2,264 Matching Results

Search Results

Advanced search parameters have been applied.

Modeling and Optimization of Deflection Slits for Fast-Pulsing of a Low Energy Ion Beam

Description: This paper discusses research on modeling and optimization of deflection slits for fast-pulsing of a low energy ion beam. The authors also investigate simulated slit configurations that reduce the length of the fields along the beam axis, thus optimizing the pulsing mechanism.
Date: March 30, 2006
Creator: Bosca, Ryan & Weathers, Duncan L.
Partner: UNT Honors College

A System for Measurement of Negative-Ion Charge-Exchange Cross Sections

Description: A radio-frequency positive-ion source and a fifty-kilovolt linear accelerator were designed and constructed in order to produce sizable quantities of hydrogen, helium, nitrogen, neon, and argon. Plans were then made to equip this ion source with charge-exchange apparatus suitable for charge-exchange cross-sectional measurements. It is the purpose of this paper to present the design of the equipment and to present operational knowledge of the equipment and of ion beams which are producible.
Date: January 1960
Creator: Wingo, Dale T.
Partner: UNT Libraries

1-D Van der Waals Foams Heated by Ion Beam Energy Deposition

Description: One dimensional simulations of various initial average density aluminum foams (modeled as slabs of solid metal separated by low density regions) heated by volumetric energy deposition are conducted with a Lagrangian hydrodynamics code using a van der Waals equation of tate (EOS). The resulting behavior is studied to facilitate the design of future warm dense matter (WDM) experiments at LBNL. In the simulations the energy deposition ranges from 10 to 30 kJ/g and from 0.075 to 4.0 ns total pulse length, resulting in temperatures from approximately 1 o 4 eV. We study peak pressures and temperatures in the foams, expansion velocity, and the phase evolution. Five relevant time scales in the problem are identified. Additionally, we present a method for characterizing the level of inhomogeneity in a foam target as it is heated and the time it takes for a foam to homogenize.
Date: December 23, 2009
Creator: Zylstra, A. B.; Barnard, J. J. & More, R. M.
Partner: UNT Libraries Government Documents Department

Ion Motion inthe Adiabatic Focuser

Description: In this paper we numerically study the effect of ion motion in an adiabatic focuser, motivated by a recent suggestion that ion motion in an adiabatic focuser might be significant and even preclude operation of the focuser as previously envisioned. It is shown that despite ion motion the adiabatic focuser should work as well as originally envisioned.
Date: June 10, 2006
Creator: Henestroza, E.; Sessler, A.M. & Yu, S.S.
Partner: UNT Libraries Government Documents Department

Coincidence Method Applied to Ion Beam Measurement

Description: "A coincidence Geiger counter system was constructed for the absolute measurement of the activity of radioactive substances made in a cyclotron. The average beam current in the cyclotron can be calculated from the number of disintegrations per second observed, the half-life of the radioactive substance, and the reaction cross section" (p. 1).
Date: February 1952
Creator: Fultz, Stanley & Pool, M. L.
Partner: UNT Libraries Government Documents Department

Integration of scanning probes and ion beams

Description: We report the integration of a scanning force microscope with ion beams. The scanning probe images surface structures non-invasively and aligns the ion beam to regions of interest. The ion beam is transported through a hole in the scanning probe tip. Piezoresistive force sensors allow placement of micromachined cantilevers close to the ion beam lens. Scanning probe imaging and alignment is demonstrated in a vacuum chamber coupled to the ion beam line. Dot arrays are formed by ion implantation in resist layers on silicon samples with dot diameters limited by the hole size in the probe tips of a few hundred nm.
Date: March 30, 2005
Creator: Persaud, A.; Park, S.J.; Liddle, J.A.; Schenkel, T.; Bokor, J. & Rangelow, I.
Partner: UNT Libraries Government Documents Department

EXTRACTION COMPRESSION AND ACCELERATION OF HIGH LINE CHARGE DENSITY ION BEAMS

Description: High Energy Density Physics (HEDP) applications require high line charge density ion beams. An efficient method to obtain this type of beams is to extract a long pulse, high current beam from a gun at high energy, and let the beam pass through a decelerating field to compress it. The low energy beam-bunch is loaded into a solenoid and matched to a Brillouin flow. The Brillouin equilibrium is independent of the energy if the relationship between the beam size (a), solenoid magnetic field strength (B) and line charge density is such that (Ba){sup 2} is proportional to the line charge density. Thus it is possible to accelerate a matched beam at constant line charge density. An experiment, NDCX-1c is being designed to test the feasibility of this type of injectors, where we will extract a 1 microsecond, 100 mA, potassium beam at 160 keV, decelerate it to 55 keV (density {approx}0.2 {micro}C/m), and load it into a 2.5 T solenoid where it will be accelerated to 100-150 keV (head to tail) at constant line charge density. The head-to-tail velocity tilt can be used to increase bunch compression and to control longitudinal beam expansion. We will present the physics design and numerical simulations of the proposed experiment.
Date: May 20, 2005
Creator: Henestroza, Enrique; Henestroza, E.; Peters, C.; Yu, S.S.; Grote, D.P. & Briggs, R.J.
Partner: UNT Libraries Government Documents Department

Broad, intense, quiescent beam of singly charged metal ions obtained by extraction from self-sputtering plasma far above the runaway threshold

Description: Dense metal plasmas obtained by self-sputtering far above the runway threshold are well suited to generate intense quiescent ion beams. The dilemma of high current density and charge state purity can be solved when using target materials of low surface binding energy by utilizing non-resonant exchange reactions before ion extraction. Space-charge-limited quiescent beams of Cu+, Zn+, and Bi+ with ~;;10 mA/cm2 have been obtained through multi-aperture gridded ion extraction up to 45 kV from self-sputtering plasmas.
Date: May 19, 2009
Creator: Anders, Andre & Oks, Efim
Partner: UNT Libraries Government Documents Department

Cluster ion beam polishing for inertial confinement fusion target capsules

Description: Targets for Inertial Confinement Fusion (ICF) typically consist of a hollow, spherical capsule filled with a mixture of hydrogen isotopes. Typically, these capsules are irradiated by short, intense pulses of either laser light (``direct drive``) or laser-generated. x-rays (``indirect drive``), causing them to implode This compresses and heats the fuel, leading to thermonuclear fusion. This process is highly sensitive to hydrodynamic (e.g., Rayleigh-Taylor) instabilities, which can be initiated by imperfections in the target. Thus, target capsules must be spherical and smooth One of the lead capsule designs for the National Ignition Facility, a 1.8 MJ laser being built at Livermore, calls for a 2-mm- diam capsule with a 150-{micro}m-thick copper-doped beryllium wall. These capsules can be fabricated by sputter depositing the metal onto a spherical plastic mandrel. This results in surfaces with measured Rq`s of 50 to 150 nm, as measured with an atomic force microscope For optimal performance the roughness should be below 10 nm rms We have begun studying the use of ion cluster beam polishing as a means of improving the surface finish of as-deposited capsules In this approach, a batch of capsules would be agitated in a bounce pan inside a vacuum chamber during exposure to the cluster beam. This would ensure a uniform beam dose around the capsule. We have performed preliminary experiments on both Be flats and on a stationary Be capsule On the capsule, the measured Rq went from 64 nm before polishing to 15 nm after This result was obtained without any effort at process optimization. Similar smoothing was observed on the planar samples
Date: June 9, 1998
Creator: McEachern, R.
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

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

Rapid Melt and Resolidification of Surface Layers Using Intense, Pulsed Ion Beams Final Report

Description: The emerging technology of pulsed intense ion beams has been shown to lead to improvements in surface characteristics such as hardness and wear resistance, as well as mechanical smoothing. We report hereon the use of this technology to systematically study improvements to three types of metal alloys - aluminum, iron, and titanium. Ion beam tieatment produces a rapid melt and resolidification (RMR) of the surface layer. In the case of a predeposited thin-fihn layer, the beam mixes this layer into the substrate, Ieading to improvements that can exceed those produced by treatment of the alloy alone, In either case, RMR results in both crystal refinement and metastable state formation in the treated surface layer not accessible by conventional alloy production. Although more characterization is needed, we have begun the process of relating these microstructural changes to the surface improvements we discuss in this report.
Date: October 2, 1998
Creator: Renk, Timothy J. Turman, Bob Senft, Donna Sorensen, Neil R. Stinnett, Regan Greenly, John B. Thompson, Michael O. Buchheit, Rudolph G.
Partner: UNT Libraries Government Documents Department

ANALYSIS OF BEAM INDUCED PRESSURE INCREASES IN RHIC WARM VACUUM SECTIONS.

Description: With increasing intensity of gold and proton beams during recent RHIC operations, pressure rises of several decades were observed at a few RHIC warm vacuum sections. The pressure increases were analyzed and compared with the beam parameters such as ion species, bunch intensity, total intensity, number ofbunches, bunch spacing and beam loss. Most of these pressure increases were found to be consistent with those induced by either beam loss and/or electron multipacting.
Date: June 2, 2002
Creator: HSEUH,H.C.; SMART,L.A. & ZHANG,S.Y.
Partner: UNT Libraries Government Documents Department