“Plasmas Reactivos a Baja Temperatura.

Caracterización y Diagnostico”.

Isabel Tanarro

Dept. de Física Molecular Inst. Estructura de la Materia (CSIC)

Serrano 123. Madrid. Spain itanarro@iem.cfmac.csic.es

CSIC, Madrid

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Plasma

“Materia gaseosa fuertemente ionizada, con igual número de cargas libres

positivas y negativas”

Estado de la materiamás abundante en el Universo.

99% en las estrellas y el espacio interestelar

Emisión de Luz

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LLightning

Solar core

Fusion reactor core

Aurora Plasma Nebula

Flame

Laser focus

Glow discharge

Solids, Liquids & Gases

Interplanetary space

Solar corona

Solar photosphere

Jupiter core

Si crystal

Fusion plasma edge

CLASIFICACIÓN de los PLASMAS

• Grado de Ionización

Plasmas débilmente ionizados ( Ne / N < 10 -3)

Plasmas con ionización media (10 -3 < Ne / N < 10-1)

Plasmas fuertemente ionizados (10 -1 < Ne / N)

• TemperaturaPlasmas Calientes : Te T N ,T N+

Plasmas Fríos : Te >> T N ,T N+

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cargas libres (Ne)

partículas neutras (N) =

¿ DIFERENCIA PLASMA FRÍO - GAS IONIZADO ?

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102 103 104 105

10-2 10-1 100 101Particle Energy (eV)

Temperature (ºK)

PLASMAS GASES

Collective Effects

Ne , Te

+

Glow discharges:

ne= 1010 cm-3, Te= 3 eV = 33000 K

D = 100 m

D ( m ) = 50 √ Te / ne

√0 k / e

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“Debye Length” (Shielding effect)

Fundamental Magnitudes of Plasmas

Plasma Dimensions >> Debye Length

Reflection vs. Transmission of EM Radiation

> P dielectric (transparent)

< P conductor (reflecting)

“Plasma Frequeny” (resonance frequency for collective e- oscillations)

P (Hz) = 9 √ ne (m-3)

e / √ 40 me

D P = √ kTe/me ve

Metals : ne = 1028 m-3 1015 Hz (UV)

Fusion Reactor: ne = 1019 m-3 1010 Hz (MW)

Ionosfere : ne = 109 m-3 105 Hz (radio)

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Te 33000 K (3 eV) ve = 106 m/s

Plasma Dimensions >> Debye LengthPlasma Frequency >> Collision Frequency

ne , Te

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Plasmas

•Collective Behaviour !!!

•Electro-Magnetic Forces >> Dynamic Forces

Gases

• Independent Particles • Energy Transfer by Individual Collisions

Gases vs. Plasmas

LLightning

Solar core

Fusion reactor core

Aurora Plasma Nebula

Flame

Laser focus

Glow discharge

Solids, Liquids & Gases

Interplanetary space

Solar corona

Solar photosphere

Jupiter core

Si crystal

Fusion plasma edge

UV

MW

Radio

1 Å10 nm

1 m

100 m 1 cm

102 103 104 105 106 107 108 109

107

109

1011

1013

1015

10-2 10-1 100 101 102 103 104 1051010

1015

1020

1025

1030

Ne

( m

- 3 )

E (eV)

T (K)

p (H

z)

LLightning

Solar core

Fusion reactor

Aurora Plasma Nebula

Flame

Laser focus

Glow discharge

Solids, Liquids & Gases

Interplanetary space

Solar corona

Solar photosphere

Jupiter core

Si crystal

1 cm

100 m

1 m

10 nm1 Å

e-

+_

Plasma production at Low Pressure in Electric Discharges

• Primary Ionization:

[Ne]0 (sea level) 103 cm-3

• Electron Multiplication• Secondary electron emission

Paschen Curve

Other processes:

Excitation of upper levels & de-excitation (light emission)

Dissociation of Precursors & Production of New Species

(Reactive Plasmas)

Sputtering & Etching (Physical or Chemical)

10-2 1021

1012

108

1016

T (eV)

N (cm-3)

ions inthe glow

electronscathode

ions

stable species

atoms & radicals

etchingproducts

Far from Equilibrium!!!

High Te 1 – 10 eV 104 – 105 K Low ionized plasmas ( 106)

Low energy transfer to the gas

Low TGAS 0.025 eV 300 K

Low Pressure, Glow Discharges (DC, RF, MW)