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

The large DD-fusion-yield enhancement reported earlier by our group [Phys. Rev. Lett. 63, 1292 (1989); J. Phys. Chem. 94, 7665 (1990)] in the bombardment of deuterated targets by large heavy-water clusters was shown by postacceleration magnetic and electrostatic filtering to be due to small-ion impurities produced in the acceleration column. With the 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 films on the polydeuteroethylene surfaces caused the observed fusion rates to decrease rapidly with time. This problem was solved by using D2O ice targets which are ''self-cleaning.'' No enhancement was observed for the fusion rates of the small D2O clusters after the oxygen knock-on corrections were made. However, the fusion yields for knock-on processes produced by (H2O)(n)H+ clusters (4 less-than-or-equal-to n less-than-or-equal-to 10) showed approximately a twofold enhancement over the yields for H3O+ ions at the same velocity. The stopping power of clusters was measured and shown not to be responsible for this enhancement.