A cathode-ray oscillograph with high-speed drum camera rotating in vacuo

A description is given of an all-metal oscillograph using a cold cathode and high accelerating voltage. It is capable of recording directly on a photographic film moving in vacuo at a speed of 100 metres per sec. Details are given of the construction of a vacuum drum camera and of the gland system by means of which a shaft running at 3 000 r. p. m. is brought from atmospheric pressure into a vacuum of 5 x 10¿5 mm of mercury. The design of the rotor (63.6 cm in diameter) and the method of fixing and retaining the film (125 mm in width) are described. The construction of the cathode-ray oscillograph is briefly outlined, and a zero-shifting device, by means of which a record 10 m long is obtained from the drum of 2 m circumference, is explained. The vacuum technique employed to obtain the low pressures required in the short times necessary for routine testing is described in some detail. Some records illustrating the capabilities and possible uses of the instrument are given.