XENON1T: a giant dark matter hunter

Dark matter, five to six times more abundant than ordinary matter, remains one of our universe’s greatest enigmas. Invisible and unobservable, it continues to challenge physicists around the world. With the aim of detecting and studying it, Dominique Thers and his team from Subatech joined the XENON project in 2009. On November 11, 2015, in the heart of the Gran Sasso mountain in Italy, the researchers on this program launched XENON1T – the most sensitive dark matter detector ever developed.

 

 

XENON1T

XENON1T is the largest dark matter detector built to date

 

What is dark matter? How can we observe it? Are we even certain it exists? Many questions have fueled this scientific controversy for decades. According to Dominique Thers, the answer to the third question is absolutely clear: “The observation of certain phenomena in our universe leaves no doubt that dark matter does exist”. This comes as no surprise: since 2009, this researcher from the Subatech laboratory — under the supervision of Mines Nantes, the University of Nantes and the CNRS — has been hunting for dark matter. The first clues appeared in the 1930s, when a Swiss astronomer named Fritz Zwicky measured the velocity of seven galaxies in the Coma Berenices constellation. The data collected presented a problem; if the observed velocities were correct, then the galaxies’ masses would have to be greater than that of the visible matter that composed them. He therefore hypothesized that the galaxies must consist of an invisible mass as well: dark matter. Almost one century later, astronomers have accumulated more evidence, in particular via the Planck satellite, enabling them to reinforce this idea which has since become a certainty. Yet these observations are all indirect, since they involve determining the presence of this enigmatic matter through phenomena that do not truly reveal it. So, in order to reveal dark matter once and for all, the XENON research program decided to develop an experimental device on an unprecedented scale called XENON1T, which is the result of a several years of collaboration between 21 international teams, bringing together over 120 researchers, including Dominique Thers and his colleagues from Subatech. It was inaugurated on November 11, in the heart of Italy.

 

équipe Xenon subatech, Mines Nantes

The Xenon team at the Subatech laboratory, one of the 21 teams working to detect dark matter on the XENON program.

 

WIMP, the ideal candidate

The XENON program works on the premise that out of all the current hypotheses on the nature of dark matter, the most probable concerns WIMPs — an acronym for weakly interacting massive particles. WIMPs are thought to be particles of matter, but different from baryons, which include protons and neutrons, which are the building blocks for atomic nuclei. Unlike baryons, WIMPs are thought to react very weakly to normal matter due to their extremely small interaction surface area, but are believed to have a very large mass, which explains why they cannot be observed, while solving the mystery of the invisible mass in the universe. However, little interaction does not mean no interaction. This nuance is the starting point for researchers. Because although it is very unlikely, the probability of a WIMP coming into contact with the nucleus of an atom, or an electron orbiting around the atom, does indeed exist. The challenge is therefore to make sure this collision takes place while the scientists are watching. Or rather, when their instruments are watching, since the detection of this phenomenon requires very specialized tools.

 

The expected collision

XENON1T is in fact an enormous chamber filled with one metric tonne of the chemical element xenon, maintained in a liquid state at a temperature around -100 °C. Above this liquid there is a thin layer of xenon in a gaseous state. The key is for a WIMP to interact with the xenon inside the chamber. “When a dark matter particle collides with the xenon, it dimerizes due to the energy created by the collision,” explains Dominique Thers. In other words: two isolated xenon atoms come together to form a dixenon molecule. Yet this state is temporary, because it is unstable. The molecule quickly separates again, forming two isolated and inert xenon atoms. But since energy was consumed to link the two atoms, the energy is emitted when they separate — “nothing is lost,” to quote Antoine Lavoisier. And this energy is emitted in the form of a photon. Or, in other words, light. “This light signal, called ‘scintillation’, is detected by the instruments located above and below the liquid xenon chamber, and is the first signal we record,” explains. But this is not all: the impact of the WIMP and atom colliding causes the xenon nucleus and electrons to move backwards, and as they slow down, they ionize the xenon in their orbit. Although an electron that has been removed usually returns to its original nucleus, the researchers prevent it from doing so by applying an electrical field to the device. The electrons are therefore forced to follow this path and rise to the top of the chamber, where they enter the gaseous phase, at the same time releasing a second signal, called an “ionization” signal. According to Dominique Thers, “the two signals allow us to very precisely determine the nature of the particle that caused the collision.”

 

XENON1T

Diagram explaining the XENON1T experiment

 

Buried deep beneath the mountain

The problem is that WIMPs face serious competition. Many different particles produced by cosmic rays bombard the earth each day and interact with ordinary matter, and much more frequently than WIMPs. To protect themselves from these disruptive particles, the XENON collaboration decided to bury their project 1,400 meters below the Gran Sasso mountain in the Apennines, in the largest underground laboratory in the world: the Gran Sasso National Laboratory (LNGS). The only particles that can pass through the rock to the laboratory are particles that hardly interact at all with ordinary matter, such as dark matter particles.

Despite these precautions, unwanted residual signals remain, referred to as “noise”. It was for this reason that researchers decided to establish a procedure using a tonne of liquid xenon, in order to limit this “noise”. “The first prototype, XENON10, contained only 10 kg of xenon, then in 2009 we increased to 100 kg with XENON100,” Dominique Thers recalls. “As the volume increases, we are more likely to detect a collision,” he adds. The detector’s upgrade to a volume equivalent to a mass of one tonne will make the results much more precise, making it the most advanced detector in the world. XENON1T, the successor to XENON100 and XENON10, will therefore “improve the accuracy of the observations a hundredfold compared to the current limitations,” explains the Subatech team coordinator. The researchers are therefore optimistic about finally detecting the long-awaited dark matter particle: “We hope to have results in the first months of the detector’s exposure,” says Dominique Thers. Before now, physicists had always advanced by eliminating hypotheses and hoping they would reach only one possibility. The observation of an interaction with xenon would represent considerable progress, since it would enable the identification of the particles that constitute this matter that remains so mysterious, despite it being five times more abundant in our universe than ordinary matter. And if XENON1T is unable to achieve its goal, the researchers in the underground laboratory already have plans to upgrade to a larger size. In 2018, XENON1T will become XENONnT, multiplying its weight in liquid xenon by five.

Access tunnel for the national Gran Sasso laboratory

Towards a smart electricity network

For several years, Smart Grids have been the hot topic in the energy field. As current networks become less and less adapted to new energy issues, we need to thoroughly rethink energy management and introduce smarter electricity networks. These networks of the future should be able to adapt production to consumption as precisely as possible, taking into account new parameters and constraints such as renewable energy or electric vehicles. The Institut Mines-Télécom, with expertise in the field of energy with the Mines schools and knowledge in the field of digital technology thanks to the Télécom schools, is involved in various projects for the Smart Grids engineering.

 

If the amount of research on Smart Grids is significantly increasing, it’s because there is a sense of urgency. “The driving force behind it all is energy transition. France must quarter its CO2 emissions by 2050”, explains Marc Girod-Genet, researcher at Télécom SudParis. The difficulty is that the solutions proposed for this transition are not always compatible with the state of current electricity grids. Most renewable energy sources are, for example, highly fluctuating and dependent on weather conditions. Moreover, some end users are becoming prosumers (i.e. both producers and consumers) by installing a miniature wind turbine or solar panels with associated small energy storage infrastructures, a dual role that has not been sufficiently accounted for by the network.

Another problem is the future popularization of electric vehicles, with heavy consumption at any hour of the day. “A few years ago it was a lot simpler to manage electricity grids,” Marc Girod-Genet points out. “If we needed more energy, with standard power plants, it was generally enough to increase the output. Today, production and consumption phases fluctuate much more.” The expected energy transition is therefore impossible without Smart Grids that are allowing the matching of these new demands.

 

Changes at all levels

Smart Grids can be seen as classical electricity grids to which three new aspects are added: a telecommunications network to relay information on the, a large scale and distributed information management system, and an energy services platform.

As primary links in the chain, consumers’ houses will very soon be fitted with smart meters. “The objective within Europe is to equip 80 % of households with this type of meter by horizon 2020” says Marc Girod-Genet. These new tools will allow local management decisions to be made according to in particular consumer habits, equipment available and levels of consumption. “Télécom Bretagne research teams are currently working on all these mechanisms for measurement communication and preprocessing information locally (Advance Metering Infrastructure – AMI), in partnership with Itron and Texas Instruments in a joint research center for developing such smart meters”, explains Marc Girod-Genet. The resulting combination of these meters with a telecommunications network will allow information to be received on a larger scale in the various control centers that will collect this sea of data. These control centers will link the information up with other types of data, for example wind speed measurements for forecasting wind turbine production. “This data is particularly large in quantity (Big Data) and diverse in nature and scales. One of the challenge is therefore to find ways of managing this heterogeneity in order to facilitate decision-making on actions aiming to improve energy efficiency. Big Data analysis is one of our specialties at Télécom SudParis.” Finally, this new network architecture, provided with an extended energy-related knowledge base, will also allow the provision of new services such as dynamic pricing, dynamic energy provider selection, and smart monitoring of electricity consumption, for each consumer. The Institut Mines-Télécom is involved in such societal changes in energy consumption.

 

Micro-grids in electric vehicles

Researchers at the Institut Mines-Télécom have been working for several years on different aspects of these Smart Grids, and more generally on what is known as Smart Energy.  For Marc Girod-Genet, this involvement is logical: “The Mines schools have always been strong in the field of pure energy, such as in particular production management, energy transport and storage, renewable energy management, fuel cells and energy transformation. Télécom research teams are contributing expert knowledge on communications networks and their management; information management systems and data modeling/processing issues (Big Data included); smart metering, Advance Metering Architecture (AMI); and service architectures. We are therefore perfectly qualified to work on Smart Grids.” Such expertise has led to the involvement of the Institut Mines-Télécom laboratories in various large-scale projects. One of them, Nice Grid (with the participation of Mines ParisTech), was launched in 2011 and allowed a Smart Grid, or “micro-grid” to be tested out at local level within a district of Nice (fifth French city). With smart meters, energy monitoring and consumer involvement, every aspect of smart grids was included in this project.

The Institut Mines-Télécom is also looking into issues less directly linked to smart grids, like electric vehicles. Completed in 2013, the VELCRI project[1] (with the participation of Télécom SudParis) consisted of three main research priorities: optimizing the distribution of charge amongst vehicles, allowing secure communication between the charging station, cars and the electricity network and finally using car batteries as a means of energy micro-storage. “Thanks to internal partnerships between Mines and Télécom researchers, we have lots of different studies on future energy networks” concludes the researcher. The Internet of Things and machine-to-machine communication (M2M), cloud architecture, environmental impact, societal issues, infrastructural and data security etc.: these are all lines of research within the Institut Mines-Télécom for optimal answer to energy transition objective requirements.

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SEAS, for a European smart grid

Studies on Smart Grids are not limited to the local or national scale. With globalization, Europe is becoming increasingly focused on energy management. At the end of 2013, a major European project named SEAS (Smart Energy Aware Systems) was launched, involving collaborators from Spain, Finland, Portugal, Turkey and France. The aim is as simple as it is ambitious: achieve interoperability of different energy systems, leading to umbrella energy management. Since management systems vary greatly from one country to another, the challenge will be to standardize generic mechanisms, data format, protocols and materials for energy information representation, processing and exchange between energy systems, automation systems, ICT based digital services and all related stakeholders. In this respect, Armines, Télécom Bretagne, Télécom ParisTech and Télécom SudParis researchers are contributing significantly to this 3-year project, focusing particularly on the open semantic energy data models used, the energy information exchange platform and the management of electric vehicles. According to the partners involved, the concrete applications of this research should be seen at the end of the project scheduled for 2017.[/box]

[author title=”” image=”https://imtech-test.imt.fr/wp-content/uploads/2014/06/Photo_Marc_Girod_Genet_recadré.jpg”]In 1994, Marc Girod-Genet left EPITA. His engineering diploma in hand, he headed to the USA where he obtained a Master of Science at the Stevens Institute of Technology. “Born in Zaire, I’ve always been attracted to going abroad”, says the researcher. Yet it was in France that he accepted his first job, at CNET (now Orange Labs), whilst also writing a thesis at the same time. In 2000 Marc Girod-Genet earned his PhD in Information Sciences at the University of Versailles Saint-Quentin-en-Yvelines before joining Télécom SudParis in the same year as EU research project manager. He concentrated in particular on mobile networks, already endeavoring to introduce more intelligence.

He later became an associate research and professor in 2005, which allowed him to teach alongside his research. “I like this perspective of knowledge transfer,” he admits “the field of new information and communication technology is evolving very quickly, and our teaching must therefore be constantly adapted.” With two decades already under his belt studying all types of networks as well as multiple awards, Marc Girod-Genet has a considerable amount of knowledge to transfer…[/author]

[1] VELCRI: Electric Vehicle with Integrated Quick Charging

From epertise in telecommunications networks to the performance of electricity grids

From networks to everyday objects, the internet has radically changed our environment. From the main arteries to the smallest vessels, it is embedded in such a large number of the most banal objects that it puts a strain on the energy bill. Yet now communicating objects can exchange information to optimize their electricity consumption. After several years of research on the IPv6 protocol, Laurent Toutain and Alexander Pelov, researchers at Télécom Bretagne, are adapting this protocol to suit objects with a small energy supply and to the smart grids that are being built. Their work is part of a series of Institut Mines-Télécom projects on energy transition, focusing on the evolution, performance and compatibility of the energy networks of the future.

 

From the web to the Internet of things: 20 years of protocol development

Over the past few years the advent of smart transport and the Internet of Things has exposed the limits of the classical model of the internet. Mobility, creation of spontaneous networks, energy constraints and security must be taken into account. The number of devices eligible for an Internet address has exceeded capacities of IP, the network’s fundamental protocol. With IPv6, a version offering 667 million billions of possible IP addresses per mm2 on Earth, each component or receptor of an object can now have its own address and be consulted. But IP was not designed for receptors located in the middle of nowhere with finite resources such as the processor, battery and memory and with low-speed connection. For such “LowPAN”, Low Power Wireless Personal Area Networks, a new version of IPv6 has been created, 6LowPAN, with an associated consultation protocol, CoAP (constraint application protocol), which assists continual communication between the traditional internet and that of Things.

“CoAP is a new way of structuring networks,” explains Laurent Toutain, “the interaction between existing networks and communicating objects can be established in two ways: either by improved integration of IP protocols making the network more uniform, or by marginalization of IP within the network and a diversification of the protocols for access to things”. Confidentiality and security aspects will be fundamental to the success of either one of these architectures. The researcher and his team also use mathematical models and game theory, applying them to the fields of smart transport and energy management.

Transmitting data in local energy loops

Over the past few years several regions in France producing considerably less electricity than they consume have endeavored to mobilize the region towards adopting concerted energy efficient behavior. Alexander Pelov observes that “this is the case of the poorly supplied Provence-Alpes-Côte d’Azur region, which is becoming the leader in smart grids”, meaning a vision of an electricity network with optimized links to improve its overall level of energy efficiency. Brittany and its partners have also been working for several years on controlling the demand for electricity, developing the production of energy from renewable sources and the security of electricity supply. In 2012 it sent out an initial call for projects on the “local energy loop”.

One of the objectives of electricity suppliers today is to be able to exchange data through the electricity network, “a network that was never designed to transport them”, emphasizes Laurent Toutain. It will use a low-speed 250 kb/s configuration similar to LowPAN, with the same constraints as the Internet of Things. Laurent Toutain’s team has built a simulator to precisely model the behavior of such networks. This simulator allows the re-definition of routing algorithms and the study of new applicative behavior. “We try to adapt to the existing infrastructure: we must use it so we can adapt to all forms of traffic”, and also improve the network’s performance to increase its uses. This is a major challenge because the electricity network must, for example, communicate with vehicles and negotiate if there is a priority ambulance, as well as supplying energy and transferring it from one place to another. “Without prior knowledge of telecoms networks, none of that is possible”, explains the researcher.

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A smart grid skills center on the Rennes campus of Télécom Bretagne

The fruit of a partnership with the Itron group, specialists in the development of metering solutions, and of Texas Instruments, experts in the field of semi-conductors, this research centre for power line communication technology inaugurated in November 2013 creates innovative solutions for electricity suppliers (technical upgrading of networks, smart metering etc.) and serves the French smart grids industry with the expertise of its researchers and engineers. Find out more +[/box]

Giving consumers a more active role in consumption

While better energy management can be achieved by the supplier, consumers must also play their part. Rennes is a pioneering city in thinking on the Digital City, a smart, sustainable and creative city built on the openness of public data, and has in this context sent out a call for projects concerned with energy and transport policies. Currently developing the ÉcoCité ViaSilva district, Rennes is encouraging inhabitants to restrict their energy usage and has committed to an Open Energy Data program.

Based on the observation that “we cannot double the existing infrastructure in order to transmit data”, the team of researchers based in Rennes are working on systems that give people a more active role in their consumption. It has been observed that the simple fact of showing users their consumption levels encouraged them to adopt better habits and led to savings of between 5 and 10%. “The idea is to make it fun, to imagine the “foursquare” of energy” explain Laurent Toutain and Alexander Pelov, referring to the localization mobile application whose most active users win badges. Another aspect is the visual representation of user behavior, which the team is working on with the École Européenne Supérieure d’Art de Bretagne, in digital laboratories (FabLabs) in Brittany. “Ultimately”, the researchers continue with a smile, “it’s like doing quantified-self at home”. This famous concept of “self-quantification” refers to the notion of being a “consum’actor” studied by sociologists and which is proving to be significant at this time of energy transition.

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Research fostering spin-offs

“It’s extremely rewarding to work on a societal issue like energy”, enthuses Alexander Pelov. Numerous collaborations with start-ups like Cityzen Data, companies like Deltadore, Kerlink, Médria and the FabLabs bear witness to this passion. The start-up Homadeus that is currently in the Télécom Bretagne incubator offers both “open energy data” materials and the interfaces (web and mobile) to drive them.[/box]

 

Toutain_recadréLaurent Toutain and Alexander Pelov are both researchers in the Networks, Security and Multimedia Services department of Télécom Bretagne. A reputed expert in IP networks, and in particular in service quality, metrology, routing protocols and IPv6, Laurent is currently looking at newPelov architectures and services for domestic networks with a  focus on industry and technology rather than research. After studies in Bulgaria and a thesis at the University of Strasbourg in 2009, Alexander joined Télécom Bretagne in 2010 to work on energy efficiency in wireless networks and the use of smart grids in the context of smart metering and electric vehicles.

Rédaction : Nereÿs