What is the difference between a SSDL and a factory calibration?
The factory calibration is the standard calibration performed in the Dosimetry Laboratory in order to assign a chamber a calibration coefficient.
The chamber is aligned with an alignment stick. One calibration measurement is carried out. Due to the measurement setup and just one measurement higher uncertainties of the calibration coefficient come up. This calibration is meant for chambers which will be used for routine relative dosimetry measurements (e.g. Scans in the IBA Blue Phantom 2/ Smartscan). Example - Accuracy: N(D,W) = 2.2 %
The SSDL calibration is internationally recognized by law and traceable to the primary standards. A calibration coefficient with a high accuracy is achieved by this type of calibration.
The chamber set up with a laser. Two calibration measurements are performed by two different people with two different electrometers to ensure highest achievable precision. This calibration should be the choice for chambers which are used for clinical reference dosimetry (absolute point measurements, beam calibration etc). Example - Accuracy: N(D,W) = 1.0 %
Comparison of uncertainties of SSDL and factory calibration: