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Antimatter: The Conundrum of Storage

Are we ever going to use antimatter to drive a starship? The question is tantalizing because while chemical reactions liberate about one part in a billion of the energy trapped inside matter — and even nuclear reactions spring only about one percent of that energy free — antimatter promises to release what Frank Close calls ‘the full mc2 latent within matter.’ But assuming you can make antimatter in large enough amounts (no mean task), the question of storage looms large. We know how to store antimatter in so-called Penning traps, using electric and magnetic fields to hold it, but thus far we’re talking about vanishingly small amounts of the stuff.

Moreover, such storage doesn’t scale well. An antimatter trap demands that you put charged particles into a small volume. The more antimatter you put in, the closer the particles are to each other, and we know that electrically charged particles with the same sign of charge repel each other. Keep pushing more and more antimatter particles into a container and it gets harder and harder to get them to co-exist. We know how to store about a million antiprotons at once, but Close points out in his book Antimatter (Oxford University Press, 2010) that a million antiprotons is a billion billion times smaller than what you would need to work with a single gram of antimatter.

Antihydrogen seems to offer a way out, because if you can make such an anti-atom (and it was accomplished eight years ago at CERN), the electric charges of positrons and antiprotons cancel each other out. But now the electric fields restraining our antimatter are useless, for atoms of antihydrogen are neutral. Antimatter that comes into contact with normal matter annihilates, so whatever state our antimatter is in, we have to find ways to keep it isolated.

A Novel Antihydrogen Trap

One solution for antihydrogen is being explored at CERN through the international effort known as the ALPHA collaboration, which reported its findings in a recent issue of Nature. Here positrons and antiprotons are cooled and held in the separate sections of what researchers are calling a Minimum Magnetic Field Trap by electric and magnetic fields before being nudged together by an oscillating electric field, forming low-energy antihydrogen. Keep the anti-atoms at low energy levels and although they are neutral in charge, they still have a magnetic moment that can be used to capture and hold them. Says ALPHA team member Joel Fajans (UC-Berkeley):

“Trapping antihydrogen proved to be much more difficult than creating antihydrogen. ALPHA routinely makes thousands of antihydrogen atoms in a single second, but most are too ‘hot’”—too energetic—“to be held in the trap. We have to be lucky to catch one.”

Image: Antiprotons and positrons are brought into the ALPHA trap from opposite ends and held there by electric and magnetic fields. Brought together, they form anti-atoms neutral in charge but with a magnetic moment. If their energy is low enough they can be held by the octupole and mirror fields of the Minimum Magnetic Field Trap. Credit: Lawrence Berkeley National Laboratory.

Clearly we’re in the earliest stages of this work. In the team’s 335 experimental trials, 38 antihydrogen atoms were recorded that had been held in the trap for about two-tenths of a second. Thousands of antihydrogen atoms are created in each of the trials, but most turn out to be too energetic and wind up annihilating themselves against the walls of the trap. In this Lawrence Berkeley National Laboratory news release, Fajans adds a progress update:

“Our report in Nature describes ALPHA’s first successes at trapping antihydrogen atoms, but we’re constantly improving the number and length of time we can hold onto them. We’re getting close to the point where we can do some classes of experiments on antimatter atoms. The first attempts will be crude, but no one has ever done anything like them before.”

Taming the Positron

So we’re making progress, but it’s slow and infinitely painstaking. Further interesting news comes from the University of California at San Diego, where physicist Clifford Surko is constructing what may turn out to be the world’s largest antimatter container. Surko is working not with antihydrogen but positrons, the anti-electrons first predicted by Paul Dirac some eighty years ago. Again the trick is to slow the positrons to low energy levels and let them accumulate for storage in a ‘bottle’ that holds them with magnetic and electric fields, cooled to temperatures as low as liquid helium, to the point where they can be compressed to high densities.

One result is the possibility of creating beams of positrons that can be used to study how antiparticles react with normal matter. Surko is interested in using such beams to understand the properties of material surfaces, and his team is actively investigating what happens when positrons bind with normal matter. As you would guess, such ‘binding’ lasts no more than a billionth of a second, but as Surko says, “the ‘stickiness’ of the positron is an important facet of the chemistry of matter and antimatter.” The new trap in his San Diego laboratory should be capable of storing more than a trillion antimatter particles at a time. Let me quote him again (from a UC-SD news release):

“These developments are enabling many new studies of nature. Examples include the formation and study of antihydrogen, the antimatter counterpart of hydrogen; the investigation of electron-positron plasmas, similar to those believed to be present at the magnetic poles of neutron stars, using a device now being developed at Columbia University; and the creation of much larger bursts of positrons which could eventually enable the creation of an annihilation gamma ray laser.”

An interesting long-term goal is the creation of portable antimatter traps, which should allow us to find uses for antimatter in settings far removed from the huge scientific facilities in which it is now made. Robert Forward was fascinated with ‘mirror matter’ and its implications for propulsion, writing often on the topic and editing a newsletter on antimatter that he circulated among interested colleagues. But he was keenly aware of the problems of production and storage, issues we’ll have to solve before we can think about using antimatter stored in portable traps for actual space missions. Much painstaking work on the basics lies ahead.

The antihydrogen paper is Andresen et al., “Trapped antihydrogen,” Nature 468 (2 December 2010), pp. 673–676 (abstract). Clifford Surko described his work on positrons at the recent meeting of the American Association for the Advancement of Science in a talk called “Taming Dirac’s Particle.” The session he spoke in was aptly named “Through the Looking Glass: Recent Adventures in Antimatter.”


Comments on this entry are closed.

  • Enzo March 11, 2011, 16:45

    I remember reading one way of confining anti-hydrogen : freezing it solid and than irradiating it with some electrons. This would annihilate some of the positrons, leaving it with a small charge. It could then be confined electrostatically , at very low temperature, in the vacuum.
    Annihilations would continue with stray atoms of normal matter but a very reduced rate.
    Regarding the positrons, they for exotic atoms with the electrons, at least temporarily. The two particles then spiral towards each other and then annihilate. Apparently it is possible to stabilize it with the appropriate electromagnetic fields.

    The following NIAC presentation of 2004 is very interesting :

    And it mentions stabilizing positronium for over a year. It also
    talks about positronic ramject etc. etc. It’s mostly pitched at the
    military (the ones with the money).

    I think tha tthe people involved in the talk are related to this company,
    Positronic Research :

  • Greg March 11, 2011, 17:03

    I’m curious, could you not use proton’s when mixed with positrons to “cool” them to lower energy levels? It would be much easier system to use I would think.

  • Rick York March 11, 2011, 18:39

    I’m not a physicist so the following may seem naive as well as foolish:

    Rather than trying to “trap” these particles, would it be possible to create these particles on demand while focusing them so that they collide far enough from the vessel to provide propulsion safely? This wouldn’t be much use for a static building like a power plant. But, for pushing a vehicle which is already in motion, it does seem like an interesting notion.

    I would appreciate it if someone could tell me that it’s not possible, and why. Just for my own further education.

  • Andrew March 11, 2011, 19:27


    The point of antimatter is the energy density, i.e. storing a vast quantity of usable energy in a small space, which makes it excellent for starship propulsion because the mass of the fuel is minimal compared to the vehicle. By comparison, fuel constitutes about 80% of the mass of a Space Shuttle at launch, so most of the effort is spent lifting the fuel itself.

    Producing the antimatter is where the issue lies. As with most things, the factory is vast compared to the product and so you can’t carry it with you.

    Think of a car powered by petrol or batteries. The fuel stores the energy which was harnessed at the refinery or the power station. Creating the fuel ‘on demand’ requires an industrial plant to be carried in the car!

  • Eniac March 11, 2011, 19:40

    The only way to utilize “the Full mc2”, a ship would have to be half matter, half antimatter. The easiest way to do this would probably be to have a solid hunk of antimatter, with normal-matter harness around it that is held in place by magnetic forces. Put a strong magnetic nozzle at one side, and shoot a beam of normal matter at the antimatter near the center of the nozzle.

    Anti-hydrogen is very unsuitable for this, as it is hard to keep solid. The radiation equilibrium temperature even in deep interstellar space is well above its freezing point. Anti-anything-else is likely orders of magnitude more difficult to synthesize. The nozzle and harness would be subject to corrosion by loose anti-matter, especially near the nozzle. Many other problems, of course.

    However, it is important to realize that anything less than a solid chunk and a substantial fraction of the ship’s mass won’t do. If the ratio of antimatter to matter is less than 1%, we might as well use regular nuclear energy, which is much easier to engineer. Plus, Uranium, Plutonium, Thorium or Lithium hydride are easier to get in the required amounts.

  • WLM March 12, 2011, 3:43

    Antimatter for interstellar propulsion is like terraforming: the proverbial big idea and doing things in a *big* way, that turns to be hopelessly impractical, and will probably never be. Yet people still dwell on it.

    It is too intrinsically dangerous, too unstable, to be of any use. Give it up.

  • Ryan March 12, 2011, 13:10

    I just don’t see a solution to the problem of smacking an interstellar dust grain at relativistic velocity and preventing enough fragments – maybe one gets through out of every 100 flights, or whatever kind of odds you like to play Russian Roulette with – from reaching the containment system without a shield thickness of Ludicrous Mass. If an unintended microgram reaction produces as much raw energy output as a small hand grenade, what prevents a secondary spray of evaporating anti-H from making it’s way to the container walls and finishing the job?

  • James M Essig March 12, 2011, 16:16

    Hi Folks;

    One might be able to construct puck combinations of two flavored matter and anti-matter quarkonium cores and encasements. The inside of one puck would be made of antimatter while its protective cladding would be made of antimatter of another species of quark, while the other puck would be composed of matter versions of the quarks in an inverse flavorwise relation.

    Alternatively, the inside of the first puck could be made of antimatter two flavor quarkonium while the outside of the puck would be made of two flavored normal quarkonium where the composition is of two different flavors. The reactive puck would contain the same flavored quarkoniums but in an inverse relationship and also of an inverse charge-parity-conjugate form.

    One might be able to construct puck combinations of three flavored matter and anti-matter quarkonium cores and encasements. The inside of one puck would be made of three flavored antimatter quarkonium while its protective cladding would be made of antimatter of another two other flavored species of quark, while the other puck would be composed of matter versions of the quarks in an inverse flavorwise relation.

    Alternatively, the interior of the first puck could be made of an antimatter three flavor quarkonium while the outside of the puck would be made of two flavored normal quarkonium where the composition is of two different and non-reactive flavors with respect to the interior. The reactive puck would contain the same flavored quarkoniums but in an inverse relationship and also of an inverse charge-parity-conjugate form.

    The relative mass of the cladding and cores for each puck would be somewhat arbitrary however for cases where complete matter antimatter annihilation was desired, the only requirement would be that the total combined quarkonium stored upon the ship would be half matter and half reactive antimatter.

    Two or more flavors would be required for the each of the core and claddings so as to enable electrically neutral compositions.

    I have produced numerous tables showing combinations that would work provided some really big caveats are met.

    The really big caveats are: 1) actually being able to produce bulk quantities of the quarkonium materials; 2) producing such quarkoniums that are stable from decay; and 3) actually being able to open the pucks in a gradual, safe, but timely matter.

    However, since I am counting on our civilization being perpetual, I think the above conditions may yet be achievable.

  • stephen March 12, 2011, 16:31

    Does this make it any easier?


    SEATTLE – Powerful thunderstorms on Earth can fling beams of antimatter into space, a new study finds.

    Scientists picked up on the never-before-seen phenomenon by peering at thunderstorms with NASA’s Fermi Gamma-ray Space Telescope. The antimatter particles were likely created by what scientists call a terrestrial gamma-ray flash (TGF), a brief burst of gamma rays produced inside thunderstorms and known to be associated with lightning, researchers said.

    “These signals are the first direct evidence that thunderstorms make antimatter particle beams,” study lead author Michael Briggs, of the University of Alabama in Huntsville, said in a statement. Briggs presented his team’s results here today (Jan. 10) at the 217th meeting of the American Astronomical Society in Seattle.

    “I think this is one of the most exciting discoveries in geoscience in a very long time,” Duke University’s Steven Cummer, who was not involved in the research, in a press conference. It “seems like something straight out of science fiction.”

  • andy March 12, 2011, 17:15

    Stephen, the problem is that the thunderstorm-generated antimatter appears to be mainly positrons (which are relatively easy to make as these things go). What you really want is something that’s producing antiprotons, or even better actual antihydrogen.

  • Tobias Holbrook March 12, 2011, 19:38

    “The only way to utilize “the Full mc2″, a ship would have to be half matter, half antimatter. ”
    Not exactly… one can collect the matter portion (protons) on the fly, since at such energies the potential thrust from the ramjet should be much greater than any drag. This could allow an effective Isp of c, I would imagine?

  • forrest noble March 13, 2011, 20:35

    We had a great run (discussion) here a couple years back on a Positron Propulsion Systems. It seems by this article that ideas will continue on the anti-matter front probably resulting in an efficient containment system. I have high expectations that within at most a few decades that the problem will be solved concerning positron containment.

    Anti-proton containment, on the other hand I think, is a more formidable quest but am glad to see designs for anti-proton containment like the one above. being continually put forward. Hopefully someday such a Star- Trek-like anti-matter propulsion system will be realized.

  • Procyan March 13, 2011, 21:33

    I remember a story, probably apocrophal, that Alexander Graham Bell was informed by a Royal Society engineer that he had “as much chance of getting that thing to work as a man flying to the Moon.” An interesting parlour trick. What do you propose? Shall we string wires everywhere?

    Eniac, it would seem that you’ve left a bit of wiggle room between “The only way to utilize “the Full mc2″, a ship would have to be half matter, half antimatter.” and “If the ratio of antimatter to matter is less than 1%, we might as well use regular nuclear energy, which is much easier to engineer.”

    Where would 10 percent take us?

    If anti-matter is the best way to go, then let the anihilation begin.

  • Eniac March 14, 2011, 0:23

    Tobias: Technically, by picking up matter on the way you are going beyond the “Full mc2”. I am not sure there would be sufficient matter there to be worth the trouble, but it is definitely an idea to consider.

    An Isp of c can easily be reached without antimatter, any flashlight is an example of a photon rocket with ISP of c, albeit with a very low thrust/mass ratio.

  • Eniac March 20, 2011, 1:09


    Where would 10 percent take us?

    10 percent would be pretty good, but 50%, 10%, or 1% are all the same in that they require a solid chunk. It is a completely different domain from the “traps” currently used, unbridgeably different, I think.

  • Astronist March 22, 2011, 19:18

    @Eniac: “If the ratio of antimatter to matter is less than 1%, we might as well use regular nuclear energy, which is much easier to engineer.”

    But do we actually know that fusion is easier to engineer? Its advantage is clearly that the fuel is relatively easy to manufacture and store. Its disadvantage is that the fuel is very hard to burn in a controlled manner, while the antimatter-matter reaction occurs spontaneously. Do we really know enough yet to say where the balance of advantage between these two technologies lies?

    Oxford, UK

  • ljk April 25, 2011, 1:32

    It’s official: Heaviest antimatter found

    STAR Collaboration / RHIC / BNL

    This image shows a three-dimensional rendering of the STAR time projection chamber surrounded by the time-of-flight barrel (the outermost cylinder).
    Particle tracks spray out from the collision, including a meter-long track from an antihelium-4 nucleus (highlighted in bold red).

    The reports began circulating a few weeks ago, and today’s publication in the journal Nature makes it official: Physicists have detected the heaviest bits of antimatter ever found on Earth. And that record is likely to stand for a long, long time.

    Full article here:


  • ljk May 4, 2011, 0:04

    Antihydrogen Trapped For 1000 Seconds

    The long term storage of significant amounts of antihydrogen should soon settle the question of whether antimatter falls up or down

    kfc 05/02/2011

    Antihydrogen is rare in our part of the Universe. Indeed, it was only last year that scientists at CERN’s Antihydrogen Laser Physics Apparatus (ALPHA) managed to trap a significant amount of the stuff for the first time, albeit only 38 antiatoms for just 172 milliseconds.

    Today, they announce a significant improvement. These guys now say they’ve trapped 309 antihydrogen atoms for up to 1000 seconds. That’s an increase in trapping time of four orders of magnitude, comparable to what’s possible with good old ordinary matter.

    The news is significant because it makes possible a new set of experiments that should answer some important questions.

    Most important of these is whether ordinary gravity attracts or repels antimatter. In other words, does antihydrogen fall up or down?

    Although there have been many attempts to do this experiment, all have been inconclusive because nobody has been able to trap a good lump of antimatter for long enough to try.

    All that should soon change. The ALPHA team now plans to cool a small lump of antihydrogen and then watch it as it falls (or rises). Which means physicists should have their answer within months.

    Ref: http://arxiv.org/abs/1104.4982: Confinement Of Antihydrogen For 1000 Seconds

  • J Cuttance May 17, 2011, 1:29

    if we’re going down the periodic table, why not use anti-lithium’s likely paramagnetic properties?

  • ljk July 21, 2011, 0:51

    New and Improved Antimatter Spaceship for Mars Missions


    Most self-respecting starships in science fiction stories use antimatter as fuel for a good reason – it’s the most potent fuel known. While tons of chemical fuel are needed to propel a human mission to Mars, just tens of milligrams of antimatter will do (a milligram is about one-thousandth the weight of a piece of the original M&M candy).

    Image right: A spacecraft powered by a positron reactor would resemble this artist’s concept of the Mars Reference Mission spacecraft. Credit: NASA

    However, in reality this power comes with a price. Some antimatter reactions produce blasts of high energy gamma rays. Gamma rays are like X-rays on steroids. They penetrate matter and break apart molecules in cells, so they are not healthy to be around. High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material.

    The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter-powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy.