Our article is devoted to the history and General principles of the synthesis of a device such as a thermonuclear bomb, sometimes called hydrogen. Instead of energy release of an explosion by the splitting of nuclei of heavy elements, like uranium, it generates even greater quantity by fusing nuclei of light elements (e.g. hydrogen isotopes) to one severe (e.g., helium).
Why is nuclear fusion preferred?
In thermonuclear reactions, consisting in the fusion of the nuclei involved in the chemical elements, generates significantly more energy per unit mass of a physical device than in a pure atomic bomb, which is implementing a nuclear fission reaction.
In a nuclear bomb fissile nuclear fuel quickly, under the action of the energy of detonation of conventional explosives combined in a small spherical volume, where he created his so-called critical mass and start a fission reaction. In this case many of the neutrons released from fissioning nuclei, will cause the division of other nuclei in the fuel mass that also emit additional neutrons, which leads to a chain reaction. It covers not more than 20 % of the fuel before the bomb blows up, or possibly much less if conditions are not perfect: atomic bombs Boy, dropped on Hiroshima, and Fat man hit Nagasaki, efficiency (if such a term actually can be applied to them) had only a 1.38% and 13%, respectively.
A merger (or fusion) of the nuclei cover the entire mass of the charge bomb and lasts until neutrons can find more unreacted thermonuclear fuel. Therefore, the mass and explosive power of such a bomb is theoretically unlimited. Such a merger could theoretically continue indefinitely. Indeed, a thermonuclear bomb is one of the potential doomsday devices which can destroy all human life.
What is the fusion reaction of nuclei?
The fuel for the nuclear fusion are the hydrogen isotopes deuterium or tritium. The first differs from ordinary hydrogen that in its core, but one still contains proton and neutron and the tritium nucleus has two neutrons. In natural waters is one atom of deuterium is necessary for every 7000 atoms of hydrogen, but from its quantity. contained in a glass of water, can be the result of thermonuclear reactions to obtain the same amount of heat as the combustion of 200 liters of gasoline. At a meeting in 1946 with politicians, the father of American hydrogen bomb, Edward teller emphasized that deuterium gives more energy per gram of weight than uranium or plutonium, however, is worth twenty cents per gram compared to several hundred dollars per gram of fuel for nuclear fission. Tritium in nature in the free state does not occur, so it is much more expensive than deuterium, with a market price of tens of thousands of dollars per gram, however the greatest amount of energy is released in a fusion reaction of deuterium and tritium, which produces helium nucleus and releases a neutron carrying away the excess energy of 17.59 MeV
D T → n 4 is Not 17,59 MeV.
This reaction is shown schematically in the figure below.A lot or a little? As you know, everything is relative. So, the energy of 1 MeV is about 2.3 million times more than is released when burning 1 kg of oil. Hence the only fusion of two nuclei of deuterium and tritium releases as much energy as is released when burned 2,3∙10 6 ∙17,59 = 40,5∙10 6 kg of oil. And we are talking about only two atoms. Can you imagine how high were the stakes in the second half of the 40-ies of the last century, when the United States and the Soviet Union turned the work, which resulted in a thermonuclear bomb.
How it all began
Back in the summer of 1942 at the beginning of the project to create the atomic bomb in the United States (Mangatangi project) and later in the same Soviet program, long before it was built the bomb based on the fission of uranium, the attention of some of the participants was drawn to the device that can use a much more powerful fusion reaction of nuclear fusion. In the USA a supporter of this approach, and one might even say, his apologist, was already mentioned above, Edward teller. In the USSR this direction was developed by Andrei Sakharov, the future academician and dissident.
For the teller of his fascination with nuclear fusion in the years of the creation of the atomic bomb played a rather disservice. As a member of Manaenkova project, he's persistent, called for the redirection of funds for the implementation of their own ideas, the purpose of which was hydrogen, and thermonuclear bomb that was not liked by the user and caused tensions. Because at that time the fusion line of research was not supported, after the creation of the atomic bomb, teller left the project and was engaged in teaching and research of elementary particles.
However, the cold war, and most of all the creation and successful test of a Soviet atomic bomb in 1949, to become a fierce anti-Communist teller new chance to realize their research ideas. He returned to the Los Alamos laboratory, where he created the atomic bomb, and along with Stanislaw Ulam and Cornelius Everett shall proceed to a settlement.
The principle of thermonuclear bomb
In order to start the fusion reaction of nuclei, it is necessary to immediately heat the charge bomb to a temperature of 50 million degrees. Diagram of the h-bomb, teller proposed uses for this the explosion the small nuclear bomb that is inside the case of hydrogen. It can be argued that there were three generations in the development of its project in the 40-ies of the last century:
- option teller, known as the “classical super”
- more complex, but also more real designs from several concentric spheres;
- the final version of the design of the teller-Ulam, which is the basis of all operating systems today thermonuclear weapons.
The same stages of planning have passed and thermonuclear bombs of USSR, the origins of which was Andrei Sakharov. He, apparently, quite independently from the Americans (which cannot be said about the Soviet atomic bomb created by the joint efforts of scientists and spies, who worked in the US) passed all the above stages of the design.
The first two generations had the property that they had a sequence of concatenated “layers”, each of which has reinforced some aspect of the previous one, and in some cases established feedback. There was no clear separation between the primary atomic bomb and a thermonuclear secondary. In contrast, the scheme of a thermonuclear bomb development of the teller-Ulam sharply distinguishes the primary explosion, secondary, and, if necessary, additional.
The device of a thermonuclear bomb by the principle of Teller-Ulam
Many of the details remain classified, but there is sufficient confidence that all currently available thermonuclear weapons uses as a prototype device created by Edward Tellers and Stanislaw Ulam, in which the atomic bomb (i.e. the primary charge) is used to generate radiation compresses and heats the fusion fuel. Andrei Sakharov in the Soviet Union, apparently independently invented a similar concept, which he called the “third idea.”
Schematically, the device of a thermonuclear bomb in this embodiment shown in the figure below. It had a cylindrical shape, with approximately spherical primary atomic bomb at one end. Secondary thermonuclear charge in the first non-industrial samples, were from liquid deuterium, some later, it became solid from a chemical compound called lithium deuteride.
The fact that industry has long used lithium hydride LiH babalonas for transportation of hydrogen. The bomb (this idea was first used in the USSR) just offered to take the place of ordinary hydrogen, its isotope deuterium, and to combine with lithium, as with solid thermonuclear charge to carry the bomb much easier.
In the form of secondary charge was a cylinder placed in a container with a lead (or uranium) shell. Between charges is a neutron shield protection. The space between the walls of the container with the fusion fuel and the body of the bomb is filled with special plastic, usually polystyrene. The body of the bomb is made of steel or aluminum.
These forms have changed in recent designs, such as the one shown in the figure below.In it the primary charge flattened like a watermelon or a ball in American football, and the secondary charge – spherical. Such forms much more efficiently fit into the inner volume of the conical missile warheads.
A sequence of thermonuclear explosion
When the primary atomic bomb detonates, in the first moments of this process generates powerful x-ray radiation (a neutron flux), which is partially blocked by the shield, neutron shield, and is reflected from the inner lining of the housing, surrounding a secondary charge, so that the x-rays fall on it symmetrically along its length.
At the initial stages of the thermonuclear reaction, the neutrons from the atomic explosion are absorbed by the plastic filler in order to prevent too rapid heating of the fuel.
X-rays cause the appearance of initially dense plastic foam filling the space between the housing and the secondary charge, which quickly turns into a plasma, heating and compressing the secondary charge.
In addition, x-rays evaporate the surface of the container surrounding a secondary charge. Symmetrically relative to the evaporating of the charge of the substance container gets some momentum from its axis, and layers of secondary charge according to the law of conservation of momentum gain momentum, directed toward the axis of the device. The principle here is the same as in the rocket, only if you imagine that rocket fuel spreads symmetrically from its axis, and the housing is compressed inwards.
As a result of this compression of thermonuclear fuel, its volume is reduced thousands of times, and the temperature reaches the level of the beginning a fusion reaction nuclei. There is an explosion of a thermonuclear bomb. The reaction is accompanied by the formation of tritium nuclei that fuse with the deuterium nuclei, initially available in the secondary charge.
The first secondary charges were built around a core core of plutonium, known informally as the “candle”, which entered the nuclear fission reaction, ie, carried out an additional nuclear explosion to further raise the temperature to guarantee the beginning of a fusion reaction nuclei. Currently, it is believed that a more effective compression system has eliminated the "candle", allowing further miniaturization design of the bomb.
So called American tests of thermonuclear weapons in the Marshall Islands in 1952, during which it was exploded the first thermonuclear bomb. It was called Ivy Mike and was built according to the standard scheme of the teller-Ulam. Its secondary thermonuclear charge was placed in a cylindrical container, which is a thermally insulated Dewar with fusion fuel in the form of liquid deuterium along the axis which passed the "candle" of 239-plutonium. Dewar, in turn, was covered with a layer 238-uranium weighing more than 5 metric tons, which is in the process of the explosion evaporated, providing symmetric compression of the fusion fuel. Container with primary and secondary explosive charges were placed in a steel casing 80 inches wide and 244 inches long with walls 10 to 12 inches thick, which was the largest example of forged products up to that time. The inner surface of the casing was lined with sheets of lead and polyethylene to reflect radiation after the explosion of the primary charge and create a plasma, warming up a secondary battery. The entire device weighed 82 tons. View of the device shortly before the explosion shown in the photo below.
The first test of a thermonuclear bomb, took place on 31 October 1952 the power of the explosion was 10.4 megatons. Attal Eniwetok, where it was produced, was completely destroyed. The time of the explosion shown in the photo below.
USSR gives a symmetrical answer
Fusion US primacy did not last long. 12.08.1953 on the Semipalatinsk test site was tested the first Soviet thermonuclear bomb RDS-6, developed under the guidance of Andrei Sakharov and Yuli Khariton.From the description above it becomes clear that the Americans on Enewetak was detonated the actual bomb is not as ready to use ammunition, but rather a laboratory device, bulky and very imperfect. The Soviet scientists, despite the small capacity of 400 kg, has experienced quite finished warhead with a thermonuclear fuel in the form of solid lithium deuteride rather than a liquid deuterium as the Americans. By the way, it should be noted that the composition of the lithium deuteride is used only in the isotope 6 Li (this is due to the passage of the thermonuclear reactions), but in nature it is mixed with the isotope 7 Li. So it built a special production for the separation of lithium isotopes and selection of only 6 Li.
Achieving maximum power
Then followed a decade of uninterrupted arms race during which the power of thermonuclear weapons continuously increased. Finally, 30.10.1961 in the USSR on the Novaya Zemlya in the air at a height of about 4 km was exploded the most powerful thermonuclear bomb ever built and tested, known in the West as "Tsar-bomb".
This three-stage munition was developed actually as 101,5-megaton bomb, but the desire to reduce radioactive contamination of territory has forced the developers to abandon the third stage with a capacity of 50 megatons to reduce the estimated power of the device to 51.5 megatons. 1,5 megatons was the power of the explosion of a primary atomic charge, and the second fusion step was to give another 50. The real power of the explosion amounted to 58 megatons.The appearance of the bombs shown in the photo below.
The consequences were spectacular. Despite the substantial height of the explosion in the 4000 meters, an incredibly bright fireball with the bottom edge almost reached Earth, and the top rose to a height of more than 4.5 km, and a Pressure below the break point it was six times higher than the peak pressure of the explosion in Hiroshima. The flash of light was so bright that it was visible at a distance of 1,000 kilometers, despite cloudy weather. One of the participants in the test saw a bright flash through dark goggles and felt the effects of a thermal pulse even at a distance of 270 km. photo of the explosion are shown below.
It was shown that the power of a thermonuclear charge really has no limitations. It was enough to perform the third step, and the estimated capacity would be achieved. But you can increase the number of steps and then, as the weight of the "Tsar bomb" was no more than 27 tons. The form of this device shown in the photo below.
After these tests, it became clear to many politicians and the military both in the USSR and in the USA that the nuclear arms race had come to an end and that it must be stopped.
Modern Russia has inherited the nuclear Arsenal of the USSR. Today a thermonuclear bomb Russia continue to serve as a deterrent to those who aspire to world hegemony. Let's hope that they will play a role only as a deterrent and will never be blown up.
The sun as a fusion reactor
It is well known that the temperature of the Sun, or rather its nucleus, reaching up to 15000000 °K, is maintained by the continuous flow of thermonuclear reactions. However, all that we could learn from the previous text, speaks about the explosive nature of such processes. Then why the Sun does not explode like a thermonuclear bomb?
The fact that the huge proportion of hydrogen in the composition of the solar mass, which reaches 71 %, the proportion of its isotope deuterium, the nucleus of which can participate in reactions of thermonuclear synthesis, is negligible. The fact that the nucleus of deuterium themselves are the result of the fusion of two nuclei of hydrogen, and not just the merge, and with the collapse of one of the protons into a neutron, a positron and a neutrino (known. beta decay), which is a rare event. Thus formed the nucleus of deuterium divided by the volume of the solar core rather evenly. So when her sheer size and weight of the individual and rare foci of thermonuclear reactions is relatively small power like smeared around its core of the Sun. Released during these reactions heat is clearly not enough to instantly burn all the deuterium in the Sun, but enough to be heated to temperatures that support life on Earth.