Reflection Efficiency and Spectra Resolutions Ray-Tracing Simulations for the VOXES HAPG Crystal Based Von Hamos Spectrometer

Veronica De Leo,Catalina Curceanu,Florin Sirghi,Alessandro Scordo,Marco Miliucci

doi:10.3390/condmat7010001

Veronica De Leo, Catalina Curceanu + Show 3 more

Open Access

https://doi.org/10.3390/condmat7010001

Copy DOI

Abstract

The VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution Von Hamos X-ray spectrometer using HAPG (Highly Annealed Pyrolytic Graphite) mosaic crystals. This technology allows the employment of extended isotropic sources and could find application in several physics fields. The capability of the spectrometer to reach energy precision and resolution below 1 and 10 eV, respectively, when used with wide sources, has been already demonstrated. Recently, the response of this device, for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1,2 and FeKα1,2 XRF lines, has been investigated in terms of reflection efficiency by a dedicated ray-tracing simulation. Details of the simulation procedure and the comparison with the experimental results are presented. This study is crucial in order to retrieve information on the spectrometer signal collection efficiency, especially in the energy range in which the standard calibration procedures cannot be applied.

Highlights

An example of the resulting spectrum, after performing the calibration and fitting procedure reported in our previous work [5], is shown in the Figure 2. In this case the slits are set to maintain an angular divergence ∆θ of 0.7◦ and the distances between the source-to-HAPG crystal and crystal-to-detector are of 900.54 mm
These kind of spectra are used in the evaluation of the HAPG crystal reflection efficiency
We defined the geometry of the crystal, using the cylindrical one, and we introduced the value of the curvature radius, the mosaicity (ω = 0.1◦ ), usually provided by the producer, the position and the nominal Bragg angle at which the reflection occurs as shown in the snapshot reported in the Figure 7 on the left column; on the center instead, the XZ plot of the XRF photons emitted from the effective source and reflected by the HAPG

Summary

Introduction

In the spectrometer configuration used in our measurements the X-ray source and the position detector are placed on the axis of a cylindrical crystal. This configuration is known as Von Hamos and allows to increase the reflection efficiency due to the vertical focusing. This geometry permits to determine the source-crystal and the source-detector distances, L1 and L2 , respectively, by means of the Bragg angle (θ B ) and of the curvature radius of the crystal (ρc ): ρc (1). The active area is 32 × 8 mm ; strip width and thickness are, respectively, 50 μm and 420 μm; further details can be found in [5]

Experimental Procedure

Ray-Tracing Simulations

Discussion