance-related difficulties are forseen.

The design of the beam transport lattice is essentially finalized and is being fully documented.

WBS 4 -- Commissioning/Operations

Planning for the necessary Accelerator Readiness Reviews (ARR) for DOE was initiated, and a proposed approach for commissioning that incorporates the ARR process was produced and posted on the WWW. The weekly FEL commissioning activities turned to devising commissioning plans for sections of the machine. For example, a draft commissioning procedure for the first recirculation arc was developed and posted on WWW. Several tasks from the weekly commissioning meeting were relegated to newly instituted weekly meetings concerning diagnostics/instrumentation/control, and activities related to control software are receiving increased emphasis.

Facility

Work continued on the facility construction unabated during August. Walls were poured in several areas of the west end of the lower level bringing to completion about 1/3 of the first 10 feet. All major excavation was completed. The elevator pit was constructed and the jack casing installed.

Several issues associated with the electrical power and placement of supporting pillars were resolved. A number of design clarifications were issued and contractor requests for information have been dealt with. No major issues currently exist and the contractor is holding to the original schedule.

Upcoming Meetings and Reviews

LPC Workshop September 9-10 at Jefferson Lab

Navy MW-Class SSD FEL Concepts Workshop September 24-25 at Jefferson Lab

Optical Cavity Design Review September 26 at Jefferson Lab

ONR Briefing October 3 at Arlington, VA

SURA Management Review October 28-29 at Jefferson Lab