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Non-linear instability of DIII-D to error fields
Otherwise stable DIII-D discharges can become nonlinearly unstable to locked modes and disrupt when subjected to resonant m = 2, n = 1 error field caused by irregular poloidal field coils, i.e. intrinsic field errors. Instability is observed in DIII-D when the magnitude of the radial component of the m = 2, n = 1 error field with respect to the toroidal field is B{sub r21}/B{sub T} of about 1.7 {times} 10{sup {minus}4}. The locked modes triggered by an external error field are aligned with the static error field and the plasma fluid rotation ceases as a result of the growth of the mode. The triggered locked modes are the precursors of the subsequent plasma disruption. The use of an n = 1 coil'' to partially cancel intrinsic errors, or to increase them, results in a significantly expanded, or reduced, stable operating parameter space. Precise error field measurements have allowed the design of an improved correction coil for DIII-D, the C-coil'', which could further cancel error fields and help to avoid disruptive locked modes. 6 refs., 4 figs.
Date:
October 1, 1991
Creator:
La Haye, R. J. & Scoville, J. T.
System:
The UNT Digital Library
Fifth high-energy heavy-ion study
This was the fifth of a continuing series of summer studies held at LBL to discuss high energy heavy ion collisions. Recently, a similar meeting has been held on alternate years at GSI (Darmstadt); and, in 1979, we held a meeting at LBL exclusively devoted to ultra-relativistic nuclear collisions. Two new features distinguish this study from earlier meetings in the series. First, the energy range for discussion was broadened by including collisions from about 20 MeV/nucleon to the highest available in the cosmic radiation. The lower range, particularly below 100 MeV/nucleon, will be under intense study in the near future with machines such as the upgraded Bevalac, Michigan State University Superconducting Cyclotron, GANIL in France, and the SC at CERN. Recently, the high energy collision regime has been expanded by the successful operation of the CERN ISR with alpha particles. Second, in addition to an extensive program of invited talks, we decided for the first time to actively solicit contributions. Forty-seven individual items from the conference were prepared separately for the data base. (GHT)
Date:
October 1, 1981
Creator:
unknown
System:
The UNT Digital Library
Two-photon physics
A new experimental frontier has recently been opened to the study of two photon processes. The first results of many aspects of these reactions are being presented at this conference. In contrast, the theoretical development of research ito two photon processes has a much longer history. This talk reviews the many different theoretical ideas which provide a detailed framework for our understanding of two photon processes.
Date:
October 1, 1981
Creator:
Bardeen, W.A.
System:
The UNT Digital Library
Light Absorption and Scattering Mechanisms in Laser Fusion Plasmas
The picture of laser light absorption and scattering which is emerging from theory and computer simulation studies of laser-plasma interactions is described. On the subject of absorption, we discuss theoretical and experimental evidence that resonance absorption in a steepened density profile is a dominant absorption mechanism. Recent work also indicates the presence of critical surface ripples, which we study using two and three dimensional computer simulations. Predictions of hot electron spectra due to resonance absorption are described, as are effects of plasma outflow. We then discuss two regimes where stimulated scattering may occur. Brillouin scattering is expected in the underdense target blow-off, for long laser pulses, and is limited by ion heating. Raman scattering in the background gas of a reactor target chamber is predicted to be at most a 10 percent effect for 1 ..mu..m lasers.
Date:
October 4, 1977
Creator:
Barnes, C.; Estabrook, K. G.; Kruer, W. L.; Langdon, A. B.; Lasinski, B. F.; Max, C. E. et al.
System:
The UNT Digital Library
High-energy proton radiation damage of high-purity germanium detectors
Motivated by their applicability to gamma-ray spectroscopy experiments in space, quantitative studies of radiation damage effects in high-purity germanium detectors due to high-energy charged particles have been initiated with the irradiation by 6 GeV/c protons of two 1.0 cm thick planar detectors maintained at 88/sup 0/K. The threshold for resolution degradation and the annealing characteristics differs markedly from those previously observed for detectors irradiated by fast neutrons. Under proton bombardment, degradation in the energy resolution was found to begin below 7 x 10/sup 7/ protons/cm/sup 2/, and increased proportionately in both detectors until the experiment was terminated at a total flux of 5.7 x 10/sup 8/ protons/cm/sup 2/, equivalent to about a six year exposure to cosmic-ray protons in space. At the end of the irradiation, the FWHM resolution measured at 1332 keV stood at 8.5 and 13.6 keV, with both detectors of only marginal utility as a spectrometer due to the severe tailing caused by charge trapping. The two detectors displayed a significant difference in proton damage sensitivity, which is consistent with fast neutron damage effects. To ensure that detector variability did not influence the comparison of proton- and neutron-induced damage effects, one of the detectors had been used …
Date:
October 1, 1977
Creator:
Pehl, R.H.; Varnell, L.S. & Metzger, A.E.
System:
The UNT Digital Library
Calorimetric and optical beam diagnostics on the LBL 120-keV neutral beam test facility
The 120-keV Neutral Beam Test Facility at LBL is fitted with several types of instrumentation to determine the properties of the 10- to 15-A hydrogen and deuterium beams produced in this facility. These include a neutral particle dump for measuring the temperature profile generated by the beam, and a fixed and a moveable ion dump to measure the temperature profiles generated by the various ion components after they have been swept out of the neutral beam by a bending magnet. These several dumps provide enough information to determine the power density profiles and divergences of the neutral beam and the various ion beams for comparison with theoretical calculations, the beam composition, and the neutralization efficiency. The optical beam diagnostic consists of a high-resolution spectrometer coupled with a commercial optical multichannel analyzer. These instruments analyze Doppler-shifted optical radiation from the moving neutral atoms in the beam. Analysis of data so obtained provides the aiming directions and divergences of the various energy components in the neutral beam, as well as the beam composition.
Date:
October 1, 1977
Creator:
Burrell, C. F.; Cooper, W. S.; Steele, W. F. & Smith, R. R.
System:
The UNT Digital Library
The neutrinos in muon decay
We review the available information on the identity of the neutrino states emitted in muon decay, and discuss the exotic decay {mu}{sup +} {yields} e{sup +} {bar {nu}}{sub e}{nu}{sub {mu}}. 22 refs.
Date:
October 21, 1991
Creator:
Herczeg, P.
System:
The UNT Digital Library
A comparison of spanwise aerodynamic loads estimated from measured bending moments versus direct pressure measurements on horizontal axis wind turbine blades
Two methods can be used to determine aerodynamic loads on a rotating wind turbine blade. The first is to make direct pressure measurements on the blade surface. This is a difficult process requiring costly pressure instrumentation. The second method uses measured flap bending moments in conjunction with analytical techniques to estimate airloads. This method, called ALEST, was originally developed for use on helicopter rotors and was modified for use on horizontal axis wind turbine blades. Estimating airloads using flap bending moments in much simpler and less costly because measurements can be made with conventional strain gages and equipment. This paper presents results of airload estimates obtained using both methods under a variety of operating conditions. Insights on the limitations and usefulness of the ALEST bending moment technique are also included. 10 refs., 6 figs.
Date:
October 1, 1991
Creator:
Simms, D A & Butterfield, C P
System:
The UNT Digital Library
New generation of arc and arc filament power supplies for pulsed neutral beams
The new Tandem Mirror Experiment (TMX) facility at LLL requires that neutral beams operate for pulse lengths between 25 and 100 ms. The inevitable increase in cost over the present 12-ms pulse length capability dictated that a more economical alternative to the pulse forming networks and the transformer-type arc filament power supplies currently in use be found. A study of the various alternatives and design requirements revealed that battery banks are the most economical alternative. The thermionic arc filaments have relatively simple power-supply requirements in terms of control and regulation. The battery arc filament power supply controls and electromechanical hardware heat the filaments to provide the electrons which produce the plasma. Component testing revealed problems that must be addressed in the finished production design. The battery arc power supply poses a difficult set of requirements for current control. The TMX requires current control accuracy of +-1.0 percent and rise/fall times of 50 ..mu..s. These requirements are met with a novel thyristor switching circuit. The features of the four-section battery bank design, capable of a total of 4000 A at 58 V dc, are detailed. Control hardware compatible with the current generation of pulse-forming network hardware has been developed. The cost …
Date:
October 3, 1977
Creator:
Santamaria, G.T.
System:
The UNT Digital Library
High resolution x-ray crystal spectrographs
Observation of x-ray line emissions are valuable for determining the thermodynamic state of the emitting plasma. For laser produced plasmas, diffraction crystals can be used to isolate x-ray monochromes to obtain high resolution spectral measurements. We will describe a versatile multi-crystal high resolution spectrograph used for photon energies from 0.5 to 6 keV. We will discuss a calculational package that tunes the response and sensitivity of the instrument and estimates the effect of source extent on spectral resolution. A scheme using fine slits to obtain spatial resolution with the basic instrument will also be described. An instrument is being built for Shiva diagnostics that incorporates a diffraction crystal and an x-ray streak camera. The design rationale for the crystal stage will be discussed.
Date:
October 21, 1977
Creator:
Koppel, L. N. & Eckels, J. D.
System:
The UNT Digital Library
Characterization of radioactive ion exchange media waste generated at Three Mile Island
The March 1979 accident at General Public Utilities Nuclear Corporation (GPUNC) Three Mile Island Nuclear Power Station Unit 2 (TMI-2), resulted in the transfer of more than 1100 m/sup 3/ of contaminated water to the auxiliary and fuel handling building. The principal sources of the water were the makeup and letdown purification system and the containment building sump. The contaminated water was processed through an ion exchange system designated as EPICOR II. The EPICOR-II System is a three-stage process. The contaminated water passes through a first stage of ion exchange media, designated as prefilters, and then through the second and third stages, designated as demineralizers. The majority of the activity was deposited in the first-stage prefilters, which have a maximum administrative loading limit of 1300 curies. The predominant radionuclides present in the prefilters are cesium and strontium.
Date:
October 1, 1981
Creator:
Runion, T. C.; Holzworth, R. E.; Ogle, R. E.; Burton, H. M. & Bixby, W. W.
System:
The UNT Digital Library
Tumors of the skin and soft tissues
The majority of the body surface is covered by the skin. Many internal disorders are reflected in the condition of the skin. One of the major functions of the skin is protection of the other organ systems from a variety of environmental insults. In this role, the skin itself is exposed to factors that can ultimately cause chronic diseases and cancer. Since it is relatively easy to recognize skin abnormalities, most skin cancers are brought to professional attention sooner than other types of cancer. However, due to the close resemblance between many skin neoplasms and noncancerous dermatologic disorders, these neoplasms may be mistreated for months or even years. In veterinary oncology, as in human medicine, most cancers can be effectively treated or cured following an accurate diagnosis. Once diagnosed, skin neoplasms should be aggressively treated. If causal factors are known, exposure to these factors should be limited through removal of the agent (for chemical carcinogens) or limiting exposure to the agent (for other carcinogens such as sunlight). 10 tabs. (MHB)
Date:
October 1, 1991
Creator:
Weller, R. E.
System:
The UNT Digital Library
Economics of geothermal direct-heat applications
Cost and production data from five commercial-scale geothermal direct-heat application projects are reviewed. Unit costs of geothermal energy under a variety of assumptions about production levels, costs, tax treatment, financial structure, and cost of capital are calculated and compared to prices of conventional fuels which would be displaced over the life of a geothermal project. Geothermal energy is found to be less costly than distillate fuel oil for all cases examined and cheaper than natural gas in many cases.
Date:
October 1, 1981
Creator:
Hederman, W.F. Jr. & Cohen, L.A.
System:
The UNT Digital Library
Future aircraft and potential effects on stratospheric ozone and climate
The purpose of this study is to extend the recent research examining the global environmental effects from potential fleets of subsonic and supersonic commercial aircraft. Initial studies with LLNL models of global atmospheric chemical, radiative, and transport processes have indicated that substantial decreases in stratospheric ozone concentrations could result from emissions of NO{sub x} from aircraft flying in the stratosphere, depending on fleet size and magnitude of the engine emissions. These studies used homogeneous chemical reaction rates (e.g. gas-phase chemistry). Recent evidence indicates that reactions on particles in the stratosphere may be important. Heterogeneous chemical reactions, for instance, N{sub 2}O{sub 5}and ClONO{sub 2} on background sulfuric acid aerosols, convert NO{sub x}(NO and NO{sub 2}) molecules to HNO{sub 3}. This decreases the odd oxygen loss from the NO{sub x} catalytic cycle and increases the odd oxygen loss from the Cl{sub x} catalytic cycle. By including these heterogeneous reactions in the LLNL model, the relative partitioning of odd oxygen loss between these two families changes, with the result that emissions of NO{sub x} from proposed aircraft fleets flying in the stratosphere now increase zone. Having these heterogeneous processes present also increases ozone concentration in the troposphere relative to gas-phase only chemistry calculations …
Date:
October 1, 1991
Creator:
Kinnison, D.E. & Wuebbles, D.J.
System:
The UNT Digital Library
Exploding pusher performance at fixed laser power, a theoretical model
A model for the physics of exploding pusher targets is presented which compares favorably with the predictions of the complex simulation code, LASNEX.
Date:
October 4, 1977
Creator:
Rosen, M.D. & Nuckolls, J.H.
System:
The UNT Digital Library
PNL In Vivo Phantom Library Calibration Program
None
Date:
October 1, 1991
Creator:
Olsen, P. C.; Nichols, L. L.; Sisk, D. R. (Pacific Northwest Lab., Richland, WA (United States)) & Loesch, R. M. (USDOE, Washington, DC (United States))
System:
The UNT Digital Library
Parity violation in polarized electron scattering
The weak forces are responsible for the decay of radioactive nuclei, and it was in these decay processes where parity non-conservation was first observed. Beta decay occurs through emission of e/sup +/ or e/sup -/ particles, indicating that the weak force can carry charge of both signs, and it was natural to speculate on the existence of a neutral component of the weak force. Even though weak neutral forces had not been observed it was conjectured that a neutral component of weak decay could exist, and Zel'dovich in 1957 suggested that parity violating effects may be observable in electron scattering and in atomic spectra. More than twenty years have passed since the early conjectures, and a great deal has been learned. Progress in quantum field theory led to the development of the SU(2) x U(1) gauge theory of weak and electromagnetic interactions and provided a renormalizable theory with a minimum of additional assumptions. Gauge theories predicted the existence of a new force, the neutral current interaction. This new interaction was first seen in 1973 in the Gargamelle bubble chamber at CERN. Today the neutral currents are accepted as well established, and it is the details of the neutral current structure …
Date:
October 1, 1980
Creator:
Prescott, Charles Y.
System:
The UNT Digital Library
The Advanced Light Source U8 beam line, 20--300 eV
The U8 is a beam line under construction at the Advanced Light Source (ALS). The beam line will be described along with calculations of its performance and its current status. An 8 cm period undulator is followed by two spherical collecting mirrors, an entrance slit, spherical gratings having a 15{degree} deviation angle, a moveable exit slit, and refocusing and branching mirrors. Internal water cooling is provided to the metal M1 and M2 mirrors as well as to the gratings. Calculations have been made of both the flux output and the resolution over its photon energy range of 20--300 eV. The design goal was to achieve high intensity, 10{sup 12} photons/sec, at a high resolving power of 10,000. The U8 Participating Research Team (PRT) is planning experiments involving the photoelectron spectroscopy of gaseous atoms and molecules, the spectroscopy of ions and actinide spectroscopy.
Date:
October 1, 1991
Creator:
Heimann, P.; Warwick, T.; Howells, M.; McKinney, W.; Digennaro, D.; Gee, B. et al.
System:
The UNT Digital Library
Some frontiers of accelerator physics
This paper discusses some concepts of future accelerators such as free electron lasers, two beam accelerator; and plasma-based adiabatic compressor. 12 refs., 10 figs., 5 tabs. (LSP)
Date:
October 13, 1989
Creator:
Sessler, A. M.
System:
The UNT Digital Library
Modeling of coupled geochemical and transport processes: An overview
Early coupled models associated with fluid flow and solute transport have been limited by assumed conditions of constant temperature, fully saturated fluid flow, and constant pore fluid velocity. Developments including coupling of chemical reactions to variable fields of temperature and fluid flow have generated new requirements for experimental data. As the capabilities of coupled models expand, needs are created for experimental data to be used for both input and validation. 25 refs.
Date:
October 1, 1989
Creator:
Carnahan, C.L.
System:
The UNT Digital Library
Review of induction LINACS
There has been a recent upsurge of activity in the field of induction linacs, with several new machines becoming operational and others in the design stages. The performance levels of electron machines have reached 10's of kiloamps of current and will soon reach 10's of MeV's of energy. Acceleration of ion current has been demonstrated, and the study of a 10 GeV heavy ion induction linac for ICF continues. The operating principles of induction linacs are reviewed with the emphasis on design choices which are important for increasing the maximum beam currents.
Date:
October 1, 1981
Creator:
Faltens, A. & Keefe, D.
System:
The UNT Digital Library
Development of a high-density energy-storage capacitor for Nova
This paper covers Maxwell's approach to developing energy storage capacitors. Based on previous capacitor designs of 3 KJ, 5 KJ and 10 KJ, the final Nova 12.5 KJ capacitor evolved. At the outset of the Nova capacitor development program, a relatively new dielectric system, polypropylene-paper-DOP, seemed to show superiority in volumetric efficiency, life, and more importantly cost. However, as a result of studies performed at Maxwell, a high-density, energy-storage capacitor was developed utilizing new high-quality, high-density paper and caster oil as the dielectric. Test data have demonstrated that the Maxwell 12.5 KJ capacitor exceeds all LLNL's qualification requirements.
Date:
October 22, 1981
Creator:
Haskell, D. K.; Cooper, R. A.; Sevigny, J. A.; Merritt, B. T.; Carder, B. M. & Whitham, K.
System:
The UNT Digital Library
Growth rate of dislocation loop in Fe-Ni-Cr alloy under Kr sup + ion and electron irradiation
In order to examine the effect of irradiating particle species on the growth rate of radiation-induced dislocation loops, a solution-annealed Fe-25Ni-15Cr-0.02C alloy was irradiated at 723 K first by 1.5 MeV Kr{sup +} ions for 2520 sec, then by 1.5 MeV Kr{sup +} ions and 1.0 MeV electrons simultaneously for 780 sec, and finally by 1.0 MeV electrons for 780 sec with the HVEM-Tandem Facility in Argonne National Laboratory. The calculated damage rate by 1.5 MeV Kr{sup +} ions was 5.8 {times} 10{sup {minus}4} dpa/s, and that by 1.0 MeV electrons was 1 {times} 10{sup {minus}4} dpa/s. The growth rate of a dislocation loop located at the center of the specimen was 7 {times} 10{sup {minus}3} nm/s for the Kr{sup +} ion irradiation, 4 {times} 10{sup {minus}2} nm/s for the simultaneous Kr{sup +} and electron irradiation, and (2--3) {times} 10{sup {minus}2} nm/s for the electron irradiation. This implies that the electron irradiation is about 19 times more effective in the growth of radiation-induced dislocation loops than the Kr{sup +} ion irradiation. The dislocation loop growth rate under the simultaneous Kr{sup +} and electron irradiation is higher than the sum of the growth rates under the individual Kr{sup +} and electron …
Date:
October 1, 1991
Creator:
Kimoto, T. (National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)); Allen, C.W. & Rehn, L.E. (Argonne National Lab., IL (United States))
System:
The UNT Digital Library
Applications of concrete polymer materials for the rehabilitation of bridge decks
The rapid deterioration of concrete bridge decks as a result of the increased use of deicing salts is one of the most severe problems facing the highway industry today. One possible solution to the problem is the use of concrete polymer materials. The materials of prime interest are polymer-impregnated concrete (PIC) and polymer concrete (PC), both of which have excellent durability and strength properties. Three potential applications: repair of deteriorated bridge decks, polymer impregnation of new bridge deck surfaces, and full impregnation of precast deck panels have been studied in laboratory and field tests and the results have been encouraging. These results and economic considerations are described.
Date:
October 1, 1977
Creator:
Kukacka, L. E.
System:
The UNT Digital Library