Pressure dependence of X-rays produced by an LiTaO3 single crystal at the pressures of 1-20Â Pa

The energy spectra of X-rays produced by an LiTaO3 single crystal have been measured at pressures of 1-20 Pa. The energy spectra showed that the endpoint energy and the amount of X-rays gradually increased with the decrease of pressure at 5-8 Pa and abruptly increased around 4 Pa and below. A maximum endpoint energy of 70 keV was obtained using the LiTaO3 single crystal with 5 mm thickness at a pressure of 3 Pa. The change of X-rays produced by the LiTaO3single crystal was discussed in relation to the breakdown potential at the pressures.