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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

The renormalized theory of beam-beam interaction

Description: A new approach to calculate analytically the particle distribution in the presence of beam-beam interaction and synchrotron radiation effects for an electron-positron colliding beam storage ring is presented. The method is based on correct calculation of the Green's function which includes the full effect of the beam-beam force on the distortion of particle orbits, borrowing the renormalization technique of quantum field therory. By this way, the theory is applicable to any level of beam-beam interaction, no matter whether chaos ensues in phase space or not. This paper is devoted mostly to verificaiton of the theory by comparison with the results of computer simulations. Fairly good agreements are obtained. 5 refs., 3 figs.
Date: June 1, 1988
Creator: Chin, Yong Ho
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

Status of the MEVVA (Metal Vapor Vacuum Arc) high current metal ion source. [Metal Vapor Vacuum Arc]

Description: The MEVVA (Metal Vapor Vacuum Arc) ion source that has been developed at LBL was reported on for the first time at the 1985 Particle Accelerator Conference (1). This source can produce hundreds of milliamperes of beam current of metal species from lithium up to uranium. In the period since then we have developed the source further, and this work is summarized here. We have now run the source with over 30 different beam species, and with an extraction voltage up to 110 kV. We have made and operated a miniature source, the MicroMEVVA. A multi-cathode version, in which one can switch rapidly between cathodes of different materials, has recently been constructed and tested. Applications of the source include: as a synchrotron ion source, as an ion source for heavy ion fusion, and for metallurgical ion implantation; we have done some preliminary work in these directions.
Date: March 1, 1987
Creator: Brown, I.G.; Galvin, J.E.; MacGill, R.A. & Wright, R.T.
Partner: UNT Libraries Government Documents Department

Nuclear science. Annual report, July 1, 1980-June 30, 1981

Description: This annual report describes the scientific research carried out within the Nuclear Science Division between July 1, 1980 and June 30, 1981. The principal activity of the division continues to be the experimental and theoretical investigation of the interaction of heavy ions with target nuclei. Complementary research programs in light-ion nuclear science, in nuclear data evaluations, and in the development of advanced instrumentation are also carried out.
Date: June 1, 1982
Creator: Friedlander, E.M. (ed.)
Partner: UNT Libraries Government Documents Department

Nuclear-deformation energies according to a liquid-drop model with a sharp surface

Description: We present an atlas of 665 deformation-energy maps and 150 maps of other properties of interest, relevant for nuclear systems idealized as uniformly charged drops endowed with a surface tension. The nuclear shapes are parametrized in terms of two spheres modified by a smoothly fitted quadratic surface of revolution and are specified by three variables: asymmetry, sphere separation, and a neck variable (that goes over into a fragment-deformation variable after scission). The maps and related tables should be useful for the study of macroscopic aspects of nuclear fission and of collisions between any two nuclei in the periodic table.
Date: May 1, 1982
Creator: Blocki, J. & Swiatecki, W.J.
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

Nuclear dissipation and the order to chaos transition

Description: The transition from ordered to chaotic nucleonic motions in the nuclear mean-field potential is reflected in the disappearance of shell effects in nuclear masses and deformations, and in the transition from an elastic, through an elastoplastic, to a dissipative behavior of the nucleus. 23 refs., 10 figs.
Date: June 1, 1988
Creator: Swiatecki, W.J.
Partner: UNT Libraries Government Documents Department

Ramp rate sensitivities of several superconducting dipole magnets operated in He I and superfluid He II

Description: The quench current of a superconducting dipole magnet decreases from its slow-ramp value as the current ramp-rate is increased, due to heat buildup in the coil winding. This ramp-rate dependence has been measured for several superconducting dipoles in both normal He I and in superfluid He II. The heat generated by charging fields has been measured for severall magnets in He II, where particularly sensitive and accurate measurements can be made of any heat input to the essentially isothermal helium bath by its temperature rise. Previously measured values of heat transfer are applied to the data from one magnet to explain its observed behavior. The conclusion is drawn that at a given cycle rate, a superfluid He II-cooled superconducting accelerator can operate closer to the short-sample limit of the magnet's superconductor than can a corresponding He I-cooled machine.
Date: November 1, 1982
Creator: Caspi, S.; Gilbert, W.S. & Rechen, J.B.
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

Resonance formation in photon-photon collisions

Description: Recent experimental progress on resonance formation in photon-photon collisions is reviewed with particular emphasis on the pseudoscalar and tensor nonents and on the ..gamma gamma..* production of spin-one resonances. 37 refs., 17 figs., 5 tabs.
Date: August 1, 1988
Creator: Gidal, G.
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

Hydrogen and deuterium NMR of solids by magic-angle spinning

Description: The nuclear magnetic resonance of solids has long been characterized by very large specral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, ..beta../sub m/ = Arccos (3/sup -1/2/), with respect to the direction of the external magnetic field. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of ..beta... A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H/sub D/ was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal motion. In the general case of large H/sub D/, isotropic spectra were obtained by dilution of /sup 1/H with /sup 2/H combined with magic angle rotation. The resolution obtained represents the practical limit for proton NMR of solids.
Date: October 1, 1982
Creator: Eckman, R.R.
Partner: UNT Libraries Government Documents Department

Evaluation of indoor aerosol control devices and their effects on radon progeny concentrations

Description: Eleven portable air cleaning devices have been evaluated for control of indoor concentrations of respirable particles, and their concomitant effects on radon progeny concentrations have been investigated. Of the devices we examined the electrostatic precipitators and extended surface filters had significant particle removal rates, while the particle removal rates for several small panel-filters, an ion-generator, and a pair of mixing fans were found to be negligible. The evaluation of radon progeny control produced similar results; the air cleaners which were effective in removing particles were also effective in reducing radon progeny concentrations. Furthermore, at the low particle concentrations, plateout of the unattached radon progeny was found to be a significant removal mechanism. The overall removal rates due to deposition of attached and unattached progeny have been estimated from these data, and the equilibrium factors for total and unattached progeny concentrations have been calculated as a function of particle concentration. 7 references, 2 figures.
Date: February 1, 1984
Creator: Sextro, R.G.; Offermann, F.J.; Nazaroff, W.W.; Nero, A.V.; Revzan, K.L. & Yater, J.
Partner: UNT Libraries Government Documents Department

Heat transfer through He II in a 9. 6 m long 35 mm ID tube

Description: The limiting heat flux at the onset of He I was measured in a 9.6 m long tube of 35 mm ID at a bath temperature between 1.8 K and T/sub lambda/ and a pressure of 1 atm. The measured limiting heat flux during axial heating is 50% more than end heating at the same bath temperature. Both cases agrees with the Gorter-Mellink mutual friction theory.
Date: July 1, 1984
Creator: Caspi, S. & Schafer, R.V.
Partner: UNT Libraries Government Documents Department

Cost of high-field Nb/sub 3/Sn and NbTi accelerator dipole magnets

Description: Future high-energy proton accelerators will likely require very high magnetic fields if the size of the accelerator and associated experimental areas are to be limited to dimensions that can be accomodated by the terrain at convenient sites. Two commercially available superconductors can be used to produce magnetic fields of 10T or more. The first is Nb/sub 3/Sn, which can operate in pool boiling helium at 4.4 K. The second is NbTi, which must be cooled to about 1.9 K in superfluid helium. In this paper the costs of 5-cm-bore, 6-m-long magnets made of these materials and operating at fields from 5 to 11 T are compared. At 10 T the capital cost of a NbTi coil operating in superfluid helium is 35% less than the cost of a Nb/sub 3/Sn coil. The cost of the NbTi coil is still 10% less after the differential operating costs that will be incurred over the life of the accelerator are included. The results presented here are a summary of a detailed analysis of these costs given in a separate report.
Date: November 1, 1982
Creator: Hassenzahl, W.V.
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