  The General AntiParticle Spectrometer (GAPS) is a balloon-borne cosmic-ray
antimatter experiment that uses the exotic atom technique, eliminating the
requirement for strong B-fields used by conventional magnetic spectrometers. It
will be sensitive to antideuterons with kinetic energies of 0.05-0.25 GeV /
nucleon, which are highly motivated candidates for indirect dark matter
detection. Moreover, GAPS will provide new information on the antiproton
spectrum from $0.07<T<0.25$ GeV. The GAPS design is based on a lithium drifted
silicon tracker and plastic scintillator time of flight (TOF) system. The
latter is the focus of this contribution.
  Currently, the TOF system includes an outer "umbrella" consisting of 132
counters covering an area of 38 m$^2$ and a nearly hermetic inner "cube" with
64 counters and area of 15 m$^2$. The counters will be mechanically secured to
the gondola using an innovative carbon fiber structure. Each end of the 196
counters will be read out using a silicon photomultiplier (SiPM) based analog
front end with a high gain timing channel and low gain trigger channel. The
high gain channel is sampled and digitized with a custom readout board that
uses the DRS-4 ASIC. A local trigger monitors multiple programmable threshold
levels for all 392 counter ends. A master trigger analyzes the local trigger
hit patterns and initiates a TOF read out for an interesting event. A central
computer then analyzes and estimates key observables. This contribution
summarizes the design, performance, and prototype development of the TOF system
and the path going forward in 2019 and 2020 towards construction and
integration of the system.
