Magnetic removal of electron contamination for 60Co panoramic gamma ray exposure—Investigations with CaSO4:Dy and LiF based dosimeters

Electron contamination from a sealed 60Co radiation source has been investigated comprehensively using a CaSO4:Dy based TLD badge and LiF crystals. It has been found that due to electron contamination, the thermoluminescence (TL) detectors exhibit over response which can be corrected by applying a magnetic field. It has also been found that for a source-to-dosimeter distance of 50 cm, the ratio of the TL readouts of the third to first discs of the TLD badge reduces from ∼1.5 to ∼1.00 after applying a magnetic field. Hence detectors which are sensitive to electrons as well as photons, and are capable of distinguishing them, can lead to an erroneous measurement. This happens because the contribution due to electron contamination interferes with pure gamma calibration. The study is helpful in establishing accurate calibration and appropriate correction factors for personnel monitoring carried out using CaSO4:Dy based TLD badge.