Symmetrical Prism Research Articles

The Virtual Optics of the Median Plane of Axially Symmetric Magnetic Prisms

The angle between the asymptotes of a ray is developed as a power series in its impact parameter about some value which characterizes the `principal ray' When this value is zero, the principal points of the equivalent lens coincide at the axis of symmetry; in all other cases it is `thick' The focal length is here associated with the coefficient of the linear term, the transverse aberrations with those of the higher terms The quadratic aberration vanishes for a wide range of relative Hρ if the principal ray is suitably chosen. Foci with quadratic aberration are intercepts of the caustic curve, whose cusp lies at the cubic focus The dependence of aberration upon magnification and the conditions in which the cubic as well as the quadratic aberration vanish are discussed

Discussion on paper by R E Siday, entitled "The Optical Properties of Axially Symmetric Magnetic Prisms"

Discussion on paper by R E Siday, entitled "The Optical Properties of Axially Symmetric Magnetic Prisms"

The optical properties of axially symmetric magnetic prismspart 1: The study of rays in a plane of symmetry, and its application to the design of prism -spectroscopes

The optical properties of the magnetic field in the neighbourhood of two equal co-axial magnetic poles of opposite polarity used as a magnetic prism are discussed. In this first part attention is confined to rays in the plane of symmetry between the poles over which the radial component of the field vanishes everywhere. The focusing properties and aberrations are discussed generally, and detailed calculations are given: by simple analytical methods for the case of zero pole separation (homogeneous field); by numerical computation for the case of a pole separation equal to the radius of either pole. Inferences are drawn concerning the use of such fields in β-spectroscopy, and it is shown that under certain conditions image formation by the prisms is optically corrected over a very wide aperture, or under other conditions can be corrected in compound instruments conssiting of the prism and one or more magnetic lenses. Thus very high resolution is possible in such instruments. The overall optimum design for a β-spectroscope, however, cannot be made without a consideration of the focusing towards the plane of symmetry of rays confined to that plane. This focusing will be considered in Part 2.