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)

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.

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.

The design of a cryogenic helium pump for circulating liquid helium in a magnet and the design of a test loop for measuring the pump performance in terms of mass flow vs pump head at various pump speeds are described. A commercial cryogenic helium pump was tested successfully. Despite flaws in the demountable connections, the piston pump itself has performed satisfactorily. A helium pump of this type is suitable for the use of flowing supercritical helium through Internally Cooled Superconductor (ICS) magnets. It has pumped supercritical helium up to 7.5 atm with a pump head up to 2.8 atm. The maximum mass flow rate obtained was about 16 g/s. Performance of the pump was degraded at lower pumping speeds. (LCL)

Three experiments are described in which H/sup -/ or D/sup -/ ions have been produced by backscattering from surfaces coated with alkali metals: (1) Backscattering of H/sup -/ and D/sup -/ produced by 0.15- to 4-keV/nucleus H/sub 2//sup +/, H/sub 3//sup +/, D/sub 2//sup +/, and D/sub 3//sup +/ bombarding clean targets of Cs, Rb, K, Na, and Li. For each target, the H/sup -/ and D/sup -/ yields were maximized at incident energies between 300 and 1200 eV/nucleus and always at a lower incident energy for H than for D on a given target. At any given incident energy, both the H/sup -/ and D/sup -/ yields decreased in going from Cs to Li in the order given above. (2) A Mo surface was bombarded by a low-energy flux of H atoms produced in a tungsten furnace. As the surface work function was reduced by evaporating Cs onto the target, a small fraction (10/sup -9/) of the incident hydrogen atoms was observed as backscattered H/sup -/ ions. (3) Surfaces of Mo, W, Pt, Ni, Cu, Re, Ta, and Pd were bombarded by hydrogen ions produced in a discharge. Two classes of H/sup -/ ions were observed when Cs was …

The hot dry rock (HDR) site selection and resource evaluation team has been assessing roughly 24 sites within the USA as candidates for development of a second HDR geothermal system. Potential sites examined fall broadly into three categories according to the nature of their thermal anomalies: (1) Quaternary magmahydrothermal (volcanic or igneous) systems such as The Geysers-Clear Lake region, California; (2) regional thermal anomalies of tectonic origin such as the Basin and Range Province of the Southwest; and (3) pre-Quaternary plutonic and metamorphic complexes such as the Conway Granite, New Hampshire. Although sites with both electrical generation and direct use potential have been considered, efforts were concentrated on electrical sites. Criteria for a successful HDR electrical generation site utilizing current technology require temperatures greater than or equal to 200/sup 0/C, depths less than or equal to 5/km, and impermeable reservoir rocks. Sites with these characteristics only exist in the western USA. The significance of other criteria such as environmental issues, water rights, public visability, and pre-existing power networks have not yet been evaluated.

The ISABELLE proton accelerator uses over one thousand superconducting magnets to guide the particle beams in two circular rings, 3.8 km in circumference. Prior to their installation in the tunnel all magnets must be tested and measured at their 3.8 K operating temperature. This paper describes the refrigeration system, called MAGCOOL, to accomplish this task.

The facilities used by the Los Alamos Explosives Technology group to study the shock-induced decomposition of high explosives are described.

Neutral beams for magnetic fusion reactors are at an early stage of development, and require considerable effort to make them into the large, reliable, and efficient systems needed for future power plants. To optimize their performance to establish specific goals for component development, systematic analysis of the beamlines is essential. Three ion source characteristics are discussed: arc-cathode life, gas efficiency, and beam divergence, and their significance in a high-energy neutral-beam system is evaluated.

Described are cytological techniques to differentiate malignant and normal cells in culture. Emphasis is placed upon cell function and gene expression for determinative procedures. (DLS)

An indirect method of laser-based equation of state studies, which utilizes shock waves generated by laser-accelerated projectiles rather than ablation shocks from direct laser irradiation of the sample under investigation, is proposed and examined theoretically. We derive simple formulas for the minimum thickness and maximum speed of laser-accelerated disks, comparing them with results of Nd-laser experiments conducted by the Naval Research Laboratory. Our calculations indicate that disks can be accelerated to velocities above 10/sup 7/ cm/s using a wide choice of laser parameters (pulse duration, energy, intensity, wavelength, etc.). The use of shorter wavelengths, e.g., a KrF(0.25 ..mu..m) laser rather than Nd (1.06 ..mu..m), allows thicker disks to be accelerated and faster velocities to be attained, approximately in the ratio (lambda/sub L/(Nd)/lambda/sub L/(KrF))/sup 1/3/ approx. = 1.6. One-dimensional Lasnex computer calculations indicate that the laser-accelerated disk constitutes a useful flyer plate even while disassembling under the force of the laser ablation shock. The calculations predict that the shockwave the projectile disk generates in a second (impact) disk located a suitable distance away has a greater amplitude than the laser shock and is considerably more steady, exhibiting little decay in propagating through the second disk.

In order to anticipate problems from the radioactivation of neutral beam sources as a result of testing, a code has been developed which calculates both the radioactivities produced and the dose rates resulting therefrom. The code ACDOS2 requires neutron source strength and spectral distribution as input, or alternately, the source strength can be calculated internally from an input of neutral beam source parameters. A variety of simple geometries can be specified, and up to 12 times of interest following the shutdown of the neutron source. Radiation attenuating and daughter radioactivities are treated accurately. ACDOS2 is also of use for neutron-induced radioactivation problems involving accelerators, fusion reactors, or fission reactors.

We review recent laser-driven shock wave experiments, with a view toward assessing the prospects of making accurate physical properties measurements at ultrahigh pressures. Recent experimental results on the scaling of shock pressure with laser intensity and wavelength are presented, and preliminary impedance matching experiments are discussed.

The relativistic random-phase approximation (RRPA) is introduced to account for electron-electron correlation in atoms and ions of high nuclear charge where non-relativistic many-body methods are inadequate. To provide a basis for this study of the RRPA, the Dirac-Fock (DF) theory is reviewed. Applications of the DF equations to determine inner-electron binding energies in heavy atoms are given illustrating the influence of relativistic effects in situations where correlations are unimportant. The RRPA equations are derived as natural generalizations of the DF equations. Examples of RRPA calculations of discrete excitations and of photoionization are given illustrating situations where both relativistic and correlation effects play important roles.

An overall injector system description is presented first, and this will be followed by a detailed discussion of those problems unique to multiple injector operation on the tokamaks, i.e., power transmission, conditioning, reliability, and failures.

Violent collision of two independent many-particle systems, victims, are discussed in the atomic sphere. The asymmetric region where the charge of the projectile Z/sub p/ is less than the target nuclear charge Z/sub n/ is now well understood though interesting details still need to be worked out. Negatively charged projectiles offer a new illustration of Fadeev re-arrangement collisions. Multi-electron coherence effects illustrate the richness of the field but a symmetric (Z/sub p/ approx. Z/sub n/) collision treatment is needed. A new one and a half center expansion method promises a solution to this problem. Future areas of interest are discussed.

Samples of fine-grained sandstone from the Colorado Interstate Gas Exploration (CIGE), Natural Buttes No. 21 core, Uinta Basin, Utah were studied using pulsed nuclear magnetic resonance (NMR) and standard mineralogical techniques. Brine-saturated rock porosities varied from 1 to 13% and were found deducible from the magnitude of the proton NMR. The complex pore geometry and presence of authigenic carbonate and clay minerals in these samples precluded the use of standard flow models for predicting brine permeabilities from T/sub 1/ decays. A network model of the pore system is proposed and shown capable of accurately reproducing measured rock permeabilities, which varied from 10/sup -4/ to 1 millidarcy.

The workshop emphasis was to acquaint the atomic physics community with the range of experimental capabilities of the NSLS. (GHT)

The effects of stored energy in the system capacitance across the accelerator grids during high voltage vacuum breakdown are examined. Measurements were made of the current flow and the energy deposition on the grids during breakdown. It is shown that only a portion (less than or equal to 40 J) of the total stored energy (congruent to 100 J) is actually dissipated on the grids. Most of the energy is released during the formation phase of the vacuum arc and is deposited primarily on the most positive grid. Certain abnormal situations led to energy depositions of about 200 J on the grid, but the ion accelerator endured them without exhibiting any deterioration in performance.

Rectangular plasma generators are being developed with the capability of producing hydrogen ion beams of 60 to 100 A. Using single and double electron feed configurations of the duoPIGatron type, these generators have been operated at arc levels of 1200 A for pulse lengths of > 30 s. The plasma density and uniformity are sufficient for extracting approx. 60-A hydrogen ions using a 13 x 43 cm accelerator and approx. 100 A with an 18 x 48 cm accelerator.

The use of empirical pseudopotentials, in evaluating interatomic potentials, provides an inexpensive and convenient method for obtaining highly accurate potential curves and permits the modeling of core-valence correlation, and the inclusion of relativistic effects when these are significant. Recent calculations of the X/sup 1/..sigma../sup +/ and a/sup 3/..sigma../sup +/ states of LiH, NaH, KH, RbH, and CsH and the X/sup 2/..sigma../sup +/ states of their anions are discussed. Pseudopotentials, including core polarization terms, have been used to replace the core electrons, and this has been coupled with the development of compact, higly-optimized basis sets for the corresponding one- and two-electron atoms. Comparisons of the neutral potential curves with experiment and other ab initio calculations show good agreement (within 1000 cm/sup -1/ over most of the potential curves) with the difference curves being considerably more accurate. In the method of computer molecular dynamics, the force acting on each particle is the resultant of all interactions with other atoms in the neighborhood and is obtained as the derivative of an effective many-body potential. Exploiting the pseudopotential approach, in obtaining the appropriate potentials may be very fruitful in the future. In the molecular dynamics example considered here, the conventional sum-of-pairwise-interatomic-potentials (SPP) approximation is …

Experimental measurements of cross sections for collisions of multiply charged ions with atoms at the lowest attainable collision energies are reported. Emphasis is on electron capture from hydrogen atoms by multiply charged ions at energies below 1 keV/amu. The principal effort is the development of a merged-ion-atom-beams apparatus for studies down to 1 eV/amu relative energy. (GHT)

The present status of the technology of positive-ion-based neutral injectors is examined with particular reference to the Oak Ridge National Laboratory neutral beam development program. It is shown that the development and application of multi-megawatt neutral beams have been quite successful. Injector parameters that have been utilized and those that are planned to be utilized in various confinement devices are examined. Development needs for the upcoming applications are shown to be primarily in the area of extending the beam pulse length to several seconds. The accomplishment of this goal will be a major step towards realizing a reactor-grade injector if the beam energy requirement for such an application is about 150 keV or less.

The conference is an attempt to gather state-of-the-art information to understand the theory of relativistic atomic structure beyond the framework of the original Dirac theory. Abstracts of twenty articles from the conference were prepared separately for the data base. (GHT)