Spectrometer procedure EN 12544-3:

Introduction/Application range

At RÖMATEC the high-tension of a X-ray tube is determined by a spectrometer procedure according to EN 12544-3. The non-invasive voltage metering uses the energetic allocation of the X-ray spectrum. This technique is applicable with all kind of X-ray systems, this means even then, when for example the voltage divider procedure is not applicable. According to the standard the range from 10 to 500 kV is covered. It is the objective to assure the correlation between the current high-tension and the value shown in the display of the controller. For that purpose only the border energy is measured and not the complete energy spectrum.

Test method

A energy dispersive photon detector is positioned into the collimated directional X-ray beam of the X-ray tube to be tested. The electric pulses are recorded with the aid of a multi-channel analyser.

The energy range of the detector has to be at least 20 % higher then the energy to be expected from the X-ray unit. In order that the detector is only exposed to the direct beam, it has to be protected against possible noise and leakage radiation in the best possible way. The soft radiation elements of the spectrum have to be weakened with the help of Al, Fe, Cu and Pb filters. The thickness of the filters, the diameter of the collimated beam and the distance between X-ray tube and detector have to be chosen that way, that the detector system features a linear performance and the same way a "Pile-up" situation (counting rate to high) is avoided. The multi-channel analyser should have a channel resolution of 0.23 to 0.27 keV. The energy range of the detector should transcend the energy to be expected by at least 20 %. Calibration of the system has to take place with the help of the characteristical lines of the radionuclide Ba133.

The result of the measurement, this means the border energy of the X-ray system, is determined through that point where the best fit straight line through the high-energetic flank of the spectrum and the energy abscissa intersect each other.