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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, November 30-December 4, 1998

Date: December 4, 1998

Management

Highlights for the week include the achievement of 75 watts cw lasing (as measured in the optical control room) with a recirculated electron beam current of 1.1 mA.

A meeting was held with Northrop Grumman and Advanced Energy Systems personnel to discuss possible collaboration with the 20 kW upgrade project.

Dr. Greg Exarhos from Pacific Northwest Labs visited Jefferson Lab this week to present a seminar on his studies of laser damage of materials and to discuss possible collaboration with the FEL team.

FEL Installation/Maintenance Activities

The FEL gun went through a refurbishment cycle this week. At the end of last week's shortened run due to the Thanksgiving holiday, it was decided to recesiate the cathode before beginning this week's run. After recesiation on Monday, some field emission activity was noted at approximately 350 kV. The cathode was given a long heat clean, followed by gun high voltage conditioning to 500 kV, a short heat clean cycle and a second recesiation. This procedure restored the cathode to capabilities of providing 60 pC beam at the required 350 kV.



FEL Commissioning Activities

After restoration of the gun parameters on Wednesday evening, commissioning of the recirculation loop continued through the remainder of the week. As of Friday at 5:00pm cw lasing at 75 watts was achieved with 1.1mA of recirculated current with the gun operated at 37 MHz. Earlier in the day half-frequency operation (18MHz) achieved 78 watts of cw laser light with 0.8 mA of recirculated current. These laser powers are measured in the optical control room. The power levels emitted at the laser are approximately 1.4 times larger. The bottom line: good progress is being made toward the primary goal of pushing up simultaneously the laser power and the recirculated current.