  Liquid argon (LAr) is a common choice as detection medium in particle physics
and rare-event searches. Challenges of LAr scintillation light detection
include its short emission wavelength, long scintillation time and short
attenuation length. The addition of small amounts of xenon to LAr is known to
improve the scintillation and optical properties. We present a characterization
campaign on xenon-doped liquid argon (XeDLAr) with target xenon concentrations
ranging from 0 to 300 ppm by mass encompassing the measurement of the
photoelectron yield $Y$ , effective triplet lifetime $\tau_3$ and effective
attenuation length $\lambda_\mathrm{att}$. The measurements were conducted in
the Subterranean Cryogenic ARgon Facility, SCARF, a 1 t (XeD)LAr test stand in
the shallow underground laboratory (UGL) of TU-Munich. These three
scintillation and optical parameters were observed simultaneously with a single
setup, the Legend Liquid Argon Monitoring Apparatus, LLAMA. The actual xenon
concentrations in the liquid and gaseous phases were determined with the
Impurity DEtector For Investigation of Xenon, IDEFIX, a mass spectrometer
setup, and successful doping was confirmed. At the highest dopant concentration
we find a doubling of $Y$ , a tenfold reduction of $\tau_3$ to $\sim$ 90 ns and
a tenfold increase of $\lambda_{att}$ to over 6 m.
