Participation of the Max Planck Institutes

Scientists of the MPI for Nuclear Physics (MPIK) initiated the GERDA experiment in 2004, in order to check the results of the Heidelberg-Moscow experiment by using an innovative shielding approach in which the germanium diodes are operated in an ultrapure cryogenic liquid. Major contributions of the MPIK include the design and supply of the cryostat filled with liquid argon, the refurbishment of the enriched diodes from previous experiments, the supply of low-radioactivity natural germanium detectors, the low-mass detector suspension, and the data acquisition system including software.

Last not least, the MPIK researchers performed a large part of the screening and validation of the highly pure construction materials. In addition, MPIK provided a detector test facility and is developing a liquid-argon veto for the second measurement phase. Crucial for this is the long-term expertise of the physicists and technicians at the MPIK in so-called low-level techniques, i.e., the ability to detect lowest levels of radioactivity. The highly sensitive instruments are operated in an underground laboratory where they are protected from cosmic radiation.

The GERDA team from the Max Planck Institute for Physics in Munich contributed to the GERDA experiment in many important areas, including designing, constructing, deploying and operating a part of the infrastructure. This infrastructure consists of a clean room on top of the cryostat and a vacuum and gas tight lock system with a sophisticated internal pulley system for movement of the detectors. The unique setup minimizes contaminations from naturally occurring radioactive elements which could otherwise mimic the extremely rare decays.

The researchers of the Max Planck Institute for Physics also procured and undertook the refinement of 37.5 kg of germanium enriched in the isotope 76Ge, yielding extremely pure material with a high yield. A fraction of this material was used to produce detectors deployed in the first phase of the experiment, and the rest will be used in the second, even more sensitive phase of the GERDA experiment. Extreme care was taken throughout the processing steps to ensure minimal production of radioactive isotopes in the Germanium due to cosmic rays.

The Munich team members were also key contributors in the analysis of the data that are being presented today, as well as in the operation of the experiment.

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