Cryogenic Rare Event Search with Superconducting Thermometers

CRESST stands for " Cryogenic Rare Event Search with Superconducting Thermometers " (paraphrased: cryogenic search for rare events using superconducting thermometers ) and is a European experiment for direct search for dark matter. It is located in the Laboratori Nazionali del Gran Sasso ( LNGS ) in Italy, the largest underground laboratory in the world. Participating institutions include the Max Planck Institute for Physics ( Munich), the Technical University of Munich, University of Tübingen, the University of Oxford ( UK) and the Istituto Nazionale di Fisica Nucleare ( INFN, Italy).

Detection principle

CRESST uses low-temperature calorimeter to detect the recoil energy of dark matter particles ( WIMPs ) in an absorber crystal at temperatures close to absolute zero (operating temperature ~ 15 mK). By the impact of a WIMP energy is deposited in the crystal, resulting in a minute change in temperature. A superconducting thermometer is thereby transferred from the superconducting to the normal conductive phase. The change in resistance associated is amplified and read out SQUID.

Since it is a weak interaction processes in rebounds this, are the expected rates extremely low ( about 5-10 events per kilogram in several years, depending on the model ). In order to measure this at all, all background events must be either suppressed by a shield, or be identified by data analysis. Furthermore, an attempt is made to to increase the detector mass up to a ton.

Project phases

CRESST I

The first stage of CRESST used four 262 g heavy sapphire crystals ( Al2O3) as absorber material. First measurements were carried out in 1999, the resulting limit on the WIMP cross section was published in 2003.

CRESST II

In the second phase, several fundamental changes were made:

  • The absorber 300 g of calcium tungstate crystals ( CaWO4 ) were used
  • Introduction of " dual detectors " for the simultaneous measurement of the recoil energy and scintillation. Allows the distinction of Photon-/Elektronereignissen and nuclear recoils
  • Mount a bracket for up to 33 dual detector modules including SQUID system

In September 2011, the CRESST collaboration published the analysis of the measurement period from 2009 to early 2011. Excluding the known noise to a signal unexplained income, which can be interpreted as an indication of a light dark matter particles revealed. This result is in contradiction with the results of the XENON and CDMS experiment. Since the COGENT and DAMA collaboration have published evidence of a light WIMP with slightly different masses and scattering cross sections, the result is currently discussed controversially.

EURECA

The long term goal of astroparticle physicists is to build a detector with a ton detector mass. For this purpose, it is planned that existing experiments CRESST, EDELWEISS and ROSEBUD under the name EURECA (European Underground Rare Event Calorimeter Array) merge and expand. Location will be the Laboratoire Souterrain de Modane (LSM ).

Similar projects

  • CDMS - Cryogenic Dark Matter Search
  • XENON Dark Matter Project
  • WARP
  • ROSEBUD
  • EDELWEISS
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