Runaway electrons

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The term runaway electrons (RE) is used to denote electrons that undergo free fall acceleration into the realm of relativistic particles. REs may be classified as thermal (lower energy) or relativistic. The study of runaway electrons is thought to be fundamental to our understanding of High-Energy Atmospheric Physics. [1] They are also seen in tokamak fusion devices, where they can damage the reactors.

Contents

Lightning

Runaway electrons are the core element of the runaway breakdown based theory of lightning propagation. Since C.T.R. Wilson's work in 1925, [2] research has been conducted to study the possibility of runaway electrons, cosmic ray based or otherwise, initiating the processes required to generate lightning. [3]

Extraterrestrial Occurrence

Electron runaway based lightning may be occurring on the four giant planets in addition to Earth. Simulated studies predict runaway breakdown processes are likely to occur on these gaseous planets far more easily on earth, as the threshold for runaway breakdown to begin is far smaller. [4]

High Energy Plasma

The runaway electron phenomenon has been observed in high energy plasmas. They can pose a threat to machines and experiments in which these plasmas exist, including ITER. Several studies exist examining the properties of runaway electrons in these environments (tokamak), searching to better suppress the detrimental effects of these unwanted runaway electrons. [5] Recent measurements reveal higher-than-expected impurity ion diffusion in runaway electron plateaus, possibly due to turbulence. The choice between low and high atomic number (Z) gas injections for disruption mitigation techniques requires a better understanding of the impurity ion transport, as these ions may not completely mix at impact, affecting the prevention of runaway electron wall damage in large tokamak concepts, like ITER. [6]

Computer and Numerical Simulations

This highly complex phenomenon has proved difficult to model with traditional systems, but has been modelled in part with the world's most powerful supercomputer. [7] In addition, aspects of electron runaway have been simulated using the popular particle physics modelling module Geant4. [8]

Space Based Experiments

Related Research Articles

<span class="mw-page-title-main">Tokamak</span> Magnetic confinement device used to produce thermonuclear fusion power

A tokamak is a device which uses a powerful magnetic field generated by external magnets to confine plasma in the shape of an axially symmetrical torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. The tokamak concept is currently one of the leading candidates for a practical fusion reactor.

<span class="mw-page-title-main">Fusion power</span> Electricity generation through nuclear fusion

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. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved.

<span class="mw-page-title-main">T-15 (reactor)</span>

The T-15 is a Russian nuclear fusion research reactor located at the Kurchatov Institute, which is based on the (Soviet-invented) tokamak design. It was the first industrial prototype fusion reactor to use superconducting magnets to control the plasma. These enormous superconducting magnets confined the plasma the reactor produced, but failed to sustain it for more than just a few seconds. Despite not being immediately applicable, this new technological advancement proved to the USSR that they were on the right path. In the original shape, a toroidal chamber design, it had a major radius of 2.43 m and minor radius 0.7 m.

<span class="mw-page-title-main">Magnetic confinement fusion</span> Approach to controlled thermonuclear fusion using magnetic fields

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, along with inertial confinement fusion.

<span class="mw-page-title-main">Field-reversed configuration</span> Magnetic confinement fusion reactor

A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.

<span class="mw-page-title-main">Tokamak à configuration variable</span> Swiss research fusion reactor at the École Polytechnique Fédérale de Lausanne

The tokamak à configuration variable is an experimental tokamak located at the École Polytechnique Fédérale de Lausanne (EPFL) Swiss Plasma Center (SPC) in Lausanne, Switzerland. As the largest experimental facility of the Swiss Plasma Center, the TCV tokamak explores the physics of magnetic confinement fusion. It distinguishes itself from other tokamaks with its specialized plasma shaping capability, which can produce diverse plasma shapes without requiring hardware modifications.

Ion cyclotron resonance is a phenomenon related to the movement of ions in a magnetic field. It is used for accelerating ions in a cyclotron, and for measuring the masses of an ionized analyte in mass spectrometry, particularly with Fourier transform ion cyclotron resonance mass spectrometers. It can also be used to follow the kinetics of chemical reactions in a dilute gas mixture, provided these involve charged species.

The Tokamak de Fontenay-aux-Roses (TFR) was the first French tokamak, built in a research centre of the French Atomic Energy Commission (CEA) in Fontenay-aux-Roses, a commune in the southwestern suburbs of Paris. The project was spearheaded by Paul-Henri Rebut, and is sometimes jokingly referred to as the "Tokamak façon Rebut" – a pun on the name Rebut and the French word "rebut" meaning "rubbish".

Ignitor is the Italian name for a proposed tokamak device, developed by ENEA. The project was abandoned in 2022.

<span class="mw-page-title-main">Relativistic runaway electron avalanche</span>

A relativistic runaway electron avalanche (RREA) is an avalanche growth of a population of relativistic electrons driven through a material by an electric field. RREA has been hypothesized to be related to lightning initiation, terrestrial gamma-ray flashes, sprite lightning, and spark development. RREA is unique as it can occur at electric fields an order of magnitude lower than the dielectric strength of the material.

<span class="mw-page-title-main">Plasma-facing material</span>

In nuclear fusion power research, the plasma-facing material (PFM) is any material used to construct the plasma-facing components (PFC), those components exposed to the plasma within which nuclear fusion occurs, and particularly the material used for the lining the first wall or divertor region of the reactor vessel.

<span class="mw-page-title-main">Divertor</span> Magnetic confinement fusion device component

In magnetic confinement fusion, a divertor or diverted configuration is a magnetic field configuration of a tokamak or a stellarator which separates the confined plasma from the material surface of the device. The plasma particles which diffuse across the boundary of the confined region are diverted by the open, wall-intersecting magnetic field lines to wall structures which are called the divertor targets, usually remote from the confined plasma. The magnetic divertor extracts heat and ash produced by the fusion reaction, minimizes plasma contamination, and protects the surrounding walls from thermal and neutronic loads.

<span class="mw-page-title-main">Sibylle Günter</span> German physicist (born 1964)

Sibylle Günter is a German theoretical physicist researching tokamak plasmas. Since February 2011, she has headed the Max Planck Institute for Plasma Physics. In October 2015, she was elected a member of the Academia Europaea in recognition of her contribution to research.

<span class="mw-page-title-main">Tokamak sawtooth</span> Relaxation in the core of tokamak plasmas

A sawtooth is a relaxation that is commonly observed in the core of tokamak plasmas, first reported in 1974. The relaxations occur quasi-periodically and cause a sudden drop in the temperature and density in the center of the plasma. A soft-xray pinhole camera pointed toward the plasma core during sawtooth activity will produce a sawtooth-like signal. Sawteeth effectively limit the amplitude of the central current density. The Kadomtsev model of sawteeth is a classic example of magnetic reconnection. Other repeated relaxation oscillations occurring in tokamaks include the edge localized mode (ELM) which effectively limits the pressure gradient at the plasma edge and the fishbone instability which effectively limits the density and pressure of fast particles.

Jose A. Boedo is a Spanish plasma physicist and a researcher at University of California, San Diego. He was elected as a fellow of the American Physical Society in 2016 for "his ground-breaking contributions to the studies of plasma drifts and intermittent plasma transport in the peripheral region of tokamaks".

Hartmut Zohm is a German plasma physicist who is known for his work on the ASDEX Upgrade machine. He received the 2014 John Dawson Award and the 2016 Hannes Alfvén Prize for successfully demonstrating that neoclassical tearing modes in tokamaks can be stabilized by electron cyclotron resonance heating, which is an important design consideration for pushing the performance limit of the ITER.

The Dreicer field is the critical electric field above which electrons in a collisional plasma can be accelerated to become runaway electrons. It was named after Harry Dreicer who derived the expression in 1959 and expanded on the concept in 1960. The Dreicer field is an important parameter in the study of tokamaks to suppress runaway generation in nuclear fusion.

<span class="mw-page-title-main">Wendelstein 7-AS</span> Stellarator for plasma fusion experiments (1988-2002)

Wendelstein 7-AS was an experimental stellarator which was in operation from 1988 to 2002 by the Max Planck Institute for Plasma Physics (IPP) in Garching. It was the first of a new class of advanced stellarators with modular coils, designed with the goal of developing a nuclear fusion reactor to generate electricity.

<span class="mw-page-title-main">Tokamak Chauffage Alfvén Brésilien</span> Tokamak at the University of Sao Paulo, Brazil

The Tokamak Chauffage Alfvén Brésilien (TCABR) is a tokamak situated at the University of São Paulo (USP), Brazil. TCABR is the largest tokamak in the southern hemisphere and one of the magnetic-confinement devices committed to advancing scientific knowledge in fusion power.

References

  1. ↑ Dwyer, Joseph R.; Smith, David M.; Cummer, Steven A. (1 November 2012). "High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena". Space Science Reviews. 173 (1–4): 133–196. Bibcode:2012SSRv..173..133D. doi: 10.1007/s11214-012-9894-0 . ISSN   0038-6308.
  2. ↑ Wilson, C.T.R. (1925). "The acceleration of β-particles in strong electric fields such as those of thunderclouds". Proc. Cambridge Philos. Soc. 22 (4): 534–538. Bibcode:1925PCPS...22..534W. doi:10.1017/s0305004100003236. S2CID   121202128.
  3. ↑ Gurevich, A.v.; Milikh, G.m.; Roussel-Dupre, R. (1992). "Runaway Electron Mechanism of Air Breakdown and Preconditioning during a Thunderstorm". Physics Letters. 165.5 (5–6): 463. Bibcode:1992PhLA..165..463G. doi:10.1016/0375-9601(92)90348-p.
  4. ↑ Dwyer, J; Coleman, L; Lopez, R; Saleh, Z; Concha, D; Brown, M; Rassoul, H (2006). "Runaway Breakdown in the Jovian Atmospheres". Geophysical Research Letters. 33 (22): L22813. Bibcode:2006GeoRL..3322813D. doi: 10.1029/2006gl027633 .
  5. ↑ Reux, C.; Plyusnin, V.; Alper, B.; Alves, D.; Bazylev, B.; Belonohy, E.; Boboc, A.; Brezinsek, S.; Coffey, I.; Decker, J (2015-09-01). "Runaway electron beam generation and mitigation during disruptions at JET-ILW". Nuclear Fusion. 55 (9): 093013. Bibcode:2015NucFu..55i3013R. doi:10.1088/0029-5515/55/9/093013. hdl: 11858/00-001M-0000-0029-04D1-5 . ISSN   0029-5515. S2CID   92988022.
  6. ↑ Hollmann, E.M.; Bortolon, A.; Effenberg, F.; Eidietis, N.; Shiraki, D.; Bykov, I.; Chapman, B.E.; Chen, J.; Haskey, S.; Herfindal, J.; Lvovskiy, A.; Marini, C.; McLean, A.; O'Gorman, T.; Pandya, M.D.; Paz-Soldan, C.; Popović, Ž. (2022-02-02). "Dynamic measurement of impurity ion transport in runaway electron plateaus in DIII-D". Nuclear Fusion. 29 (2): 022503. Bibcode:2022PhPl...29b2503H. doi: 10.1063/5.0080385 . S2CID   246504822.
  7. ↑ Levko; Yatom; Vekselman; Glezier; Gurovich; Krasik (2012). "Numerical Simulations of Runaway Electron Generation in Pressurized Gases". Journal of Applied Physics. 111 (1): 013303–013303–9. arXiv: 1109.3537 . Bibcode:2012JAP...111a3303L. doi:10.1063/1.3675527. S2CID   119256027.
  8. ↑ Skeltved, Alexander Broberg; Østgaard, Nikolai; Carlson, Brant; Gjesteland, Thomas; Celestin, Sebastien (2014). "Modeling the relativistic runaway electron avalanche and the feedback mechanism with GEANT4". Journal of Geophysical Research: Space Physics. 119 (11): 9174–9191. arXiv: 1605.07771 . Bibcode:2014JGRA..119.9174S. doi:10.1002/2014JA020504. PMC   4497459 . PMID   26167437.
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