IMPROVED ACCURACY OF EPR DOSIMETRY USING A CONSTANT ROTATION GONIOMETER

Grains of sufficiently small diameter will theoretically result in an isotropic EPR response which is independent of sample orientation. In practice, use of such small grains may present problems of altered sen sitivity and newly induced paramagnetic centers. Additionally, the eff ect of anisotropy is increased with increasing microwave power. This p laces limits on the effectiveness of the differential power method whi ch allows determination of cumulative dose without the need for a zero background signal. The use of a constant rotation goniometer reduces the effect of anisotropy, making measurements at all microwave powers, and particularly the higher powers, significantly more accurate. Sinc e the organic and the mineralized components of the EPR signal are bot h effected by anisotropy, this procedure may well result in reduced li mits of detection. (C) 1997 Elsevier Science Ltd.