Effects of perturbing magnetic fields on the performance of photoelectronic sensors

Photoelectronic sensors are all susceptible, to a greater or lesser degree, to the influence of perturbing ambient magnetic fields. Theoretical and experimental results are presented for the effects of axial and transverse magnetic fields on the various types of image intensifiers (including microchannel plate devices), TV camera tubes, and photomultipliers. The most immediately apparent effects are image displacement and loss of focus; additionally, changes in gain and certain other more subtle effects may be encountered. Numerical and graphical or nomographic methods for determining the magnitudes of the major effects in the different electron-optical systems at various voltages are provided, and electrode supply tolerances may be obtained therefrom. The nomographs can also be used to derive the focus conditions for magnetically focused systems. Interpretations of previously unexplained phenomena in the behavior of microchannel plates are also presented.