ADVANCES IN IMPEDANCE THEORY (open access)

ADVANCES IN IMPEDANCE THEORY

We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.
Date: June 5, 2009
Creator: Stupakov, G.
Object Type: Article
System: The UNT Digital Library
Advances in processing of Ag-sheathed (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconductors. (open access)

Advances in processing of Ag-sheathed (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconductors.

Advances in the processing and fabrication of Ag-sheathed (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) high-T{sub c} superconductors by the powder-in-tube technique continue to bring this material closer to commercial applications. Enhancement of the transport critical current density (J{sub c}) of Ag-sheathed Bi-2223 tapes was achieved by increasing the packing density of the precursor powder, improving mechanical deformation, and adjusting the cooling rate. Long lengths (>150 m) of multifilamentary Bi-2223 tapes have been fabricated and carry critical currents (I{sub c}) of >50 A (J{sub c} {approx} 25 kA/cm{sup 2}) at 77 K in self-field. A 1260-m-long tape carried an I{sub c} of 18 A (J{sub c} {approx} 12 kA/cm{sup 2}) from end-to-end. Several prototype coils have been assembled from these long-length tapes. Recent progress in the fabrication of Bi-2223 tapes is presented in this paper.
Date: March 5, 1998
Creator: Balachandran, U.; Eror, N. G.; Haldar, P. & Lelovic, M.
Object Type: Article
System: The UNT Digital Library
Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime (open access)

Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime

A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for three years. The major outcome has been the demonstration of stable 100 MV/m gradient operation of a number of CLIC prototype structures. These structures were fabricated using the technology developed from 1994 to 2004 for the GLC/NLC linear collider initiative. One of the goals has been to refine the essential parameters and fabrication procedures needed to realize such a high gradient routinely. Another goal has been to develop structures with stronger dipole mode damping than those for GLC/NLC. The latter requires that the surface temperature rise during the pulse be higher, which may increase the breakdown rate. One structure with heavy damping has been RF processed and another is nearly finished. The breakdown rates of these structures were found to be higher by two orders of magnitude compared to those with equivalent acceleration mode parameters but without the damping features. This paper presents these results together with some of the earlier results from non-damped structures.
Date: July 5, 2012
Creator: Higo, Toshiyasu; Higashi, Yasuo; Matsumoto, Shuji; Yokoyama, Kazue; Adolphsen, Chris; Dolgashev, Valery et al.
Object Type: Article
System: The UNT Digital Library
Aerated atomization of coal water slurry (open access)

Aerated atomization of coal water slurry

In order to better understand the process of slurry atomization, it is important to observe the influence of fluid non-Newtonian rheological behavior on the spray formation process. As a first step, glycerin-water solutions have been atomized. This report describes findings of photographs taken during atomization. 19 figs.
Date: January 5, 1989
Creator: Buckner, H.N.; Sojka, P.E. & Lefebvre, A.H.
Object Type: Report
System: The UNT Digital Library
Aerial radiometric and magnetic survey: Bozeman National Topographic Map, Montana (open access)

Aerial radiometric and magnetic survey: Bozeman National Topographic Map, Montana

The results of analyses of the airborne gamma radiation and total magnetic field survey flown for the region identified as the Bozeman National Topographic Map NL12-8 are presented in Volume I and II of this report. The airborne data gathered are reduced by ground computer facilities to yield profile plots of the basic uranium, thorium, and potassium equivalent gamma radiation intensities, ratios of these intensities, aircraft altitude above the earth's surface, total gamma ray and earth's magnetic field intensity, correlated as a function of geologic units. The distribution of data within each geologic unit, for all surveyed map lines and tie lines, has been calculated and is included. Two sets of profiled data for each line are included with one set displaying the above-cited data. The second set includes only flight line magnetic field, temperature, pressure, altitude data plus magnetic field data as measured at a base station. A general description of the area, including descriptions of the various geologic units and the corresponding airborne data, is included also.
Date: April 5, 1979
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Aerodynamic levitation : an approach to microgravity. (open access)

Aerodynamic levitation : an approach to microgravity.

Measurements of the thermophysical and structural properties of liquid materials at high temperature have undergone considerable development in the past few years. Following improvements in electromagnetic levitation, aerodynamic levitation associated with laser heating has shown promise for assessing properties of different molten materials (metals, oxides, and semiconductors), preserving sample purity over a wide range of temperatures and under different gas environments. The density, surface tension and viscosity are measured with a high-speed video camera and an image analysis system. Results on nickel and alumina show that small droplets can be considered in the first approximation to be under microgravity conditions. Using a non-invasive contactless technique recently developed to measure electrical conductivity, results have been extended to variety of materials ranging from liquid metals and liquid semiconductors to ionically conducting materials. The advantage of this technique is the feasibility of monitoring changes in transport occurring during phase transitions and in deeply undercooled states.
Date: December 5, 2000
Creator: Glorieux, B.; Saboungi, M.-L.; Millot, F.; Enderby, J. & Rifflet, J.-C.
Object Type: Article
System: The UNT Digital Library
The age of the martian meteorite Northwest Africa 1195 and the differentiation history of the shergottites (open access)

The age of the martian meteorite Northwest Africa 1195 and the differentiation history of the shergottites

Samarium-neodymium isotopic analyses of unleached and acid-leached mineral fractions from the recently identified olivine-bearing shergottite Northwest Africa 1195 yield a crystallization age of 348 {+-} 19 Ma and an {var_epsilon}{sub Nd}{sup 143} value of +40.1 {+-} 1.3. Maskelynite fractions do not lie on the Sm-Nd isochron and appear to contain a martian surface component with low {sup 147}Sm/{sup 144}Nd and {sup 143}Nd/{sup 144}Nd ratios that was added during shock. The Rb-Sr system is disturbed and does not yield an isochron. Terrestrial Sr appears to have affected all of the mineral fractions, although a maximum initial {sup 87}Sr/{sup 86}Sr ratio of 0.701614 {+-} 16 is estimated by passing a 348 Ma reference isochron through the maskelynite fraction that is least affected by contamination. The high initial {var_epsilon}{sub Nd}{sup 143} value and the low initial {sup 87}Sr/{sup 86}Sr ratio, combined with the geologically young crystallization age, indicate that Northwest Africa 1195 is derived from a source region characterized by a long-term incompatible element depletion. The age and initial Sr and Nd isotopic compositions of Northwest Africa 1195 are very similar to those of Queen Alexandra Range 94201, indicating these samples were derived from source regions with nearly identical Sr-Nd isotopic systematics. These …
Date: April 5, 2007
Creator: Symes, S; Borg, L; Shearer, C & Irving, A
Object Type: Article
System: The UNT Digital Library
Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon (open access)

Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon

Rockfishes (Sebastes spp.) support one of the most economically important fisheries of the Pacific Northwest and it is essential for sustainable management that age estimation procedures be validated for these species. Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon ({sup 14}C) signal in the ocean environment that scientists have identified as a useful tracer and chronological marker in natural systems. In this study, we first demonstrated that fewer samples are necessary for age validation using the bomb-generated {sup 14}C signal by emphasizing the utility of the time-specific marker created by the initial rise of bomb-{sup 14}C. Second, the bomb-generated {sup 14}C signal retained in fish otoliths was used to validate the age and age estimation methodology of the quillback rockfish (Sebastes maliger) in the waters of southeast Alaska. Radiocarbon values from the first year's growth of quillback rockfish otoliths were plotted against estimated birth year producing a {sup 14}C time series spanning 1950 to 1985. The initial rise of bomb-{sup 14}C from pre-bomb levels ({approx} -90 {per_thousand}) occurred in 1959 {+-} 1 year and {sup 14}C levels rose relatively rapidly to peak {Delta}{sup 14}C values in 1967 (+105.4 {per_thousand}), with a subsequent declining trend …
Date: January 5, 2005
Creator: Kerr, L A; Andrews, A H; Munk, K; Coale, K H; Frantz, B R; Cailliet, G M et al.
Object Type: Article
System: The UNT Digital Library
Aging Studies of Sr-doped LaCrO3/YSZ/Pt Cells for an Electrochemical NOx Sensor (open access)

Aging Studies of Sr-doped LaCrO3/YSZ/Pt Cells for an Electrochemical NOx Sensor

The stability and NO{sub x} sensing performance of electrochemical cells of the structure Sr-doped LaCrO{sub 3-{delta}} (LSC)/yttria-stabilized zirconia (YSZ)/Pt are being investigated for use in NO{sub x} aftertreatment systems in diesel vehicles. Among the requirements for NO{sub x} sensor materials in these systems are stability and long lifetime (up to ten years) in the exhaust environment. In this study, cell aging effects were explored following extended exposure to a test environment of 10% O{sub 2} at operating temperatures of 600-700 C. The data show that aging results in changes in particle morphology, chemical composition and interfacial structure, Impedance spectroscopy indicated an initial increase in the cell resistance during the early stages of aging, which is correlated to densification of the Pt electrode. Also, x-ray photoelectron spectroscopy indicated formation of SrZrO{sub 2} solid state reaction product in the LSC, a process which is of finite duration. Subsequently, the overall cell resistance decreases with aging time due, in part, to roughening of YSZ-LSC interface, which improves interface adherence and enhances charge transfer kinetics at the O{sub 2}/YSZ/LSC triple phase boundary. This study constitutes a first step in the development of a basic understanding of aging phenomena in solid state electrochemical systems with …
Date: October 5, 2005
Creator: Song, S.; Martin, L. P.; Glass, R. S.; Murray, E. P.; Visser, J. H.; Soltis, R. E. et al.
Object Type: Article
System: The UNT Digital Library
Agriculture, greenhouse, wetland and other beneficial uses of geothermal fluids and heat (open access)

Agriculture, greenhouse, wetland and other beneficial uses of geothermal fluids and heat

The status for related beneficial uses including agriculture, greenhousing, and geothermal wetlands is presented. Data published for the geothermal fluids found in areas of China have been examined and compared with the geothermal fluids used in the agriculture evaluations in the United States. This comparison indicates that the geothermal fluids found in parts of China are similar to those used in the US agriculture experiments. Greenhousing is addressed largely from the standpoint of hardware systems and technology being employed or being proposed in the United States.
Date: April 5, 1981
Creator: Schmitt, R. C.
Object Type: Article
System: The UNT Digital Library
AGS Machine Studies (open access)

AGS Machine Studies

This report talks about the AGS Machine Studies
Date: October 5, 1994
Creator: Wei, J.
Object Type: Report
System: The UNT Digital Library
Air Conditioner Compressor Performance Model (open access)

Air Conditioner Compressor Performance Model

During the past three years, the Western Electricity Coordinating Council (WECC) Load Modeling Task Force (LMTF) has led the effort to develop the new modeling approach. As part of this effort, the Bonneville Power Administration (BPA), Southern California Edison (SCE), and Electric Power Research Institute (EPRI) Solutions tested 27 residential air-conditioning units to assess their response to delayed voltage recovery transients. After completing these tests, different modeling approaches were proposed, among them a performance modeling approach that proved to be one of the three favored for its simplicity and ability to recreate different SVR events satisfactorily. Funded by the California Energy Commission (CEC) under its load modeling project, researchers at Pacific Northwest National Laboratory (PNNL) led the follow-on task to analyze the motor testing data to derive the parameters needed to develop a performance models for the single-phase air-conditioning (SPAC) unit. To derive the performance model, PNNL researchers first used the motor voltage and frequency ramping test data to obtain the real (P) and reactive (Q) power versus voltage (V) and frequency (f) curves. Then, curve fitting was used to develop the P-V, Q-V, P-f, and Q-f relationships for motor running and stalling states. The resulting performance model ignores the …
Date: September 5, 2008
Creator: Lu, Ning; Xie, YuLong & Huang, Zhenyu
Object Type: Report
System: The UNT Digital Library
AIR PERMIT COMPLIANCE FOR WASTE RETRIEVAL OEPRATIONS INVOLVING MULTI-UNIT OPERATIONS (open access)

AIR PERMIT COMPLIANCE FOR WASTE RETRIEVAL OEPRATIONS INVOLVING MULTI-UNIT OPERATIONS

Since 1970, approximately 38,000 suspect-transuranic and transuranic waste containers have been placed in retrievable storage on the Hanford Site in the 200 Areas burial grounds. Hanford's Waste Retrieval Project is retrieving these buried containers and processing them for safe storage and disposition. Container retrieval activities require an air emissions permit to account for potential emissions of radionuclides. The air permit covers the excavation activities as well as activities associated with assaying containers and installing filters in the retrieved transuranic containers lacking proper venting devices. Fluor Hanford, Inc. is required to track radioactive emissions resulting from the retrieval activities. Air, soil, and debris media contribute to the emissions and enabling assumptions allow for calculation of emissions. Each of these activities is limited to an allowed annual emission (per calendar year) and .contributes to the overall total emissions allowed for waste retrieval operations. Tracking these emissions is required to ensure a permit exceedance does not occur. A tracking tool was developed to calculate potential emissions in real time sense. Logic evaluations are established within the tracking system to compare real time data against license limits to ensure values are not exceeded for either an individual activity or the total limit. Data input …
Date: November 5, 2007
Creator: FM, SIMMONS
Object Type: Article
System: The UNT Digital Library
Air quality impacts analysis for area G. Final report (open access)

Air quality impacts analysis for area G. Final report

The impact of fugitive radioactive emissions from the disposal site, Area G, was evaluated in support of site characterization for the Performance Assessment and for the Radioactive Air Emissions Management (RAEM) program. Fugitive emissions of tritiated water and contaminated windblown dust were considered. Data from an extensive field measurement program were used to estimate annual emissions of tritiated water. Fugitive dust models were used to calculate estimates of the annual emissions of windblown dust. These estimates were combined with data on contamination levels in surface soils to develop annual emission rates for specific radionuclides: tritium, uranium-238, cesium-137, plutonium-238, plutonium-239,240, and strontium-90. The CAP-88 atmospheric transport model was used to predict areas potentially affected by long-term dust deposition and atmospheric concentrations. The annual emission rate of tritiated water was estimated from the field data to be 14.0 Ci/yr. The emission rate of soil-borne radionuclides from open areas and from soils handling operations totaled less than 1x10{sup -4} Ci/yr. The CAP-88 results were used to develop effective dose equivalents (EDEs) for receptor locations downwind of Area G. All EDEs were several orders of magnitude below the national standard of 10 mrem/yr. Fugitive air emissions from Area G were found not to pose …
Date: July 5, 1995
Creator: Kowalewsky, K.; Eklund, B. & Vold, E. L.
Object Type: Report
System: The UNT Digital Library
AISI/DOE Technology Roadmap Program: Behavior of Phosphorus in DRI/HBI During Electric Furnace Steelmaking (open access)

AISI/DOE Technology Roadmap Program: Behavior of Phosphorus in DRI/HBI During Electric Furnace Steelmaking

Many common scrap substitutes such as direct reduced iron pellets (DRI), hot briquetted iron (HBI), iron carbide, etc., contain significantly higher levels of phosphorus steelmaking for the production of higher quality steels, control of phosphorus levels in the metal will become a concern. This study has developed a more complete understanding of the behavior of phosphorus in DRI during EAF steelmaking, through a thorough investigation of the kinetics and thermodynamics of phosphorus transfer in the EAF based upon laboratory and plant experiments and trials. Laboratory experiments have shown that phosphorus mass transfer between oxide and metallic phases within commercial direct reduced iron pellets occurs rapidly upon melting according to the local equilibrium for these phases. Laboratory kinetic experiments indicate that under certain conditions, phosphorus mass transfer between slag and metal is influenced by dynamic phenomena, which affect the mass transfer coefficient for the reaction and/or the slag metal interfacial area. Plant trials were conducted to directly evaluate the conditions of mass transfer in the electric furnace and to determine the effects of different scrap substitute materials upon the slag chemistry, the behavior of phosphorus in the steel, and upon furnace yield. The data from these trials were also used to …
Date: October 5, 2001
Creator: Frueham, Richard J. & Manning, Christopher P.
Object Type: Report
System: The UNT Digital Library
ALARA Center of Technology -- resource guide (open access)

ALARA Center of Technology -- resource guide

The purpose is to provide a source of information that can be used to assist personnel in the planning, training, and execution of radiological work using the principles of ALARA. This document is not intended to replace HNF or WHC Control Manual requirements. The ALARA Tools-List provides detailed information on the use and procurement of engineered controls, mockup training guidelines, and good radiological work practices that have been proven to be ALARA.
Date: February 5, 1998
Creator: Waggoner, L. O.
Object Type: Article
System: The UNT Digital Library
Albeni Falls Wildlife Mitigation Project, 2008 Annual Report. (open access)

Albeni Falls Wildlife Mitigation Project, 2008 Annual Report.

The Albeni Falls Interagency Work Group (AFIWG) was actively involved in implementing wildlife mitigation activities in late 2007, but due to internal conflicts, the AFIWG members has fractionated into a smaller group. Implementation of the monitoring and evaluation program continued across protected lands. As of 2008, The Albeni Falls Interagency Work Group (Work Group) is a coalition comprised of wildlife managers from three tribal entities (Kalispel Tribe, Kootenai Tribe, Coeur d Alene Tribe) and the US Army Corps of Engineers. The Work Group directs where wildlife mitigation implementation occurs in the Kootenai, Pend Oreille and Coeur d Alene subbasins. The Work Group is unique in the Columbia Basin. The Columbia Basin Fish and Wildlife Authority (CBFWA) wildlife managers in 1995, approved what was one of the first two project proposals to implement mitigation on a programmatic basis. The maintenance of this kind of approach through time has allowed the Work Group to implement an effective and responsive habitat protection program by reducing administrative costs associated with site-specific project proposals. The core mitigation entities maintain approximately 9,335 acres of wetland/riparian habitats in 2008.
Date: August 5, 2009
Creator: Soults, Scott
Object Type: Report
System: The UNT Digital Library
Alcoa North American Extrusions Implements Energy Use Assessments at Multiple Facilities: Office of Industrial Technologies (OIT) BestPractices Aluminum Assessment Case Study (open access)

Alcoa North American Extrusions Implements Energy Use Assessments at Multiple Facilities: Office of Industrial Technologies (OIT) BestPractices Aluminum Assessment Case Study

This case study is the latest in a series on industrial firms who are implementing energy efficient technologies and system improvements into their manufacturing processes. The case studies document the activities, savings, and lessons learned on these projects.
Date: August 5, 2001
Creator: Energy, U.S. Department of
Object Type: Book
System: The UNT Digital Library
Algorithms for deriving crystallographic space-group information. II: Treatment of special positions (open access)

Algorithms for deriving crystallographic space-group information. II: Treatment of special positions

Algorithms for the treatment of special positions in 3-dimensional crystallographic space groups are presented. These include an algorithm for the determination of the site-symmetry group given the coordinates of a point, an algorithm for the determination of the exact location of the nearest special position, an algorithm for the assignment of a Wyckoff letter given the site-symmetry group, and an alternative algorithm for the assignment of a Wyckoff letter given the coordinates of a point directly. All algorithms are implemented in ISO C++ and are integrated into the Computational Crystallography Toolbox. The source code is freely available.
Date: October 5, 2001
Creator: Grosse-Kunstleve, Ralf W. & Adams, Paul D.
Object Type: Article
System: The UNT Digital Library
Alignment tolerances of IR quadrupoles in the LHC (open access)

Alignment tolerances of IR quadrupoles in the LHC

Luminosity in the LHC will depend critically on the alignment of the triplet quadrupoles. These quadrupoles are closest to the interaction points (IPs), have large gradients and the {beta} functions have their largest values within these quadrupoles. Within a triplet, the cold masses of the Q1 and Q3 quadrupoles will be housed in separate cryostats while Q2a and Q2b will be placed in a single cryostat. The absolute alignments of Q1, Q3 and the Q2a/Q2b pair with respect to the desired axes will be determined during installation. The relative alignment of Q2a and Q2b however will be fixed once they are placed in their common cryostat at Fermilab. In this note, we examine the required relative alignment tolerances of Q2a and Q2b. An early study of some alignment tolerances was done by Weisz [1].
Date: November 5, 1999
Creator: Sen, Tanaji
Object Type: Article
System: The UNT Digital Library
All Fiber Technology for High-Energy Petawatt Front End Laser Systems (open access)

All Fiber Technology for High-Energy Petawatt Front End Laser Systems

We are developing an all fiber front end for the next generation high-energy petawatt (HEPW) laser at Lawrence Livermore National Laboratory (LLNL). The ultimate goal of the LLNL HEPW effort is to generate 5-kJ pulses capable of compression to 5ps at 1053nm, enabling advanced x-ray backlighters and possible demonstration of fast ignition. We discuss the front-end of the laser design from the fiber master oscillator, which generates the mode-locked 20nm bandwidth initial pulses through the 10mJ output of the large flattened mode (LFM) fiber amplifier. Development of an all fiber front end requires technological breakthroughs in the key areas of the master oscillator and fiber amplification. Chirped pulse amplification in optical fibers has been demonstrated to 1mJ. Further increase is limited by the onset of stimulated Raman scattering (SRS). We have recently demonstrated a new flattened mode fiber technology, which reduces peak power for a given energy and thus the onset of SRS. Controlled experiments with 1st generation fibers yielded 0.5mJ of energy while significantly increasing the point at which nonlinear optical effects degrade the amplified pulse. In this paper we will discuss our efforts to extend this work to greater than 20mJ using our large flattened mode fiber amplifier.
Date: September 5, 2003
Creator: Dawson, J W; Liao, Z M; Jovanovic, I; Wattellier, B; Beach, R; Payne, S A et al.
Object Type: Article
System: The UNT Digital Library
All One-loop Maximally Helicity Violating Gluonic Amplitudes in QCD (open access)

All One-loop Maximally Helicity Violating Gluonic Amplitudes in QCD

We use on-shell recursion relations to compute analytically the one-loop corrections to maximally-helicity-violating n-gluon amplitudes in QCD. The cut-containing parts have been computed previously; our work supplies the remaining rational parts for these amplitudes, which contain two gluons of negative helicity and the rest positive, in an arbitrary color ordering. We also present formulae specific to the six-gluon cases, with helicities (-+-+++) and (-++-++), as well as numerical results for six, seven, and eight gluons. Our construction of the n-gluon amplitudes illustrates the relatively modest growth in complexity of the on-shell-recursive calculation as the number of external legs increases. These amplitudes add to the growing body of one-loop amplitudes known for all n, which are useful for studies of general properties of amplitudes, including their twistor-space structure.
Date: July 5, 2006
Creator: Berger, Carola F.; Bern, Zvi; Dixon, Lance J.; Forde, Darren & Kosower, David A.
Object Type: Report
System: The UNT Digital Library
Allinea DDT as a Parallel Debugging Alternative to Totalview (open access)

Allinea DDT as a Parallel Debugging Alternative to Totalview

Totalview, from the Etnus Corporation, is a sophisticated and feature rich software debugger for parallel applications. As Totalview has gained in popularity and market share its pricing model has increased to the point where it is often prohibitively expensive for massively parallel supercomputers. Additionally, many of Totalview's advanced features are not used by members of the scientific computing community. For these reasons, supercomputing centers have begun to search for a basic parallel debugging tool which can be used as an alternative to Totalview. As the cost and complexity of Totalview has increased over the years, scientific computing centers have started searching for a viable parallel debugging alternative. DDT (Distributed Debugging Tool) from Allinea Software is a relatively new parallel debugging tool which aims to provide much of the same functionality as Totalview. This review outlines the basic features and limitations of DDT to determine if it can be a reasonable substitute for Totalview. DDT was tested on the NERSC platforms Bassi, Seaborg, Jacquard and Davinci with Fortran90, C, and C++ codes using MPI and OpenMP for parallelism.
Date: March 5, 2007
Creator: Antypas, K.B.
Object Type: Report
System: The UNT Digital Library
Alpha-Decay in Isotopes of Atomic Number Less Than 83 (open access)

Alpha-Decay in Isotopes of Atomic Number Less Than 83

Some time ago we started work in an attempt to observe alpha-particle decay in isotopes of atomic number less than 83. In the first experiments, thin targets of gold leaf were bombarded with 190-Mev deuterons in the 184-inch cyclotron. Two alpha-decay periods were observed in these targets; one of 0.7 minutes half-life and another of 4.3 minutes half-life. The alpha-particle energies were 5.7 and 5.2 Mev, respectively. Chemical separations proved that the 4.3-minute period is due to a gold isotope and suggested that the 0.7-minute period is due to a mercury isotope. The mass numbers of these new isotopes have not been determined. However, the results of excitation-functions in the production of the gold isotope by bombarding gold and platinum with protons suggest that its mass number lies in the range 185-188. The work on this isotope indicates that the alpha to electron capture branching ratio is of the order of magnitude of 10{sup -4}, and that positron activity accompanies the 4.3-minute alpha-period.
Date: September 5, 1949
Creator: Thompson, S. G.; Ghiorso, A.; Radmussen, J. O. & Seaborg, G. T.
Object Type: Report
System: The UNT Digital Library