Film Badge Foma ( Surveymeter/ Survey Meter/ Pendose/ Pen Dose/ Dosimeter)

PERSONAL MONITORING FILM FILMS FOR PERSONAL DOSIMETRY General information Foma PMF is a set of two films intended for personal dosimetry of gamma radiation, x-radiation and electrons: Foma DF10 is a high speed film double coated on a blue coloured polyethylene terephthalate base. Foma DF2is a lowspeed ( emergency) film. Classification: Personal photographic dosemeter ISO 1757 -3-W-2.The films are supplied in the 3 x 4 cm size ( according to ISO 3665) . One package contains 150 pieces of DF10+ DF2 film sets packed in light-proof and moisture-proof packing. The films are intended for use with dosimetric film holders. Depending on the processing method they can be used for measurement of personal dose equivalents of photon radiation in the energy span from 15 keV to 6 MeV in the range from 0.1 mSv to 2 Sv. Darkroom light Due to their high speed, the films should be processed under indirect red safelight ( recommended filters Agfa R1 or R4) using a 25 watt bulb placed at a distance of at minimum 75 cm from the film. Processing Dosimetric Foma films can be processed using the powderx-ray developer Foma DP with Foma DP-R replenisher and rapid fixer Fomafix P with replenisher. Application of a mildly acidic stop bath is recommended between developing and fixing. Film processing is performed at temperatures from 19 to 21 C. Development time depends on developer concentration, temperature and on the intensity of solution exchange in the film vicinity. It must be determined experimentally. Typical values are between 5 and 7 minutes. Confectioning The film is supplied in the 3 x 4 cm size ( according to ISO 3665) . One package contains 150 pieces of two sheet moisture -proof packets from plasticized PVC. Dosimetric characteristics of the films and their optimisation The basic dosimetric characteristic is the optical density ver sus ionising radiation dose curve of the film. As opposed to the visible radiation, this curve is linear with a dose from the lowest doses. If the films are to be used for personal dosimetry purposes, the lowest measurable dose should be approximately 0.1 mSv according to international recommendations ICRP 60 and ICRP 75. This can be achieved with the films Foma DF10 experimentally by an appropriate selection of developing conditions. The procedure is as follows. The set of personal monitoring films is expo sed to gamma radiation ( emitter Cs -137 or Co-60) with kerma in the air in the range from 0.1 mGy to ca. 40 mGy. These films are then developed together with films that were not exposed to the radiation ( fog or background) in given equipment for a varietyof time periods ( approx. from 5 to 7 minutes) . The determination of the optimum development time is then based on the condition that for the high speed film DF10 the optical density of background ( fog) increased by 4 Ã of the background must correspond wit h kerma in the air lower than 0.1 mGy ( read from the gamma radiation calibration curve) . The lowest measurable dose is 0.08 mSy ( ± 30 % ) and the measurement uncertainty is better than ± 15 % for values higher than approx. 0.2 mSv. The requirements of the recommendations ICRP 60 and ICRP 75 are thus met by a considerable margin ( uncertainty from -33 % to + 50 % in annual dose limit) . The corresponding curve forx -radiation with energy 49keV ( approx. 70 kV + 0.5 mm Cu) is shown in fig. 2. Calibration curves for emergency films Foma DF2 are shown in fig. 3 and 4 for gamma radiation andx -radiation with maximum efficiency ( 49 keV) respectively. These curves were obtained under developing conditions determined for high speed films Foma DF10 as optimum. It is evident from figs. 1 and 3 that the ranges of gamma radiation doses overlap with a considerable margin and the upper limit of the measuring range is above 1 Gy. If the developing time is reduced by 50% , it will be possible to use Foma DF2 filmsf or measuring the doses up to at least 2 Gy. However, the lower limit of the measuring range will also be increased. Energy dependence of Foma films is shown in fig. 5. As a result of this dependence the speed of DF10 is approximately 17x higher forx-radiation with energy 49 keV ( ca 70 kV + 0.5 mm Cu) . This fact is apparent from the comparison of fig. 1 and fig. 2 ( or fig. 3 and fig. 4) . For these reasons, in film dosimetry this energy dependence must be compensated for using some of the published methods. Filtration analysis method yields very good results in the whole energy span 15 keV – 6MeV as it is also shown in fig. 5. Fading, i.e. decrease in optical density with time after exposure to radiation, does not exceed 10% during 3 months in the case offilms Foma DF10 provided that the ambient temperature is not higher than 30° C and relative humidity does not exceed 60% . Fading can be compensated for by an appropriate selection of irradiation time of the calibration film. Storage The method of storage is an important condition for the preservation of the dosimetric parameters of the films. A temperature of about 10° C and relative humidity not exceeding 60% are recommended. The films must be outside the reach of the effects of ionising radiation and aggres sive vapours.