  Radial time projection chambers (TPC), already employed in the search for
rare phenomena such as light Dark Matter candidate, could provide a new
detection approach for the search of neutrinoless double beta decay
($\beta\beta0\nu$). The assessment of the performances of such a detector for
$\beta\beta0\nu$ search is indeed the goal of the Rare Decays with Radial
Detector (R2D2) R\&D. Promising results operating a spherical TPC with argon up
to 1~bar have been published in 2021. Supplementary measurements were recently
taken extending the gas pressure range up to 3~bar. In addition, a comparison
between two detector geometries, namely spherical (SPC for spherical
proportional counter) and cylindrical (CPC for cylindrical proportional
counter), was performed. Using a relatively simple gas purification system the
CPC detector was also operated with xenon at 1~bar: an energy resolution of
1.4\% full-width at half-maximum was achieved for drift distances up to 17~cm.
Much lower resolution was observed with the SPC. These results are presented in
this article.
