Halos of intense proton beams

Abstract

Beam halo is an important issue for accelerator driven transmutation technologies and other applications of CW proton accelerators. These projects include, for example, the accelerator transmutation of waste, accelerator-based conversion of plutonium, accelerator production of tritium, and the development of a next-generation spallation neutron source. To keep radioactivation within acceptable limits these accelerators must operate with a very low beam loss (less than a nanoampere per meter). Beam loss is associated with the presence of a low density halo far from the beam core. Understanding the physics of halo production and determining methods to control beam halo are important to these projects. In recent years significant advances have been made, both analytically and computationally. In the following we describe recent developments in beam halo theory and simulation, including results from multi-million particle simulations.

On FFT-based convolutions and correlations, with application to solving Poisson's equation in an open rectangular pipe

“…a split-operator, FFT-based method for advancing the distribution in phase space one time step can be expressed as [18],…”

Rapidly converging chaos indicator for studying dynamic aperture in a storage ring with space charge

“…As an example of a time dependent Hamiltonian system, we use the 1-dimensional particle-core model [23][24][25][26][27] in a constant focusing channel. The particle and the envelope (i.e., beam core radius) can be described by the following Hamiltonian [24],…”

Critical issues for high-brightness heavy-ion beams --prioritized

“…Halo formation is still not thoroughly understood or experimentally validated [19][20][21][22][23]. Most of the beam current is within the beam "envelope", but a small fraction of beam ions undergo radial excursions of up to a few envelope radii; these are known as halo ions, and are the most likely to be lost by scraping off on the beam tube.…”

“…(Beam mismatch has been identified as a major source of beam halo [20].) Can we align scrapers sufficiently accurately relative to beam?…”

“…c. These experiments would also benefit from longer duration ion beams, to provide more time for desorbed gas to reach the beam. For this purpose, consider using STS-500 pulser: can we achieve operation at 500 kV for [18][19][20][21][22][23][24][25][26][27][28][29][30] µs with a modified existing facility? Can we vary duration to check the scaling with time of gas-induced beam loss?…”