Coaxial anode for background suppression in X-ray proportional counters.

We have devised, constructed, and tested in flight a scheme which permits the ends (near the anode seals) as well as the bottom and sides of an X-ray astronomy proportional counter to be protected by anticoincidence guard counters. A rocket-borne test has shown that the non-X-ray background is reduced by an additional factor of about 30 when the end guard counter feature is added.