DD-NUCLEAR-FUSION REACTIONS WITH SMALL D2O AND H2O CLUSTERS IMPACTINGHEAVY ICE

The large DD-fusion-yield enhancement reported earlier by our group [P hys. Rev. Lett. 63, 1292 (1989); J. Phys. Chem. 94, 7665 (1990)] in th e bombardment of deuterated targets by large heavy-water clusters was shown by postacceleration magnetic and electrostatic filtering to be d ue to small-ion impurities produced in the acceleration column. With t he filtering arrangement in place we have carefully studied DD-fusion rates with small (D2O)(n)D+ and (H2O)(n)H+ ions (n less-than-or-equal- to 10) which produced detectable fusion rates. Formation of carbon fil ms on the polydeuteroethylene surfaces caused the observed fusion rate s to decrease rapidly with time. This problem was solved by using D2O ice targets which are ''self-cleaning.'' No enhancement was observed f or the fusion rates of the small D2O clusters after the oxygen knock-o n corrections were made. However, the fusion yields for knock-on proce sses produced by (H2O)(n)H+ clusters (4 less-than-or-equal-to n less-t han-or-equal-to 10) showed approximately a twofold enhancement over th e yields for H3O+ ions at the same velocity. The stopping power of clu sters was measured and shown not to be responsible for this enhancemen t.