Improvements to the image bandpass filter for electron and positron spectromicroscopy

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Abstract
The design and construction of a low-pass electron energy mirror with controllable image rotation and pass energy to operate in a magnetic field is described. Image rotation is radially uniform and rotations of up to approximately 40 degrees are demonstrated. A low-pass filter is described incorporating a virtual reflecting surface and a novel electron trap also operating in a magnetic field. This reduces the proportion of elastically and inelastically scattered high-energy electrons escaping the filter. Both the above elements are demonstrated working in an image bandpass filter operating in a photoelectron spectromicroscope. Low-energy (0-35 eV) electron absorption and reflection from a number of electrode surfaces is investigated and recommendations made on possible structures. A scheme is proposed whereby azimuthally averaged axial emission angles can be obtained from electrons emitted in a photoelectron spectromicroscope using an image bandpass filter. The devices considered are equally suited to the manipulation of low-energy positrons and will allow simultaneous positron-energy analysis and imaging.