Magnetic design of large-bore superconducting quadrupoles for the AHF.

The Advanced Hydrotest Facility (ANF), under study by LANL, utilizes large-bore superconducting quadrupole magnets to image protons for radiography of fast events. In this concept, 50-GeV proton bunches pass through a thick object and are imaged by a lens system that analyzes the scattered beam to determine object details. Twelve simultaneous views of the object are obtained using multiple beam lines. The lens system uses two types of quadrupoles: a large bore (48-cm beam aperture) for wide field of view imaging and a smaller bore (23 cm aperture) for higher resolution images. The gradients of the magnets are 10.14 T/m and 18.58 T/m with magnetic lengths of 4.3 m and 3.0 m, respectively. The magnets are sufficiently novel to present a design challenge. Evaluation and comparisons were made for various types of magnet design: shell and racetrack coils, cold and warm iron, as well as an active superconducting screen. Nb{sub 3}Sn cable was also considered as an alternative to avoid quenching under high beam-scattering conditions. The superconducting shield concept eliminates the iron core and greatly lessens the cryogenic energy needed for cool down. Several options are discussed and comparisons are made

Conceptual design of large-bore superconducting quadrupoles with active magnetic shielding for the AHF

The Advanced Hydrotest Facility, under study by LANL, utilizes large-bore superconducting quadrupole magnets. In the paper we discuss the conceptual design of such quadrupoles using active shielding. The magnets are specified to achieve gradients of up to 24T/m with a 28-cm warm bore and to have 0.01% field quality. Concepts for the magnet cryosystems and quench protection are also briefly discussed to confirm the reliability of the proposed design

A compact layout for a 50 GeV proton radiography facility

We describe a new compact layout for a 50 GeV proton radiography facility. The more compact design utilizes two-point extraction from the main ring to drive an optimal 8 view imaging system. The lattice design of both the main ring, and of the corresponding 8.5 GeV booster ring is described. The rings have very good longitudinal stability, which is of interest for other applications of high current proton machines in this energy range

Monte Carlo of Trapped Ultracold Neutrons in the UCNτ Trap

In the UCNτ experiment, ultracold neutrons (UCN) are confined by magnetic fields and the Earth’s gravitational field. Field-trapping mitigates the problem of UCN loss on material surfaces, which caused the largest correction in prior neutron experiments using material bottles. However, the neutron dynamics in field traps differ qualitatively from those in material bottles. In the latter case, neutrons bounce off material surfaces with significant diffusivity and the population quickly reaches a static spatial distribution with a density gradient induced by the gravitational potential. In contrast, the field-confined UCN—whose dynamics can be described by Hamiltonian mechanics—do not exhibit the stochastic behaviors typical of an ideal gas model as observed in material bottles. In this report, we will describe our efforts to simulate UCN trapping in the UCNτ magneto-gravitational trap. We compare the simulation output to the experimental results to determine the parameters of the neutron detector and the input neutron distribution. The tuned model is then used to understand the phase space evolution of neutrons observed in the UCNτ experiment. We will discuss the implications of chaotic dynamics on controlling the systematic effects, such as spectral cleaning and microphonic heating, for a successful UCN lifetime experiment to reach a 0.01% level of precision

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Design of end turns in current-dominated dipole and quadrupole magnets for fields with low higher-harmonic content.

A design approach based on a stream function with a single angular Fourier component can be used to specify the end-turn configuration in magnet windings with discrete blocks of conductors. The design approach is especially appropriate for large-bore, current-dominated magnets with many turns. The design method can be summarized as follows: First find a winding-block layout (block angles, number of turns in each block, etc.) for the central, straight-conductor part of the windings that produces two-dimensional fields with negligible higher harmonic content. Next, specify the numbers of groups of conductors into which each block of the 2-D part of the winding fans out in the end-turn region. Also specify the end-zone axial length and the shape-function profile for the end zones. Finally, generate turn contours by finding conductor-group centerline curves in the developed (flattened) cylinder surface that are contours of constant stream function. Individual turns are specified by constant parallel displacement from the group centerline curve in the developed winding surface. An interactive computer program performs the above steps has been written and has been used to design end windings for a test quadrupole example. The unwanted higher harmonics in both peak and integral fields as computed by the Biot-Savart law are remarkably low

Soft-edged magnet models for higher-order beam-optics map codes

Continuously varying surface and volume source-density distributions are used to model magnetic fields inside of cylindrical volumes. From these distributions, a package of subroutines computes on-axis generalized gradients and their derivatives at arbitrary points on the magnet axis for input to the numerical map-generating subroutines of the Lie-algebraic map code Marylie. In the present version of the package, the magnet menu includes: 1. cylindrical current-sheet or radially thick current distributions with either open boundaries or with a surrounding cylindrical boundary with normal field lines (which models high-permeability iron), 2. Halbach-type permanent mutipole magnets, either as sheet magnets or as radially thick magnets, 3. modeling of arbitrary fields inside a cylinder by use of a fictitious current sheet. The subroutines provide on-axis gradients and their z derivatives to essentially arbitrary order, although in the present 3rd and 5th order Marylie only the 0th through 6th derivatives are needed. The formalism is especially useful in beam-optics applications, such as magnetic lenses, where realistic treatment of fringefield effects is needed

A 50 kV solid state multipulse kicker modulator

Performance requirements, design concepts, and test results for a prototype multipulse kicker modulator based on solid-state switches and a voltage-adding transformer topology are described. Tape-wound cores are stacked to form the transformer primary windings and a cylindrical pipe that passes through the circular inner diameters of the cores serves as the secondary winding of the step-up transformer. Boards containing MOSFET switches, trigger circuitry, and energy-storage capacitors plug into the core housings. A 50 kV prototype modulator that meets most of the facility requirements has been designed, fabricated, and tested at LLNL. More recent work has been concerned with designing and testing cores and boards with the full volt-second capability needed for 24-pulse operation. Results of the 50 kV prototype tests, preliminary tests of the full-volt-second cores and boards, and future development needs are described

Magnet design concepts for the 100 MeV isotope production facility

The North Port Target Facility proposal includes a 100 MeV beam line to be is built at the LANSCE accelerator. In developing cost and schedule estimates for the proposal the greatest uncertainties are associated with the kicker magnet that is needed to divert portions of the beam into the new beam line. This magnet must fit into a rigidly defined space within the transition region of the existing accelerator and must operate in synchrony with the current accelerator operations systems, In addition, it must not degrade the beam qualify when beam is directed to other areas of the complex. Because of these constraints the magnet must be specifically designed and built for this intended application. We have produced conceptual designs of a kicker-magnet and power supply that will meet all of the design requirements. The power supply design is based on a working design for the RIKI kicker magnet that switches 800 MeV beam into the PSR. This report presents the kicker-magnet and power-supply designs and cost and schedule estimates for incorporation into the EP facility proposal. The feasibility of various design alternatives are briefly discussed

Overview of the bump-magnet system at the LANSCE proton storage ring

An upgrade program for increasing the stored beam current in the Proton Storage is presently under way. A part of the upgrade is the design and installation of a four-magnet beam-bumping system used for phase-space painting and minimizing interaction of the stored beam with the injection stripper foil. This paper describes the bump- magnet system including the relevant beam requirements, magnet specifications, power-cable specifications, pulsed-modulator requirements, and beam-tube eddy-current effects. The magnets are ferrite window-frame magnets with saddle windings. The series-pass pulsed modulators are programmable both in rise and fall time as well as amplitude. The peak current can be varied between 50 and 300 A. The pulsed-current rise-time is fixed at 1 ms, and the linear fall- time during which beam is injected into the ring can be varied between 0.5 and 1.5 ms