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A preliminary analysis of the APS crotch design

Description: A preliminary design analysis of the absorber plate of the proposed crotch for the APS bending magnet radiation is presented. Various design aspects including thermal and structural considerations, material selection, geometry, and cooling method are discussed and a number of recommendations are made.
Date: March 1, 1990
Creator: Khounsary, A.M.
Partner: UNT Libraries Government Documents Department

Absorption of laser light in overdense plasmas by sheath inverse bremsstrahlung

Description: The original sheath inverse bremsstrahlung model [P. J. Catto and R. M. More, 1977] is modified by including the vxB term in the equation of motion. It is shown that the present results axe significantly different from those derived without the vxB term. The vxB term is also important in interpreting the absorption mechanism. If the vxB term were neglected, the absorption of the light would be incorrectly interpreted as an increase in the transverse electron temperature. This would violate the conservation of the transverse components of the canonical momentum, in the case of a normally incident laser light. It is also shown that both the sheath inverse bremsstrahlung and the anomalous skin effect are limiting cases of the same collisionless absorption mechanism. Finally, results from PIC plasma simulations are compared with the absorption coefficient calculated from the linear theory.
Date: November 1, 1994
Creator: Yang, T.Y.B.; Kruer, W.L. & More, R.M.
Partner: UNT Libraries Government Documents Department

Target and collection optimization for muon colliders

Description: To achieve adequate luminosity in a muon collider it is necessary to produce and collect large numbers of muons. The basic method used in this paper follows closely a proposed scheme which starts with a proton beam impinging on a thick target ({approximately} one interaction length) followed by a long solenoid which collects muons resulting mainly from pion decay. Production and collection of pions and their decay muons must be optimized while keeping in mind limitations of target integrity and of the technology of magnets and cavities. Results of extensive simulations for 8 GeV protons on various targets and with various collection schemes are reported. Besides muon yields results include-energy deposition in target and solenoid to address cooling requirements for these systems. Target composition, diameter, and length are varied in this study as well as the configuration and field strengths of the solenoid channel. A curved solenoid field is introduced to separate positive and negative pions within a few meters of the target. This permits each to be placed in separate RF buckets for acceleration which effectively doubles the number of muons per bunch available for collisions and increases the luminosity fourfold.
Date: January 10, 1996
Creator: Mokhov, N.V.; Noble, R.J. & Van Ginneken, A.
Partner: UNT Libraries Government Documents Department

Energy Absorption in Chopped Carbon Fiber Compression Molded Composites

Description: In passenger vehicles the ability to absorb energy due to impact and be survivable for the occupant is called the ''crashworthiness'' of the structure. To identify and quantify the energy absorbing mechanisms in candidate automotive composite materials, test methodologies were developed for conducting progressive crush tests on composite plate specimens. The test method development and experimental set-up focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. Quasi-static progressive crush tests were performed on composite plates manufactured from chopped carbon fiber with an epoxy resin system using compression molding techniques. The carbon fiber was Toray T700 and the epoxy resin was YLA RS-35. The effect of various material and test parameters on energy absorption was evaluated by varying the following parameters during testing: fiber volume fraction, fiber length, fiber tow size, specimen width, profile radius, and profile constraint condition. It was demonstrated during testing that the use of a roller constraint directed the crushing process and the load deflection curves were similar to progressive crushing of tubes. Of all the parameters evaluated, the fiber length appeared to be the most critical material parameter, with shorter fibers having a higher specific energy absorption than longer fibers. The combination of material parameters that yielded the highest energy absorbing material was identified.
Date: July 20, 2001
Creator: Starbuck, J.M.
Partner: UNT Libraries Government Documents Department

Feasibility of High Yield / High Gain NIF Capsules

Description: Our original ignition ''point designs'' (circa 1992) for the National Ignition Facility (NIF) were made energetically conservative to provide margin for uncertainties in laser absorption, x-ray conversion efficiency and hohlraum-capsule coupling. Since that time, extensive experiments on Nova and Omega and their related analysis indicate that NIF coupling efficiency may be almost ''as good as we could hope for''. Given close agreement between experiment and theory/modeling, we can credibly explore target enhancements which couple more of NIF's energy to an ignition capsule. We find that 3-4X increases in absorbed capsule energy appear possible, providing a potentially more robust target and {approx}10X increase in capsule yield.
Date: December 6, 1999
Creator: Suter, L.; Rothenberg, J.; Munro, D.; Van Wonterghem, B.; Haan, S. & Lindl, J.
Partner: UNT Libraries Government Documents Department

Mechanical properties and energy absorption characteristics of a polyurethane foam

Description: Tension, compression and impact properties of a polyurethane encapsulant foam have been measured as a function of foam density. Significant differences in the behavior of the foam were observed depending on the mode of testing. Over the range of densities examined, both the modulus and the elastic collapse stress of the foam exhibited power-law dependencies with respect to density. The power-law relationship for the modulus was the same for both tension and compression testing and is explained in terms of the elastic compliance of the cellular structure of the foam using a simple geometric model. Euler buckling is used to rationalize the density dependence of the collapse stress. Neither tension nor compression testing yielded realistic measurements of energy absorption (toughness). In the former case, the energy absorption characteristics of the foam were severely limited due to the inherent lack of tensile ductility. In the latter case, the absence of a failure mechanism led to arbitrary measures of energy absorption that were not indicative of true material properties. Only impact testing revealed an intrinsic limitation in the toughness characteristics of the material with respect to foam density. The results suggest that dynamic testing should be used when assessing the shock mitigating qualities of a foam.
Date: March 1, 1997
Creator: Goods, S.H.; Neuschwanger, C.L.; Henderson, C. & Skala, D.M.
Partner: UNT Libraries Government Documents Department

Magnetotunneling absorption in double quantum wells

Description: Tunneling absorption is calculated in weakly coupled n-type asymmetric double quantum wells in an in-plane magnetic field using a linear response theory. Photon-assisted tunneling occurs between the ground sublevels of the quantum wells. We show that the absorption threshold, the resonance energy of absorption, and the linewidth depend sensitively on the magnetic field and the temperature.
Date: June 1, 1996
Creator: Lyo, S.K.
Partner: UNT Libraries Government Documents Department


Description: To one whose responsibility it is to make evaluations of the degree of hazard existing in the radiation field of a nuclear accelerator or a nuclear reactor, the valid estimate of the contribution of neutrons to such a field is of considerable importance. The degree of difficulty of such a measurement depends strongly upon the information desired - whether (1) simply the presence of 'slow' and 'fast' neutrons in significant numbers is in question, or (2) a measure of flux densities within known energy intervals is required, or (3) a direct estimate of the specific rate of energy absorption due to neutron-produced effects in a given medium is desired. The importance of securing trustworthy estimates of the neutron field can be appreciated by recalling that the biological damage due to a given amount of ionization produced in biological tissue by effects due to neutrons is estimated to be several times the damage due to a similar amount of ionization produced by X-rays or gamma rays. This 'relative biological effectiveness' must be evaluated by carefully controlled animal experiments. Its value appears to range from about 2.5 for slow neutrons to abount 10 for fast and high energy neutrons. Of course the value obtained may also be a function of the particular biological variable under observations, and from some experiments a value as high as 20 for fast neutrons may be indicated.
Date: January 11, 1952
Creator: Moyer, B.J.
Partner: UNT Libraries Government Documents Department

Monte Carlo calculations of track structures

Description: In the study of radiation effects in matter, a knowledge of the spatial distribution of secondary products and of energy deposited is important. For charged particles heavier than electrons, energy is deposited along an almost straight track which can be seen in photographic emulsions or cloud chambers. The initial effect of the energy deposition is the production of clouds of collectively excited electrons (``plasmons``), ions and secondary electrons (``delta rays`` which in turn produce plasmons etc.) We describe the spatial pattern of energy deposited and new species produced as the track structure. The discussion presented here is only concerned with the initial track structure; the subsequent fate of the products is discussed in other papers of this conference. 6 refs., 2 figs.
Date: December 31, 1995
Creator: Bichsel, H.
Partner: UNT Libraries Government Documents Department

A grey {gamma}-ray transfer procedure for supernovae

Description: The {gamma}-ray transfer in supernovae for the purposes of energy deposition in the ejecta can be approximated as grey radiative transfer using mean opacities. In past work there is a single pure absorption mean opacity which is a free parameter. Accurate results can be obtained by varying this mean opacity to fit the results of more accurate procedures. In this paper, the authors present a grey {gamma}-ray transfer procedure for energy deposition in which there are multiple mean opacities that are not free parameters and that have both absorption and scattering components. This procedure is based on a local-state (LS) approximation, and so they call it the LS grey {gamma}-ray transfer procedure or LS procedure for short.
Date: December 1, 1997
Creator: Jeffery, D.J.
Partner: UNT Libraries Government Documents Department


Description: Beam-induced radiation effects have been simulated for 20 and 50 GeV muon storage rings designed for a Neutrino Factory. It is shown that by appropriately shielding the superconducting magnets, quench stability, acceptable dynamic heat loads, and low residual dose rates can be achieved. Alternatively, if a specially-designed skew focusing magnet without superconducting coils on the magnet's mid-plane is used, then the energy is deposited preferentially in the warm iron yoke or outer cryostat layers and internal shielding may not be required. In addition to the component irradiation analysis, shielding studies have been performed. Calculations of the external radiation were done for both designs but the internal energy deposition calculations for the 20 GeV Study-2 lattice are still in progress.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department


Description: We report initial results of exposing low-Z solid and high-Z liquid targets to 150-ns, 4 x 10{sup 12} proton pulses with spot sizes on the order of 1 to 2 mm. The energy deposition density approached 100 J/g. Diagnostics included fiberoptic strain sensors on the solid target and high-speed photography of the liquid targets. This work is part of the R and D program of the Neutrino Factory and Muon Collider Collaboration.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

Magnetized Target Fusion (MTF): Principles, Status, and International Collaboration

Description: Magnetized target fusion (MTF) is an approach to thermonuclear fusion that is intermediate between the two extremes of inertial and magnetic confinement. Target plasma preparation is followed by compression to fusion conditions. The use of a magnetic field to reduce electron thermal conduction and potentially enhance DT alpha energy deposition allows the compression rate to be drastically reduced relative to that for inertial confinement fusion. This leads to compact systems with target driver power and intensity requirements that are orders of magnitude lower than for ICF. A liner on plasma experiment has been proposed to provide a firm proof of principle for MTF.
Date: November 16, 1998
Creator: Kirkpatrick, R.C.
Partner: UNT Libraries Government Documents Department

Modeling and design of energy concentrating laser weld joints

Description: The application of lasers for welding and joining has increased steadily over the past decade with the advent of high powered industrial laser systems. Attributes such as high energy density and precise focusing allow high speed processing of precision assemblies. Other characteristics of the process such as poor coupling of energy due to highly reflective materials and instabilities associated with deep penetration keyhole mode welding remain as process limitations and challenges to be overcome. Reflective loss of laser energy impinging on metal surfaces can in some cases exceed ninety five percent, thus making the process extremely inefficient. Enhanced coupling of the laser beam can occur when high energy densities approach the vaporization point of the materials and form a keyhole feature which can trap laser energy and enhance melting and process efficiency. The extreme temperature, pressure and fluid flow dynamics of the keyhole make control of the process difficult in this melting regime. The authors design and model weld joints which through reflective propagation and concentration of the laser beam energy significantly enhance the melting process and weld morphology. A three dimensional computer based geometric optical model is used to describe the key laser parameters and joint geometry. Ray tracing is used to compute the location and intensity of energy absorption within the weld joint. Comparison with experimentation shows good correlation of energy concentration within the model to actual weld profiles. The effect of energy concentration within various joint geometry is described. This method for extending the design of the laser system to include the weld joint allows the evaluation and selection of laser parameters such as lens and focal position for process optimization. The design of narrow gap joints which function as energy concentrators is described. The enhanced laser welding of aluminum without keyhole formation has been demonstrated.
Date: April 1997
Creator: Milewski, J. O. & Sklar, E.
Partner: UNT Libraries Government Documents Department


Description: In this report we will show some new Q related seismic attributes on the Burlington-Seitel data set. One example will be called Energy Absorption Attribute (EAA) and is based on a spectral analysis. The EAA algorithm is designed to detect a sudden increase in the rate of exponential decay in the relatively higher frequency portion of the spectrum. In addition we will show results from a hybrid attribute that combines attenuation with relative acoustic impedance to give a better indication of commercial gas saturation.
Date: April 1, 2003
Creator: Walls, Joel; Taner, M.T.; Derzhi, Naum; Mavko, Gary & Dvorkin, Jack
Partner: UNT Libraries Government Documents Department


Description: In this report we will show the fundamental concepts of two different methods to compute seismic energy absorption. The first methods gives and absolute value of Q and is based on computation with minimum phase operators. The second method gives a relative energy loss compared to a background trend. This method is a rapid, qualitative indicator of anomalous absorption and can be combined with other attributes such as band limited acoustic impedance to indicate areas of likely gas saturation.
Date: October 1, 2003
Creator: Walls, Joel; Taner, M.T.; Derzhi, Naum; Mavko, Gary & Dvorkin, Jack
Partner: UNT Libraries Government Documents Department

A Preliminary Report on X-Ray Photoabsorption Coefficients andAtomic Scattering Factors for 92 Elements in the 10-10,000 eVRegion

Description: Based on currently available photoabsorption measurements and recent theoretical calculations by Doolen and Liberman (Physica Scripta 36, 77 (1987)), a revised (from ADNDT 27, 1 (1982)) best-fit determination of the photoabsorption cross sections is presented here for the elements Z=1 to Z=92 in the 10-10,000 eV range. The photoabsorption data used include those described in the Lockheed and DOE listings of research abstracts for the past ten years and those which have been recently added to the comprehensive NBS Measured Data Base (NBSIR 86-3461, Hubbell et al.). The best-fit curves are compared with both the compilation of measurements and the calculations by Doolen and Liberman. Using the photoabsorption curves, the atomic scattering factors have been calculated for the energy range 50-10,000 eV and are also presented in this report.
Date: November 1, 1988
Creator: Henke, B.L.; Davis, J.C.; Gullikson, E.M. & Perera, R.C.C.
Partner: UNT Libraries Government Documents Department

Response to Absorber-Focus Coil Preliminary Safety ReviewPanel

Description: In this document we provide responses to the various issues raised in the report of the Preliminary Safety Review Panel (see http://mice.iit.edu/mnp/MICE0069.pdf). In some cases we have made design changes in response to the Panels suggestions. In other cases, we have chosen not to do so. In a few cases, we indicate our plans, although the tasks have not yet been completed. For simplicity, the responses are organized along the same lines as those of the Panel Report.
Date: July 21, 2004
Creator: Barr, Giles; Baynham, Elwyn; Black, Edgar; Bradshaw, Tom; Cummings, Mary Anne; Green, Michael A. et al.
Partner: UNT Libraries Government Documents Department

Laser fusion monthly, February 1981

Description: This report is divided into the following sections: (1) facility reports (Argus and Shiva); (2) Nova project; and (3) fusion experiments. In the Fusion Experiments section of this report, the author describes the results of a series of experiments on Shiva which further the understanding of the production and transport of suprathermal electrons. He found that of the suprathermal electrons which strike a laser irradiated disk target or which interact with the rear surface of a half Cairn hohlraum target, a significant fraction of these electrons orbit the target and strike the rear of the disk. These results have significant implications in the interpretation and modeling of the laser irradiated target experiments.
Date: February 1, 1981
Creator: Ahlstrom, H.G.
Partner: UNT Libraries Government Documents Department

Plasma enhanced RF power deposition on ICRF antennas in Tore Supra

Description: The dual-strap Tore Supra ICRF antennas have been very successful in coupling high power fluxes > 16 MW/m2 to the plasma. In many cases it has been found that the power is limited not by the voltages and currents that can be sustained on antenna components, but rather by localized increases in antenna surface temperatures which are correlated with increased impurity levels. Hot spots have been observed using an IR imaging system with peak temperatures as high as 1,100 C after 2 s, and as little as 1.5 MW power coupled from a single launcher. The maximum temperature observed is highly dependent on antenna phasing, and is lowest with dipole ({pi}) phasing of the relative antenna currents. Both toroidal and poloidal asymmetries in hot spot distribution have been observed, and interestingly, the toroidal asymmetry has been found to vary when the phase is changed from +{pi}/2 to {minus}{pi}/2. Significant differences in the temperature profiles have been seen on the two types of Faraday shield in use, which appears to be related to the fact that one type has a recessed center septum between straps while the other does not. In some cases, the peak temperature has been observed to increase as the antenna/plasma gap is increased, while the peak remains in the same location. This behavior suggests that voltages generated by currents flowing in the Faraday shield structure itself may play a role in generating potentials responsible for the hot spots, in addition to rf fields in the plasma. In this paper data on antenna surface heating and loading data as a function of plasma density, antenna/plasma gap, and phasing will be presented. Calculations from the RANT3D electromagnetic code together with bench measurements of electric fields near the antenna surface will also be shown.
Date: August 1, 1997
Creator: Goulding, R.H.; Harris, J.H.; Carter, M.D.; Hoffman, D.J.; Hogan, J.T.; Ryan, P.M. et al.
Partner: UNT Libraries Government Documents Department

Co-counter asymmetry in fast wave heating and current drive and profile control in NSTX

Description: In this paper, full-wave ICRF coupling models are applied to understand the difference in plasma response when antenna arrays are phased to drive currents co and counter to the plasma current. The source of this difference lies in the natural up-down asymmetry of the antenna`s radiated power spectrum caused by Hall currents. When a poloidal field is applied, this up-down asymmetry acquires a toroidal component. The result is that plasma absorption (i.e., antenna loading) is shifted or skewed toward the co-current drive direction, independent of the direction of the magnetic field. When waves are launched to drive current counter to the plasma current, electron heating and current profiles are more peaked on axis, and this peaking becomes more pronounced at lower toroidal magnetic fields.
Date: August 1, 1997
Creator: Jaeger, E.F.; Carter, M.D.; Berry, L.A.; Batchelor, D.B.; Ryan, P.M.; Forest, C.B. et al.
Partner: UNT Libraries Government Documents Department

Examination of the CLIC drive beam pipe design for thermal distortion caused by distributed beam line

Description: Beam transport programs are widely used to estimate the distribution of power deposited in accelerator structures by particle beams, either intentionally as for targets or beam dumps or accidentally owing the beam loss incidents. While this is usually adequate for considerations of radiation safety, it does not reveal the expected temperature rise and its effect on structural integrity. To find this, thermal diffusion must be taken into account, requiring another step in the analysis. The method that has been proposed is to use the output of a transport program, perhaps modified, as input for a finite element analysis program that can solve the thermal diffusion equation. At Cern, the design of the CLIC beam pipe has been treated in this fashion. The power distribution produced in the walls by a distributed beam loss was found according to the widely-used electron shower code EGS4. The distribution of power density was then used to form the input for the finite element analysis pro gram ANSYS, which was able to find the expected temperature rise and the resulting thermal distortion. As a result of these studies, the beam pipe design can be modified to include features that will counteract such distortion.
Date: January 1, 1997
Creator: Johnson, C. & Kloeppel, K.
Partner: UNT Libraries Government Documents Department