Polymer electrolyte membranes for use in fuel cells are produced by first graft polymerizing acrylic acid derivatives or vinylketone derivatives as monomers on polymer substrates and by then performing selective conversion to a sulfonic acid group of hydrogen atoms on the carbon atom adjacent to the carbonyl in the ketone or carboxyl group on the graft chains. The device further includes a thermally activated initiation device, and a transfer line coupling the thermally activated initiation device and the explosive cutting charge. 0 is satisfied, f1 being the focal length of the first lens group and f2 being the focal length of the second lens group.