[en] Large-scale technological success of high-temperature superconductors will ultimately be decided by their capacity to sustain large critical current densities J_c in high magnetic fields. There are two principal factors controlling current conduction. One is regions of weaker superconductivity (weak links) at the grain boundaries in polycrystalline materials. Another is easy motion of magnetic vortices in the bulk -- the result being energy dissipation and losses. Each of these factors is a challenge to overcome, for their origin is intrinsic: i.e. short superconducting coherence length ξ, large anisotropy, large thermal fluctuations (related to high transition temperature T_c), and perhaps even a d-wave character of the superconducting ground state. For these reasons, in spite of the highest T_c's (> 130 K), mercury cuprates HgBa₂Ca_n-1Cu_nO_2n+2+δ with n = 1, 2 or 3 adjacent CuO layers (Hg-1201, 01212, or -1223) still have relatively low-lying irreversibility lines (suppressed by a strong 2-D nature of the vortex structure), above which J_c vanishes. Here, the authors demonstrate a method by which they expand the useful range to T > 100 K (higher than in Y-, Bi-, or Tl-based materials) and boost J_c by orders of magnitude in fields of several Tesla -- namely fission of Hg nuclei within Hg-cuprates with energetic (0.8 GeV) protons. This technologically viable process allows doping these cuprates with strongly pinning columnar defects