The CIEMAT DM group has a long time experience in liquid argon (LAr) technology, profiting from the expertise, equipment and know-how acquired since the start of our participation in projects like ICARUS and ArDM. We are carrying out a first-class R&D program on the Ar technology, investigating frontier aspects of the noble elements technology so far not fully understood, exploring new paths towards potential novel techniques. The R&D is structured in three main research lines focused on both the charge transport in argon and the detection of the vacuum-ultra-violet (VUV) noble liquids scintillation light. Different prototypes are currently in operation and several new results recently published and are listed in the RESEARCH OUTPUT menu bar.
AVOLAR: high voltage system for massive LAr detectors.
The relatively high fields (~keV/cm) and the long drift distances (some meters), typical in massive LAr detectors, require very high voltages on the cathode. In order to fulfil the new technical requirements, reaching the MV range, our group designed a high voltage generator based on a Van Der Graaff scheme, in which the charge transporting insulating belt has been replaced by a hydrodynamic flow of liquid Argon.
ARION: Study of ion transport in LAr detectors.
Very little is known about the dynamics of the positive ions in LAr time projection chambers. Given their small mobility coefficient in liquid argon, the ions spend a considerably longer time in the active volume with respect to the electrons, producing space charge effects which modify the electric field in the TPC and disturb the charge signal energy and track reconstruction. Those effects have been not fully understood and very little can be found in the literature. Our group predicted, for the first time and before the recent experimental observation, meaningful recombination effects of the electron signal with the volume charge. This effect has a tremendous impact on the event reconstruction of the new massive LAr experiment now under construction.
ARDIS: Argon scintillation and particle discrimination studies.
We built a high-pressure gas chamber designed for the investigation of the Ar photon emission mechanism and the electron vs nuclear recoil discrimination. Preliminary studies have been carried out using radioactive sources (241Am and 90Sr/90) installed inside the chamber, with argon at different pressures (up to 15 bar), demonstrating that the usual second excimer mechanism, typically assumed to explain the light emission, is not satisfactory. This R&D activity has been awarded an EXPLORA grant in 2019 (FPA2017-92505-EXP). The studies on new particle identification techniques will continue during the next years.