Cold Fusion

Nuclear Energy

Most chemical reactions (e.g. burning of gasoline) give out ~ 100 MJ/kg. At the atomic level, this implies about 10 electron-volts/atom.

[Electron volt is a unit of energy: an electron in a TV tube has an energy of ~ 30 KeV, an atom in a gas has an energy of about 1/40 eV]

C + O₂ -> CO₂ + ~ 5 eV

Nuclear reactions give out millions of eV/nucleus

E.g.

Problem: there is a very large repulsive force between nuclei, until distances become very small (~ 10-15 m or 1 femtometre, 1 fm). Fusion won’t happen until we can get over the barrier

Ways out:

a) Stars: use lots of pressure -> high temp (15*10⁶ ºC)

Average energy of protons ~ 100 KeV, so some will fuse.

b) Hydrogen bomb: heat small amount of gas up to ~10⁹ °C for a very short time, by imploding layer.

c) Magnetic bottle or Tokomak: confines very hot gas with magnetic fields, for long enough.

d) Laser implosion: essentially b) with lasers used to replace explosive.

e) Due to an obscure process known as "quantum-mechanical tunneling", we do not need to actually exceed the barrier height. Can calculate that a D₂ molecule would spontaneously turn into He with a rate of 1 in 10⁷⁹ s^-1. (i.e. about 1 in the visible universe!)

Cold Fusion

"Discovered" in March 1989 by Stanley Pons and Martin Fleischmann: confirmed by Steve Jones et al shortly afterwards

Electrolysis separates water into oxygen and hydrogen

Palladium electrodes absorb deuterium for several days.

When electric current is stopped, electrodes continue to release heat: up to 100 W. Helium is found in residual gas. Only possible interpretation is

D + D --> ⁴He + energy.

What is the exact reaction?

Is not allowed in free space: instead we should get

So should see tritium: can be detected in residual gases So should see neutrons: can detect these with n detector

Why does it work?

All sorts of reasons.

a) Obviously what the Pd lattice does is to compress the deuterons together to allow the process to run much faster rate ~ 10^-9 s^-1

Pressure in Pd can be calculated at 10²⁶ atmospheres (Centre of sun is 10⁹ atmos)

b) Electron screening:

c) Many body effects (sometimes 10⁶ electrons do not behave like 10⁶ times one electron: e.g. in superconductors)

SO "It is no longer possible to lightly dismiss the reality of cold fusion" Julian Schwinger (Nobel laureate)

Why is the scientific establishment suppressing the most exciting scientific discoveries of the 20^th century? Could it be that it is being done by the oil companies?!?!?!?!?

The reality seems to be

1. Not nearly enough neutrons are seen (if any!)
2. Tritium shows up as a contaminant almost everywhere (and the quantities are tiny)
3. The energy released (if it is real) is probably just caused by distortion of the lattice of atoms

and finally: is this a success or failure of the scientific method?

A resounding success. a very provocative and exciting idea caused hundreds of people (including myself!) to drop everything to investigate it. The cumulative work showed that there is NO appreciable effect: it probably cost M$10 to show this.