R.C. Juras

A simple, inexpensive voltage grading resistor for large electrostatic accelerators

Abstract A simple, inexpensive voltage grading resistor installation for electrostatic accelerators is described. Functional tests in the Holifield Heavy Ion Research Facility 25-MV tandem accelerator indicate that this system is insensitive to spark-induced damage at operating potentials up to 24 MV.

Improved voltage performance of the Oak Ridge 25URC tandem accelerator

Abstract Installation of compressed geometry acceleration tubes and associated changes in the corona voltage grading system have resulted in significant improvement in voltage performance of the Oak Ridge 25URC tandem accelerator. Details of the final phase of this work and initial tests on the modified accelerator are provided.

Development of the HRIBF 25-MV tandem accelerator as a RIB accelerator

The Holifield Facility 25URC tandem accelerator will begin accelerating radioactive ion beams (RIBs) for nuclear structure and astrophysics research in 1996. This paper addresses the development of the accelerator to allow optimum operation with the particular challenges associated with RIBs. New diagnostics for ultra-low-intensity beams are being installed and the terminal potential stabilization system is being studied to optimize control with these low beam intensities. A new resistor-based voltage-grading system has resulted in more stable operation as well as allowing operation at the very low terminal potentials which are required for some astrophysics experiments. Also addressed is beam transmission optimization, particularly at low terminal potentials, and operation of the accelerator at high terminal potentials.

The Holifield Heavy Ion Research Facility

The Holifield Heavy Ion Research Facility has been in routine operation since July 1982. Beams have been provided using both the tandem accelerator alone and a coupled mode in which the Oak Ridge Isochronous Cyclotron is used as an energy booster for tandem beams. The coupled mode has proved to be especially effective and has allowed us to provide a wide range of energetic beams for scheduled experiments. In this report we discuss our operational experience and recent development activities.

Radioactive Ion Beam Production Capabilities At The Holifield Radioactive Ion Beam Facility

The Holifield Radioactive Ion Beam Facility (HRIBF) is a national user facility for research with radioactive ion beams (RIBs) that has been in routine operation since 1996. It is located at Oak Ridge National Laboratory (ORNL) and operated by the ORNL Physics Division. The principal mission of the HRIBF is the production of high quality beams of shortlived radioactive isotopes to support research in nuclear structure physics and nuclear astrophysics. HRIBF is currently unique worldwide in its ability to provide neutron‐rich fission fragment beams post‐accelerated to energies above the Coulomb barrier for nuclear reactions. HRIBF produces RIBs by the isotope separator on‐line (ISOL) technique using a particle accelerator system that consists of the Oak Ridge Isochronous Cyclotron (ORIC) driver accelerator, one of the two Injectors for Radioactive Ion Species (IRIS1 or IRIS2) production systems, and the 25‐MV tandem electrostatic accelerator that is used for RIB post‐acceleration. ORIC provides a light ion...

Control system for the Holifield Radioactive Ion Beam Facility

A new accelerator control system is being implemented as part of the development of the Holifield Radioactive Ion Beam Facility (HRIBF), a first generation radioactive ion beam (RIB) facility. The pre-existing accelerator control systems are based on 1970s technology and addition or alteration of controls is cumbersome and costly. A new, unified control system for the cyclotron and tandem accelerators, the RIB injector, ion sources, and accelerator beam lines is based on a commercial product from Vista Control Systems, Inc. Several other accelerator facilities, as well as numerous industrial sites, are now using this system. The control system is distributed over a number of computers which communicate over Ethernet and is easily extensible. Presently, implementation at the HRIBF is based on VAX/VMS, VAX/ELN, VME, and Allen-Bradley PLC5 programmable logic controller architectures. Expansion to include UNIX platforms and CAMAC hardware support is planned. Operator interface is via X-terminals. The system has proven to be quite powerful, yet it has been easy to implement with a small staff. A Vista users group has resulted in shared software to implement specific controls. This paper details present system features and future implementations at the HRIBF.

Progress, status, and plans for the HRIBF project☆

Abstract Over the last three years, the Holifield accelerator system has been reconfigured into a first-generation radioactive ion beam facility, the HRIBF, a national user facility for RIB research. The construction and reconfiguration have been completed and the equipment commissioning and beam development phases have started. The progress to date, the present status, and future plans will be given. The special problems connected with the production and acceleration of RIBs will be discussed.

THE ORNL 25-MV TANDEM ACCELERATOR CONTROL SYSTEM

The CAMAC-based control system for the 25 MV tandem electrostatic accelerator of the Holifield Heavy Ion Research Facility at Oak Ridge National Laboratory (ORNL) was specified by ORNL and built by the National Electrostatics Corporation. Two Perkin-Elmer 32-bit minicomputers are used in the system, a message switching computer and a supervisory computer. The message switching computer transmits and receives control information on six serial highways. This computer shares memory with the supervisory computer. Operator consoles are located on a serial highway; control is by means of a console CRT, trackball, and assignable shaft encoders and meters. Two identical consoles operate simultaneously: one is located in the tandem control room; the other is located in the cyclotron control room to facilitate operation during injection of tandem beams into the cyclotron or when beam lines under control of the cyclotron control system are used. The supervisory computer is used for accelerator parameter setup calculations, actual accelerator setup for new beams based on scaled, recorded parameters from previously run beams, and various other functions. Nearly seven years of control system operation and improvements will be discussed.

Use of the Holifield facility 25-MV tandem accelerator in the Oak Ridge radioactive ion beam project

The absence of time structure and the excellent beam and beam transport properties of tandem electrostatic accelerators make them an attractive choice for the acceleration of a large class of radioactive ion species produced with the ISOL technique. In this paper, considerations on the use of the Holifield facility 25-MV tandem accelerator in the ORNL Radioactive Ion Beam Facility now under construction will be presented. Preliminary beam parameter measurements which suggest that the 25-MV tandem accelerator can be used as an effective separator of isobaric contaminant beams will also be presented and discussed.<<ETX>>

Radioactive beams with the HHIRF accelerators

It is pointed out that the two accelerators of the Holifield Heavy Ion Research Facility (HHIRF) provide a unique opportunity to quickly and economically develop an interim proton-rich, medium-intensity, ISOL-type, RIB (radioactive ion beam) facility. This extension of the HHIRF would provide for research and development until the much larger facility can be realized in the late 1990s. Presently, the Oak Ridge Isochronous Cyclotron (ORIC) serves as an energy booster for heavy ions from the 25-MW tandem accelerator. To produce RIBs, this process could simply be reversed. The tandem accelerator would be injected with heavy ions produced by ORIC. In this case, the two accelerators will be coupled by a thick target, ion source, mass separator, and charge exchange canal, all mounted on a 300-kV high-voltage platform in an existing shielded room. Light ions from ORIC, with an internal ion source, would produce radioactive heavy ions for tandem injection. Moreover, the UNISOR on-line isotope separator allows the timely development of the target-ion source hardware and chemistry. A central feature of this plan is that most of the main components already exist.<<ETX>>