X-Ray Transition Radiation Applied to the Detection of Superhigh-Energy Particles

Preliminary measurements of the transition radiation in the x-ray region indicate that an average of 12 x-ray photons are produced by a single positron of 2-BeV energy traversing a stack of 231 thin aluminum foils. This number is large enough to indicate that it is feasible to use the x-ray transition radiation for the determination of the relativistic factor $\gamma$ rather than $\beta$ of superhigh-energy particles. Such an application may well provide a unique method for distinguishing monoenergetic particles in the superhigh-energy region.