Electron Multiplier Time Projection Chamber Research Articles

Long-term operation of a double phase LAr LEM Time Projection Chamber with a simplified anode and extraction-grid design

We report on the successful operation of a double phase Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) equipped with two dimensional projective anodes with dimensions 10 × 10 cm2, and with a maximum drift length of 21 cm. The anodes were manufactured for the first time from a single multilayer printed circuit board (PCB). Various layouts of the readout views have been tested and optimised. In addition, the ionisation charge was efficiently extracted from the liquid to the gas phase with a single grid instead of two previously. We studied the response and the gain of the detector to cosmic muon tracks. To study long-term stability over several weeks, we continuously operated the chamber at fixed electric field settings. We reproducibly observe that after an initial decrease with a characteristic time of τ ≈ 1.6 days, the observed gain is stable. In 46 days of operation, a total of 14.6 million triggers have been collected at a stable effective gain of G∞ ∼ 15 corresponding to a signal-to-noise ratio (S/N)≳60 for minimum ionising tracks. During the full period, eight discharges across the LEM were observed. A maximum effective gain of 90 was also observed, corresponding to a signal-to-noise ratio (S/N)≳400 for minimum ionising tracks, or S/N ≈ 10 for an energy deposition of 15 keV on a single readout channel.

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

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.

Stable operation with gain of a double phase Liquid Argon LEM-TPC with a 1 mm thick segmented LEM

In this paper we present results from a test of a small Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC). This detector concept provides a 3D-tracking and calorimetric device capable of charge amplification, suited for next-generation neutrino detectors and possibly direct Dark Matter searches. During a test of a 3 lt chamber equipped with a 10×10 cm2 readout, cosmic muon data was recorded during three weeks of data taking. A maximum gain of 6.5 was achieved and the liquid argon was kept pure enough to ensure 20 cm drift (O(ppb) O2 equivalent).

First operation of a double phase LAr Large Electron Multiplier Time Projection Chamber with a 2D projective readout anode

We have previously reported on the construction and successful operation of the novel double phase Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC). This detector concept provides a 3D-tracking and calorimetric device capable of adjustable charge amplification, a promising readout technology for next generation neutrino detectors and direct Dark Matter searches. In this paper, we report on the first operation of a LAr LEM-TPC prototype equipped with a single 1 mm thick LEM amplifying stage and a 2D projective readout anode. The active area of the detector is 10×10 cm 2 and the drift length is 21 cm. Cosmic muon events were collected, fully reconstructed and used to characterize the performance of the chamber. The obtained signals provide images of very high quality and the energy loss distributions of minimum ionizing tracks give a direct estimate of the amplification. We find that a stable gain of ∼ 30 can be achieved with this detector configuration corresponding to a signal-over-noise ratio larger than 200 for minimum ionizing tracks. The decoupling of the amplification stage and the use of the 2D readout anode offer several advantages which are described in the text.

Operation of a double-phase pure argon Large Electron Multiplier Time Projection Chamber: Comparison of single and double phase operation

We constructed and operated a double phase (liquid–vapour) pure argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) with a sensitive area of 10 × 10 cm 2 and up to 30 cm of drift length. The LEM is a macroscopic hole electron multiplier built with standard PCB techniques: drifting electrons are extracted from the liquid to the vapour phase and driven into the holes of the LEM where the multiplication occurs. Moving charges induce a signal on the anode and on the LEM electrodes. The orthogonally segmented upper face of the upper LEM and anode permit the reconstruction of X– Y spatial coordinates of ionizing events. The detector is equipped with a Photo Multiplier Tube immersed in liquid for triggering the ionizing events and an argon purification circuit to ensure long drift paths. Cosmic muon tracks have been recorded and further characterization of the detector is ongoing. We believe that this proof of principle represents an important milestone in the realization of very large, long drift (cost-effective) LAr detectors for next generation neutrino physics and proton decay experiments, as well as for direct search of Dark Matter with imaging devices.