Speaker
Description
The sPHENIX detector at RHIC is a heavy ion experiment that aims to further investigate the microscopic nature of the QGP through precision measurements of jets, the upsilon, and open heavy flavor probes over a broad pT range. The Time Projection Chamber (TPC) is the main tracking detector in the experiment with a rapidity range of |η|<1.1 and full azimuthal coverage. Amplification in the TPC is performed using an array of quadruple-stacked gas electron multiplier (GEM) modules to amplify signals from the chamber for precise tracking measurements. The GEM foils and transfer gaps are energized through resistor chains that distribute high voltage across the entire stack. Sparking events within the GEMs will sometimes lead to changes in the effective resistance that reduce the gain of affected modules and limit TPC performance. Initial attempts to restore proper voltages to these modules proved challenging due to the placement of the HV cards in the magnet bore of the detector. To simplify this process, the HV chain of each module was modified by rerouting the resistors on the GEM HV cards to breakout boxes located in separate racks away from the detector that use replaceable resistor cards. Here we present the design, testing, and implementation of the TPC breakout boxes as well as future upgrades to further improve the system in the next run of sPHENIX.
