In this paper, the whole-core reactivity consequences of internal fuel motion in three annular fuel designs during a hypothetical 3 dollars/s transient overpower (TOP) accident are compared to determine the effect of geometric design variations. The PINEX-2 and PINEX-3 experiments were performed in the TREAT reactor using annular fuel pins irradiated in GETR. This paper investigates three combinations of solid and annular axial blankets and fission gas plena: top annular blanket and plenum, bottom annular blanket and plenum, and both top and bottom (dual) annular blankets and plena. The dual plena design case showed a significant decrease in internal fuel motion over the single plenum design cases.

Constant extension rate tests have been performed on sensitized Type 316 stainless steel in oxygenated water (8 ppM O/sub 2/) containing chloride ion impurities (0.5 ppM) over a range of strain rates from 10/sup -5/ to 2 x 10/sup -7/ s/sup -1/. The susceptibility to IGSCC (as quantified by parameters such as crack length at failure) increases with a decrease in strain rate. A model consistent with the observed and postulated crack growth behavior and with a fracture criterion is presented and used to derive power laws that relate the IGSCC susceptibility parameters and strain rate. The predicted strain rate exponents are in agreement with the experimental results of this and other studies. The correlations between IGSCC susceptibility and strain rate can be used to predict susceptibility to cracking outside the range of conditions used in the laboratory. In addition, it is shown that the average crack-tip strain rate in CERT experiments can be estimated by use of a J-integral approach. It is observed that the average crack growth rate is proportional to the square root of the estimated average crack-tip strain rate. The experimentally observed correlation is in good agreement with that deduced from a slip-dissolution model proposed by …

X-ray computed tomography (CT) is a widely used method of obtaining cross-sectional views of objects. The high intensity, natural collimation, monochromaticity and energy tunability of synchrotron x-ray sources could potentially be used to provide CT images of improved quality. The advantages of these systems would be that images could be produced more rapidly with better spatial resolution and reduced beam artifacts. In addition, images, in some cases, could be acquired with elemental sensitivity. As a demonstration of the capability of such a system, CT images were obtained of four slices of an excised pig heart in which the arteries and the cardiac chambers were filled with an iodinated medium. Images were taken with incident x-rays tuned successively to energies just above and below the iodine K edge. Iodine specific images were obtained by logarithmically subtracting the low energy image data from the high energy data and then reconstructing the image. CT imaging using synchrotron radiation may become a convenient and non-destructive method of imaging samples difficult to study by other methods.

The dosimetry of A-bomb survivors at Hiroshima and Nagasaki is discussed in light of the new dosimetry developed in 1980 by the author. The important changes resulting from the new dosimetry are the ratios of neutron to gamma doses, particularly at Hiroshima. The implications of these changes in terms of epidemiology and radiation protection standards are discussed. (ACR)

The stellarator configuration can be greatly simplified when toroidal harmonics are introduced. The toroidal function satisfies Laplace's equation and together with toroidal field and vertical field, a small-aspect-ratio stellarator can be constructed with an aspect ratio as low as 3.6. This functional presentation suggests a very fast computation of particle orbits and magnetic configuration.

Gamma scanning measurements revealed that the axial power profile in these test trains was more peaked than expected based on pretest calculations and critical facility measurements. These results implied that the thermal flux incident on the test assembly was greater than expected, which was manifested in highly skewed and extensive fuel melting zones in the outer pin fuel pellets. Observations indicated that the extent of fuel melting near the midplane exceeded 90% of the pellet radius in some of the outer fuel pins toward the end of the overpower transient, with penetration of molten fuel to the cladding inner surface. It is postulated that this extensive fuel melting and penetration combined with bowing-induced high temperature oscillations to produce the initial disruptive failure in an outer pin at the midplane. Subsequent failure events were induced by the inrush of argon fill gas following rupture of the fluted duct tube. Up to one-third of the total fuel inventory was expelled from the test pin bundle into the coolant channels, with substantial upward sweepout of the ejected fuel noted in the post-test examination. The overall nature of the failure event was judged to be relatively nonviolent, based largely on the survival of unclad, …

The proposed Stanford Linear Collider (SLC) has been designed to provide 50 on 50 GeV electron-positron collisions. The performance of the 240 klystrons driving the two-mile long linac must be upgraded to achieve at least 50 Megawatts of peak power output at a pulse of 5 ..mu..sec and a pulse repetition frequency of 180 pulses per second. The operating frequency of the upgraded linac will continue to be 2856 MHz. A klystron amplifier meeting these new requirements has been designed to operate at 315 kV, ..mu..k = 2, with a computed efficiency of slightly greater than 50%. Initial tests indicate the achievement of the basic power objectives; however, observed parasitic instabilities make beam focusing, RF drive frequency and drive level extremely critical. High electric fields in the electron gun, output gap and output window are all potential problems. Steps taken in the design to overcome these problems are discussed and test results are presented.

Beams of monoenergetic positrons with energies of a few eV to many keV have been used in experiments in atomic physics, solid state physics and materials science. The production of positron beams from a new source, an electron linac, is described. Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency, moderator geometry, beam spot size and other positron beam parameters have been determined for electrons with energies from 60 to 120 MeV. Low-energy positron beams produced with a high-energy electron linac can be of much higher intensity than those beams currently derived from radioactive sources. These higher intensity beams will make possible positron experiments previously infeasible.

On-line mathematical models have been used successfully for computer controlled operation of SPEAR and PEP. The same model control concept is being implemented for the operation of the LINAC and for the Damping Ring, which will be part of the Stanford Linear Collider (SLC). The purpose of this paper is to describe the general relationships between models, simulations and the control system for any machine at SLAC. The work we have done on the development of the empirical model for the Damping Ring will be presented as an example.

Core level angle-resolved photoemission intensity oscillates sinusoidally with increasing photoelectron momentum. Interference between direct and scattered photo-emission causes this angle-resolved photoemission extended fine structure (ARPEFS). We will discuss an analytic single-scattering theory which quantitatively describes the oscillations. The procedures for extracting surface geometry information from photoemission measurements will be illustrated with S(1s) ARPEFS from S on Ni(100) and Cu(100) obtained with the soft X-ray double crystal monochromator at the Stanford Synchrotron Radiation Laboratory. Building on the surface sensitivity and chemical selectivity of photoemission, ARPEFS analysis provides direct geometrical information from the oscillation frequencies (derived with auto-regressive Fourier analysis), from intensity changes with polarization and analyzer position, and from analysis of scattering phase-shift zero-crossings.

Complementary broad-band instruments have been developed to measure time dependent, absolute soft x-ray spectra at the Lawrence Livermore National Laboratory (LLNL) Nd glass laser irradiation facilities. Absolute flux measurements of x rays emitted from laser-produced plasmas are important for understanding laser absorption and energy transport. We will describe two new 10-channel XRD systems that have been installed at the LLNL Novette facility for use in the 0.15- to 1.5-keV range. Since XRD channel time response is limited by available oscilloscope performance to 120 ps, a soft x-ray streak camera has been developed for better time resolution (20 ps) and greater dynamic range (approx.10/sup 3/) in the same x-ray energy region. Using suitable filters, grazing incidence mirrors, and a gold or cesium-iodide transmission cathode, this streak camera instrument has been installed at Novette to provide one broad and four relatively narrow channels. It can also be used in a single channel, spatially discriminating mode by means of pinhole imaging. The complementary nature of these instruments has been enhanced by locating them in close proximity and matching their channel energy responses. As an example of the use of these instruments, we present results from Novette 2..omega..(0.53 ..mu..m) gold disk irradiations at 1 …

The first part of this talk is an experimental review of the properties of the THETA meson. Results or upper limits come from radiative j/psi decays and ..gamma gamma.. scattering for the final states eta eta, ..pi pi.., K anti K and rho rho. In the second part, an upper limit is given for the production of low-mass particles in radiative J/psi decays. Constraints for the existence of low-mass gluonic and Higgs mesons are derived.

Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

We are developing a detector capable of measuring the neutron energy spectrum from a laser fusion target containing DT fuel. From such a spectrum the compressed areal density of the DT can be inferred by observing the fraction of 14.1 MeV neutrons down-shifted in energy by elastic scattering. The detector consists of a 0.1 cm thick Ta x-ray and debris shield backed by a 50 to 200 ..mu..m polyethylene radiator followed by layers of CR-39. The energy of each neutron producing a knock-on proton in the radiatior, that in turn creates a damage track in the CR-39, can be derived from the resultant track diameter, location, and orientation. We have analyzed the proton sensitivity and sample readability of 5 types of CR-39 in the energy range 3 to 11 MeV and have found a type fabricated by American Acrylics from a monomer made by a French company, Allymer, to be the most acceptable. Calibration curves were obtained for this plastic at energies of 3 to 15 MeV and dip angles ranging from 75 to 90/sup 0/. These curves were subsequently used to unfold a 14.7 MeV spectrum generated at the Livermore Rotating Target Neutron Source.

A summary is presented of typical gas-phase photoemission studies based on synchrotron radiation in the 50-5000 eV range, using beam lines at the Stanford Synchrotron Radiation Laboratory. Three topics are addressed: atomic inner-shell photoelectron cross sections and asymmetries, correlation peaks in rare gases, and core-level shape resonances in molecules.

A rocket powered by fusion microexplosions is well suited for quick interplanetary travel. Fusion pellets are sequentially injected into a magnetic thrust chamber. There, focused energy from a fusion Driver is used to implode and ignite them. Upon exploding, the plasma debris expands into the surrounding magnetic field and is redirected by it, producing thrust. This paper discusses the desired features and operation of the fusion pellet, its Driver, and magnetic thrust chamber. A rocket design is presented which uses slightly tritium-enriched deuterium as the fusion fuel, a high temperature KrF laser as the Driver, and a thrust chamber consisting of a single superconducting current loop protected from the pellet by a radiation shield. This rocket can be operated with a power-to-mass ratio of 110 W gm/sup -1/, which permits missions ranging from occasional 9 day VIP service to Mars, to routine 1 year, 1500 ton, Plutonian cargo runs.

We have developed a capability for imaging proton sources of moderate energy (6 MeV), with moderate spatial resolution (approx. = 9 ..mu..m), as a diagnostic for laser fusion research. Our technique involves the use of Fresnel zone plate coded imaging coupled with nuclear track detectors (CR-39). We report on a series of test experiments in which a zone plate shadow camera successfully produced images of a proton source distribution. The zone plate shadow patterns were optically reconstructed in higher order producing diffraction-limited point response images with FWHM values of approx. = 9 ..mu..m for a 6 MeV proton source.

Information is presented concerning transients in research reactors and nuclear power plants.

Silicon and germanium semiconductor detectors are widely used as photon and charged-particle spectrometers. Semiconductor detectors combine wide energy bandwidth with good energy resolution to make useful spectrometers for use with the high-intensity x-ray sources available at synchrotron facilities. High-quality silicon and germanium single-crystal starting material is now available for the fabrication of large-volume detectors. Techniques have also been developed to reliably make detectors with passivated surfaces, thin windows and complex geometries. New low-noise preamplifiers and pulse-shaping networks allow higher counting rates and improved pulse throughput. For applications where accurate flux measurements of intense photon beams are required, a semiconductor detector with a current-measuring voltage-to-frequency converter provides a simple system which has excellent linearity and stability. Examples are given where semiconductor detectors have been used in experiments at synchrotron facilities.

RF sources with high peak power output and relatively short pulse lengths will be required for future high gradient e/sup +/e/sup -/ linear colliders. The required peak power and pulse length depend on the operating frequency, energy gradient and geometry of the collider linac structure. The frequency and gradient are in turn constrained by various parameters which depend on the beam-beam collision dynamics, and on the total ac wall-plug power that has been committed to the linac rf system. Various rf sources which might meet these requirements are reviewed. Existing source types (e.g., klystrons, gyrotrons) and sources which show future promise based on experimental prototypes are first considered. Finally, several proposals for high peak power rf sources based on unconventional concepts are discussed. These are an FEL source (two beam accelerator), rf energy storage cavities with switching, and a photocathode device which produces an rf current by direct emission modulation of the cathode.

We will review the performance of the Advanced Test Accelerator, a 50 MeV, 10 KA induction linac. The discussion will cover the operation of the plasma cathode electron source, beam transport throughout the accelerator, and transverse instabilities. Particular emphasis will be placed on the beam breakup instability and on the methods used to minimize it. These include a program of design changes that lead to an order of magnitude reduction in the Q's of the accelerator cavity modes and optimization of the transport tune.

In contrasting the title of this paper with a second paper to be presented at this conference entitled Distributed Digital Control of Accelerators, a potential reader might be led to believe that this paper will focus on systems whose computing intelligence is centered in one or more computers in a centralized location. Instead, this paper will describe the architectural evolution of SLAC's computer based accelerator control systems with respect to the distribution of their intelligence. However, the use of the word centralized in the title is appropriate because these systems are based on the use of centralized large and computationally powerful processors that are typically supported by networks of smaller distributed processors.

Techniques for vectorizing complex logic are shown using a decoupled sliding-surface calculation that is part of a two-dimensional Lagrangian simulation model. The same source coding can be run on many vector, parallel, and multiprocessor computers with very little or no alteration. The vectorizing techniques have been used for a wide range of problems.

In contrast to an rf linac - a constant-current device in which the beam power is increased solely by the addition of kinetic energy, qV, - the induction linac (I.L.) can amplify the beam power at a much more rapid rate. Proper programming of the switching of the modules and the shape of their voltage waveforms, in the early stages of acceleration, can result in a beam current that rises at a rate between V/sup 1/2/ and V and, consequently, a beam power that varies in the range V/sup 3/2/ to V/sup 2/. The current is limited by the transport lens system, which must overcome the beam defocusing force due to space charge.