Inertial electrostatic confinement, or IEC, is a class of
fusion power
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices d ...
devices that use
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 ...
s to confine the
plasma rather than the more common approach using
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
s found in
magnetic confinement fusion
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma (physics), plasma. Magnetic confinement is one of two major branches of controlled fusi ...
(MCF) designs. Most IEC devices directly accelerate their fuel to fusion conditions, thereby avoiding energy losses seen during the longer heating stages of MCF devices. In theory, this makes them more suitable for using alternative
aneutronic fusion
Aneutronic fusion is any form of fusion power in which very little of the energy released is carried by Neutron, neutrons. While the lowest-threshold Nuclear fusion#Important reactions, nuclear fusion reactions release up to 80% of their energy in ...
fuels, which offer a number of major practical benefits and makes IEC devices one of the more widely studied approaches to fusion.
IEC devices were the very first
fusion products to reach the commercial market in 2000, as neutron generators. A company called NSD-Gradel developed a compact IEC device that fused ions and created neutrons and sold the product for several hundred thousand dollars.
As the negatively charged
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s and positively charged
ion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s in the plasma move in different directions in an electric field, the field has to be arranged in some fashion so that the two particles remain close together. Most IEC designs achieve this by pulling the electrons or ions across a potential well, beyond which the potential drops and the particles continue to move due to their
inertia
Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...
. Fusion occurs in this lower-potential area when ions moving in different directions collide. Because the motion provided by the field creates the energy levels needed for fusion, not random collisions with the rest of the fuel, the bulk of the plasma does not have to be hot and the systems as a whole work at much lower temperatures and energy levels than MCF devices.
One of the simpler IEC devices is the
fusor, which consists of two concentric metal wire spherical grids. When the grids are charged to a high
voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...
, the fuel gas ionizes. The field between the two then accelerates the fuel inward, and when it passes the inner grid the field drops and the ions continue inward toward the center. If they impact with another ion they may undergo fusion. If they do not, they travel out of the reaction area into the charged area again, where they are re-accelerated inward. Overall the physical process is similar to the
colliding beam fusion, although beam devices are linear instead of spherical. Other IEC designs, like the
polywell
The polywell is a proposed design for a fusion reactor using an electric and magnetic field to heat ions to fusion conditions.
The design is related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of e ...
, differ largely in the arrangement of the fields used to create the potential well.
A number of detailed theoretical studies have pointed out that the IEC approach is subject to a number of energy loss mechanisms that are not present if the fuel is evenly heated, or
"Maxwellian". These loss mechanisms appear to be greater than the rate of fusion in such devices, meaning they can never reach
fusion breakeven and thus be used for power production. These mechanisms are more powerful when the
atomic mass
Atomic mass ( or ) is the mass of a single atom. The atomic mass mostly comes from the combined mass of the protons and neutrons in the nucleus, with minor contributions from the electrons and nuclear binding energy. The atomic mass of atoms, ...
of the fuel increases, which suggests IEC also does not have any advantage with aneutronic fuels. Whether these critiques apply to specific IEC devices remains highly contentious.
Mechanism
For every
volt
The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Uni ...
that an ion is accelerated across, its kinetic energy gain corresponds to an increase of temperature of 11,604
kelvin
The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By de ...
s (K). For example, a typical
magnetic confinement fusion
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma (physics), plasma. Magnetic confinement is one of two major branches of controlled fusi ...
plasma is 15 keV, which corresponds to 170 megakelvin (MK). An ion with a charge of one can reach this temperature by being accelerated across a 15,000 V drop. This sort of voltage is easily achieved in common electrical devices; a typical
cathode-ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...
operates in this range.
In fusors, the voltage drop is made with a wire cage. However high
conduction
Conductor or conduction may refer to:
Biology and medicine
* Bone conduction, the conduction of sound to the inner ear
* Conduction aphasia, a language disorder
Mathematics
* Conductor (ring theory)
* Conductor of an abelian variety
* Condu ...
losses occur in fusors because most ions fall into the cage before fusion can occur. This prevents current fusors from ever producing net power.
History
1930s
Mark Oliphant
Sir Marcus Laurence Elwin Oliphant, (8 October 1901 – 14 July 2000) was an Australian physicist and humanitarian who played an important role in the first experimental demonstration of nuclear fusion and in the development of nuclear weapon ...
adapts
Cockcroft and
Walton's particle accelerator at the
Cavendish Laboratory
The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the School of Physical Sciences. The laboratory was opened in 1874 on the New Museums Site as a laboratory for experimental physics and is named ...
to create
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 ...
and
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 ...
by nuclear fusion.
1950s
Three researchers at
LANL including
Jim Tuck first explored the idea, theoretically, in a 1959 paper.
The idea had been proposed by a colleague. The concept was to capture electrons inside a positive cage. The electrons would accelerate the ions to fusion conditions.
Other concepts were being developed which would later merge into the IEC field. These include the publication of the
Lawson criterion
The Lawson criterion is a figure of merit used in nuclear fusion research. It compares the rate of energy being generated by fusion reactions within the fusion fuel to the rate of energy losses to the environment. When the rate of production is ...
by
John D. Lawson in 1957 in England. This puts on minimum criteria on power plant designs which do fusion using hot
Maxwellian plasma clouds. Also, work exploring how electrons behave inside the
biconic cusp
The biconic cusp, also known as the picket fence reactor, was one of the earliest suggestions for plasma confinement in a fusion reactor. It consists of two parallel electromagnets with the current running in opposite directions, creating opposit ...
, done by
Harold Grad group at the
Courant Institute in 1957. A biconic cusp is a device with two alike magnetic poles facing one another (i.e. north-north). Electrons and ions can be trapped between these.
1960s

In his work with vacuum tubes,
Philo Farnsworth
Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971), "The father of television", was the American inventor and pioneer who was granted the first patent for the television by the United States Government.
Burns, R. W. (1998), ''Televisi ...
observed that electric charge would accumulate in regions of the tube. Today, this effect is known as the
multipactor effect. Farnsworth reasoned that if ions were concentrated high enough they could collide, and fuse. In 1962, he filed a patent on a design using a positive inner cage to concentrate plasma, in order to achieve nuclear fusion. During this time,
Robert L. Hirsch joined the
Farnsworth Television labs and began work on what became the
fusor. Hirsch patented the design in 1966 and published the design in 1967.
The
Hirsch machine was a 17.8 cm diameter machine with 150 kV voltage drop across it and used ion beams to help inject material.
Simultaneously, a key plasma physics text was published by
Lyman Spitzer at
Princeton
Princeton University is a private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the Unit ...
in 1963. Spitzer took the ideal gas laws and adapted them to an ionized plasma, developing many of the fundamental equations used to model a plasma. Meanwhile,
magnetic mirror
A magnetic mirror, also known as a magnetic trap or sometimes as a pyrotron, is a type of magnetic confinement fusion device used in fusion power to trap high temperature Plasma (physics), plasma using magnetic fields. The mirror was one of the e ...
theory and
direct energy conversion were developed by
Richard F. Post's group at
LLNL
Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
.
["Mirror Systems: Fuel Cycles, loss reduction and energy recovery" by Richard F. Post, BNES Nuclear fusion reactor conferences at Culham laboratory, September 1969.] A magnetic mirror or magnetic bottle is similar to a biconic cusp except that the poles are reversed.
1980s
In 1980
Robert W. Bussard developed a cross between a fusor and
magnetic mirror
A magnetic mirror, also known as a magnetic trap or sometimes as a pyrotron, is a type of magnetic confinement fusion device used in fusion power to trap high temperature Plasma (physics), plasma using magnetic fields. The mirror was one of the e ...
, the
polywell
The polywell is a proposed design for a fusion reactor using an electric and magnetic field to heat ions to fusion conditions.
The design is related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of e ...
. The idea was to confine a non-neutral plasma using magnetic fields. This would, in turn, attract ions. This idea had been published previously, notably by
Oleg Lavrentiev in Russia. Bussard patented
[R.W.Bussard in U.S.Patent 4,826,646, "Method and apparatus for controlling charged particles", issued May 2, 1989] the design and received funding from
Defense Threat Reduction Agency
The Defense Threat Reduction Agency (DTRA) is both a defense agency and a combat support agency within the United States Department of Defense (DoD) for countering weapons of mass destruction (WMD; chemical, biological, radiological, nuclear ...
,
DARPA
The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adva ...
and the US
Navy
A navy, naval force, military maritime fleet, war navy, or maritime force is the military branch, branch of a nation's armed forces principally designated for naval warfare, naval and amphibious warfare; namely, lake-borne, riverine, littoral z ...
to develop the idea.
1990s
Bussard and
Nicholas Krall published theory and experimental results in the early nineties. In response, Todd Rider at
MIT
The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...
, under
Lawrence Lidsky developed general models of the device.
Rider argued that the device was fundamentally limited. That same year, 1995, William Nevins at
LLNL
Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
published a criticism of the polywell.
Nevins argued that the particles would build up
angular momentum
Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity – the total ang ...
, causing the dense core to degrade.
In the mid-nineties, Bussard publications prompted the development of fusors at the
University of Wisconsin–Madison
The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...
and at the
University of Illinois at Urbana–Champaign
The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United States. Established in 1867, it is the f ...
. Madison's machine was first built in 1995.
George H. Miley's team at Illinois built a 25 cm fusor which has produced 10
7 neutrons using deuterium gas
and discovered the "star mode" of fusor operation in 1994. The following year, the first "US-Japan Workshop on IEC Fusion" was conducted. This is now the premier conference for IEC researchers. At this time in Europe, an IEC device was developed as a commercial neutron source by
Daimler-Chrysler Aerospace under the name FusionStar. In the late nineties, hobbyist Richard Hull began building amateur fusors in his home.
["Living with a nuclear reactor" The Wall Street Journal, interview with Sam Schechner, https://www.youtube.com/watch?v=LJL3RQ4I-iE ] In March 1999, he achieved a neutron rate of 10
5 neutrons per second.
["The Neutron Club", Richard Hull, Accessed 6-9-2011, https://prometheusfusionperfection.com/category/fusor/ ] Hull and Paul Schatzkin started fusor.net in 1998. Through this open forum, a community of amateur fusioneers have done nuclear fusion using homemade fusors.
2000s
Despite demonstration in 2000 of 7200 hours of operation without degradation at high input power as a sealed reaction chamber with automated control the FusionStar project was canceled and the company NSD Ltd was founded. The spherical FusionStar technology was then further developed as a linear geometry system with improved efficiency and higher neutron output by NSD Ltd. which becam
NSD-FusionGmbH in 2005.
In early 2000, Alex Klein developed a cross between a polywell and ion beams.
["The Multipole Ion-beam eXperiment", Presentation, Alex Klien, 7–8 December 2011, 13th US-Japan IEC workshop, Sydney 2011] Using
Gabor lensing, Dr. Klein attempted to focus plasma into non-neutral clouds for fusion. He founded FP generation, which in April 2009 raised $3 million in financing from two venture funds.
The company developed the MIX and Marble machine, but ran into technical challenges and closed.
In response to Riders' criticisms, researchers at
LANL reasoned that a plasma oscillating could be at local thermodynamic equilibrium; this prompted the POPS and Penning trap machines.
At this time,
MIT
The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...
researchers became interested in fusors for space propulsion and powering space vehicles. Specifically, researchers developed
fusors with multiple inner cages. In 2005, Greg Piefer founded
Phoenix Nuclear Labs to develop the fusor into a neutron source for the mass production of medical isotopes.
["Phoenix Nuclear Labs meets neutron production milestone", PNL press release May 1, 2013, Ross Radel, Evan Sengbusch]
Robert Bussard began speaking openly about the Polywell in 2006. He attempted to generate interest
["The Advent of Clean Nuclear Fusion: Super-performance Space Power and Propulsion", Robert W. Bussard, Ph.D., 57th International Astronautical Congress, October 2–6, 2006] in the research, before passing away from multiple myeloma in 2007. His company was able to raise over ten million in funding from the US Navy in 2008 and 2009.
2010s
Bussard's publications prompted the
University of Sydney
The University of Sydney (USYD) is a public university, public research university in Sydney, Australia. Founded in 1850, it is the oldest university in both Australia and Oceania. One of Australia's six sandstone universities, it was one of the ...
to start research into electron trapping in polywells in 2010. The group has explored theory, modeled devices,
built devices, measured trapping
and simulated trapping. These machines were all low power and cost and all had a small
beta
Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...
ratio. In 2010, Carl Greninger founded the northwest nuclear consortium, an organization which teaches nuclear engineering principles to high school students, using a 60 kvolt fusor.
In 2012, Mark Suppes received attention, for a fusor. Suppes also measured electron trapping inside a polywell. In 2013, the first IEC textbook was published by
George H. Miley.
2020s
Avalanche Energy is a start-up with about $51 million in venture/DOD funding that is working on small (tens of centimetres), modular, fusion batteries producing 5kWe. They are targeting 600 kV for their device to achieve certain design goals. Their Orbitron concept electrostatically (magnetron-augmented) confines ions orbiting around a high voltage (100s of kVs) cathode in a high vacuum environment (p< 10 −8 Torr) surrounded by one or two anode shells separated by a dielectric. Concerns include breakdown of the vacuum/dielectric and insulator surface flashover.
Permanent magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, c ...
/electromagnet magnetic field generators are arranged coaxially around the anode. The magnetic field strength is targeted to exceed a
Hull cut-off condition, ranging from 50-4,000 kV. Candidate ions include protons (m/z=1), deuterium (m/z=2), tritium (m/z=3), lithium-6 (m/z=6), and boron-11 (m/z=11). Recent progress includes successful testing of a 300 kV
bushing.
Designs with cage
Fusor
The best known IEC device is the fusor.
This device typically consists of two wire cages inside a vacuum chamber. These cages are referred to as grids. The inner cage is held at a negative voltage against the outer cage. A small amount of
fusion fuel is introduced (
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 ...
gas being the most common). The voltage between the grids causes the fuel to ionize. The positive ions fall down the voltage drop toward the negative inner cage. As they accelerate, the
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 ...
does
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an ani ...
on the ions, accelerating them to fusion conditions. If these ions collide, they can fuse. Fusors can also use
ion guns rather than electric grids. Fusors are popular with amateurs, because they can easily be constructed, can regularly produce fusion and are a practical way to study
nuclear physics
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
Nuclear physics should not be confused with atomic physics, which studies th ...
. Fusors have also been used as a commercial
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 ...
for industrial applications.
No fusor has come close to producing a significant amount of
fusion power
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices d ...
. They can be dangerous if proper care is not taken because they require high voltages and can produce harmful radiation (
neutrons
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The neutron was discovered by James Chadwick in 1932, leading to the discovery of nuclear fission in 1938, the f ...
and
X-ray
An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
s). Often, ions collide with the cages or wall. This
conducts energy away from the device limiting its performance. In addition, collisions heat the grids, which limits high-power devices. Collisions also spray high-mass ions into the reaction chamber, pollute the plasma, and cool the fuel.
POPS
In examining
nonthermal plasma, workers at
LANL realized that scattering was more likely than fusion. This was due to the
coulomb scattering
Coulomb scattering is the elastic scattering of charged particles by the Coulomb interaction.
The physical phenomenon was used by Ernest Rutherford in a classic 1911 paper that eventually led to the widespread use of scattering in particle phy ...
cross section being larger than the fusion cross section. In response they built POPS,
a machine with a wire cage, where ions are moving at steady-state, or oscillating around. Such plasma can be at local thermodynamic equilibrium.
[net energy gain. Working off this design, researchers in Russia simulated the POPS design using ]particle-in-cell
In plasma physics, the particle-in-cell (PIC) method refers to a technique used to solve a certain class of partial differential equations. In this method, individual particles (or fluid elements) in a Lagrangian frame are tracked in continuous ...
code in 2009. This reactor concept becomes increasingly efficient as the size of the device shrinks. However, very high transparencies (>99.999%) are required for successful operation of the POPS concept. To this end S. Krupakar Murali et al., suggested that carbon nanotube
A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range ( nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized:
* ''Single-walled carbon nanotubes'' (''S ...
s can be used to construct the cathode grids.[S. Krupakar Murali et al.,"Carbon Nanotubes in IEC Fusion Reactors", ANS 2006 Annual Meeting, June 4–8, Reno, Nevada.] This is also the first (suggested) application of carbon nanotubes directly in any fusion reactor.
Designs with fields
Several schemes attempt to combine magnetic confinement
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of controlled fusion research, alo ...
and electrostatic
Electrostatics is a branch of physics that studies slow-moving or stationary electric charges.
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word (), mean ...
fields with IEC. The goal is to eliminate the inner wire cage of the fusor, and the resulting problems.
Polywell
The polywell uses a magnetic field to trap electrons. When electrons or ions move into a dense field, they can be reflected by the magnetic mirror effect. A polywell is designed to trap electrons in the center, with a dense magnetic field surrounding them. This is typically done using six electromagnets in a box. Each magnet is positioned so their poles face inward, creating a null point in the center. The electrons trapped in the center form a "virtual electrode" Ideally, this electron cloud accelerates ions to fusion conditions.
Penning trap
A Penning trap
A Penning trap is a device for the storage of charged particles using a homogeneous magnetic field and a quadrupole electric field. It is mostly found in the physical sciences and related fields of study for precision measurements of properties o ...
uses both an electric and a magnetic field to trap particles, a magnetic field to confine particles radially and a quadrupole electric field to confine the particles axially.
In a Penning trap fusion reactor, first the magnetic and electric fields are turned on. Then, electrons are emitted into the trap, caught and measured. The electrons form a virtual electrode similar to that in a polywell, described above. These electrons are intended to then attract ions, accelerating them to fusion conditions.
In the 1990s, researchers at LANL built a Penning trap to do fusion experiments. Their device (PFX) was a small (millimeters) and low power (one fifth of a tesla, less than ten thousand volts) machine.
Marble
MARBLE (multiple ambipolar recirculating beam line experiment) was a device which moved electrons and ions back and forth in a line.["The Multiple Ambipolar Recirculating Beam Line Experiment" Poster presentation, 2011 US-Japan IEC conference, Dr. Alex Klein] Particle beams were reflected using electrostatic optics. These optics made static voltage surfaces in free space. Such surfaces reflect only particles with a specific kinetic energy, while higher-energy particles can traverse these surfaces unimpeded, although not unaffected. Electron trapping and plasma behavior was measured by Langmuir probe
A Langmuir probe is a device used to determine the electron temperature, electron density, and electric potential of a plasma. It works by inserting one or more electrodes into a plasma, with a constant or time-varying electric potential between ...
. Marble kept ions on orbits that do not intersect grid wires—the latter also improves the space charge limitations by multiple nesting of ion beams at several energies. Researchers encountered problems with ion losses at the reflection points. Ions slowed down when turning, spending much time there, leading to high conduction
Conductor or conduction may refer to:
Biology and medicine
* Bone conduction, the conduction of sound to the inner ear
* Conduction aphasia, a language disorder
Mathematics
* Conductor (ring theory)
* Conductor of an abelian variety
* Condu ...
losses.
MIX
The multipole ion-beam experiment (MIX) accelerated ions and electrons into a negatively charged electromagnet.[ Ions were focused using Gabor lensing. Researcher had problems with a very thin ion-turning region very close to a solid surface][ where ions could be conducted away.
]
Magnetically insulated
Devices have been proposed where the negative cage is magnetically insulated from the incoming plasmas.
General criticism
In 1995, Todd Rider critiqued all fusion power schemes using plasma systems not at thermodynamic equilibrium. Rider assumed that plasma clouds at equilibrium had the following properties:
* They were quasineutral, where the positives and negatives are equally mixed together.
* They had evenly mixed fuel.
* They were isotropic
In physics and geometry, isotropy () is uniformity in all orientations. Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence '' anisotropy''. ''Anisotropy'' is also ...
, meaning that its behavior was the same in any given direction.
* The plasma had a uniform energy and temperature throughout the cloud.
* The plasma was an unstructured Gaussian sphere.
Rider argued that if such system was sufficiently heated, it could not be expected to produce net power, due to high X-ray
An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
losses.
Other fusion researchers such as Nicholas Krall, Robert W. Bussard, Norman Rostoker, and Monkhorst disagreed with this assessment. They argue that the plasma conditions inside IEC machines are not quasineutral and have non-thermal energy distributions. Because the electron has a mass and diameter much smaller than the ion, the electron temperature can be several orders of magnitude different than the ions. This may allow the plasma to be optimized, whereby cold electrons would reduce radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:
* ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
losses and hot ions would raise fusion rates.
Thermalization
The primary problem that Rider has raised is the thermalization of ions. Rider argued that, in a quasineutral plasma where all the positives and negatives are distributed equally, the ions will interact. As they do, they exchange energy, causing their energy to spread out (in a Wiener process
In mathematics, the Wiener process (or Brownian motion, due to its historical connection with Brownian motion, the physical process of the same name) is a real-valued continuous-time stochastic process discovered by Norbert Wiener. It is one o ...
) heading to a bell curve (or Gaussian function
In mathematics, a Gaussian function, often simply referred to as a Gaussian, is a function (mathematics), function of the base form
f(x) = \exp (-x^2)
and with parametric extension
f(x) = a \exp\left( -\frac \right)
for arbitrary real number, rea ...
) of energy. Rider focused his arguments within the ion population and did not address electron-to-ion energy exchange or non-thermal plasmas.
This spreading of energy causes several problems. One problem is making more and more cold ions, which are too cold to fuse. This would lower output power. Another problem is higher energy ions which have so much energy that they can escape the machine. This lowers fusion rates while raising conduction losses, because as the ions leave, energy is carried away with them.
Radiation
Rider estimated that once the plasma is thermalized the radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:
* ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
losses would outpace any amount of fusion energy generated. He focused on a specific type of radiation: X-ray
An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
radiation. A particle in a plasma will radiate light anytime it speeds up or slows down. This can be estimated using the Larmor formula
In electrodynamics, the Larmor formula is used to calculate the total power radiated by a nonrelativistic point charge as it accelerates. It was first derived by J. J. Larmor in 1897, in the context of the wave theory of light.
When any charge ...
. Rider estimated this for D–T (deuterium–tritium fusion), D–D (deuterium fusion), and D–He3 (deuterium–helium 3 fusion), and that breakeven operation with any fuel except D–T is difficult.
Core focus
In 1995, Nevins argued that such machines would need to expend a great deal of energy maintaining ion focus in the center. The ions need to be focused so that they can find one another, collide, and fuse. Over time the positive ions and negative electrons would naturally intermix because of electrostatic
Electrostatics is a branch of physics that studies slow-moving or stationary electric charges.
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word (), mean ...
attraction. This causes the focus to be lost. This is core degradation. Nevins argued mathematically, that the fusion gain (ratio of fusion power produced to the power required to maintain the non-equilibrium ion distribution function) is limited to 0.1 assuming that the device is fueled with a mixture of 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 ...
and 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 ...
.[
The core focus problem was also identified in fusors by Tim Thorson at the ]University of Wisconsin–Madison
The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...
during his 1996 doctoral work. Charged ions would have some motion before they started accelerating in the center. This motion could be a twisting motion, where the ion had angular momentum
Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity – the total ang ...
, or simply a tangential velocity. This initial motion causes the cloud in the center of the fusor to be unfocused.
Brillouin limit
In 1945, Columbia University professor Léon Brillouin, suggested that there was a limit to how many electrons one could pack into a given volume. This limit is commonly referred to as the Brillouin limit or Brillouin density, this is shown below.
:
Where B is the magnetic field, the permeability of free space, m the mass of confined particles, and c the speed of light. This may limit the charge density inside IEC devices.
Commercial applications
Since fusion reactions generates neutrons, the fusor has been developed into a family of compact sealed reaction chamber neutron generators for a wide range of applications that need moderate neutron output rates at a moderate price. Very high output neutron sources may be used to make products such as molybdenum-99[ and ]nitrogen-13
Nitrogen-13 (13N) is a radioisotope of nitrogen used in positron emission tomography (PET). It has a half-life of a little under ten minutes, so it must be made at the PET site. A cyclotron may be used for this purpose.
Nitrogen-13 is used to tag ...
, medical isotopes used for PET
A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive/ cute appearances, inte ...
scans.
Devices
Government and commercial
*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 ...
Researchers developed POPS and Penning trap[
*]Turkish Atomic Energy Authority
The Turkish Energy, Nuclear and Mineral Research Agency was formed from other agencies and the Turkish Atomic Energy Authority which was the official nuclear energy institution of Turkey. The headquarters is located in Ankara since 1956, the y ...
In 2013 this team built a fusor at the Saraykoy Nuclear Research and Training center in Turkey. This fusor can reach and do deuterium fusion, producing neutrons per second.
*ITT Corporation
ITT Inc., formerly ITT Corporation, is an American worldwide manufacturing company based in Stamford, Connecticut. The company produces specialty components for the aerospace, transportation, energy and industrial markets. ITT's three businesses ...
Hirschs original machine was a 17. diameter machine with voltage drop across it. This machine used ion beams.
* Phoenix Nuclear Labs has developed a commercial neutron source based on a fusor, achieving neutrons per second with the deuterium-deuterium fusion reaction for 132 hours of continuous operation.[
* Energy Matter Conversion Inc Is a company in Santa Fe which has developed large high powered polywell devices for the US Navy.
* NSD-Gradel-Fusion sealed IEC neutron generators for DD (2.5 MeV) or DT (14 MeV) with a range of maximum outputs are manufactured by Gradel sárl in Luxembourg.]
* Atomic Energy Organization of Iran Researchers at Shahid Beheshti University in Iran have built a diameter fusor which can produce neutrons per second at 80 kilovolts using deuterium gas.
*Avalanche Energy has received $5 million in venture capital to build their prototype.
*CPP-IPR in India, has achieved a significant milestone by pioneering the development of India's first Inertial Electrostatic Confinement Fusion (IECF) neutron source. The device is capable of reaching an energy potential of -92kV. It can generate a neutron yield of up to 107 neutrons per second by deuterium fusion. The primary objective of this program is to propel the advancement of portable and handheld neutron sources, characterized by both linear and spherical geometries.
Universities
*Tokyo Institute of Technology
The Tokyo Institute of Technology () was a public university in Meguro, Tokyo, Japan. It merged with Tokyo Medical and Dental University to form the Institute of Science Tokyo on 1 October 2024.
The Tokyo Institute of Technology was a De ...
has four IEC devices of different shapes: a spherical machine, a cylindrical device, a co-axial double cylinder and a magnetically assisted device.
*University of Wisconsin–Madison
The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...
– A group at Wisconsin–Madison has several large devices, since 1995.
*University of Illinois at Urbana–Champaign
The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United States. Established in 1867, it is the f ...
– The fusion studies laboratory has built a ~25 cm fusor which has produced neutrons using deuterium gas.
*Massachusetts Institute of Technology
The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
– For his doctoral thesis in 2007, Carl Dietrich built a fusor and studied its potential use in spacecraft propulsion.["Improving Particle Confinement in Inertial Electrostatic Fusion for Spacecraft Power and Propulsion" submitted to the Department of Aeronautics and Astronautics, Carl Dietrich, February 2007] Also, Thomas McGuire studied multiple well fusors for applications in spaceflight.
*University of Sydney
The University of Sydney (USYD) is a public university, public research university in Sydney, Australia. Founded in 1850, it is the oldest university in both Australia and Oceania. One of Australia's six sandstone universities, it was one of the ...
has built several IEC devices and also low power, low beta ratio polywell
The polywell is a proposed design for a fusion reactor using an electric and magnetic field to heat ions to fusion conditions.
The design is related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of e ...
s. The first was constructed of Teflon rings and was about the size of a coffee cup. The second has ~12" diameter full casing, metal rings.
*Eindhoven Technical University
*Amirkabir University of Technology and Atomic Energy Organization of Iran have investigated the effect of strong pulsed magnetic fields on the neutron production rate of IEC device. Their study showed that by 1-2 Tesla magnetic field it is possible to increase the discharge current and neutron production rate more than ten times with respect to the ordinary operation.
*The Institute of Space Systems at the University of Stuttgart
The University of Stuttgart () is a research university located in Stuttgart, Germany. It was founded in 1829 and is organized into 10 faculties. It is one of the oldest technical universities in Germany with programs in civil, mechanical, ind ...
is developing IEC devices for plasma physics research, and as an electric propulsion
Spacecraft electric propulsion (or just electric propulsion) is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generating thrust to modify the velocity of a ...
device, the IECT (Inertial Electrostatic Confinement Thruster).
See also
* Fusor
* List of fusion experiments
Experiments directed toward developing fusion power are invariably done with dedicated machines which can be classified according to the principles they use to confine the plasma (physics), plasma fuel and keep it hot.
The major division is bet ...
* Northwest Nuclear Consortium
* Philo Farnsworth
Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971), "The father of television", was the American inventor and pioneer who was granted the first patent for the television by the United States Government.
Burns, R. W. (1998), ''Televisi ...
* Phoenix Nuclear labs
* Polywell
The polywell is a proposed design for a fusion reactor using an electric and magnetic field to heat ions to fusion conditions.
The design is related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of e ...
* Robert Bussard
* Taylor Wilson
Patents
* P.T. Farnsworth, , June 1966 (Electric discharge — Nuclear interaction)
* P.T. Farnsworth, . June 1968 (Method and apparatus)
* Hirsch, Robert, . September 1970 (Apparatus)
* Hirsch, Robert, . September 1970 (Generating apparatus — Hirsch/Meeks)
* Hirsch, Robert, . October 1970 (Lithium-Ion source)
* Hirsch, Robert, . April 1972 (Reduce plasma leakage)
* Hirsch, Robert, . May 1972 (Electrostatic containment)
* R.W. Bussard, "Method and apparatus for controlling charged particles", , May 1989 (Method and apparatus — Magnetic grid fields)
* R.W. Bussard, "Method and apparatus for creating and controlling nuclear fusion reactions", , November 1992 (Method and apparatus — Ion acoustic waves)
* S.T. Brookes, "Nuclear fusion reactor", UK patent GB2461267, May 2012
* T.V. Stanko, "Nuclear fusion device", UK patent GB2545882, July 2017
References
External links
Polywell Fusion: Electrostatic Fusion in a Magnetic Cusp
talk at Microsoft Research
University of Wisconsin-Madison IEC homepage
IEC Overview
*From Proceedings of the 1999 Fusion Summer Study (Snowmass, Colorado):
Summary of Physics Aspects of Some Emerging Concepts
Inertial-Electrostatic Confinement (IEC) of a Fusion Plasma with Grids
Fusion from Television? (American Scientist Magazine, July-August 1999)
Should Google Go Nuclear? Clean, cheap, nuclear power (no, really)
NSD-Gradel-Fusion
NSD-Gradel-Fusion (Luxembourg)
{{Fusion power
Fusion power
de:Elektrostatischer Trägheitseinschluss