Tunable Narrow-Band High Harmonic Beamline Optimized for Ultrafast Soft X-Ray Photoemission and Imaging

This proposed work addresses the needs of a short pulse, tunable and monochromatic extreme ultraviolet and soft X-ray beamline that is table-top, low cost and easy-to-use for advanced material and nano- device studies using photoemission spectroscopy and nano-imaging techniques. The short-pulse and short- wavelength nature of this source enables capturing ultrafast dynamics in materials and nano-devices, and the wide range of tunability makes it applicable to a broad range of materials and nano-devices. This source can potentially impact the research and development in the fields of nanotechnology, new energy resources, and biomedical science. How this problem being addressed: We develop this beamline using a high harmonic generation source, which generates coherent, short-pulse, broadband, extreme ultraviolet and soft X-ray light through nonlinear up-conversion. The short pulse, tunable and monochromatic beamline is then realized by using a Monk-Gillieson monochromator with a grating operating at off-plane mount and in grazing incidence geometry. In Phase I, we have explored the feasibility of the beamline design in the following two aspects: 1. How to produce efficient broadband extreme ultraviolet and soft X-ray generation using high harmonic generation; 2. looking for optimum grating parameters and mounting geometry, as well as monochromator design to obtain high spectral resolution and short pulse duration. The results have demonstrated the feasibility, and helped to obtain the design parameters for the beamline. In Phase II, we will, first, turn this beamline design into a research prototype. Second, we will develop a diagnostics system that can measure the flux, stability, pulse duration and beam quality of the beamline for routine operation. Finally, we will test and optimize the performance, as well as lower the costs and improve the ease-of-use of the beamline. Commercial Applications and Other Benefits: A tabletop, tunable, short-pulse soft x-ray source that is optimized for elemental- and chemical-specific spectroscopy, microscopy and nano-imaging will enable discoveries and technological advances spanning a broad range of science and technology. In the short term, the proposed tunable, ultrafast, soft x-ray source can be combined with techniques such as angle-resolved photoemission spectroscopy (ARPES) to understand novel correlated electron materials, high-Tc superconductors, photovoltaic devices, catalytic processes, nanoscale magnetic dynamics, nanoscale heat and charge transport, thin film metrologies, and hydrogen storage, as well as uncovering new science in the area of molecular dynamics and the function of biological systems. In the longer term, the proposed beamline will make it possible to capture a 3-D, high resolution x-ray image of a nanodevice or a single cell with elemental- and chemical-specificity. All these findings will lead to faster and more energy-efficient electronics, new energy resources and new ways to treat diseases.