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

cc: Division (M7), FEL Coordination Group

From: F. Dylla

Subject: IR Demo Project Weekly Report, January 25-29, 1999

Date: January 29, 1999

Management

Highlights for the week include the finishing of the planned installation/maintenance activities and the start-up of gun conditioning.

We have confirmed that RADM Paul Gaffney will be visiting the FEL project as a quest of the Commonwealth's Secretary of Technology (Don Upson) on Feb. 16th.

Several papers were presented on the FEL program at this week's SPIE High Power Laser Conference in San Jose.

FEL Installation/Maintenance Activities

The following installation/maintenance items were completed this week:

The gun was high-voltage processed, and the cathode was heat-cleaned and cesiated. The high- voltage power supply for the gun was tested to 5 mA into a relatively low impedance load.

Twelve viewers were aligned and their gains checked. Three new viewers were installed, two in the first recirculation arc, and one in the energy-recovery dump line. Four beam-loss monitors were installed as beam-scraping diagnostics. They are not linked to the machine protection system. The two new beam-current monitors were connected, and their electronics were tested.

The rf system, dipole-magnet power supplies, and beam-position monitors were checked out.

A vacuum leak in the first recirculation arc developed and was fixed.

The modified infrared detectors in the waveguides of the cryomodule were tested under full- gradient conditions, and their trip levels were reset.

FEL Commissioning Activities

The week was devoted principally to getting the machine ready to run. It took a couple of days to chase down and fix vacuum leaks stemming from installation of new diagnostics. Meanwhile, final touches in rejuvenating the gun took place. After installation of a new cathode wafer, the gun was high-voltage processed to the point of quiet field emission at 430 kV. It was heat- treated last night at 675 C for two hours to purge remanent impurities. Early this afternoon the cathode was cesiated, and just before this writing (1500 Friday, 29 Jan 99) its photoresponse was measured. Unfortunately the white-light response was only 1.4 µA, with a red-to-white ratio of 28-to-1. These numbers are nearly identical to those of the last cathode at the beginning of its run, and they indicate the cathode is dirty. We do not know why this is happening, i.e., whether the "dirt" is coming prior to installing the cathode in the gun, or in conjunction with the high-voltage processing. Plans are to turn on the gun Monday. If the current is satisfactory, commissioning will resume. If not, then most likely we will do a protracted, lower-temperature heat clean, recesiate, and try again.

System checks also took place throughout the week, including, for example, turning on the magnet and rf systems, as well as running the drive laser. In addition, the new "FEL Driver Recovery Procedure/Optimization Test Plan" was fleshed out.