Barbara Blind

Nuclear energy generation and waste transmutation using an accelerator-driven intense thermal neutron source

We describe a new approach for commercial nuclear energy production without a long-term high-level waste stream and for transmutation of both fission product and higher actinide commercial nuclear waste using a thermal flux of accelerator-produced neutrons in the 1016 n/cm2s range. Continuous neutron fluxes at this intensity, which is approximately 100 times larger than is typically available in a large scale thermal reactor, appear practical, owing to recent advances in proton linear accelerator technology and to the spallation target-moderator design presented here. This large flux of thermal neutrons makes possible a waste inventory in the transmutation system which is smaller by about a factor of 100 than competing concepts. The accelerator allows the system to operate well below criticality so that the possibility for a criticality accident is eliminated. No control rods are required. The successful implementation of this new method for energy generation and waste transmutation would eliminate the need for nuclear waste storage on a geologic time scale. The production of nuclear energy from 232Th or 238U is used to illustrate the general principles of commercial nuclear energy, production without long-term high-level waste. There appears to be sufficient thorium to meet the worlds energy needs for many millenia.

Production of uniform and well-confined beams by nonlinear optics

Abstract Particle beams with uniform and well-confined intensity distributions are desirable for medical treatment, food irradiation, and ion implantation, and are essential in high-intensity accelerator systems to prevent target damage and optimize target efficiency. One method for beam redistribution employs nonlinear beamline elements of odd multipolarity, such as octupoles and duodecapoles. The method is not limited to the production of uniform beam distributions. Techniques for producing uniform and well-confined beam distributions are reviewed. Beam redistribution is explained and the degree of uniformity and confinement achievable under various conditions is discussed. A method for tuning the size of the irradiation area is given. An unconventional combined-function magnet is presented. The effect of beam jitter on distributions is considered. Applications of the method are given.

Overview of the APT high-energy beam transport and beam expanders

The APT high energy beam transport (HEBT) and beam expanders convey the 1700-MeV, 100-mA cw proton beam from the linac to the tritium target/blanket assembly, or a tuning beam stop. The HEBT includes extensive beam diagnostics, collimators, and beam jitter correction, to monitor and control the 170-MW beam prior to expansion. A zero-degree beamline conveys the beam to the beam stop, and an achromatic be and conveys the beam to the tritium production target. Nonlinear beam expanders make use of higher-order multipole magnets and dithering dipoles to expand the beam to a uniform-density, 16-cm wide by 160-cm high rectangular profile on the tritium-production target. The overall optics design are reviewed, and beam simulations are presented.

Accelerator design and calculated performance of the Los Alamos HIBAF facility

Abstract The HIBAF 40 MeV accelerator and beam transport have been designed and studied with ISIS and PARMELA simulations. The nominal beam parameters for a 5 nC pulse are an emittance of 40π mm mrad, 300 A peak current, and an energy spread of 0.25%. We will discuss the major design issues and report on performance expectations.

The los Alamos Proton Storage Ring Fast-Extraction Kicker System

We describe the kicker system used by the Los Alamos Proton Storage Ring1 (PSR) for fast extraction of accumulated 800-MeV proton beam. The system has several severe constraints in terms of rise time, field quality, and magnet dimensions. These are, in turn, defined by characteristics of the stored beam, ring lattice, and the allowable activation of ring components. Design methods to meet the constraints are outlined here and we describe the novel modulators that produce the fast pulses required.

Beam expansion with specified final distributions

The formation of nearly uniformly distributed beams has been accomplished by the use of multipole magnets. Multipole fields, however, are an inappropriate basis for creating precise distributions, particularly since substantial departures from uniformity are produced with a finite number of multipole elements. A more appropriate formalism that allows precise formation of a desired distribution is presented. Design of nonlinear magnets for uniform-beam production and the optics of an accompanying expansion system are presented.

A high-flux accelerator-based neutron source for fusion technology and materials testing

Advances in high-current linear-accelerator technology since the design of the Fusion Materials Irradiation Test (FMIT) Facility have increased the attractiveness of a deuteriumlithium neutron source for fusion materials and technology testing. This paper discusses the conceptual design of such a source that is aimed at meeting the near-term requirements of a high-flux high-energy International Fusion Materials Irradiation Facility (IFMIF). The concept employs multiple accelerator modules providing deuteron beams to two liquid-lithium jet targets oriented at right angles. This beam/target geometry provides much larger test volumes than can be attained with a single beam and target and produces significant regions of low neutron-flux gradient. A preliminary beam-dynamics design has been obtained for a 250-mA reference accelerator module. Neutron-flux levels and irradiation volumes were calculated for a neutron source incorporating two such modules, and interaction of the beam with the lithium jet was studied using a thermal-hydraulic computer simulation. Approximate cost estimates are provided for a range of beam currents and a possible facility staging sequence is suggested.

High-resolution parallel particle-in-cell simulations of beam dynamics in the spallation neutron source linac

Abstract In this paper, we present results of using high-performance parallel computers to simulate beam dynamics in an early design of the Spallation Neutron Source (SNS) linac. These are among the most detailed linac simulations ever performed. The simulations have been performed using up to 500 million macroparticles, which is close to the number of particles in the physical system. The simulations are fully three-dimensional, and utilize RF cavity field data from modeling over 400 RF cavities. Furthermore, they use an improved model of the beam dynamics within the cavities. Traditionally, small-scale two-dimensional simulations have been performed on PCs or workstations. While such simulations are sufficient for rapid design and for predicting root mean square properties of the beam, large-scale simulations are essential for modeling the tails of the beam. The large-scale parallel simulation results presented here represent a three order of magnitude improvement in simulation capability, in terms of problem size and speed of execution, compared with typical two-dimensional serial simulations. In this paper we will show how large-scale simulations can be used to predict the extent of the beam halo and facilitate design decisions related to the choice of beam pipe aperture.

Overview and status of the Los Alamos PSR injection upgrade project

An upgrade is in progress to the Los Alamos Proton Storage Ring (PSR) to allow direct injection of the H/sup -/ beam into the ring and provide a beam bump system to move the circulating beam off the stripper foil. The primary benefits of this upgrade are matching the transverse phase space of the injected beam to the PSR acceptance and reduction of foil hits by the circulating beam by a factor of ten. Foil thickness is optimized to minimize the combination of circulating-beam losses plus losses due to excited H/sup 0/ states produced at injection. An overall factor of five reduction in losses is expected. The project comprises extensive modifications of the injection line, the injection section of the ring, and the waste-beam transport line. We will discuss the goals of the project, present an overview of the technical design, and describe the status of the implementation plan.

Lattice design of the LANL spallation-source compressor ring

A new compressor ring for 790-MeV protons is proposed at Los Alamos National Laboratory to provide 1 MW of beam power for a spallation-neutron source. The design has unit-transfer-matrix achromatic arcs. Bunching, beam-control, and extraction elements reside in dispersionless straight sections. The arc symmetry and further high-order corrections maximize tune space available to the beam. The ring-injection scheme uses direct H/sup -/ injection and care is taken in disposing of the unstripped and partially stripped beams. The lattice design allows for transverse phase-space painting to maximize particle storage, as well as minimize stored-beam foil traversals.<<ETX>>