Simulation of a Novel Dosimeter Based on Electrical Characteristics of Polymethyl Methacrylate- Carbon Nanotube Composite

Combination of carbon nanotubes with polymers in an especial weight percentage called electrical percolation threshold, leads to a sudden increase of several orders of magnitude of the electrical conductivity of the polymer-carbon nanotube composite. In the present research, considering these characteristics, the idea of using Polymethyl Methacrylate-Carbon Nanotube composite as an active dosimeter is exhibited. One of the factors affecting the response of this type of dosimeter is the variation of electrical resistance in the composite due to absorption of radiation. For investigation of dosimetric parameters of this composite in different dose rates, the COMSOL software and finite element method were utilized. In this simulation, the electrical current density of PMMA-CNT composite with a thickness of 10µm under a constant voltage of 3 V in different dose rates for 2 min was calculated for the samples having different weight percentages of carbon nanotubes adjacent to the electrical percolation threshold region, namely 0.17, 0.19 and 0.30. The value of the absorbed dose was calculated through the product of the dose rate by the irradiation time. Linearity of the dose response in the range of 400 mGy to ~3 Gy in the diagnostic and therapeutic dose levels could be considered as a positive factor for dosimetry applications of this composite material.