219 Matching Results

Results open in a new window/tab.

A 40 mm bore quadrupole magnet for the SSC (open access)

A 40 mm bore quadrupole magnet for the SSC

A 40 mm bore quadrupole magnet design, called QC'', has been made for the SSC with the following parameters: 208 T/m gradient at 6500A, 2-layer cos 2 {theta}'' winding arrangement with 30 strand cable and one spacer wedge per coil. Structural support is provided by self-supporting interlocking collars; two types of symmetrical laminations are pre-assembled into collar packs for ease of assembly. This paper will describe the design of a prototype quadrupole magnet for the SSC and preliminary tests results on 1 m models. 7 refs., 6 figs., 2 tabs.
Date: September 1, 1990
Creator: Taylor, C.E.; Barale, P.; Caspi, S.; Dell'Orco, D.; Fritz, D.; Gilbert, W.S. et al.
System: The UNT Digital Library
Mechanical and electromagnetic analysis of 50 millimeter designs for the SSC dipole (open access)

Mechanical and electromagnetic analysis of 50 millimeter designs for the SSC dipole

Several designs for the Superconducting Super Collider dipole magnet have been analyzed. This note discusses the mechanical and electromagnetic features of each design. Electromagnetic and Mechanical analyses were performed using hand, computer programs and finite element techniques to evaluate the design. 10 refs., 6 figs., 3 tabs.
Date: September 1, 1990
Creator: Jayakumar, J.; Leung, K.; Nobrega, F.; Orrell, D.; Sanger, P.; Snitchler, G. et al.
System: The UNT Digital Library
Quench propagation in the SSC dipole magnets (open access)

Quench propagation in the SSC dipole magnets

The effects of quench propagation are modeled in 40mm and 50mm diameter collider dipole magnet designs. A comparative study of the cold diode (passive) and quench heater (active) protection schemes will be presented. The SSCQ modeling program accurately simulates the axial quench velocity and uses phenomenological time delays for turn-to-turn transverse propagation. The axial quench velocity is field dependent and consequently, each conductor's quench profile is tracked separately. No symmetry constraints are employed and the distribution of the temperatures along the conductor differs from the adiabatic approximation. A single magnet has a wide margin of self protection which suggests that passive protection schemes must be considered. 6 refs., 3 figs., 1 tab.
Date: September 1, 1990
Creator: Lopez, G. & Snitchler, G.
System: The UNT Digital Library
Resolutions to difficulties experienced in SSC cable fabrication during the initial scale-up period (open access)

Resolutions to difficulties experienced in SSC cable fabrication during the initial scale-up period

Late in 1988, a prototype high speed cable machine was built by industry and delivered in FY88 for the Superconducting Super Collider (SSC), and delivered to New England Electric Wire Corp. for the fabrication of SSC cable. This cabling machine has produced the majority of the cable needed for the SSC Dipole Program. During the past year and a half we have experienced several cabling difficulties that were not seen previously. These difficulties were due to new techniques and equipment relating to the high speed production of cable meeting SSC specifications. These difficulties included mandrel alignment, Turk's-head roller alignment, and Turk's-head drive equipment. The solution to these problems are discussed with the SSC specification in detail. 2 refs., 6 figs.
Date: September 1, 1990
Creator: Hannaford, R.; Christopherson, D.; Remsbottom, B. (Superconducting Super Collider Lab., Dallas, TX (United States)) & Boivin, M. (New England Electric Wire Corp., Lisbon, NH (United States))
System: The UNT Digital Library
Simulation of a Standing-Wave Free-Electron Laser (open access)

Simulation of a Standing-Wave Free-Electron Laser

The standing-wave free-electron laser (FEL) differs from a conventional linear-wiggler microwave FEL in using irises along the wiggler to form a series of standing-wave cavities and in reaccelerating the beam between cavities to maintain the average energy. The device has been proposed for use in a two-beam accelerator (TBA) because microwave power can be extracted more effectively than from a traveling-wave FEL. The standing-wave FEL is modeled in the continuum limit by a set of equations describing the coupling of a one-dimensional beam to a TE{sub 01} rectangular-waveguide mode. Analytic calculations and numerical simulations are used to determine the time variation of the reacceleration field and the prebunching required so that the final microwave energy is the same in all cavities. The microwave energy and phase are found to be insensitive to modest spreads in the beam energy and phase and to errors in the reacceleration field and the beam current, but the output phase appears sensitive to beam-energy errors and to timing jitter.
Date: September 1, 1990
Creator: Sharp, W. M.; Sessler, A. M.; Whittum, D. H. & Wurtele, J. S.
System: The UNT Digital Library
The Advanced Light Source: A new tool for research in atomic physics (open access)

The Advanced Light Source: A new tool for research in atomic physics

The Advanced Light Source, a third-generation national synchrotron-radiation facility now under construction at the Lawrence Berkeley Laboratory in Berkeley, California, is scheduled to begin serving qualified users across a broad spectrum of research areas in the spring of 1993. Undulators will generate high-brightness, partially coherent, plane polarized, soft-x-ray and ultraviolet (XUV) radiation from below 10 eV to above 2 keV. Wigglers and bend magnets will generate high fluxes of x-rays to photon energies above 10 keV. The ALS will have an extensive research program in which XUV radiation is used to study matter in all its varied gaseous, liquid, and solid forms. 7 refs., 3 figs.
Date: September 1, 1990
Creator: Schlachter, A.S.
System: The UNT Digital Library
Fabrication of an infrared bolometer with a high T sub c superconducting thermometer (open access)

Fabrication of an infrared bolometer with a high T sub c superconducting thermometer

A sensitive high {Tc} superconducting bolometer has been fabricated on a 20 {mu}m thick sapphire substrate with a YBCO thin film transition edge thermometer. Optical measurements with a He-Ne laser gave a noise equivalent power of 2.4{center dot}10{sup {minus}11} W/Hz{sup 1/2} at 10 Hz and a responsivity of 17 V/W in good agreement with electrical bolometer measurements. Gold black smoke was then deposited on the back side of the assembled bolometer as an absorber. Spectral measurements on a Fourier transform spectrometer show that the bolometer has useful sensitivity from visible wavelengths to beyond {approximately}100 {mu}m. This performance is clearly superior to that of a commercial room temperature pyroelectric detector. Some improvement appears possible. 10 refs., 5 figs.
Date: September 1, 1990
Creator: Vergjese, S.; Richards, P.L. (California Univ., Berkeley, CA (USA). Dept. of Physics Lawrence Berkeley Lab., CA (USA)); Char, K. & Sachtjen, S.A. (Conductus, Inc., Sunnyvale, CA (USA))
System: The UNT Digital Library
Photofragment imaging: The photo-dissociation of bromomethane, bromoethane, and bromoethanol (open access)

Photofragment imaging: The photo-dissociation of bromomethane, bromoethane, and bromoethanol

Bromomethane, bromoethane and bromoethanol are photolyzed with 205-nm light and the velocity of the bromine atoms is recorded by the technique of photofragment imaging. The velocity distribution of the bromine atoms is a direct reflection of the internal-state distribution of the methyl, ethyl, and hydroxy-ethyl radicals and the orientation of the transition moment in the parent molecule. 8 refs., 2 figs., 1 tab.
Date: September 1, 1990
Creator: Chandler, D.W. (Sandia National Labs., Albuquerque, NM (United States)); Thoman, J.W. Jr. (Williams Coll., Williamstown, MA (United States). Dept. of Chemistry) & Hess, W.P. (Battelle Pacific Northwest Lab., Richland, WA (United States))
System: The UNT Digital Library
Isotopically selective RIMS of rare radionuclides by double-resonance excitation with cw lasers (open access)

Isotopically selective RIMS of rare radionuclides by double-resonance excitation with cw lasers

Double-resonance, Resonance Ionization Mass Spectroscopy (RIMS) using two single-frequency dye lasers and a CO{sub 2} laser for photoionization has been shown to be both extremely sensitive and highly selective. Measurements on the radioisotope {sup 210}Pb have demonstrated optical selectivity in excess of 10{sup 9} and detection limits of less than 1 femtogram.
Date: September 1, 1990
Creator: Bushaw, B. A. & Munley, J. T.
System: The UNT Digital Library
Texture analysis of bulk YBa sub 2 Cu sub 3 O sub x by neutron diffraction (open access)

Texture analysis of bulk YBa sub 2 Cu sub 3 O sub x by neutron diffraction

Neutron diffraction has been used to generate Orientation Distribution Functions for two sinter-forged YBa{sub 2}Cu{sub 3}O{sub x} specimens. Sinter forging imparted a strong texture, with c axes of crystals preferentially aligned parallel to the forging direction. The distribution of a and b axes was not uniform, which may have implications to critical current density. 14 refs., 6 figs.
Date: September 1, 1990
Creator: Kallend, J.S. (Illinois Inst. of Tech., Chicago, IL (USA)); Biondo, A.C.; Schultz, A.J. & Goretta, K.C. (Argonne National Lab., IL (USA))
System: The UNT Digital Library
Development of scaling rules for Rutherford type superconducting cables (open access)

Development of scaling rules for Rutherford type superconducting cables

During the R D phase of the Superconducting Supercollider (SSC) program, LBL was responsible for establishing the parameters for cables used in SSC dipole and quadrupole magnets. In addition, the design and fabrication of a new cable for use in the Low Beta Quadrupoles. As a result of the development work on these and other cables, we have arrived a set of scaling rules which provide guidelines for choosing the parameters for a wide range of superconducting cables. These parameters include strand size, strand number, keystone angle, percent compaction, cable pitch and compacted cable dimensions. In addition, we have defined the tolerance ranges for the key cable manufacturing parameters such as mandrel size and shape, stand tension, and Turkshead temperature control. In this paper, we present the results on cables ranging from 8 strands to 36 strands of 0.65mm wire and from 8 strands to 30 strands of 0.8mm wire. We use these results to demonstrate the application of the scaling rules for Rutherford-type cable.
Date: September 1, 1990
Creator: Royet, J. M. & Scanlan, R. M.
System: The UNT Digital Library
Performance of the 2 MeV microwave gun for the SSRL 150 MeV linac (open access)

Performance of the 2 MeV microwave gun for the SSRL 150 MeV linac

As described in a previous article, the preinjector linac for SSRL's 3 GeV synchrotron is fed by a 2 MeV, 1.5 A, low-emittance microwave gun, consisting of a thermionic cathode mounted in the first cell of a 1-1/2-cell S-band cavity. In this article, we report on the successful operation of the low-emittance gun, the longitudinally-bunching alpha-magnet, and the three-microbunch FET-pulsed beam-chopper. Simulations predict a normalized rms emittance at the gun exit of less than 10 {pi}{center dot}m{sub e}c{center dot}{mu}m; chromatic effects in transport optics increase this to approximately 30 {pi}{center dot}m{sub e}c{center dot}{mu}m. The gun was specifically designed to have a longitudinal phase-space suited to magnetic compression, as a result of which we predict that peak currents in excess of 300 A in a 1 ps bunch are feasible with the existing alpha-magnet. Results of simulations and experiments will be presented and compared. 13 refs., 9 figs.
Date: September 1, 1990
Creator: Borland, M.; Weaver, J. N.; Wiedemann, H. (Stanford Univ., CA (USA). Stanford Synchrotron Radiation Lab.); Green, M. C.; Nelson, L. V. (Varian Associates, Inc., Palo Alto, CA (USA)); Miller, R. H. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)) et al.
System: The UNT Digital Library
Erosion and redeposition of divertor and wall materials during abnormal events (open access)

Erosion and redeposition of divertor and wall materials during abnormal events

High energy deposition to in-vessel components of fusion reactors is expected to occur during abnormal operating conditions. This high energy dump in short times may result in very high surface temperatures and can cause severe erosion as a result of melting and vaporization of these components. One abnormal operating condition results from plasma disruptions where the plasma loses confinement and dumps its energy on reactor components. Another abnormal condition occurs when a neutral beam used in heating the plasma shines through the vacuum vessel to parts of the wall with no plasma present in the chamber. A third abnormal event that results in high energy deposition is caused by the runaway electrons to chamber components following a disruption. The failure of these components under the expected high heat loads can severely limit the operation of the fusion device. The redeposition of the eroded materials from these abnormal events over the first wall and other components may cause additional problems. Such problems are associated with tritium accumulation in the freshly deposited materials, charge exchange sputtering and additional impurity sources, and material compatibility issues.
Date: September 1, 1990
Creator: Hassanein, A.
System: The UNT Digital Library
Cryostat design for the Superconducting Super Collider (open access)

Cryostat design for the Superconducting Super Collider

The cryostat of an SSC dipole magnet consists of all magnet components except the cold mass assembly. It serves to support the cold mass accurately and reliably within the vacuum vessel, provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations and must be manufacturable at low cost. The major components of the cryostat are the vacuum vessel, thermal shields, multilayer insulation (MLI) system, cryogenic piping, interconnections, and suspension system. The overall design of a cryostat for superconducting accelerator magnets requires consideration of fluid flow, proper selection of materials for their thermal and structural performance at both ambient and operating temperature, and knowledge of the environment to which the magnets will be subjected over the course their 25 year expected life. This paper describes the design of the current SSC collider dipole magnet cryostat and includes discussions on the thermal, structural, and dynamic considerations involved in the development of each of the major systems. 7 refs., 4 figs.
Date: September 1, 1990
Creator: Nicol, T.H.
System: The UNT Digital Library
Lattice gas simulations of one and two-phase fluid flows using the Connection Machine-2 (open access)

Lattice gas simulations of one and two-phase fluid flows using the Connection Machine-2

In this paper, we report recent lattice gas simulations for single-phase and two-phase flows for two dimensional problems using the Connection Machine-2. For the single-phase fluid problem, we use the standard 7-bit lattice gas model with the maximum collision rules. The velocity and vorticity field of the Kelvin-Helmholtz instability is studied. It is shown that the lattice gas method preserves the main properties of the flow patterns observed in other numerical simulations. Using colored particles and holes, the lattice gas method is extended to simulate immiscible fluids with adjustable surface tension, using a purely local collision scheme. The locality of this model allows us to implement a very fast and parallel algorithm on the Connection Machine-2. Because this new model correctly describes short-range particle-particle interactions between liquids and also particle-solid interactions between the fluid and the wall, cohesion and wettability can be simulated. Applications of the current model to several physical systems including spinodal decomposition, Rayleigh-Taylor flows and wettability in two-phase flows through porous media are discussed. 15 refs., 10 figs.
Date: 1990-09~
Creator: Chen, S.; Doolen, G. D.; Eggert, K.; Grunau, D. & Loh, E. Y., Jr.
System: The UNT Digital Library
Ion trap measurement of U sup 64+ x-ray transition spectra (open access)

Ion trap measurement of U sup 64+ x-ray transition spectra

Highly-charged uranium ions with a dominant nickel-like component (U{sup 64+}) were produced using the Electron Beam Ion Trap (EBIT) with an electron bombardment energy of 7.4 keV. A comparison of the measured n=4 to n=3 x-ray transition spectra with calculations for U{sup 64+} gave excellent qualitative agreement. The low-energy region of the 4-3 spectrum for the Ni-like ions was characterized by a strong electric quadrupole 4s-3d transition, about as large as the leading dipole 4f-3d transition, which tagged the abundance of U{sup 64+} ions. High resolution spectroscopy was used to measure 4f-3d transition energies for ten charge states: U{sup 60+}-U{sup 69+} excited by 6.4-8.9 keV electrons. The ionization balance for 8.9 keV electron excitation was mostly from five charge states: U{sup 64+}-U{sup 68+} in qualitative agreement with a separate analysis of extracted ions. 16 refs., 4 figs., 3 tabs.
Date: September 1, 1990
Creator: Del Grande, N. K.; Beiersdorfer, P.; Henderson, J. R.; Osterheld, A. L.; Scofield, J. H. & Swenson, J. K.
System: The UNT Digital Library
First-order inflation (open access)

First-order inflation

In the original proposal, inflation occurred in the process of a strongly first-order phase transition. This model was soon demonstrated to be fatally flawed. Subsequent models for inflation involved phase transitions that were second-order, or perhaps weakly first-order; some even involved no phase transition at all. Recently the possibility of inflation during a strongly first-order phase transition has been revived. In this talk I will discuss some models for first-order inflation, and emphasize unique signatures that result in inflation is realized in a first-order transition. Before discussing first-order inflation, I will briefly review some of the history of inflation to demonstrate how first-order inflation differs from other models. 58 refs., 3 figs.
Date: September 1, 1990
Creator: Kolb, E.W. (Fermi National Accelerator Lab., Batavia, IL (USA) Chicago Univ., IL (USA). Enrico Fermi Inst.)
System: The UNT Digital Library
DOE's Computer Incident Advisory Capability (CIAC) (open access)

DOE's Computer Incident Advisory Capability (CIAC)

Computer security is essential in maintaining quality in the computing environment. Computer security incidents, however, are becoming more sophisticated. The DOE Computer Incident Advisory Capability (CIAC) team was formed primarily to assist DOE sites in responding to computer security incidents. Among CIAC's other responsibilities are gathering and distributing information to DOE sites, providing training workshops, coordinating with other agencies, response teams, and vendors, creating guidelines for incident handling, and developing software tools. CIAC has already provided considerable assistance to DOE sites faced with virus infections and worm and hacker attacks, has issued over 40 information bulletins, and has developed and presented a workshop on incident handling. CIAC's experience in helping sites has produced several lessons learned, including the need to follow effective procedures to avoid virus infections in small systems and the need for sound password management and system administration in networked systems. CIAC's activity and scope will expand in the future. 4 refs.
Date: September 1, 1990
Creator: Schultz, E.
System: The UNT Digital Library
Simulation of a standing-wave free-electron laser (open access)

Simulation of a standing-wave free-electron laser

The standing-wave free-electron laser (FEL) differs from a conventional linear-wiggler microwave FEL in using irises along the wiggler to form a series of standing-wave cavities and in reaccelerating the beam between cavities to maintain the average energy. The device has been proposed for use in a two-beam accelerator (TBA) because microwave power can be extracted more effectively than from a traveling-wave FEL. The standing-wave FEL is modeled in the continuum limit by a set of equations describing the coupling of a one-dimensional beam to a TE{sub 01} rectangular-waveguide mode. Analytic calculations and numerical simulations are used to determine the time variation of the reacceleration field and the prebunching required so that the final microwave energy is the same in all cavities. The microwave energy and phase are found to be insensitive to modest spreads in the beam energy and phase and to errors in the reacceleration field and the beam current, but the output phase appears sensitive to beam-energy errors and to timing jitter.
Date: September 1, 1990
Creator: Sharp, W. M. (Lawrence Livermore National Lab., CA (USA)); Sessler, A. M.; Whittum, D. H.; Wurtele, J. S. (Lawrence Berkeley Lab., CA (USA)); McDermott, D. & Luhmann, N. (California Univ., Los Angeles, CA (USA))
System: The UNT Digital Library
US--ITER activation analysis (open access)

US--ITER activation analysis

Activation analysis has been made for the US ITER design. The radioactivity and the decay heat have been calculated, during operation and after shutdown for the two ITER phases, the Physics Phase and the Technology Phase. The Physics Phase operates about 24 full power days (FPDs) at fusion power level of 1100 MW and the Technology Phase has 860 MW fusion power and operates for about 1360 FPDs. The point-wise gamma sources have been calculated everywhere in the reactor at several times after shutdown of the two phases and are then used to calculate the biological dose everywhere in the reactor. Activation calculations have been made also for ITER divertor. The results are presented for different continuous operation times and for only one pulse. The effect of the pulsed operation on the radioactivity is analyzed. 6 refs., 12 figs., 1 tab.
Date: September 1, 1990
Creator: Attaya, H.; Gohar, Y. & Smith, D.
System: The UNT Digital Library
Use of probability analysis to establish routine bioassay screening levels (open access)

Use of probability analysis to establish routine bioassay screening levels

Probability analysis was used by the Hanford Internal Dosimetry Program to establish bioassay screening levels for tritium and uranium in urine. Background environmental levels of these two radionuclides are generally detectable by the highly sensitive urine analysis procedures routinely used at Hanford. Establishing screening levels requires balancing the impact of false detection with the consequence of potentially undetectable occupation dose. To establish the screening levels, tritium and uranium analyses were performed on urine samples collected from workers exposed only to environmental sources. All samples were collected at home using a simulated 12-hour protocol for tritium and a simulated 24-hour collection protocol for uranium. Results of the analyses of these samples were ranked according to tritium concentration or total sample uranium. The cumulative percentile was calculated and plotted using log-probability coordinates. Geometric means and screening levels corresponding to various percentiles were estimated by graphical interpolation and standard calculations. The potentially annual internal dose associated with a screening level was calculated. Screening levels were selected corresponding to the 99.9 percentile, implying that, on the average, 1 out of 1000 samples collected from an unexposed worker population would be expected to exceed the screening level. 4 refs., 2 figs.
Date: September 1, 1990
Creator: Carbaugh, E.H.; Sula, M.J. & McFadden, K.M.
System: The UNT Digital Library
High electric fields in a superconducting RFQ structure (open access)

High electric fields in a superconducting RFQ structure

High surface electric fields have been obtained in the first tests of a superconducting rf quadrupole device. The rf quadrupole fields were generated between niobium vanes 6.5 cm in length, with an edge radius of 2 mm, and with a beam aperture of 6 mm diameter. In tests at 4.2 K, the 64 MHz device operated cw at peak surface electric fields of 128 MV/m. Virtually no electron loading was observed at fields below 100 MV/m. It was possible to operate at surface fields of 210 MV/m in pulses of 1 msec duration using a 2.5 kW rf source. For the vane geometry tested, more than 10 square centimeters of surface support a field greater than 90% of the peak field. The present result indicates that electric fields greater than 100 MV/m can be obtained over an appreciable area, sufficient for some accelerator applications. It also shows that superconducting rf technology may provide an extended range of options for rf quadrupole design. 7 refs., 4 figs.
Date: September 24, 1990
Creator: Delayen, J.R. & Shepard, K.W.
System: The UNT Digital Library
Superdeformed band relationships, mass-190 region (open access)

Superdeformed band relationships, mass-190 region

A new region of superdeformed (SD) bands in the mercury nuclei has been extended to the thallium and lead isotopes. A surprising number of excited, as well as yrast, bands have been found, and they have very interesting properties. So far 25 such bands have been observed, including six in one nucleus, {sup 194}Tl. They show some startling features. More than half have transition energies equivalent within a few keV to transitions in other SD bands in the region. And in these examples the relative alignments with respect to an optimum reference SD band is not often integral with the value l{Dirac h}, whether comparing an odd- or an even-mass nucleus with the reference. We believe the pseudo-spin formalism gives clues to explaining these features, but not the fact that changes in orbital alignment, in deformation, in pairing, and in mass seem to cancel almost perfectly although individually they may cause larger variations than are observed. Perhaps some new basic physics is involved, or at least some new symmetries. 24 refs., 11 figs.
Date: September 1, 1990
Creator: Diamond, R. M.
System: The UNT Digital Library
QCD phenomenology of parton distribution functions at small x (open access)

QCD phenomenology of parton distribution functions at small x

The small x behavior of parton distributions is studied phenomenologically by examining in detail a series of QCD-evolved distribution sets obtained in a new global analysis of deep inelastic scattering and lepton-pair production experiments. The importance of 2-loop evolution is discussed. The main features and results of the global analysis are described. The range of small x behavior consistent with next-to-leading order QCD and current data is delineated. The extrapolated small x behavior is parameterized by effective Q-dependent power- and logarithmic-law parameters. Intriguing features of the evolution of these parameters with Q are presented. Alternative parametrizations based on the analytic solution for small x is also explored. 20 refs., 6 figs., 1 tab.
Date: September 1, 1990
Creator: Tung, Wu-Ki (Illinois Inst. of Tech., Chicago, IL (USA) Fermi National Accelerator Lab., Batavia, IL (USA))
System: The UNT Digital Library