MEMORANDUM



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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IRFEL Weekly Report, March 3-March 7, 1997

Date: March 7, 1997

Management

Excellent progress was made this week on RF windows, new ceramics for the HV stack assembly for the gun, magnet procurements and the accelerator vault in the facility. Details are given in the report that follows.

We received a draft of the reviewers' report from last week's DOE-BES review. The draft report is positive. D. Helms and F. Dylla visited the BES program office on March 6 to discuss follow-up activities resulting from the review. The primary follow-up activity is generating research proposals from the pro-positive FEL user community to be sent to BES for evaluation. Outlines of four such proposals were presented to BES to initiate the proposal process.

A draft proposal and statement of work for the 1 micron IR FEL Demo Upgrade were prepared and sent to the Navy High Energy Laser Office for comments.

R. Li attended a workshop on March 6 hosted by the Naval Post Graduate School on the subject of coherent synchrontron radiation.

M. Shinn gave a presentation entitled, "The Free Electron Laser, a Possible Tool for the 21st Century Automotive Industry" at the Automotive Laser Applications Workshop '97, held in Novi, MI.

Injector Test Stand

This week we performed a set of magnet sensitivity studies to investigate the relationship of the gun solenoid field to beam emittance, particularly in the region around 20 pC/bunch. The data suggest a strong sensitivity for emittance to solenoid strength. The data has also been passed to the modeling effort for explanation.

We continued development work on the bunchlength and longitudinal emittance measurement programs. In beam tests we performed several bunchlength measurements using the rf cavity. The measurements give a one sigma bunchlength of 20 to 25 psec. This is very comparable to the 20 to 30 one sigma pulse width previously measured for the drive laser pulse.

In hardware improvements we closed the feedback loops on the phase and amplitude for the rf cavity and switched the laser to run off the common master oscillator.

The drive laser feedback loop for phase has been closed but still has a large RMS error. We also installed the second Conoptics electro optic modulator which will allow us to use the gating and timing system originally designed.

The newest version of the divide-by-two EO modulator is installed and so far has handled full IR power (~ 20W) without problems. We are still optimizing it. In addition, we received the new EO modulator that will give us more flexible pulse selection. It is installed in the beamline and is being optimized as well.

This system will allow us to also pulse the rf in the cavity to higher gradients without going into thermal runaway. The higher gradients will enhance our resolution for the bunchlength measurements without sacrificing the signal to noise ratio caused by the extinction ratio of the drive laser modulation system.

The new Ion Implanted Ceramics, having a resistance of 1.88E10 and 1.72E10 Ohms (matched to within a resistance of 10%) were received from Lawrence Berkeley Lab. This implies a dissipation of around 3.5 watts at full voltage of 250,000 V which is ideal.

We plan to weld the Cathode Support Tube to its flange and weld the ceramics to their respective vacuum flanges and mid voltage ring next week and complete the refurbishment of the Gun in two weeks.

Also planned is the exchange of the vacuum valve between gun and beam line and the addition of a single Multi-slit element to allow testing its properties. The first tests are planned in about a month after the vacuum bake out and the reinstallation and check-out of the beam line instrumentation.

The back-up ceramic was sent from Hitemp and to Lawrence Berkeley Lab for its implantation.

Accelerator Systems

RF systems:

The spare 50 kW klystron tube has developed a vacuum leak. The tube will be removed from the test set and returned for repair. Also sent out for repairs was a ITS buncher temperature sensor card.

The chopper cavity was operated in both cw and pulsed mode with beam this week. The bunch length measurement was run with 40 W cw into the chopper.

An interference was discovered at the legs of the new gun high voltage power supply tank. We decided to shorten the elbow to allow clearance.

The second high power klystron was configured to use for high power testing of RF windows so that performance of the RF windows can be verified before installation on the unit. An SOP for this testing was implemented.

Hipotronics (vendor for the 225 kW power supply) is now about 2 months late. They are still claiming to be able to deliver in May but we are concerned. We are planning a trip to the factory late next week for a first hand evaluation.

Instrumentation and Controls:

All shielded and unshielded beam viewers were received; they are undergoing QA checkout. Three will be connected to an RGA to check cleanliness; the first was reviewed and looked fine.

48 of 150 vacuum gate valve control cards have arrived ready for testing. The balance will be shipped today (3/7). The majority (125) of these are for a CEBAF upgrade.

All 50 beamline ion pump control cards are here and being tested.

Ion pump power supply fabrication continues, the new log amp board prototype has been tested and checked out OK. 400 of these will be ordered; 100 for the FEL and 300 to upgrade CEBAF. The volume purchases are helping to keep our costs down.

Beam Transport:

Design of the 180 Degree dipole and second Reverse Bend continued at Northrop Grumman. Design of the Injection Chicane dipoles continued at Jefferson Lab and we anticipate going out for separate bids next Thursday.

Bids are due on the Optical Chicane Dipoles next Thursday.

Our first attempt to create the Purcell gap and glue the mu metal on to the poles of the prototype dipole was not successful. The epoxy was not squeezed to the anticipated zero thickness that other tests had indicated was possible. While the adhesion proved itself to be acceptably tenacious, we were able to remove the mu metal and aluminum from the pole tips of the prototype with no damage to the pole tip. We are gluing the pieces of aluminum tooling plate under very uniform and high pressure conditions to gain insight into the process variables before the next trial on the prototype.

We are reviewing the layout for the required good field region vs. the new potential stay-out zone from the edges of the chambers.

Eight weak quads were shipped from the vendor and back leg stands and vacuum valves were received. The stands were delivered to the FEL tunnel.

An extensive drawing signing session was held on Friday, March 7, reflecting the greater design resources available to the system starting several month back. The drawings included the back leg girders, Y vacuum chamber, injection line stands, optical chicane dipole stands and quadrupole stands.

The order was placed for the two 100 A power supplies needed for the injection and extraction chicanes with a July delivery date specified.

Shunt construction started and system drawings of the DC power distribution are in active production.

Cryomodule fabrication:

The second warm window was tested to 50 kW in the resonant ring facility. Two warm windows have been assembled into the vacuum test fixture and are being prepared for testing with the ITS 50 kW klystron. The SOP for testing with the ITS 50 kW klystron has been written and approved. We are ready for testing when the window fixture is completed. We expect to run rf next Monday.

Schedule for cooldown and testing the 1/4 cryomodule is set for the week starting 17 March. This will qualify the 1/4 cryomodule with 50 kW rf supply.

Procurements and deliveries of parts are on schedule to support FEL cryomodule assembly. The second FEL cavity pair is scheduled for assembly on Tuesday 13 March. This is a delay of one week.


FEL systems

Injector Reinstallation

Design of the stands in the injector is complete. The clean room contract was awarded to Clean Air Technology. It is scheduled to be installed by June 1, assuming that facility construction progress is adequate.

Wiggler

All mechanical parts for the wiggler are done. The final shipment of magnets is due next week. These will be characterized and sorted for final assembly and testing. Final certification measurement is now scheduled for the first week of April.

The vendor for the wiggler vacuum tubing raised their price estimate dramatically. We are looking for alternative sources.

Optics

Efforts continue on the new design for the optical collimator. This week the mirror mounts and the output Brewster window were the optical cavity components being fabricated. The drawings for the near-Brewster window assembly were signed and are in Procurement. We began assembling optical cavity components, and have found some discrepancies from the prints that will require some minor remachining.

Facility

The facility this week had significant activities going on both upstairs and downstairs. Downstairs the floor was cleaned and sealed. Fire sprinkler pipes were hung over the full area. Placement markers were surveyed in and established for setting the cryo transfer line. The entrance labyrinth had wall finish work performed. The trenches around the vault perimeter were cut and cleaned. The ceiling was painted. After the north side was sealed the cryotransfer lines were placed in their approximate final locations. Several days of adjustments and survey checks will put us in a position of being able to start welding.

Upstairs the exterior wall frames were set in place over more than 60% of the walls. Framework was completed on the utility area, the last major framing work required. Finish work continued around the elevator. Roof decking was placed on about 1/3 of the area.

In a meeting with the contractor it was determined that the floor flatness in the lower level does not meet contract specifications. Nonetheless it does appear possible to compensate for the out of flatness that is observed by setting our stands at different heights. We intend to negotiate a suitable settlement with the contractor to compensate us for the extra effort on this item.

Current plan has the contractor completely out of the lower level (except some testing and touchup) in one more week. This will help our efforts to accelerate the installation activities since we now have stands for the backleg of the accelerator, cryolines are ready to be positioned for welding, and the cable tray is ready to be hung as are the LCW circuits.

Operations

Discussions are underway on the details for implementing the machine protection system. The hardware approach has been chosen and is based on a combination of CEBAF detectors and existing Argonne VME based detector boards. What remains to be determined is the way in which interlocks are zoned: either based on the beam mode in operations or geographically. Each approach has advantages and drawbacks which will be investigated over the next few weeks to settle on a system with the best utility.