Precise measurement of internal sense-wire locations in high energy physics detectors

Abstract The central tracking region of the Solenoidal Detector Collaboration detector being designed to operate at the Superconducting Super Collider will utilize gas-filled straw tubes for particle tracking; the straws, each containing a thin central wire for charge collection, will be collected into modules of a few hundred straws each. It is crucial for proper interpretation of the data that the positions of the sense wires be known to very high precision. A pattern-deviation scanning system is being investigated for determining if the sense wires in constructed modules are within 35 μm of their intended locations. The system involves moving a module in steps through a broad x-ray beam and comparing a response matrix of transmission measurements to a template which is characteristic of a “perfectly” aligned module. The pattern-deviation scanner approach is described and simulation results are presented.