Next Meeting

Date: 20 May 99

Time: 1500-1600

Place: FEL Facility Break Room

Agenda for Next Meeting

• Status of apertured cesiator (Biallas, 15 min)
• Status of ion implantation (Biallas, Siggins, 15 min)

This Week's Attendees

G. Biallas, C. Bohn, F. Dylla, L. Phillips, T. Siggins

Discussion

This latest round of processing, i.e., to 430 kV with the cathode retracted, taught us that the condition of the cathode ball prevents successful turn-around without going to higher voltage. Consequently, this week was spent processing to >510 kV with the cathode inserted (recognizing we wreak havoc on the quantum efficiency that way). Putting in a cathode shutter as has been discussed recently would be worthless given the present ball because the cathode would need to be retracted for the shutter to be used. Therefore, we decided to do two things. First, we will replace the cathode ball during the June down; the spare ball is polished to 1 µm and ready for installation. Second, we will defer more work on the shutter/shield until we have some experience with the new ball and new apertured cesiator. Possibly we won't need the shield. Nonetheless, G. Biallas presented a conceptually interesting idea for a shield that would fit flush against the lip of the ball and therefore would enable processing to higher (>430 kV) voltage.

The apertured cesiator is progressing, with the "slow" items being the internal support tube and internal cesiator. Biallas anticipates assembly to be complete by mid-June, upon which testing will proceed. L. Phillips says he has a bell jar and rate monitor (the old Perkin-Elmer) that would do for testing, but he also remarked that C. Sinclair may have a more sensitive monitor. In any event, barring unforeseen complications, the cesiator will be ready to install by the last week of June. Biallas discussed getting support from the Alignment Group for installation. That might be tough given CEBAF may have need; if so, we'll adjust our schedule to be compatible with that of the Alignment Group.

All six of the ball-steel plates needed for the ion-implantation tests are in house. D. Bullard has polished one of them to 9 µm; however, he observes some "microholes" believed to be relics from removing small inclusions. In other words, the ball steel doesn't seem to be an improvement from the lower-grade steel he had been working with. T. Siggins will take a look and advise. None of the other five plates are in polishing yet.

Plans are to polish four plates to identical fineness and quality (9 µm "flat") to start. Two will be used as controls and two will be ion-implanted. Depending on the test results, we may or may not wish to do tests with 1 µm plates; we'll make that decision later. D. Manos is having Ling-Ling get the ion-implantation chamber and peripherals ready ASAP.

Biallas reported that two 6-inch disks made from high-quality ball steel were just received and turned over to Bullard for polishing. The remainder are due in shortly.

Closed Action Items

• Biallas: Procure "best quality" (vacuum remelt) steel for the ion-implantation studies. Have JLab machine shop make the plates. Status: All six ball-steel plates (ball steel being what we ultimately decided was "best quality") are now in house.

New Action Items

• Siggins: Inspect the polished ball-steel plates and, if necessary, advise D. Bullard how to improve the polishing. (due 11 May 99)

Old Action Items

• Sinclair: Prepare procurement package for DLC-coated samples for Dylla's signature. Status: Biallas needs to provide Sinclair with a drawing of the electrode plates.. (due 20 May 99)
• Siggins/Biallas: Specify design of experiment to measure cathode temperature. (due date TBD)