  In the Fall of 2017, two photon detector designs for the Deep Underground
Neutrino Experiment (DUNE) Far Detector were installed and tested in the TallBo
liquid argon (LAr) cryostat at the Proton Assembly (PAB) facility, Fermilab.
The designs include two light bars developed at Indiana University and a photon
detector based on the ARAPUCA light trap engineered by Colorado State
University and Fermilab. The performance of these devices is determined by
analyzing 8 weeks of cosmic ray data. The current paper focuses solely on the
ARAPUCA device as the performance of the light bars will be reported
separately. The paper briefly describes the ARAPUCA concept, the TallBo setup,
and focuses on data analysis and results.

Instrumentation and Detectors