The sPHENIX TPC Line Laser Calibration System

Résumé fourni par la source

The sPHENIX experiment has just completed its first year of data collection from high energy particle collisions at Brookhaven National Laboratory's Relativistic Heavy Ion Collider. A vital component of the sPHENIX tracking system is a Time Projection Chamber (TPC), capable of measuring particle tracks with very high precision over a relatively long lever arm in a 1.4 T magnetic field. However, to achieve this precision, the device must rely on several independent calibration schemes to correct for significant deviations to measured particle trajectories caused by non-uniformities in both the electric and magnetic fields in the drift region, including$\mathrm{E} \square \mathrm{B}$effects. We have developed a so called “Line Laser” system to address the corresponding impact from small mechanical imperfections in the TPC vessel. This system delivers multiple steerable laser beams into the TPC at opportune times to scan virtually the entire active volume to a precision of a fraction of a degree. As each beam sweeps across the volume, distortion information from each region is carried to the readout plane. We report on the novel design of this system and evaluate its performance with regard to providing an effective means for calibrating static distortions in a TPC.

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