Experimental Verifications Of The Nuclear Effect Of Acoustic Cavitation

Acoustic cavitation has a very important position in ultrasonics and has beenapplied in many fields for more than a century, R.P.Taleyarkhan research group in theUnited States of America Oak Ridge Nation Laboratory had been done the researchesof acoustic fusion with different nucleating particles from2002to2007and resultsshowed that there was nuclear effect in acoustic cavitation. Their conclusion hasinspired scientists to study nuclear effect of acoustic cavitation (NEAC).This article makes more studies of NEAC in detail with different methods andfrom different angles to achieve reliable experimental data. The main contents were asfollows:(1) Arrangement of NEAC experiment was improved, and the neutron spectrumand the γ spectrometer measurement systems were assembled and adjusted and thehigh electronic stability and measurement accuracy were achieved. The measurementrelative standard deviation（RSD）of spectrometers were <5.0%, which wouldsatisfied the experiments of NEAC.(2)Many experimental methods were designed to study NEAC. The neutrons fromneutron generator and from fission of252Cf, and α particles from241Am were used asthe nucleated particles respectively in acoustic cavitations of NEAC. The fusion inreaction liquids during the acoustic cavitation were verified repeatedly.(3)Fast neutron activation method had been used to verify the NEAC.14MeVneutrons originated in acoustic cavitation fusion were determined using copperthreshold detectors. According to the nuclear reactions of14MeV neutrons with63Cu,(n,2n), the characteristicγ-radiations of62Cu were measured. When neutronirradiation time was50min,511keV characteristic γ-radiation counts of activatedcopper pieces with or without ultrasound after30min of decay time were determinedrespectively by NaI detector. The nuclear effect of acoustic cavitation was verifiedaccording toγpeak net counts increments, C, and the statistically significant increases.(4)The temperature in the acoustic cavitation nuclear reaction system was inquired.(D,D) fusion temperatures of acoustic fusion neutrons emissivity in NEACexperiments were estimated using the reaction rate equation based thermodynamicequilibrium, the temperatures of D-D fusion in the acoustic cavitation were about6~8KeV (about107K); Monte Carlo simulation of neutron transport process inmedium showed that the single elastic collision energy loss between neutron andcomponential atom of heavy water is about0.28MeV and this energy can not onlyform bubble nucleus, but also heat the nuclear reaction particles, which introducethermonuclear reaction; The spatial distributions of neutrons in NEAC systems weremeasured, the angular distribution of neutrons without ultrasound was obviouslyforward and that of neutrons with ultrasound was forward a little, that is, the angularcorrelation of neutrons with ultrasound was lower than that of neutrons withoutultrasound. Therefore, reaction in cavitation bubbles may be characterized by thermofusion.