Reflection of photons and azimuthal distribution of photoelectrons in a cylindrical beam pipe

In a cryogenic proton accelerator, such as the LHC, the creation of an electron cloud and generated heat loads resulting from electron bombardment are strongly dependent on the azimuthal distribution of created photoelectrons. In this context, photon reflection and photoelectron yield measurements have been performed using a beam line on the VEPP-2M storage ring. Six electrodes, covering the complete vacuum chamber perimeter, were mounted such that they could be suitably biased, and while one electrode was irradiated with synchrotron radiation the resulting electron current of all others could be measured. A detailed description of the experimental apparatus and the results of the measurements of photon reflection and the azimuthal distribution of generated photoelectrons are presented

Modified x-ray polymer refractive cross lens with adiabatic contraction and its realization

A refractive x-ray lens with reduced focal length, due to continuous reduction in the designed aperture over the length of the lens, is presented. The lens elements have refractive parabolic sidewalls like geometrical prisms, with a varying cross section over the length of the lens, in accordance with the x-ray propagation law. The focusing effect occurs directly in the lens due to the fact that the initial x-ray beam is directed toward the focal point, and due to the phase retardation caused by the refractive properties of the sidewall surfaces. An array of such adiabatic lens elements with different optical parameters, arranged in a number of rows, represented by polymer microstructures, has been produced using x-ray lithography. Preliminary testing of the lenses has resulted in a focal spot of 67 nm at a photon energy of 18.6 keV

Sub-micrometer Focusing and High-Resolution Imaging with Refractive Lenses and Multilayer Laue Optics

In this chapter we describe the fundamentals of X-ray optics with a particular emphasis on refractive and diffractive optics for high-resolution X-ray microscopy. To understand the physical limitations of X-ray microscopy and X-ray optics, a wave-optical treatment of the interaction of X-rays with the optical elements is needed. As all optics exploit elastic X-ray scattering in the form of refraction, reflection, or diffraction, these phenomena are reviewed, modeling matter by its complex index of refraction. The smallest probe sizes are reached at the diffraction limit. In that case, the focal spot size depends only on the numerical aperture of the optical element at a given wavelength. We discuss refractive and diffractive optics in view of optimal numerical aperture and give a few application examples in full-field and scanning microscopy