This proposal describes a programme of research on single-particle and collective radiation-beam-plasma interactions at high field intensities, production of high-brightness particle beams with femtosecond to attosecond duration, new sources of coherent and incoherent radiation that are both compact and inexpensive, new methods of accelerating particles which could make them widely available and, by extending their parameter range, stimulate new application areas. An important adjunct to the proposal will be a programme to apply the sources to demonstrate their usefulness and also provide a way to involve industry and other end-users. The project builds on previous experiments and theoretical investigations of the Advanced Laser Plasma High-energy Accelerators towards X-rays (ALPHA-X) project, which has demonstrated controlled acceleration in a laser-plasma wakefield accelerator (LWFA), initial applications of beams from the LWFA and demonstrations of gamma ray production due to resonant betatron motion in the LWFA. The programme will have broad relevance, through developing an understanding of the highly nonlinear and collective physics of radiation-matter interactions, to fields ranging from astrophysics, fusion and nuclear physics, to the interaction of radiation with biological matter. It will also touch on several basic problems in physics, such as radiation reaction in plasma media and the development of coherence in nonlinear coupled systems.

The loss of Arctic sea-ice is one of the most compelling manifestations of man-made climate change. Profound environmental change is already affecting Arctic inhabitants and ecosystems. Increasing scientific evidence, including many key papers by the PI, suggests the impacts of sea-ice loss will be felt way beyond the poles. Linkages between Arctic sea-ice loss and extreme mid-latitude weather have become an area of increasing scholarly enquiry and societal interest. Yet, significant knowledge gaps remain that demand urgent attention; in particular, the robustness of response to sea-ice loss - and its underpinning physical causes - across different climate models. The Polar Amplification Model Intercomparison Project (PA-MIP) will significantly advance the state-of-the-art in understanding and modelling the climate response to Arctic and Antarctic sea-ice loss. It will enable deeper understanding of the causes and global effects of past and future polar change, and the physical mechanisms involved. PA-MIP is a novel and unique collaboration of UK and international scientists. To promote fruitful collaboration and drive research excellence, this proposal supports two key activities: a secondment scheme and a synthesis workshop, both with direct benefit to NERC-funded science.