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?
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!
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.
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!