Monthly Report IR Demo FEL Upgrade and Commissioning Project

March 1998

Management

March 1998 was the eighth month for the $3.7M IR Demo Upgrade and Commissioning project. Cost and schedule performance are described in the accompanying Performance Assessment report by Gordon Smith. Highlights for the month include: (1) successful re-start of machine commissioning operations after re-build of the photogun; (2) use of the FEL linac at 38 MeV at 2mA cw for irradiation of ammonia targets for the Nuclear Physics program; (3) successful longitudinal alignment of the optical cavity.

CA 221: Scaleable Optical Cavity

A two-day meeting was held with John Foley, a theoretical optician from Mississippi State, who will be joining the project on a sabbatical leave in July to continue our design efforts on scaleable optical cavities. All other efforts by the FEL optics team continue to be concentrated on first light. The IR Demo optical cavity was successfully aligned on its primary axis to better than 100 microns using three different methods. Also during March, significant progress was made toward commissioning the optical diagnostics for characterizing the IR Demo output light.

CA 321: Upgrade Cryomodule System

Individual cavities slated for the upgrade cryomodule continue to be tested after various regimens of cavity chemistry and rinsing as a means for improving cavity performance.

A series of high pressure rinse only tests has revealed interesting results in that a breakdown is occurring in some cavities that leads to increased field emission as the limit (something blows up and spreads the contamination). This process is fully recovered by high pressure rinse butthe source of the problem is still under investigation.

4 of 8 FEL 5 cell cavities were polished at the equator electron beam welds (EBW) with an improved grinding system. The welds were documented on video before polishing and after heavy chemistry. Many weld defects were identified and removed. Testing of these cavities is planned for early April.