﻿

# Beta (plasma physics)

The beta of a plasma, symbolized by "β", is the ratio of the plasma pressure ("p" = "n" "k"B "T") to the magnetic pressure ("p"mag = "B"²/2"μ"0).

[ Wesson, J: "Tokamaks", 3rd edition page 115, Oxford University Press, 2004]

Beta is a parameter indicating the relative importance of kinetic to electromagnetic phenomena. In fusion power applications, beta can be thought of as an economic figure of merit. The magnetic field in a fusion device has technological limits such as the critical field of practical superconductors. The fusion power density, which determines the power output of a reactor, scales with the square of the plasma pressure. Therefore the output of a reactor can be said to scale with the square of the average beta. In a tokamak, for example, there is a fairly firm limit on the value beta can have before destructive instabilities occur.

Beta can also be thought of (very approximately) as an economic indicator of reactor efficiency. Since temperature (and therefore thermonuclear fusion power) scale like pressure, we can say that the numerator is roughly a measure of electricity generated. The costs of large magnets roughly scales like $B^\left\{1/2\right\}$. Therefore Beta can be thought of as a ratio of money in to money out for a reactor.

ee also

*Plasma

References

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• Beta — may refer to: *Beta (β), the second letter of the Greek alphabetIn finance: * Beta coefficient in Capital Asset Pricing ModelIn mathematics: * Beta function in mathematics * Beta distribution in statistics * False negative rate in statistics *… …   Wikipedia

• Plasma stability — An important field of plasma physics is the stability of the plasma. It usually only makes sense to analyze the stability of a plasma once it has been established that the plasma is in equilibrium. Equilibrium asks whether there are net forces… …   Wikipedia

• physics — /fiz iks/, n. (used with a sing. v.) the science that deals with matter, energy, motion, and force. [1580 90; see PHYSIC, ICS] * * * I Science that deals with the structure of matter and the interactions between the fundamental constituents of… …   Universalium

• plasma — plasmatic /plaz mat ik/, plasmic, adj. /plaz meuh/, n. 1. Anat., Physiol. the liquid part of blood or lymph, as distinguished from the suspended elements. 2. Cell Biol. cytoplasm. 3. whey. 4. a green, faintly translucent chalcedony. 5. Physics. a …   Universalium

• Plasma parameters — define various characteristics of a plasma, an electrically conductive collection of charged particles that responds collectively to electromagnetic forces. Plasma typically takes the form of neutral gas like clouds or charged ion beams, but may… …   Wikipedia

• Plasma scaling — The parameters of plasmas, including their spatial and temporal extent, vary by many orders of magnitude. Nevertheless, there are significant similarities in the behaviors of apparently disparate plasmas. It is not only of theoretical interest to …   Wikipedia

• Nuclear physics — For other uses, see Nuclear Physics (disambiguation). Nuclear physics Radioactive decay Nuclear fission Nuclear fusion …   Wikipedia

• Bremsstrahlung — produced by a high energy electron deflected in the electric field of an atomic nucleus Bremsstrahlung (German pronunciation: [ˈbʁɛmsˌʃtʁaːlʊŋ] ( …   Wikipedia

• Instabilité électrothermique — L instabilité électrothermique dite aussi instabilité de Velikhov ou instabilité d ionisation a été prédite par la théorie par le physicien russe Evgeny Velikhov en 1962, prédiction qui fut confirmée expérimentalement dès 1965. C est une… …   Wikipédia en Français

• Columbia School of Engineering and Applied Science — School of Engineering and Applied Science redirects here. For other uses, see School of Engineering and Applied Science (disambiguation). Fu Foundation School of Engineering and Applied Science Established …   Wikipedia