Production of ultra-depleted protium

The base line of this project assumes utilization of the protium water available on the market with the lowest concentration of deuterium ($\leq$1 ppm). The expected distortion of the measured $\lambda_{\mu^-}$ due to muon transfer to deuterium nuclei at this concentration is small but not negligible. Therefore, some correction will be applied by the extrapolation method as explained in section 5.4.3.

To avoid this correction completely, it would be attractive to produce ultra-depleted protium with c$_d\leq$0.3 ppm. Negotiations with AECL, Chalk River Ontario, showed that in principle such protium could be produced but there are two problems: the considerable cost ($\sim$120 kSF) for the corresponding R&D and the lack of capability by the company to measure such small deuterium concentrations.

An alternative approach is presently under study at PNPI. In this case, the additional protium/deuterium separation would be reached by circulating the gas in a low temperature loop using Zeolites of the type NaA. This method would be relatively cheap and, what is also important, it could be implemented into the TPC gas circulating system to keep the deuterium concentration on a minimal level.

The deuterium concentration will be measured using a specialized mass spectrometer in St. Petersburg with a sensitivity limit of 0.1 ppm.