Dose-efficient scanning Compton X-ray microscopy

The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure,induced by the necessarily high energy of short-wavelength radiation.Imaging the inelastically scattered X-rays at a photon energy of 60 keV(0.02 nm wavelength)offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography.We present images of dried,unstained,and unfixed biological objects obtained by scanning Compton X-ray microscopy,at a resolution of about 70 nm.This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision,a new wavefront measurement scheme for hard X rays,and efficient pixel-array detectors.The doses required to form these images were as little as 0.02%of the tolerable dose and 0.05%of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy.The images obtained provide a quantitative map of the projected mass density in the sample,as confirmed by imaging a silicon wedge.Based on these results,we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.

A Custom-Tailored Multi-TW Optical Electric Field for Gigawatt Soft-X-Ray Isolated Attosecond Pulses

Since the first isolated attosecond pulse was demonstrated through high-order harmonics generation(HHG)in 2001,researchers’interest in the ultrashort time region has expanded.However,one realizes a limitation for related research such as attosecond spectroscopy.The bottleneck is concluded to be the lack of a high-peak-power isolated attosecond pulse source.Therefore,currently,generating an intense attosecond pulse would be one of the highest priority goals.In this paper,we review our recent work of a TW-class parallel three-channel waveform synthesizer for generating a gigawatt-scale soft-X-ray isolated attosecond pulse(IAP)using HHG.By employing several stabilization methods,we have achieved a stable 50 mJ three-channel opticalwaveform synthesizer with a peak power at the multi-TW level.This optical-waveform synthesizer is capable of creating a stable intense optical field for generating an intense continuum harmonic beam thanks to the successful stabilization of all the parameters.Furthermore,the precision control of shot-to-shot reproducible synthesized waveforms is achieved.Through the HHG process employing a loose-focusing geometry,an intense shot-to-shot stable supercontinuum(50–70 eV)is generated in an argon gas cell.This continuum spectrum supports an IAP with a transform-limited duration of 170 as and a submicrojoule pulse energy,which allows the generation of a GW-scale IAP.Another supercontinuum in the soft-X-ray region with higher photon energy of approximately 100–130 eV is also generated in neon gas from the synthesizer.The transform-limited pulse duration is 106 as.Thus,the enhancement of HHG output through optimized waveform synthesis is experimentally proved.

Modeling of ultrafast X-ray induced magnetization dynamics in magnetic multilayer systems

In this work,we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials.With this tool,we have studied the response of Co/Pt multilayer system irradiated by an ultrafast extreme ultraviolet pulse at the M-edge of Co(photon energy~60 eV).It was previously investigated experimentally at the FERMI free-electron-laser facility,using the magnetic small-angle X-ray scattering technique.Our simulations show that the magnetic scattering signal from cobalt decreases on femtosecond timescales due to electronic excitation,relaxation,and transport processes both in the cobalt and in the platinum layers,following the trend observed in the experimental data.The confirmation of the predominant role of electronic processes for X-ray induced demagnetization in the regime below the structural damage threshold is a step toward quantitative control and manipulation of X-ray induced magnetic processes on femtosecond timescales.