| Radiochromic film (RCF) is a kind of organic function films. The dyes painted on the the surface of the backing material. When RCF is exposed to ionising radiation, colouration occurs, which does not require any latent thermal, optical or chemical development or amplification. This colouration is due to an attenuation of some of the visible light passing through the film and resulting in a greying of its appearance. The reduction in light passing through the film is a measure of its optical density (OD). In this paper, a important theorem is that the dose to the film is reflected in the resulting optical density of that film,So we can get the irradiation dose according to the optical density.Using this characteristic, we can preparation two-dimensional (2D) or three-dimensional (3D) solid dose meter, has wide application value.In this paper, diacetylene was used as the dyes of the radiochromic film dosimeters and it developed.We had overcomed the difficult, optimized the technical process. According to the characteristics of gelatin, we designed a device to prepered gelatin - film dosimetry. also, a lot of factor infulence the dosimetry's performance,such as raw material ratio, the solubility temperature, solution viscosity, coating temperature, crosslinking agent and the influence of ethanol mixed film factors.The basic characteristics of the geltin-film dosimetry tested by 6OCoγ-ray and as fellows:1,In this paper,we prepered gelatin-film dosimetery,Commercially available gelatin was used as the matrix,while diacetylene was used as the dyes of the dosimeters.2,Colourles transparent radiochromic films prduces a permanent blue colour upon irradiation. since of the radiochromic layer contains micro-crystals of a monomer,this layer undergoes partial polymerization by the ionising radiation and becomes darker with more and more absorbed dose. Two absorption peaks occur in the visible waveband,these being at 640nm and 590nm,A small shift in the position of these peaks occurs with the delivered absorbed dose. The dose response of the gelatin-film dosimetry at specific wavelengths of determination,the results show that a large variation in sensitivities achievable through analyses at different wavelengths of the spectra. The maximum sensitivity is produced at the maximum absorption peak of 640nm.3,There is a good linear relationship between optical density(OD)and absorb dose ranging from 50mGy up to 1Gy.4,The effect of dose rate of delivery on the response of gelatin-film has been test,it has been found that the film is relatively dose-rate independent from the range of 1mGy/s to 5mGy/s.The applied total dose delivered was 1Gy and the net densities differ by less than 2% from the mean.At the same time, dose fractionation effects are absent for gelatin-fim.it is need to undertake calibration to get accurate result.5,The gelatin-film very little dependence on relative humidity during irradiation but there is a marked temperature dependence.At a dose of 1Gy,the gelatin-film show a 5% increase is response when the irradiation temperature is increased from 20～30℃, at highter temperature(between 30～55℃)the response increase due to arise in irradiation temperature by～1.6% per℃,specially when the temperature up to about 60℃, the image changes abruptly from blue to red.6,The active components in the geltin-film is radiation-sensitive monomer,Polymerization proceeds after the reaction has ceased causing a post-exposure density growth.The film becomes relatively stable after 24h(Environment temperature:25℃, HR:40%), and heat can speed the process(<4h).the geltin-fim can storage in the dark envirement long time.it sensitive to daylight,Fluorescent light and ultraviolet.7,the sensitive lay mainly construction of gelatin and dyes,it very hard to mix together. so there is a bad unifrom between batch to batch,but per batch,the net densities differ by less than 1% from the mean. |
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