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,
Date: December 4, 1998
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.