Title: Vibrational Kinetics, electron dynamics and elementary processes in H2 and D2 Plasmas for Negative Ion Production: Modelling Aspects
1ELEMENTARY PROCESSES, THERMODYNAMICS AND
TRANSPORT OF H2, O2 AND N2 PLASMAS
2COLLABORATORs
3OUTLINE
a) photodissociation of H2(?), D2(?), HD(?) and
H2(?) b) heavy particle collision cross
sections H2(?), D2(?) from recombination c)
H2(?) formation on graphite d) heavy particle
collision cross sections for O-O2 and N-N2
fitting relations d) collision integrals for O-O
and O-O interactions e) collision integrals for
N-N and N-N interactions a phenomenological
approach a) thermodynamic properties of
atomic hydrogen plasma b) transport properties
of atomic hydrogen plasma cut-off criteria c)
negative ion source modeling
4PHOTODISSOCIATION PROCESSES for H2(?), D2(?),
HD(?) and H2(?)
- LYMAN and WERNER SYSTEMS
- HIGH-ENERGY EXTRAPOLATION for STATE-DEPENDENT
CROSS SECTIONS - derivation of
- STATE-DEPENDENT PHOTODISSOCIATION RATE
COEFFICIENTS - MACROSCOPIC PHOTODISSOCIATION RATE COEFFICIENT
(ktot) - FITTING FORMULAS
5MACROSCOPIC PHOTODISSOCIATION RATE COEFFICINTS
for H2(?) and H2(?) COMPARISON with LITERATURE
H2(?) WERNER
H2(?) LYMAN
H2(?)
D.R.G. Schleicher et al. AstronomyAstrophysics
490 (2008) 521
6HEAVY PARTICLE COLLISIONS VIBRATIONALLY EXCITED
MOLECULES FROM RECOMBINATION
- QCT SIMULATION
- RECOMBINATION RATE COEFFICIENTs
- from QCT DISSOCIATION by DETAILED BALANCE
- THREE-BODY RECOMBINATION
-
- from RBC (Roberts, Bernstein Curtiss) THEORY
- TWO-STEP BINARY COLLISION
rotational barrier
quasi-bound state
7H2(?) FROM RECOMBINATION
T 1,000 K
T 300 K
8O2(?), N2(?) FROM RECOMBINATION
O2
N2
9ATOMIC RECOMBINATION on GRAPHITE SURFACE H2 (?,
j) NASCENT DISTRIBUTIONs
- SEMI-CLASSICAL MODEL
- ELEY-RIDEAL MECHANISM (H CHEMISORBED at the
SURFACE with a chemisorption well of 0.52eV ) - PROBABILITIES dependence on
- SURFACE TEMPERATURE
- IMPACT ENERGY
- ISOTOPES
vibrational distribution is obtained summing up
population of rotational levels
SURFACE TEMPERATURE500 K ENERGY 0.07 eV
M.RUTIGLIANO, M.CACCIATORE, CHEM.PHYS.CHEM. 9
(2008) 171
10HEAVY PARTICLE COLLISION CROSS SECTIONS for O-O2
and N-N2 SYSTEMS FITTING RELATIONS
- ACCURATE QCT CROSS SECTIONS for
- VIBRATIONAL DEACTIVATION VT processes
- DISSOCIATION
fitting bidimensional relations
EASY INCLUSION in KINETIC MODEL
30
?i30
20
10
?i40
RATE COEFFICIENT cm3s-1
RATE COEFFICIENT cm3s-1
?i0
?i46
TEMPERATURE
TEMPERATURE
F.ESPOSITO, I.ARMENISE, G.CAPITTA, M.CAPITELLI,
CHEM.PHYS 351 (2008) 91
11COLLISION INTEGRALS for O-O and O-O INTERACTIONS
involving LOW-LYING EXCITED STATES SCHEME OF
CLASSICAL APPROACH
12EFFECTIVE DIFFUSION-TYPE COLLISION INTEGRALS for
O-O INTERACTIONS involving LOW-LYING EXCITED
STATES ELASTIC CONTRIBUTION from POTENTIALS
and INELASTIC CONTRIBUTION from CHARGE-EXCHANGE
CROSS-SECTIONS
A.LARICCHIUTA, D.BRUNO, M.CAPITELLI, R.CELIBERTO,
C.GORSE, G.PINTUS, CHEM.PHYS.LETT. 344 (2008) 13
13A PHENOMENOLOGICAL MODEL for HEAVY PARTICLE
COLLISION INTEGRALS
PHENOMENOLOGICAL APPROACH AVERAGE INTERACTION
INTERACTION POTENTIAL
CLASSICAL COLLISION INTEGRALS
fitting formulas up to (4,4) order A.
LARICCHIUTA, G.COLONNA et al. Chemical Physics
Letters 445 (2007) 133
14PHENOMENOLOGICAL APPROACH
4
ION-NEUTRAL
6
NEUTRAL-NEUTRAL
hard interactions
soft interactions
15 COLLISION INTEGRALS COMPARISON between CLASSICAL
and PHENOMENOLOGICAL APPROACHES
phenomenological approach
LARICCHIUTA et al. (2008)
CAPITELLI et al. (1972)
16INELASTIC (CHARGE TRANSFER) DIFFUSION-TYPE
COLLISION INTEGRALs for N-N INTERACTIONs
involving HIGH-LYING EXCITED STATES
Dependence of diffusion-type collision integrals
for the interaction N(3P)-N on the principal
quantum number of the atom valence shell
electrons, n, at T10,000 K (different electronic
states of N, arising from the same electronic
configuration have been considered. n2 N(2p3
4S,2D,2P), n3 N(2p23s 2P,4P), n4 N(2p24s
2P,4P), n5 N(2p25s 2P,4P)
17EFFECTIVE DIFFUSION-TYPE COLLISION INTEGRALS for
N-N INTERACTIONS involving LOW-LYING EXCITED
STATES ELASTIC CONTRIBUTION from PHENOMENOLOGICAL
POTENTIALS and INELASTIC CONTRIBUTION from
CHARGE-EXCHANGE CROSS-SECTIONS
T 10,000 K
18OUTLINE
a) photodissociation of H2(?), D2(?), HD(?) and
H2(?) b) heavy particle collision cross
sections H2(?), D2(?) from recombination c)
H2(?) formation on graphite d) heavy particle
collision cross sections for O-O2 and N-N2
fitting relations d) collision integrals for O-O
and O-O interactions e) collision integrals for
N-N and N-N interactions a phenomenological
approach a) thermodynamic properties of
atomic hydrogen plasma b) transport properties
of atomic hydrogen plasma cut-off criteria c)
negative ion source modeling
19THERMODYNAMIC PROPERTIES for ATOMIC HYDROGEN
PLASMA
M. Capitelli, D. Giordano, G. Colonna The role of
Debye-Hückel electronic energy levels on the
thermodynamic properties of hydrogen plasmas
including isentropic coefficients Physics of
Plasmas 15(8) (2008) 082115
20Internal partition function
Internal specific heat
21CONTRIBUTION TO SPECIFIC HEAT
Reactive Specific Heat
Frozen Specific Heat
internal state contribution
reaction contribution
22HYDROGEN MIXTURE ISENTROPIC COEFFICIENT
Frozen
Total
23TRANSPORT PROPERTIES for ATOMIC HYDROGEN PLASMA
CUT-OFF CRITERIA
- GROUND STATE METHODS
- DEBYE HÜCKEL CRITERION
- CONFINED ATOM APPROXIMATION
internal energy 0
IN ANY CASE DRASTICALLY DECREASES INCREASING
PRESSURE or ELECTRON DENSITY!!!
particle density
24EFFECT of DIFFERENT CUT-OFF CRITERIA on ATOMIC
HYDROGEN NUMBER DENSITY
GROUND-STATE
DEBYE-HUCKEL
CONFINED-ATOM
Trampedach et al. Astrophys. J. (2006)
25COLLISION INTEGRALs for H(n)-H INTERACTIONs
compared with COULOMB COLLISION INTEGRALs
VISCOSITY-TYPE COLLISION INTEGRALS
DIFFUSION-TYPE COLLISION INTEGRALS
26- case USUAL EES considered as independent
chemical species BUT - EES collision integrals set equal to ground
state ones - case ABNORMAL EES considered as independent
chemical species with - their own collision integrals
27EFFECT of DIFFERENT CUT-OFF CRITERIA on TRANSPORT
PROPERTIES of HYDROGEN PLASMA including ABNORMAL
TRANSPORT CROSS SECTIONs for EES
HEAVY PARTICLE THERMAL CONDUCTIVITY
VISCOSITY
D. Bruno, M. Capitelli, C. Catalfamo, A.
Laricchiuta Physics of Plasmas (2008) in press
28EFFECT of DIFFERENT CUT-OFF CRITERIA on TRANSPORT
PROPERTIES of HYDROGEN PLASMA including ABNORMAL
TRANSPORT CROSS SECTIONs for EES
REACTIVE THERMAL CONDUCTIVITY
INTERNAL THERMAL CONDUCTIVITY
29RF-ICP NEGATIVE ION SOURCE
- 3 CRITICAL AREAS (remote source)
- Source chamber (driver)
- ICP (transformer) heating at high RF power
- No sheath losses
- Hot electrons
- Expansion region
- H2 vibrational excitation
- Extraction region
- Magnetic filtering
- Cold electrons
- H- production (surface/volume)
- Electron removal
Length 0.35 m
Radius 0.2 cm
Input Power 170 kW
Current coil 100 A
Frequency 1 MHz
Pressure 0.6 Pa
Max magnetic field 160 G
Extraction grid potential -20 kV
30EXPANSION REGION H2(?) EXCITATION
Boltzmann Tg VDF
H2(v) vibrational distribution function
H2(?) VIBRATIONAL DISTRIBUTION FUNCTION
() J. R. Hiskes et al., J. Appl. Phys. 53(5),
3469 (1982) () O. Fukumasa, K. Mutou, H.
Naitou, Rev. Sci. Instrum. 63(4), 2693 (1992)
31EXTRACTION REGION RESULTS PG BIAS EFFECT
transition from a classical sheath drop to a
complete reversed sheath
0 5 10 15 20
30 (cm)
PG
PLASMA GRID
DRIVER EXIT
TO THE DRIVER
EXTRACTION REGION
EXPANSION REGION
(a) U. Fantz, et al., Plasma Phys. Control. Fus.
49(12B), 563-580 (2007).
32FUTURE PERSPECTIVEs
a) elementary gas-phase processes involving
Caesium b) direct approaches for gas-phase
recombination c) H2(?) formation on caesiated
surfaces d) approaches for collision integral
calculation of highly excited states
interactions a) transport properties of
air plasma with electronically excited states b)
transport of radiation c) negative ion source
modeling improvements