Vibrational Kinetics, electron dynamics and elementary processes in H2 and D2 Plasmas for Negative Ion Production: Modelling Aspects - PowerPoint PPT Presentation

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Vibrational Kinetics, electron dynamics and elementary processes in H2 and D2 Plasmas for Negative Ion Production: Modelling Aspects

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a) photodissociation of H2( ), D2( ), HD( ) and H2 ... c) H2( ) formation on graphite ... a) elementary gas-phase processes involving Caesium ... – PowerPoint PPT presentation

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Title: Vibrational Kinetics, electron dynamics and elementary processes in H2 and D2 Plasmas for Negative Ion Production: Modelling Aspects


1
ELEMENTARY PROCESSES, THERMODYNAMICS AND
TRANSPORT OF H2, O2 AND N2 PLASMAS
2
COLLABORATORs
3
OUTLINE
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
4
PHOTODISSOCIATION 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

5
MACROSCOPIC 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
6
HEAVY 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
7
H2(?) FROM RECOMBINATION
T 1,000 K
T 300 K
8
O2(?), N2(?) FROM RECOMBINATION
O2
N2
9
ATOMIC 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
10
HEAVY 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
11
COLLISION INTEGRALS for O-O and O-O INTERACTIONS
involving LOW-LYING EXCITED STATES SCHEME OF
CLASSICAL APPROACH
12
EFFECTIVE 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
13
A 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
14
PHENOMENOLOGICAL 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)
16
INELASTIC (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)
17
EFFECTIVE 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
18
OUTLINE
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
19
THERMODYNAMIC 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
20
Internal partition function
Internal specific heat
21
CONTRIBUTION TO SPECIFIC HEAT
Reactive Specific Heat
Frozen Specific Heat
internal state contribution
reaction contribution
22
HYDROGEN MIXTURE ISENTROPIC COEFFICIENT
Frozen
Total
23
TRANSPORT 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
24
EFFECT of DIFFERENT CUT-OFF CRITERIA on ATOMIC
HYDROGEN NUMBER DENSITY
GROUND-STATE
DEBYE-HUCKEL
CONFINED-ATOM
Trampedach et al. Astrophys. J. (2006)
25
COLLISION 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

27
EFFECT 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
28
EFFECT of DIFFERENT CUT-OFF CRITERIA on TRANSPORT
PROPERTIES of HYDROGEN PLASMA including ABNORMAL
TRANSPORT CROSS SECTIONs for EES
REACTIVE THERMAL CONDUCTIVITY
INTERNAL THERMAL CONDUCTIVITY
29
RF-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
30
EXPANSION 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)
31
EXTRACTION 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).
32
FUTURE 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
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