Spherical gaseous time projection chamber detectors, known also as spherical proportional counters, are widely used today for the search of rare phenomena such as weakly interacting massive particles. In principle such a detector exhibits a number of essential features for the search of neutrinoless double beta decay (ββ0ν). A ton scale experiment using a spherical gaseous time projection chamber could cover a region of parameter space relevant for the inverted mass hierarchy in just a few years of data taking. In this context, the first point to be addressed, and the major goal of the R2D2 R&D effort, is the energy resolution. The first results of the prototype, filled with argon at pressures varying from 0.2 to 1.1 bar, yielded an energy resolution as good as 1.1% FWHM for 5.3 MeV α tracks having ranges from 3 to 15 cm. This is a milestone that paves the way for further studies with xenon gas, and the possible use of this technology for ββ0ν searches.

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The measurement of neutrino magnetic moment larger than 10-19 μB would be a clear signature of physics beyond the standard model other than the existence of massive Dirac neutrinos. The use of a spherical proportional counter detector filled with gas at 40 bar located near a nuclear reactor would be a simple way to perform such a measurement exploiting the developments made on such a technology for the search of dark matter and neutrinoless double beta decay. Different targets can be used just by replacing the gas: xenon, CF4 and argon were compared and the sensitivity in one year of data taking could reach the level of 4.3 × 10-12 μB , 6.5 × 10-12 μB , and 8.5 × 10-12 μB , respectively.