Phase and group velocities of X-ray waves in the pores of track membranes

Propagation of electromagnetic hard X-ray waves inside cylindrical pores in thin polyethylene terephthalate (PET) track membranes is studied. Numerical simulation shows that both the phase and group velocities of the waves are constant over a significant part of the through pore length. In this case, the product of the phase and group velocities is equal to the square of the speed of light in vacuum. The paper analyzes the relationship between the established properties of wave velocities in pores and the properties of waveguide modes propagating in a hollow cylindrical waveguide with smooth walls. Possible applications of the observed phase properties of the pores for fabricating phase X-ray filters based on porous PET membranes are discussed.