Papers by Author: Shinji Fukao

Abstract: X-ray emission using pyroelectric crystals is intermittent, and has low intensity and stability. One of the factors for low stability is related to creeping discharge, due to the accumulation of surface electric charges that change in response to the temperature. The time dependence of the net amount of electric charge was investigated by changing the cycle period of the crystal temperature. The stability of the X-ray emission is demonstrated to be strongly dependent on the temperature cycle period.

Abstract: The mechanism of pryoelectric-induced X-ray emission in LaTiO₃ crystals is discussed. It is suggested that electrons which contribute to the X-ray emission were generated around and close to the crystal and were emitted from the z surface. The poor reproducibility was found to be due to a creeping electrostatic discharge. It is speculated that one of the factors of the discharge is the accumulation of positive charges on the z surface.

Abstract: Three and six LiTaO₃ single crystals are used to achieve continuous emission of high-intensity X-rays. Furthermore, the interaction between X-rays and the case of the X-ray source is used to generate electrons. X-rays were emitted continuously and fluctuations in the count rate were reduced when three or six crystals were used. Moreover, the X-ray intensity increased and the number of electrons generated by the above-mentioned interaction increased with increasing number of crystals.

Abstract: X-ray radiation using pyroelectric crystal is intermittent and the X-ray intensity is low and unstable compared with a conventional X-ray radiation method, such as X-ray tube. It is expected that the X-ray intensity becomes stable if electric field intensity and supply of electron are stable. In this study, to use X-ray radiation equipment as an electron source, tandem-type X-ray radiation equipment which is composed of two LiNbO3 single crystals polarized in a z-axis is proposed. When the temperature gradient for each crystal was the same, the X-ray intensity became approximately 6 times higher at a maximum. When the temperature gradient for each crystal was reversed, the period of X-ray radiation became approximately two times longer and the X-ray intensity became approximately 20 times higher at a maximum. Moreover, the stability of X-ray radiation for the repetition of temperature could be improved.

Abstract: The gas pressure and the types of ambient gas dependence of X-ray intensity were investigated for LiNbO3 single crystals polarized in the c-axis direction at pressures of approximately 1 to 30 Pa. The integrated X-ray intensity showed a local maximum value at the pressure Pmax. Pmax moved to the high-pressure side in the ambient with a large first ionization energy. Pmax was proportional to the Boltzmann factor using the first ionization energy of each ambient gas molecule. The X-ray intensity was approximated using the quadratic function, which was convex upward for the pressure. It was found that one of the causes of the decrease in X-ray intensity on the pressure side higher than Pmax was the adsorption of positive ions on the crystal electric surface.

Abstract: The radiation of X-rays using the electric charge generated by a temperature change of a LiNbO3 single crystal has been investigated. When the LiNbO3 single crystal was placed in a conductive cylindrical pipe made of graphite, aluminum or copper, the photon flux of the radiated X-rays was dependent on the type of conductive material used. Depending on the type of materials on which the crystal was placed, the photon flux of the radiated X-rays increased with decreasing work function of the material.