Observation of X-rays generated by relativistic electrons in waveguide   target mounted inside a betatron
  In this work we have observed x-ray emission from x-ray waveguide radiator excited by relativistic electrons. The experiment carried out at Tomsk betatron B-35. Such new type stratified target was mounted on goniometer head inside the betatron toroid. The target is consisted of the W-C-W layers placed on Si substrate. The photographs of the angular distributions of the radiation generated in the target by 20-33 MeV electrons have shown the waveguide effect of the three-layer structure on x-rays generated in the target. The effect proved in an angular distribution of radiation as an additional narrow peak of guided x-rays intensity inside a wide cone of usual Bremsstrahlung. 
V. V. Kaplin, V. V. Sohoreva, S. R. Uglov, O. F. Bulaev, A. A.   Voronin, M. Piestrup, C. Gary