Transient nuclear inversion by X-Ray Free Electron Laser in a tapered x-ray waveguid

TL;DR

This paper theoretically demonstrates that tapered x-ray waveguides can focus and guide intense x-ray radiation from free electron lasers, enabling significant enhancement of nuclear interactions and potential control of nuclear states.

Contribution

It introduces the concept of using tapered x-ray waveguides with high-Z cladding to achieve high-intensity x-ray guidance and nuclear population inversion, a novel approach in x-ray quantum optics.

Findings

X-ray intensity can be increased by up to three orders of magnitude.

Tapered waveguides can focus x-ray beams to enhance nuclear interactions.

Potential for controlling nuclear states using x-ray waveguides.

Abstract

By restricting the spatial energy transmission of an electromagnetic wave, dielectric waveguides transmit light over long distances at sustained intensity. Waveguides have been used in the microwave and optical range to maintain strong signal intensities in connection with lasers, but guiding of intense short-wavelength radiation such as x-rays has proven more cumbersome. Here we investigate theoretically how tapered x-ray waveguides can focus and guide radiation from x-ray free electron lasers. Elliptical waveguides using a cladding material with high atomic number such as platinum can maintain an x-ray intensity up to three orders of magnitude larger than in free space. This feature can be used to significantly enhance resonant interactions of x-rays, for instance driving nuclear transitions up to transient nuclear population inversion. This could be the first breakthrough in nuclear state population control. Our results anticipate the important role of tapered x-ray waveguides in the emerging field of x-ray quantum optics with nuclear transitions.