a design study for a cobra upgrade to - Institut für Kern- und ...

Chapter 3
The COBRA experiment
COBRA, being an acronym for CdZnTe-0ν-Double-Beta-Decay-
Research-Apparatus, is a double beta decay experiment, using CdZnTe
semiconductor crystals. It was founded in 2001 by K. Zuber and is
currently in the R&D phase, hosted with a prototype apparatus at the
Laboratori Nazionali del Gran Sasso (LNGS). The COBRA experiment
investigates the neutrinoless double beta decay of nine different double
beta decay isotopes. Double beta decays, being extremely rare processes,
lead to very small event rates in the order of events per day for
2νββ decays and even expected events per year in case of 0νββ decays
in one kg source material. These are covered by background rates in
the order of events per second. Accordingly, the background reduction
is essential for all double beta experiments.
This chapter will explain the concept of the COBRA experiment and the
structure of the current prototype set-up, before motivating the design
of a COBRA upgrade with enhanced efficiency for gamma ray detection.
3.1 CdZnTe
COBRA is currently the only double beta decay experiment using
CdZnTe semiconductor crystals. These crystals are simultaneously
source and detector, leading to excellent detection efficiency for double
beta decays.
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