Pyroelectric fusion
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Pyroelectric fusion refers to the technique of using pyroelectric crystals to generate high strength electrostatic fields to accelerate deuterium ions (tritium might also be used someday) into a metal hydride target also containing deuterium (or tritium) with sufficient kinetic energy to cause these ions to undergo nuclear fusion. The process of light ion acceleration using electrostatic fields and deuterium ions to produce fusion in solid deuterated targets was first demonstrated by Cockcroft and Walton in 1932 (see Cockroft-Walton generator). Indeed, the process is used today in thousands of minaturized versions of their original accelerator, in the form of small sealed tube neutron generators, in the petroleum exploration industry.
The novel idea with the pyroelectric approach to fusion is in its application of the pyroelectric effect to generate the accelerating fields. This is done by heating the crystal from −30°C to +45°C over a period of a few minutes.
A UCLA team, headed by Brian Naranjo, conducted an experiment demonstrating the use of a pyroelectric power source for producing fusion on a laboratory bench top device in April 2005. The device used a lithium tantalate (LiTaO3) pyroelectric crystal to ionize deuterium atoms and accelerate the ions towards a stationary erbium dideuteride (ErD2) target. Around 1000 fusion reactions per second took place, each resulting in the production of an 820 keV helium-3 nucleus and a 2.45 MeV neutron. The team anticipated applications of the device as a neutron generator, or in microthrusters for space propulsion.
A team at Rensselaer Polytechnic Institute, led by Dr. Danon and his graduate student Jeffrey Geuther, has confirmed and improved upon these experiments using a device using two pyroelectric crystals and capable of operating at non-cryogenic temperatures.
Nuclear D-D fusion driven by pyroelectric crystals was proposed by Naranjo and Putterman in 2002. It was also discussed by Brownridge and Shafroth in 2004. The possibility of using pyroelectric crystals in a neutron production device (by D-D fusion) was first proposed in a conference paper by Geuther and Danon in 2004 and later in a publication discussing electron and ion acceleration by pyroelectric crystals. The key ingredient of using a tungsten needle to produce sufficient ion beam current for use with a pyroelectric crystal power supply was first proposed and demonstrated in the 2005 Nature paper although in a broader context tungsten emitter tips have been used as ion sources in other applications for many years.
This development is not related to earlier claims of fusion having been observed during sonoluminescence (bubble fusion). In fact, the leader of the team behind this development was one of the main critics of these earlier prospective fusion claims.
[edit] Sources
- B. Naranjo, J.K. Gimzewski and S. Putterman "Observation of nuclear fusion driven by a pyroelectric crystal". Nature, April 28, 2005
- B. Naranjo and S. Putterman "Search for fusion from energy focusing phenomena in ferroelectric crystals". UCEI Proposal, February 1, 2002
- James D. Brownridge and Stephen M. Shafroth, [1], 1 May 2004
- Jeffrey A. Geuther, Yaron Danon, “Pyroelectric Electron Acceleration: Improvements and Future Applications”, ANS Winter Meeting Washington, D.C, November 14 – 18, 2004.
- Jeffrey A. Geuther, Yaron Danon “Electron and Positive Ion Acceleration with Pyroelectric Crystals”, Journal of Applied Physics 97, 074109 (April 1 2005).
- Matin Durrani and Peter Rodgers "Fusion seen in table-top experiment". Physics Web, April 27, 2005
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