Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets

Abstract

Particle acceleration based on high intensity laser systems (a process known as laser-plasma acceleration) has achieved high quality particle beams that compare favourably with conventional acceleration techniques in terms of emittance, brightness and pulse duration. A long-term difficulty associated with laser-plasma acceleration--the very broad, exponential energy spectrum of the emitted particles--has been overcome recently for electron beams. Here we report analogous results for ions, specifically the production of quasi-monoenergetic proton beams using laser-plasma accelerators. Reliable and reproducible laser-accelerated ion beams were achieved by intense laser irradiation of solid microstructured targets. This proof-of-principle experiment serves to illuminate the role of laser-generated plasmas as feasible particle sources. Scalability studies show that, owing to their compact size and reasonable cost, such table-top laser systems with high repetition rates could contribute to the development of new generations of particle injectors that may be suitable for medical proton therapy.

Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

“…This is a strong idealization of typical TNSA proton beams which have a broad, roughly exponentially varying energy spectrum. However, methods exist to produce a more monochromatic energy distribution by restricting the source region within the TNSA context to a small volume [40][41][42], or alternatively, through exploiting a radiation-pressureinduced acceleration mechanism [43,44]. The initial (z¼z i ¼0) rms-beam width x ðz¼z i Þ¼ xi and divergence…”

“…Before explicitly calculating the form factor F for Gaussian and uniform choices of b ðrÞ to fully specify the envelope model, it is instructive to interpret the terms in the envelope equation (41). First, ðzÞhx 2 i 1=2 ?…”

Investigations of Field Dynamics in Laser Plasmas with Proton Imaging

“…The proton spectra are usually continuous up to a sharp cut-off representing the highest proton energies. However, for specific target types ion spectra with dips [91,92] or quasi-monoenergetic [13][14][15][16] features have been observed. Since the generation of monoenergetic ion beams is of high interest for many applications, it will be discussed shortly in the next section.…”

“…To achieve tailored spectra, especially monoenergetic ion beams, different approaches exist. For instance, in reference [13] micro-structured targets were used. In reference [14] quasi-monoenergetic ions are accelerated by heating the target and thus manipulating the target surface.…”

“…Concave targets focus or collimate the whole ion beam [1,[10][11][12]. Manipulated target surfaces or microstructured targets can deliver quasi-monoenergetic ion and proton beams [13,14]. At the Max-Born-Institute it was shown for the first time that also water-droplet targets can deliver quasi-monoenergetic deuteron and proton beams [15,16] (see Chapter 5.2).…”