Antimatter Source Near the Earth

by Paul Gilster on August 10, 2011

Now that NASA’s Institute for Advanced Concepts (NIAC) is back in business, I’m reminded that it was through NIAC studies that both Gerald Jackson and James Bickford introduced the possibility of harvesting antimatter rather than producing it in huge particle accelerators. The idea resonates at a time when the worldwide output of antimatter is measured in nanograms per year, and the overall cost pegged at something like $100 trillion per gram. Find natural antimatter sources in space and you can think about collecting the ten micrograms that might power a 100-ton payload for a one-year round trip mission to Jupiter. Contrast that with Juno’s pace!

That assumes, of course, that we can gather enough antimatter to test the concept and develop propulsion systems — doubtless hybrids at first — that begin to draw on antimatter’s power. Bickford (Draper Laboratory, Cambridge MA) became interested in near-Earth antimatter when he realized that the bombardment of the upper atmosphere of the Earth by high-energy galactic cosmic rays should result in ‘pair production,’ creating an elementary particle and its antiparticle.

A planetary magnetic field can hold such particles in place, producing a localized source of antiprotons. The detection of antimatter in this configuration has now been confirmed by a team of researchers using data from the Pamela satellite (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics). In fact, Pamela picks up thousands of times more antiprotons in a region called the South Atlantic Anomaly than would be expected from normal particle decays.

Image: A cross-sectional view of the Van Allen radiation belts, noting the point where the South Atlantic Anomaly occurs. Credit: Wikimedia Commons.

We could go so far as to talk about an ‘antimatter belt’ around the Earth, as the paper on this work explains:

Antiprotons are… created in pair production processes in reactions of energetic CRs [cosmic rays] with Earth’s exosphere. Some of the antiparticles produced in the innermost region of the magnetosphere are captured by the geomagnetic field allowing the formation of an antiproton radiation belt around the Earth. The particles accumulate until they are removed due to annihilation or ionization losses. The trapped particles are characterized by a narrow pitch angle distribution centered around 90 deg and drift along geomagnetic field lines belonging to the same McIlwain L-shell where they were produced. Due to magnetospheric transport processes, the antiproton population is expected to be distributed over a wide range of radial distances.

The McIlwain L-shell referred to above describes the magnetic field lines under investigation. As to the South Atlantic Anomaly, it is here that the inner Van Allen radiation belt approaches the Earth’s surface most closely, which creates a higher degree of flux of energetic particles in the region. It turns out to be quite a lively place, as this Wikipedia article on the matter makes clear:

The South Atlantic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation, caused by the trapped protons in the inner Van Allen belt, each time. The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Space Telescope does not take observations while passing through the SAA. Astronauts are also affected by this region which is said to be the cause of peculiar ‘shooting stars’ (phosphenes) seen in the visual field of astronauts. Passing through the South Atlantic Anomaly is thought to be the reason for the early failures of the Globalstar network’s satellites.

What we’re seeing in the new work is that the Van Allen belt is indeed confining antiparticles in ways that the earlier NIAC work suggested. The antiprotons eventually encounter normal matter in the Earth’s atmosphere and are annihilated, but new antiparticles continue to be produced. The question is whether there may be enough antimatter here for hybrid missions like Steven Howe’s antimatter sail, which uses tiny amounts of antimatter to induce fission in a uranium-infused sail. James Bickford, in his Phase II study at NIAC, talked about a collection scheme that could collect 25 nanograms per day, using a plasma magnet to create a magnetic scoop that could be deployed in an equatorial Earth orbit, one that would trap incoming antiprotons.

Antimatter trapped in Earth’s inner radiation belt offers us useful savings, if Bickford is right in thinking that space harvesting will prove five orders of magnitude more cost effective than antimatter creation here on Earth. I also noticed an interesting comment in his Phase II NIAC report: “Future enhanced systems would be able to collect from the GCR [galactic cosmic ray] flux en route to further supplement the fuel supply.” Obviously, exploiting antimatter trapped near the Earth and other Solar System worlds assumes a robust space-based infrastructure, but it may be one that will finally be able to bring antimatter propulsion into a new era of experimentation.

James Bickford’s Phase II report is titled “Extraction of Antiparticles Concentrated in Planetary Magnetic Fields” (online at the NIAC site). Back in 2007 I looked at this work in three connected posts, which may be useful in putting all this in context:

The Pamela work is found in Adriani et al., “The discovery of geomagnetically trapped cosmic ray antiprotons,” Astrophysical Journal Letters Vol. 37, No. 2, L29 (abstract / preprint). See also Gusev et al., “Antiparticle content in the magnetosphere,” Advances in Space Research, Volume 42, Issue 9, p. 1550-1555 (2008). Abstract available.

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{ 7 comments }

Alex Tolley August 10, 2011 at 11:18

Looking at Bickford’s NIAC PII paper, he states that the total anti-proton mass trapped in the earth’s magnetic fields is just 160ng, with a 2ng/yr fill rate. This seems insufficient for Howe’s Kuiper Belt sail (~ 30mg needed :- 5-6 orders of magnitude > earth reserve) and suggests that once the earth’s supply is tapped, it would take 80 years to replenish. This doesn’t seem a very good source to me. Saturn, OTOH, with 240 microgm/yr production seems more plausible, if the production can be trapped.

Bickford states that 1 kg/s of anti-protons enter the solar system. This would be a vast source if even a small amount could be tapped. While I appreciate that magnetic fields are best means to collect this matter, I wonder if it is possible that gravitational lensing might also be useful to concentrate the material. Could this work, or would the solar magnetic fields disrupt any such focusing?

JohnQ August 10, 2011 at 13:01

Maybe I’m missing something here, but Robert Forward made it very clear in his newsletter devoted to anti-matter that the reason costs of Anti-M are so high is simply because the stuff currently is a by product of scientific processes, not industrial. He fully expected that if the production of anti-matter were undertaken by industry (that’s right, capitalism and all the associated yucky stuff that goes with it), then the costs would significantly drop. Now, admittedly a cost study of how to do this, considering the available alternatives, has probably not been done. But as we move into the realm of economics more than in science (and yes, the bridge between them, engineering) we should be able to start thinking about many possibilities. If you want to get serious about getting your hands on anti-m (yes, that’s a joke), considerations of cost are paramount, but they are only the beginning. If it’s just going to be a State subsidizied toy, economics still applies of course, but as the hand-maiden of government, has little to say.

Again, I don’t know what the market for anti-matter could be, though I think it could be substantial (as costs decline, what is the break-even point where it becomes profitable to manufacture the stuff?). I don’t know how much investment would be required for any of the options (producing or harvesting or a mix?), what reasonable regulations would be involved (it is easy enough to imagine regulations that would kill versions or all of the Anti-M industry outright), and what additional research would need to be done to make any of the options practical (not the same as feasible!). Storage and distribution, let’s not forget about them.

It’s a huge problem but history says such can be “solved” (i.e. identify the optimal trade-offs). As we come to understand the trade-0ffs better, economically viable decisions can be made.

kurt9 August 10, 2011 at 15:46

He fully expected that if the production of anti-matter were undertaken by industry (that’s right, capitalism and all the associated yucky stuff that goes with it), then the costs would significantly drop.

Forward made this assumption off the top of his head, but gave no detailed ideas on how to do it. I think positrons are used in certain medical imaging and cancer treatments, which means that a commercial market already exists for them (if you can call medical “commercial”). Yet, the production rate has not increased much (nor costs come down).

Perhaps these table-top systems based on SLAC/CPA laser technology may lead to low cost antimatter production. I think this is the key development in high energy physics. This technology allows one to do for, say, $1 million what used to require a $1 billion accelerator.

If not, harvesting from Saturn (and Jupiter) makes sense. Saturn first, since it has the lower escape velocity. Jupiter probably has more of this antimatter than Saturn. I guess both antimatter and He3 will come from the Saturn system.

Dale Jacobs August 12, 2011 at 4:18

Antimatter at Jupiter is trapped in its ‘South Atlantic anomaly’, the Giant Red Spot, and Juno will confirm that? Fusion temperatures at Jupiter? and Saturn too?

Alex Tolley August 12, 2011 at 8:09

Would it be possible to trap antiprotons in C60 (fullerene)? Is the electron density high enough to keep the antiproton from penetrating the electron shells? If one antiproton was trapped per molecule, that would be approximately 1/1000 the mass, so 1 kg of “fuel” would contain a 1gm of antiprotons. I could imagine this fuel would glow as some antiprotons escaped their cages and were annihilated.

Such a fuel would almost instantly solve the launch to orbit constraint, as well as deep space missions.

Bill Higgins-- Beam Jockey August 13, 2011 at 23:50

According to Alex Tolley, Bickford claimed the fill rate for the Earth’s supply of trapped antiprotons was 2 ng/year.

Fermilab’s antiproton source may not have satisfied Bob Forward, God rest his soul, but hard-working engineers and physicists have improved it greatly in the years since Bob visited, and it now easily exceeds two nanograms per year. I think in 2008, when the usual maintenance shutdown period was canceled, over three nanograms were stacked.

So the cosmic harvest of Earth’s trapped antiprotons doesn’t look very attractive, if the number Alex Tolley quoted is correct, compared to the production rate of an underground source which already exists and which cost a few hundred million dollars.

(I agree with Forward that a higher efficiency could be achieved in a hypothetical antiproton factory of new design, as long as designers are willing to spend plenty of money.)

Regrettably, the Antiproton Source will be out of business 48 days from now, when the Tevatron collider shuts down permanently, since the Tevatron is the only customer for its “p-bars.”

In Switzerland, although the Large Hadron Collider does not use antiprotons, being a p-p collider, CERN’s antiproton factory continues to supply beam to various experiments.

ljk March 13, 2012 at 9:25

ALPHA Closes in on Antimatter

by Amy Shira Teitel on March 10, 2012

We live in a universe made of matter. But at the moment of the Big Bang, matter and antimatter existed in equal amounts. That antimatter has all but disappeared suggests that nature, for some reason, has a strong preference for matter. Physicists want to know why matter has replaced its antimatter twin, and this week the ALPHA collaboration at CERN got a step closer to unraveling the mystery.

ALPHA, an international collaborative experiment established in 2005, was designed to trap and measure antihydrogen particles with a specially designed experiment. It’s picking up where its antimatter-searching predecessor, ATHENA, left off. The focus is on antihydrogen because hydrogen is the most prevalent element in the universe and its structure is extremely well known to scientists.

Each hydrogen atom has one electron orbiting its nucleus. Firing light at the atoms excites the electron, causing it to jump into an orbit further away from the nucleus before it relaxes and returns to its resting orbit emitting light in the process. The frequency distribution of this emitted light is known; it has been precisely measured and, in our universe made of matter, is unique to hydrogen.

Full article here:

http://www.universetoday.com/94076/alpha-closes-in-on-antimatter/#

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