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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

A High-Temperature, "Volume-Type" ECR Ion Source for RIB Generation

Description: A high temperature, low-charge-state, "volume-type" source has been designed for use in the nuclear physics and nuclear astrophysics research radioactive ion beam (RIB) programs at the Holifield Radioactive Ion beam Facility (HRIBF). The source utilizes electromagnetic coils to generate a large and uniformly distributed central magnetic field with magnitude (875 G) chosen to be in electron-cyclotron-resonance (ECR) with single- frequency (2.45 GHz) microwave radiation. Among the features of the source includti a variable mirror-ratio at ion extraction as required for optimizing low-charge state ion beam generation, a right-hand, circularly-polarized RF injection system to overcome the relatively-low, cutoff-density, (nC - 7.4x10'0/cm3) associated with the use of 2.45 GHz microwave radiatiom, and a high temperature, Ir- or Re-coated-Ta plasma chamber to reduce the residence times of radioactive species that are adsorbed on the walls of the chamber. No provisions are made for radial plasma confinement due to the sensitivity of permanent magnets to degradation by the huge fluxes of neutrons incumbent during target irradiation, routinely used for this purpose. Aspects of the design features of the source are described in this report.
Date: March 29, 1999
Creator: Alton, G.D.; Liu, Y.; Reed, C.A.; Williams, C. & Zhang, T.
Partner: UNT Libraries Government Documents Department

Overview of linac applications at future radioactive beam facilities

Description: There is considerable interest worldwide in the research which could be done at a next generation, advanced radioactive beam facility. To generate high quality, intense beams of accelerated radionuclides via the {open_quotes}isotope separator on-line{close_quotes} (ISOL) method requires two major accelerator components: a high power (100 kW) driver device to produce radionuclides in a production target/ion source complex, and a secondary beam accelerator to produce beams of radioactive ions up to energies on the order of 10 MeV per nucleon over a broad mass range. In reviewing the technological challenges of such a facility, several types of modem linear accelerators appear well suited. This paper reviews the properties of the linacs currently under construction and those proposed for future facilities for use either as the driver device or the radioactive beam post-accelerator. Other choices of accelerators, such as cyclotrons, for either the driver or secondary beam devices of a radioactive beam complex will also be compared. Issues to be addressed for the production accelerator include the choice of ion beam types to be used for cost-effective production of radionuclides. For the post-accelerator the choice of ion source technology is critical and dictates the charge-to-mass requirements at the injection stage.
Date: November 1, 1996
Creator: Nolen, J.A.
Partner: UNT Libraries Government Documents Department

Study of low-lying resonant states in 16F using an 15O radioactiveion beam

Description: A 120 MeV {sup 15}O radioactive ion beam with an intensity on target of 4.5 x 10{sup 4} pps has been developed at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This beam has been used to study the level structure of {sup 16}F at low energies via the p({sup 15}O,p) reaction using the thick target inverse kinematics method on a polyethylene target. The experimental excitation function was analyzed using R-matrix calculations. Significantly improved values for the level widths of the four low-lying states in 16F are reported. Good agreement with the theoretical spectroscopic factors is also obtained.
Date: January 22, 2007
Creator: Lee, D.W.; Perajarvi, K.; Powell, J.; O'Neil, J.P.; Moltz, D.M.; Goldberg, V.Z. et al.
Partner: UNT Libraries Government Documents Department

Study of the 11C(p,gamma) reaction via the indirect d(11C,12N)ntransfer reaction

Description: The {sup 11}C(p,{gamma}){sup 12}N reaction is expected to be an important branch point in supermassive low-metallicity stars because it could produce CNO seed nuclei before the traditional triple-alpha process turns on. In the present work, the d({sup 11}C, {sup 12}N)n transfer reaction was employed to evaluate this reaction using a radioactive ion beam of 150 MeV {sup 11}C with 6 x 10{sup 5} ions/s on target from the BEARS project at the 88-inch cyclotron at Lawrence Berkeley National Laboratory. Excellent agreement was obtained between the experimental cross sections ({theta}{sub c.m.} = 10.9{sup o} to 71.5{sup o}) and DWBA calculations. The asymptotic normalization coefficient was deduced to be (C{sub eff}{sup 12N}){sup 2} = (C{sub p1/2}{sup 12N}){sup 2} + (C{sub p3/2}{sup 12N}){sup 2} = 1.83 {+-} 0.27 fm{sup -1}.
Date: January 7, 2008
Creator: Lee, Dongwon; Powell, James; Perajarvi, Kari; Guo, Fanqing; Moltz, Dennis & Cerny, Joseph
Partner: UNT Libraries Government Documents Department

1+-n+ ECR ION SOURCE DEVELOPMENT TEST STAND

Description: A test stand for the investigation of 1+-n+ charge boosting using an ECR ion sources is currently being assembled at the Texas A&M Cyclotron Institute. The ultimate goal is to relate the charge-boosting of ions of stable species to possible charge-boosting of ions of radioactive species extracted from the diverse, low-charge-state ion sources developed for radioactive ion beams.
Date: April 7, 2006
Creator: May, Donald P.
Partner: UNT Libraries Government Documents Department

Accelerator complex for a radioactive ion beam facility at ATLAS

Description: Since the superconducting heavy ion linac ATLAS is an ideal post-accelerator for radioactive beams, plans are being developed for expansion of the facility with the addition of a driver accelerator, a production target/ion source combination, and a low q/m pre-accelerator for radioactive ions. A working group including staff from the ANL Physics Division and current ATLAS users are preparing a radioactive beam facility proposal. The present paper reviews the specifications of the accelerators required for the facility.
Date: June 1, 1995
Creator: Nolen, J.A.
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

A combined thermal dissociation and electron impact ionization source for RIB generation

Description: The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for RIB applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, in principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility (HRIBF), now under construction at the Oak Ridge National Laboratory. 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

Ionization efficiency and effusive delay time characterization of high temperature target-ion sources for RIB generation

Description: Ion sources for radioactive ion beam (RIB) generation must efficiently ionize short-lived-radioactive nuclei released from on-line targets with minimal delay times. Delay times attributable to interactions between chemically active species and surfaces of the vapor transport system which are long compared to the half-life of the desired radioactive atom and/or low ionization efficiency of the target/ion source (TIS) will result in a severe reduction of the RM intensity available for research. We have developed complementary off-line techniques for directly measuring both effusive delay times and ionization efficiencies for chemically active species in high temperature TISs using only the stable complements of the radioactive element of interest. Equipment, designed and developed for these measurements, include: a high-temperature Ta valve; a differentially cooled injection nozzle; and a gaseous flow measurement and control system. These techniques are employed in a systematic investigation of fluorine transport and ionization in an electron-beam-plasma target/ion source (EBPTIS) designed for initial use at the Holifield Radioactive Ion Beam Facility (HRIBF).
Date: December 1, 1996
Creator: Welton, R.F.; Alton, G.D.; Murray, S.N. & Cui, B.
Partner: UNT Libraries Government Documents Department

A combination thermal dissociation/electron impact ionization source for RIB generation

Description: The flourishing interest in radioactive ion beams (RIBs) with intensities adequate for astrophysics and nuclear physics research place a premium on targets that will swiftly release trace amounts of short lived radio-nuclei in the presence of bulk quantities of target material and ion sources that have the capability of efficiently ionizing the release products. Because of the low probability of simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules containing the element of interest with conventional, hot-cathode, electron-impact ion sources, the species of interest is often distributed in several mass channels in the form of molecular sideband beams and, consequently, the intensity is diluted. The authors 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 to address these problems. 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, 1996
Creator: Alton, G.D.; Cui, B. & Welton, R.F.
Partner: UNT Libraries Government Documents Department

The production and transport of radioactive {sup 17}F at ATLAS for research

Description: A secondary beam of radioactive {sup 17}F was produced at the ATLAS accelerator and delivered to an experimental target station with an intensity of as much as 5{circ}10{sup 5} ions/s for use in the research program. Beams of {sup 17}F were produced via the p({sup 17}O, {sup 17}F)n or d({sup 16}O, {sup 17}F)n reactions by bombarding a gas-filled cell with up to 300 pnA beams of {sup 17}O or {sup 16}O from the ATLAS superconducting linac. The gas target, with HAVAR windows, was maintained at pressures as high as 500 Torr. The beam quality was dominated by small-angle scattering in the gas cell windows, by the reaction kinematics and beamline acceptance. Detailed beam parameters are presented. Plans for relocation of the target to allow improved capture efficiency and acceleration or de-acceleration of the secondary beam will also be discussed.
Date: June 1, 1997
Creator: Harss, B.; Berger, J.C. & Borasi, F.
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

Status of U.S. Plans for an Advanced ISOL Facility, A Brief Report

Description: A brief discussion is provided of the current status of plans to build an advanced ISOL radioactive ion beam facility in the US. Designs for this new facility, which was recommended as the next major construction project of the DOE Nuclear Physics Program Office, have been proposed by two US national laboratories, Argonne National Laboratory and Oak Ridge National Laboratory. The new facility will provide orders-of-magnitude higher radioactive beam currents than existing facilities of this type and will cost in the range of $250 million.
Date: November 13, 1998
Creator: Bertrand, F.E.
Partner: UNT Libraries Government Documents Department

A new concept positive (negative) surface ionization source for RIB applications

Description: A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed. fabricated, and tests completed which can operate in either positive- or negative-ion beam generation modes without mechanical changes to the source. The highly permeable, composite Ir/C has an intrinsic work function of 0 = 5.29 eV and can be used directly for the generation of positive-ion beams of highly electropositive elements. For negative-surface ionization, the work function is lowered by dynamic flow of a highly electropositive adsorbate such as Cs through the ionizer matrix. The results of initial testing indicate that the source is reliable, stable and easy to operate, with efficiencies for Cs{sup +} estimated to exceed 60% and as high as {approximately}50% for F{sup -} generation. The design features, operational principles, and initial performance of the source for generating Cs{sup +} and F{sup -}, when operated with Cs, are discussed in this article.
Date: December 31, 1996
Creator: Alton, G.D.; Welton, R.F. & Cui, B.
Partner: UNT Libraries Government Documents Department

Isobar Separators for Radioactive Ion Beam Facilities

Description: A radioactive ion beam facility - in short a RIB facility - produces ions of short-lived nuclei and accelerates them to energies of 0.1�10 MeV per nucleon or even higher. In this process it is important that the resulting RIB beams are free from nuclei of neighboring isobars or of neighboring elements. This task requires the production and ionization of the nuclei of interest as well as separating them from all others with a high-mass resolving power and small-mass cross contaminations. When constructing such a facility it also is very important to find ways that allow the accelerated ions to be provided to different experiments at least quasi simultaneously.
Date: October 5, 1998
Creator: Garrett, J.D. & Wollnik, H.
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

Nuclear structure studies of exotic nuclei. Progress report, September 1, 1996--August 31, 1997

Description: This report concerns the current status of the project `Nuclear Structure Studies of Exotic Nuclei`. Discussed in this report are experiments performed during the current year, status of data analysis, plans and proposals for future experiments, conferences attended, equipment purchases related to the project, and use of graduate and undergraduate students.
Date: May 1, 1997
Creator: Winger, J.A.
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