RA2. Accelerator System Status
ORIC Operations and Development (B. A. Tatum)
ORIC did not operate for most of the reporting period due to a combination of several factors: the Beryllium RIB campaign with the batch-mode ion source, stable ion beam runs, maintenance activities, a tandem tank opening, and HPTL construction. Maintenance activities included the replacement of the deflector high voltage electrode which developed an extremely small water leak, but one large enough to prevent stable operation of the device. Control system and RF improvements were also made
ORIC operation resumed in June for 17F astrophysics experiments and the machine performed quite well with only the normal frequent cathode change-outs that are associated with helium beams. This was the first operation of ORIC on the EPICS control system and we are pleased with the performance to date.
Tandem Operations and Development (M. J. Meigs)
The Tandem Accelerator was operated for approximately 2600 hours since the last report. The machine ran at terminal potentials of 2.44 to 23.22 MV and the stable beams 1H, 2H, 7Li, 10B, 12C, 16O, 18O, 23Na, 24Mg, 28Si, 32S, 54Fe, 58Ni, 75As, 124Sn, and 172Yb were provided. This is the first time Yb has been accelerated at our facility. Radioactive beams of 7Be, and 18F accounted for about 600 hours. Six tank openings were necessary during this period with one being a scheduled maintenance period. Two of the other five were to fix vacuum leaks of which one was caused by maintenance activities and the other was failure of a Faraday cup bellows. The other three were to fix damage to the terminal communications and the terminal bending magnet power supply, which was caused by sparks. During the regular maintenance period it was discovered that the terminal CAMAC crate box cover was not tight which would allow spark energy to enter and cause failures. Since this problem was fixed, we have had no terminal communications failures. About 290 hours were spent on conditioning with the goal of operation at 24.5 MV for the neutron-rich program.
During this period, beam lines 31 to the RMS and 16 to the OLTF were reinstalled and beams were delivered to these two areas. No beam had been delivered to either area for about eight months due to the High Power Target Laboratory construction.
RIB Injector Operations and Development (P.E. Mueller)
During this reporting period, we delivered beams of
6.5 Mpps 1+/ 4+ terminal gas / post foil stripped 12 MeV pure 7Be and
30 Mpps 1+ terminal gas stripped 12 MeV 7Be to the Daresbury Recoil Separator, and
1 Mpps 1+/ 4+ terminal gas / post foil stripped 14 MeV pure 7Be and
400 kpps 7+/ 9+ terminal foil / post foil stripped 150 MeV pure 18F to the astrophysics endstation in Beam Line 21.
The 7Be beams were produced with a cesium sputter negative ion source with 126 mCi 7BeO in Ag powder in a Cu holder. The 18F beam was produced via the 16O(4He,pn) 18F reaction by bombarding a fibrous HfO2 target coupled to a Kinetic Ejection Negative Ion Source (KENIS) with 2 euA of 85 MeV 4He from the Oak Ridge Isochronous Cyclotron (ORIC). This is the first operation of a KENIS with permanent magnets installed around the beam line upstream of the first quadrupole multiplet to sweep away electrons and with the recirculating cesium jet charge exchange cell removed to maximize transmission. The KENIS cesium oven heater, external line heater, and internal line heater were controlled by MICROMEGA CN77000 Series Controllers in a modified controller chassis. During the 18F campaign there were NO failures of these new heater controllers. We plan to implement these controllers for the new recirculating cesium jet charge exchange cell for the upcoming neutron rich fission product campaign. The previously used OMEGA controllers failed frequently.
High voltage transient protection circuitry was installed for the (cathode and target heater) high current power supplies at target ion source potential in C111N. The increasing vibration of the platform potential motor-generator shaft was reduced by replacing both coupling bearings, both coupling elements, the flange bearing, and the pillow block bearing. The target ion source potential motor-generator shaft pillow block bearing failed (motor decoupled from shaft) and was replaced. The upper and lower coils for the second dipole of the second stage (isobar) mass separator (BM_12_1) were replaced with ONLY two days of rigging after extensive preparation of the work area.