baudrunner's space: Antimatter - dream or possibility?
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Monday, January 21, 2008

Antimatter - dream or possibility?

The current production of antimatter is entirely experimental in scope, and is accomplished only for the purpose of scientific investigation and to support or assist in refining particle theory. If antimatter production were commercially viable then we would have the answer to all of our energy concerns because one gram of antimatter could drive one hundred thousand cars for about a year. But it is not commercially viable at the present time. All the antimatter production done at CERN over the last ten years amounts to about a billionth of a gram in a program that has cost a few hundred million euros. That would make that one gram of antimatter cost about seven hundred million billion dollars, or $700,000,000,000,000,000.00 at today's prices. That doesn't make the price of gasoline seem so outrageous now, come to think of it.

A "self-contained antiproton factory", the Antiproton Decelerator (or AD), is operational at CERN. It is designed to produce, collect, cool, decelerate and eventually extract antiprotons.

Targets, usually copper or iridium, are bombarded with a high energy stream of protons. This releases a huge amount of energy compacted in a small space in which matter-antimatter particles are spontaneously created. Antiproton-proton pairs are formed in about one in a million collisions, but with about 10 trillion protons hitting the target every minute a good 10 million antiprotons are directed into the AD at a time. Through a process of magnetic confinement and super cooling the antiproton package is coerced into a tight bunch travelling at about 10% of light speed.

The current state of the art in antiproton experimentation is in the creation of antihydrogen, which consists of combining antiprotons with positrons from a radioactive source, and in creating other exotic atoms by replacing the electrons of atoms with antiprotons.

I see the researchers at CERN moving forward in leaps and bounds in advancing the science of antimatter production. Perhaps some day we will be driving cars powered by this exotic fuel source, who knows?

Before that happens, we would certainly be powering our spacecraft with antimatter. With the highest energy density of any material currently found on earth, a mere 100 milligrams of the stuff provides the propulsive energy of the space shuttle. A process called antiproton catalyzed microfission (ACMF) developed at Penn state University allows 100% of the energy from a fission reaction to be used for propulsion. A team there has already developed a spacecraft utilizing this technology which would require the nominal amount of 140 nanograms of antimatter to send a manned spacecraft to Mars in about thirty days. Even more advanced spacecraft have been envisioned in which antimatter and fissionable material are used to spark a microfusion reaction. Requiring somewhat more antimatter than the ACMF engine but less fissionable material, the effective specific impulse, a measure of rocket or jet engine efficiency, is increased by a factor of two over ACMF.

The chief obstacle to actually building and using these engines is in the storage and transportation of antimatter. Thus far, the Antimatter Group at Penn State have constructed and proved a portable antimatter storage (Penning) trap which can store 100 billion antiprotons for one week. NASA has taken an interest in this project and is using the Penn State results to develop a Penning trap that can store ten trillion antiprotons, enough to potentially support hundreds of reactions over a two minute time-frame. A good explanation of the technologies I have described can be found at The Encyclopedia of Astrobiology Astronomy and Spaceflight.

The first practical application of antimatter that will be realized is in the field of medicine. NASA is developing its Penning trap with the idea of harnessing the antiproton for radiotherapy of tumors. Additionally, a by-product of the Penning trap is the generation of the Oxygen isotope O-15, which is used in Positron Emission Tomography of the human brain. Only a few research hospitals around the world have the ability to create O-15, and the Penning trap would make possible the delivery of this valuable element to any hospital.

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