Effect of the shape and size of dosimeters on the response of solid state/EPR dosimetry

The influence of the shape and size of dosimeters used in solid state-EPR (SS/EPR) dosimetry on their response is reported. It is shown that for commonly used cylindrical (rod) shaped dosimeters of equal height, prepared of low (ε⩽3ε⩽3) dielectric constant materials, linearity between their volume and the EPR response is observed when their diameter varies between 3 and 5 mm. Further increase of the dosimeter's diameter is not recommended since the increased penetration of the dosimeter material into the electric component of the microwave field in the EPR cavity increases the dielectric losses and decreases the EPR response. In an attempt to improve the sensitivity of the SS/EPR dosimetry we have prepared and tested new, flat-shaped, dosimeters of low (ε≈2ε≈2) dielectric constant materials which were found to exhibit: (i) linear EPR response within 1–5 mm thickness; (ii) higher sensitivity than cylindrical dosimeters at equal sample volume; (iii) increased by ca. 270% EPR sensitivity at 5 mm thickness compared to the cylindrical dosimeters with the same diameter (ca. 1.7 times increased sample volume). Using flat shape dosimeters of suitable size provides 2.7 times higher EPR sensitivity of single estimation.