Multi-wall carbon nanotubes as x-ray waveguides and PXR and CTR source

ABSTRACT Our theoretical calculations show that multi-wall nanotubes (MWNTs) can serve as x-ray waveguides. Two types of waveguiding exist based either on Fresnel or Bragg reflections of x-rays from nanotube walls. Moreover,fast electrons propagating through MWNTs can emit "channeled transition (CTR) or parametric x-ray (PXR)types of radiation with much greater intensity than in ordinary crystals. Keywords: Nanotubes , diffraction, channeling, waveguides, x-ray radiation 1. INTRODUCTION Application of hollow glass capillaries for x-ray guiding due to multiple small-angle Fresnel reflections is wellknown since long ago. For example, 70 years ago Nahring' used straight 100 m wide and 8 cm long capillaryto reduce exposure times in Laue x-ray diffraction patterns. The interest to capillary x-ray optics was revived in80s when bent and tapered capillaries were considered. It was shown theoretically2 how an x-ray beam can befocused using multiple bent planar waveguides. Soon it was shown experimentally3 that x-ray beam can be indeedeffectively deflected at angles much higher than the Fresnel angle using flexible capillaries. Tapered planar x-raywaveguide with variable profile was investigated in4 both theoretically and experimentally. It was demonstratedthat x-ray beam with low enough primary angular spread can be compressed to sub-micron dimension without