GB1132016A - Improvements in or relating to magnetic field correction means in electron dischargetubes - Google Patents

Abstract

1,132,016. Discharge apparatus. SIEMENS A.G. 15 Nov., 1965 [16 Nov., 1964], No. 48353/65. Heading H1D. An electron gun surrounded by a cylindrical magnetic shield 4 having a fixed iris 5 of magnetically soft material at the end through which the beam passes further includes a metal sleeve 11 closely surrounding, and anchored to, the shield 4, which sleeve bears at its periphery, at the end adjacent the iris, a substantially tangential plate 12 of soft iron, whereby rotational asymmetry in the residual magnetic field at the gun cathode may be compensated, during the manufacture of the tube, by axial and rotational adjustment of the sleeve before the latter is anchored to the shield 4. As described, the gun is incorporated in a travelling wave tube having a periodic permanent magnet focusing system, the magnetic shield 4 being held central by a tube 6 engaged with a shoulder ring 7 which supports the central portion 8 of the discharge tube. The plate 12 is triangular in shape, Fig. 3, and is spot-welded to the sleeve 11, which is axially slit to permit adjustment with respect to the shield 4 before it is spotwelded to the latter. In an alternative arrangement, the assembly of shield 4 and sleeve 11 may be mounted outside the tube envelope.