  The first operation of a cryogenic Resistive Plate WELL (RPWELL) detector in
the saturated vapor of liquid argon is reported. The RPWELL detector was
composed of a Thick Gas Electron Multiplier (THGEM) electrode coupled to a
metallic anode via Fe$_2$O$_3$/YSZ ceramics (Fe$_2$O$_3$ in weight equal to
75$\%$), with tunable bulk resistivity in the range 10$^{9}$ - 10$^{12}$
$\Omega\cdot$cm. The detector was operated at liquid argon temperature in
saturated argon vapor (90~K, 1.2~bar) and characterized in terms of its
effective charge gain and stability against discharges. Maximum stable gain of
G$\approx$17 was obtained, without discharges. In addition, preliminary results
from novel 3D-printed thermoplastic plates doped with carbon nanotubes are
presented.
