Investigation of Electron Emission from Superconductors

Electron emission from a superconducting tin surface at low electric field strengths was sought for. The sample was the cathode of an electron gun, which was focused on a NaI(Tl) crystal. A photomultiplier tube and associated pulse-counting equipment was used as a detector for light pulses. The measurements indicate that at a field strength of 570 v/cm the order of magnitude of such emission is less than 100 electrons/${\mathrm{cm}}^2$-sec, under the surface conditions used.