A Wire Spark Chamber Spectrometer with a Capacitor Memory and FET Readout

A 20-plane wire chamber spectrometer utilizing capacitors as memory elements and suitable for operation in a magnetic field is described. The (parallel) wire planes are separated by 1 cm. The active areas of the chambers range in size from 120 × 120 cm2 to 200 × 240 cm2. The wire separation is 1 mm. Each readout wire is connected to a separate capacitor resulting in a 30 K-bit memory for the total system. Using FET´s as gates, the capacitors are read out in 32 bit words. These words are formatted into data sets of 18 bits/spark and transferred to a PDP-9 computer. Digital processing of data is briefly described, including the computer interface and test procedures. Advantages of this system are discussed together with some performance characteristics.