<title>Microchannel-plate-limited resolution with the Vernier anode</title>

Abstract

We have previously described the Vernier Anode, a conductive charge division readout device for use in microchannel plate detectors. The readout pattern comprises nine electrodes each of which varies cyclically, having a sinusoidal form. One of the major benefits offered by the Vernier design is that the spatial resolution can greatly exceed the charge measurement accuracy, unlike devices such as the wedge and strip anode, where the electrode variation is linear. Thus the Vernier anode can exploit the potential position resolution of even the smallest pore microchannel plates at readily achievable microchannel plate gains and electronic signal to noise ratios. We describe a detector utilizing the Vernier anode using the image charge technique. The microchannel plate event charge is collected on a resistive anode composed of Germanium deposited on an insulting substrate. This serves to localize the charge while it is being measured. The Vernier anode is capacitively coupled to the reverse side of the Germanium and the event charge induces signals on the Vernier anode, which are then used to calculate the event centroid position. We present spatial resolution and linearity results from a detector using the Vernier in image charge mode, and discuss the practical and performance advantages offered by this method of operation. The intrinsic spatial resolution of the Vernier anode is shown to be less than 10 microns FWHM and detector resolution is limited by the microchannel plate pore spacing.