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First CSDP (Continental Scientific Drilling Program)/thermal regimes core hole project at Valles Caldera, New Mexico (VC-1): Drilling report
This report is a review and summary of the core drilling operations of the first Valles Caldera research borehole (VC-1) under the Thermal Regimes element of the Continental Scientific Drilling Program (CSDP). The project is a portion of a broader program that seeks to answer fundamental scientific questions about magma, rock/water interactions, and volcanology through shallow (<1-km) core holes at Long Valley, California; Salton Sea, California; and the Valles Caldera, New Mexico. The report emphasizes coring operations with reference to the stratigraphy of the core hole, core quality description, core rig specifications, and performance. It is intended to guide future research on the core and in the borehole, as well as have applications to other areas and scientific problems in the Valles Caldera. The primary objectives of this Valles Caldera coring effort were (1) to study the hydrogeochemistry of a subsurface geothermal outflow zone of the caldera near the source of convective upflow, (2) to obtain structural and stratigraphic information from intracaldera rock formations in the southern ring-fracture zone, and (3) to obtain continuous core samples through the youngest volcanic unit in Valles Caldera, the Banco Bonito rhyolite (approximately 0.1 Ma). All objectives were met. The high percentage of core …
Date:
February 1, 1987
Creator:
Rowley, J.; Hawkins, W. & Gardner, J. (comps.)
Object Type:
Report
System:
The UNT Digital Library
User needs: is a survey the answer
Some of the ramifications of user needs, user satisfaction, and the survey as a shaper of library policy are discussed. The presentation is in three parts: philosophical thinking on user needs and satisfaction, a modest tutorial on survey methodology, and a brief review of the Sandia National Laboratory Technical Library's use of surveys for information gathering and decision making. (RWR)
Date:
January 1, 1980
Creator:
Gardner, J.L.
Object Type:
Article
System:
The UNT Digital Library
Formaldehyde Absorption toward W51
We have measured formaldehyde (H{sub 2}CO) absorption toward the HII region complex W51A (G49.5-0.4) in the 6 cm and 2 cm wavelength rotational transitions with angular resolution of approximately 4 inch. The continuum HII region shows a large, previously undetected shell structure 5.5 pc along the major axis. We observe no H{sub 2}CO emission in regions of low continuum intensity. The absorption, converted to optical depth, shows a higher degree of clumping than previous maps at lower resolution. The good S/N of the maps allows accurate estimation of the complicated line profiles, showing some of the absorbing clouds to be quite patchy. We list the properties of the opacity spectra for a number of positions both in the clumps and in the more diffuse regions of the absorbing clouds, and derive column densities for the 1{sub 11} and 2{sub 12} rotational levels of ortho-formaldehyde.
Date:
April 1, 1988
Creator:
Kogut, A.; Smoot, G. F.; Bennett, C. L. & Petuchowski, S. J.
Object Type:
Article
System:
The UNT Digital Library
Reaction cross-section calculations using new experimental and theoretical level structure data for deformed nuclei
A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been used to construct sets of discrete states with energy 0 to 1.5 MeV in /sup 176/Lu and /sup 236/Np. These data were used as part of the input for calculation of isomer production cross-section ratios in the /sup 175/Lu(n,..gamma..)/sup 176/Lu and /sup 237/Np(n,2n)/sup 236/Np reactions. In order to achieve agreement with experiment, it has been found necessary to include in the modeled set many rotational bands (35 to 95), which are comprised of hundreds of levels with their gamma-ray branching ratios. It is essential that enough bands be included to produce a representative selection of K quantum numbers in the de-excitation cascade. 20 refs., 3 figs., 3 tabs.
Date:
October 5, 1984
Creator:
Hoff, R. W.; Gardner, D. G. & Gardner, M. A.
Object Type:
Article
System:
The UNT Digital Library
Detailed photonuclear cross-section calculations and astrophysical applications
We have investigated the role of an isomeric state and its coupling to the ground state (g.s.) via photons and neutron inelastic scattering in a stellar environment by making detailed photonuclear and neutron cross-section calculations for /sup 176/Lu and /sup 210/Bi. In the case of /sup 176/Lu, the g.s. would function as an excellent galactic slow- (s-) process chronometer were it not for the 3.7-h isomer at 123 keV. Our calculations predicted much larger photon cross sections for production of the isomer, as well as a lower threshold, than had been assumed based on earlier measurements. These two factors combine to indicate that an enormous correction, a factor of 10/sup 7/, must be applied to shorten the current estimate of the half-life against photoexcitation of /sup 176/Lu as a function of temperature. This severely limits the use of /sup 176/Lu as a stellar chronometer and indicates a significantly lower temperature at which the two states reach thermal equilibrium. For /sup 210/Bi, our preliminary calculations of the production and destruction of the 3 /times/ 10/sup 6/ y isomeric state by neutrons and photons suggest that the /sup 210/Bi isomer may not be destroyed by photons as rapidly as assumed in certain …
Date:
June 15, 1989
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Absolute dipole gamma-ray strength functions for /sup 176/Lu
We have derived absolute dipole strength-function information for /sup 176/Lu from an average resonance capture study of /sup 175/Lu with 2-keV neutrons, and from neutron capture cross-section measurements with neutrons from 30 keV to about 1 MeV. We found that we needed to increase our previous estimate of the relative M1/E1 strengths near 5 MeV by a factor of 3, and to revise downward the absolute magnitude of our E1 strength function. We accomplished the latter, while still maintaining continuity with the photonuclear data, by adjusting the one free parameter in our line shape. The present E1 and M1 strengths now seem correct both near the neutron separation energy and also around 1 MeV.
Date:
August 29, 1984
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Reaction cross-section calculations using new experimental and theoretical level structure data for deformed nuclei
A technique for modeling level structures of odd-odd nuclei has been used to construct sets of discrete states with energies in the range 0 to 1.5 MeV for several nuclei in the rare-earth and actinide regions. The accuracy of the modeling technique was determined by comparison with experimental data. Examination was made of what effect the use of these new, more complete sets of discrete states has on the calculation of level densities, total reaction cross sections, and isomer ratios. 9 refs.
Date:
May 1, 1985
Creator:
Hoff, R. W.; Gardner, D. G. & Gardner, M. A.
Object Type:
Article
System:
The UNT Digital Library
Isomer ratio calculations using modeled discrete levels
Isomer ratio calculations were made for the reactions: /sup 175/Lu(n,..gamma..)/sup 176m,g/Lu, /sup 175/Lu(n,2n)/sup 174m,g/Lu, /sup 237/Np(n,2n)/sup 236m,g/Np, /sup 241/Am(n,..gamma..)/sup 242m,g/Am, and /sup 243/Am(n,..gamma..)/sup 244m,g/Am using modeled level structures in the deformed, odd-odd product nuclei. The hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment. Many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers. The levels of each band must be extended to appropriately high values of angular momentum.
Date:
October 16, 1984
Creator:
Gardner, M. A.; Gardner, D. G. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Absolute dipole gamma-ray strength functions for /sup 176/Lu. Supplement
We have derived absolute dipole strength-function information for /sup 176/Lu from an average resonance capture study of /sup 175/Lu with 2-keV neutrons and from neutron capture cross-section measurements with neutrons from 30 keV to about 1 MeV. We found that we needed to increase our previous estimate of the relative M1/E1 strengths near 5 MeV by a factor of 3 and to revise downward the absolute magnitude of our E1 strength function. We accomplished the latter, while still maintaining continuity with the photonuclear data, by adjusting the one free parameter in our line shape. The present E1 and M1 strengths now seem correct both near the neutron separation energy and also around 1 MeV.
Date:
October 16, 1984
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Dipole strength functions in the actinide mass region
We have calculated a number of neutron- and photon-induced reactions for the actinide nuclei /sup 232/Th, /sup 238/U, and /sup 237/Np. By fitting average resonance capture (ARC) measurements and total neutron capture data, we deduced absolute dipole strength functions for /sup 233/Th and /sup 239/U. We have found that the M1/E1 ratio is the same as in the /sup 176/Lu case, but the total transition strength was larger by about 27%. 17 refs., 4 figs., 1 tab.
Date:
July 15, 1987
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Isomer ratio calculations using modeled discrete levels
We have calculated isomer ratios for the /sup 175/Lu(n,..gamma..), /sup 175/Lu(n,2n), /sup 237/Np(n,2n), /sup 241/Am(n,..gamma..), and /sup 243/Am(n,..gamma..) reactions using modeled level structures in the deformed, odd-odd product nuclei. We find: that the hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment, that many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers, and that the levels of each band must be extended to appropriately high values of angular momentum. 8 references.
Date:
August 29, 1984
Creator:
Gardner, M. A.; Gardner, D. G. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Experimental database and design concept for a 1-MW, 200-keV neutral-beam line based on a SITEX negative ion source
Scaling studies for a SITEX negative ion source to produce 200-keV, 10-A, long pulse D/sup -/ beams are under way at Oak Ridge National Laboratory (ORNL). Designs have been restricted to the use of established techniques and reasonably well-demonstrated scaling. The results show that the 1-A SITEX source can be directly scaled to produce 200-keV, 10-A long pulse ion beams with a source power efficiency of less than or equal to 5 kW of total plasma generator power per ampere of D/sup -/ beam generated. Extracted electron-to-D/sup -/ ratios should be less than or equal to 0.06, with all extracted electrons recovered at less than or equal to 10% of the first gap potential energy difference. The close-coupled accelerating structure will be 5 cm long and have five electrodes with 21 slits each, with a 50-kV/cm field in each gap.
Date:
January 1, 1983
Creator:
Dagenhart, W. K.; Gardner, W. L.; Stirling, W. L. & Whealton, J. H.
Object Type:
Article
System:
The UNT Digital Library
Electrode design and performance of the ORNL positive ion sources
The neutral beam development group at ORNL has designed, constructed, and shipped four 50-kV, 100-A sources to PPPL to be used for neutral beam heating of the confined plasma on the PDX tokamak. These sources have higher current capability than scaled-down sources, and they are required to run for 0.5 s as opposed to the 0.3-s requirement for PLT and ISX-B sources. Due to an innovative electrode design, these higher power sources met these requirements and achieved a higher transmission efficiency - 76% of the total input power on target vs 60% for the original ISX-B and modified PLT sources or 40% for the original PLT sources. As a consequence, a power of 2 MW of neutrals to the torus target was achieved; this is a record for measured neutral power and exceeds that of any other power source expected to be used on such advanced tokamaks as TFTR and D-III. A theoretical consideration of the relevant Poisson-Vlasov equations for ions extracted from a plasma was used to optimize the ion optics. Using the same electrode design with a tetraode accelerating structure and a new, indirectly heated cathode, repeatable long pulse, high energy conditions of 70 kV, 7 A, 8 …
Date:
January 1, 1980
Creator:
Whealton, J.H.; Gardner, W.L. & Haselton, H.H.
Object Type:
Article
System:
The UNT Digital Library
Geologic map of the Sulphur Springs Area, Valles Caldera Geothermal System, New Mexico
The geologic and tectonic setting and geology of Sulphur Springs Area are described. Geologic faults, sheared or brecciated rock, volcanic vents, geothermal wells, hydrothermal alteration, springs, thermal springs, fumaroles, and geologic deposits are indicated on the map. (MHR)
Date:
December 1, 1980
Creator:
Goff, F.E. & Gardner, J.N.
Object Type:
Report
System:
The UNT Digital Library
Difficulties with inferring neutron cross sections from charged-particle reactions
We have investigated problems associated with inferring cross sections for neutron reactions on unstable nuclei in the mass-90 region from charged-particle reactions on nearby stable targets. We conclude that effects due to precompound evaporation, isospin, and multiple reaction paths severely limit the circumstances under which charged-particle studies may be directly and easily converted to neutron cross sections of useful accuracy. 4 refs., 2 figs.
Date:
May 7, 1985
Creator:
Gardner, D. G. & Gardner, M. A.
Object Type:
Article
System:
The UNT Digital Library
Continued study of the parameterization of the El gamma-ray strength function
The parameterization of the magnitude and the energy dependence of the E1 gamma-ray strength function for the calculation of neutron- and proton-induced capture cross sections and capture gamma-ray spectra is investigated. The energy-dependent Breit-Wigner (EDBW) is reparameterized incorporating a more general expression for the Breit-Wigner line shape. Evaluation of the reparameterized E1 gamma-ray strength function is discussed. (WHK)
Date:
June 19, 1981
Creator:
Gardner, M. A. & Gardner, D. G.
Object Type:
Article
System:
The UNT Digital Library
Importance of level structure in nuclear reaction cross-section calculations. Revision 1
It is shown that level-density expressions cannot adequately represent or substitute for level structure information when making calculations of the Hauser-Feshbach type for cross sections or isomer-ratios for nuclei in the first few MeV above their ground state. It is stated that such discrete level information should include both experimentally confirmed and theoretically predicted levels. The utility of discrete level information to optimize level density calculations, to compute isomer ratios, in deriving dipole strength functions, and in the analysis of primary gamma ray spectra is emphasized, especially for nuclei far from the line of stability. 29 refs., 12 figs., 6 tabs. (DWL)
Date:
November 7, 1985
Creator:
Gardner, M. A. & Gardner, D. G.
Object Type:
Article
System:
The UNT Digital Library
Preliminary evaluation of neutron capture cross sections for /sup 144/Sm, /sup 145/Sm and /sup 145/Pm
We have made preliminary neutron-capture cross-section calculations of the Hauser-Feshbach type for the isotopes /sup 144/Sm, /sup 145/Sm, and /sup 145/Pm to investigate the production of radioactive /sup 145/Pm by neutron capture on the stable isotope /sup 144/Sm. The calculations were made for incident neutron energies from 2.5 MeV to about 1/sup -4/ or 10/sup -5/ MeV, wherever the first unbound resonance was estimated to occur in each case. At that energy, the calculated value was reduced by a somewhat arbitrary factor, and the excitation function extended down to thermal energy using a (E/sub n/)/sup -1/2/ energy dependence. Since very large uncertainties are associated with the position and magnitude of the first unbound resonance and the subsequent extrapolation back to thermal energy, the cross sections in this low-energy region should not be considered more accurate than +- a factor of 10. For incident neutron energies above each step, the calculations represent an average through the separated and overlapping resonance regions and may be accurate to better than +- a factor of 2. 18 refs., 7 figs., 5 tabs.
Date:
February 13, 1986
Creator:
Gardner, D. G. & Gardner, M. A.
Object Type:
Report
System:
The UNT Digital Library
Initial Assessment of Time of Travel and Mixing through Gulf Island Pond and the Lower Androscoggin River, Maine
From purpose and scope: The purpose of this interim report is to describe the unconventional methods required to analyze time-of-travel data in this reservoir and the regulated section of the Lower Androscoggin River.
Date:
1983
Creator:
Parker, Gene W. & Hunt, Gardner S.
Object Type:
Report
System:
The UNT Digital Library
Engineering Research Division report on reports: calendar year 1979. [LLL]
A bibliography of publications of members of the Engineering Research Division of the Electronics Engineering Department is presented for 1979. Abstracts for 148 publications are included, along with author and keywork indexes. (RWR)
Date:
March 1, 1980
Creator:
Gardner, C.L. & Johnston, S.J. (eds.)
Object Type:
Report
System:
The UNT Digital Library
Calculational tools for the evaluation of nuclear cross-section and spectra data
A technique based on discrete energy levels rather than energy level densities is presented for nuclear reaction calculations. The validity of the technique is demonstrated via theoretical and experimental agreement for cross sections, isomer-ratios and gamma-ray strength functions. 50 refs., 7 figs. (WRF)
Date:
May 7, 1985
Creator:
Gardner, M.A.
Object Type:
Article
System:
The UNT Digital Library
Recent developments in nuclear reaction theories and calculations
A brief review is given of some recent developments in the fields of optical model potentials; level densities; and statistical model, precompound, and direct reaction codes and calculations. Significant developments have occurred in all of these fields since the 1977 Conference on Neutron Cross Sections, which will greatly enhance the ability to calculate high-energy neutron-induced reaction cross sections in the next few years. 11 figures, 3 tables.
Date:
May 5, 1980
Creator:
Gardner, D. G.
Object Type:
Article
System:
The UNT Digital Library
Methods and procedures for evaluation of neutron-induced activation cross sections
One cannot expect measurements alone to supply all of the neutron-induced activation cross-section data required by the fission reactor, fusion reactor, and nuclear weapons development communities, given the wide ranges of incident neutron energies, the great variety of possible reaction types leading to activation, and targets both stable and unstable. Therefore, the evaluator must look to nuclear model calculations and systematics to aid in fulfilling these cross-section data needs. This review presents some of the recent developments and improvements in the prediction of neutron activation cross sections, with specific emphasis on the use of empirical and semiempirical methods. Since such systematics require much less nuclear informaion as input and much less computational time than do the multistep Hauser-Feshbach codes, they can often provide certain cross-section data at a sufficient level of accuracy within a minimum amount of time. The cross-section information that these systematics can and cannot provide and those cases in which they can be used most reliably are discussed.
Date:
September 1, 1981
Creator:
Gardner, M.A.
Object Type:
Article
System:
The UNT Digital Library
Statistical vs valence neutron neutron capture in /sup 98/Mo
It has often been reported that, in mass regions corresponding to peaks in the neutron strength function, nonstatistical mechanisms contribute a significant or even major portion of the average radiation width in the beginning of the resonance region. This could severely limit the possibility of calculating caputure cross sections for targets where experimental data are lacking, because such direct effects are sensitive to the detailed nuclear level structure in the daughter nucleus. The reaction /sup 98/Mo+n was examined for neutrons in the 1 keV to 3 MeV energy range, because this case is often cited as one of the clearest examples of valence neutron capture effects. Preliminary calculations are presented which suggest that these nonstatistical effects rapidly disappear when measurements from even a small number of resonances are averaged.
Date:
June 19, 1981
Creator:
Gardner, D. G.
Object Type:
Article
System:
The UNT Digital Library