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The ion-channel laser

Description: A relativistic electron beam propagating through a plasma in the ion-focused regime exhibits an electromagnetic instability at a resonant frequency {omega} {approximately} 2{gamma}{sup 2} {omega}{sub {beta}}. Growth is enhanced by optical guiding in the ion channel, which acts as dielectric waveguide, with fiber parameter V {approximately} 2 (I/I{sub A}){sup 1/2}. A 1-D theory for such an ion-channel laser'' is formulated, scaling laws are derived and numerical examples are given. Possible experimental evidence is noted. 23 refs., 1 fig., 1 tab.
Date: January 1, 1990
Creator: Whittum, D.H.; Sessler, A.M. (Lawrence Berkeley Lab., CA (USA)) & Dawson, J.M. (California Univ., Los Angeles, CA (USA). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Pion correlations in relativistic heavy ion collisions at Heavy Ion Spectrometer Systems (HISS)

Description: This thesis contains the setup, analysis and results of experiment E684H Multi-Pion Correlations in Relativistic Heavy Ion Collisions''. The goals of the original proposal were: (1) To initiate the use of the HISS facility in the study of central Relativistic Heavy Ion Collisions (RHIC). (2) To perform a second generation experiment for the detailed study of the pion source in RHIC. The first generation experiments, implied by the second goal above, refer to pion correlation studies which the Riverside group had performed at the LBL streamer chamber. The major advantage offered by moving the pion correlation studies to HISS is that, being an electronic detector system, as opposed to the Streamer Chamber which is a visual detector, one can greatly increase the statistics for a study of this sort. An additional advantage is that once one has written the necessary detector and physics analysis code to do a particular type of study, the study may be extended to investigate the systematics, with much less effort and in a relatively short time. This paper discusses the Physics motivation for this experiment, the experimental setup and detectors used, the pion correlation analysis, the results, and the conclusions possible future directions for pion studies at HISS. If one is not interested in all the details of the experiment, I believe that by reading the sections on intensity interferometry, the section the fitting of the correlation function and the systematic corrections applied, and the results section, one will get a fairly complete synopsis of the experiment.
Date: May 1, 1990
Creator: Christie, W.B. Jr.
Partner: UNT Libraries Government Documents Department

Stochastic ion heating by lower hybrid turbulence

Description: The motion of an ion in a spectrum of lower hybrid waves propagating across a constant magnetic field is examined. In particular, numerical simulation is used to determine the extent to which a turbulent spectrum of these electrostatic waves may accelerate thermal ions (T < 1 eV). The significance of stochastic web development in this heating process is also discussed. 20 refs., 31 figs.
Date: May 1, 1990
Creator: Candy, J.
Partner: UNT Libraries Government Documents Department

Prospects for research with radioactive beams and targets

Description: Research with heavy ion (HI) beams has become a major field of physics. Nuclei of all naturally occuring elements and isotopes can be accelerated to energies as high as 2 GeV/A with even higher energies expected in the future. With the advent of relativistic heavy ion accelerators and the development of high intensity on-line isotope separators it has now become possible to explore a new dimension in nuclear physics based on the production and application of radioactive ion beams (RIB). More than 1400 unstable nuclei with half lives of more than 1 ..mu..s are known and could potentially serve as projectiles in RIB experiments. The purpose of this paper is firstly to point out that there are now several promising possibilities to obtain RIB's of acceptable intensity and that secondly a large variety of scientific questions can be addressed should such beams become routinely available. The discussion of the production of RIB's is divided into methods where the radioactive species are stopped and reaccelerated, and methods where the RIB emerges as a secondary beam from a suitable nuclear reation. A third section is devoted to the far reaching experimental possibilities related to accumulator and storage rings. The chapters on research will cover the application of RIB's to the synthesis of exotic nuclei, astrophysics, reaction mechanisms, nuclear structure, atomic- and solid-state physics, bio-medicine, and physics related to the special characteristics of storage rings.
Date: June 1, 1984
Creator: Nitschke, J.M.
Partner: UNT Libraries Government Documents Department

Design philosophy for high-resolution rate and throughput spectroscopy systems

Description: The paper describes the philosophy behind the design of a pulse processing system used in a semiconductor detector x-ray spectrometer to be used for plasma diagnostics at the Princeton TFTR facility. This application presents the unusual problems of very high counting rates and a high-energy neutron background while still requiring excellent resolution. To meet these requirements three specific new advances are included in the design: (i) A symmetrical triangular pulse shape is employed in the main pulse-processing channel. A new simple method of generating a close approximation to the symmetrical triangle has been developed. (ii) To cope with the very wide dynamic range of signals while maintaining a constant fast resolving time, approximately symmetical triangular pulse shaping is also used in the fast pulse pile-up inspection channel. (iii) The demand for high throughput has resulted in a re-examination of the operation of pile-up rejectors and pulse stretchers. As a result a technique has been developed that, for a given total pulse shaping time, permits approximately a 40% increase in throughput in the system. Performance results obtained using the new techniques are presented.
Date: May 1, 1982
Creator: Goulding, F.S.; Landis, D.A. & Madden, N.W.
Partner: UNT Libraries Government Documents Department

High-resolution results from the LBL 55-meter SGM (Spherical Grating Monochromator) at SSRL (Stanford Synchrotron Radiation Laboratory) near the K-edge of carbon and nitrogen

Description: The performance of a 55-meter Spherical Grating Monochromator (SGM) is described. A resolution of 60 MeV has been achieved at 400 eV, inferred from the linewidths of the nitrogen 1s-{pi}* resonance. With 0.5 eV resolution, a photon flux of 4 {times} 10{sup 10} photons/sec has been observed at 440 eV. An initial experiment has studied the core-shell resonances of gas-phase ethylene, C{sub 2}H{sub 4}. Vibrational fine structure was resolved both for the carbon 1s-{pi}* and carbon 1s-Rydberg excitations. Comparison with the vibrational frequencies of ground state ethylene implies that the {nu}{sub 1} (C-H stretch) and {nu}{sub 2} (C-C stretch) or {nu}{sub 3} (H-C-H bend) are excited. It is suggested that the lower Rydberg orbitals, 3s and 3p{sigma}, have molecular, anti-bonding character. 13 refs., 6 figs.
Date: July 1, 1989
Creator: Heimann, P.A.; McKinney, W.; Howells, M.; van Zee, R.D.; Medhurst, L.J.; Lauritzen, T. et al.
Partner: UNT Libraries Government Documents Department

Quantum noise in Josephson junctions and squids

Description: A theory for noise in the resistively shunted Josephson junction in the quantum limit is outlined and extended to the dc SQUID. Experimental results for both the single junction and the SQUID are reported.
Date: April 1, 1981
Creator: Koch, R.H.; Van Harlingen, D.J. & Clarke, J.
Partner: UNT Libraries Government Documents Department

Multiple dissociation of /sup 16/O, /sup 14/N, and /sup 12/C at 32. 5 MeV/nucleon

Description: An array of 34 fast/slow plastic scintillators has been used to identify fragments from the breakup of /sup 16/O, /sup 14/N, and /sup 12/C projectiles at 32.5 MeV/nucleon, scattered by a Au target. The dissociation of /sup 16/O into as many as five charged particles has been observed. The yields of the different channels correlate approximately with the threshold energy for separation of the projectile into the observed fragments. The excitation spectrum of the primary projectile fragment was deduced from the measured positions and kinetic energies of the individual fragments. These spectra show that, although most of the decomposition proceeds through excitation energies within /approximately/20 MeV of the lower particle-decay thresholds, excitation energies extending up to /approximately/80 MeV can be produced in the primary stage of the reaction. This represents a significant acquisition of energy by the projectile. Calculations of the yields based on a sequence of binary decays have been presented. Reactions in which one or two units of charge are acquired by the projectile were also observed. 25 refs., 10 figs.
Date: September 1, 1988
Creator: Stokstad, R.G.; Chan, Y.D.; Dacal, A.; DiGregorio, D.E.; Harmon, B.A.; Knop, R. et al.
Partner: UNT Libraries Government Documents Department

Application of Robertson's collective focusing to final focusing

Description: Recently Robertson suggested that a collective focusing scheme might be useful in the final focusing problem for Heavy Ion Fusion. He demonstrates that it is possible to focus a charge and current neutralized beam, and shows this scheme is applicable since HIF scenarios have current requirements smaller than the electron Alfven current. In this note ion emittance is included in the analysis of such lenses. It is found that one can focus an acceptable fraction of the beam, provided the current density is large enough.
Date: September 1, 1982
Creator: Krafft, G.
Partner: UNT Libraries Government Documents Department

First in-beam. gamma. -ray study of sup 67 As

Description: Excited states of the neutron-deficient nucleus {sup 67}As were populated using the {sup 40}Ca({sup 32}S,{alpha}p){sup 67}As and the {sup 40}Ca({sup 33}S,{alpha}pn){sup 67}As reactions at bombarding energies between 95 and 110 MeV. We present a tentative level scheme for {sup 67}As, derived from {gamma}-{gamma} coincidence studies in conjunction with measurement of evaporated charged particles and neutrons.
Date: January 1, 1990
Creator: Lang, T.F.; Moltz, D.M.; Reiff, J.E.; Batchelder, J.C.; Ognibene, T.J.; Cerny, J. et al.
Partner: UNT Libraries Government Documents Department

First-order kinetics-controlled multiple species reactive transport of dissolved organic compounds in groundwater: Development and application of a numerical model

Description: Reactive chemical transport models developed over the past decade have generally relied on the assumption that local thermodynamic equilibrium is achieved at all times between aqueous species in a given system. Consequently, homogeneous aqueous systems characterized by a number of kinetically slow reactions, particularly problems involving organic species, cannot be satisfactorily modeled. In this study, we present a prototype computer model, KINETRAN, which is designed to handle kinetically-controlled homogeneous reactions in the aqueous phase, along with the transport of the various species involved, through geologic media. 31 refs., 53 figs., 10 tabs.
Date: May 1, 1990
Creator: McNab, W.W. Jr.
Partner: UNT Libraries Government Documents Department

Understanding the origin of radon indoors: Building a predictive capability

Description: Indoor radon concentrations one to two orders of magnitude higher than the US average of approx.60 Bq m/sup -3/ (approx.1.5 pCi L/sup -1/) are not uncommon, and concentrations greater than 4000 Bq m/sup -3/ have been observed in houses in areas with no known artificially-enhanced radon sources. In general, source categories for indoor radon are well known: soil, domestic water, building materials, outdoor air, and natural gas. Soil is thought to be a major source of indoor radon, either through molecular diffusion (usually a minor component) or convective flow of soil gas. While soil gas flow into residences has been demonstrated, no detailed understanding of the important factors affecting the source strength of radon from soil has yet emerged. Preliminary work in this area has identified a number of likely issues, including the concentration of radium in the soil, the emanating fraction, soil type, soil moisture content, and other factors that would influence soil permeability and soil gas transport. Because a significant number of dwellings are expected to have indoor radon concentrations above guideline levels, a predictive capability is needed that would help identify geographical areas having the potential for high indoor concentrations. This paper reviews the preliminary work that has been done to identify important soil and building characteristics that influence the migration of radon and outlines the areas of further research necessary for development of a predictive method. 32 refs., 4 figs.
Date: December 1, 1985
Creator: Sextro, R.G.
Partner: UNT Libraries Government Documents Department

PEP liquid level system

Description: A liquid level system has been installed in the accelerator housing of the PEP storage ring. This instrument spans the entire 2.2 km circumference of the PEP project, and over one hundred readouts provide reference elevations which are used for the accurate alignment of accelerator components. The liquid level has proven to be extremely precise (+-0.10 mm) and quick to use, and it has contributed to the accurate alignment of PEP before beam turn-on. Since the liquid level readouts are rigidly attached to the accelerator housing, the liquid level has been a convenient means to monitor the settling of the accelerator housing.
Date: March 1, 1981
Creator: Lauritzen, T. & Sah, R.C.
Partner: UNT Libraries Government Documents Department

Multiple beam induction linac research at LBL

Description: We present results of progress on the LBL multiple beam induction linac experiment (MBE-4). This machine models the accelerator physics of the electric-focused portion of a driver for heavy ion inertial confinement fusion. Four beams of cesium ions are accelerated in common through twenty four induction gaps while being separately focused in individual electrostatic AG focusing channels. Early experiments have demonstrated current amplification in the linac, from 10 mA to 90 mA per beam. This is achieved both by acceleration (from 200 keV to 1 MeV) and by carefully controlled bunch compression. Recent experiments have concentrated on studies of beams extracted from an ion source which produces 5 mA cesium beams at emittances near 0.03 {pi} mm-mrad (normalized). Experiments and theory show a growth of emittance (by about a factor of 2) as these beams are accelerated through the linac. Results of recent measurements of the transverse emittance behavior of these strongly space-charge-dominated ion beams are reviewed and compared with theory. 9 refs., 3 figs.
Date: June 1, 1990
Creator: Garvey, T.; Eylon, S.; Fessenden, T.J.; Hahn, K.; Henestroza, E. & Keefe, D.
Partner: UNT Libraries Government Documents Department

Thermal-gradient migration of brine inclusions in salt crystals. [Synthetic single crystals of NaCl and KCl]

Description: It has been proposed that high-level nuclear waste be disposed in a geologic repository. Natural-salt deposits, which are being considered for this purpose, contain a small volume fraction of water in the form of brine inclusions distributed throughout the salt. Radioactive-decay heating of the nuclear wastes will impose a temperature gradient on the surrounding salt which mobilizes the brine inclusions. Inclusions filled completely with brine migrate up the temperature gradient and eventually accumulate brine near the buried waste forms. The brine may slowly corrode or degrade the waste forms which is undesirable. In this work, thermal gradient migration of both all-liquid and gas-liquid inclusions was experimentally studied in synthetic single crystals of NaCl and KCl using a hot-stage attachment to an optical microscope which was capable of imposing temperature gradients and axial compressive loads on the crystals. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is non-linear.At high axial loads, however, the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. All-liquid inclusions filled with mixed brines were also studied. For gas-liquid inclusions, three different gas phases (helium, air and argon) were compared. Migration studies were also conducted on single crystallites of natural salt as well as in polycrystalline natural salt samples. The behavior of the inclusions at large angle grain boundaries was observed. 35 figures, 3 tables.
Date: September 1, 1982
Creator: Yagnik, S.K.
Partner: UNT Libraries Government Documents Department

Vacuum arc ion charge state distributions

Description: We have measured vacuum arc ion charge state spectra for a wide range of metallic cathode materials. The charge state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. We have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th and U. The arc was operated in a pulsed mode with pulse length 0.25 msec; arc current was 100 A throughout. This array of elements extends and completes previous work by us. In this paper the measured distributions are cataloged and compared with our earlier results and with those of other workers. We also make some observations about the performance of the various elements as suitable vacuum arc cathode materials.
Date: June 1, 1990
Creator: Brown, I.G. & Godechot, X.
Partner: UNT Libraries Government Documents Department

Transverse beam dynamics studies of a heavy ion induction linac

Description: The multiple beam induction linac experiment (MBE-4) was built to study the accelerator physics of the low energy, electrostatically focussed end of a driver for heavy ion inertial confinement fusion. In this machine four beams of Cs{sup +} ions are accelerated through 24 common induction gaps while being focussed in separate AG focussing channels. Each channel consists of a syncopated FODO lattice of 30 periods. We report results of the most recent studies of the transverse beam dynamics of a single drifting (180 keV) beam in this machine. The dependence of the emittance on the zero-current phase advance shows systematic variations which may be understood in the light of previous theoretical work on this topic. This result, unique to the beam parameters of a linac for heavy ion fusion, will be discussed in the context of its implications for a driver design. In addition we will discuss recent measurements of the motion of the beam centroid through the linac. These measurements, coupled with simulations, have proven to be a powerful tool in determining the presence of misalignment errors in the lattice of the accelerator. 6 refs., 3 figs.
Date: August 1, 1990
Creator: Garvey, T.; Eylon, S.; Fessenden, T.J.; Hahn, K.; Henestroza, E. & Keefe, D.
Partner: UNT Libraries Government Documents Department

A database for the Geysers geothermal field

Description: This document contains graphs of data collected from Geysers Geothermal Field. These graphs display data concerning steam rate and cumulative steam from 1968 to 1988. 245 figs. (FSD)
Date: September 1, 1989
Creator: Bodvarsson, G.S.; Cox, B.L.; Fuller, P.; Ripperda, M.; Tulinius, H.; Witherspoon, P.A. et al.
Partner: UNT Libraries Government Documents Department

Metal vapor vacuum arc ion sources

Description: We have developed a family of metal vapor vacuum are (MEVVA) high current metal ion sources. The sources were initially developed for the production of high current beams of metal ions for heavy ion synchrotron injection for basic nuclear physics research; more recently they have also been used for metal ion implantation. A number of different embodiments of the source have been developed for these specific applications. Presently the sources operate in a pulsed mode, with pulse width of order 1 ms and repetition rate up to 100 pps. Beam extraction voltage is up to 100 kV, and since the ions produced in the vacuum arc plasma are in general multiply ionized the ion energy is up to several hundred keV. Beam current is up to several Amperes peak and around 10 mA time averaged delivered onto target. Nearly all of the solid metals of the Periodic Table have been use to produce beam. A number of novel features have been incorporated into the sources, including multiple cathodes and the ability to switch between up to 18 separate cathode materials simply and quickly, and a broad beam source version as well as miniature versions. here we review the source designs and their performance. 45 refs., 7 figs.
Date: June 1, 1990
Creator: Brown, I.G.; Dickinson, M.R.; Galvin, J.E.; Godechot, X. & MacGill, R.A.
Partner: UNT Libraries Government Documents Department

Molecular beam studies of reaction dynamics

Description: Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.
Date: March 1, 1987
Creator: Lee, Y.T.
Partner: UNT Libraries Government Documents Department

Pions from and about heavy ions

Description: A review is presented of the possibilities of pion production with heavy ion reactions. Major headings include: pion thermometry; hills and valleys in pion spectra; pionic orbits of nuclear size; pion confinement in the fireball; anomalons; and Schroedinger equation solutions for pionic atoms. 47 references, 9 figures. (GHT)
Date: September 1, 1982
Creator: Rasmussen, J.O.
Partner: UNT Libraries Government Documents Department

Design analysis and performance evaluation of a two-dimensional camera for accelerated positron-emitter beam injection by computer simulation

Description: The characteristics and design of a high-accuracy and high-sensitivity 2-dimensional camera for the measurement of the end-point of the trajectory of accelerated heavy ion beams of positron emitter isotopes are described. Computer simulation methods have been used in order to insure that the design would meet the demanding criteria of ability to obtain the location of the centroid of a point source in the X-Y plane with errors smaller than 1 mm, with an activity of 100 nanoCi, in a counting time of 5 sec or less. A computer program which can be developed into a general purpose analysis tool for a large number of positron emitter camera configurations is described in its essential parts. The validation of basic simulation results with simple measurements is reported, and the use of the program to generate simulated images which include important second order effects due to detector material, geometry, septa, etc. is demonstrated. Comparison between simulated images and initial results with the completed instrument shows that the desired specifications have been met.
Date: May 1, 1982
Creator: Llacer, J.; Chatterjee, A.; Batho, E.K. & Poskanzer, J.A.
Partner: UNT Libraries Government Documents Department

Thermochemical data for nuclear waste disposal

Description: Thermochemical data for nuclear waste disposal are compiled. The resulting data base consists of enthalpy, entropy and heat capacity of formation, and Debye-Huckel coefficients of selected substances for about 25 elements. Values of the data are combined with intrinsic equilibrium constants at 25/sup 0/C and zero ionic strength to calculate equilibrium quotients to 350/sup 0/C and 3 ionic strength. PuSO/sub 4//sup 2 +/, UOH/sup 3 +/ and UO/sub 2/CO/sub 3/(aq) are given as examples.
Date: May 1, 1984
Creator: Phillips, S.L.
Partner: UNT Libraries Government Documents Department