MAX - Multi-ton Argon and Xenon TPCs

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This proposal will fund the search led by Princeton University for evidence to the existence of dark matter that is made of Weakly Interacting Massive Particles (WIMPs). WIMPs may be detectable by their collisions with nuclei on Earth, but the low expected rate of such collisions and low energy of the recoil nuclei requires massive detectors with extremely low background rates, located in a deep underground laboratory. The development of a Deep Underground Science and Engineering Laboratory (DUSEL) will enable the deployment within the U.S. of WIMP detectors several orders of magnitude more sensitive than those operating today. This proposal plans to use Liquid argon and xenon as the active media in Time Projection Chamber (TPC)where the scintillation and ionization can be independently detected and spatially resolved through large volumes of liquid. The discrimination of nuclear recoils from background is possible using the relative size and time dependence of these signals. By exploiting these methods and the self-shielding capability of the dense liquids, the leading xenon and argon TPC experiments have already achieved competitive sensitivity to WIMPs. This proposal plans to develop two important new technologies that will greatly enhance the power of the present collaboration to design the best xenon and argon detector system for the discovery and identification of WIMPs: (1) the development within the Xenon collaboration of a new low radioactivity, high-quantum-efficiency hybrid photomultiplier tube, the Quartz Photon Intensifying Detector or Qupid, designed at UCLA in partnership with Hamamatsu and (2) the discovery of underground sources of argon gas low in the isotope 39Ar by the Princeton and Notre Dame groups, supported by the NSF. This proposal will also prepare the way for a following generation of still-larger detectors (10 ton xenon TPC, 50 ton depleted argon TPC). These will be required to detect WIMP dark matter if the cross section is below the 10 to the minus 47 cm**2, or to perform high statistics, detailed studies of WIMP properties if WIMP dark matter is discovered using DUSEL-ISE experiments.BROADER IMPACT: The proposed activity will advance the development of DUSEL and its scientific and educational mission in a variety of ways: (1) it will help the visibility of DUSEL as an international facility, through cooperation and partnership of US universities and national laboratories with European and Japanese groups; (2) it will offer an excellent opportunity for the training of students, who will have a chance to contribute to the success of a cutting edge project in fundamental science and advanced engineering; (3) it will benefit society through commercial applications of noble liquid detectors and associated technologies in areas ranging from national security to medical imaging; (4) it will support continued development of successful EPO programs such as the Princeton-Abruzzo-South Dakota summer school for high school students.