Management

December 1997 was the fifth 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. Summary of the technical progress of the remaining three open cost accounts is given below.

CA 221 Scaleable Optical Cavity

The efforts of the Optics Team this month was devoted to alignment sensitivity and reproducibility measurements on the optical cavity assembly installed in the IR Demo. The results of these measurements have immediate impact on the first-light commissioning effort that begins in February; however, these results also affect the design options being considered for the scaleable optical cavity.

CA 321 Upgrade Cryomodule System

The first eight cavities were re-processed and readied for testing. Processing/assembly/testing cycles will continue until cavity pairs are needed for cryomodule assembly late in the fiscal year to gain more process experience and improvement. Vacuum tests were successfully completed on the three inch ID gate valves used in cavity assembly. Four so-called "dogleg" power couplers with windows have been completed for testing next month. These re-designed coupler assemblies have shown considerably less (~10e-3) field emission in prototype tests than the traditional straight-through coupler design. One dog-leg coupler assembly was prepared for cryo-vacuum tests next month with an indium-sealed vacuum plate to simulate make-up to the helium vessel.

CA 421 Commissioning Preparations

This account has been closed to further obligations since October. Remaining cost obligations (on corrector magnets and the Analog Monitoring System) should be closed out in January.

CA 521 IR FEL Commissioning

The focus of the month was getting tune-up beam to the straight-ahead dump, a goal that was completed on 21 Dec. 97, on which day we succeeded in depositing a 38 MeV/c, 2 µA electron beam on the dump. Following that achievement, we ran the beam momentum up to 48 MeV/c to verify consistency of the momentum measured in the first optical chicane with that inferred from the gradient settings on the control screen. Lastly, we ran the charge per bunch up to 60 pC in the injector and measured the transverse emittance using the multislit monitor. The result was high, in excess of 20 mm-mrad versus the expected 6 mm-mrad. Preliminary indications (from the necessary magnet settings) are that the axes of the cryounit cavities are significantly misaligned, a situation that we will look into and correct, if necessary, in January. (Note: the problem was traced to a partially open valve within the cryounit which was corrected. Alignment checked out within tolerance).

In summary, our 1Q98 commissioning goals were achieved. Moreover, the beam delivered to the straight-ahead dump meets the requirements for the GEN polarized-target irradiation experiment that will be installed in early 1998 to support the nuclear physics program at Jefferson lab. The 38 MeV/c momentum is also the required value to support first light.

FEL INSTALLATION

Installation highlights in December included:

Completing all hardware installation from the photocathode to the straight-ahead dump in preparation for the commissioning activities described above. Spare CEBAF air-core correctors were installed pending receipt of the actual air cores from the vendor (now slated for January). Installation of the optical cavity (minus the mirrors) was completed. The optical transport line was completed and checked out under vacuum.

Making further progress toward installing the recirculation arcs. Fit-up of the arc vacuum chambers was completed. All of the dipole magnets have now been released for installation, with the exception of the two 180-degree dipoles. Measurements of core field and field uniformity along the beam path of the first 180-degree dipole are within tolerance. A defect in the coils of the second dipole is being corrected. Its reassembly is slated for late Jan. 98. The large-diameter probe for the sextupole measurements was tested, and four of the eight trim quads were received.