Spherical time projection chambers (TPC), also known as spherical proportional counters, are employed in the search for rare phenomena, such as light Dark Matter candidates. The spherical TPC exhibits a number of essential features, making it a promising candidate for the search of neutrinoless double beta decay ($betabeta0 u$). A tonne-scale spherical TPC experiment could cover a region of parameter space relevant for the inverted mass hierarchy with a few years of data taking. In this direction, the major R&D goal of the R2D2 effort is the demonstration of the required energy resolution. First results from an argon-filled prototype detector are reported, demonstrating an energy resolution of 1.1% FWHM for 5.3~MeV $alpha$ tracks in the 0.2 to 1.1~bar pressure range. This is a major milestone in terms of energy resolution, paving the way for further studies with xenon gas, and the possible use of this technology for $betabeta0 u$ searches.
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