First operation and drift field performanceof a large area double phase LAr Electron Multiplier Time Projection Chamber with an immersed Greinacher high-voltage multiplier

Abstract

We have operated a liquid-argon large-electron-multiplier time-projection chamber (LAr LEM-TPC) with a large active area of 76 × 40 cm2 and a drift length of 60 cm. This setup representsthe largest chamber ever achieved with this novel detector concept.The chamber is equipped with an immersed built-in cryogenic Greinachermulti-stage high-voltage (HV) multiplier, which, when subjected to anexternal AC HV of ∼ 1 kVpp, statically charges up toa voltage a factor of ∼ 30 higher inside the LAr vessel, creatinga uniform drift field of ∼ 0.5 kV/cm over the full drift length.This large LAr LEM-TPC was brought into successful operation in thedouble-phase (liquid-vapor) operation mode and tested during a periodof ∼ 1 month, recording impressive three-dimensional images ofvery high-quality from cosmic particles traversing or interacting inthe sensitive volume. The double phase readout and HV systemsachieved stable operation in cryogenic conditions demonstrating theirgood characteristics, which particularly suit applications fornext-generation giant-scale LAr-TPCs.