To the popular imagination, antimatter is a nigh-magical substance. In various fictional sources, it has been used to warp time and space, destroy whole worlds, and almost kill the Pope. But it is also a very fundamental physical phenomenon in the real world, one responsible for much of our understanding of the subatomic world. Links to pages with much more detailed explanations into the nature and workings of antimatter are provided at the end of this article.
This article addresses the use of antimatter in power generation only. Use of antimatter in other applications, such as space propulsion or weaponry, will be covered in other articles.
Antimatter particles have the same mass as normal matter particles, but opposite electrical charges. Matter and antimatter mutually annihilate each other on contact and are converted to pure, 100% energy. This energy usually takes the form of a combination of gamma rays, neutrinos, antineutrinos, and pions. This total energy conversion makes forms of antimatter very attractive as a fuel. One gram of antimatter, annihilated with one gram of normal matter, can generate as much energy as 23 Space Shuttle external fuel tanks. A kilogram of matter and antimatter smashed together would produce an explosion equal to approximately 43 million tons of TNT.
Antimatter was first postulated by physicist Paul Dirac in 1928, and in 1932 the first antiparticle, the positron, was detected. Other antiparticles were discovered in the decades after as nuclear accelerators became more powerful and sophisticated. In 1995, the first antihydrogen atoms (composed of an antiproton nucleus and an orbiting positron) were created at the CERN facility in Europe. Antimatter traps--devices that use magnetic and electrical fields to hold antiparticles and antiatoms for extended periods of time--have also steadily improved over the decades. Today, investigations into the nature and use of antimatter is studied at many facilities around the world.
Though antimatter is much rarer than its twin, it is readily found in certain circumstances in nature (for example, it is a natural byproduct of proton chain fusion which powers most stars, and the annihilation of these antiparticles actually accounts for about 11% of the Sun’s energy output.) However, it has proven extremely difficult to manufacture antimatter in quantity on Earth. It currently costs far more in terms of energy and resources to create an antiparticle than the amount of energy one could ever hope to get back from it.
This combined with extremely low production rates even using the most advanced equipment keeps antimatter from being considered seriously as a means of power production, even for the foreseeable future. At CERN’s current rate of antiproton production, it would take about 2 billion years to create 1 gram of antihydrogen. Even if production time could be accelerated to within a few years, it would still cost over $62 trillion in resources. Prospects for antimatter power any time within this century looks grim especially when compared to other cheaper, more readily available sources of power that will be available as alternatives.
However, antimatter may eventually come into its own if production techniques can be ramped up considerably. How this can be done is usually left vague, even by experts in the field. The assumption seems to be in creating a steady progression of ever more powerful, compact, and advanced accelerators in the coming decades and centuries. Whether there may be a practical upper limit to how much antimatter can be artificially produced, or if enough could ever be produced to make antimatter an economically practical power source, is a complete unknown. One can be heartened somewhat, however, that antimatter progression has grown at near exponential rates since the discovery of the first artificially produced antiparticle in the 1950s.
Even if the creation and storage of antimatter fuel remains difficult, the availability of a such potent, compact energy source may outweigh the production cost in certain circumstances. These may include deep space propulsion and power, weapons, and high-end scientific applications.
Problems with antimatter go beyond just production limits. It has also proven particularly difficult to store for significant amounts of time. For obvious reasons, it cannot be allowed to come into contact with normal matter, so antimatter particles must be stored in Penning traps, which suspend them in vacuum by a combination of electrical and magnetic fields. Charged particles respond readily to these fields, but add the complication of repulsing each other, which in turn makes storing them even more difficult, especially in large numbers.
Uncharged antiparticles such as antihydrogen require even more complicated radiative atomic traps that use the dipole moment of the atoms to suspend them, or lasers to hold a very small amount of particles in place by balancing them in between the intersecting beams. Larger antiatoms such as antihelium could be made into ions (antiions?) which could respond better to conventional penning traps, but would also run into repulsion problems.
Cooling the antimatter to cryonic temperatures by various techniques could prove useful, especially if antihydrogen could be made into a somewhat more manageable solid like antihydrogen ice.
Another hitch in using antimatter as a power source is that not all energy released by matter/antimatter annihilation is readily usable. Depending on the type of reaction used (positron/electron, proton/antiproton, hydrogen/antihydrogen, etc), up to half the energy released may be neutrinos, with the rest being gamma rays and pions.
Pions, being charged particles, can be readily used to generate power by surrounding the reaction chamber with a like-charged electrical field. The pions and field repel each other, and the expansion and contraction of the field provided by the ‘push’ of the pion flux against the field can be used to create electrical current. Gamma rays would be more difficult to harness, but can either be focused with advanced mirrors, or at least used to heat a working fluid.
The neutrinos, however, are small, nearly massless ghost particles that can flash through a light year’s worth of solid lead and never impact anything. Any neutrinos created by matter/antimatter annihilation is pretty much considered lost. Even at a loss of 25 to 50 percent of its energy output, however, antimatter still produces far more power gram for gram than any other type of fuel.
Antimatter reactors would produce a great deal of radiation from pion and gamma ray leakage, and would require very heavy shielding and safety measures, much more so than modern day nuclear reactors.
ADVANCED PORTABLE ANTIMATTER TRAPS
Tech Level: 14
|Diagram of a modern day Penning trap.|
Advanced techniques in manipulating powerful electromagnetic fields to trap highly energetic plasma, such as those being researched for use in plasma rockets and fusion generators, can also be modified to build better, more compact, and more efficient antimatter traps. Also useful would be more advanced particle cooling techniques and more efficient portable energy sources that keep the unit working longer, another technology being actively purseud.
Though advanced portable traps will not make antimatter economically practical, they will go a long way in making antimatter actually useful for a number of applications where profits may not be the primary concern, such as deep space propulsion and weaponry.
This is the simplest and most easily achievable type of antimatter reactor. Antimatter particles such as antiprotons are injected into a working medium like water or liquid hydrogen. Just enough antiparticles are used so that the energy released by their annihilations superheats the liquid, turning it to gas or steam; this in turn is used to turn turbines to produce electricity.
If enough antimatter is used, the liquid fuel may also be superheated into plasma and can be used for space propulsion and other applications.
The antimatter may either come from a reserve in a penning trap or may be manufactured on the spot as needed in an attached accelerator. The potency of the generator can be adjusted by releasing more or less antimatter into the fluid. More antimatter means more annihilations and much more heat added to the fluid, which results in much more energetic steam.
This technology assumes that antimatter production is considerably more successful at Tech level 14 than it is today, and that the generator will have access to adequate amounts of antimatter fuel for its needs. The cost of antimatter is still expected to be prohibitively high for means of creating a widely-available economical energy source, but in certain specialized circumstances (such as being in deep space with no other fuel available) these type of generators may prove invaluable.
At higher Tech Levels, if antimatter ever becomes relatively cheap to manufacture, these type of devices may become commonplace.
This is a modification of a propulsion scheme considered for the AIMSTAR project, detailed in the article for Antimatter Rockets linked to at the bottom of this page.
A penning trap is set up to hold a large population of antiprotons. Pellets of fission/fusion fuel are "shot" through the trap, basically compressing onto the outer layer of the antiparticle mass in the trap. The energy of the antimatter annihilations initiates a fission reaction, which in turn sparks a fusion burn in the compressed fuel mix. This in turn creates superheated plasma which then can be used to generate power.
After each such "burn" the antiprotons in the penning trap are allowed to reset back to their original configuration, minus about 0.5% of their original mass, which was used up in the burn cycle annihilations. After every 50 burns, new antiprotons are injected into the magnetic bottle to reload the trap. The reactor would fire at about 200 burns per second.
Fuels being considered include a deuterium-tritium (DT) mix and a deuterium-helium-3 (DHe3) mix. The DT fuel provides a higher burn and more energy, but the tritium for the DT mix is much harder to obtain (at least at projected Tech level 15 capabilities) than helium-3 and the reaction produces far more radiation than the DHe3 fuel. Helium-3 can be readily mined from the surface Moon and (presumably) other space rocks near the Sun that lack an atmosphere, which would include Mercury, Phobos, Deimos, and perhaps countless asteroids. Tritium would either have to be manufactured or skimmed from the atmospheres of gas giants.
The main advantage of this type of reactor would be its potential low mass and compact size for its theorized enormous energy output, especially given the capabilities of Tech Level 15 technology. This would make it valuable for space-based applications beyond simply propulsion. Again, though, the main limiting factor to creating this type of reactor may be the economics of antimatter production and storage.
These are the types of antimatter power sources usually depicted in science fiction sources, most famously to power the starships in Star Trek. They generally use direct annihilation of equal parts of matter and antimatter, and harvest the full power of the pion flux and gamma rays generated. They are also sometimes called MAM or M/AM (Matter/AntiMatter) reactors.
The warp cores in Star Trek are probably the best detailed type of MAM reactor in science fiction. They are a bit misnamed; the warp core in and of themselves do not warp space, but instead provide the power for the engines to do so.
A warp core MAM reactor uses streams of tightly-contained deuterium and antideuterium annihilations to superheat a working medium surrounding the reaction, creating a highly energetic plasma which is in turn is used to actually power the ship’s needs (phasers, sensors, warp drive, etc.) They produce an extreme amount of power; one source quoted the maximum power output of the Enterprise D at 4.77 million terawatts over a 12 hour period. Compare this to the total world output of energy of modern day Earth, which is typically about 15 terawatts. Of course, the Enterprise D would have to consume thousands of tons of antimatter to produce this, but given the ship’s size and very high Tech Level (about 21) it doesn’t seem unreasonable for them to have that much stored on board or to have the means to produce it.
One potential problem that arises with this type of reactor is keeping the flow of the reaction steady. The explosions caused by the mutually-annihilating particles are so intense they could disrupt the incoming flow of reactants, diminishing the production of power, and perhaps stopping it altogether. The same technologies used in advanced fusion reactors, extremely powerful magnetic fields and moving the reactants at very high velocities (perhaps even near light speed) in order to overcome the back pressure of the annihilation flux, may be required. The system may also be rapidly pulsed. Because the pions and gamma rays travel outward from the annihilation point at the speed of light or very near to it, the remnants of the explosion would clear the reaction chamber quickly enough that the engine could probably be pulsed thousands if not millions of times a second without a significant loss in efficiency.
These are devices, either advanced particle accelerators, colliders, nuclear reactors, advanced quantum manipulators, or some esoteric combination of all of those, designed to produce large amounts of antimatter for a variety of applications. In the universe of Star Trek, antimatter is produced at large, advanced, planet-bound facilities, but starships carry their own miniature antimatter factories for use when their stored supply runs low.
It may still require vast amounts of input energy as large populations of subatomic particles are still smashed together at near light speed. Or it may require an as yet unguessed-at quantum trick, using sophisticated knowledge of the quantum world but low amounts of energy to simply flip the charge on an electron from negative to positive. The latter technique how antimatter is produced in quantity in the Star Trek universe.
Because of the vague nature of how these devices would work, their placement on the Tech Level scale is fairly arbitrary. Its placed at where antimatter technology begins to become commonplace as typically portrayed in science fiction, usually late in the Space Opera era (Tech levels 19-20.)
Today, the entire world output of antimatter can be measured in nanograms per year. An antiparticle factory would be able to produce millions upon millions of times that, creating thousands of tons per year, perhaps more.
Given sufficiently advanced technology, its seems possible that antimatter production can eventually be ramped up to such spectacular levels. But whether it could ever be made economical, where it would cost less in resources to produce the antimatter than the value of the energy one could extract from it, is another matter. While antimatter production at this Tech Level may prove to be truly impressive, it may still not be able to penetrate the break-even point.
However, this may only be true of direct hard costs. The indirect, ‘soft’ benefits of such a technology may still make it worth the investment. The availability of so much antimatter, even if comparatively expensive in and of itself, would transform any society that had access to it. It would find applications in many different fields and open up many potential markets, technological and otherwise. For example, it may well become the deep space propulsion technology of choice, especially in the vast voids of interstellar space where low fuel mass and high energy returns would be paramount. That in turn may open up new resources (such as Oort cloud comets or quicker access to other star systems) which in turn would generate profitable returns. So even though the direct return on investment, production cost vs energy return, may not reach the break-even point, the larger benefits of the technology in the society at large may make investing in the technology worthwhile.
Speculative Antimatter Technologyhttp://www.centauri-dreams.org/?p=8081 http://ffden-2.phys.uaf.edu/213.web.stuff/Scott%20Kircher/ http://orbitalvector.com/Deep%20Space%20Propulsion/Antimatter%20Rockets/Antimatter%20Rockets.htm http://memory-alpha.org/wiki/Warp_core http://www.ex-astris-scientia.org/inconsistencies/treknology-power.htm