Towards an ultra-compact x-ray free-electron laser (Conference Presentation)

The short-wavelength FEL is a revolutionary instrument, which for the first time has permitted the structure of atomic and molecular matter to be interrogated at the spatial and temporal scales relevant to electron rearrangement – A and fsec, respectively. This frontier tool has produced a paradigm shift in imaging, but suffers from limited access, as the $1B-class instruments needed for both photon science and exploring the attosecond world of the FEL are located at a few national labs worldwide. Due to this expense, access to coherent X-rays for iterative experimentation by the optimal width of the photon science community is suppressed. Further, R&D aimed at cutting edge FEL physics and in the US, has extremely limited resources, thus dimming the prospects for a new, approach to FELs in which the cost and scale of the machine is consistent with university financial and space budgets. The scientific and technological environment of the free-electron laser and related next generation instruments is complex, embracing a wide range of cutting edge fields which are undergoing rapid maturation. This infrastructure is intended to address both scientific and educational roadblocks in the current FEL and photon science communities, by pursuing a vision of an FEL that is an extension of current techniques, pushed to the limits of current performance. This vision entails an approach based on progress in three areas: very high brightness electron beam production; compact, high gradient acceleration; advanced beam manipulations aimed a current enhancement without phase space dilution; and new techniques in realizing very short period undulators. UCLA has played a lead role in high brightness beam production for several decades. It has recently, with support of the NSF through the Center for Bright Beams (CBB), brought a new concept towards fruition, a cryogenic RF photoinjector capable of operations at very high field, and achieving an order of magnitude improvement in electron beam brightness. This beam can be accelerated to GeV energies with the same technical approach, recently shown in proof-of-principle experiments by a Stanford and UCLA. These beams can, further, be compressed by optical bunching techniques, as has been studie successfully at SLAC and UCLA in recent years. Finally, one can utilize a new generation of undulators with periodicity in the mm-scale, exploiting MEMS-based research in this area. In combination, this approach may produce an Angstrom X-ray FEL with fluxes up to ~5% of the LCLS, yet costing an estimated $20M and occupying a footprint of a few tens of meters. This new class of coherent light source will be exploited UCLA and collaborating scientists to explore a new model for both advanced FEL and photon science experimentation. UCLA and its direct collaborators in universities, national labs worldwide, and industry are leaders in these fields, the expertise needed to push thiss state-of-the-art concept is available.