Bumpy torus

The bumpy torus is a class of magnetic fusion energy devices that consist of a series of magnetic mirrors connected end-to-end to form a closed torus. Such an arrangement is not stable on its own, and most bumpy torus designs use secondary fields or relativistic electrons to create a stable field inside the reactor. The main disadvantage of magnetic mirror confinement, that of excessive plasma leakage, is circumvented by the arrangement of multiple mirrors end-to-end in a ring. It is described as "bumpy" because the fuel ions comprising the plasma tend to concentrate inside the mirrors at greater density than the leakage currents between mirror cells.

Bumpy torus designs were an area of active research starting in the 1960s and continued until 1986 with the ELMO (ELectro Magnetic Orbit) Bumpy Torus at the Oak Ridge National Laboratory.[1] One in particular has been described: "Imagine a series of magnetic mirror machines placed end to end and twisted into a torus. An ion or electron that leaks out of one mirror cavity finds itself in another mirror cell. This constitutes a bumpy torus."[2] These demonstrated problems and most research on the concept has ended.

References

  1. ^ Uckan, Dandl, Hendrick, Bettis, Lidsky, McAlees, Santoro, Watts, Yeh. "THE ELMO BUMPY TORUS (EBT) REACTOR". osti dot gov. Oak Ridge National Laboratory. Retrieved June 1, 2017.CS1 maint: Multiple names: authors list (link)
  2. ^ Cobble, Jim. "The ELMO Bumpy Torus Experiment, A Microwave-Driven, Steady-State Fusion Machine at ORNL" (PDF). iccworkshops dot org. Los Alamos National Laboratory, August 18, 2011. Retrieved June 1, 2017.
600-cell

In geometry, the 600-cell is the convex regular 4-polytope (four-dimensional analogue of a Platonic solid) with Schläfli symbol {3,3,5}. It is also called a C600, hexacosichoron and hexacosihedroid.The 600-cell is regarded as the 4-dimensional analog of the icosahedron, since it has five tetrahedra meeting at every edge, just as the icosahedron has five triangles meeting at every vertex. It is also called a tetraplex (abbreviated from "tetrahedral complex") and polytetrahedron, being bounded by tetrahedral cells.

Astron (fusion reactor)

The Astron is a type of fusion power device pioneered by Nicholas Christofilos and built at the Lawrence Livermore National Laboratory during the 1960s and 70s. Astron used a unique confinement system that avoided several of the problems found in contemporary designs like the stellarator and magnetic mirror. Development was greatly slowed by a series of changes to the design that were made with limited oversight, leading to a review committee being set up to oversee further development. The Astron was unable to meet the performance goals set for it by the committee; funding was cancelled in 1972 and development wound down in 1973. Work on similar designs appears to have demonstrated a theoretical problem in the very design that suggests it could never be used for practical generation.

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 designed to harness this energy are known as fusion reactors.

Fusion processes require fuel and a confined environment with sufficient temperature, pressure and confinement interval, to create a plasma in which fusion can occur. In stars, the most common fuel is hydrogen, and gravity creates the conditions needed for fusion energy production.

Fusion reactors generally use hydrogen isotopes such as deuterium and tritium, which react more easily, and create a confined plasma of millions of degrees using inertial (laser) or magnetic methods (tokamak and similar), although many other concepts have been attempted. The major challenge in realising fusion power are to engineer a system that can confine the plasma long enough at high enough temperature and density for a long term reaction to occur. A second issue that affects common reactions, is managing neutrons that are released during the reaction, which over time degrade many common materials used within the reaction chamber.

As a source of power, nuclear fusion is expected to have several theoretical advantages over fission. These include reduced radioactivity in operation and little high-level nuclear waste, ample fuel supplies, and increased safety. However, achieving the necessary temperature/pressure/duration combination has proven to be difficult to produce in a practical and economical manner. Research into fusion reactors began in the 1940s, but to date, no design has produced more fusion power output than the electrical power input, defeating the purpose.Fusion researchers have investigated various confinement concepts. The early emphasis was on three main systems: z-pinch, stellarator and magnetic mirror. The current leading designs are the tokamak and inertial confinement (ICF) by laser. Both designs are under research at very large scales, most notably the ITER tokamak in France, and the National Ignition Facility laser in the United States. Researchers are also studying other designs that may offer cheaper approaches. Among these alternatives there is increasing interest in magnetized target fusion and inertial electrostatic confinement, stellerator and proton-boron.

Magnetic mirror

A magnetic mirror, known as a magnetic trap (магнитный захват) in Russia and briefly as a pyrotron in the US, is a type of magnetic confinement device used in fusion power to trap high temperature plasma using magnetic fields. The mirror was one of the earliest major approaches to fusion power, along with the stellarator and z-pinch machines.

In a magnetic mirror, a configuration of electromagnets is used to create an area with an increasing density of magnetic field lines at either end of the confinement area. Particles approaching the ends experience an increasing force that eventually causes them to reverse direction and return to the confinement area. This mirror effect will only occur for particles within a limited range of velocities and angles of approach, those outside the limits will escape, making mirrors inherently "leaky".

An analysis of early fusion devices by Edward Teller pointed out that the basic mirror concept is inherently unstable. In 1960, Soviet researchers introduced a new "minimum-B" configuration to address this, which was then modified by UK researchers into the "baseball coil" and by the US to "yin-yang magnet" layout. Each of these introductions led to further increases in performance, damping out various instabilities, but required ever-large magnet systems. The tandem mirror concept, developed in the US and Russia at about the same time, offered a way to make energy-positive machines without requiring enormous magnets and power input.

By the late 1970s, many of the design problems were considered solved, and Lawrence Livermore Laboratory began the design of the Mirror Fusion Test Facility (MFTF) based on these concepts. The machine was completed in 1986, but by this time, experiments on the smaller Tandem Mirror Experiment revealed new problems. In a round of budget cuts, MFTF was mothballed, and eventually scrapped. The mirror approach has since seen less development, in favor of the tokamak, but mirror research continues today in countries like Japan and Russia.A fusion reactor concept called the Bumpy torus made use of a series of magnetic mirrors joined in a ring. It was investigated at the Oak Ridge National Laboratory until 1986.

Nicholas Krall

Nicholas Krall is an American theoretical plasma physicist. Dr Krall has authored over 160 science publications and has contributed to the fields of electron scattering, plasma stability, high energy nuclear physics and magnetohydrodynamics. He has worked at General Atomics, the University of California, San Diego, the Naval Research Laboratory and University of Maryland.

Richard Geller (physicist)

Richard Geller (25 April 1927 – 1 July 2007) was an experimental nuclear and plasma physicist. He was born in Vienna and died in Grenoble.

Geller received his undergraduate degree from the Conservatoire National des Arts et Métiers, Paris and his Doctorat en Sciences, under Prof. F. Perrin from the Sorbonne (1954). He was hired in 1948 by F. Joliot Curie to work at Commissariat à l'énergie atomique (CEA; Atomic Energy Commission) and remained there until leaving in 1992, with the exception of a sabbatical at Stanford University (1961–1962), where, as a research associate, he developed the first bumpy torus plasma.

In the 1960s he developed electron cyclotron resonance heating of plasma physics as part of controlled fusion. In the 1970s and 1980s his group developed the Electron Cyclotron Resonance Ion Source, ECRIS, for use in accelerators on for particle physics, nuclear physics, and medical applications.

In 1992 he went to the Institut des Sciences Nucléaires de Grenoble, where he developed a new electron cyclotron resonance (ECR) method that was used to generate radioactive ion beams in nuclear physics.

In 1983 he received the "Prix Gegner of the Académie des Sciences, Paris," in 1987 the "Prix du CEA," and in 2001 the American Physical Society's Tom W. Bonner Prize in Nuclear Physics, shared with Claude Lyneis.A prize awarded by Pantechnik (a manufacturer of ECR sources) is named after him.He authored a book Electron Cyclotron Resonance Ion Sources and ECR Plasmas.

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