Pontecorvo's 1945 paper credits the idea using carbon tetrachloride (CCl4) to the French physicist Jules Guéron. Experiments were conducted at Chalk River using the NRX as a neutrino source, but were unsuccessful, and were abandoned in 1949, after Pontecorvo had left. The experiment was unsuccessful because, unknown at the time, nuclear reactors produced antineutrinos instead of neutrinos. In what is now known as the Cowan–Reines neutrino experiment, Frederick Reines and Clyde Cowan detected antineutrinos in 1955, for which they won the Nobel Prize in Physics in 1995.