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0-G experiments with advanced ceramic fabric wick structures: Both Air Force and NASA future spacecraft thermal management needs span the temperature range from cryogenic to liquid metals. Many of these needs are changing and not well defined and will remain so until goals, technology, and missions converge. Nevertheless, it is certain that high-temperature (> 800 K) and medium-temperature (about 450 K) radiator systems will have to be developed that offer significant improvements over current designs. This paper discusses experiments performed in the lower temperature regime as part of a comprehensive advanced ceramic fabric (ACF) heat pipe development program. These experiments encompassed wicking tests with various ceramic fabric samples, and heat transfer tests with a 1-m long prototype ACF water heat pipe. A prototype ceramic fabric/titanium water heat pipe has been constructed and tested; it transported up to 60 W of power at about 390 K. Startup and operation both with and against gravity examined. Wick testing was begun to aid in the design and construction of an improved prototype heat pipe, with a 38-{mu}m stainless steel linear covered by a biaxially-braided Nextel (trademark of the 3M Co., St. Paul, Minnesota) sleeve that is approximately 300-{mu}m thick. Wick testing took place in 1-g; limited testing in 0-g was initiated, and results to date suggest that in 0-g, wick performance improves over that in 1-g.
2-D and 3-D computations of curved accelerator magnets: In order to save computer memory, a long accelerator magnet may be computed by treating the long central region and the end regions separately. The dipole magnets for the injector synchrotron of the Advanced Photon Source (APS), now under construction at Argonne National Laboratory (ANL), employ magnet iron consisting of parallel laminations, stacked with a uniform radius of curvature of 33.379 m. Laplace's equation for the magnetic scalar potential has a different form for a straight magnet (x-y coordinates), a magnet with surfaces curved about a common center (r-{theta} coordinates), and a magnet with parallel laminations like the APS injector dipole. Yet pseudo 2-D computations for the three geometries give basically identical results, even for a much more strongly curved magnet. Hence 2-D (x-y) computations of the central region and 3-D computations of the end regions can be combined to determine the overall magnetic behavior of the magnets. 1 ref., 6 figs.
A 2-GHz Rectangular Corrugated Horn: We have designed, constructed and tested a large, rectangular horn antenna with a center frequency of 2.0 GHz, corrugated on the E-plane walls, made out of aluminum sheet. A new technique has been developed to solder thin aluminum strips onto the back plane to form the corrugations. The radiation beam pattern shows half-power beamwidths of 12{sup 0} and 14{sup 0} in the H and E planes respectively, and side lobe response below -40 dB at angles greater than 50{sup 0} from horn axis. The measured return loss is less than -20 dB (VSWR < 1.22) between 1.7 and 2.3 GHz; insertion loss is less than 0.15 dB.
A 3-D adaptive mesh refinement algorithm for multimaterial gas dynamics: Adaptive Mesh Refinement (AMR) in conjunction with high order upwind finite difference methods has been used effectively on a variety of problems. In this paper we discuss an implementation of an AMR finite difference method that solves the equations of gas dynamics with two material species in three dimensions. An equation for the evolution of volume fractions augments the gas dynamics system. The material interface is preserved and tracked from the volume fractions using a piecewise linear reconstruction technique. 14 refs., 4 figs.
A 10,000 A 1000 VDC solid state dump switch: The superconducting magnet test program at Fermilab requires a switch, called a dump switch, rated 10,000 A, 1000 Vdc, which must be able to continuously carry rated current. A dump resistor rated 2 MJoules, is connected in parallel with the switch contacts and dissipates the stored energy from a magnet when the switch opens. The required switch opening time is 250 {mu}sec maximum after detection of a fault or a trip command. A successful switch can be constructed from six parallel inverter type Silicon Controlled Rectifiers (SCR's) which each carry their share of the load current. These run SCR's are mounted at watercooled heatsinks and are commutated off from stored energy in capacitors. Each parallel SCR is connected in series with a 1 m{Omega} watercooled resistor to assure dc current sharing and turn on. A description of the control and construction of the switch is presented. 6 figs.
30-60 MHz FWCD system on DIII-D: Power division, phase control and tuning for a four-element antenna array: The 2 MW Fast Wave Current Drive system on DIII-D is intended to provide a near-term demonstration of up to 0.3 MA of current driven by the fast wave. The system used to drive the four element phased antenna array which produces the required directional spectrum is presented. This system must be able to cope with strong coupling between antenna elements and the time-varying plasma load seen by the antennas. Computer modelling shows that this system should be able to maintain a directional spectrum at full power under most anticipated load conditions. 5 refs., 1 fig.
30-60 MHz FWCD system on DIII-D: Power division, phase control and tuning for a four-element antenna array: The 2 MW Fast Wave Current Drive system on DIII-D is intended to provide a near-term demonstration of up to 0.3 MA of current driven by the fast wave. The system used to drive the four element phased antenna array which produces the required directional spectrum is presented. This system must be able to cope with strong coupling between antenna elements and the time-varying plasma load seen by the antennas. Computer modelling shows that this system should be able to maintain a directional spectrum at full power under most anticipated load conditions. 5 refs., 1 fig.
40- angstrom FEL designs for the PEP storage ring: We explore the use of the 2.2-km PEP storage ring at SLAC to drive a 40-{Angstrom} free-electron laser in the self-amplified spontaneous emission configuration. Various combinations for electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67-m, hybrid permanent-magnet undulator in a ring bypass. A 100-m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6-m, Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. 35 refs., 4 figs., 1 tab.
40-{angstrom} FEL designs for the PEP storage ring: We explore the use of the 2.2-km PEP storage ring at SLAC to drive a 40-{Angstrom} free-electron laser in the self-amplified spontaneous emission configuration. Various combinations for electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67-m, hybrid permanent-magnet undulator in a ring bypass. A 100-m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6-m, Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. 35 refs., 4 figs., 1 tab.
100 MW klystron development at SLAC: A klystron designed to operate at 11.4 GHz and 440 kV is presently SLAC's strongest rf power source candidate for the Next Linear Collider. It is expected to provide 100 MW of rf power with a pulse width of 1 microsecond. Many of the conventional tube technologies are being pushed to their limits. High electron beam power densities, rf electric gradients in cavity gaps and stresses on the ceramic rf output windows are among the most severe problems to be dealt with. This paper describes progress in the development of this device including results from single and double gap output cavities and various styles of rf output windows. 6 refs., 3 figs., 1 tab.
110 GHz ECH on DIII-D: System overview and initial operation: A new high power electron cyclotron heating (ECH) system has been introduced on D3-D. This system is designed to operate at 110 GHz with a total output power of 2 MW. The system consists of four Varian VGT-8011 gyrotrons, (output power of 500 kW), and their associated support equipment. All components have been designed for up to a 10 second pulse duration. The 110 GHz system is intended to further progress in rf current drive experiments on D3-D when used in conjunction with the existing 60 GHz ECH (1.6 MW), and the 30--60 MHz ICH (2 MW) systems. H-mode physics, plasma stabilization experiments and transport studies are also to be conducted at 110 GHz. The present system design philosophy was based on experience gained from the existing 60 GHz ECH system. The consequences of these design decisions will be addressed as will the actual performance of various 110 GHz components.
110 GHz ECH on DIII-D: System overview and initial operation: A new high power electron cyclotron heating (ECH) system has been introduced on D3-D. This system is designed to operate at 110 GHz with a total output power of 2 MW. The system consists of four Varian VGT-8011 gyrotrons, (output power of 500 kW), and their associated support equipment. All components have been designed for up to a 10 second pulse duration. The 110 GHz system is intended to further progress in rf current drive experiments on D3-D when used in conjunction with the existing 60 GHz ECH (1.6 MW), and the 30--60 MHz ICH (2 MW) systems. H-mode physics, plasma stabilization experiments and transport studies are also to be conducted at 110 GHz. The present system design philosophy was based on experience gained from the existing 60 GHz ECH system. The consequences of these design decisions will be addressed as will the actual performance of various 110 GHz components.
350 MW(t) MHTGR preassembly and modularization: The Modular High Temperature Gas Cooled Reactor (MHTGR) provides a safe and economical nuclear power option for the world's electrical generation needs by the turn of the century. The proposed MHTGR plant is composed of four 350 MW(t) prismatic core reactor modules, coupled to a 2(2 {times} 1) turbine generator producing a net plant electrical output of 538 MW(e). Each of the four reactor module is located in a below-ground level concrete silo, and consists of a reactor vessel and a steam generator vessel interconnected by a cross duct vessel. The modules, along with the service buildings, are contained within a Nuclear Island (NI). The turbine generators and power generation facilities are in the non-nuclear Energy Conversion Area (ECA). The MHTGR design reduces cost and improves schedule by maximizing shop fabrication, minimizing field fit up of the Reactor Internals components and modularizing the NI ECA facilities. 3 refs., 6 figs., 2 tabs.
The 1990 Clean Air Act Amendments and the Great Lakes Economy: Challenges and Opportunities: This paper deals with the market for SO{sub 2} emission allowances over time and electric utility compliance choices. For currently high emitting plants ( > 2.5 lb SO{sub 2}/MMBtu), the 1990 Clean Air Act Amendments (CAAA) provide for about twice as many SO{sub 2} allowances to be issued per year in Phase 1 (1995--1999) than in Phase 2. Also, considering the scrubber incentives in Phase 1, there is likely to be substantial emission banking for use in Phase 2. Allowance prices are expected to increase over time at a rate less than the return on alternative investments, so utilities which are risk neutral or other potential speculators in the allowance market are not expected to bank allowances. The allowances will be banked by risk averse utilities or the utilities may buy forward contracts for SO{sub 2} allowances. However, speculators may play an important role by selling forward contracts for SO{sub 2} allowances to the risk averse utilities. The Argonne Utility Simulation Model (ARGUS) is being revised to incorporate the provisions of the CAAA acid rain title and to simulate SO{sub 2} allowance prices, compliance choices, capacity expansion, system dispatch, fuel use, and emissions. The revised model (ARGUS2) incorporates unit-level performance data and can incorporate unit-specific compliance decisions when these are known. The model has been designed for convenience in analyzing alternatives scenarios (demand growth rates, technology mix, economic parameters, etc). 1 ref., 5 figs.
1991 Conference summary on computing in high energy physics: The papers presented at the Conference cover a wide range of important issues in software engineering and management. They indicate a trend toward more use of commercial systems and standards. This trend will likely have a significant influence on plans for future systems.
1991 US-Japan workshop on Nuclear Fusion in Dense Plasmas: The scientific areas covered at the Workshop may be classified into the following subfields: (1) basic theory of dense plasma physics and its interface with atomic physics and nuclear physics; (2) physics of dense z-pinches, ICF plasmas etc; (3) stellar interior plasmas; (4) cold fusion; and (5) other dense plasmas.
A 1K Shadow RAM for circumvention applications: A 1K bit Shadow RAM has been developed for storage of critical data in a high transient radiation environment. The circuit includes a 1K bit (128 {times} 8) static RAM with two non-volatile (NV) shadows. The NV shadows are used to back-up the data in the static RAM allowing the circuit to be powered down during transient radiation without losing critical data. This paper will describe the circuit's operation and characterization results.
3d Image Reconstruction for PET by Multi-Slice Rebinning and Axial Filtering: Two different approaches are used at present to reconstruct from 3D coincidence data in PET. We refer to these approaches as the single-slice rebinning approach and the fully-3D approach. The single-slice rebinning approach involves geometrical approximations, but it requires the least possible amount of computation. Fully-3D reconstruction algorithms, both iterative and non-iterative, do not make such approximations, but require much more computation. Multi-slice rebinning with axial filtering is a new approach which attempts to achieve the geometrical accuracy of the fully-3D approach with the simplicity and modest amount of computation of the single-slice rebinning approach. The first step (multi-slice rebinning) involves rebinning of coincidence lines into a stack of 2D sinograms, where multiple sinograms are incremented for each oblique coincidence line. This operation is followed by an axial filtering operation, either before or after slice-by-slice reconstruction, to reduce the blurring in the axial direction. Tests with simulated and experimental data indicate that the new method has better geometrical accuracy than single-slice rebinning, at the cost of only a modest increase in computation. 11 refs.
3d Image Reconstruction for PET by Multi-Slice Rebinning and Axial Filtering. [Positron Emission Tomography (Pet)]: Two different approaches are used at present to reconstruct from 3D coincidence data in PET. We refer to these approaches as the single-slice rebinning approach and the fully-3D approach. The single-slice rebinning approach involves geometrical approximations, but it requires the least possible amount of computation. Fully-3D reconstruction algorithms, both iterative and non-iterative, do not make such approximations, but require much more computation. Multi-slice rebinning with axial filtering is a new approach which attempts to achieve the geometrical accuracy of the fully-3D approach with the simplicity and modest amount of computation of the single-slice rebinning approach. The first step (multi-slice rebinning) involves rebinning of coincidence lines into a stack of 2D sinograms, where multiple sinograms are incremented for each oblique coincidence line. This operation is followed by an axial filtering operation, either before or after slice-by-slice reconstruction, to reduce the blurring in the axial direction. Tests with simulated and experimental data indicate that the new method has better geometrical accuracy than single-slice rebinning, at the cost of only a modest increase in computation. 11 refs.
3D numerical thermal stress analysis of the high power target for the SLC Positron Source: The volumetrically nonuniform power deposition of the incident 33 GeV electron beam in the SLC Positron Source Target is hypothesized to be the most likely cause target failure. The resultant pulsed temperature distributions are known to generate complicated stress fields with no known closed-form analytical solution. 3D finite element analyses of these temperature distributions and associated thermal stress fields in the new High Power Target are described here. Operational guidelines based on the results of these analyses combined with assumptions made about the fatigue characteristics of the exotic target material are proposed. 6 refs., 4 figs.
3D simulations of axially confined heavy ion beams in round and square pipes: We have been using the 3d PIC code WARP6 to model the behavior of beams in a heavy ion induction accelerator; such linacs are candidates for an ICF driver. Improvements have been added to the code to model an axially confined beam using comoving axial electric fields to simulate the confining ears'' applied to the accelerating pulses in a real system. We have also added a facility for modeling a beam in a round pipe, applying a capacity matrix to each axial Fourier mode in turn. These additions are described along with results, such as the effect of pipe shape on the beam quality degradation from quadrupole misalignments. 5 refs., 6 figs., 1 tab.
3D vadose zone modeling using geostatistical inferences: In developing a 3D model of the 600 ft thick interbedded basalt and sediment complex that constitutes the vadose zone at the Radioactive Waste Management Complex (RWMC) at the Idaho National Engineering Laboratory (INEL) geostatistical data were captured for 12--15 parameters (e.g. permeability, porosity, saturation, etc. and flow height, flow width, flow internal zonation, etc.). This two scale data set was generated from studies of subsurface core and geophysical log suites at RWMC and from surface outcrop exposures located at the Box Canyon of the Big Lost River and from Hell's Half Acre lava field all located in the general RWMC area. Based on these currently available data, it is possible to build a 3D stochastic model that utilizes: cumulative distribution functions obtained from the geostatistical data; backstripping and rebuilding of stratigraphic units; an expert'' system that incorporates rules based on expert geologic analysis and experimentally derived geostatistics for providing: (a) a structural and isopach map of each layer, (b) a realization of the flow geometry of each basalt flow unit, and (c) a realization of the internal flow parameters (eg permeability, porosity, and saturation) for each flow. 10 refs., 4 figs., 1 tab.
The 40th AAAS Gordon Conference on nuclear chemistry: I am pleased to speak at the Fortieth Gordon Conference on Nuclear Chemistry. I served as Chairman of the first Gordon Conference on Nuclear Chemistry held June 23--27, 1952, at New Hampton, New Hampshire. In my remarks, during which I shall quote from my journal, I shall describe some of the background leading up to the first Gordon Conference on Nuclear Chemistry and my attendance at the first seven Gordon Conferences during the period 1952 through 1958. I shall also quote my description of my appearance as the featured speaker at the Silver Anniversary of the Gordon Research Conferences on December 27, 1956 held at the Commodore Hotel in New York City. I shall begin with reference to my participation in the predecessor to the Gordon Conferences, the Gibson Island Research Conferences 45 years ago, on Thursday, June 20, 1946, as a speaker. This was 15 years after the start of these conferences in 1931. Neil Gordon played a leading role in these conferences, which were named (in 1948) in his honor -- the Gordon Research Conferences -- soon after they were moved to Colby Junior College, New London, New Hampshire in 1947. W. George Parks became Director in 1947, Alexander Cruickshank became Assistant Director in 1947 and Director in 1968.
7th DOE workshop on computer-aided engineering: This report contains the abstracts and the program for the 7th DOE workshop on Computer-Aided Engineering. (LSP)
7th international symposium on photosynthetic prokaryotes: This book contains the abstracts of all the presentations made either in oral or poster form, at the VII International Symposium on Photosynthetic Prokaryotes.
7th international symposium on photosynthetic prokaryotes. Abstracts: This book contains the abstracts of all the presentations made either in oral or poster form, at the VII International Symposium on Photosynthetic Prokaryotes.
Ab initio calculations on collisions of low energy electrons with polyatomic molecules: The Kohn variational method is one of simplest, and oldest, techniques for performing scattering calculations. Nevertheless, a number of formal problems, as well as practical difficulties associated with the computation of certain required matrix elements, delayed its application to electron--molecule scattering problems for many years. This paper will describe the recent theoretical and computational developments that have made the complex'' Kohn variational method a practical tool for carrying out calculations of low energy electron--molecule scattering. Recent calculations on a number of target molecules will also be summarized. 41 refs., 7 figs.
Ab initio cluster studies of La₂CuO₄: In this paper we examine the properties of small cluster models of La{sub 2}CuO{sub 4}. In Section 2, the Madelung/Pauli background potential used to imbed the primary cluster and the basis sets used to expand the cluster wavefunction are discussed. Section 3 presents the results of calculations on CuO{sub 6} in which the optical absorption and the photoemission spectrum are examined. The calculation on CuO{sub 6} and our earlier work on larger clusters suggest that a single-band Pariser-Parr-Pople (PPP) model be developed. Therefore, in Section 4 the PPP model and extensions which relax the zero-differential-overlap (ZDO) approximation upon which it is based are reviewed. Calculations on the states of Cu{sub 2}O{sub 7} necessary to parameterize the PPP model are presented in Section 5 and compared with analogous calculations for Cu{sub 2}O{sub 11}. Section 6 discusses the problems associated with the direct ab initio determination of the anti-ferromagnetic exchange interaction, examines the magnitudes of the occupation-dependent hopping and direct exchange interactions which arise when the ZDO approximation is relaxed, and provides estimates of the uncertainties in the parameters due to electron correlation and polarization effects not recoverable with the present basis sets and finite clusters. A comparison of the parameters with those extracted from constrained LDF theory concludes Section 6. Finally, Section 7 summarizes the conclusions of this research.
Ablation gas dynamics of low-Z materials illuminated by soft x-rays: Though many of our results will have much greater generality, the main purpose of this paper is to provide a simple, accurate, physical theory of what happens when a Planckian spectrum of soft x-rays is incident on one side of the slab of initially cold, dense material, of small nuclear charge Z. Our approach will be to consider in some detail the idealized situation. A semi-infinite (x {le} 0) slab of initially cold (T < 300 K), dense ({rho} {approximately} 1 {minus} 10 g/cc), low-Z (Z < 5) material is suddenly subjected at time t = 0 and thereafter to radiation incoming from x = +{infinity} with a specific intensity in directions toward the slab that is Planckian, characterized by a black-body temperature, T{sub R} in the soft x-ray region.
Ablation of material by front surface spallation: Laser irradiation can be utilized to remove (i.e., ablate) material in a controlled manner by a hydrodynamic process, referred to as front surface spallation. In this process, a thin layer next to a free surface is heated to a level (below vaporization) so rapidly that it cannot undergo thermal expansion during laser heating. This generates a stress pulse, which propagates both inward and toward the free surface, with an initial amplitude that can be calculated using the Grueneisen coefficient. As the pulse reflects from the free surface, a tensile tail can develop of sufficient amplitude, exceeding the material strength, that a layer will be spalled off, taking much of the laser-deposited energy with it. To achieve spallation conditions, the laser wavelength, pulselength and fluence must be tailored to the absorption depth, Grueneisen coefficient, and spall strength. Hydrodynamic calculations and analytical modeling are presented to explain the process and illustrate conditions under which it should be expected to occur. Under some conditions, front surface spallation can have advantages over ablation by thermal vaporization, where residual temperatures are generally higher. 9 refs., 7 figs.
Absence of antiferromagnetic order in UBe sub 13: The linear magnetostriction ({lambda}{sub //} and {lambda}{sub //}) of a single-crystalline sample of the heavy-fermion compound UBe{sub 13} has been measured for fields B < 8 T (B{sub //}(100)) in the temperature interval 0.3 < T < 12 K. We find neither evidence for the antiferromagnetic order (T{sub N}=8.8 K) nor for the magnetostrictive oscillations, that were reported recently. Instead {lambda} varies proportional to B{sup 2} as expected for a normal paramagnetic metal. 8 refs., 3 figs.
Absorbing CAD system geometries into GEANT: The simulation community has for many years discussed the possibility of direct conversion of geometrical detector models from computer- aided design and engineering systems (CAD systems) to the simulation packages (which we shall assume means GEANT). This would allow fast and simultaneous optimization of the physics performance and structural integrity of detector designs. The benefit that this would offer is the avoidance of such problems as the late discovery of the rather thick cryostats in the D-Zero detector. Recent progress in the absorption of CAD geometries into GEANT models is reviewed, including descriptions of the additions to the I-DEAS solid modeller package developed for the EMPACT SSC proposal, the COGENT CAD-to-GEANT interpreter developed by Quantum Research Services, and the OCTAGON package for representing arbitrary shapes in GEANT. Likely future directions of development are described. 2 refs., 7 figs.
Absorption chillers: Part of the solution: Acid rain, ozone depletion, global warming, and implementation economics are considered as they relate to the advisability of expanding the application of absorption chillers. Introductory and background information are provided to put the discussion in the proper context. Then all four issues are discussed separately as they relate to absorption chillers. Acid rain and ozone depletion concerns, and implementation economics, are found to support the expanded use of absorption chillers. The global warming concern is found to be more of a gray area, but the areas of benefit correspond well with the conditions of greatest economic advantage. All things considered, absorption chillers are believed to be part of the environmental and economic solution. It is further believed that integrated resource planning (IRP) processes that consider electric and gas technologies on an equal footing would come to the same conclusion for many regions of the United States. 9 refs., 3 tabs.
Abstracts and research accomplishments of university coal research projects: The Principal Investigators of the grants supported by the University Coal Research Program were requested to submit abstracts and highlight accomplishments of their projects in time for distribution at a grantees conference. This book is a compilation of the material received in response to the request. Abstracts discuss the following area: coal science, coal surface science, reaction chemistry, advanced process concepts, engineering fundamentals and thermodynamics, environmental science.
Ac losses in YBa sub 2 Cu sub 3 O sub 7 and Bi sub 2 Sr sub 2 Ca sub 2 Ci sub 3 O sub 10 superconductors at power frequencies: Ac losses of sintered and melt-textured YBa{sub 2}Cu{sub 3}O{sub 7} bars and powder-in-a-tube processed Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes were measured at 4.2, 65, 70 and 77 K and at 15--180 Hz. In general, the results are well described by the critical state model for the ac losses. However, the losses for the Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes at 4.2 K exhibited significant contributions from the eddy currents in the Ag sheath.
Ac losses in YBa{sub 2}Cu{sub 3}O{sub 7} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Ci{sub 3}O{sub 10} superconductors at power frequencies: Ac losses of sintered and melt-textured YBa{sub 2}Cu{sub 3}O{sub 7} bars and powder-in-a-tube processed Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes were measured at 4.2, 65, 70 and 77 K and at 15--180 Hz. In general, the results are well described by the critical state model for the ac losses. However, the losses for the Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes at 4.2 K exhibited significant contributions from the eddy currents in the Ag sheath.
Accelerating field step-up transformer in wake-field accelerators: In the wake-field scheme of particle acceleration, a short, intense drive bunch of electrons passes through a slow-wave structure, leaving behind high rf power in its wake field. The axial accelerating electric field associated with the rf can be quite large, > 100 MeV/m, and is used to accelerate a much less intense witness'' beam to eventual energies > 1 TeV. The rf power is deposited predominantly in the fundamental mode of the structure, which, for dielectric-lined waveguide as used at Argonne, is the TM{sub 01} mode. In all likelihood on the field amplitude will be limited only by rf breakdown of the dielectric material, the limit of which is currently unknown in the short time duration, high frequency regime of wake-field acceleration operation. To obtain such strong electric fields with given wake-field rf power, the dimensions of the dielectric-lined waveguide have to be fairly small, OD of the order of a cm and ID of a few mm, and this gives rise to the generation of strong deflection modes with beam misalignment. While a scheme exists to damp such deflection modes on a bunch-to-bunch time scale, head-tail beam deflection could still be a problem and BNS damping as well as FODO focusing are incomplete cures. Presented here are details of a scheme by which the rf power is generated by in a large-diameter wake-field tube, where deflection mode generation by the intense drive beam is tolerable, and then fed into a small-diameter acceleration tube where the less intense witness beam is accelerated by the greatly enhanced axial electric field. The witness beam generates little deflection-mode power itself, even in the small acceleration tube, thus a final high-quality, high-energy electron beam is produced.
Accelerator and feedback control simulation using neural networks: Unlike present constant model feedback system, neural networks can adapt as the dynamics of the process changes with time. Using a process model, the Accelerator'' network is first trained to simulate the dynamics of the beam for a given beam line. This Accelerator'' network is then used to train a second Controller'' network which performs the control function. In simulation, the networks are used to adjust corrector magnetics to control the launch angle and position of the beam to keep it on the desired trajectory when the incoming beam is perturbed. 4 refs., 3 figs.
Accelerator and transport line survey and alignment: This paper summarizes the survey and alignment processes of accelerators and transport lines and discusses the propagation of errors associated with these processes. The major geodetic principles governing the survey and alignment measurement space are introduced and their relationship to a lattice coordinate system shown. The paper continues with a broad overview about the activities involved in the step sequence from initial absolute alignment to final smoothing. Emphasis is given to the relative alignment of components, in particular to the importance of incorporating methods to remove residual systematic effects in surveying and alignment operations. Various approaches to smoothing used at major laboratories are discussed. 47 refs., 19 figs., 1 tab.
Accelerator-driven neutron sources for fusion-materials testing: Several accelerator-driven neutron sources have been proposed for satisfying the requirements of a high-flux high-volume international fusion materials testing facility that could be built in the near future. This paper summarizes the features and projected performance for the three accelerator sources that are leading candidates for such a role and that are viewed by the International Energy Agency (IEA) as worthy of further evaluation. These are: (1) the d-Li source, in which 35-MeV deuteron beams are incident on flowing lithium targets, (2) the t-H{sub 2}O source, in which 21-MeV triton beams strike high-speed water jets, and (3) the Spallation source in which a 600-MeV proton beam bombards a heavy-metal target.
Accelerator-driven sub-critical target concept for transmutation of nuclear wastes: A means of transmuting key long-lived nuclear wastes, primarily the minor actinides (Np, Am, Cm) and iodine, using a hybrid proton accelerator and sub-critical lattice, is proposed. By partitioning the components of the light water reactor (LWR) spent fuel and by transmuting key elements, such as the plutonium, the minor actinides, and a few of the long-lived fission products, some of the most significant challenges in building a waste repository can be substantially reduced. The proposed machine, based on the described PHOENIX Concept, would transmute the minor actinides and the iodine produced by 75 LWRs, and would generate usable electricity (beyond that required to run the large accelerator) of 850 MW{sub e}. 19 refs., 20 figs.
Accelerator Physics and Modeling: Proceedings: This report contains papers on the following topics: Physics of high brightness beams; radio frequency beam conditioner for fast-wave free-electron generators of coherent radiation; wake-field and space-charge effects on high brightness beams. Calculations and measured results for BNL-ATF; non-linear orbit theory and accelerator design; general problems of modeling for accelerators; development and application of dispersive soft ferrite models for time-domain simulation; and bunch lengthening in the SLC damping rings.
Accelerator Simulation and Operation Via. Identical Operational Interfaces: The CEBAF accelerator contains approximately 2500 power supplies, 340 klystrons, and 800 beam monitors. The operation of such a complex machine requires a control system which can provide a high degree of automation with strong support by simulation and modeling programs.\nWe present the architecture and first results of a control system which allows one the use of identical operation procedures and interfaces for operation of the real accelerator and high-level accelerator simulation programs. The interfaces were developed using TACL (Thaumaturgic Automated Control Logic) control software, developed at CEBAF for accelerator control. This setup provides the capability to: (1) test and debug the various operation procedures before the completion of the accelerator, (2) execute machine simulations under realistic environmental conditions, and (3) preview and evaluate the effectiveness of operational procedures during run time. The optimized simulation program adds only two seconds to
Accelerator technology for Los Alamos nuclear-waste-transmutation and energy-production concepts: Powerful proton linacs are being studied at Los Alamos as drivers for high-flux neutron sources that can transmute long-lived fission products and actinides in defense nuclear waste, and also as drivers of advanced fission-energy systems that could generate electric power with no long-term waste legacy. A transmuter fed by an 800-MeV, 140-mA cw conventional copper linac could destroy the accumulated {sup 99}Tc and {sup 129}I at the DOE's Hanford site within 30 years. A high-efficiency 1200-MeV, 140-mA niobium superconducting linac could drive an energy-producing system generating 1-GWe electric power. Preliminary design concepts for these different high-power linacs are discussed, along with the principal technical issues and the status of the technology base. 9 refs., 5 figs., 4 tabs.
Accelerator technology for the Los Alamos ATW (accelerator transmutation of nuclear waste) system: The Los Alamos concept for accelerator transmutation of nuclear waste (ATW) employs a high-power proton linear accelerator to generate intense fluxes of thermal neutrons (>10{sup 16} n/cm{sup 2}-s) through spallation on a lead-bismuth target. The nominal beam energy for an ATW accelerator is 1.6 GeV, with average current requirements ranging from 250 mA to 30 mA, depending on application specifics. A recent study of accelerator production of tritium (APT) led to the development of a detailed point design for a 1.6 GeV, 250 mA cw proton linac. The accelerator design was reviewed by the Energy Research Advisory Board (ERAB) and found to be technically sound. The Panel concluded that linac of this power level could now be implemented within the existing technology base, given an adequate component development program and an integrated engineering demonstration of the front end.
Acceptance criteria for heat exchanger head staybolts: Each of the six primary coolant loop systems of the Savannah River Site production reactors contains two parallel single-pass heat exchangers to transfer heat from the primary coolant (D{sub 2}O) to the secondary cooling water (H{sub 2}O). The configuration of the heat exchangers includes a plenary space defined by the heat exchanger tubesheet and the heat exchanger head at both the heat exchanger inlet and outlet to the primary piping. The primary restraint of the heat exchanger head (Type 304 stainless steel) is provided by 84 staybolts (Type 303 stainless steel) which attach to the tubesheet. The staybolts were cap seal-welded in the mid-1960's and are immersed in moderator. Access to inspect the staybolts is limited to a recently-developed ultrasonic technique shooting a beam through the staybolt assembly. Acceptance Criteria to allow disposition of flaws detected by UT inspection have been developed. The structural adequacy to protect against collapse loading of the head is demonstrated by finite element analysis of the head assembly and fracture analysis of flaw postulates in the staybolts. Both normal operation and normal operation plus seismic loading conditions were considered. Several bounding cases containing various configurations of nonactive (exceeding critical flaw size) staybolts were analyzed. The model of the head assembly can be applied to evaluate any active staybolt configurations based on the results from future inspections. 9 refs.
Acceptance criteria for heat exchanger head staybolts: Each of the six primary coolant loop systems of the Savannah River Site production reactors contains two parallel single-pass heat exchangers to transfer heat from the primary coolant (D{sub 2}O) to the secondary cooling water (H{sub 2}O). The configuration of the heat exchangers includes a plenary space defined by the heat exchanger tubesheet and the heat exchanger head at both the heat exchanger inlet and outlet to the primary piping. The primary restraint of the heat exchanger head (Type 304 stainless steel) is provided by 84 staybolts (Type 303 stainless steel) which attach to the tubesheet. The staybolts were cap seal-welded in the mid-1960`s and are immersed in moderator. Access to inspect the staybolts is limited to a recently-developed ultrasonic technique shooting a beam through the staybolt assembly. Acceptance Criteria to allow disposition of flaws detected by UT inspection have been developed. The structural adequacy to protect against collapse loading of the head is demonstrated by finite element analysis of the head assembly and fracture analysis of flaw postulates in the staybolts. Both normal operation and normal operation plus seismic loading conditions were considered. Several bounding cases containing various configurations of nonactive (exceeding critical flaw size) staybolts were analyzed. The model of the head assembly can be applied to evaluate any active staybolt configurations based on the results from future inspections. 9 refs.
Accident Management to Prevent Containment Failure and Reduce Fission Product Release: Brookhaven National Laboratory, under the auspices of the US Nuclear Regulatory Commission, is investigating accident management strategies which could help preserve containment integrity or minimize releases during a severe accident. The strategies considered make use of existing plant systems and equipment in innovative ways to reduce the likelihood of containment failure or to mitigate the release of fission products to the environment if failure cannot be prevented. Many of these strategies would be implemented during the later stages of a severe accident, i.e. after vessel breach, and sizable uncertainties exist regarding some of the phenomena involved. The identification and assessment process for containment and release strategies is described, and some insights derived from its application to specific containment types are presented. 2 refs., 5 figs., 2 tabs.
Accident simulation and consequence analysis in support of MHTGR safety evaluations: This paper summarizes research performed at Oak Ridge National Laboratory (ORNL) to assist the Nuclear Regulatory Commission (NRC) in preliminary determinations of licensability of the US Department of Energy (DOE) reference design of a standard modular high-temperature gas-cooled reactor (MHTGR). The work described includes independent analyses of core heatup and steam ingress accidents, and the reviews and analyses of fuel performance and fission product transport technology.
Accreditation of ionizing radiation protection programs: There are over one million workers in the United States who have the potential to be exposed to ionizing radiation. Therefore, it is necessary to determine accurately the quantity of radiation to which they may have been exposed. This quantity if measured by personnel dosimeters that are carried by individuals requiring radiation monitoring. Accreditation of the organizations which evaluate this quantity provides official recognition of the competence of these organizations. Accreditation programs in the field of ionizing radiation protection have been in operation for a number of years, and their experience has demonstrated that such programs can help to improve performance.

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