Radiation Dosimetry by Dyed Polymethyl Methacrylate
1976 Volume 25 Issue 5 Pages 265-270
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1976 Volume 25 Issue 5 Pages 265-270
A dyed polymethyl methacrylate (PMMA) called ‘Sumipex 400’, which is commerci ally available, has been irradiated by 60Co γ rays and 35 MeV pulsed electron beams from a linear accelerator and the radiation-induced optical absorption has been investigated. In the irradiated dyed PMMA, increased absorption was observed in the region of 600 nm to 1000 nm. The difference between an absorption curve of normal PMMA and that of irradiated PMMA has two peaks at 609 nm and 653 nm. However absorption curves obtained by both 60Co γ rays and electron beams exhibit the similar shape.
The change in optical density at 653 nm is a linear function of the dose, up to about 1 Mrads. The linearity of change in optical density for the dose is lost when the dose exceeds about 1 Mrads. But if the calibration curve is available, this technique is useful for measuring irradiation doses between 105 and 4×106 rads within 2% fading during less than 24 hours after irradiation.
This method has been also applied for measuring spatial distributions of electron beams from the linac, and reasonable results have been obtained. As a conclusion, it was experimentally shown that the radiation-induced optical absorption in the dyed PMMA had been found to be a convenient and inexpensive method of radiation dosimetry.
