• Free this month
• Hearing music in ensembles
• Obama, Detroit push the limits of electric vehicle batteries
• The cytoskeleton: I-beams of the cell
• Obituaries
• New books
• New products
• Letters

• Most popular articles
• Gedanken experiment: Levitate a physics sitcom?
  Points of View
• Nanoplasmonics: The physics behind the applications
  February 2011
• Half-quantum vortices
  Physics Update
• Quantum criticality
  February 2011

Muons, deuterium, and cold fusion

It would be in the national interest for all those involved in the cold-fusion
 controversy to read a 1957 paper by Luis Alvarez and his coworkers. During the
 1950s Alvarez, of the University of California, Berkeley, invented a new kind
 of particle detector. Called a hydrogen bubble chamber, it was the subject of
 one of the 40 patents he held. It was vastly superior to other detectors then
 available, and it permitted experiments that would not otherwise have been
 possible.

Using his detector, in 1957 Alvarez observed the capture of μ⁻ mesons by deuterium molecules, immediately followed by the nuclear fusion of the
 two deuterium atoms. He reported his discovery in one of the 168 scientific
 publications he wrote; he described the process as the chemical catalysis of
 nuclear fusion.¹ The force holding two atoms together in a diatomic molecule is linear in the
 mass of the electron. Substituting a μ⁻ meson for an electron effectively increased that force more than 200 times,
 allowing the fusion to occur.

Although Alvarez used cyclotron-produced μ⁻ mesons, Earth is continually bathed in cosmic rays that produce μ mesons and other particles. By showing that a μ⁻ meson will induce fusion of two deuterons if it is captured in their electric
 field, Alvarez proved that a molecule of deuterium exposed to the terrestrial
 cosmic-ray background has a small but finite probability of undergoing fusion.

In 1989 Martin Fleischmann and Stanley Pons also discovered the fusion of
 deuterium without the use of great heat and called a press conference to
 announce their “cold fusion” results. The media was quick to pounce on the promise of nearly unlimited power
 from such small equipment, but the scientific community was much more
 skeptical. The fusion of two deuterons requires hundreds of thousands of eV,
 whereas Pons and Fleischmann’s experiment involved only a few volts, a fact that rendered their explanation
 of the effect impossible. Still, since 1989 the Pons–Fleischmann experiment has been repeated over and over, ² often with the result that rather more energy is released than can be explained
 by the equipment used. The 24 April 2009 segment of the CBS TV show 60 Minutes rehashed those experiments and again mentioned the potential for nuclear-powered
 vehicles and other wonderful applications.

It takes hundreds of MeV to make a meson, which has a half-life of only microseconds and produces at most only a
 few tens of MeV of energy during the fusion reaction. Had any viable
 energy-producing application come out of the effect he discovered, Alvarez
 would have patented it. If those involved in the cold-fusion controversy read
 Alvarez’s paper, they will recognize that deuterium does undergo fusion if exposed to
 cosmic-ray secondaries. Can the cold-fusion results be explained merely in
 terms of fusion induced by naturally occurring cosmic-ray muons, or is
 something else going on in those experiments?

References

1. 1. L. Alvarez, Phys. Rev. 105, 1127 (1957) [SPIN].
2. 2. See, for example, the review by G. K. Hubler, Surf. Coat. Technol. 201, 8568 (2007) [INSPEC].