Application of the VMM3a/SRS: A t0-less TWIN GEM-based TPC

Integrating the ATLAS/BNL VMM3a ASIC (Application Specific Integrated Circuit) into the RD51/SRS (Scalable Readout System) provides a self-triggered continuous readout system for various gaseous detectors.Since the system allows flexible parameters, such as switching the polarity, adjusting electronics gain or different peaking times, the settings can be adjusted for a wide range of detectors.The system allows particles to be recorded with a MHz interaction rate in energy, space, and time.The system is used as a trigger-less readout for the TWIN GEM-TPC (Gas ElectronMultiplier-Time Projection Chamber) to prove the operationwithout external t$_{0}$ of such a TPC configuration. First results of position reconstruction withthe TWIN GEM-TPC are presented, with a spatial resolution around 220 µm in X, and330 µm in Y. Y is reconstructed from the time information, and X from the 1D stripreadout.Operating the setup as an ultra-low material budget tracking telescope, an angular distribution can be extracted in the horizontal and vertical planes.Giving distributions with σ$_{h}$ = 0.15° in the horizontal plane and in the vertical plane σ$_{v}$ between 0.3° and 0.9°, depending on the reconstruction method.