  The GAPS experiment is foreseen to carry out a dark matter search using a
novel detection approach to detect low-energy cosmic-ray antideuterons. The
theoretically predicted antideuteron flux resulting from secondary interactions
of primary cosmic rays with the interstellar medium is very low. So far not a
single cosmic antideuteron has been detected by any experiment, but
well-motivated theories beyond the standard model of particle physics, e.g.,
supersymmetry or universal extra dimensions, contain viable dark matter
candidates, which could led to a significant enhancement of the antideuteron
flux due to self-annihilation of the dark matter particles.This flux
contribution is believed to be especially large at small energies, which leads
to a high discovery potential for GAPS. GAPS is designed to achieve its goals
via a series of ultra-long duration balloon flights at high altitude in
Antarctica, starting in 2014. The detector itself will consist of 13 planes of
Si(Li) solid state detectors and a time of flight system. The low-energy
antideuterons (< 0.3 GeV/n) will be slowed down in the Si(Li) material, replace
a shell electron, and form an excited exotic atom. The atom will be deexcited
by characteristic x-ray transitions and will end its life by forming an
annihilation pion star. This unique event structure will allow for nearly
background free detection. To prove the performance of the different detector
components at stratospheric altitudes, a prototype flight will be conducted in
2011 from Taiki, Japan.
