Maxwell’s Atomic Coilgun: The Quest for Absolute Zero

Scientific American’s March 2011 article entitled “Demons, Entropy, and the Quest for Absolute Zero” by Mark G. Raizen reveals just how low of temperatures can now be reached with Maxwell’s Atomic Coilgun and what implications this has in modern science. The second law of thermodynamics deals with entropy, and how natural processes always go toward lower order; entropy is disorder. Maxwell and his atomic coilgun aim to turn that law on its head to realize an idea from the nineteenth century. This idea involved “Maxwell’s demon and appeared to violate the second law of thermodynamics because it could lower the entropy of the gas while expending a negligible amount of energy” (58). A man named Szilard talked Maxwell’s demon out of this paradox in a very complex manner. Just know that it did not violate the second law of thermodynamics.

The way modern scientists go about getting gas atoms and some gas molecules to such low temperatures starts with using a vacuum. They launch this gas into a vacuum at super-high speeds, making temperature decrease drastically. This gets the gas’s temperature to around 1/100 a degree above (barely) absolute zero. Next, these scientists use magnetic brakes called an atomic coilgun to reduce the speed of these atoms/molecules. These atomic coilguns were originally designed to do the opposite, accelerating particles and large projectiles using the same magnetic field. This technology is applied in reverse to slow the particles this time. Most elements have north and south magnetic poles, and all elements that do can be controlled by these atomic coilguns.

That was stage one of cooling; here is step two. At this point, an atomic coilgun would have cooled down atoms/molecules to 1/100 of a degree above absolute zero. Some might say that this is close, but no cigar. Wiser men would realize that this new achievement in science will allow us to discover much about matter that is currently unknown, and possibly not just about matter’s properties, but maybe about antimatter and its properties. This list could go on and on; nobody knows. Anyhow, at stage two of cooling, the temperature is brought down to one-millionth of a degree above absolute zero, or even lower! Here, scientists use a technique called single-photon cooling, which “appears to violate the second law of thermodynamics” (59). This method uses a one-way gate once proposed by Maxwell in 1871 in a thought experiment. This gate compresses atoms down to a smaller volume, all the while without raising their temperature! The gate follows by letting the atoms expand to the initial volume. This, however, lowers their temperature.

This has opened many doors in research. One is to study chemical reactions at a quantum level. Another possibility of utility of this research would be to work to lift the barriers of the current ultrahigh-precision spectroscopy and make it even more precise. Two more would be to measure the mass of a neutrino, and maybe even that of an antineutrino. This applies for antihydrogen as well, which will tell us more about antimatter and its reactions to gravity. One more is to aid in the separation of isotopes. Yet another is to help us better understand how atoms look down to the nanometer. This list may go on forever.

Posted by Derek Melzar (2).