A new design of wire locators for drift tubes

Every position-sensitive wire detector needs to solve the problem of wire positioning with a defined accuracy all over its sensitive volume. In particular, thin-walled drift tubes ("straws"), which are currently being attached to large detector units of several tens of square meters of surface, need to be equipped with wire locators along their signal wires. A wire locator has been developed together with an insertion device, especially for medium-sized drift tube systems, which significantly reduces the production time and avoids the danger of applying epoxy glue to the signal wire. The wire locator is being inserted in one single time-saving production step together with the signal wire itself. The proposed design is being compared to the rigid wire locators in use in the COMPASS straw tracking system at CERN. The investigation comprises both wire-centering capability and influence on the efficiency of adjacent detector regions, demonstrating the competitive performance of the proposed new system. Its sufficient mechanical reliability could be shown by means of an X-ray tomography; the attractively small influence on the drift field was determined in a test measurement using a silicon tracking system in a hadron beam.