The theory and design of an analyser for investigating the electron emission characteristics of surfaces in gases

Ordinary un-outgassed metal surfaces exhibit substantial electron emission (similar 10 5 electrons per sec) under the influence of electric fields of the order of 10 3 -10 5 v cm -1 . The electron emission from a workshop-turned nickel surface under a field of 5 × 10 4 v cm -1 is about 2 × 10 4 electrons per sec in air. Such emission rates can be of considerable importance in the operation of switches, contacts, high pressure gas insulation or the initiation of discharges in gases or in vacuo . This paper gives an account of the theory and design of an apparatus for measuring the rate of electron emission from given metal surfaces under given values of applied electric intensities. The method consists of applying a succession of N unit-function pulses to the metal surface acting as the cathode in a small parallel-plate gap, and the statistical time lag t s of sparking measured for each pulse. The rate of electron emission r is, in appropriate conditions, N /Σ t s ; Σ t s is counted and electronically recorded thus giving r directly. Some typical data found for metals - brass, steel, aluminium, nickel and molybdenum - with various surface conditions are given. The technological application of such data is indicated, and some physical problems in which the apparatus has been used are briefly discussed.