[en] Accelerator reliability corresponding to a very low frequency of beam interrupts is an important new accelerator requirement for accelerator-driven subcritical reactor systems. In this paper we review typical accelerator-reliability requirements and discuss possible methods for meeting these goals with superconducting proton-linac technology.

[en] We compare macroparticle simulations with measurements from a proton beam-halo experiment in a 52-quadrupole periodic-focusing channel. Three different initial distributions with the same Courant-Snyder parameters and emittances, but different shapes, predict different beam profiles in the transport system. Input distributions with greater population in the tails produce larger rates of emittance growth, a result that is qualitatively consistent with the particle-core model of halo formation in mismatched beams. The simulations underestimate the growth rate of halo and emittance for mismatched beams. Better agreement between simulations and experiment may require an input distribution that represents more accurately the tails of the real input beam.

[en] We compare macroparticle simulations with beam-profile measurements from a proton beam-halo experiment in a study of beam-halo formation in mismatched beams in a 52-quadrupole periodic-focusing channel. The lack of detailed measurement of the initial distribution is an important issue for being able to make reliable predictions of the halo. We have found earlier that different initial distributions with the same Courant-Snyder parameters and emittances produce similar matched-beam profiles, but different mismatched-beam profiles in the transport system. Also, input distributions with greater population in the tails produce larger rates of emittance growth. We have concluded that using only the known Courant-Snyder parameters and emittances as input parameters is insufficient information for reliable simulations of beam halo formed in mismatched beams. The question is how to obtain the best estimate of the input beam distribution needed for more accurate simulations. In this paper, we investigate a new least squares fitting procedure, which is applied to the simulations used to determine the injected beam distribution, in an attempt to obtain a more accurate description of halo formation than fiom simulation alone.

[en] An overview is presented of modern high-power proton linacs, including a survey of worldwide applications that are presently underway. The recent trend towards RF superconducting linacs is also discussed. We present some preliminary results from the beam-halo experiment recently carried out at Los Alamos

[en] We present physics results from an experimental study of beam halo in a high-current 6.7-MeV proton beam propagating through a 52-quadrupole periodic-focusing channel. The gradients of the first four quadrupoles were independently adjusted to match or mismatch the injected beam. Emittances and beam widths were obtained from measured profiles for comparisons with maximum emittance predictions of a free-energy model and maximum halo-amplitude predictions of a particle-core model. The experiment supports both models and the present theoretical picture of halo formation

[en] Recent developments in W-band (-100 GHz) traveling wave tube technology at Los Alarnos may lead to a compact high-power W-band RE source. A conceptual design of a compact 8-MeV electron linac that codd be powered by this source is presented, including electromagnetic structure calculations, proposed rnicrojbbrication and manufacturing methods, supporting calculations to estimate accelerator performance, and gumma production rates based on preliminary target geometries and expected output beam current.

[en] Advanced Beam-Dynamics Simulation Tools for the RIA Driver Linac; Low Energy Beam Transport and Radiofrequency Quadrupole

[en] Understanding and predicting beam halo is a major issue for accelerator driven transmutation technologies. If strict beam loss requirements are not met, the resulting radioactivation can reduce the availability of the accelerator facility and may lead to the necessity for time-consuming remote maintenance. Recently there has been much activity related to the core-halo model of halo evolution [1-5]. In this paper we will discuss the core-halo model in the context of constant focusing channels and periodic focusing channels. We will present numerical results based on this model and we will show comparisons with results from large scale particle simulations run on a massively parallel computer. We will also present results from direct Vlasov simulations

[en] We report measurements of transverse beam halo in mismatched proton beams in a 52-quadrupole FODO transport channel following the 6.7-MeV LEDA RFQ. Beam profiles in both transverse planes are measured using beam-profile diagnostic devices that consist of a movable carbon filament for measurement of the dense beam core, and scraper plates for measurement of the halo. The gradients of the first four quadrupoles can be independently adjusted to mismatch the RFQ output beam into the beam-transport channel. The properties of the measured mismatched beam profiles in the transport channel will be compared with predictions from multiparticle beam-dynamics simulations.

[en] The present configuration of the Low-Energy Demonstration Accelerator (LEDA) consists of a 75-keV proton injector, a 6.7-MeV 350-MHz cw radio-frequency quadrupole (RFQ) with associated high-power and lowlevel rf systems, a 52-magnet periodic lattice followed by a short high-energy beam transport (HEBT) and highpower (670-kW cw) beam stop. The rms beam emittance was measured prior to the installation of the 52-magnet lattice, based on wire-scanner measurements of the beam profile at a single location in the HEBT. New measurements with additional diagnostic hardware have been performed to determine the rms transverse beam properties of the beam at the output of the 6.7-MeV LEDA RFQ. The 52-magnet periodic lattice also includes ten beam position monitors (BPMs) evenly spaced in pairs of two. The BPMs provide a measure of the bunched beam current that exhibits nulls at different locations in the lattice. Model predictions of the locations of the nulls and the strength of the bunched beam current are made to determine what information this data can provide regarding the longitudinal beam emittance.