The General Antiparticle Spectrometer (GAPS) Antarctic long duration balloon mission is scheduled for launch during the austral summer of 2024-25. Its novel detection technique, based on exotic atom formation, excitation, and decay, is specifically designed for the detection of slow moving cosmic antiprotons and antideuterons. Such antinuclei are predicted by a wide variety of allowed dark matter models, as well as other astrophysical theories like primordial black holes.


There are two main components of the GAPS instrument: a large-area tracker and a surrounding time-of-flight system (TOF). The combination of these two systems allows GAPS to effectively differentiate between species of negatively-charged antinuclei and determine the energy deposition, velocity, and trajectory of particles interacting with the detector. This contribution will focus on the TOF, which determines the velocity of the incoming antiparticle and provides the trigger to the experiment. We will give an overview of the TOF detector, an explanation of relevant electronics, and a report on its construction and preliminary performance. The TOF is composed of 160 thin plastic scintillator paddles ranging in length from 1.5 to 1.8 meters. At each paddle end, signals from six silicon photomultipliers are combined to produce two copies of the resulting waveform: one to form the trigger and one for data readout. This design is optimized for low mass and fast data acquisition while still maintaining good light collection.