A cryostat for x-ray reflection photography with a widely divergent beam

Abstract

The writers have carried out experiments on the action and behaviour of getters as used in the actual production of, for example, receiving tubes, power tubes, cathode ray tubes, mercury rectifiers and X-ray tubes. Initially the results obtained from the study of the flashing conditions of the getter and the effect of these conditions on the sorption of gases are presented. Results are given for the quantity of the gas sorbed during the first minute, the following four minutes and the successive 10 min, for getters which have been evaporated for 10 and 60 sec. The difference in the quantity of gas initially sorbed when using different times of flashing are quite remarkable in the case of N2 and H2. Due to this the quantity of gas sorbed can nearly be doubled by a rapid firing of the getter. This difference is less marked for O2 and negligibly small for CO and CO2. Similar studies have been made using rare gases; these studies have been helped by using the electron microscope to study the surface of the getter film. Studies have also been made on the influence of the distance between getter and condensing wall and hence of the condensing area of barium film. By examining cathode ray tubes, the dependance of the tube pressure and life on the conditions of flashing of the getter have been studied. In non aluminized picture tubes data are presented giving the most favourable angle of connection of the getter assembly to the electron gun. The modifications made to the cathode structure of X-ray tubes in order to obtain the most favourable conditions when using the getter are reported. Data on the pressure obtained under such circumstances are also presented. Subsequently a study is given of the gas sorption by barium, magnesium and titanium, in mercury vapour tubes. Finally there is a study of the influence of the getter on the emission from the oxide cathodes employed in mercury rectifiers made with an apposite apparatus.