Patent ID: 8519608
Filing Date: 2013-08-27
Classification: B82Y,H01J

Abstract:
1. An electron source comprising: an insulator; two conductive terminals arranged spaced apart on said insulator; two long filaments mounted between said conductive terminals; and a needle cathode attached to said two filaments and having an electron emitting portion; the cross sectional shape of said two filaments in a direction perpendicular to an axial direction having a long direction and a short direction; the maximum length in the long direction being at least 1.5 times and at most 5 times the maximum length in the short direction; and said two filaments being mounted such that the long direction of the cross sectional shape of said two filaments have has an angle of ±10° with respect to the normal to the plane formed by three points which are the position of said cathode and the two positions where said filament is attached to said conductive terminals, wherein the angle between said two filaments is at least 30° and at most 120°.