ISO/CD 32543-4

Non-destructive testing — Characteristics of focal spots in industrial X-ray systems — Part 4: Measurement of the effective focal spot size of micro- and nanofocus X-ray tubes with spot sizes < 100 µm using line group test objects

Scope

This document specifies a method for the measurement of effective focal spot dimensions between 0,2 µm and 100 µm of X-ray tubes up to and including 225 kV tube voltage by means of the line group fit method and evaluation of digital images.
The image quality and the resolution of X-ray images depend highly on the characteristics of the effective focal spot, in particular the size and the two-dimensional intensity distribution as seen from the detector plane.
This test method provides instructions for determining the effective size (dimensions) of nano and micro focal spots of industrial X-ray tubes. This determination is based on the evaluation of an X-ray images taken with line group test objects.
This document provides instructions for determining the effective size (dimensions) of nano and micro focal spots of industrial X-ray tubes for users in applications where the pin hole method of ISO 32543-1:2024 is not practical. This determination is based on the measurement of profiles of an image of line group test objects in different directions.
The use of the pin hole method ( ISO 32543-1:2024 ) requires the application of special pin hole cameras. This procedure describes, how the size of focal spots can be determined from line group exposures, which are easier to produce in comparison to pin holes and the related cameras.
Microfocus (1 µm ≤ spot sizes < 0,1 mm) and nanofocus tubes (spot sizes < 1 µm) have a significantly lower photon flux than mini and macro focus tubes (spot sizes ≥ 0,1 mm). Furthermore, pin holes (see ISO 32543-1:2024 ) with diameters in the nm and µm region are difficult to manufacture and will not permit sufficient photon statistics for digital imaging with the required magnifications. Nano- and micrometre pin hole methods would require very long exposure times for obtaining a sufficient SNR and CNR.