“Plasmas Reactivos a Baja Temperatura. Caracterización y Diagnostico”. Isabel Tanarro Dept. de...
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Transcript of “Plasmas Reactivos a Baja Temperatura. Caracterización y Diagnostico”. Isabel Tanarro Dept. de...
“Plasmas Reactivos a Baja Temperatura.
Caracterización y Diagnostico”.
Isabel Tanarro
Dept. de Física Molecular Inst. Estructura de la Materia (CSIC)
Serrano 123. Madrid. Spain [email protected]
CSIC, Madrid
3
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
4
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+
6
cargas libres (Ne)
partículas neutras (N) =
¿ DIFERENCIA PLASMA FRÍO - GAS IONIZADO ?
7
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
8
“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)
9
Te 33000 K (3 eV) ve = 106 m/s
Plasma Dimensions >> Debye LengthPlasma Frequency >> Collision Frequency
ne , Te
10
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)