10 Matching Results

Results open in a new window/tab.

The Study of Parametric Instabilities in Nif-Scale Plasmas on Nova (open access)

The Study of Parametric Instabilities in Nif-Scale Plasmas on Nova

At the same time we experimentally reproduced the plasma conditions expected within the NIF using plasmas produced by the Nova laser. The plasmas were created by irradiating a thin walled gas balloon or a sealed hohlraum containing of order one atmosphere of a low-Z gas (e.g. C{sub 5}H{sub 12}, C{sub 5}D{sub 12} or CO{sub 2}). When the gas is ionized and heated the resultant plasmas are homogeneous, and of high density ({approximately}10{sup 21} electron/cm{sup 3}) and temperature ({approximately}3 keV) with large scale density scale lengths ({approximately}2 mm). Nine of the Nova beams were used to produce the plasma, the tenth beam was configured as an interaction beam that was sent through the performed plasma after a delay of order 500 psec. The SRS and SBS scattered from the plasma, together with the effects of the plasma on the transmitted beam, were studied as a function of the interaction beam intensity, beam smoothing and plasma constituents. The interaction beam was smoothed by using radon phase plates (RPPs), and 4 different colors within the f/8 beam to mimic the NIF laser architecture. The 4-color set-up divided the f/8 beam in to 4 separate quadrants each of which had its wavelength shifted relative …
Date: September 26, 1994
Creator: MacGowan, B. J.; Back, C. A. & Berger, R. L.
System: The UNT Digital Library
Determination of the concentration and isotopic composition of uranium in environmental air filters (open access)

Determination of the concentration and isotopic composition of uranium in environmental air filters

For many years, Lawrence Livermore National Laboratory has collected monthly air-particulate filter samples from a variety of environmental monitoring stations on and off site. Historically the concentration and isotopic composition of uranium collected on these filters was determined by isotope dilution using a {sup 233}U spike and thermal ionization mass spectrometry (TIMS). For samples containing as little as 10 nanograms of uranium, ICP-MS is now used to make these measurements to the required level of precision, about 5% in the measured 235/238 and 233/238. Unless particular care is taken to control bias in the mass filter, variable mass bias limits accuracy to a few percent. Measurements of the minor isotopes 236 (if present) and 234 are also possible and provide useful information for identifying the source of the uranium. The advantage of ICP-MS is in rapid analysis, {approximately}12 minutes of instrument time per sample.
Date: August 26, 1994
Creator: Russ, G. P., III & Bazan, J. M.
System: The UNT Digital Library
Wentzel-Bardeen singularity in coupled Luttinger liquids: Transport properties (open access)

Wentzel-Bardeen singularity in coupled Luttinger liquids: Transport properties

The recent progress on 1 D interacting electrons systems and their applications to study the transport properties of quasi one dimensional wires is reviewed. We focus on strongly correlated elections coupled to low energy acoustic phonons in one dimension. The exponents of various response functions are calculated, and their striking sensitivity to the Wentzel-Bardeen singularity is discussed. For the Hubbard model coupled to phonons the equivalent of a phase diagram is established. By increasing the filling factor towards half filling the WB singularity is approached. This in turn suppresses antiferromagnetic fluctuations and drives the system towards the superconducting regime, via a new intermediate (metallic) phase. The implications of this phenomenon on the transport properties of an ideal wire as well as the properties of a wire with weak or strong scattering are analyzed in a perturbative renormalization group calculation. This allows to recover the three regimes predicted from the divergence criteria of the response functions.
Date: August 26, 1994
Creator: Martin, T.
System: The UNT Digital Library
Beryllium based multilayers for normal incidence extreme ultraviolet reflectivity (open access)

Beryllium based multilayers for normal incidence extreme ultraviolet reflectivity

The need for normal incidence mirrors maintaining reflectivity greater than 60% for an industrially competitive Extreme Ultraviolet Lithography (EUV) system has been well documented. The Molybdenum/Silicon system has emerged as the de-facto standard, where researchers are now routinely fabricating mirrors demonstrating 63% reflectivity near 130 Angstroms. However, multilayer mirrors using beryllium as the low atomic number (low-Z) spacer could potentially show similar or better reflectivity, and operate at wavelengths down to the beryllium K-edge at 111 Angstroms. Besides offering potentially greater reflectivity, the shorter wavelength light offers increased dissolution depth in photoresists, and offers potentially better resolution and depth of focus. We will report our latest results from beryllium based multilayers. The mirrors were fabricated at the Lawrence Livermore National Laboratory (LLNL) and tested at the Center for X-Ray Optics at Lawrence Berkeley Laboratory (CXRO/LBL).
Date: May 26, 1994
Creator: Skulina, K. M.; Alford, C.; Bionta, R. M.; Makowiecki, D. M.; Kortright, J.; Soufli, R. et al.
System: The UNT Digital Library
Measurement of the polarization in the decay B{sup 0} {yields} J/{psi}K{sup *0} in {bar p}p collisions at {radical}s = 1.8 TeV (open access)

Measurement of the polarization in the decay B{sup 0} {yields} J/{psi}K{sup *0} in {bar p}p collisions at {radical}s = 1.8 TeV

This paper reports on the measurement of the polarization in the decay B{sup o} {yields} J/{psi}K{sup *o} using data collected at the collider Detector at Fermilab in {bar p}p collisions at {radical}s = 1.8 TeV. B{sup O} mesons were reconstructed through the decay chain B{sup o} {yields} J/{psi}K{sup *o}, J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}, K{sup *o} {yields} K{sup +}{pi}{sup {minus}}. A sample of 50 {plus_minus} 11 events was used in the measurement, yielding the result {Gamma}{sub L}/{Gamma} = 0.66 {plus_minus} 0.10 (stat) {sub {minus}}0.10 {sup +0.08} (sys).
Date: May 26, 1994
Creator: CDF Collaboration
System: The UNT Digital Library
Power conditioning for the National Ignition Facility (open access)

Power conditioning for the National Ignition Facility

A cost-effective, 320-MJ power-conditioning system has been completed for the proposed National Ignition Facility (NIF). The design features include metallized dielectric capacitors, a simple topology, and large (1.6-MJ) module size. Experimental results address the technical risks associated with the design.
Date: May 26, 1994
Creator: Larson, D. W.; Anderson, R. & Boyes, J.
System: The UNT Digital Library
Scoping economics for the commercial manufacture of metallocene catalysts (open access)

Scoping economics for the commercial manufacture of metallocene catalysts

This study assumes that commercial-scale production of propylene-based isotactic polymers with metallocene catalyst systems will become a reality. The challenge that must be overcome for commercial success with these propylene polymers is to discover a metallocene system recipe that will give sufficient catalyst activity along with the requisite stereo-selectivity at reasonable cost. Anticipating such a discovery, it is assumed here that the economics are well-represented by a catalyst system that consists in part of a silylene-bridged cyclopentadienyl zirconocene made in a batchwise process having an annual capacity of 15,000 pounds. Activation will be achieved with a cocatalyst such as methylaluminoxane (MAO), coated in conjunction with the catalyst on a support such as silica. The MAO at an estimated $100/lb contributes $1800/lb cost to the finished catalyst with an assumed recipe of 18:1 mass ratio of MAO to zirconocene. Based on a 20% return on investment, the selling price for the supported zirconocene system is estimated to be $2915/lb. The required capital investment to make 735,000 lb/yr of the total supported system is 9 million dollars. These estimates have {plus_minus}50% range of uncertainty. Payback period for this plant in a sold-out condition is three years. The catalyst system cost in ethylene-propylene …
Date: May 26, 1994
Creator: Brockmeier, N. F.
System: The UNT Digital Library
A Structural Determination Using Magnetic X-Ray Circular Dichroism in Spin-Polarized Photoelectron Diffraction (open access)

A Structural Determination Using Magnetic X-Ray Circular Dichroism in Spin-Polarized Photoelectron Diffraction

The first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produce spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p{sup 3/2} level are observed. . Fully spin-specific multiple scattering calculations reproduce the experimentally determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced.
Date: May 26, 1994
Creator: Waddill, G. D.; Tobin, J. G.; Guo, X. & Tong, S. Y.
System: The UNT Digital Library
A freon-filled, holographic bubble chamber as a high energy photon burst spectrometer (open access)

A freon-filled, holographic bubble chamber as a high energy photon burst spectrometer

A small holographic, freon-filled bubble chamber is being built to measure the energy spectrum of high-energy photons (energy above a few 100 keV) emitted in a short burst (less than about 1 ms duration). The photon energy is calculated from the scattered electron`s energy and direction in the case of Compton scattering or from the electron and positron energies in the case of pair production. Electron and positron energies are determined from the curvature of the tracks in a magnetic field. The use of freon results in a large photon interaction probability. Holography combines good spatial resolution with large depth of field. The main concern for the holographic system is the minimization of the bubble image size, so as to maximize the number of bubbles visible in one hologram. A high energy photon burst spectrometer has several potential applications in Inertial Confinement Fusion research.
Date: April 26, 1994
Creator: Dendooven, P. G. & Lerche, R. A.
System: The UNT Digital Library
News from LBL (open access)

News from LBL

We present a brief summary of recent news from LBL related to accelerator physics. This talk was given on October 29, 1993 at the 6th Advanced ICFA Beam Dynamics Workshop on the subject ``Synchro- Betraton Resonances,`` held in Funchal (Madeira, Portugal), October 24--30, 1993.
Date: January 26, 1994
Creator: Furman, M. A.
System: The UNT Digital Library