Micro-X-ray sources from flowing gases and PZT crystals

We report for the first time the observation of low intensity (~10⁵ photons/cm².s) soft X-rays (1-30 KeV) from flowing gases (N₂, Ne, He, and Ar) in capillaries and piezoelectric lead zirconate titanate (PZT) crystals at room temperature. The no-slip boundary condition of gas flow at the capillary boundary may lead to friction between the gas molecules and surface dangling bonds of SiO₂ causing chemical bond formation and breakage that generates soft x-rays. The X-ray spectrum of the gas was Gaussian with no characteristic emission lines. The spectrum shape was dependent on the velocity of the flowing gas with the x-ray mean energy and full-width-at-half-maximum being inversely related to each other. The PZT x-ray also did not have any characteristic emission lines, and its mean energy depended on the amplitude and the type of excitation voltage (square, sinusoidal and pulse) waveforms applied to the PZT.