(19)
(11) EP 0 326 273 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
11.07.1990 Bulletin 1990/28

(43) Date of publication A2:
02.08.1989 Bulletin 1989/31

(21) Application number: 89300425.9

(22) Date of filing: 18.01.1989
(51) International Patent Classification (IPC)4: H01J 1/15
(84) Designated Contracting States:
AT BE CH DE ES FR GR IT LI LU NL SE

(30) Priority: 26.01.1988 GB 8801633

(71) Applicant: EEV LIMITED
Chelmsford, Essex, CM1 2QU (GB)

(72) Inventor:
  • Pickering, Alan Hugh
    Chelmsford Essex (GB)

(74) Representative: Loven, Keith James et al
GEC plc Patent Dept.(Chelmsford Office) GEC-Marconi Research Centre West Hanningfield Road
Great Baddow Essex CM2 8HN
Great Baddow Essex CM2 8HN (GB)


(56) References cited: : 
   
       


    (54) Directly heated cathodes


    (57) A directly heated cathode for generating an electron beam along an axis (A) comprises two nested, dish-shaped conductors (4,5) on the axis joined electrically and mechanically on the axis by a spot weld (7), and supported by respective co-axial cylinders (1,2). A heater current supplied by the cylinders (1,2) flows between the conductor rims by way of the spot weld (7), and does not interfere with the electron beam generated by the outer conductor (5).







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