Pyroelectric fusion refers to the technique of using
pyroelectric crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
s to generate high strength electrostatic fields to accelerate
deuterium
Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...
ions (
tritium
Tritium () or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.33 years. The tritium nucleus (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the ...
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
Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
. It was reported in April 2005 by a team at
UCLA
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the C ...
. The scientists used a
pyroelectric crystal heated from , combined with a
tungsten
Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...
needle to produce an
electric field
An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
of about 25 gigavolts per meter to ionize and accelerate
deuterium
Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...
nuclei into an
erbium
Erbium is a chemical element; it has Symbol (chemistry), symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare- ...
deuteride target. Though the energy of the deuterium ions generated by the crystal has not been directly measured, the authors used 100 keV (a temperature of about 10
9 K) as an estimate in their modeling. At these energy levels, two deuterium nuclei can fuse to produce a
helium-3
Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron. (In contrast, the most common isotope, helium-4, has two protons and two neutrons.) Helium-3 and hydrogen-1 are the only stable nuclides with ...
nucleus, a 2.45 MeV
neutron
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...
and
bremsstrahlung. Although it makes a useful neutron generator, the apparatus is not intended for power generation since it requires far more energy than it produces.
History
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
Cockcroft–Walton generator
The Cockcroft–Walton (CW) generator, or multiplier, is an electric circuit that generates a high DC voltage from a low-voltage AC. It was named after the British and Irish physicists John Douglas Cockcroft and Ernest Thomas Sinton Walton, ...
). That process is used in miniaturized versions of their original accelerator, in the form of small sealed tube
neutron generator
Neutron generators are neutron source devices which contain compact linear particle accelerators and that produce neutrons by fusing isotopes of hydrogen together. The nuclear fusion, fusion reactions take place in these devices by acceleratin ...
s, for
petroleum exploration.
The process of pyroelectricity has been known from ancient times. The first use of a pyroelectric field to accelerate deuterons was in a 1997 experiment conducted by Drs. V.D. Dougar Jabon, G.V. Fedorovich, and N.V. Samsonenko.
This group was the first to utilize a
lithium tantalate () pyroelectric crystal in fusion experiments.
The novel idea with the pyroelectric approach to fusion is in its application of the
pyroelectric effect to generate accelerating electric fields. This is done by heating the crystal from −34 °C to +7 °C over a period of a few minutes.
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 proposed in a conference paper by Geuther and Danon in 2004 and later in a publication discussing electron and ion acceleration by pyroelectric crystals. None of these later authors had prior knowledge of the earlier 1997 experimental work conducted by Dougar Jabon, Fedorovich, and Samsonenko which mistakenly believed that fusion occurred within the 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 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. In 2010, it was found that tungsten emitter tips are not necessary to increase the acceleration potential of pyroelectric crystals; the acceleration potential can allow positive ions to reach kinetic energies between 300 and 310 keV.
2005–2009
In April 2005, a
UCLA
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the C ...
team headed by chemistry professor
James K. Gimzewski and physics professor
Seth Putterman utilized a
tungsten
Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...
probe attached to a pyroelectric crystal to increase the electric field strength. Brian Naranjo, a graduate student working under Putterman, conducted the experiment demonstrating the use of a pyroelectric power source for producing fusion on a laboratory bench top device. The device used a
lithium tantalate () pyroelectric crystal to ionize deuterium atoms and to accelerate the deuterons towards a stationary erbium dideuteride (
Er D2) target. Around 1000 fusion reactions per second took place, each resulting in the production of an 820
keV helium-3
Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron. (In contrast, the most common isotope, helium-4, has two protons and two neutrons.) Helium-3 and hydrogen-1 are the only stable nuclides with ...
nucleus and a 2.45
MeV neutron. The team anticipates applications of the device as a
neutron generator
Neutron generators are neutron source devices which contain compact linear particle accelerators and that produce neutrons by fusing isotopes of hydrogen together. The nuclear fusion, fusion reactions take place in these devices by acceleratin ...
or possibly in
microthrusters for
space propulsion.
A team at
Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute (; RPI) is a private university, private research university in Troy, New York, United States. It is the oldest technological university in the English-speaking world and the Western Hemisphere. It was establishe ...
, led by Yaron Danon and his graduate student Jeffrey Geuther, improved upon the UCLA experiments using a device with two pyroelectric crystals and capable of operating at non-cryogenic temperatures.
Pyroelectric fusion has been hyped in the news media, which overlooked the work of Dougar Jabon, Fedorovich and Samsonenko.
Pyroelectric fusion is not related to the earlier claims of fusion reactions, having been observed during
sonoluminescence
Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound.
Sonoluminescence was first discovered in 1934 at the University of Cologne. It occurs when a sound wave of sufficient intensity induces a gaseo ...
(
bubble fusion) experiments conducted under the direction of
Rusi Taleyarkhan of
Purdue University
Purdue University is a Public university#United States, public Land-grant university, land-grant research university in West Lafayette, Indiana, United States, and the flagship campus of the Purdue University system. The university was founded ...
. Naranjo of the UCLA team was one of the main critics of these earlier prospective fusion claims from Taleyarkhan.
2010–present
The first successful results with pyroelectric fusion using a tritiated target was reported in 2010.
Putterman and Naranjo worked with T. Venhaus of
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...
to measure a 14.1 MeV neutron signal far above background.
See also
*
Neutron source
A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear p ...
s
*
Neutron generator
Neutron generators are neutron source devices which contain compact linear particle accelerators and that produce neutrons by fusing isotopes of hydrogen together. The nuclear fusion, fusion reactions take place in these devices by acceleratin ...
*
Pyroelectricity
References
External links
"UCLA crystal fusion website"* [https://www.nbcnews.com/id/wbna7654627 "Nuclear fusion on the desktop...really! - Science - nbcnews.com - an article to hype the great UCLA team! Again, see reference 2 (above) for who should first get the credit"]
"Supplementary methods for "Observation of nuclear fusion driven by a pyroelectric crystal" is found in reference 3 (above)"
{{Fusion methods
Nuclear fusion
Neutron sources