Pyrolitic Graphite Mosaic Crystal Thickness and Mosaicity Optimization for an Extended Source Von Hamos X-ray Spectrometer

Alessandro Scordo,Johann Zmeskal,Marco Miliucci,Catalina Curceanu,Florin Sirghi

doi:10.3390/condmat4020038

Abstract

Bragg spectroscopy, one of the best established experimental techniques for high energy resolution X-ray measurements, has always been limited to the measurement of photons produced from well collimated (tens of microns) or point-like sources; recently, the VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution and high precision X-ray spectrometer working also with extended isotropic sources. The realized spectrometer makes use of Highly Annealed Pyrolitic Graphite (HAPG) crystals in a “semi”-Von Hamos configuration, in which the position detector is rotated with respect to the standard Von Hamos one, to increase the dynamic energy range, and shows energy resolutions at the level of 0.1% for photon energies up to 10 keV and effective source sizes in the range 400–1200 μ m in the dispersive plane. Such wide effective source dimensions are achieved using a double slit system to produce a virtual point-like source between the emitting target and the crystal. The spectrometer performances in terms of reflection efficiency and peak resolution depend on several parameters, among which a special role is played by the crystal mosaicity and thickness. In this work, we report the measurements of the Cu(K α 1 , 2 ) and the Fe(K α 1 , 2 ) lines performed with different mosaicity and thickness crystals in order to investigate the influence of the parameters on the peak resolution and on the reflection efficiency mentioned above.

Highlights

High precision measurements of soft X-rays represent still today a very big challenge; such kind of measurements are strongly demanded in many fields of fundamental science, from particle and nuclear physics to quantum mechanics, as well as in astronomy and in several applications using synchrotron light sources or X-ray Free Electron Lasers (X-FEL) beams, in biology, medicine and industry
We report the measurements of the Cu(Kα1,2) and the Fe(Kα1,2) lines performed with different mosaicity and thickness crystals in order to investigate the influence of the parameters on the peak resolution and on the reflection efficiency mentioned above
This is a very important result to be taken into account when X-rays emitted from extended isotropic sources have to be measured

Summary

Introduction

High precision measurements of soft X-rays represent still today a very big challenge; such kind of measurements are strongly demanded in many fields of fundamental science, from particle and nuclear physics to quantum mechanics, as well as in astronomy and in several applications using synchrotron light sources or X-ray Free Electron Lasers (X-FEL) beams, in biology, medicine and industry. For several of these applications, in particular for nuclear physics experiments like those involving the measurement of exotic atoms’ radiative transitions, the detection of photons isotropically emitted from extended (non point-like) targets is required. As a consequence, when the photons emitted from extended isotropic sources (like a gaseous or liquid target) have to be measured, this method has been until now ruled out by the constraint to reduce the dimension of the target to a few tens of microns [4,5]

Results

Discussion

Conclusion