Management

February 1998 was the seventh month for the $3.7M IR Demo Upgrade and Commissioning project. Cost and schedule performance are described in the accompanying "Performance Assessment" report by Gordon Smith. Early in the month, linac commissioning was restarted after the January shut-down for Central Helium Liquiefier maintenance. However, beam commissioning activities were suspended for the remainder of the month when an internal arc necessitated the dis-assembly and refurbishment of the photogun. The down time was used constructively for completion of installation tasks and initial alignment of the optical cavity components. Despite the loss of commissioning time, we still expect to meet the primary commissioning milestone of "first light" well within the contractual period and within the contractual budget. Some contingency was provided in the overall budget with the arrival of $200k from the DOE-BES program office to support commissioning activities related to coherent synchrotron radiation (CSR) measurements. A summary of the technical progress of the three open cost accounts is given below.

CA 221: Scaleable Optical Cavity

The optics team continued to concentrate its effort on the checkout, alignment and commissioning of the FEL optical systems. Arrangements were finalized for John Foley, an optics theory expert who will be spending a 6-month sabbatical with us starting July 1 to work on the scaleable optical cavity design and performance modelling.

CA 321: Upgrade Cryomodule System

The cryomodule assembly process study being performed with support from the Old Dominion University Engineering Management Department was completed with a presentation to the Division on results. Follow-on work is required to evaluate and implement, if appropriate, identified improvement plans. A technical review of the planned CEBAF energy upgrade cryomodule was held. The focus of the review was the cryostat design concepts. The down select for cryostat concepts will be made in March. We expect that some of the improvements slated for the CEBAF modules can be incorporated in the FEL upgrade cryomodule presently under fabrication.

Seven of ten dogleg couplers have been fabricated. Testing will start next week on a five cell cavity to qualify each window assembly.

CA 421: Commissioning Preparations

This account has been closed to further obligations since October.

CA 521: IR FEL COMMISSIONING

Beam commissioning activities resumed on 5 Feb. 98. Tune-up beam was accelerated through the cryounit and viewed as a small round spot. Thus, the partly closed valve discovered at the start of the January shut-down appears to have caused the beam shape issue discovered during the December run. The gun ran at slightly lower voltage, 340 kV versus the usual 350 kV, and the cathode appeared to have a slight tilt. That weekend we refurbished the gun in an attempt to correct these deficiencies, and commissioning resumed Monday, 9 Feb. 98. Unfortunately, it was short-lived because the gun field-emitted copiously down the beam pipe, a most unwelcome and unexpected circumstance. We terminated commissioning and began an autopsy of the gun. We subsequently repolished the cathode ball to remove minor blemishes. We also built a stainless steel shield for the getter pumps that will protect the pumps and hopefully reduce impurities in the high-voltage region. At this writing (17 Mar 98), the gun has been restarted and beam has reached end of the injector. We restructured our commissioning plans after turn-on to expedite GEN target irradiation in support of the nuclear physics program. Consequently, we will run tune-up beam to the straight-ahead dump as quickly as possible, then insert the target chamber. We will defer all 60 pC (first-light) setup until after the GEN targets are prepared.

Testing of the injector cryounit verified that it now can be operated at 11 and 9 MV/m with its new ceramic warm windows. These are the nominal values that had been assumed in most of the simulations done to date. Development of optimized PARMELA settings for 60 pC first-light beam is nearly complete. The package includes images at the various viewer locations.

A "checkout" of the two multislit transverse-emittance diagnostics was done via simulation (PARMELA) with the latest injector settings for 60 pC. The findings indicate that these diagnostics will perform well with 60 pC bunches and will support a procedure for identifying and isolating drifts from nominal settings in key components of the injector.

FEL INSTALLATION

Installation highlights in February included:

General installation activities to ready the straight-ahead accelerator for first-light electron beam. Examples include: installing and connecting all remaining beam-position monitors up to the straight-ahead dump, installing and operating two replacement 8 kW klystrons for the FEL cryomodule, installing and wiring the raster magnet for the straight-ahead dump, and making considerable progress toward completing the machine protection system. Miram curves for all of the cryomodule klystrons were taken at cathode voltages of 11.6 and 14.0 kV. Their heater voltages were adjusted to extend their operating lifetimes at 14.0 kV, the voltage required for 8 kW operation.

Installation of a sulphur hexafluoride recovery system for the gun. It will reduce our operating costs by about $7500 (the cost of the sulphur hexafluoride) every time the cathode is replaced or the gun is otherwise refurbished.

Installation of the first 180-degree dipole magnet and its vacuum chamber subsequent to completing the magnet's measurements on the Magnet Test Stand.

Completing installation of the low-conductivity-water cooling system for the insertable dumps. The stand for the insertable dump located at the end of the second recirculation arc was installed.

Rework and installation of the mirror mounts, trial mirrors, and collimator mirrors for the optical cavity. The upstream pellicle (used for optical-cavity alignment) was reworked and tested. The downstream pellicle and the laser safety system shutter were also installed in the optical cavity and tested. The high power optical train is instrumented and operational.

Installation of laser safety systems for User Lab Rooms 4 (for use by the Saclay nuclear physics group to provide polarized He³ nuclear targets) and 6 (to support the Compton polarimeter for CEBAF Hall A). They involve use of a smart card to gain access to the rooms.