A 10 kilo-tonne dual-phase liquid argon TPC is one of the detector options considered for the Deep Underground Neutrino Experiment (DUNE). The detector technology relies on amplification of the ionisation charge in ultra-pure argon vapour and offers several advantages compared to the traditional single-phase liquid argon TPCs. A 4.2 tonne dual-phase liquid argon TPC prototype, the largest of its kind, with an active volume of 3 × 1 × 1 m 3 has been constructed and operated at CERN. In this paper we describe in detail the experimental setup and detector components as well as report on the operation experience. We also present the first results on the achieved charge amplification, prompt scintillation and electroluminescence detection, and purity of the liquid argon from analyses of a collected sample of cosmic ray muons.

Abstract:The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a highpressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the L/E behaviour, and distinguishing effects arising from δ CP and matter.In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to > 5σ C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has ∼ 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract δ CP from the data, the first LBNO phase can convincingly give evidence for CPV on the 3σ C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.

The 3×1×1 m3 demonstrator is a dual phase liquid argon time projection chamber that has recorded cosmic rays events in 2017 at CERN. The light signal in these detectors is crucial to provide precise timing capabilities. The performance of the photon detection system, composed of five PMTs, are discussed. The collected scintillation and electroluminescence light created by passing particles has been studied in various detector conditions. In particular, the scintillation light production and propagation processes have been analyzed and compared to simulations, improving the understanding of some liquid argon properties.

A: We report the results of the analyses of the cosmic ray data collected with a 4 tonne (3×1×1 m 3 ) active mass (volume) Liquid Argon Time-Projection Chamber (TPC) operated in a dual-phase mode. We present a detailed study of the TPC's response, its main detector parameters and performance. The results are important for the understanding and further developments of the dual-phase technology, thanks to the verification of key aspects, such as the extraction of electrons from liquid to gas and their amplification through the entire one square metre readout plain, gain stability, purity and charge sharing between readout views.

To estimate the contribution of Chernobyl 137Cs contamination, in 1993 and especially 2016, its total inventory was determined by gamma-ray high-resolution spectroscopy in 62 and respectively 747 soil samples covering the entire Romanian territory. This permitted us to estimate the 1993 and 2016 total 137Cs inventory to 43 ± 2 TBq and respectively to 14.1± 0.7 Tbq, the last one reduced by a factor of 3 ± 0.3. This value, about twice higher than natural disintegration suggests a significant amount of 137Cs being washed out by precipitation and, in a lower measure, incorporated into plants. At the same time, by evaluating the maximum contribution of 137Cs to the population exposure, in 1993 and especially in 2016, the supplementary annual effective dose did not exceed, the maximum accepted value of 1 mSv.