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.