Dictionary of Material Science and High Energy Physics Part 13 doc

The value of the magnetic field at which this happens is called the critical magnetic field.There are two types of superconductors.One, in which the quenching occurs discontin-uously fir

subsonic flow Flow in which the local Mach

number is less than unity The governing

differ-ential equations in subsonic flow are elliptic

substitutional defects Defects arising out of

substitution of some atoms in a crystal by atoms

of a different element although the basic

struc-ture remains the same

Sudbury neutrino observatory (SNO) The

first detector capable of distinguishing electron

neutrinos from muon or tauon neutrinos The

detector contains 1000 T of heavy water (D2O)

surrounded by 9500 photo multiplier tubes

Us-ing heavy water gives an advantage over

us-ing ordinary water (Kamioka detector) because

deuteron in heavy water is sensitive to the

neu-tral current reaction:

ν e + d → p + n + ν e

A neutron realized in this reaction can be

cap-tured by another nucleus through a (n, γ )

reac-tion A scintillation counter can detect γ quanta.

The minimum neutrino energy to activate this

reaction is 2.22 MeV

sum-frequency generation When two laser

beams of frequencies ω1and ω2are incident on a

non-linear material, a new beam with frequency

ωsum = ω1 + ω2is generated This occurs via

simultaneous absorption of an incident photon

from each field followed by emission of a photon

at the sum-frequency

summing over histories Richard Feynman

devised this method This method of string

the-ories has been fully developed by Stanley

Man-delstam and Alexandar Polyakov

sum rule A formula which establishes the

equality between some quantity or expression

to the sum over all states of another quantity

The most prominent example is the Thomas–

Reiche–Kuhn sum rule

sunspots Magnetic regions roughly the same

diameter as the earth which appear as dark spots

on the surface of the sun and can last anywhere

from a few days to several weeks in the case

of the larger ones The temperature at the

cen-ter of a sunspot is about 4500 K, whereas the

photosphere is normally 6000 K The number

of sunspots varies cyclically with an 11 year

pe-riod related to the solar magnetic cycle During

the sunspot cycle, the activity ranges from no

sunspots near the time of minimum activity to

hundreds near the time of maximum activity

superallowedβ− decay A special class of

beta decay when the initial nuclear state is J i π =

of a collision has to be 40 TeV

superconductivity A state of matter wherethe conductance of the matter is infinite at DC

voltages Superconductivity was discovered in

1911 by H Kammerling Onnes, who found thatcertain elements like mercury, lead, and tin ap-peared to lose all electrical resistance when theywere cooled below a certain temperature called

the transition temperature Superconductivity is

characterized by zero DC resistance and fect diamagnetism The latter means that notonly does a superconductor exclude all mag-netic flux, but as a material in the normal state iscooled to below the transition temperature, anytrapped flux is expelled This latter phenom-enon is called the Meissner effect The exis-tence of this effect implies that at high enoughmagnetic fields, when the superconductor is nolonger able to expel the flux, the flux will pene-

per-trate the material and quench the

superconduc-tivity The value of the magnetic field at which

this happens is called the critical magnetic field.There are two types of superconductors.One, in which the quenching occurs discontin-uously (first order phase transition), is called atype I superconductor (such as mercury) Thenthere are those where the quenching occurs con-tinuously and the phase transition is of secondorder These are called type II superconductors.Flux starts to penetrate a type II superconductor

at a critical field H c1 Flux tubes penetrate the

sample, each carrying a quantum of flux h/2e, where h is Planck’s constant and e is the elec-

tron charge This is called the Shubnikov phase

Then finally, at another critical field H c2, the flux

density in the material B reaches the value µH

(µ = magnetic permeability in the normal state

and H = applied magnetic field) At this point,

the superconductivity is completely quenched.

Superconductors are also classified into low

Tc and high Tc superconductors The latter

were discovered in 1986 by Bednorz and Müller

They are of type II and have a much higher

tran-sition temperature (Tc) than the low Tc type

The best known example is

yttrium-barium-copper-oxide (Y1Ba2Cu3O7−δ) with a transition

temperature of around 92 K

The phenomenon of superconductivity is

ex-plained by the Bardeen–Cooper–Schrieffer

the-ory, which postulates that two electrons (or

holes) of like charge develop an attraction

(over-coming the Coulomb repulsion) as a result of the

intercession of a third entity such as a phonon

These Cooper pairs carry current without

resis-tance (or dissipation) Low Tcsuperconductors

are amply described by this theory and it is not

clear if high Tcsuperconductors can also be

de-scribed by the same theory

superconductors Substances exhibiting the

rather unusual property of very low or negligible

resistance to the flow of electric current below

a certain temperature, the latter being known as

the critical temperature These substances

in-clude various alloys or compounds or metals and

are repelled by magnetic fields The critical

tem-perature depends on the type of the substance

supercritical field In heavy ion collisions it

is possible to compound a nucleus with Z higher

than Z critical (137) As result of this a

super-critical field is created.

superdeformation (nuclei) For stable

nu-clei, departure from the equilibrium spherical

form is generally small in the ground state

Extremely large deformations from spherical

shape are called superdeformations and they are

observed in excited configurations of medium

weight nuclei produced by the fusion of two

heavy ions in one In this process, the

forma-tion of superdeformed bands (states with high

values of J ) is observed An example is the

100Mo (36S, 4n)132Ce reaction In this

reac-tion, a 155 MeV36Sbeam is used on a target

of100Mo Superdeformed bands in132Ceare

formed Deformed nuclei de-excite through theemission of gamma rays

superelastic collision A collision between

a nucleus (or an atom) in an excited state and

a nucleon (electron) in which the target systemreturns to the ground state and almost the entireexcitation energy is transferred to the projectile

superexchange A mechanism involving change interaction between two ions of an anti-ferromagnetic substance where two other ions

ex-of a different material, most commonly oxygen,play an intermediate role by forming coupleswith their spins resulting in the final couplingbetween the original ions through these oppo-site spins

Superfish A particular computer programfor computing various field parameters of ac-celerators such as induced voltages in acceler-ator rf cavities, mode frequencies, and shuntimpedances for accelerating fields in resonant

rf cavities (accelerator cavity losses depend on

shunt impedance) See also more sophisticated

MAFIA computer program

superfluorescence Also known as Dicke perradiance It is a superradiant process where

su-N atoms are placed in an excited state and arespatially within one wavelength of one another.They may then radiate collectively, with a radi-

ation rate proportional to N2rather than N

supergravity The gauge theory of gravitation

is the supergravity theory Einstein’s theory of

gravity does not itself lend to quantization lem divergences) Divergences are common inquantum theory of fields, but a renormalization

(prob-procedure fails to solve this problem

Super-gravity theory has better divergence behavior.

superheavy elements The heaviest closeshell nucleus known is 208P b(Z = 82, N = 126) Z= 114 and 126 are strongly stabilized

by shell effects So far, Z = 112, and A = 277

are identified The quest is continuing for

ele-ments with Z > 112 and N ∼ 184 The element

Z = 112, N = 165(A = 277) was created in

Gesellschaft Fur Schwerionjenforschung lab in

Darmstadt, Germany using a beam of Zn on

a target of 208P b82

superkamiokande A massive 50,000 T

high-purity water Cernikov detector in a

Japanese mine in Kamioka This detector uses

Cernikov radiation to detect solar neutrinos A

neutrino scattered by a charged particle will

pro-duce recoil and Cernikov light For low energy

neutrinos (coming from sun hydrogen burning),

only scattering with electrons can produce such

radiation (neutrinos with energy comparable to

the electron rest mass energy of 0.5 MeV in

a process of electron scattering can produce

Cernikov light)

superlattice (1) Artificially periodically

structured materials proposed by Tsu in 1969 A

periodic variation of the composition of a

ma-terial or the doping profile leads to a tunable

periodicity The introduction of the superlattice

perturbs the bandstructure of the host materials,

yielding a series of narrow sub-bands and

for-bidden gaps

(2) Alternating layers of two different

ma-terials A and B result in a compositional

su-perlattice structure The structure has an

addi-tional spatial periodicity along the direction of

alternation, over and above the inherent

period-icity of the atomic lattice This periodperiod-icity can

be achieved by either compositional modulation

or doping modulation in the case of a

semicon-ductor In the latter (called doping superlattices

or n–i–p–i structures), the doping is alternated

between n- and p-types The resulting changes

in the conduction and valence band profiles

re-sults in a periodic modulation of the potential

energy seen by an electron or hole

Compositional superlattices can be of four

types depending on the relative alignments of the

conduction and valence band edges Note that

type 2A superlattices result in semiconductors

that are indirect gap in real space

supermultiplet Multiplet comprising greater

than three lines

supernova Supernovas have a special role in

the formation of matter because heavy elements

are created in their explosions In supernova

explosions, shock waves created by a

collaps-ing star core rebound and create ideal tions for endothermic creation of elements be-

condi-yond A∼ 56 In very massive stars (20-30 solarmass) under huge gravitational attraction col-lapse of stars becomes to collapse making hugeexplosion and ejecting matter in space The rest

of the supernova is a neutron star or black hole The mass of a supernova before explosion

(Fowler, W.A and Hoyle, F Nucleosynthesis

in massive stars and supernovae, AstrophysicsJournal Supplement Series, 91, 201, 1964) is57% 16O rich mantle and the outer shell of 33%

of H and 4H e Under the influence of shock

waves, different heavy ion reactions can happen,For example, 16O+16O→28Si+4H e28Si+

28Si→56N i + γ

The shock waves convert hydrogen into lium and helium into oxygen Coulomb barriersfor elements beyond nickel and iron are highbecause of a large number of protons Most ob-served capturing neutrons make heavy elements.This process makes nuclei richer in neutrons fol-lowed by beta decay that keeps the formation inlimits of valleys of stability

he-supernova neutrinos Radiation of energy

can take place in the formation of supernovas inseveral ways Kinetic energy of matter ejected

in space, gamma rays, positrons, and electronneutrinos are produced Neutrinos and antineu-trinos are produced in the process of annihila-tion of positrons and electrons Another chan-nel for this annihilation is the production of twogammas Gammas have to brake through thickstellar mass and they are absorbed inside

super-Poissonian statistics A typical

pho-ton counting experiment will measure a certain

number of photons in time T This is repeated

over and over again until the statistical tion of the number of photons detected in time

distribu-T is built up, P (n, T ) For coherent light, this

distribution can be calculated to be a Poissonian

distribution, where the standard deviation n is

equal to the square root of the mean photon ber

num-light, this distribution can be super-Poissonian

(n≥√ularly spaced sequence of photons See also

photon bunching

Four different types of superlattices.

superposition of states The most general

so-lution to the Schrödinger equation (or any

lin-ear differential equation) is a linlin-ear sum of all

possible solutions (|n), weighed by coefficients

(C n) that are determinable from initial

condi-tions, |ψ =∞n=0 C n |n Generally one uses

eigenstates of any Hermitian operator These

eigenstates form a complete orthonormal basis

set

superposition principle States that the most

general solution to a linear differential equation

is a superposition of all possible solutions

super proton synchrotron Started operating

at the peak energy of 400 GeV in 1976 at CERN

Fermilab has a more advanced version of thismachine

superradiance A high gain amplifier can

emit with no incident laser field via the process

of amplified spontaneous emission, or

superra-diance In this process, a photon emitted by one

atom molecule of the gain medium is then plified via the process of stimulated emission

am-See also superfluorescence

supersonic flow Flow in which the localMach number is greater than unity The gov-

erning differential equations in supersonic flow

are hyperbolic For the perturbed velocity field

u = (u∞+u)i +vj+wk, a velocity potential

is defined such thatu = ∇ In the subsonic

and supersonic regimes,

supersymmetric theories In

supersymmet-ric theories is a symmetry that transforms

bosons and fermions into one another (unifies

particles with integer and half integer spins)

There are an equal number of bosons and

fermions for any given mass Gravity with

su-persymmetry gives supergravity theories A

graviton is a particle (spin 3/2) which is

respon-sible for supersymmetry in these theories For

every ordinary boson there is supersymetric spin

1/2 fermion Every particle has supersymmetric

particle identical except in spin (e.g., for a spin

1 photon, the supersymetric particle is 1/2 spin

photino; every boson has a spin 1/2

supersym-metric fermion) Supersymmetry explains why

at high energies, leptons, hadrons, and gauge

bosons have smaller masses than normal

superthermal electron, ion, or particle

Many plasmas may be viewed as consisting of

one or more bulk fluids in approximate

ther-mal equilibrium plus various non-therther-mal

com-ponents, such as resonantly accelerated

parti-cles or partiparti-cles injected from an outside source

When particles in some non-thermal component

have higher characteristic energies than those in

the thermal bulk plasma, the particles are said

to be superthermal For example, in intense

laser–plasma interactions, a laser impinging on a

near-solid density target can produce

superther-mal electrons via the ponderomotive force, as

well as a thermal blow-off plasma

supplementary condition The condition

that the state vector would behave as a state

surface acoustic wave Acoustic wave that

travels along the surface of a material These

usually decay rapidly into the bulk of the

mate-rial, and the characteristic length of the decay is

the wavelength Surface acoustic wave devices

are used in signal processing on a semiconductor

chip They are widely used in realizing tapped

delay lines which are the mainstay of transversal

filters

surface electromagnetic wave netic wave that travels along the surface of a ma-terial These usually decay rapidly into the bulk

Electromag-of the material, and the characteristic length Electromag-ofthe decay is the wavelength

surface gravity waves Non-dispersive wavesformed at the interface of a liquid and a gas.Solution of potential flow equations reveal thatthe wave frequency is

f = 2πgk tanh kH where k is the wave number and H is the fluid depth; the phase speed c = 2πf/k is

and for shallow water waves this becomes

c=gH

Note that in the former case the phase speed doesnot depend upon the fluid depth, and in the lat-ter case the phase speed is independent of wave-length, giving rise to the rarefaction phenomena

of beaching waves tending to align themselvesperpendicular to the shoreline Particle motion

in surface gravity waves are circular in nature.

surface phonon, plasmon, waves A flatvacuum–solid interface has solutions to theLaplace equation ∇2φ = 0 which propagatealong the interface and decay exponentiallyfrom that interface when the dielectric function

of the solid medium is equal to−1 Such waves

are known as surface waves For a dielectric, the condition ε = −1 is satisfied between the fre-quencies of the transverse and longitudinal op-tical phonon frequencies This frequency in be-

tween is associated with the surface phonon For

a metallic medium, this surface wave is called

surface plasmon.

surface states The states on the surface of asemiconductor to which electrons may be boundvery closely

surface tension Force acting at the interface

of two or more immiscible fluids caused by

in-termolecular attractive forces For an interface

of curvature of radius R, the surface tension σ

is proportional to the pressure jump across the

interface

σ =R

2p The change in pressure arises from the curvature

of the interface and the pressure on the convex

side of the interface is lower

surface waves Acoustic waves generated by

earthquakes These waves travel along a great

circle, from the epicenter of the quake, close

to the earth’s surface The plate on which the

wave travels determines the wavelength of these

waves, usually a fraction of the plate size

susceptibility The susceptibility χ is defined

by P = 0 χ  E, where  P is the polarization

in-duced in a material under the influence of an

ex-ternal field E In general, the susceptibility is a

tensor It is scalar constant for a linear, isotropic,

homogeneous material

Sussex potential A special form of nuclei

ef-fective interaction that includes many-body

cor-relations in Hartree–Fock nuclear structure

com-putations Sussex potential is not written in a

functional form, but as a numerical description

of the nucleon-nucleon interaction in the form

of matrix elements in a basis of wave functions

of shell model

Sweet–Parker model An early theory for

magnetic reconnection, proposed by Sweet

(1958) and Parker (1963), in which plasma flows

into a region where two sheets of

oppositely-directed field lines are reconnecting (a resistive

magnetohydrodynamics process); the magnetic

energy released in the reconnection process is

transferred to the plasma and expels it outwards

perpendicular to the inflow direction This type

of reconnection process is a leading candidate

for understanding solar flares, and is also

im-portant in some types of laboratory plasmas

symmetric ordering An operator containing

products of creation and annihilation operators

is said to be symmetrically ordered if it is an

equal admixture of terms with all creation erators acting to the left and annihilation oper-

op-ators to the right For example, Asymmetric =

de-of space and solutions are unchanged we have

global symmetry in respect to that

characteris-tic If some specific characteristic can be tered independently in each point of space, one

al-can say that symmetry is local For example,

in-variant to three space rotations, (O(3) group) is acontinuous group and gives the conservation of

angular momentum Much symmetry is not

re-lated to ordinary space, but some internal space

It can be rotation in U(1) group gives vation of charge in Maxwell’s electromagnetictheory Specific very important type of sym-metries is gauge symmetries In these types of

conser-symmetries, an independent transformation can

be done in each point of time and space

Sym-metries can be broken, i.e., for some direction in

internal space a new phenomena can arise romagnetism at some specific temperature) Forexample, a group of symmetry for electroweakinteraction is SU(2)xU(1) At ordinary temper-atures we observe two different forces (electro-magnetic and weak), but at temperatures beyond

(fer-1015 degrees C there is no difference betweenthese two forces Similarly, at temperatures be-tween 1030 and 1032 C, grand unified theory(SU(5); SO(10) or E6 )are on scene (unifica-tion of electromagnetic, weak, strong interac-tions) At these temperatures (1030 and 1032C), the effects of quantum gravity becomes im-portant These temperatures were present be-tween 10−43 and 10−38 seconds after the BigBang Many grand unification theories incorpo-

rate supersymmetry (symmetry between bosons

and fermions) Recent attempts include stein’s theory of gravity

Ein-symmetry group A group of particles thatexhibits symmetry on a plot of the differencebetween the average charge of the group and thecharge of an individual particle vs hypercharge

symmetry scars New observed phenomena

in highly excited states of a nucleus This

phe-nomenon represents order in chaos

SYNCH (also TRANSPORT, COMFORT,

MAD) Special computer programs for

peri-odic lattice accelerator design used to compute

phase-space matching accelerator sections

synchrocyclotron Cyclotron (cyclic

accel-erator) type of accelerator To accelerate a

par-ticle to high energies, relativistic effects have

to be taken into account Resonant relativistic

relations require that the frequency of the RF

field has to be decreased or the magnetic field

increased (or both) as the velocity of particles

approaches the speed of light (v → c)

Machines in which the magnetic field is

con-stant, but with frequencies that are varied, are

called synchrocyclotrons Machines in which

the magnetic field is changed (irrespectively of

frequency) are called synchrotrons In electron

synchrotrons, frequency is kept constant; in

pro-ton synchrotrons both are varied

Synchrotrons in the GeV range of energies

have positioned magnets in the form of a ring

In some places of the ring, there are RF cavities

that accelerate particles

synchrotron radiation (1) Also known as

cyclotron radiation, synchrotron radiation is

emitted by charged particles whose trajectoriesare curved by magnetic fields, since the accel-eration required to curve the particle’s motionleads to the emission of electromagnetic radia-

tion A number of synchrotron radiation sources

are presently in operation, using electron ticle beams traveling through electron storagerings to provide X-ray light sources for variousresearch applications

par-(2) Moving in close synchrotron loops,

charged particles emit intensive beams of traviolet and X-rays This loss of energymust be compensated for by additional radio-frequency power in a synchrotron This is a se-rious problem in the construction of large syn-chrotrons, when small beams of magnetic fieldsbecome large These losses are known as beam-strahlung These losses are the fourth power ofbeam energy for a given radius (10 GeV acceler-ator problem) This radiation is a valuable toolfor biological and materials studies These arethe most intensive resource of X-rays and ultra-violet light

ul-synchrotrons See synchrocyclotron

T1 The lifetime, or inverse decay rate, of the

population inversion of a two-level atom Also

known as γ
In the radiatively broadened case,

we have T1 = 2T2.

T2 The inverse decay rate of the induced

dipole moment of a two-level atom Also known

as γ⊥ In general 1/T1 = 1/2T2 + 1/Tdephase.

tachyon A hypothetical particle that travels

faster than light

Tamm–Dancoff approximation An

approx-imate way of solving the Schrödinger equation

for a system of many interacting particles

(elec-trons or nucleons) by including states close in

energy through nonperturbative methods and

more remote excitations through perturbation

theory

Tamm–Dancoff method A method of

ap-proximation to the wave function of an

interact-ing particle system by considerinteract-ing

superposi-tion of several possible states, the latter number

determining the degree of approximation being

considered

Tamm surface states In 1932, Tamm

demonstrated the existence of surface states of a

special type near the surface of a crystal James

suggested that similar states could also exist near

an interface between two different materials An

interface, like a surface, is a strong perturbation

because of the discontinuity of the parameters of

the material The energy of such localized states

can lie in both allowed and forbidden bands of

the bulk dispersion relation In the latter case,

states localized at an interface will manifest as

donor or acceptor impurities

tandem accelerators At Fermilab, two

pro-ton accelerators occupy a single tunnel (see

Teva-tron collider) The second one is proton

syn-chrotron

targeted radiotherapy A method in

radio-therapy of cancer that selectively exposes cancercells using radionuclides conjugated to tumorseeking molecules Radionuclides in use in thismethod are beta, alpha, or Auger electron emit-ters (example, 90Y, 131Y, 199 Au, 212 Bi, 125

I, etc.)

tau (τ−) Named after the Greek word τριτ oυ

(third), it is the third charged lepton (after theelectron and muon)

Heavy leptons, tau and antitau, have charges

equal to −1, and masses of 1784 MeV Theirlife-time is less than 510−12 s The antipar-

ticle is antitau (τ+) and decays through weakinteraction into electrons, muons, or other parti-cles according to the Wainberg–Salam theory ofweak interactions For example, by weak inter-action, tau lepton can decay to a tau neutrino and

W− boson A W− boson decays into a negativemuon and a muon antineutrino

tauon neutrino Has a mass of less than 164

MeV and a charge of zero They are not served directly

ob-Taylor column Column of fluid above a body

in a rotating frame that appears to the ing flow as an extension of the body and ef-fectively acts as a solid boundary See Taylor–

as discrete vortical bands and can be laminar orturbulent

Taylor–Görtler vortices Counter-rotatingtoroidal vortices encountered along in a bound-ary layer along a concave wall

Taylor hypothesis Assumption that ations at a single point in a turbulent flow arecaused by the advection of a frozen turbulentflow field past that point Essentially, a temporal

fluctu-measurement of a quantity q(t ) is transformed to

thermal reservoir When one couples a

quan-tum system to its environment, and that

environ-ment is in thermal equilibrium at some

temper-ature, one can assume that the large system (the

reservoir, or environment) is unaffected by the

actions of the small quantum system and use

appropriate statistics to specify the state of the

environment at all times

thermionic emission The phenomenon of

electron or hole emission over a potential

bar-rier at a finite temperature Such a barbar-rier may

exist at the interface of a metal and an

insu-lator The current density J associated with

thermionic emission is given by the Richardson–

Dushman law:

J = − qm

2π2 ¯h3 (kT )2e −W/kT where q is the charge of an electron (or hole),

T is the absolute temperature, k is the

Boltz-mann constant, and W is the work function of

the metal Thus, if ln(J /T 2) is plotted against

1/kT , the resulting curve will be a straight line

with a slope of -W Such a plot is used to

ex-perimentally measure the work function W

thermodynamic equilibrium, plasma

There is a very general result from statistical

me-chanics which states that, if a system is in

ther-modynamic equilibrium with another (or

sev-eral other) system(s), all processes by which

the systems can exchange energy must be

ex-actly balanced by their reverse processes so that

there is no net exchange of energy For plasmas

in thermodynamic equilibrium, one can view

the plasma as an ion and electron system, and

one sees that ionization must be balanced by

recombination, Bremsstrahlung by absorption,

line radiation by line absorption, etc When

thermodynamic equilibrium exists, the

distribu-tion funcdistribu-tion of particle energies and excited

en-ergy levels of the atoms can be obtained from

the Maxwell–Boltzmann distribution, which is

a function only of the temperature The Saha

equation is a special application of this Because

thermodynamic equilibrium is rarely achieved,

especially in short-lived laboratory plasmas, one

must generally also consider deviations from

to-tal equilibrium, leading to more complicated

sit-uations

thermoelectric Materials that transport

elec-tricity efficiently while transporting heat not as

efficiently The figure of merit for a

thermoelec-tric material is a dimensionless quantity defined

as

ZT = S2σ T

κ where S is the Seebeck coefficient, σ is the elec- trical conductivity, κ is the thermal conductivity, and T is the absolute temperature.

thermoelectric effects The effect by which

heat energy is converted directly into electricalenergy and vice versa

thermoluminescence The process of

ther-mally releasing electrons (holes), trapped in calized states, which gives rise to photolumi-nescence upon subsequent recombination withholes (electrons) These electrons (holes) canoften also be observed in electrical transport(thermally stimulated currents) The intriguingfact about the process is that a very small quan-tum energy (thermal, 25 meV at room tempera-ture) is needed to produce emission of photons

lo-of several eV Thermoluminescence applications

has in dosimetry and as an infrared beam finder

thermomagnetic effects Thermoelectric fects occurring in presence of magnetic field

ef-See thermoelectric effect

thermonuclear In nuclear physics, relating

to processes which initialize the fusion of lightnuclei because of their rapid motion at extremelyhigh temperatures, leading to the release of fu-sion energy

thermonuclear fusion (1) Describes fusion

reactions achieved by heating the fuel into theplasma state to the point where ions have suf-ficient energy to fuse when they collide, typi-cally requiring temperatures of at least 1 mil-

lion K Thermonuclear fusion converts a small

amount of the mass of the reactants into energy

via E = mc2, and is the process by which mosttypes of stars (including the sun) produce the en-ergy to shine In these stars, gravity compressesand heats the core stellar plasma until the powerreleased from fusion balances the power radi-ated from the star; the star then reaches an equi-

librium where thermonuclear fusion reactions

sustain the internal pressure of the star in

bal-ance against the force of gravity This prevents

the star from collapsing, at least until it runs out

of fusion fuel On earth, controlled

thermonu-clear fusion reactions represent a possible

long-term source of energy for humanity, though

re-search remains decades away from economical

fusion power Uncontrolled fusion provides the

immense power of thermonuclear weapons

(hy-drogen bombs) In controlled fusion research,

the term thermonuclear is also used to

charac-terize fusion reactions between thermal ions, as

opposed to fusion reactions involving injected

beam ions or other ions lying outside the

ther-mal Maxwellian distribution

(2) A process in which two nuclei interact

and form a heavier nucleus An example of this

kind of reaction is a process that is investigated

in fusion reactors See tokamak

thermonuclear reaction An exoenergetic

nuclear reaction in which the nuclei of light

el-ements in a gas at a very high temperature

be-come energetic enough to combine with each

other upon collision

theta particle (meson) Discovered in the

Crystal Ball collaboration among products of

decay of psi particles Ii has a mass of 1640

MeV and an angular moment of two This

par-ticle could have double meson states (composed

of two quarks and two antiquarks) or gluonium

states

theta pinch or thetatron A fast-pulsed pinch

device in which an externally imposed current

goes in the azimuthal/circumferential direction

(generally in a solenoid) around a cylindrical

plasma Use of a fast-rising solenoidal current

causes a rapidly increasing axial magnetic field

which compresses and heats the plasma

thin airfoil theory Linearized supersonic

flow utilizating perturbations For the perturbed

velocity fieldu = (u∞+ u)i + vj+ wk, a

ve-locity potential  is defined such that u = ∇.

In the transonic regime,

−2u

u∞ and v = u∞θ, compressible corrections

such as the subsonic Prandtl–Glauert rule,

where α is the angle of attack of the thin airfoil.

third order susceptibility The susceptibilitydefined by P = 0 χ  Eoften has a dependence

on the applied field It is often useful to use

a Taylor series expansion of the susceptibility

in powers of the applied field For an isotropic

homogeneous material, this yields χ = χ ( 1)+

χ ( 2) E + χ ( 3) E2 The factor χ ( 3)is referred to

as the third order susceptibility, as it results in a

term in the polarization third order in the appliedfield This factor is only nonzero for materialswith no inversion symmetry For a material that

is not isotropic, the third order susceptibility is

a tensor

thixotropic fluid Non-Newtonian fluid inwhich the apparent viscosity decreases in timeunder a constant applied shear stress

Thomas–Fermi equation A differentialequation to calculate the electrostatic potential

in the context of the Thomas-Fermi atom model:

d2φ/ dr2 = φ 3/2 /r 1/2, with boundary

condi-tions φ (0) = 1 and φ(∞) = 0.

Thomas–Fermi theory A generalization of

Fermi-gas model in collective models of nuclear

matter In the Thomas–Fermi model,

single-particle wave function is replaced by plane wave

locally

Thomas Jefferson National Accelerator

Fa-cility Has CEBAF (Continuous Electron

Beam Accelerator Facility) This facility can

ex-aminate nuclei at scales smaller than the size of

nucleons as research of quark-gluon degrees of

freedom in nuclei, and electromagnetic response

of nuclei [the first continuous beam electron

ac-celerator at multi GeV energies (1-6 Gev)]

Thomas–Reiche–Kuhn sum rule This is an

identity involving the transition matrix elements

of an atom,

i ω ij |i|d|j |2= 3¯he2/2m Here,

e and m are the charge and mass of an

elec-tron and ω ijis the frequency difference between

states|i and |j The dipole moment operator

is d = er.

Thomson effect The electricity generated in

a single conductor, in the form of an emf, by

maintaining a thermal gradient in it Heating

and/or cooling effect can then be produced by

adjusting the flow of current along the thermal

gradient

Thomson scattering Scattering of

electro-magnetic radiation by free (or loosely bound)

particles

t’Hooft, Gerard Physicist from the

Univer-sity of Utrecht who notably contributed to the

theory of electroweak forces, QED, gauge

the-ories, etc and won the Nobel Prize in physics

Thouless number The conductance of a

sol-id divsol-ided by the fundamental conductance 2

e2/ h (e is the electronic charge and h is Planck’s

constant) is a dimensionless number called the

Thouless number It occurs in the theory of

lo-calization

three-body problem In quantum

mechan-ics, the problem of solving the equation of

mo-tion of three interacting quantum particles Theproblem has no exact solution except for certainunphysical interactions

three-body recombination In this atomicprocess occurring in relatively high density plas-mas, two electrons (or an ion and an electron)interacting near an ion result in a recombination

of one electron onto the ion, with the third ticle carrying away the resulting energy Thisprocess is the inverse of impact ionization

par-three-j coefficients Expansion coefficientsthat occur when eigenfunctions of two individ-

ual angular momenta j1 and j2 are coupled toform eigenfunctions of the total angular momen-

tum J = j1 + j2 They are also called Wignerthree-j symbols and are closely related, but notidentical, to the Clebsch–Gordon coefficients

three-level atom An atom that interacts with

an electromagnetic field such that only three els have significant population

lev-three-wave mixing A process in which twolaser beams interact in a non-linear optical ma-terial, generating a third beam

threshold dose A hypothetical dose belowwhich ionizing radiation has no stochastic risk

of cancer induction Namely, below 0.1 Sv ofwhole body dose epidemiological studies havenot observed statistical significant increase inthe number of cancers (including leukemia).Extrapolation linear doses effects relationshipfrom medium dose region (0.1–0.4 Sv) to lowdose region (below 0.1 Sv, or according someauthors below 0.2 Sv) is scientifically unjusti-fied Moreover, some authors claim hormesis(beneficial) effect of ionizing radiation in lowdose range

threshold gain The gain at which a laserturns on, where the gain per pass is equal to theloss This is a well-defined concept for largelasers

thyristor A device made of semiconductorfor changing the direction of current in an elec-trical circuit