Radiochromic films

Radiometer for spot and flood cures. (Courtesy of Dymax Corporation.) 

Obviously, the user has a large selection of instruments, each of them having a different function. The selection depends on what the user wants to measure and for what purpose. 

In process design, the main objective is to optimize the cured properties of the finished product. To that end, the following conditions have to be established and quantified  

fhese measuremenfs provide quanfifafive information abouf fhe critical paramefers used in fhe process, and help esfablish the limits within which the process is successful, or the so-called process window. 

Once the process window is established, the goal is to maintain the operating condition within the established limits. This is often referred to as process control. The primary purpose of process control is to monitor the process to get a feedback by means of on-line radiomefric measuremenfs and fake action to keep it within the established limits. Process monitoring has to verify thaf fhe key process variables remain wifhin fhe specified limits, and to interpret changes in the exposure conditions to help maintain control. Once established, proper measurements are invaluable in monitoring the condition of the UV lamps and determining when they have to be maintained or replaced.  

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Additional information concerning the fast electron distribution can be obtained in such experiments by direct measurement of forward escaping electrons using a calibrated stack of radiochromic films [52] that can provide information of the angular and energy distribution of fast electrons. These measurements were performed in the same experiment described above [31] and the summary of those measurements is reported in Fig. 7.10 and reveal a distribution that is consistent with a relativistic Maxwellian distribution with a characteristic temperature of 160keV. 

Figure 8.6 shows a typical cross section of the 18 MeV component of the electron beam, after de-convolution of experimental data from the radiochromic film-stack device SHEEBA [76],... 

Radiochromic films Spectrophotometers Dyed and clear plastic films ... 

Other commercially radiochromic films are poly(methyl methacrylate) (PMMA), cellulose triacetate (CTA),i polyamide (nylon) films, poly(vinyl butyrate) with pararosaniline and p-nitrobenzoic acid, and alanine films. The CTA films are undyed PMMA films are available undyed and dyed (red and amber). ... 

Essentially, a calorimeter measures absorbed dose in terms of the radiation-induced temperature rise in the calorimeter core connected electrically to the outside. The dose to the dosimeter being calibrated is related to the associated calorimeter reading of the net temperature rise. These calorimeters are used as reference dosimeters for high-energy electron beams (2-12 MeV) and also for small references and routine dosimeters (pellets and radiochromic films). 

ISO/ASTM 51275 Standard Practice for Use of Radiochromic Film Dosimetry System... 

Radiochromic films spectrophotometry microdensitometry dyed plastics, polydiacetylenes... 

Dosimeters that are sufficiently small, such as thin radiochromic films and alanine pellets, can readily be calibrated against the calorimeter, by irradiating in tandem (with a suitable radiation monitor) while encased in a phantom material that is identical in size, shape and substance to the calorimetric absorber. The main appreciable correction that is required is the ratio of mass energy-absorption coefficients of the two materials (in the case of photon irradiations) or the ratio of mass collision stopping powers of the two materials (in the case of electron beam irradiations) (McLaughlin et al., 1989). 

Lavalle, M., Corda, U., Fuochi, P.G., Caminati, S., Venturi, M., Kovacs, A., Baranyai, M., Safrany, A., Miller, A. Radiochromic film containing methyl viologen for radiation dosimetry. Radiat Phys. Chem. 76, 1502-1506 (2007)... 

Radiochromic film dosimeters. Many polymer-based film dosimeters have been developed containing various types of dyes, whose color or depth of color changes during irradiation. Certain leucocyanides or leucomethoxides of triphenylmethane dyes are widely applied in the dose range of 10 -10 Gy (McLaughlin 1974,1977, 1985, ISO/ASTM 51275). 

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