Novel quasi phase matching of high harmonic generation via advanced dual gas multi jet targets

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Ultrafast/attosecond physics is an exciting and dynamic research discipline, revealing atomic and molecular structures/processes with unprecedented spatial and temporal resolution. A significant limitation, however, has been the limited amount of laser energy that can be converted into XUV and soft x-ray regions of the spectrum. This is primarily due to phase mismatch between the driving laser and generated harmonic field, induced by the large free-electron contribution to the refractive index. Quasi-phasematching has been a front runner in the drive towards this objective but to date has been largely confined to low average power 'proof-of-principle' experiments in hollow core capillaries. This proposal seeks to develop a ground breaking new approach to quasi-phasematching developed by our group at QUB - dual gas multi-jet arrays in a capillary free geometry - to an exceptionally high standard.In this proposal we intend to build upon experimental observations already made which verify this exciting new technique. Together with our collaborators at the HASYLAB (DESY, Hamburg) and TEI Rethymno (Crete) the current design will be extended to generate a high average power harmonic source suitable for seeding the FLASH free electron laser at DESY. In a second strand of this proposal we will use the unique ability of this source to fine-control the phase of HHG emission for intense single attosecond pulse generation. This proposal will form the core of an international collaboration aimed at delivering the first high average power HHG source and intense attosecond pulses, and work will be performed on lasers at QUB, DESY and TEI Crete.