Next generation laser-driven neutron sources for ultrafast studies

Neutrons are one of the fundamental particles of an atom with no charge. Because of their unique ability to reach nuclei, neutrons provide unique and valuable insights to many aspects of the physics of matter beyond the capability of any charged particle or ionizing radiation probes. We are now seeing the world at the very limits of our existing neutron probes - the key limitation being the temporal resolution. The possibility of ultrafast (significantly faster than a millionth of a second) studies using neutrons, either as a pump or a probe, has not yet been considered because no high flux sources of such short neutron pulses exist.

Thanks to the continuing developments in laser technology and related areas, access to ultra-intense laser pulses (well above 10^15 watts of pulsed power focussed down to a spot of a fraction of the diameter of human hair) has opened several new avenues of research in plasma physics. One of them is the bourgeoning field of ion acceleration driven by the intense laser light pressure (also called radiation pressure (RP)). Depending on laser and target parameters, the interaction produces either moderate kinetic energy (corresponding to a speed of 1000 Km/sec) and near solid density jets of high Mach numbers, or mono-energetic and collimated ion pulses of ultra-high energy (orders of magnitude higher than the jet ions). The proposal is aimed to develop, test and apply a novel laser based neutron source, exploiting the unique combination of parameters at the frontier of RP driven ion bunches, Since the source is driven by the ions accelerated by a highly efficient laser driven ion acceleration mechanism, it lays a foundation towards next generation neutron facility in light of the rapid development in laser technology. The source with enhanced characteristics will enable expansion of our understanding of ultrafast molecular dynamics in a wide range of discipline, from physics to biology. A laser driven source may bring further advantages in terms of cost reduction and compactness, reduction of radioactive pollution and ability of radiation confinement by closed-coupled irradiation experiments, which will make the source more appealing for industrial, technological and medical applications, such as cancer therapy centre based on a novel, highly promising technique employing neutrons.

The output of the proposed research will have impact and relevance at several levels and over different timescales. Some of the impact is associated with the training aspect of the activity, others are expected to rise directly from the applied research which will be carried out during the research programme.

Training two Ph.D. students in an exciting multidisciplinary field of research is one of the immediate impact on society that the project is programmed to make. The training will provide them the necessary skills to develop their career pathways in future. During their degree they will make efficient use of national laser facility and may continue to provide scientific supports to the facility in future by joining the team, promoting UK science. The proposed research will also complement the breadth of activities of the host organisation and will facilitate recruitment prospects, particularly with respect to attracting Ph.D. students from outside Northern Ireland and overseas.

Two objectives of the proposed research, such as, characterising a novel radiography technique to greatly improve security measures for large cargos and developing a source for a novel cancer therapy centre, will have direct impact on the society in a long term. Further impact on society can be envisioned through the potential of the proposed method in setting milestones for next-generation neutron facilities, creating new opportunities for training and recruiting scientists, creating new laboratory facilities. This can be seen as a critical pathway to social and economic impact as it lays the basis of continuous supply of well-trained and qualified personnel with a range of options for career in academia, R&D, industry and other sectors, such as finance.

The proposed research will have an important role to play in facing present energy challenges by providing valuable information in answer to two of the most fundamental physics questions related to fusion energy power plants, the most promising source for our bright future.
The proposed work on neutron source development and underlying ion acceleration mechanism has a clear strategic importance to science, in light of the high power and high repetition laser developments. If successful, the project will stretch the realm of ultrafast research for a wider scientific community and will benefit directly our society by improving security measures. It may also open up opportunities for the development of university scale table-top neutron probes and, possibly, novel cancer therapy centres based on the Boron neutron capture technique. Industry may gain from the development of an alternative source for applications such as fuel cell and Li battery diagnosis, semiconductor doping etc.