A Tetramethylsilane TPC with Cherenkov light readout and 3D reconstruction

Abstract

We describe the construction and calibration of a multi-channel liquid time projection chamber filled with Tetramethylsilane. Its charge readout system consists of 8 wires each in the X and Y directions. The chamber is also equipped with a light readout system consisting of a 5′′ photomultiplier tube coupled to the liquid volume through a viewport. The energy scale of the detector is calibrated using positron–electron pairs produced by 4.4 MeV gamma rays emitted from an AmBe source, using an external trigger on the positron annihilation gammas. The external trigger is then reconfigured to tag cosmic ray muons passing through the active Tetramethylsilane volume, which are used to measure the stopping power in Tetramethylsilane and the electron lifetime in the detector. We find a most-probable energy loss from minimum ionizing particles of Δp∕ds = (0.60 ± 0.01) MeV/cm. We also measure an electron lifetime of 43−21+680μs by measuring the most-probable energy loss as a function of drift time. For both measurements, the errors are statistical only. For both fast electron and muon signals, the photomultiplier tube detects prompt Cherenkov light, demonstrating the possibility of self-triggering of the detector. The room-temperature organic target medium, together with the self-triggering capabilities and long electron lifetimes reported in this work, make this an attractive technology to explore for rare event detectors or other applications in the area of radiation measurements.