A state-of-the-art detector, called sPHENIX is being planned at RHIC for measuring jets, jet correlations and upsilons to study the microscopic nature of the QGP. Precision vertexing and tracking, as well as calorimetry, will be provided over full azimuth and pseudorapidities of |eta| < 1.1. The data will be continuously recorded making use of the 15 kHz RHIC collision rate in the region of interest.
A high resolution and low mass tracking system for reconstructing the three upsilon states is needed. The tracking system comprises silicon pixel and strip detectors and a compact TPC.
The TPC at the present planning stage will be using quadruple-GEM detectors as a readout, following the path of the ALICE-TPC upgrade, with a modified Neon-based gas mixture. The main tasks of this configuration are the achievement of sufficient momentum resolution and combating ion back-flow.
The motivation and the design of the technology choices will be presented along with the present status of the project. Furthermore, alternative readout structures, like hybrids of MicroMegas and GEMs will be discussed.