Professor Marco Borghesi
Laser-driven ion acceleration for biomedical applications

High power laser interactions with matter provides new, compact ways of accelerating particles to high energy, producing beams with unique properties, particularly in terms of ultrashort burst emission and high brilliance. At QUB, we pursue, in particular, research in the acceleration of ions, and we have contributed over the years some major developments to this field of research.

A major motivation is the potential application of these beams in the biomedical context, e.g. as a future driver in radiotherapy, or for the exploration of fundamental processes of radiation interaction with biological media.   A particularly interesting aspect of these interactions arises from the peculiar properties of laser-driven ion sources, which can deliver large doses to a sample in very short times (ranging from 10s of ps to ns depending on the sample’s distance from the source), resulting in extremely high dose rates (in excess of 10⁹ Gy/s). This is many orders of magnitude higher than used in conventional studies, and has opened up to investigation

Research in this area has been recently carried out in the framework of an extended UK-wide consortium (A-SAIL), supported by large EPSRC funding, such a recent Programme Grant (2013-2020). This research is led by Prof. M. Borghesi, and currently involves Dr S. Kar and Dr D. Margarone from the Centre for Plasma Physics , as well as Prof. K. Prise from the The Patrick G Johnston Centre for Cancer Research.

In our experiments, we aim to optimize the ion beam properties towards these applications, and are currently focusing our attention on advanced acceleration mechanisms which aim to harness the enormous radiation pressure associated to ultra-intense, short laser pulses to accelerate ions directly from the bulk of ultrathin foils (10-100 nm thick). Expansion of the foils during the irradiation may lead to regimes where an enhanced coupling and complex interplay between laser radiation, electron and ions in the plasma can also enhance the acceleration efficiency.

This has led to significant advances in the acceleration of protons (with record energies demonstrated in [1]) as well as carbon ions [2].

We are also engaged in the development of target-based techniques which act on the ions after their acceleration from a foil, in order to optimize their properties (such as divergence and energy spectrum) towards applicative use of the ions [3].

The ion sources are used to explore the radiobiology of extreme irradiation regimes. In experiments employing high power lasers, such as for example, the VULCAN and GEMINI laser systems at STFC Central Laser Facility, we irradiate cellular samples (including both normal and cancerous cells) with laser-accelerated, short burst of protons and Carbon ions, and we investigate the biological effects of these processes (e.g. damage to the cells’ DNA and subsequent cell death, or inhibition of cell functions in surviving cells). This research (see for example [4]) is aimed to establish the biological effectiveness of irradiations at these extreme, and yet unexplored, dose rates, in comparison with known cell response at the standard dose rates employed in radiobiology and cancer radiotherapy. A programme of irradiations at conventional accelerators supports these investigations, which are aimed to establish a basis for the potential future use of laser-driven particle in radiotherapy. 

[1] A. Higginson et al., Near-100 MeV protons via a laser-driven transparency-enhanced hybrid acceleration scheme, Nature Comm., 9, 724 (2018)

[2] C. Scullion et al, Polarization Dependence of Bulk Ion Acceleration from Ultrathin Foils Irradiated by High-Intensity Ultrashort Laser Pulses, Phys. Rev. Lett., 119, 054801 (2017)

[3] S. Kar et al, Guided post-acceleration of laser-driven ions by a miniature modular structure, Nature Comm., 7, 10792 (2016)

[4] F. Hanton et al, DNA DSB Repair Dynamics following Irradiation with Laser-Driven Protons at Ultra-High Dose Rates, Sci. Rep., 9, 4471 (2019)