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Tube parameters: Calibration

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MarcoVogt edited this page Aug 21, 2020 · 2 revisions

Calibration measurements have been carried out at several distances from the tube using a calibrated PIN diode on a scanning motor stage.

For each tube distance, two diameters are provided: Full width at half maximum (50% peak intensity) and full width at 80% peak intensity.

The dose rate (in SiO2 has been measured at the maximum anode current of 50 mA and scales linearly with the current.

A few hints:

  • The reference point for the distance measurement is the bottom side of the aluminium collimator holder (fig. 4 "Zero position"). A distance value of 0cm corresponds to the smallest possible distance to the X-ray tube (touching the collimator holder).

  • To prolong the life of the X-ray tube, it is recommended to reduce the anode current as much as possible. In order to still achieve the desired dose rate, the tube distance can be reduced, as long as the DUT surface is fully covered.

  • Because of the heel-effect, the given diameter values are derived from the unaffected axis of the beam. An intensity gradient has to be expected along the tube axis, as shown in the beam profile plots.

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