Fusion in Cavitation
Nuclear Fusion under the Action of Cavitation
Tech Area / Field
- FUS-PLA/Plasma Physics/Fusion
3 Approved without Funding
Institute of Physical-Technical Problems, Russia, Moscow reg., Dubna
- Joint Institute of Nuclear Research, Russia, Moscow reg., Dubna
- Istituto Nazionale di Fisica Nucleare, Italy, Monserrato\nCNRS / Centre de Recherche de la Matière Condensée et des Nanostructures, France, Marseille\nUniversity of Washington / Center for Industrial and Medical Ultrasound, USA, WA, Seattle\nUniversité du Québec en Outaouais, Canada, QC, Gatineau
Project summaryIn the project it is planned to carry out the experiments on producing the superhot plasma and obtaining nuclear D+D fusion during acoustic cavitation, and to specify the main factors determining the yield of thermonuclear reaction during cavitation.
During last several years, theoretical and experimental indications at a possibility of the realization of thermonuclear synthesis during acoustic cavitations were obtained. Theoretically this possibility was proved in the paper [Moss et al, Sonoluminescence and the prospects for table-top micro-thermonuclear fusion. Phys. Lett. A211, p. 69 (1996)]; the most in details the question was considered in a series of works of R. Nigmatulin and co-workers. In these works it was shown, that in a limited area near the center of a cavitation bubble the plasma cluster is generated with temperature up to T~108 K and density ρ ~10-100 gram/cm3. If deuterium presents in the structure of working liquid, the neutron emission from D+D reaction occurs with the rate up to 104 s-1. In the first experimental work [Taleyarkhan, R. P. et al. Evidence for nuclear emissions during acoustic cavitation. Science 295, 1868-1873 (2002)] the neutron yield in coincidence with the light pulses during the ultrasonic cavitations in cooled acetone was reported about. Cavitation was supported due to the action of pulses of fast neutrons coincident in time with the maximum of decompression of the liquid in a standing acoustic wave at a frequency ~25 kHz. According to the interpretation of results, the neutrons were produced in d+D→3He+n (En=2.45 MeV) reaction. The relative neutron excess over a background was no more than 4 %, however statistical confidence was rather high: the excess above the background was ~5 SD. In the subsequent experiments [Taleyarkhan, R. P. et al. Additional evidence of nuclear emissions during cavitation. Phys. Rev. E 69, 036109 (2004)] mainly the same methodic was used, and the excess over the background amounted ~26 SD. In experiment with another technique the primary cavitation centers was generated by the neutrons from a radioisotope source of permanent action. The results also proved the conclusion about the observation of thermonuclear reactions in the D+D→ 3He+n system.
Nevertheless, critical relation to so important conclusions proceeded. This was connected mainly with the use of primary fast neutrons in the experiments, and the detection of “thermonuclear” neutrons on the background of the scattered primary neutrons.
Right after that, the additional confirmation of the conclusion about the thermonuclear reactions during the cavitation was obtained. It was succeeded to detect the yield of neutrons with the energy about 2.5 MeV without the application of primary neutrons [Taleyarkhan, R. P. et al. Nuclear Emissions during self-nucleated acoustic cavitation. Phys. Rev. Lett., 96034301 (2006)]. Small amount of radioactive substance emitting α-particles during the deceleration of which the primary cavitation centers was generated. This results enhanced appreciably the convincingness of the conclusions about the cavitation thermonuclear synthesis.
Thus, the significant experimental material proving the possibility of the realization of the thermonuclear reactions during the cavitation is accumulated at present. At the same time the independent confirmation of so important results concerned of the new ways of the realization of the nuclear synthesis during the inertial confinement of the hot plasma in the cavitating liquid is urgent as before. In particular, numerous unsuccessful attempts of other experimental groups to repeat these experiments tell about that. Besides, the very topical task is represented by the further development of this new direction of the study of the processes of the cavitation formation of the superhot plasma, and of the finding of new conditions for the production of the thermonuclear reactions, the search for the ways of increasing the yield of the reactions due to the variation of the experimental conditions: the types of the working liquids, parameters of the medium, external conditions.. The analysis of the theoretical and experimental data shows that the important factors determining dynamics of the process are the properties of the liquid (vapor pressure and the condensation ability, the sound speed), acoustic field parameters (the frequency, sound level), and some others; in particular, the possibility of obtaining the higher values of acoustic cavitation threshold by more accurate purification of the medium or at the expense of increasing hydrostatic pressure. It is planned in the project to carry out the experimental study on the systematic investigation of the problem of the controlled thermonuclear fusion under the action of cavitation directed at obtaining the following results:
- independent confirmation of the possibility of the realization of the controlled thermonuclear synthesis during the confinement of the hot plasma in cavitating liquid media;
- data on the neutron emission yield (thermonuclear reaction D+D) in various liquids;
- data on the parameters of the media and the conditions of the experiment determining the neutron emission yield during the cavitation, such as the level and the frequency of the field, cavitation threshold, media temperature, hydrostatic pressure, the ways of the formation of the primary cavitation centers (neutrons, charged particles).
- methods of the realization of a self-sustaining thermonuclear reaction due to cavitation (prerequisites for the development of a thermonuclear reactor on the basis of the acoustical-cavitation method of the synthesis).
One of the important peculiarities of the planned investigations consists in carrying out the experiments at sufficiently higher values of acoustic pressure. In connection with this, a special attention will be paid on the problem of increasing values of acoustical thresholds in liquid, since exactly the premature spontaneous cavitation limits the value of acoustical pressure that can be achieved in the resonator. For it's turn, the cavitation thresholds are decreased due to the presence of foreign admixtures in the liquid. The use of the radioactive source of α-particles is connected with the introduction of the considerable amount of uranium chemical compound into the liquid: several grams of the compound are required for the achievement of the necessary intensity of α-radiation. Only this one decreases automatically the cavitation threshold. For the elimination of this factor it is proposed to use short life-time α- radioactive isotopes as the alternative to uranium. The most effective should be the isotope 212Pb (life-time T1/2 = 10.6 h). The necessary amount of the radioactive substance occurs negligibly small in this case: in the limit 1012 times less in comparison with the case, when the uranium is used.
Another idea, which will be explored in the project, consists of the realization of the self-sustaining cavitation fusion reaction under the action of cavitation. Up to now, no methods of the creation of conditions for self-sustaining thermonuclear reaction under the action of cavitation were proposed. A complexity of the realization of self-sustaining reaction is caused by a fact that the moment of the emission of neutrons from the fusion reaction D+D→3He+n and the moment of the cavitation starting are separated by a considerable time interval, thus, using the neutrons from the reaction for restarting the process of the synthesis represents a problem. Two variants of solving this problem is proposed. One of them consists of using a so-called few-bubble sonoluminescence mode, when the conditions for arising two or more centers of capturing the pulsing bubbles are formed. Moreover, bubble pulsations at the different centers occur with a phase shift corresponding to the time interval between the moment of starting cavitation process and the moment of the neutron emission from the D+D reaction. The second variant can be realized in an array of the resonators excited with the appropriate phase shifts. These experiments are interesting from the various points of view. First, the self-sustaining cavitation fusion reaction, if successfully realized, will give a new evidence of the very idea of this effect: in this case the reaction will take place without any external radioactive action (save the primary starting pulse of neutrons). Furthermore, the self-sustaining mode is interesting from the point of view of the increasing the nuclear reaction yield. When every cavitation event is generated by the external neutron pulse, the frequency of their repetition is ~100 s-1. The self-sustaining reaction will take place with the frequency of the driving acoustical field, i.e., with the frequency f=30-60 kHz. Thus, the intensity will prove to be 300-600 times higher and will amount the value 107 s-1 and more (the intensity is ~ 104–105 when primary neutrons are used, and 103–104 in the experiments with the use of α-particles).
At the present time the group of the authors of the project possesses an experimental facility for obtaining superhigh temperatures during the cavitation [Miller M.B., Sermyagin A.V., Sobolev Yu.G., Kostenko B.F. “Experimental facility for checking the possibility to obtain super-high temperature due to acoustic cavitation”. Communication of the Joint Institute for Nuclear Research. P13-2004-214. Dubna, 2004]. The facility is supplied with the necessary equipment for the detection of neutrons from D+D reaction with the use of scintillation counter with a system of identification of neutrons by the pulse shape. The start of the cavitation is carried out by the neutron beam from the neutron generator synchronized with the phase of the ultrasonic vibrations. For the realization of the experiments under the planned program the development of the advanced installation is planned. The various methods of neutron detection, including nuclear track detectors, will be applied. The group has the experience of dealing with the track detectors, including the detectors of light ions CR-39. There are already necessary amount of this type of the detectors at the disposal of the group, as well as the equipment for their processing and the identification of the tracks.
The present project meets the ISTC purposes, promoting the integration of Russian scientists into the international scientific community, redirection of the efforts of Russian defensive experts at the science-intensive activity not connected with the weapons development, and also gives the contribution to the resolving one of the most important problems of the modern physics and ecologically clean power engineering. The labor expense of the defensive experts will take the most part of the general labor expense of the project.
It is planned the participation of the foreign collaborators in the discussion of intermediate and final results, in joint seminars, workshops and conferences. Closer forms of co-operation are possible also, for example in-site acquaintance with the developed experimental instrumentations and carrying out the joint experiments with the purpose of increasing reliability of the conclusions.