Pyroelectric fusion
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Pyroelectric fusion is a technique for achieving nuclear fusion by using an electric field generated by pyroelectric crystals to accelerate ions of deuterium (tritium might also be used someday) into a metal hydride target also containing detuerium (or tritium) with sufficient kinetic energy to cause these ions to fuse together. The novel idea at work with this approach to fusion is in its application of the pyroelectric effect to generate a strong electric field (gigavolts per meter), by heating the crystal from −30°C to +45°C in a few minutes. The strong field is used to accelerate deuterium ions from a needle-thin tungsten probe tip mounted on a copper disk into a solid target containing deuterium. Some of the deuterium atoms fuse, producing helium and neutrons. Like muon-catalyzed fusion, the process does not appear to be able to generate net power, but may have other uses.
A UCLA team, headed by Brian Naranjo, has observed the nuclear fusion of deuterium nuclei in a laboratory bench top device in April 2005. The device uses a lithium tantalate () pyroelectric crystal to ionize deuterium atoms and accelerate the ions towards a stationary erbium dideuteride (D2) target. Around 1000 fusion reactions per second took place, each resulting in the production of an 820 keV helium-3 nuclei 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 Jeffrey Geuther, has confirmed and improved upon these findings, with 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 neutron production (by D-D fusion) was first proposed in a conference paper by Geuther and Danon in 2004 and later in a publications 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 maany 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.
Sources
- B. Naranjo, J.K. Gimzewski and S. Putterman ["Observation of nuclear fusion driven by a pyroelectric crystal"]. [[w:Nature (journal)|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, [link], 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"]. [[w:Physics Web|Physics Web]], April 27, 2005
External links
See also
Neutron sources
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