Measurement of reflectivity of spherically bent crystals using Kα signal from hot electrons produced by laser-matter interaction

Abstract

In an experiment at the laser facility ECLIPSE of the CELIA laboratory, University of Bordeaux, we measure the reflectivity of spherically bent crystals that are commonly used to investigate the propagation of fast electrons through the Kα radiation they generate in matter. The experimental reflectivity compares well with predictions from a ray-tracing code that takes into account the specific geometry, although the crystals seem to suffer from aging problems.

Studies on laser–plasma interaction physics for shock ignition

“…From the image lineout, taking into account the response of the densitometer and the calibration of Kodak AA400 film (26) we could calculate the number of X-ray photons incident on the film. To obtain the total number of photons, we then took into the solid angle seen by the crystal, its reflectivity (27), and the transmission of the mylar and aluminum filters used to reduce noise. In the calculation we assumed an isotropic emission and a monoenergetic electron beam.…”

Diagnostics of laser-produced plasmas

“…One tool is at the same time rather simple and very powerful and has found a very large application in recent experiment. This is the use of spherically bent crystals [26,27].…”

Experimental studies for generation, transport and applications of ultra-fast laser driven X-ray sources

“…This condition leads to the Bragg law, Eq.II.50. It is noteworthy to mention that Bragg formula needs to be corrected in the x-ray range, mainly for the phase shift factor and is given according to [Antonelli et al, 2015] as…”

“…II.19 (bottom) shows an example of the reflectance obtained numerically with XOP of an α-quartz crystal for an incident x-ray beam of Cu-kα (8.05 keV) as a function of the grazing incidence angle around the Bragg angle θ B . The crystal reflectance r can also be calculated using simple models such as the Darwin curve for planar crystals [Antonelli et al, 2015]. This one is given by…”

“…Here, ∆θ is the half width of the curve plateau where r = R max and x is θ i − θ B (λ B ). We note that the expression for ∆θ can be complex to calculate since its depending on many crystal parameters such as the structure factor, polarizability, etc ... More details concerning this issue can be fund in [Antonelli et al, 2015]. On the other hand, we can also calculate the spectral resolution of the detector by differentiating Eq.II.56…”