ANL, Argonne, Illinois, USA
LSU, Baton Rouge, Louisiana, USA
Radioactive ion beams (RIB) at the Argonne Tandem Linear Accelerator System (ATLAS) are produced either from the in-flight method at 5-15 MeV/u for A < 30, or via reacceleration of fission fragments from the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) at 4-10 MeV/u for 80 < A < 160. These RIB are typically accompanied by contaminant beams >100x more intense. The goal of this work is to develop a fast (>105 pps), compact (retractable from the beam line) particle detector capable of A and Z identification to enable accelerator optimization on the exact species of interest. The detector should have an energy resolution of ≤5% and be resistant to radiation damage. A gas ionization chamber supplemented with an inorganic scintillator was chosen as the basic conceptual design. GSO:Ce was chosen as the primary candidate scintillator due to a demonstrated energy resolution of ~3% for 15 MeV/u He and less irradiation induced performance degradation than other candidate materials.
ANL, Argonne, Illinois, USA
ATLAS (the Argonne Tandem Linac Accelerator System) is a super conducting heavy ion accelerator which can accelerate nearly all stable, and some unstable, isotopes between protons and uranium with a charge to mass range of 1/1 to 1/7. The maximum energy ranges of these accelerated ions are 7-17 MeV per nucleon with intensities ranging from a few thousand ions/second to microampere currents. On average ATLAS delivers a different ion species and energy each week to one of six target areas. ATLAS currently operates 24 hours a day, 7 days per week, and at least 40 weeks per year. Topics discussed will be how we handle day to day operation of the facility including start up, reusing old accelerator configurations for new experiments (scaling), tuning for in-flight produced radioactive beams, troubleshooting problems, and maintenance.
ANL, Argonne, USA
ATLAS, the world's first accelerator to use RF superconductivity for ion acceleration, has undergone a major facility upgrade with the goals of significantly increased stable-beam current for experiments and improved transmission for all beams. The dominant components of the upgrade are a) new CW-RFQ to replace the first three low β resonators, b) a new cryostat of seven β=0.077 quarter-wave resonators demonstrating world-record accelerating fields, c) an improved cryogenics system, and d) the retirement of the original tandem injector. This latest upgrade followed closely on the earlier development of a cryostat of β=0.144 quarter-wave resonators. This reconfigured ATLAS system has been in operation for over one year. This paper will discuss the on-line performance achieved for the redesigned system, plans for further improvement, and long term facility plans for new performance capabilities. This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.
ANL, Argonne, Illinois, USA
The efficient and rapid production of a high-quality, pure beam of highly charged ions is at the heart of any radioactive ion beam facility. An ECR charge breeder, as part of the Californium Rare Ion Breeder Upgrade (CARIBU) program at Argonne National Laboratory, was developed to fulfill this role. The charge breeding efficiency and high charge state production of the source are at the forefront of ECR charge breeders, but its overall performance as part of the accelerator system is limited by a pervasive stable ion background and relatively long breeding times. Steps have been taken to reduce the level of background contamination but have met with limited success. As such, an EBIS charge breeder has been developed and is now running in an off-line configuration. It has already demonstrated good breeding efficiencies, shorter residence times, and reduced background, and it is scheduled to replace the ECR charge breeder in late 2015. The resultant change in duty cycle and time structure necessitates changes to the overall facility operation. The experiences with these breeders their strengths, their weaknesses, and the possible paths to further improvement - will be discussed.
ANL, Argonne, USA
The ATLAS linac at Argonne National Laboratory has recently been upgraded for higher beam intensity and transport efficiency. Following the installation of the new RFQ, we have performed a high-intensity run using a 40Ar8+ beam. A beam current of 7 pμA was successfully injected and accelerated in the RFQ and the first superconducting section of the linac to an energy of 1.5 MeV/u. Since then, a new superconducting module was installed in the Booster section of the linac replacing three old cryomodules of split-ring resonators. The split-rings are known to cause excessive beam steering leading to beam loss which limits the maximum current in ATLAS. We are planning a second run to try to push the beam current higher and farther into the linac. The ultimate goal is to accelerate 10 pμA to the Booster exit at 5 MeV/u. Among the limitations encountered in the first run are the large beam emittance at the ECR source and the beam loss in the LEBT. The results of these attempts will be presented and discussed.