The present study of the interstellar formyl ion HCO/sup +/ is the first attempt to investigate dissociative recombination for a triatomic molecular ion using an entirely theoretical approach. We describe a number of fairly extensive electronic structure calculations that were performed to determine the reaction mechanism of the e-HCO/sup +/ process. Similar calculations for the isoelectronic ions HOC/sup +/ and HN/sub 2//sup +/ are in progress. 60 refs.

A direct implicit particle-in-cell (PIC) simulation model with full electromagnetic (EM) effects has been implemented in 2-D Cartesian geometry. The model, implemented with the D/sub 1/ time differencing scheme, was first implemented in a 1-D electrostatic (ES) version to gain some experience with spatial differencing in forms suitable for extension to the full EM field in two dimensions. The implicit EM field solve is considerably different from the implicit ES code. The EM field calculation requires an inductive part as well as the electrostatic and the B field must be self-consistently advanced.

The interaction of energetic electrons with highly charged ions is of great importance to several research fields such as astrophysics, laser fusion and magnetic fusion. In spite of this importance there are almost no measurements of electron interaction cross sections for ions more than a few times ionized. To address this problem an electron beam ion trap (EBIT) is being developed at LLNL. The device is essentially an EBIS except that it is not intended as a source of extracted ions. Instead the (variable energy) electron beam interacting with the confined ions will be used to obtain measurements of ionization cross sections, dielectronic recombination cross sections, radiative recombination cross sections, energy levels and oscillator strengths. Charge-exchange recombinaion cross sections with neutral gasses could also be measured. The goal is to produce and study elements in many different charge states up to He-like xenon and Ne-like uranium. 5 refs., 2 figs.

We have developed a LSI-11/23 computer-driven CAMAC data acquisition system. The 64 silicon-detector system is being used to investigate the alpha and spontaneous fission activities of short-lived transfermium isotopes by the real-time monitoring of the mother-daughter alpha decay sequence. A unique modular pulse processing electronics system was designed to simplify set up and calibration. The computer adjusts the gain of the CAMAC shaping amplifiers enabling the calibration and alignment of all 64 of the 1 k alpha spectra to within 0.5 channel in less than 10 minutes.

Here the authors present a possible way to further increase the energy of SLAC single bunch from 50 GeV to 65 GeV or even more, without increasing the rf peak power and accelerator length.

During 1985, interest has been revived at LLNL in tandem mirrors operating in the negative-potential mode. The negative tandem is formed by combining ECRH-sustained hot electron end cell plasmas with pumping mechanisms to remove trapped ions from the end cells. No sloshing ions are required. The resulting negative potential in the end cells confines the central cell electrons. The requirement of charge neutrality causes the ambipolar potential of the central cell to become negative relative to the end wall (hence, the name ''negative' tandem mirror), thereby providing central cell ion confinement. This potential distribution is the exact inverse of the axial distribution for the conventional (positive) tandem mirror without thermal barriers. In the negative tandem mirror, central cell electrons are confined electrostatically, end cell electrons are confined magnetically, and ions are confined electrostatically everywhere. In this report, we briefly assess the reactor issues pertinent to the operation of the tandem mirror in the negative mode. 7 refs., 5 figs.

A series of viewgraphs is provided that summarize and illustrate some of the physics aspects and design issues of free electron lasers. Physics aspects include the coupling between electrons and light, electron beam properties that affect the free electron laser, and tapering of the wiggler. Design issues include focusing and mismatched electron orbit, as well as diffraction. Modelling of the free electron laser and scaling are also mentioned. (LEW)

The purpose of the ICRH start-up antenna on MFTF-B is to heat the plasma and control the ion distribution as the density increases during start-up. The antenna, consisting of two center fed half turn loops phased 180/sup 0/ apart, has been designed for 1 MW of input power, with a goal of coupling 400 kW into the ions. To vary the heating frequency relative to the local ion cyclotron frequency, the antenna is tunable over a range from 7.5 to 12.5 MHz. The thermal requirements common to low duty cycle ICRH antennas are especially severe for the MFTF-B antenna. The stress requirements are also unique, deriving from the possibility of seismic activity or JxB forces if the magnets unexpectedly quench. Considerable attention has been paid to contact control at high current bolt-up joints, and arranging geometries so as to minimize the possibility of voltage breakdown.

The client submitted 5 sets of porcelain and stoneware subsurface (radioactive site) marker prototypes (31 markers each set). The following were determined: compressive strength, thermal shock resistance, thermal crazing resistance, alkali resistance, color retention, and chemical resistance.

The task force has studied two options for an 8 T ring operating at 2 K. In the first of these the synchrotron light load is taken at 2 K, and in the second it is intercepted on a bore liner at 4.5 K. The possibility of staged construction of the 20 Tev, 8 T, 2 K ring with initial operation at 15 Tev, 6 T and 4.5 K has also been considered. A set of dimensions and specifications has been developed for each of the two 8 T options in the three categories: magnets, cryostat, and refrigeration system with the object of providing for a detailed cost comparison with the 6 T, design D ring. Cost information for refrigeration systems that are not strictly comparable to design D have been developed from component quotations. A very preliminary discussion of costs is included in the report. A summary of the principal findings of the task force is as follows: the temperature at which a 6 T, 4.5 K magnet will operate at 8 T with the same critical current safety margin is found to be 2 K; an increase of 0.5 cm in the magnet inner diameter is found to …

This report is about the Chromatic Correction Scheme for the RHIC3 Lattice. The RHIC3 is the current design for the relativistic heavy ion collider.

For some time now, the sources of RF transverse beam steering in the SLAC Linac have been a mystery. The previously known sources, coupler asymmetries and survey misalignment, have predicted deflections which are frequently much smaller than the observed deflections. A new source of RF steering has been discovered: the tilting of accelerator irises. Measurements of iris tilting in a forty foot accelerator girder are compared with measurements of RF beam deflections and are found to be strongly correlated. 4 refs., 6 figs., 3 tabs.

Pulsed laser annealing and ion beam mixing have been used as surface modification techniques to enhance the physical properties of polycrystalline ..cap alpha..-SiC. Thin Ni overlayers (20 nm to 100 nm) were evaporated onto the SiC surface. The specimens were subsequently irradiated with pulses of a ruby or krypton fluoride (KrF) excimer laser or bombarded with high energy Xe/sup +/ or Si/sup +/ ions. Both processes are nonequilibrium methods and each has been shown to induce unique microstructural changes at the SiC surface which are not attainable by conventional thermal treatments. Under particular (and optimum) processing conditions, these changes considerably increased the mechanical properties of the SiC; following laser irradiation, the fracture strength of the SiC was increased by as much as 50%, but after ion beam mixing, no strength increase was observed. High resolution cross-section transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and Rutherford backscattering techniques were used to characterize the extent of mixing between the Ni and the SiC as a result of the surface modification.