PURPOSE: To enhance the mechanical strength of a dosimeter element and to apply said element to measurement of a dose distribution, etc., by providing a cord in the center of the element.

CONSTITUTION: A resin compsn. 1 contg. 10W1,000pts.wt. alanine crystal powder is continuously extruded and is applied on the outside circumference of such a cord 2 in which the quantity of the free radicals formed to the cord by irradiation of ionizing radiations is decreased to ≤1/5 the quantity of the free radicals formed in the alanine crystal by the similar irradiation or the free radicals formed to the cord are unstable and are attenuated in a short period of time at room temp. to 1/10 the quantity of the free radicals in the alanine crystal. This molding 3 is cut to, for example, 3cm length and is used as the dosimeter.