Modification of the Charpak Chamber with Foil Supported Conductors

A conductive film supports the anode wires of a multi-wire proportional type counter and a bias voltage applied through this film controls the electric field concentration around the anode wires. Because the critical operating voltage is applied through the film one has increased freedom in the mechanical design of these chambers . Two coordinates of spacial information are available with this technique. The first coordinate is the anode wire signals. The second is obtained by a grid of ribbons on the back of the anode supporting film which picks up an induced signal from the primary discharge. Spacial resolution of 1.6 mm fwhm has been measured using the induced readout ribbon grid along with 3.3 mm fwhm on the anode grid. We expect this to improve.