Operation of Multidrift Tubes with Dimethyl Ether

Abstract

The most difficult region to instrument in a detector for collider experiments is the one close to the vacuum tubes, where the density of tracks and the background rate are very high. This is, moreover, the most inaccessible region of the set-up; a major breakdown there has the worst consequences for the whole operation. One way of improving the reliability of a system based on gaseous wire detectors is to increase its modularity and redundancy; such an approach was originally taken by a group at SLAC with the development of cheap, mass-produced individual drift tubes or’ straws’ that can be assembled to constitute a complete detector.¹ Extending this concept further, we have built several multidrift modules that have many independent drift cells packed within a thin carbon-fibre supporting tube, of hexagonal shape, which also contains the gas. Each sensitive cell consists of an anode wire centred in a hexagonal drift structure with cathode wires at the corners. Our first prototypes (called Model 1) had 128 anodes per module, with an anode-to-cathode distance (cell radius) of 1.15 mm; the method of construction and the main experimental results obtained with such a design have already been described.^2,3 Because of the problems encountered in the manufacturing of such a high-density detector, we have redesigned the detector as Model 2, slightly increasing the cell radius to 1.45 mm (1.27 mm between wire planes); this has simplified wiring and soldering, and greatly increased the reliability of the detector, at the expense of a decrease in the information density (70 cells per tube) and a slightly longer resolution time. All results described in this note refer to Model 2.