FLASH radiotherapy delivered at ultrahigh dose-rates (UHDR) has shown promise in reducing normal tissue toxicity while maintaining tumor control, which could revolutionize cancer treatment. In this talk, some of the current research aimed towards clinical translation of FLASH and its challenges will be discussed. The history of FLASH radiotherapy from first in vitro experiments to the ongoing clinical trials will be presented. The engineering challenges of UHDR radiation sources and the need for accurate online dose measurements, where optical dosimetry might play an important role, will be discussed. Radiobiological hypotheses responsible for the FLASH effect will be briefly discussed.

In this study, we analyzed the X-ray fluorescence of the multi-layer material with aluminum tape-based laser-induced X-ray and electron sources. We used Ti: Sapphire laser with power of 10 W, repetition rate of 1 kHz, and pulse width of 36 fs. The X-ray fluorescence signals of the multi-layer material’s surface and interior were distinguishable by the penetration depth difference between X-rays and electron sources. And the quantitative measurement of alloy samples was also measured by corresponding sources. Combining these two complementary sources can provide a useful tool for analyzing the surface and interior of multi-layer materials.

The goal of the dual KB mirror system for the CXI beamline of the LCLS-HE upgrade is to realize both micro-focusing and nano-focusing functions over a photon energy range of 7-21 keV. This system consists of two pairs of bendable mirrors with the length of 1 m. The dynamical range of the mirror bending is up to 104 due to the fine adjustment of the focusing length to 1 mm over a 10 m range. The prefigured shape and the width profile of each mirror are optimized to have good performance for both functions.

The thermal deformation requirement for wavefront preservation through an X-ray crystal monochromator is found to restrict the standard deviation of the height error to less than 25 pm under certain conditions. By optimizing effective cooling temperature of liquid nitrogen cooled crystals, combined with the compensation of second order component in thermal deformation, we have an approach to reach this unprecedented requirement. As an example, the criteria on thermal deformation of a high heat-load monochromator crystal for a LCLS-II-HE beamline can be achieved for 100 W FEL beam. Wavefront propagation simulations confirm that the reflected beam intensity profile is satisfactory.

X-rays provide exceptional insights into complex samples due to their high penetration depth and chemical sensitivity. Nanostructured diffractive optics are a type of X-ray optics that have enabled many scientific discoveries at large research facilities. The development of these optics has been facilitated by recent advancements in nanotechnology. XRnanotech, a spin-off from Paul Scherrer Institut in Switzerland, uses various nanolithography methods to increase the performance and applicability of diffractive optics. These include transmission achromatic X-ray optics, blazed reflection gratings, and ultra-high resolution zone plates. Latest advancements in diffractive optics fabrication offer exciting possibilities for future X-ray research.

We developed a new process for low blaze angle (LBA) diffraction gratings for x-ray applications. The process provides a perfect shape of the saw-tooth grooves and preserves high precision of the optical surface of the grating substrate. An LBA grating is made by double-replication of a master blazed grating by nanoimprinting followed by a transfer of the polymer replica into a Si grating substrate by a plasma etch. The plasma etch process optimized for a certain etch rate ratio for the polymer and Si provides a reduction of the groove depth and the blaze angle down to 0.2 degrees. The reduction results in an improvement of surface roughness compared to the master grating and mitigate process non-uniformity owing to the scaling down effect. We investigate the quality and performance of the fabricated LBA gratings and evaluate process accuracy and reproducibility. This work was supported by the US Department of Energy under contract number DE-AC02-05CH11231.

We have developed a two-stage soft X-ray focusing system at BL1 of SACLA. The system consists of two free-form mirrors, a ring focusing mirror and a quasi ellipsoidal mirror. Soft X-rays with photon energies around 120 eV can be focused down to φ350 nm. By using its unique intensity pattern after focusing, we propose a background-free signal detection method for extremely low optical signals such as SHG of soft X-ray.

The Materials Research Collaborative Access Team’s bending magnet beamline (10-BM) at Argonne National Laboratory is being upgraded to deliver a significantly higher photon flux with improved spectral resolution in the 4–32 keV photon energy range. This will allow faster x-ray absorption spectroscopy measurements. The plan is to use an aspherical focusing mirror downstream of the x-ray monochromator to collect and focus a significant part of the vertically collimated horizontally divergent beam. An x-ray mirror surface is typically coated with high-atomic-number elements such as platinum (Pt) to allow high energy photon reflection. The absorption edges of such coating materials, however, introduce experimental complications when performing spectroscopy measurements at energies near those edges. This problem is typically addressed by coating the mirror substrate (typically silicon) with two different materials on two parallel longitudinal stripes. This option, however, is not possible for two-dimensional focusing optics. This paper reports on a multilayer coating over an x-ray mirror that provides high reflectivity over the entire energy range of interest with minimal absorption edges. An acceptable coating was determined using numerical simulations and a pair of flat silicon mirrors were coated and tested: one with a bilayer of Pt (20 nm) and Al2O3 (10 nm), and another with an additional carbon layer (8 nm). The reflectivity of both mirrors was measured and then re-measured after they were both heated to 70° C for 8 hours for a stability test. Experimental results show excellent stability, high reflectivity over the entire 4–32 keV energy range, and the suppression of the Pt absorption edges to below 1% reflectivity.