How cold is cold fusion?

Janne Wallenius

Associate professor

Department of Reactor Physics

Royal Institute of Technology

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

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

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.”

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!

What about the fusion neutrons?

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!

Possible fusion reactions:

d + d –> t + n + 4.0 MeV

d + d -> 3He + p + 3.3 MeV

Helium, anyone?

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.

Suggested solution:

d + d -> 4He + gamma + 24 MeV

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?

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.

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

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.

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.

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!