PROPORTIONAL COUNTER

PURPOSE:To make it possible to detect radioactive rays without using any spe- cial filling gas by heating the positive electrode of a proportional counter. CONSTITUTION:A proportional counter 1 has an external electrode 2 which serves as its cathode, and a center electrode 3 inserted in the center of the external electrode 2. Lids 4a and 4b are provided at the both ends of the external electrode 2, which contains air, and one end of the center electrode 3 is fixed to a holder 6b installed at the center of the lid 4b via an elastic member 5 such as a spring or the like, and the other end is pulled out through a holder 6a installed at the center of the lid 4a to be connected to a signal pick-up terminal 7. The center electrode 3 is heated by a heating circuit 8 through which a proper amount of current flows from a battery 9 and a variable resistance 10. The secondary electrons generated by radioactive rays are gas-amplified even when air exists inside the external electrode 2, and so even a low energy radioactive ray can be measured.