Imaging achievements with the Vernier readout

We describe the Vernier anode. a high resolution and charge division image readout for microchannel plate detectors. It comprises a planar structure of insulated electrodes deposited on an insulating substrate. The charge cloud from an event is divided amongst all nine electrodes and the charge ratio uniquely determines the two-dimensional position coordinate of the charge centroid. We discuss the design of the anode pattern and describe the advantages offered by this readout. The cyclic variation of the electrode structure allows the image resolution to exceed the charge measurement resolution and enables the entire active area of the readout to be utilized. In addition. fixed pattern noise is greatly reduced. We present results demonstrating the position resolution and image linearity. A position resolution of 10 mum FWHM is demonstrated and the overall imaging performance is shown to be limited by the microchannel plate pore spacing. We present measurements of the image distortions and describe techniques used to minimize them. (C) 2002 Elsevier Science B.V. All rights reserved.