Bulk thermolian

Science and thermonuclear bubbles

Bubble thermal unit: blowing sensation or discovery?

Messages about sensational scientific achievements can excite the imagination of the general public for a long time, however, they are accepted by the scientific community only if they are justified in accordance with the methodological principles of science and integrated into its conceptual structure. If the opening applicants cannot overcome this bar, their work is deprived of the chance of recognition.

This story began three years ago. On March 8, 2002, an article appeared in the American journal SCIENCE, which even before the publication caused fierce disputes in the scientific environment. Its authors claimed that they managed to react the thermonuclear synthesis on a simple installation built in the Ok-Ridge National Laboratory.

It has long been known that under the influence of ultrasound, the smallest bubbles form in the liquid, which instantly collapse, strongly warm up and emit very short light flashes. This physical effect is called sonoluminescence . Jesus engineer Ruzi Talyayarkhan and his colleagues decided to use it to launch a thermonuclear reaction. They passed ultrasound through a cylindrical vessel with chilled liquid acetone, in the molecules of which hydrogen was replaced by its heavy isotope - deater. The formula of conventional acetone is C3H6O, and its “heavy” analogue is C3D6O (C - carbon, h - hydrogen, o - oxygen, d - deater). The novelty of the experiment was that the container with acetone was treated with flows of fast neutrons. The article said that a secondary neutron radiation arose in an irradiated liquid, as well as a certain number of tripi nuclei, an ultra -leisure unstable hydrogen isotope. Such a result, in principle, could be explained by the fact that pairs inside the bubbles were heated to about ten million degrees. At such a temperature, a thermonuclear synthesis of tritius from the nuclei of the deater is possible, and this process should just be accompanied by the emission of neutrons. Physicists from OK Ridge interpreted their results.

It is easy to imagine that the appearance of work with such announcements was fraught with considerable noise. Many experts resolutely objected to her appearance in print even before the magazine exit from the printing house. When the editors of Science nevertheless gave the go -ahead for the publication, and the journalists spoke that humanity would soon receive an inexhaustible source of pure and cheap energy, these protests only intensified. The article by Talyayarkhan and his comrades (and among them was the Russian physicist Robert Nigmatulin) immediately forced to recall the quickly bursting sensation of thirteen years ago. In 1989, a physicist from Britain Martin Fleischmann and his American student and colleague Stanley Pons allegedly discovered thermonuclear reactions accompanying the most common electrolysis of water. True, the electrolyte was still not ordinary water, but heavy, D2O, the electrodes were made of precious metals, platinum and palladium. Messages about such an unusual physical phenomenon, which was dubbed by a cold thermal unit, immediately got to the first pages of newspapers and in the prime time of television. However, the "great discovery" turned out to be a soap bubble, and soon they forgot about it.

I must say that the conclusions of the Ok-Riga physicists still sounded more believable. Both theoretical calculations and experimental data show that light nuclei can merge into more severe (this is thermonuclear synthesis) only at temperatures of millions of degrees. The same astrophysicists say the same, because thermonuclear reactions serve as the main source of stars. So the allegations of the possibility of thermonuclear reactions at indoor temperatures were perceived by specialists about the same as reports that the Earth rests on four elephants. Talyayarkhan and co -authors did not talk about any cold thermal unit, they believed that they carried out a “standard” high -temperature thermal unit, only in a non -standard way - not in a tokamak or other plasma reactor, but in a jar with heavy acetone. However, other scientists soon repeated these experiments and found neither tritium nor neutrons. In a professional environment, the opinion quickly triumphed that the Ok-Riga experimenters worked illiterate and their conclusions were not worth a sorted egg. In addition, at that time, the American Congress was just discussing the financing of the construction of an international thermonuclear reactor (ITER project). Both physicists and large cones from the Ministry of Energy feared that the hype around the cheap "bubble" thermal will prompt legislators to cut funds for this expensive program. In general, a sensational article in Science a year after publication was perceived by the absolute majority of specialists as an annoying curiosity.

But now something has changed. The stubborn Talyayarkhan did not abandon his experiments (Nigmatulin continues to cooperate with him). Last year, his group published in the prestigious Physical Review an article with the presentation of new results obtained on the same installation, but on the basis of a modified methodology. About a year have passed since then, but the experts seemed to have not yet found any mistakes in it. Moreover, these studies are subsidized by a very, very serious organization, the management of promising defense projects of the US Department of Defense, The Defense Advance Research Projects Agency. This is the Pentagon unit (in the abbreviation of Darpa) often allocates funds for semi -fantastic projects, but still does not throw money into the wind.

We will talk about what DARPA has interest in the work of Talyayarkhan (by the way, he has now moved from Ok-Riga to the University of Pardyu in Indiana), we will talk later. Now let's do physics. So, Sonoluminescence is the generation of light quanta inside the cavitic vesicles that occur in liquids under the influence of ultrasound waves. It was opened in the thirties of the twentieth century, but the physical mechanism of this phenomenon was understood only after six decades. This became possible primarily thanks to the works of the American physicist Felip Gaitan, who learned to “lock” bubbles in standing sound waves and thereby control their expansion and compression to some extent. Now it is considered proven that in the final phase of collapse the bubbles are compressed at a speed of one to one and a half kilometers per second, which is three to four times higher than the sound speed in the liquid. This leads to the emergence of shock waves, which very much heat the gases inside the bubble - at least to ten thousand kelvins. Calculations show that in the area of ​​the front wave front, the temperature of the medium can reach several hundred thousand degrees, it is possible that even to a million. This is still not enough to arson a thermonuclear reaction, but the distance is not so great.

Now let's move on to the experiments of the Talyayarkhan group, during which the fluid saturated with cavitation bubbles was irradiated by a stream of fast neutrons. This was done in order to reduce the size of the bubbles. The equipment for the study of sonoluminescence forms bubbles with a diameter of about 20 micrometers. As happens with cavitation, first the bubbles expand, and then tighten and collapse. For some reasons, the irradiation of neutrons leads to the emergence of vamigations with a diameter of no more than a few nanometers. Such nanopuses grow much more intensively than ordinary, "immunebrone" - not ten times, like those, but about ten thousand. Then, in the compression phase, they are collapsed more sharply, and, therefore, heats up harder. Talyayarkhan and his colleagues hoped that such a super -collapse could just heat the inside of the bubbles to thermonuclear temperatures. In this case, two deerial nuclei could, in a collision, form the core of tritius plus the core of ordinary hydrogen (in other words, proton). In another channel of the thermonuclear reaction, helium nucleus plus free neutrons are born. Since the Ok-Ridge physicists believed that in the first experiments they managed to register tritius and secondary neutrons, they claimed that thermonuclear reactions were lit inside the nanopoudycels.

As already mentioned, experts did not consider these conclusions convincing and could not confirm them in control experiments. At the same time, the opinion was triumphed that the neutron radiation observed by the Talyarhan group was not thermonuclear - these were just primary neutrons, reflected from the walls of the bubbles. However, Talyayarkhan and his like -minded people were not going to retreat. For new experiments, they used tracking equipment, which allowed to continuously measure the number of neutrons that leave the container with acetone. As a result, it turned out that the reflection of primary neutrons really occurs, but it quickly fades. And the neutron stream leaving the container suddenly intensifies and gives two peaks. According to the experimenters, it is these neutrons that are born during thermonuclear reactions that occur during the collapse of nanopoudy. If the experience was made in such a way that the primary neutron impulse did not start the birth of nanopoudyrs, these peaks did not arise at all, although the reflected neutrons were still recorded. Talyayarkhan and his colleagues believe that now the presence of a bubble thermal unit has been proven quite reliably.

And these arguments have already convinced many. In particular, Larry Krum, one of the main critics of the first article in Science, not only agreed with the current conclusions of the former opponents, but even came up with a theoretical model that explains the appearance of a large number of thermonuclear neutrons - about ten thousand for each chollapsized nanopouder. This is how it looks in a modified form. As a result of irradiation by primary neutrons, nanopuses are born not by one by one, but by accumulations, and they emit neutrons almost simultaneously. Each cluster has about a thousand bubbles, each bubble gives birth to about ten neutrons - in total and it turns out ten thousand.

So, it turns out that the problem of implementing a controlled thermonuclear reaction has already been resolved and the ITER project can be canceled? We will not rush. Firstly, the existence of a bubble thermal unit is still not proven, although it looks much more believable than three years ago. Recently, the head of the university nuclear technology department, Pardyu Lefteri Tsukalos and his colleagues repeated the experiments of the Talyayarkhan group and, according to information leaked to print, confirmed the birth of a tritium. These results have not yet been published, but Professor Tsukalos intends to report them at a conference in France in October. But even if the bubble thermal unit is not a fiction, but the reality, a miniature installation of Talyyarkhan, is far from a reactor. So far, no one can say whether it is possible to reproduce this effect on such a scale that will allow it to be used to produce energy. The prospect of using such devices as inexpensive neutron generators is more real, the need for which is quite large.

Why did these experiments receive the Pentagon's support? Of course, the hope for the creation of thermonuclear energy itself is a sufficient incentive, but so far it is quite ephemeral. However, with the help of a bubble thermal unit you can get a radioactive tritius, and this is a dangerous weapon in the hands of terrorists. So it is possible that Darpa pays to make sure of the reality or unreality of this effect, the military must have blanks for all occasions.

Sources:

RP Taleyarkhan, Js Cho, SD West, RT Lahey, Jr., Ri Nigmatulin, and Rc Block

Additional Evidence of Nuclear Emissions During Acoustic Cavitation

Physical Review E, 69, 036109 (2004)

Justin Mullins

Harnessing Bubbles to Trigger Nuclear Fusion

New Scientist, 22 January 2005