Low-energy cosmic ray antideuterons ($<0.25$ GeV/$n$) are a compelling, mostly uncharted channel of many viable dark matter models and benefit from highly suppressed astrophysical background.
The General Antiparticle Spectrometer (GAPS) is a first-of-its-kind exotic-atom-based Antarctic balloon-borne experiment specialized for detection of low-energy antiprotons, antideuterons, and antihelium with a targeted launch in 2022. The results of novel technology development and a summary of current construction status are the focus of this contribution.
GAPS exploits a novel antiparticle identification technique based on exotic atom formation and decay, allowing more active target material for a larger overall acceptance since no magnet is required. The GAPS instrument consists of a large-area ($\sim 50$ m$^2$) scintillator time-of-flight, ten planes of custom silicon detectors with dedicated ASIC readout, and a novel oscillating heat pipe cooling approach.
This contribution will briefly introduce the exotic atom detection technique. Following this, the instrument design will be discussed and detailed description of experimental hardware and expected performance will be presented. I will conclude with recent construction and testing progress while also highlighting developments of a scaled, integrated prototype.