Comments on the possible observation of d-d fusion in sonoluminescence

We have repeated the experiment of Taleyarkhan et al. in an attempt to detect the emission of neutrons from d-d fusion during bubble collapse in deuterated acetone. Using the same apparatus, a more sophisticated data acquisition system, and a larger scintillator detector, we find no evidence for 2.5-MeV neutron emission correlated with sonoluminescence from the collapsing bubbles. Any neutron emission that might occur is many orders of magnitude smaller than that necessary to explain the tritium production reported in Ref. 1 as being due to d-d fusion. We demonstrate that proper allowance for random coincidence rates in such experiments requires the simultaneous measurement of the complex time-varying singles rates. Introduction In a recent paper Taleyarkhan et al. reported the possible observation of d-d fusion events occurring in collapsing bubbles formed by cavitation in deuterated acetone. The bubbles were seeded by pulses of neutrons from a 14-MeV pulsed-neutron generator (PNG). This note summarizes the results of an attempt to reproduce some of these experimental results with the help of some of the original authors. We repeated their original experiment using all of the same equipment, with the exception of the neutron detector, for which we substituted a much larger one based on NE213 and thus capable of n-γ discrimination, and a significantly more sophisticated data acquisition system. The coincidences we observed were totally explained by random events, any excess neutrons in the singles data, if significant, did not correlate with sonoluminescence signals, and the reported level of tritium production should have been accompanied by a substantial neutron emission which we did not observe. Scope of the repeat experiment Our experiment focused on the detection of “penetrating radiation” from the sonoluminescent bubbles. No attempt was made to verify the reported tritium production. We note that these levels of tritium – if due to d-d fusion – would have been accompanied by easily detectable levels (10/s) of neutron emission. This is the same strength as the 14-MeV neutron generator used. The published experiment used fast sampling oscilloscopes to count coincidences between pulses from a phototube designed to detect light (SL) emission from sonoluminescent bubbles, and a plastic scintillator/phototube combination for detecting neutrons.