  The Balloon Experiment for Galactic INfrared Science (BEGINS) is a concept
for a sub-orbital observatory that will operate from $\lambda$ = 25-250 $\mu$m
to characterize dust in the vicinity of high-mass stars. The mission's
sensitivity requirements will be met by utilizing arrays of 1,840 lens-coupled,
lumped-element kinetic inductance detectors (KIDs) operating at 300 mK. Each
KID will consist of a titanium nitride (TiN) parallel strip absorbing inductive
section and parallel plate capacitor (PPC) deposited on a silicon (Si)
substrate. The PPC geometry allows for reduction of the pixel spacing. At the
BEGINS focal plane the detectors require optical NEPs from $2\times10^{-16}$
W/$\sqrt{\textrm{Hz}}$ to $6\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$ from 25-250
$\mu$m for optical loads ranging from 4 pW to 10 pW. We present the design,
optical performance and quasiparticle lifetime measurements of a prototype
BEGINS KID array at 25 $\mu$m when coupled to Fresnel zone plate lenses. For
our optical set up and the absorption efficiency of the KIDs, the electrical
NEP requirement at 25 $\mu$m is $7.6\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$ for
an absorbed optical power of 0.36 pW. We find that over an average of five
resonators the the detectors are photon noise limited down to about 200 fW,
with a limiting NEP of about $7.4\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$.
