RA2. Accelerator System Status
ORIC Operations and Development (B. A. Tatum)
ORIC provided a nominal 54-MeV, 10μA proton beam to IRIS1 for the production of RIBS used for commissioning and initial experiments with the new Low Energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS) until an Operational Emergency was declared at HRIBF on July 28 (see HRIBF Updates in this and the previous newsletters). RIB production and ORIC operations were suspended by ORNL management in order to conduct a four month investigation into the event. The remainder of the second half of 2008 was consumed by the development of a corrective action plan. ORIC operations were resumed in early February 2009.
During the shutdown, some equipment improvements were made to ORIC systems. A new 20-inch cryopump was installed on the rf resonator enclosure, replacing a failed unit and providing supplemental pumping to the three main diffusion pumps. The associated gate valve was also extensively refurbished. Four new power amplifiers have been received in addition to a new 4648A power amplifier tube, providing much needed backup capability for the ORIC rf system.
A program was initiated to replace the 50-year-old ORIC substation circuit breakers with new units with the goal of improving reliability of operation and reducing maintenance. The new breakers can be easily racked out and locked out, and also include remote power monitoring capability. Concurrently, preventive maintenance was performed on motor control centers and some deteriorating cabling and power distribution panels were replaced.
RIB Injector Operations and Development (P.E. Mueller)
Prior to the unexpected shutdown of the facility at the end of July 2008, the radioactive ion beam injector (IRIS 1) delivered beams of
3000 pps 200-keV 1- 75Cu, 300 pps 200-keV 1- 76Cu, 130 pps 200-keV 1- 77Cu, 1760 pps 200-keV 1+ 76Cu, 2000 pps 200-keV 1+ 80Zn, and 200 pps 200-keV 1+ 81Zn
to the Low Energy Radioactive Ion Beam Spectroscopy Station (LERIBSS).
These beams were produced via proton induced fission of 238U by bombarding a pressed powder uranium carbide target coupled to an Electron Beam Plasma (positive) Ion Source (EBPIS) with 10 - 12 uA of 50-MeV 1H from the Oak Ridge Isochronous Cyclotron (ORIC).
Tandem Operations and Development (M. Meigs)
The Tandem Accelerator was operated for more than 1900 hours since the last report. The machine ran at terminal potentials of 7.58 to 23.57 MV and the stable beams 1H, 12C, 58Ni, 71Ga, 73,76Ge, 75As, 79Br, 107Ag, 115In, 120,124Sn, 121Sb, and 124Te were provided. This was the first time that Indium has been accelerated at our facility. Due to the 'operational emergency" reported in the last newsletter, no radioactive beams were accelerated during this period. And as a consequence of the same event, the tandem accelerator was put into standby for over three weeks, after which, a tank opening was done and then conditioning was allowed. About 125 hours were spent conditioning, which allowed terminal voltages up to 24 MV. Four tank openings were completed during this period; the first for regular maintenance, one for a broken shorting rod, and two to repair CAMAC power supplies which caused a lack of communication to D4. The new SNICS source purchased from NEC was installed during the first tank opening.