In a recent variation of this method, Slatis uses systems of concentric rings. A tube consisting of an assembly of 22 parallel ring systems, each with 3 concentric rings, is stated to have a sensitivity 2.5-3.2 times that of a Geiger-Muller tube of the same size of the gamma radiation of Ra, Co-60 and Hg-203.

A tube similar in principle to the ones just described, has been in use in this laboratory since 1946. This tube consists of a series of parallel metal plates as the cathode and a series of parallel wires passing through holds in the plats, as the anode.

Used end-on as described below, the sensitivities to the gamma radiations of I-131, Co-60 and Ra were found to be two to three times higher than those given in Figure I.