Unlike other physical reactions, matter-antimatter annihilation results in the release of all of their mass-energy equivalence as energy, without loss. This very quickly made it a science fiction concept, a field in which antimatter is often used as a source of energy for weapons or as fuel. But what about the scientific reality of such uses? Can antimatter be used as a short-term weapon?
The advantage of the matter-antimatter reaction for a theoretical weapon is obvious at first glance:the energy released corresponds to the exact sum of their mass-energy equivalent. In other words, the equivalence E =mc² is achieved completely, without any loss in the process. Such a weapon would thus have a much better energy yield than the most efficient current thermonuclear weapons, whose yield is between 7 and 10%.
The matter-antimatter collision therefore fully releases the mass energy of the two components. In terms of energy, 1 gram of this reaction produces approximately 1.8×10 14 J, or about 43 kilotons. If on paper these parameters prove to be extremely interesting for any institution wishing to produce antimatter weapons, numerous technical and economic constraints make these prospects impossible in the short term.
Today, antimatter is produced artificially in only two known ways:within particle accelerators and by bombardment with high-energy particles. Both of these processes have extremely low yield and poor production efficiency. The global antimatter production rate is only between 1 and 7 nanograms per year. In 2008, for example, CERN's Antiproton Decelerator produced only a few picograms of antiprotons.
To develop an antimatter bomb with a power equivalent to a 10 megaton nuclear bomb, i.e. 250 grams of antimatter, with current production rates, it would take about 2.5 billion years of intensive global production. Thus, to make a bomb equivalent to the Hiroshima bomb, it would require 500 mg of antimatter, or 2 million years of production at CERN.
Also, the very small antiproton production cross section in high-energy nuclear collisions makes it very difficult to improve the rate of antimatter production with current technologies. Although specialized laboratories like the Lawrence Livermore National Laboratory have managed to increase the amount of positrons produced by bombarding gold targets with short-pulse lasers, these rates are still far too low.
The other technological constraint is the storage of antimatter. Considering that it is systematically annihilated with ordinary matter, it is impossible to use conventional storage systems.
Today, antimatter produced in particle accelerators is stored and stabilized in devices called Penning traps; vacuum chambers in which charged antiparticles are trapped by a high-intensity electromagnetic field.
Furthermore, the core of any antimatter weapon must possess a globally neutral electrical charge in order to be compacted to the maximum. For example, a heart composed exclusively of antiprotons (positive electrical charge) would be too large due to the electrical repulsion of the antiprotons. It would therefore be necessary to use antihydrogen atoms whose stability is extremely difficult to maintain (cooling close to absolute zero coupled with a Penning trap).
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Finally, the risk of accidental matter-antimatter annihilation is high. If the storage device malfunctions, this would cause the complete annihilation of the structure and the external release of all the energy resulting from the reaction. By contrast, nuclear bombs only activate if the nuclear trigger is on; no thermonuclear reaction can occur if the activation is not done deliberately.
Along with the technological hurdles, there are also very strong economic constraints on the development of antimatter weapons. Today, the production of one gram of antimatter costs around 60 billion billion euros. At CERN, the production of a few picograms of antiprotons at the Antiproton Decelerator costs 18 million euros per year.
These totally prohibitive costs for the quantities produced (far too small for the smallest possible weapon) therefore make the development of antimatter weapons unviable in the short term. Even if it were possible to directly convert energy into particle-antiparticle pairs without any loss, a giant power plant generating a power of 2000 MWe would take 25 hours to produce only 1 gram of antimatter.
With an electrical energy cost of 45 euros/MWh, this would lead to a cost of 2.5 million euros per gram of antimatter. If this is not economically viable for a weapon, the balance sheet remains extremely interesting in terms of fuel for spacecraft. Indeed, NASA estimates that one milligram of antimatter would be enough for a probe to make a round trip to Pluto in a single year.
