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Investigating proton emitters at the limits of stability with radioactive beams from the Oak Ridge facility

Description: By using beams from the Holifield Radioactive Ion Beam Facility at ORNL, it should be possible to identify many new ground-state proton emitters in the mass region from Sn to Pb. In these investigations nuclei produced in fusion-evaporation reactions will be separated from incident ions and dispersed in mass/charge with a recoil mass separator and then implanted into a double-sided Si strip detector for study of proton (and {alpha}-particle) radioactivity. This paper summarizes data presently extant on proton emitters and then focuses on tests and initial experiments that will be carried out with stable beams and with radioactive ions as they are developed at the Oak Ridge facility.
Date: October 1, 1996
Creator: Toth, K. S.; Batchelder, J. C.; Zganjar, E. F.; Bingham, C. R.; Wauters, J.; Davinson, T. et al.
Partner: UNT Libraries Government Documents Department

Preliminary shielding estimates for the proposed National ISOL Radioactive Ion Beam (RIB) Facility at Oak Ridge

Description: ORNL built a first-generation Radioactive Ion Beam (RIB) facility for astrophysics and nuclear physics research; it was named Holifield Radioactive Ion Beam Facility (HRIBF) and is based on the Isotope Separator On Line (ISOL) technique. Planning is underway for a second- generation facility, the National ISOL RIB facility at Oak Ridge; it will build on the existing HRIBF and may utilize many existing components and shielded areas. Preliminary upgrade plan for the new facility includes: adding a superconducting booster for the tandem accelerator; replacing the 1960-vintage, 60-MeV proton, 50-microamp ORIC (Oak Ridge Isochronous Cyclotron) with a modern 200-MeV proton, 200-microamp cyclotron; and building a high-power {sup 238}U fission target to accept the 200-MeV proton beam. This report summarizes the results of a preliminary 1-D shielding analysis of the proposed upgrade, to determine the shielding requirements for a 0.25 mrem/h dose rate at the external surface of the exclusion area. Steel shielding weights ranging from 60 to 100 metric tons, were considered manageable; these could be reduced by a factor of 2 to 3 if the orientation of the proposed target station was changed.
Date: October 1, 1996
Creator: Johnson, J.O.; Gabriel, T.A. & Lillie, R.A.
Partner: UNT Libraries Government Documents Department

HRIBF Tandem Accelerator Radiation Safety System Upgrade

Description: The HRIBF Tandem Accelerator Radiation Safety System was designed to permit experimenters and operations staff controlled access to beam transport and experiment areas with accelerated beam present. Neutron-Gamma detectors are mounted in eaeh area at points of maximum dose rate and the resulting signals are integrated by redundan~ circuitry; beam is stopped if dose rate or integrated dose exceeds established limits. This paper will describe the system, in use for several vears at the HRIBF, and discuss changes recently made to modernize the system and to make the system compliant with DOE Order 5480.25 and related ORNL updated safety rules.
Date: November 4, 1998
Creator: Blankenship, J.L. & Juras, R.C.
Partner: UNT Libraries Government Documents Department

New resistor voltage grading system at the Oak Ridge National Laboratory 25URC tandem accelerator; installation and first experience

Description: On June 27,1994, installation work was completed on a new resistor-based voltage grading system for the Holifield facility tandem accelerator. This new system replaces the original point-plane corona-discharge system which had inherent disadvantages. Perhaps the worst disadvantages of corona-discharge systems are poor gap-to-gap voltage homogeneity and very low grading currents. It is believed that the resistor-based system will reduce or eliminate these disadvantages as well as some others.
Date: December 31, 1994
Creator: Meigs, M.J.; Haynes, D.L.; Jones, C.M. & Juras, R.C.
Partner: UNT Libraries Government Documents Department

A positive (negative) surface ionization source concept for RIB generation

Description: A novel, versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed and fabricated which will have the capability of generating both positive- and negative-ion beams without mechanical changes to the source. The source utilizes a highly permeable, high-work-function Ir ionizer ({phi}{approximately} = 5.29 eV) for ionizing highly electropositive atoms/molecules; while for negative-surface ionization, the work function is lowered to {phi} {approximately} = 1.43 eV by continually feeding cesium vapor through the ionizer matrix. The use of Cs to effect low work function surfaces for negative ion beam generation has the potential of overcoming the chronic poisoning effects experienced with LaB{sub 6} while enhancing the probability for negative ion formation of atomic and molecular species with low to intermediate electron affinities. The flexibility of operation in either mode makes it especially attractive for RIB applications and, therefore, the source will be used as a complementary replacement for the high-temperature electron impact ionization sources presently in use at the HRIBF The design features and operational principles of the source will be described in this report.
Date: December 31, 1995
Creator: Alton, G.D. & Mills, G.D.
Partner: UNT Libraries Government Documents Department

The latest from the new Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory

Description: The status of new Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory (ORNL), which is slated to start its scientific program late in 1996 is discussed, as is the new experimental equipment which is being constructed at this facility. Information on the early scientific program is also given.
Date: October 1, 1996
Creator: Garrett, J. D.
Partner: UNT Libraries Government Documents Department

The Performance of the HRIBF Recoil Mass Spectrometry

Description: The Recoil Mass Spectrometer (RMS) is a mass separator located at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. This paper describes the RMS, its performance, its detector systems, and discusses some experiments to illustrate its capabilities.
Date: November 13, 1998
Creator: Ginter, T.N.
Partner: UNT Libraries Government Documents Department

Mass and charge distributions in Fe-induced reactions

Description: The charge and mass of the projectile-like fragments produced in the 12-MeV/nucleon {sup 56}Fe + {sup 165}Ho reaction were measured at a laboratory scattering angle of 16 degrees. The mass and charge distributions of the projectile-like fragments were generated as a function of total kinetic energy loss (TKEL), and characterized by their neutron and proton centroids and variances, and correlation factors. A weak drift of the system towards mass asymmetry, opposite to the direction which minimizes the potential energy of the composite system, was observed. The increase in the variances with energy loss is consistent with a nucleon exchange mechanism as a means for energy dissipation. Predictions of two nucleon exchange models, Randrup`s and, Tassan-Got`s models, are compared to the experimental results of the 672-MeV {sup 56}Fe + {sup 165}Ho reaction and to other Fe-induced reactions. The proton and neutron centroids were found to be generally better reproduced by Tassan-Got`s model than by Randrup`s model. The variances and correlation factor are well reproduced for asymmetric systems by both models.
Date: February 21, 1995
Creator: Madani, H.; Mignerey, A.C.; Marchetti, A.A.; Weston-Dawkes, A.P.; Kehoe, W.L. & Obenshain, F.
Partner: UNT Libraries Government Documents Department

Software architecture considerations for ion source control systems

Description: General characteristics of distributed control system software tools are examined from the perspective of ion source control system requirements. Emphasis is placed on strategies for building extensible, distributed systems in which the ion source element is one component of a larger system. Vsystem, a commercial software tool kit from Vista Control Systems was utilized extensively in the control system upgrade of the Holifield Radioactive Ion Beam Facility. Part of the control system is described and the characteristics of Vsystem are examined and compared with those of EPICS, the Experimental Physics and Industrial Control System.
Date: September 1, 1997
Creator: Sinclair, J.W.
Partner: UNT Libraries Government Documents Department

Oak Ridge 24URC tandem accelerator

Description: This report discusses the operation of the Holifield Radioactive Ion Beam Facility (HRIBF) which was dedicated on December 12, 1996, with a formal ceremony followed by a reception and tour. This dedication marked the culmination of the reconfiguration, started in the middle of 1992, and the beginning of full-time operation as an international user facility. Although construction and commissioning are finished, development continues on ion sources and better methods to produce new and more intense radioactive ion beams (RIBs). The first RIB experiment, Coulomb excitation of {sup 69}As, was completed on June 6, 1997. During the time period from June 1-6, {sup 69}As and {sup 67}Ga were provided for seventy-six hours with a maximum of 1.5 x 10{sup 6} particles/sec at the experimental station. Four {mu}A of primary beam, 42 MeV protons from the Oak Ridge Isochronous Cyclotron (ORIC), was on the {sup 70}Ge target to produce this maximum beam. The experimenter was not set up to use this much beam, so most of the run was done at reduced levels. A second RIB experiment, again using {sup 69}As beam, was attempted on 9/9/97. Although a beam of about 10{sup 5} particles/second was successfully tuned to the Recoil Mass Spectrometer, the intensity produced by the RIB injector source was inadequate to complete the experiment.
Date: November 1, 1997
Creator: Meigs, M.J.; Haynes, D.L. & Juras, R.C.
Partner: UNT Libraries Government Documents Department

A High-Charge-State Acceleration Scheme for Potential Upgrade of the HRIBF

Description: This article describes a high-charge-state linear post accelerator for enhancing the number and intensities of short-lived radioactive nuclei at the Holifield Radioactive Ion Beam facility (HRIBF). The system consists of a room temperature RFQ, a normal conducting IH linac and a SC QWR linac that is designed to either bypass or post accelerate beams from the 25-MV tandem. The voltage gain of the linac system will reach 60 MV making possible the acceleration of ions with masses, M {le}150, above the Coulomb barrier. Since the linac accelerates positive-ion beams, it will increase the number of elements that can be delivered for research by a factor of {approx} 3 and the intensity of a given species by orders of magnitude over those of the present HRIBF.
Date: June 29, 2001
Creator: Zhang, Y.
Partner: UNT Libraries Government Documents Department

Oak Ridge 25URC Tandem Accelerator 2001 SNEAP Lab Report

Description: Radioactive ion beam production and development at the Holifield Radioactive Ion Beam Facility (HRIBF) will be detailed in a talk at this conference. A highlight during this period, however, has been providing A{approx}130 neutron-rich RIBs at energies up to {approx}4 MeV/nucleon. At the present time, the HRIBF is the only facility in the world capable of providing such beams.
Date: October 19, 2001
Creator: Meigs, MJ
Partner: UNT Libraries Government Documents Department

The Holifield Radioactive Ion Beam Facility at the Oak Ridge National Laboratory: Present status and future plans

Description: The Holifield Radioactive Ion Beam Facility (HRIBF) is a first generation national user facility for nuclear physics and nuclear astrophysics research with radioactive ion beams (RIBs). The reconfiguration, construction, and equipment commissioning phases have been completed and the beam development program is in progress. In this article, descriptions of the facility and newly implemented experimental equipment for use in the nuclear and astrophysics programs will be given and an outline of the initial experimental program will be presented. Special target ion source related problems, endemic to the production of specific short lived RIBs will be discussed. In addition, plans, which involve either a 200 MeV or a 1 GeV proton linac driver for a second generation ISOL facility, will be presented.
Date: January 1, 1998
Creator: Alton, G.D. & Beene, J.R.
Partner: UNT Libraries Government Documents Department

Status of the radioactive ion beam injector at the Holifield Radioactive Ion Beam Facility

Description: The Holifield Radioactive Ion Beam Facility (HRIBF) is a first generation radioactive ion beam (RIB) facility. Project construction commenced in FY `93 with the initial emphasis placed on conversion of a heavily shielded room from an experiment area to an area suitable for housing the RIB injector. The RIB injector is the central component of the RIB project. The injector consists of two electrically connected high voltage platforms which are designed to operate at -300 kilovolts and which are separated bye a shield wall. One platform houses control, instrumentation, an power supplies. The second platform houses the first stage mass separator system which is designed for 1 part in 1000 mass resolution, electrostatic quadrupole lenses for beam transport, and a cesium charge cell for conversion of positive ions to negative ions for injection into the Tandem Accelerator. This paper details the design and beam development aspects of the RIB injector.
Date: December 31, 1995
Creator: Dowling, D.T.; Alton, G.D.; Auble, R.L.; Dinehart, M.R.; Haynes, D.L.; Johnson, J.W. et al.
Partner: UNT Libraries Government Documents Department

A new concept Tandem thermal dissociator/electron impact ion source for RIB generation

Description: An innovative thermal dissociation/electron impact ionization positive ion source is presently under design at the Oak Ridge National Laboratory for potential use for generating RIBs at the Holifield Radioactive Ion Beam Facility (HRIBF). Because of the low probability of simultaneously dissociating and efficiently ionizing the individual atomic constituents with conventional, hot-cathode, electron-impact ion sources, the ion beams extracted from these sources often appear as a mixture of several molecular sideband beams. In this way, the intensity of the species of interest is diluted. We have conceived an Ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high efficiency characteristics of an electron impact ionization source. If the concept proves to be a viable option, the source will be used as a complement to the electron beam plasma ion sources already in use at the HRIBF. The design features and principles of operation of the source are described in this article.
Date: December 31, 1995
Creator: Alton, G.D. & Williams, C.
Partner: UNT Libraries Government Documents Department

The Holifield Radioactive Ion Beams Facility (HRIBF) -- getting ready to do experiments

Description: The conversion of the HHIRF facility to a Radioactive Ion Beam facility started in 1994. In this ISOL type facility the Cyclotron has been re-fitted as a driver providing high intensity proton beams which react with the target from which the radioactive products are extracted and then accelerated in the Tandem Electrostatic Accelerator to the desired energy for nuclear science studies. Facilities for nuclear physics experiments are at different stages of development: A Recoil Mass Spectrometer (RMS) with a complement of detectors at the focal plane and around the target is used primarily for nuclear structure studies. A large recoil separator combining velocity and momentum selection, with its complement of focal plane detectors, will be dedicated to measurements relevant to nuclear astrophysics. The Enge Split Pole spectrograph is being re-fitted for operation in a gas filled mode, making it a more versatile tool for nuclear reaction studies. With the new experimental equipment being commissioned and the prospects of running experiments with low intensity radioactive beams a significant effort to develop equipment for beam diagnostics is underway. Some of the efforts and results in developing beam diagnostic tools will be described.
Date: February 26, 1998
Creator: Shapira, D. & Lewis, T.A.
Partner: UNT Libraries Government Documents Department

The Production and Acceleration of Radioactive Ion Beams at the HRIBF

Description: The Holifield Radioactive Ion Beam Facility (HRIBF) includes a cyclotron (ORIC) which provides high-intensity light-ions for producing radioactive atoms, and a 25 MV tandem electrostatic accelerator which is used to accelerate the radioactive-ions for nuclear structure and nuclear astrophysics research. Ion sources and targets suitable for the production of various radioactive ion beams (RIBs) have been developed. Operational experiences, problem areas, and plans for future beam development are discussed.
Date: November 4, 1998
Creator: Auble, R. L.
Partner: UNT Libraries Government Documents Department

Ion sources for initial use at the Holifield Radioactive Ion Beam Facility

Description: The Holifield Radioactive Ion Beam Facility (HRIBF) now under construction at the Oak Ridge National Laboratory will use the 25-MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility; the choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. A high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the HRIBF because of its low emittance, relatively high ionization efficiencies and species versatility, and because it has been engineered for remote installation, removal and servicing as required for safe handling in a high-radiation-level ISOL facility. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are also under design consideration for generating negative radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.
Date: December 31, 1993
Creator: Alton, G. D.
Partner: UNT Libraries Government Documents Department

Holifield Heavy Ion Research Facility

Description: 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.
Date: January 1, 1985
Creator: Jones, C.M.; Alton, G.D.; Ball, J.B.; Biggerstaff, J.A.; Dowling, D.T.; Erb, K.A. et al.
Partner: UNT Libraries Government Documents Department

Targets for ion sources for RIB generation at the Holifield Radioactive Ion Beam Facility

Description: The Holifield Radioactive Ion Beam Facility (HRIBF), now under construction at the Oak Ridge National Laboratory, is based on the use of the well-known on-line isotope separator (ISOL) technique in which radioactive nuclei are produced by fusion type reactions in selectively chosen target materials by high-energy proton, deuteron, or He ion beams from the Oak Ridge Isochronous Cyclotron (ORIC). Among several major challenges posed by generating and accelerating adequate intensities of radioactive ion beams (RIBs), selection of the most appropriate target material for production of the species of interest is, perhaps, the most difficult. In this report, we briefly review present efforts to select target materials and to design composite target matrix/heat-sink systems that simultaneously incorporate the short diffusion lengths, high permeabilities, and controllable temperatures required to effect maximum diffusion release rates of the short-lived species that can be realized at the temperature limits of specific target materials. We also describe the performance characteristics for a selected number of target ion sources that will be employed for initial use at the HRIBF as well as prototype ion sources that show promise for future use for RIB applications.
Date: December 1995
Creator: Alton, G. D.
Partner: UNT Libraries Government Documents Department

A High Efficiency, Kinetic-Ejection Negative Ion Source for RIB Generation

Description: Chemically active radioactive species, diffused from RIB target materials, often arrive at the ionization chamber of the source in a variety of molecular forms. Because of the low probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules with conventional hot-cathode electron-impact ion sources, the species of interest are often distributed in several mass channels in the form of molecular side-band beams and consequently, their intensities are diluted. The sputter negative ion beam generation technique offers an efficient means for simultaneously dissociating and ionizing highly electronegative atomic species present in molecular carriers. We have incorporated these principles in the design and fabrication of a kinetic ejection negative ion source and evaluated its potential for generating {sup 17,18}F{sup {minus}} beams for the Holifield Radioactive Ion Beam Facility astrophysics research program. The source utilizes Cs{sup +} beams to bombard condensable fluorine compounds that emanate from a target material, such as Al{sub 2}O{sub 3}, and are transported to the cooled inner surface of a conical-geometry cathode where they are adsorbed. The energetic Cs{sup +} beams efficiently dissociate these molecules and sputter their constituents. Since the work functions of cesiated surfaces are low, highly electronegative species such as fluorine are efficiently ionized in the sputter-injection process. Measured efficiencies for ionizing atomic fluorine, dissociated from condensable compounds that are formed by reactions of SF{sub 6} with fibrous Al{sub 2}O{sub 3} material, exceed 6.5%. In this report, we describe the mechanical design features and principles of operation, and present emittance, F{sup {minus}} yield and ionization efficiency data derived from off-line, experimental evaluation of the source.
Date: October 5, 1998
Creator: Alton, G.D.; Liu, Y.; Murray, S.N. & Williams, C.
Partner: UNT Libraries Government Documents Department

Selection of RIB targets using ion implantation at the Holifield radioactive ion beam facility

Description: Among several major challenges posed by generating and accelerating adequate intensities of RIBs, selection of the most appropriate target material is perhaps the most difficult because of the requisite fast and selective thermal release of minute amounts of the short-lived product atoms from the ISOL target in the presence of bulk amounts of target material. Experimental studies are under way at the Oak Ridge National Laboratory (ORNL) which are designed to measure the time evolution of implanted elements diffused from refractory target materials which are candidates for forming radioactive ion beams (RIBs) at the Holifield Radioactive Ion Beam Facility (HRIBF). The diffusion coefficients are derived by comparing experimental data with numerical solutions to a one-dimensional form of Fick`s second law for ion implanted distributions. In this report, we describe the experimental arrangement, experimental procedures, and provide time release data and diffusion coefficients for releasing ion implanted {sup 37}Cl from Zr{sub 5}Si{sub 3} and {sup 75}As, {sup 79}Br, and {sup 78}Se from Zr{sub 5}Ge{sub 3} and estimates of the diffusion coefficients for{sup 35}Cl, {sup 63}Cu, {sup 65}Cu, {sup 69}Ga and {sup 71}Ga diffused from BN; {sup 35}Cl, {sup 63}Cu, {sup 65}Cu, {sup 69}Ga, {sup 75}As, and {sup 78}Se diffused from C; {sup 35}Cl, {sup 68}Cu, {sup 69}Ga, {sup 75}As, and {sup 78}Se diffused from Ta.
Date: December 31, 1995
Creator: Alton, G.D. & Dellwo, J.
Partner: UNT Libraries Government Documents Department

Advanced target concepts for RIB generation

Description: In this report, we describe highly permeable composite target matrices that simultaneously incorporate the short diffusion lengths, high permeabilities, and heat removal properties necessary to effect maximum diffusion release rates of short-lived, radioactive species as required for efficient radioactive ion beam (RIB) generation in nuclear physics and astrophysics research programs. The RIB species are generated by either fusion or fission nuclear reactions between high energy {sup 1}H, {sup 2}H, {sup 3}He or {sup 4}He ion beams and specific nuclei which make up the target material. The target materials may be used directly as small diameter particulates coated or uncoated with Re or Ir to minimize adsorption following diffusion release and eliminate sintering of the particulates at elevated temperatures; plated onto both sides of thin disks of C, for example; or plated, in thin layers, onto low density, Ir or Re coated carbon-bonded-carbon-fiber (CBCF) or reticulated-carbon-fiber (RCF) to form sponge-like composite target matrices; or in other cases, where applicable, the target material of interest can be grown in crystalline fibrous form and fabricated in woven mats of the target material to form a highly permeable fibrous structure.
Date: December 1, 1996
Creator: Alton, G.D.
Partner: UNT Libraries Government Documents Department