MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IR FEL Weekly Report: July 1-12, 1996
Date: July 12, 1996, 1996
Management
Cost, schedule and earned value reporting templates were finalized
in preparation for the June monthly report to be issued on July
15. All spreadsheets have been updated with approved overhead
and G&A loadings.
Overview presentations on the FEL program were prepared for the
SURA Science and Technology Review on July 16-18 and for the Navy
Program Review to be held at ONR on July 30.
FEL Accelerator Systems
A cavity pair which delivers 10 MV/m was chosen for assembly into
the gun cryounit. After demonstrating good gradient, Q, and vacuum
integrity during vertical dewar tests, assembly of the cavity
into a cryounit commenced.
Modeling confirmed the previous estimates of longitudinal dynamics
in the recirculation with FEL-induced energy spread. An approach
with nearly neutral RF loading has been chosen as the baseline
although tuning knobs will permit an exploration of a wide parameter
space.
Fabrication of the 60 foot long cryogenic return lines has begun.
Injector Test Stand
The bake of the injector test stand was completed. The gun bake
was fully successful while a small leak appeared in the transport
line during cooldown in a commercial six-way cross in a weld joint
which previously tested okay. We are attempting to repair the
leak in-situ and remain on schedule for gun testing.
The phase noise was measured of the photocathode drive laser and
found to be less than 1ps thus satisfying the design requirement.
A conceptual design for the 10 MeV emittance diagnostic was adopted
based on work previously done by UCLA. The beam selector uses
an array of slits at a beam waist followed by a OTR screen which
can measure the local beam divergence. The design will be optimized
for an assumed emittance of 8 mm mrad which would result in a
20% uncertainty if the emittance comes in as low as 4 mm mrad.
Operations/FEL Optical Systems
Planning continues for the Commissioning Workshop to be held July
24 and 25. The proposed agenda was issued to all participants
for review and comment. The background material and introductory
presentations for the workshop are being prepared.
Modeling of the spontaneous spectrum was performed to analyze
sensitivity to alignment and help determine the usefulness of
this diagnostic in initiating lasing. The fundamental spectrum
was very insensitive to the levels of errors expected but some
effects could be observed on the third harmonic, especially at
the lower energy spreads which should occur under reduced charge
tuneup.