Development of new approaches to produce compact sources of high energy ions has the potential to lead to an array of real-world applications – from proton therapy as a cancer treatment, to radiation-driven chemistry and materials characterisation. Efforts to increase the maximum energy of ions accelerated in intense laser-plasma interactions have been the focus of international scientific activity over recent years in order to bring these sources closer to the realisation of such applications. This is one of the objectives of the ESPRC-funded A-SAIL project, which aims to develop laser-driven ion acceleration towards medical applications.
A recent experiment led by Paul McKenna and his team from the University of Strathclyde, in collaboration with Queen's University Belfast, Shanghai Jiao Tong University and researchers from the Central Laser Facility, used the CLF's own Vulcan laser to create proton energies close to 100 MeV. The maximum proton energy measured is in the range 94 to 101 MeV, as defined by the energy resolution of the detection technique. Following this, we are pleased to announce that the results of this ground-breaking EPSRC-funded research have just been published in the high impact science journal, Nature Communications.
The rapidly evolving nature of intense laser-foil interactions is a challenge because it can limit the effectiveness of individual acceleration mechanisms. However, as shown in the latest work, it can also give way to the development of hybrid schemes involving two or more mechanisms, which can enable additional degrees of control on the final ion beam properties.
The high energies measured in the Vulcan experiment were achieved by exciting a hybrid form of radiation pressure-sheath acceleration with an ultrathin foil irradiated by a linearly polarized laser pulse. The onset of relativistic transparency and an associated jet of super-thermal electrons helped to enhance the double-peaked electrostatic field structure responsible for ion acceleration, driving higher proton energies over a narrow angular range.
The results from Vulcan promote the further development of laser-driven ion sources and open up a potential new route to actively controlling the energy spectral and spatial energy distributions of beams of high energy protons produced via intense laser-foil interactions. Implications for acceleration using multi-petawatt laser pulses are also discussed in the Nature Communications paper.
To read more, please go to: https://www.nature.com/articles/s41467-018-03063-9