Resonance Transition Radiation as a Tunable X-Ray Source

A shift in the resonance frequencies of transition radiation from a 4 GeV positron beam incident on a stack of 19 ¿m mylar foils has been observed when the angle ¿t between the beam and foils was set at 40 and 60 degrees. Spectra were the same as from a beam incident normally on a stack with foil and gap thicknesses increased by a factor of 1/cos¿t. Simple design formulas are presented fol constructing a tunable X-ray source with variable bandwidth.