MEMORANDUM

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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IRFEL Weekly Report, March 17-March 21, 1997

Date: March 21, 1997

Management

Members of the FEL team met with Alan Todd (Northrop Grumman) on March 18 to review and brainstorm on Alan's strawman plan for high power FELs for Navy SSD applications. Alan asked for specific guidance on the near term Jefferson Lab plans for upgrading the IR Demo to higher powers.

An overriding goal of the Jefferson Lab efforts is to plan and implement an IR FEL upgrade design that maximizes the performance of the CEBAF 1500 MHz hardware and minimizes the cost and schedule envelope. The target is an approximately 10kW device that fits the possible FY 97-98 Navy budget line.

We received the final report from DOE for the February 23-25 BES review of the IR Demo project. The FY 98 field work proposal was submitted to laboratory management for inclusion with the Jefferson Laboratory submission to the DOE Oak Ridge Office.

Admiral Al Baciocco, Chairman of SURA's Maritime Technical Advisory Committee visited Jefferson Lab on March 20 with the CEO of American Superconductor Corporation. ASC may have an interest in laser pulse deposition of high Tc materials for their superconducting cable products.

We also hosted visits by Dr. Dave Shoemaker, deputy leader of the MIT LIGO group and the two principles involved with the new 1.5 GeV synchrotron/FEL radiation source near Kobe, Japan.

Jefferson Lab will host an AVS sponsored workshop next week (March 26-27) on "Contamination Control and Measurement in Vacuum Systems." The workshop will attempt to cross fertilize the accelerator and microelectronics communities on common problems in this area.

Injector Test Stand

We made three measurements of bunch length versus transverse position at low charge per bunch. These measurements were in close agreement with the laser autocorrelator signal, giving an indicated one-sigma bunch length of 23 ps with the laser cavity optimized. We also did a longitudinal emittance measurement at low charge per bunch, thereby verifying the software and technique necessary for the measurement. We also started to integrate lessons learned from last week's remote run of the ITS from the Machine Control Center (MCC) to enable routinely running from the MCC in the future with operations support.

We discovered a curious hole in the electron beam following the cathode life test last Friday. It is unknown whether this is an artifact of the beamline, the laser optics, or the cathode.

Upon determining that the second high-voltage-bias supply for the electro-optic modulators had failed, we returned it to the vendor for repair. We also determined that the modulator's thermal blooming problems were related to the indexing fluid used in their manufacture. A dry design is being fabricated by the vendor and will be shipped after it has been tested for the problem.

Regarding upgrading the photocathode gun:

Upon receiving the back-up ion-implanted ceramic from Lawrence Berkeley Laboratory on Monday (17 Mar 97), we decided to use it to replace the most severely misbrazed ceramic of the two we already had on hand. We then successfully bent the kovar flanges to compensate for the remaining gap that resulted from misbrazing in preparation for welding the high-voltage-stack assembly. Welding proceeded on Wednesday, and the assembly was verified to be leak-tight on Thursday. Consequently, we began tearing down the gun on Thursday to replace its ceramic stack with the new ion-implanted one, and to replace its cathode support tube with the new one having a field-emission-resistant coating. This effort is being expedited, with work scheduled over this weekend.

Regarding other ITS activities:

We completed software development for remote control of the photocathode gun's high-voltage power supply, including provisions for status updates and current-limit and voltage-ramp-up controls. Remote control of the power supply for the first electro-optical modulator was likewise completed, as was the rf attenuator for this modulator.

One of the two "good" warm windows broke Sunday afternoon (16 Mar 97) at 30 kW on the 50 kW klystron test stand, which is now operational. This is one of the two windows that qualified last week at 25 kW. The other is still intact. It's not yet known why the one broke -- NASA's infrared monitoring system was in use with the one that didn't break.

In view of the window breakage, we plan to proceed by qualifying fully the surviving window to nominally 20-25 kW and install it on the cryounit. Subsequently we will do all the planned experiments per existing schedule using the one waveguide-window assembly. Meantime, we will vigorously pursue warm windows to 50 kW by, for example, getting consistent ceramics from vendors, further klystron testing, etc. We are putting together a program to get these windows at about 50% confidence by 1 June and at about 90% confidence by August. If for some reason windows are unavailable even then, it would take about 2 weeks to install and test them on the cryounit once the unit is installed in the FEL Facility. It is not a problem to have warm windows to support first light; 20 kW windows will be OK for 1.1 mA beam.

The diode temperature cards for the cryounit were installed in the CAMAC crate. The readout software is to be loaded early next week.

Accelerator Systems

Regarding the beam-transport system:

The photon optics of the machine in the optical-chicane region were changed slightly to allow space for shielding in front of the optical collimator. The shift does not affect clearance to other features of the optical cavity or the design of the dipole magnets.

Bidders received solicitations for the optical-chicane dipole magnets. Design work continued on the remaining reverse-bend, 180-degree, and injection/extraction dipoles.

At the Magnet Test Stand, 304 stainless steel qualified as the vacuum chamber material of choice after tests in the prototype dipole. The prototype trim quadrupole magnet underwent detailed magnetic measurements which will require extensive analysis over the next few weeks. The prototype sextupole magnet went through preliminary characterization with the conclusion that the basic design is sound but we will need field clamps. The exact pole-tip shape will need further work, but fabrication and even installation can proceed.

The first article of the main quadrupoles arrived from the vendor. It passed magnetic acceptance tests.

A very productive kick-off meeting was held regarding design of the stands for magnetic elements downstream of the cryomodule.

Regarding the vacuum system, the differential pump station was signed off, and design of the vacuum chambers in the remaining first-light regions started. Substantial portions of the vacuum hardware have been ordered.

Regarding the power supply system, the request for bid on the two 100 A power supplies needed for the injection and extraction chicanes was sent to the power supply vendor.

Regarding cryomodule fabrication:

We could not test the second cavity pair this week because the Vertical Test Assembly (VTA) sprung two vacuum leaks and is being repaired. However, we assembled the third cavity pair this week and are anticipating putting both the second and third pairs through acceptance tests on the VTA very soon, perhaps next week.

Regarding electron-beam instrumentation and controls:

An ever-increasing fraction of I&C activities is focused on equipping the FEL Facility. For example, this week almost all of the cable trays were hung in the accelerator bay, and the box ducts for the Personnel Safety System are being installed. Installation of AC power and panel assignments are proceeding in the Facility. The location of the transformer had to be changed to avoid interferences; the transformer will now hang from the ceiling.

The effort to assign channel locations for the many signals from the machine continues, this week focusing on signals from the beam-loss monitors.

FEL Systems

Injector Move

Vendor for clean room has received notification to proceed with construction. HV tank on schedule for delivery at end of April. Design of the ancillary to start next week.

Wiggler

Design work for wiggler vacuum chamber and support is on schedule for detailed drawings to be delivered next week.

Optics

The 5 micron mirrors have cleared Procurement, delivery is expected in mid-July. The metal mirrors that will be used in the optical transport system also cleared Procurement. We expect a designer sometime next week to replace the system designer who resigned last week. During the interim there will be little progress in the remaining design efforts.

Operations/Commissioning

The principal activity for the week in this area was an extensive discussion concerning the Accelerator Readiness Review (ARR) process, especially as regards its purpose and sequence. Operation of the accelerator is envisioned not to be contingent on completing the ARR process. Rather, the ARR process is intended to allow routine and productive operation of the entire system, which means we can commission without going through the entire ARR. The key prerequisite in deciding how to implement the ARR is coming to agreement with the regulatory parties (Navy and DOE site office) about the relative importance to the ARR of EH&S issues vis-à-vis technical issues. We started preparing a proposal concerning ARR for the DOE site office. A www-based system will probably be the vehicle for implementing and monitoring the ARR process.

Facility

Facility work continued at a rapid pace this week, only slightly hampered by the rains. Downstairs the return leg stands were grouted into position. The cryolines were positioned and welding the pieces together began. Box duct for the safety system was hung and the cable trays were essentially complete. Hangers for the optical transport pipe were placed in the ceiling and the optical transport line welding began. The contractor has received the trench covers and pit rails and will set them early next week. Upstairs roofing of the mechanical room was complete and decking was 90% complete over the rest of the building. Plumbing is in the process of being installed including roof drains. HVAC ducting is being hung. Wall panels are commencing at the SW corner and proceeding around the building. The wall studs have been placed across the front except the injector area and is proceeding along the back. Roof equipment was placed and plumbing and electrical work continued in the lobby. Arrangements were made with the contractor to begin putting electrical racks in the upstairs starting April 4.