The research activities of the XENON group are centered around the detection technology with liquid xenon.
The XENON Collaboration is an international collaboration that brings together a dozen of laboratories in the U.S., China and Europe, among which Subatech, and which conducts basic research focused on the searching for dark matter in the universe by developing a detection system with liquid xenon.
The goal of the XENON Collaboration is the discovery of a direct evidence of the presence of particles called WIMPs (Weakly Interacting Massive Particles), an acronym to describe a family of massive particles weakly interacting with matter, by observing their interaction within a target consisting of ultra pure liquid xenon and placed underground at the Gran Sasso National Laboratory (LNGS), Italy. WIMPs are to date the most likely candidates to describe dark matter, especially the neutralino. The detection technique used is that of a time projection chamber (TPC) biphasic, consisting of a xenon target in liquid phase (LXe) and an amplification phase consisting of xenon gas (GXe). This system has the ability to simultaneously detect signals from scintillation and ionization via two planes of photomultipliers located at upper and lower ends of the chamber.
The current phase of the research program is called XENON100 and uses a total of 161 kg of xenon. It is so far the experience with the best sensitivity for the detection of dark matter, as demonstrated by the results published by the XENON collaboration in 2012, which reported an unprecedented sensitivity on the interaction cross section of WIMPs in the whole domain of masses. Subatech, who joined the collaboration in 2009, is now involved in the analysis and in data processing.
The next phase of the research program, XENON1T, will use the same detection technique, with a total mass of about 3.3 tons of xenon. For this next step, Subatech is involved in most aspects of construction of the detector, and is responsible for the construction of the xenon recovery system, ReStoX (Xenon Recovering System). The XENON1T detector is expected to reach a sensitivity 100 times greater than that of its predecessor.
Given the possibility of adapting the technology of the time projection chamber used by XENON Collaboration to a very large scale, the European scientific community is already working for the study of a detector of the order of several tons. Thus, the DARWIN project is a network of different European laboratories whose goal is to develop the next generation of detectors for the discovery or for a more accurate measurement of the properties of WIMPs in the case of a precedent discovery by the XENON1T experiment.
The detection technique using a time projection chamber xenon is a promising technology not only for particle physics, but also for other applications that have a more direct impact on our society. It is within this context that the Subatech is developing a liquid xenon Compton telescope for medical imaging, XEMIS (Xenon Medical Imaging System). In a first phase, XEMIS1, we were able to demonstrate the quality of our detection principle. We are currently working to improve this system as part of a new phase of the project, called XEMIS2, and whose goal is to develop a demonstrator that would conduct studies on small animals.
Finally, the possibility of adapting to different scales the xenon detector technology opens the way for the development of photosensitive sensors capable of detecting photons over large areas. Subatech is a pioneering laboratory for the development of cryogenic gaseous photomultipliers, called GPM (Gaseous Photomultiplier), which play a fundamental role in future detectors.
The fundamental research
The dark matter