p-Process modeling of some rare but stable proton-rich nuclei requires knowledge of a variety of neutron, charged particle, and photonuclear reaction rates at temperatures of 2 to 3 {times} 10{sup 9} {degrees}K. Detailed balance is usually invoked to obtain the stellar photonuclear rates, in spite of a number of well-known constraints. In this work we attempt to calculate directly the stellar rates for ({gamma},n) and ({gamma},{alpha}) reactions on {sup 151}Eu. These are compared with stellar rates obtained from detailed balance, using the same input parameters for the stellar (n,{gamma}) and ({alpha},{gamma}) reactions on {sup 150}Eu and {sup 147}Pm, respectively. The two methods yielded somewhat different results, which will be discussed along with some sensitivity studies. 16 refs., 7 figs.

We report measurements of the time response of fast-gated, micro- channel plate (MCP) detectors, using a <10 ps pulsewidth ultra-violet laser and an electronic sampling system to measure time resolutions to better than 25 ps. The results show that framing times of less than 100 ps are attainable with high gain. The data is compared to a Monte Carlo calculation, which shows good agreement. We also measured the relative sensitivity as a function of DC bias, and saturation effects for large signal inputs. In part B, we briefly describe an electrical time-of-flight'' technique, which we have used to measure the response time of a fast-gated microchannel plate (MCP). Thinner MCP's than previously used have been tested, and, as expected, show fast gating times and smaller electron multiplication. A preliminary design for an x-ray pinhole camera, using a thin MCP, is presented. 7 refs., 6 figs.

Path planning among movable obstacles is a practical problem that is in need of a solution. In this paper an efficient heuristic algorithm that uses a generate-and-test paradigm: a good'' candidate path is hypothesized by a global planner and subsequently verified by a local planner. In the process of formalizing the problem, we also present a technique for modeling object interactions through contact. Our algorithm has been tested on a variety of examples, and was able to generate solutions within 10 seconds. 5 figs., 27 refs.

We are closing chapter one'' of the nuclear age. Whatever happens to the Soviet Union and to Europe, some of the major determinants of nuclear policy will not be what they have been for the last forty-five years. Part of the task for US nuclear weapons policy is to adapt its nuclear forces and the oganizations managing them to the present, highly uncertain, but not urgently competitive situation between the US and the Soviet Union. Containment is no longer the appropriate watchword. Stabilization in the face of uncertainty, a more complicated and politically less readily communicable goal, may come closer. A second and more difficult part of the task is to deal with what may be the greatest potential source of danger to come out of the end of the cold war: the breakup of some of the cooperative institutions that managed the nuclear threat and were created by the cold war. These cooperative institutions, principally the North Atlantic Treaty Organization (NATO), the Warsaw Pact, the US-Japan alliance, were not created specifically to manage the nuclear threat, but manage it they did. A third task for nuclear weapons policy is that of dealing with nuclear proliferation under modern conditions when …

Unlike a genetic map which provides information on the relative position of genes or markers based upon the frequency of genetic recombination, a physical map provides a topographical picture of DNA, i.e. distances in base pairs between landmarks. The landmarks may be genes, gene markers, anonymous sequences, or cloned DNA fragments. Perhaps the most useful type of physical map is one that consists of an overlapping set of cloned DNA fragments (contigs) that span the chromosome. Once genes are assigned to this contig map, sequencing of the genomic DNA can be prioritized to complete the most interesting regions first. While, in practice, complete coverage of a complex genome in recombinant clones may not be possible to achieve, many gaps in a clone map may be closed by using multiple cloning vectors or uncloned large DNA fragments such as those separated by electrophoretic methods. Human chromosome 19 contains about 60 million base pairs of DNA and represents about 2% of the haploid genome. Our initial interest in chromosome 19 originated from the presence of three DNA repair genes which we localized to a region of this chromosome. Our approach to constructing a physical map of human chromosome 19 involves four steps: …

In order to understand the coupling of a charged particle beam to modes in induction cells with gap width -- to -- beampipe radius ratio w/b > 1, the variation of the transverse Z/Q for both axially symmetric and axially asymmetric dipole modes in this regime is investigated. It is found that the gross behavior of the axially symmetric modes when w/b > 1 is at least consistent with the approximate analysis of Briggs, although a thorough comparison has not been undertaken. The axially asymmetric modes are found to be unimportant until w/b approaches 2, and they generally exhibit lower values of Z{perpendicular}/Q than the axially symmetric modes.

Experimental work is being performed by collaborators at LLNL, SLAC, and LBL to investigate relativistic klystrons as a possible rf power source for future high-gradient accelerators. We have learned how to overcome or previously reported problem of high power rf pulse shortening and have achieved peak rf power levels of 330 MW using an 11.4-GHz high-gain tube with multiple output structures. In these experiments the rf pulse is of the same duration as the beam current pulse. In addition, experiments have been performed on two short sections of a high-gradient accelerator using the rf power from a relativistic klystron. An average accelerating gradient of 84 MV/m has been achieved with 80-MW of rf power.

High gain Inertial Confinement Fusion (ICF) targets require a highly uniform drive. In the case of direct drive, the inherent non-uniformities in a high-power glass laser beam are large enough to prevent high compression of targets. In recent years two methods for smoothing the laser drive, Induced Spatial Incoherence (ISI) and Smoothing by Spectral Dispersion (SSD), have been proposed. Both methods break the original laser beam up into many beamlets that then interfere at the target to produce an illumination pattern with large instantaneous intensity variations over a wide range of spatial scales. This interferences pattern dances around at the coherence time of the laser and averages out to produce a smooth beam on longer time scales. Indirect drive schemes shine the laser on high-Z material, usually gold, which converts the laser energy into x-rays. The x-rays are then used to drive the target. Non-uniformities in the laser beam can imprint themselves on the emitted x-rays and potentially cause problems, although the spatial transport of the x-rays to the target tends to smooth out these non-uniformities. As a result, ISI and SSD schemes are also being considered for indirect drive laser systems. We address this problem by modeling the effects …

The light and velocity variations of the Sun and solar-like stars are unique among intrinsic variable stars. Unlike all other standard classes, such as Cepheids, B stars, and white dwarfs, the pulsation driving is caused by coupling with the acoustic noise in the upper convection zone. Each global pulsation mode is just another degree of freedom for the turbulent convection, and energy is shared equally between these g{sup {minus}}-modes and the solar oscillation modes. This driving and damping, together with the normal stellar pulsation mechanisms produce extremely low amplitude solar oscillations. Actually, the surface layer radiative damping is strong, and the varying oscillation mode amplitudes manifest the stochastic convection driving and the steady damping. Thus stability calculations for solar-like pulsations are difficult and mostly inconclusive, but calculations of pulsation periods are as straightforward as for all the other classes of intrinsic variable stars. The issue that is important for the Sun is its internal structure, because the mass, radius, and luminosity are extremely well known. Conventionally, we need the pulsation constants for each of millions of modes. Unknown parameters for constructing solar models are the composition and its material pressure, energy, and opacity, as well as the convection mixing length. …

Recent studies concerning optimization parameters for e{sup +}e{sup {minus}} super linear colliders use multiple particle bunches for each rf pulse to increase the luminosity and overall efficiency. Requirements for final focusing of the beams severely restrict the bunch to bunch energy variation during the rf pulse. To accurately determine the accelerating fields and energy variation, the dispersion related transient behavior of the rf drive pulse must be considered. A numerical study of dispersion effects on several different accelerating structures is presented.

A linear, frequency independent model of the rf properties of unbiased, soft ferrite has been implemented in finite-difference, time-domain, electromagnetic simulation code AMOS for the purposes of studying linac induction cavities. The simple model consists of adding a magnetic conductivity term ({sigma}{sub m}H) to Faraday's Law. The value of {sigma}{sub m} that is appropriate for a given ferrite at a particular frequency is obtained via an rf reflection experiment on a very thin ferrite toroid in a shorted coaxial line. It was found that in the frequency range 100 to 1000 MHz, the required value of {sigma}{sub m} varies only slightly (<10%), and so we approximated it as a frequency independent parameter in AMOS. A description of the experimental setup and the technique used to extract the complex {mu} from the measurements is described. The model has been used to study the impedances of the DARHT induction cavity, and comparisons between these experimental measurements and AMOS calculations is presented. Implementation of a frequency dependent version of this model in AMOS is being pursued, and a discussion of this effort is given.

A series of pressurization tests of a 3.5-km deep body of jointed crystalline rock has shown that both the pressure deformation (i.e., dilation) of the region and the boundary permeation are nonlinear functions of the effective stress. This is because the apertures for both the joints and microcracks are strong functions of the effective normal stress acting to close them. For a surface pressure increase from zero to 7.5 MPa, the fluid storage in the natural joints and microcracks in this 0.3 km{sup 3} volume of rock increased by 1470 m{sup 3}. The corresponding increase in fluid storage between 7.5 and 15 MPa was 1090 m{sup 3}. However, even at a surface pressure level of 15 MPa, the permeation loss rate from this large volume of rock is only 0.3 l/s after six months of pressure maintenance. Using transient nonlinear numerical modeling, it is shown that the pressure-dependent fracture permeability model of Gangi, and the fracture porosity equivalent, adequately represent the measured permeability and porosity data obtained to date from this continuing series of pressurization experiments.

The combustion of chloroethane is modeled as a stirred reactor so that we can study critical emission characteristics of the reactor as a function of residence time. We examine important operating conditions such as pressure, temperature, and equivalence ratio and their influence on destructive efficiency of chloroethane. The model uses a detailed chemical kinetic mechanism that we have developed previously for C{sub 3} hydrocarbons. We have added to this mechanism the chemical kinetic mechanism for C{sub 2} chlorinated hydrocarbons developed by Senkan and coworkers. In the modeling calculations, sensitivity coefficients are determined to find which reaction-rate constants have the largest effect on destructive efficiency. 24 refs., 6 figs., 1 tab.

The development of Inertial Confinement Fusion (ICF) as a power source will require demonstrating four principal objectives: ignition and propagating burn, adequate gain ({eta}G {approx gt} 10) at low drive energy for the reactor driver, reactor pulse rates of a few Hz, and the long-term reliability and economics of a reactor. Additionally, the potential value and applicability of special-purpose ICF reactors, such as tritium breeding reactors and reactors for burning high level fission waste (actinide and fission products) should be investigated. To keep development time and costs to a minimum these should be accomplished with as few major facilities as possible, and subsystems should be developed only as they are needed. A viable scenario for Inertial Fusion Energy (IFE) would include establishing the first milestone in the National Academy of Sciences (NAS) and Fusion Policy Advisory Committee (FPAC) recommended Nova Upgrade, and the latter three in an Engineering Test Facility (ETF)/Demonstration Power Plant (DPP), i.e. two major facilities. To be successful in so short a time, operations at the major facilities would have to be supported by off-line reactor driver and other technology development. The program plan discussed here assumes that enhanced funding is available beginning in FY 1992. It …

We have identified the Motorola 2N4014 and 2N5551 and the Raytheon RS3944 as three transistor types that exhibit avalanche characteristics and have long term collector breakdown voltage stability superior to other transistors tested. Stability on all types has been improved by power burnin. An automatic avalanche transistor burnin tester has been constructed to allow power burnin of up to 1008 transistors at a time. The tester is controlled by an IBM Personal Computer (PC) and can be programmed to acquire data, unattended, at any desired rate or period. Data are collected from each run and stored on a floppy disk in ASCII format. The data analysis software, RS/1, was used for analysis and display. Data runs were typically 3 to 4 months long, with readings taken weekly. The transistors were biased into the avalanche or Zener region by individual current sources set to about 20% of the self-avalanche current for each type of transistor. Motorola, Zetex and National transistors were operated at 100 microamperes ({mu}A), and the Raytheon units were operated at 20 {mu}A. The electric field causes migration of material in the high field region at the surface near the collector-base junction, creating the voltage instability. 7 refs., 9 …

A KMS laser experiment collides Aluminum (A1) and Magnesium (Mg) plasmas. The measurements include electron density, time and space resolved Ly-alpha and He-alpha lines of Al and Mg, and x-ray images. These measurements were analyzed with a hydrodynamic code, LASNEX, and a special two-fluid code OFIS. The results strongly suggest that at early times, the Al interpenetrates the counterstreaming Mg and deposits in the dense Mg region. At late times, the Al plasma stagnates against the Mg plasma.

Photocopy of the front cover of a magazine and an article titled Money for the Asking, which details that teachers have to make do with what they have, but education funds are trying to change that, funneling money and expertise into the schools that need the support the most.