Experiments are presented which demonstrate, for the first time, the extreme stopping power of fully ionized hydrogen plasma for low-energy (45 keV/u) heavy ions. The plasma was created by an electrical discharge in a 20 cm long quartz tube, producing electron densities up to 7 × ${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$ at plasma temperatures well above 1 eV. In the described experiment a stopping power of 1080 MeV/(mg/${\mathrm{cm}}^2$) was measured using krypton ions, which exceeds the corresponding value in cold neutral gas by a factor of 35. These measurements provide the first experimental confirmation of theoretical stopping power predictions close to the expected maximum in a fully ionized plasma.

• Received 6 April 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1550