Large-area transition radiation detectors for cosmic-ray observations in space

The characteristic dependence of x-ray transition radiation on the Lorentz factor of the parent particle can be utilized in cosmic-ray observations on balloons or in space in order to discriminate between relativistic electrons and hadrons, or to determine the energy spectra of heavy cosmic-ray nuclei at very high energies. To obtain statistically meaningful results, exposure factors of the instruments of the order of 100 - 1000 m2sr days are essential. While the intrinsic weight of transition radiation detectors is low, this requires novel approaches and precludes the use of heavy pressurized containers for the instrument. We have developed a system using large arrays of xenon filled proportional tubes as detectors which can operate in a zero pressure environment. We shall discuss this design and present results from prototype evaluations. Finally, we shall describe the capabilities of a practical detector system that will measure the elemental composition and individual energy spectra of heavy cosmic ray nuclei up to energies around 1015 eV.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.