Diamond shaped cathode pads for the longitudinal coordinate from a drift chamber

Results are presented for a system of diamond shaped cathode pads which give the coordinate of an avalanche along the length of the wire of a large area drift chamber to an accuracy of 1 mm. To first order the method is insensitive to small lateral displacements of the signal wire and to the pulse height. Two sets of such pads, above and below the wire, and offset relative to one another longitudinally by a quarter of the repeat distance, provide a check sum which (1) validates the data, (2) helps to calibrate the non-linearities and (3) determines the resolution.