Modeling and measurement of the scattering properties of the source pinhole in the BEaTriX facility
Date Issued
2021
Author(s)
SPIGA, Daniele
•
SALMASO, Bianca
•
BASSO, Stefano
Abstract
The purpose of this brief technical note is to provide an assessment of the performance of the tungsten pinhole placed in front of the microfocus Incoatec X-ray source with Titanium anode in the BEaTriX X-ray facility. The pinhole is a part of the collimator kit by Amptek purchased years ago to collimate a solid-state detector, and consists of a small (1/2 inch) tungsten disk with a 2.2 mm thickness and a 450 μm diameter. The pinhole is placed at a 20 mm distance from the source and limits the beam along the short arm of the facility, avoiding so the X-ray incidence on the tube walls which might cause unwanted X-ray reflection/scattering or diffuse background. At the same time, the pinhole located near the X-ray source provides visual reference for the parabolic mirror alignment.
Pinholes are crucial optical components, as they have to diaphragm an X-ray beam without degrading it. Due to the closeness of the lateral walls of the pinhole to the X-rays, the surface has to be properly ruggedized in order to avoid unwanted reflections or diffuse scattering when X-rays impinge on it in grazing incidence conditions. Should this condition not be fulfilled, the pinhole would cause a broadening of the X- ray source and a consequent worsening of the finally collimated X-ray beam in BEaTriX. In this short note, we will show measurements of the X-ray beam in the BEaTriX facility aiming at ascertaining the scattering properties of the pinhole surface. The conclusion is that the amount of scattered/reflected radiation off the pinhole is hardly detectable and that the pinhole appears perfectly suitable for the collimation of the X-ray beam in the short arm of BEaTriX.
Volume
INAF-OAB internal report 2021/04
Rights
open.access