FIRE - A fast image readout and electronics for microchannel plate detectors

The FIRE1 position readout has much commonality with existing conductive charge division readouts such as the wedge and strip, and Vernier anodes. It comprises a planar set of electrodes arranged in pitches, the event charge being collected by all elements. In one major respect however, it differs greatly from these devices, which are fundamentally analogue in their operation. Position encoding in FIRE is accomplished by using comparison of electrode signals alone and is effectively digital in nature. Thus it exhibits much higher noise immunity than comparable analogue devices enabling it to operate at high count rates, in excess of 10 MHz. We describe the FIRE pattern and the features of its design that minimize the problems associated with high-speed operation. The FIRE electronic design uses MMIC2 amplifiers with a pulse pair resolution of two nanoseconds. An unusual application of ECL logic(3) circuits provides an effective peak and field circuit used to overcome time delays across the readout pattern. Multiple comparators generate a digital event coordinate, which is converted to a position coordinate using a lookup table. We present results from a microchannel plate detector using a FIRE readout and electronics showing the count rate capability and spatial resolution achieved so far. We discuss the ultimate performance that may be achieved using this technique.