sPHENIX TPC Alignment and Distortion Calibration: An Overview

The sPHENIX experiment at Brookhaven National Laboratory's Relativistic Heavy Ion Collider has been collecting collision proton-proton and gold-gold collision data since 2023 to study the emergent properties of QCD in the Quark Gluon Plasma, the structure of jets, and nucleon spin dynamics. Accurate tracking, essential for these studies, is enabled by four tracking detectors: an innermost MAPS-based vertex detector, a silicon strip detector with precise timing resolution, a compact Time Projection Chamber (TPC) for precise momentum measurement and an outer micromegas-based detector to aid in space charge distortion calibration of the TPC. Achieving the experiment's physics objectives demands precise alignment of the tracking subsystems and accurate calibrations to correct trajectory distortions of drifting electrons within the TPC caused by the 1.4 T magnetic field and ion-induced space charge effects. The distortions and alignment errors are corrected using three complimentary subsystems: a digital current readout framework used to monitor the ions flowing back into the TPC volume, dedicated laser calibration systems to monitor the static and short-timescale components of the distortions, and a track fitting-based method utilizing data from the partial coverage micromegas detector. In this talk, I will present details on the scale and structure of alignment errors and distortion corrections, describe the monitoring subsystems, and outline the procedures used to derive and implement the calibrations.