Abstract
Geiger-Müller counters suffer from two disadvantages: (a) the thickness of the walls limits the radiation which may be studied to that above a certain minimum energy, and (b) their shape and the thickness of the walls prevent complete cover being obtained in anti-coincidence work. A new type of counter is described in which these difficulties are overcome. Preliminary tests give a minimum value of 89 per cent for the efficiency, and absorption experiments show that 85 per cent of the particles counted have an energy less than 1.5 × 106 eV.