The main objectives of A-SAIL are:
Demonstration of all-optical acceleration of dense bunches of protons in the 60- 250 MeV range;
Demonstration of the acceleration of other low-Z ion species to similar energies/nucleon;
Optical control of the ion energy and spectrum at the source;
Assessment of the radiobiological effects of ultrafast ion energy deposition.
Progress toward these objectives will be achieved through a coordinated programme of activities in the following four closely interlinked Work Packages:
Work Package 1 (WP1):
Development and control of acceleration mechanisms . This is the core challenge of the programme. We will investigate and optimize emerging ion acceleration schemes, with a focus on processes based on the radiation pressure of an intense laser pulse, namely Light Sail (see fig.3), Hole Boring and shock acceleration, which members of the team have contributed to develop theoretically and numerically. All these schemes have potential for delivering high quality ion beams at the required energies, with narrow energy spread. Crucial issues will be stabilization of the accelerating phases, inhibition of transverse instabilities and experimental verification of predicted scaling with laser intensity and target density. This project will receive key input from WP2 and WP3, and will feed into WP4, by providing optimized sources for biological testing.
Work Package 2 (WP2):
Understanding and control of underpinning physical processes.. We will aim to unravel the physics of laser-matter interactions at the intensities of relevance to this project (1020-1023 W/cm2). This is a regime mostly unexplored, and clarification of a number of fundamental issues will be of high benefit to the developments planned in WP1, as it will allow a better control of the interaction and will improve predictive capability of acceleration models by accounting for the relevant physics. These include, among others: laser energy absorption and partition, relativistic transparency and hole boring and effects of radiation friction. In order to explore some of these issues, this WP will also gain from the targetry developments planned in WP3.
Work Package 3 (WP3):
Development of appropriate enabling technologies In order to support activities within WP1, WP2, WP4, we will address a number of technological challenges in 3 key areas: targetry, diagnostics and beam transport. Core to RPA targetry will be the provision of innovative cryogenic concepts and high-density, shaped gas flows. Diagnostic progress will respond to the challenge of diagnosing energy spectra and spatial profiles for multispecies high-energy ion beams, while delivery systems tailored to the beam properties will enhance capabilities within WP4. This work will in turn receive guidance from the ion beam properties emerging from WP1, and from the understanding of laser-target coupling arising from WP2.
Work Package 4 (WP4):
Assessment of biological effects of ions at extreme dose rates (Prise, Borghesi). Detailed investigations of the biological effects, in cell and tissue models, of ultra-short ion bursts will underpin progress toward medical applications of laser-ion beams. This is a novel area of radiobiology only now developing, which will benefit from the combined world-leading expertise of the CPP and CCRCB teams at QUB. While meaningful work is already possible at present energies and fluxes, developments in WP1 will provide crucial additional capabilities. Conversely, WP4 will feed back into WP1, and provide indications on how to fine tune, or refocus, source development work and enhance its relevance to future therapeutic use.
While the work will proceed along the broad lines discussed above, the structure of the program will be highly dynamic, with methods and milestones periodically reassessed. In Phase 1 we will explore, in parallel, several possible technical and scientific approaches, potentially capable of delivering the stated aims; in Phase 2 we will bring to fruition the progress made in Phase 1 in each of the Challenge areas by selecting the most promising routes for development and actively integrating these across the challenge areas. We will also apply the selected approaches and technology we develop to the higher laser pulse specifications achievable with next-generation laser facilities which are due to come online during phase 2 of the programme. Our aim is to have established, by the end of the programme, whether a laser-driven technology will be effectively capable of transforming cancer therapy – and to have developed a roadmap indicating the next steps required to achieve this.