How cold is cold fusion?

1. How cold is cold fusion? Janne Wallenius Associate professor Department of Reactor Physics Royal Institute of Technology

2. Outline • Press conference science • Cold nuclear fusion in condensed matter • What about fusion neutrons? • Helium, anyone? • How not to use a thermometer. • Cold fusion that works: Muon Catalysed Fusion

3. Press conference science • On March 23rd 1989, Fleischmann & Pons from University of Utah announce at a press conference the discovery of “controlled nuclear fusion during electrolysis of heavy water using palladium electrodes”. • Competing bid from Jones et al at Brigham Young University published in Nature a few weeks later. • Production of excess heat soon “confirmed” in various laboratories over the world. • Massive attention from media

4. Media wave • Swedish engineering student journal among first to publish the news! • “The eternal solution to the energy problems of the world does not appear implausible.”

5. Cold Nuclear Fusion in Condensed Matter • Palladium absorbs large amounts of hydrogen. • F&P: Electrolysis of D2O using palladium electrodes would lead to D2 formation in the crystal lattice of the metal. • The heat of formation was measured using “calorimetry”. • Heating rate of heavy water exceeding expectations by more than 10 W ! • Observation of gamma rays from neutron capture in surrounding water. • F&P interpret data as a result of D2 fusion!

6. What about the fusion neutrons? Possible fusion reactions: d + d –> t + n + 4.0 MeV d + d -> 3He + p + 3.3 MeV • How many fusion reactions are necessary to obtain 10 W of excess heating? • More than 1013 /s • Measured neutron yield ~104/s • Why would solid state fusion affect fusion branching ratios? • Where does the heat come from? • F&P warn for performing the experiment with too large electrodes!

7. Helium, anyone? Suggested solution: d + d -> 4He + gamma + 24 MeV • Known to be 8 orders of magnitude less probable than the major reaction paths. • Helium production claimed to be measured by several groups. • When carefully checked, air leakage identified as probable source of helium.

8. How not to use a thermometer • A series of refined experiments by Jones et al at BYU excludes production of neither neutrons nor tritium. • The erratic observations of excess heat shown to be a result of poor calorimetric techniques. • F&P move to France and start a private company funded by Toyota. • Having spent 30 M$, Pons gives up and stops talking to media. • Fleischmann returns to UK and continues to work on Cold Fusion theory. • Cold Fusion: Religion or Truth?

9. Muon catalysed fusion • Muons are electron like elementary particles • Muon mass: 200 x electron mass • Muon life time: 2.2 microseconds • Exercise: estimate the radius of a hydrogen atom where the electron is substituted with a muon! • 200 times smaller! • In a muonic hydrogen molecule, the nuclei would be 200 times closer to each other. • Exercise : estimate the increase in fusion probability, comparing to “electronic” hydrogen molecules.

10. Historical perspective • In 1947, F.C. Frank suggested in a Nature paper that if muonic hydrogen molecules form, they would undergo fusion according to • pμ + d -> pdμ -> 3He + μ + γ + 5.5 MeV • In 1948, A. Sakharov proposed that the fusion rate would be higher in mixtures of deuterium and tritium, where the following reactions occur • dμ + d -> ddμ -> 3He + μ + γ + 3.3 MeV • dμ + d -> ddμ -> t + p + μ + 4.0 MeV • tμ + d -> tdμ -> 4He + n + μ + 17.6 MeV

11. Experimental confirmation • 1957: Alvarez and Teller observes pdμ fusion • 1966: Dzhelepov measures strong temperature dependence of ddμ fusion rates - resonant process must be behind. • 1967: Vesman proposes resonant muonic molecule formation mechanism. 10 fusions per muon possible in D2. • 1977: Ponomarev predicts 100 fusions per muon in DT-mixtures. • 1983: Jones et al measures 150 fusions per muon in liquid DT. • Jones coins the term cold fusion, and then starts to work on more bizarre projects.

12. Muon recycling • In liquid hydrogen the time for formation of muonic hydrogen molecules is < 10-8 s • Potential for > 200 fusions per muon . • Probability for muon sticking on helium fusion product: 0.5% • Upper limit: 200 fusion per muon. • Experimentally: 100-150 fusions per muon observed.

13. How cold is muon catalysed fusion? • Fusion neutrons readily produced at room temperature! • Energy released by 200 DT fusions: ~ 3.6 GeV • Cost for producing a muon by proton bombardment of lithium or carbon: 10 GeV. • No prospects for commercial utilisation. • Potential use as 14 MeV line neutron source for material testing. • Coldest fusion ever: Experiments have been made in solid hydrogen at T = 3K!