Migma
Encyclopedia
Migma was a proposed inertial electrostatic confinement
fusion reactor designed by Bogdan Maglich
in the early 1970s. Migma uses self-intersecting beams of ion
s from small particle accelerator
s to force the ions to fuse. It was an area of some research in the 1970s and early 1980s, but lack of funding precluded further development. Similar systems using larger collections of particles were referred to as "macron
s".
. The barrier is lowered for atoms with less positive charge, those with the fewest number of proton
s, and the strong force is increased with additional nucleons, the total number of protons and neutron
s. This means that a combination of deuterium
and tritium
has the lowest coulomb barrier, at about 100 keV (see requirements for fusion).
When the fuel is heated to high energies the electron
s disassociate from the nuclei, which are left as ions in a gas-like plasma
. Any particles in a gas are distributed across a wide range of energies in a spectrum known as the Maxwell-Boltzmann distribution. At any given temperature the majority of the particles are at lower energies, with a "long tail" containing smaller numbers of particles at much higher energies. So while 100 KeV represents a temperature of over one billion degrees, in order to produce fusion events the fuel does not have to be heated to this temperature as a whole. Even at a much lower temperature, the rate of fusion may be high enough to provide useful power output as long as it is confined for some period of time. Increased density also increases the rate, as the energy from the reactions will heat the surrounding fuel and potentially incite fusion in it as well. The combination of temperature, density and confinement time is known as the Lawson criterion
.
Two primary approaches have developed to attack the fusion energy problem. In the inertial confinement
approach the fuel is quickly squeezed to extremely high densities, increasing the internal temperature in the process. There is no attempt to maintain these conditions for any period of time, the fuel explodes outward as soon as the force is released. The confinement time is on the order of nanoseconds, so the temperatures and density have to be very high in order to any appreciable amount of the fuel to undergo fusion. This approach has been successful in producing fusion reactions, but to date the devices that can provide the compression, typically laser
s, require more energy than the reactions produce.
In the more widely studied magnetic confinement
approach, the plasma, which is electrically charged, is confined with magnetic fields. The fuel is slowly heated until some of the fuel in the tail of the temperature distribution starts undergoing fusion. At the temperatures and densities that are possible using magnets the fusion process is fairly slow, so this approach requires long confinement times on the order of tens of seconds, or even minutes. Confining a gas at millions of degrees for this short of time scale has proven difficult, although modern experimental machines are approaching the conditions needed for net power production.
, which are a million times more powerful.
The original Migma concept used two small accelerators arranged in a collider arrangement, but this reaction proved to have fairly low cross-sections and most of the particles exited the experimental chamber without colliding. Maglich's concept modified the arrangement to include a powerful magnetic confinement system in the target area; ions injected into the center would orbit around the center for some time, thereby greatly increasing the chance that any given particle would undergo a collision given a long enough confinement time. It was not obvious that this approach could work, as positively charged ions would all orbit the magnetic field in the same direction. However, Maglich showed that it was nevertheless possible to produce self-intersecting orbital paths in such a system, and he was able to point to experimental results from the intersecting beams at CERN
to back up the proposal with real-world numbers.
Several Migma experimental devices were built in the 1970s; the original in 1972, Migma II in 1975, Migma III in 1978, and eventually culminating with the Migma IV in 1982. These devices were relatively small, only a few meters long along the accelerator beamline with a disk-shaped target chamber about 2 m in diameter and 1 m thick. This device achieved the record fusion triple product
(density × energy-confinement-time × mean energy)
of 4e14 keV sec cm−3 in 1982, a record that was not approached by a conventional tokamak until JET achieved 3e14 keV sec cm−3 in 1987.
Maglich has been attempting to secure funding for a follow-on version for some time now, unsuccessfully. According to an article in The Scientist
, Maglich has been involved in an apparently acrimonious debate with the various funding agencies since the 1980s.
. These processes remove energy from the fast particles being injected, lowering their temperature and feeding it into the surrounding fuel mass. It appears there is no obvious way to fix this problem. Whether this concern applies to the Migma is not clear.
Inertial electrostatic confinement
Inertial electrostatic confinement is a concept for retaining a plasma using an electrostatic field. The field accelerates charged particles radially inward, usually in a spherical but sometimes in a cylindrical geometry. Ions can be confined with IEC in order to achieve controlled nuclear fusion...
fusion reactor designed by Bogdan Maglich
Bogdan Maglich
Bogdan Castle Maglich is a nuclear physicist and the leading advocate of a purported non-radioactive aneutronic fusion energy source. Maglich's Migma fusion would use colliding ion beams. He is the son of a lawyer and elected member of the Yugoslav Royal Parliament...
in the early 1970s. Migma uses self-intersecting beams of ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s from small particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s to force the ions to fuse. It was an area of some research in the 1970s and early 1980s, but lack of funding precluded further development. Similar systems using larger collections of particles were referred to as "macron
Macron
A macron, from the Greek , meaning "long", is a diacritic placed above a vowel . It was originally used to mark a long or heavy syllable in Greco-Roman metrics, but now marks a long vowel...
s".
Conventional fusion
Fusion takes place when atoms come into close proximity and the nuclear strong force pulls their nuclei together. Counteracting this process is the fact that the nuclei are all positively charged, and thus repel each other due to the electrostatic force. In order for fusion to occur, the nuclei must have enough energy to overcome this coulomb barrierCoulomb barrier
The Coulomb barrier, named after Coulomb's law, which is named after physicist Charles-Augustin de Coulomb , is the energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo a nuclear reaction...
. The barrier is lowered for atoms with less positive charge, those with the fewest number of proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s, and the strong force is increased with additional nucleons, the total number of protons and neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s. This means that a combination of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
and tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
has the lowest coulomb barrier, at about 100 keV (see requirements for fusion).
When the fuel is heated to high energies the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s disassociate from the nuclei, which are left as ions in a gas-like plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
. Any particles in a gas are distributed across a wide range of energies in a spectrum known as the Maxwell-Boltzmann distribution. At any given temperature the majority of the particles are at lower energies, with a "long tail" containing smaller numbers of particles at much higher energies. So while 100 KeV represents a temperature of over one billion degrees, in order to produce fusion events the fuel does not have to be heated to this temperature as a whole. Even at a much lower temperature, the rate of fusion may be high enough to provide useful power output as long as it is confined for some period of time. Increased density also increases the rate, as the energy from the reactions will heat the surrounding fuel and potentially incite fusion in it as well. The combination of temperature, density and confinement time is known as the Lawson criterion
Lawson criterion
In nuclear fusion research, the Lawson criterion, first derived on fusion reactors by John D. Lawson in 1955 and published in 1957, is an important general measure of a system that defines the conditions needed for a fusion reactor to reach ignition, that is, that the heating of the plasma by the...
.
Two primary approaches have developed to attack the fusion energy problem. In the inertial confinement
Inertial confinement fusion
Inertial confinement fusion is a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that most often contains a mixture of deuterium and tritium....
approach the fuel is quickly squeezed to extremely high densities, increasing the internal temperature in the process. There is no attempt to maintain these conditions for any period of time, the fuel explodes outward as soon as the force is released. The confinement time is on the order of nanoseconds, so the temperatures and density have to be very high in order to any appreciable amount of the fuel to undergo fusion. This approach has been successful in producing fusion reactions, but to date the devices that can provide the compression, typically laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s, require more energy than the reactions produce.
In the more widely studied magnetic confinement
Magnetic confinement fusion
Magnetic confinement fusion is an approach to generating fusion power that uses magnetic fields to confine the hot fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research, the other being inertial confinement fusion. The magnetic approach is...
approach, the plasma, which is electrically charged, is confined with magnetic fields. The fuel is slowly heated until some of the fuel in the tail of the temperature distribution starts undergoing fusion. At the temperatures and densities that are possible using magnets the fusion process is fairly slow, so this approach requires long confinement times on the order of tens of seconds, or even minutes. Confining a gas at millions of degrees for this short of time scale has proven difficult, although modern experimental machines are approaching the conditions needed for net power production.
Migma fusion
The Migma approach avoided the problem of heating the mass of fuel to these temperatures by accelerating the ions directly in a particle accelerator. Accelerators capable of 100 keV are fairly simple to build, although in order to make up for various losses the energy provided is generally higher. Later Migma testbed devices used accelerators of about 1 MeV, fairly small compared to the large research reactors like TevatronTevatron
The Tevatron is a circular particle accelerator in the United States, at the Fermi National Accelerator Laboratory , just east of Batavia, Illinois, and is the second highest energy particle collider in the world after the Large Hadron Collider...
, which are a million times more powerful.
The original Migma concept used two small accelerators arranged in a collider arrangement, but this reaction proved to have fairly low cross-sections and most of the particles exited the experimental chamber without colliding. Maglich's concept modified the arrangement to include a powerful magnetic confinement system in the target area; ions injected into the center would orbit around the center for some time, thereby greatly increasing the chance that any given particle would undergo a collision given a long enough confinement time. It was not obvious that this approach could work, as positively charged ions would all orbit the magnetic field in the same direction. However, Maglich showed that it was nevertheless possible to produce self-intersecting orbital paths in such a system, and he was able to point to experimental results from the intersecting beams at CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
to back up the proposal with real-world numbers.
Several Migma experimental devices were built in the 1970s; the original in 1972, Migma II in 1975, Migma III in 1978, and eventually culminating with the Migma IV in 1982. These devices were relatively small, only a few meters long along the accelerator beamline with a disk-shaped target chamber about 2 m in diameter and 1 m thick. This device achieved the record fusion triple product
Lawson criterion
In nuclear fusion research, the Lawson criterion, first derived on fusion reactors by John D. Lawson in 1955 and published in 1957, is an important general measure of a system that defines the conditions needed for a fusion reactor to reach ignition, that is, that the heating of the plasma by the...
(density × energy-confinement-time × mean energy)
of 4e14 keV sec cm−3 in 1982, a record that was not approached by a conventional tokamak until JET achieved 3e14 keV sec cm−3 in 1987.
Maglich has been attempting to secure funding for a follow-on version for some time now, unsuccessfully. According to an article in The Scientist
The Scientist
The Scientist: Magazine of Life Sciences is a professional magazine intended for life scientists. Coverage includes reviews of widely noticed research papers, informing its audience of current research, updates to technology, updates to career information, profiles of scientists achieving...
, Maglich has been involved in an apparently acrimonious debate with the various funding agencies since the 1980s.
Migma drawbacks
One more recent concern with the Migma design is that the particles lose energy through collisions with other particles in the reaction area, and through other interactions that only become an issue at very high energies, notably bremsstrahlungBremsstrahlung
Bremsstrahlung is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic energy, which is converted into a photon because energy is conserved. The term is...
. These processes remove energy from the fast particles being injected, lowering their temperature and feeding it into the surrounding fuel mass. It appears there is no obvious way to fix this problem. Whether this concern applies to the Migma is not clear.
External links
- Visionary Physicist's Crusade Serves As Lesson In Futility in The ScientistThe ScientistThe Scientist: Magazine of Life Sciences is a professional magazine intended for life scientists. Coverage includes reviews of widely noticed research papers, informing its audience of current research, updates to technology, updates to career information, profiles of scientists achieving...
- Patent 4788024: Apparatus and method for obtaining a self-colliding beam of charged particles operating above the space charge limit
- "Figure Eights for Fusion: The Migma's Mix," by Dietrick E. Thomsen, Science News, 1973