1959 年 28 巻 8 号 p. 445-450
In order to eliminate undesirable electrical oscillations of a travelling wave tube, inside of the helix-supporting pipe is treated with Nesa-coating. For this purpose, several kΩ/_??_ is required as the surface resistance of the film.
Nesa-coating is performed by the following processes: Fine drops of Nesa-solution, that is aq. HCI containing SnCl4 and SbCl3, are sprayed through the inside of the helix-supporting pipe previously heated above 420°C. The ratio between the constituents of Nesa-solution has considerable effects on the surface resistance of the coated film, and the higher the temperature used for coating and the longer the time spent for spraying, the higher the conductivity of the film. Well stabilized film is obtained if after coating the pipe is washed with aq. HCl and water, fired at 770°C for 30 min. in air and heated at 650°C for 1 hr. in vacuum.
The mechanical stability of the film thus obtained proved to be excellent and the microwave characteristics satisfied the requirement in the use of travelling wave tube. In addition, these films showed high durability against electron bombardment, heating and corrosion by acids, but were only affected by gases, e. g. H2 or N2, at high temperature.