Hard-x-ray spectrographs with resolution beyond 100<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>μ</mml:mi></mml:math>eV

Abstract

Spectrographs take snapshots of photon spectra with array detectors by dispersing photons of different energies into distinct directions and spatial locations. Spectrographs require optics with a large angular dispersion rate as the key component. In visible light optics, diffraction gratings are used for this purpose. In the hard-x-ray regime, achieving large dispersion rates is a challenge. Here we show that multicrystal, multi-Bragg-reflection arrangements feature cumulative angular dispersion rates almost two orders of magnitude larger than those attainable with a single-Bragg reflection. As a result, the multicrystal arrangements become potential dispersing elements of hard-x-ray spectrographs. The hard-x-ray spectrograph principles are demonstrated by imaging a spectrum of photons with a record high resolution of $\ensuremath{\Delta}E\ensuremath{\simeq}90$ $\ensuremath{\mu}$eV in the hard-x-ray regime, using multicrystal optics as the dispersing element. The spectrographs can boost research using inelastic ultrahigh-resolution x-ray spectroscopies with synchrotrons and seeded x-ray free electron lasers.