X-ray Spectra from a Brass-target Plasma Triode

Abstract

In this paper, we describe a recentlyd e v elopedt able-top plasma x-ray generator utilizing a brass-target triode, which we used in preliminary experiments for the superposition of K-series characteristic x-rays in weakly ionized plasma and for producing their higher harmonics. In the plasma flash x-ray generator, a 200 nF condenser was charged, and flash x-rays were produced by discharging. The x-ray tube was a demountable triode with a brass target containing 65% copper and 35% zinc by weight, and a turbomolecular pump evacuated air from the tube with a pressure of 1 mPa. Target evaporation led to the formation of weakly ionized linear plasma, consisting of metal ions and electrons, around the rod target, and intense characteristic x-rays were produced. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was 15 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities of zinc Ka, copper K,8, and copper K/3 lines increased substantially. On the other hand, hardly any zinc KP lines were detected. In particular, we confirmed the irradiation of the second unsharp harmonics of the fundamental Ka lines of copper and zinc. The x-ray pulse widths were 700 ns, and the time-integrated x-ray intensity was 1.2 mGy at 1.0 m per pulse with a charging voltage of 50 kV.