This award will provide funds for research and development to advance the search for the direct detection of dark matter Weakly Interactive Massive Particles (WIMPs) with liquid xenon (LXe) as target and detector medium in next generation, large volume, two-phase time-projection chambers (TPC). These types of detectors have been most successfully exploited by the XENON collaboration, with the XENON10 prototype and the XENON100 detector. The latter is currently the most sensitive dark matter experiment in operation underground with a target at the 100 kg mass scale.
The group will develop and test a two-phase Xe TPC prototype to validate the design of the next generation XENON1T experiment. A key requirement for the realization of multi-ton LXe detectors is the demonstration of electron drift over a meter length, under a field of at least 1 kV/cm. At the same time, one has to demonstrate the liquid xenon purity required to allow ionization electrons to drift across such large detectors. The Collaboration has designed a detector system which will be able to address these and other questions relevant to XENON1T. The goal is to get results within one year, and most of the equipment items could also be used in the actual XENON1T development.
The broader impact of this award comes about since the XENON science addresses questions about fundamental properties of the Universe, with all the ingredients to captivate the interest and imagination of students and the general public alike. The research and development work will advance the application of LXe detectors and related technologies in fields beyond particle astrophysics, including national security and medical imaging research.
Most of the matter in the Universe is not in the form of known atoms, but consists of some new, unknown kind of matter. The nature of this so-called Dark Matter is one of the greatest outstanding questions of contemporary physics. As we fly with the Solar System through the Milky Way, we constantly plow through a halo of this Dark Matter. Thus there is a constant head-wind of Dark Matter particles that penetrate everything and everybody on Earth, much as it is the case for better known particles such as, for example, neutrinos and cosmic rays. One way to try to unravel what Dark Matter is made of is then to try to detect some of these particles as they pass through a detector. Led by the Columbia University PI, and with continuing support from the National Science Foundation, the XENON collaboration has installed and operated in the Laboratori Nazionali del Gran Sasso, in central Italy, the XENON100 detector, which is at present the most sensitive apparatus looking for dark matter. After a two years search, the detector has found no evidence of the presence of dark matter, but has set the most stringent constraints on its properties. To continue the search for this elusive dark mat- ter, the collaboration has proposed a new generation detector, XENON1T (Xenon one ton), with a mass ten times larger than XENON100 and a sen- sitivity one hundred times better. To be able to realize such an experiment, several technical challenges must be overcome. This R&D proposal provided the funds to build the XENON1T Demonstrator, a facility capable to test some of the key technologies necessary for the construction of XENON1T. The Demonstrator consists of a cryogenics system and a liquid xenon detector with a total height of 1 meter similar to what is planned for XENON1T. It uses novel technologies which enable the application of very high voltages (up to 100 kilovolts), the fast purifcation of the xenon gas and its efficient cooling to turn it into liquid. With this Demonstrator Facility we have achieved the drifting of electrons over one meter, with an electric field of 1 kV/cm and a liquid xenon recirculation rate close to 100 liters per minute. The successful operation of the detector within this R&D project has allowed us to identify effective solutions to some of the most critical challenges identified during the design of XENON1T. With the experience gained during this R&D phase we will begin the construction of the new detector in the next months. The XENON1T experiment will start operation in 2015, at the Laboratori Nazionali del Gran Sasso, continuing to lead the quest for understanding the nature of dark matter.
