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Research Highlight

The upgrade of the ALICE TPC with GEMs and continuous readout

The Relativistic Nuclear Physics group has played a leading role in the upgrade of the ALICE Experiment in preparation for the next data collection period at the CERN Large Hadron Collider.

After years of development and preparation, underground in situ commissioning of the full upgraded Time Projection Chamber (TPC) is now underway and proceeding smoothly using cosmic ray events, x-rays, and laser data.  The new Inner Tracking System (ITS) is presently being installed inside the TPC.   These upgrades are required to study the upcoming 50 kHz Pb-Pb collisions, eliminating inherent rate limitations of conventional trigger-based detector systems.  Ultimately, these upcoming measurements will improve our understanding of emergent properties of QCD in extreme conditions, studying by far the hottest, densest matter ever achieved under laboratory conditions.
Multiple state-of-the-art technologies were required for this major upgrade including high resolution large-area silicon tracking, Gas Electron Multiplier-based (GEM) time projection chambers with reduced deadtime, fast radiation-tolerant optical transceivers, and streaming readout with on-the-flying processing at the highest total bandwidth achieved in science (3 TB/s).  A new custom low-noise, radiation tolerant, continuously digitizing ASIC (SAMPA) was developed for the project which has subsequently been adopted by other experiments, including the sPHENIX Experiment at BNL.  The large scale of the TPC electronics upgrade required best practices of industrial production such as PCB production in China using an Apple top-100 supplier, and ORNL-developed automated test stations located at the assembly factory in Silicon Valley.
This work is described in the following 88-page article which has just been published:
C.L. Britton, L.G. Clonts, T.M. Cormier, M.N. Ericson, N.B. Ezell, J. Rasson,  K.F. Read, A. Rusu, J. Schambach, D. Simpson, R.J. Warmack, et al., JINST 16 P03022 (2021)