Influence of magnesium chloride on the dose–response of polyacrylamide-type gel dosimeters

We investigated the effect of magnesium chloride (MgCl 2 ) on the nuclear magnetic resonance dose–response of polyacrylamide-type (PAGAT, NIPAM, and VIPET) gel dosimeters containing acrylamide, N -isopropylacrylamide, and N -vinylpyrrolidone as a monomer, respectively. The dose-transverse relaxation rates (1/ T 2 = R 2 ) obtained from magnetic resonance imaging data revealed that a substantial increase in the dose– R 2 response occurred as the concentration of MgCl 2 in the gel dosimeters increased. The sensitivity of the PAGAT gel with 1.0 M MgCl 2 was found to be approximately one order higher than that of the same gel without MgCl 2 . In addition, the water equivalences of the gels with MgCl 2 were evaluated over a wide range of photon energies. The results indicated that MgCl 2 acts as a powerful sensitizer to radiation-induced free-radical polymerization in polyacrylamide-type gel dosimeters, but does not interfere with the desirable properties of basic polyacrylamide-type gel dosimeters (i.e., the dose rate and dose integration).