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Calibration of the X-ray system is periodically made with a pre-calibrated PIN diode. Two such diodes have been procured at the time of purchasing the X-ray machine (in 1997) and are still used today.

The mechanical configuration of the irradiation system, in particular for what concerns the support for a collimator on the X-ray tube, has been modified several times since the initial acquisition of the system. Most often, this was due to the need for reaching increased dose rates - this in turn driven by the high levels of TID foreseen for the upgraded LHC tracking detectors. The most recent modification, in 2013, removed all mechanical support for collimators and for the alignment laser diode (which has been mounted in a different position) so that the DUT can now be put at the minimum possible distance from the focal point of X-ray production. Dose rates of the order of 9Mrad/hour can be reached with reasonable tube settings (voltage and current). In this occasion, calibration was also made with another and independent method based on dosimetric films. The measured dose rate was in rather good agreement with the one obtained from the PIN diodes, confirming that overall the dosimetry provided to users is good to within +-20% (or better).

A summary of the most recent calibration and some additional information about the configuration of the system can be found in the report at this link. This report has been updated in January 2017 when the tube ceased to function after about 16,000 hours of reliable operation and was replaced with another one.






Last modified: 31 March 2014