1 CRYOPLASMA IN HELIUM INDUCED BY CORONA DISCHARGE N. Bonifaci , F. Aitken, G2Elab Grenoble, France V Atrazhev, Joint Institute for High Temperatures, Russia V.A. Shakhatov, Topchiev of Petrochemical Synthesis Institute, Russia J. Eloranta Department of Chemistry,California State University, USA K. von Haeften , Leicester University, Leicester, UK G Vermeulen, Institut Néel Grenoble, France
CRYOPLASMA IN HELIUM INDUCED BY CORONA DISCHARGE . N. Bonifaci , F. Aitken, G2E lab Grenoble, France V Atrazhev, Joint Institute for High Temperatures, Russia V.A. Shakhatov, Topchiev of Petrochemical Synthesis Institute, Russia - PowerPoint PPT Presentation
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CRYOPLASMA IN HELIUM INDUCED BY CORONA DISCHARGE
N. Bonifaci, F. Aitken, G2Elab Grenoble, France V Atrazhev, Joint Institute for High Temperatures, Russia
V.A. Shakhatov, Topchiev of Petrochemical Synthesis Institute, RussiaJ. Eloranta Department of Chemistry,California State University, USA
K. von Haeften , Leicester University, Leicester, UKG Vermeulen, Institut Néel Grenoble, France
2
Discharges in dense fluids (liquids or high-pressure gases :1-100 bar)
Motivation
2
Filamentary Streamers in Liquid N2
This process in dense fluids is very complex that involves
- electronic phenomena : electron injection, electron impact, excitation and ionization
- thermal phenomena: phase change
- hydrodynamic phenomena : formation of pressures waves, propagation of discharge channel.
Modeling
3
Cryoplasma in Helium
3
Discharge model in liquid model
µ-discharge Liquefied Helium
Condensed 4He
Interaction of atoms He*, molecules He2, and e- with helium in various thermodynamic phases and states
Gas liquid300k 4.2k
nanoscopic probes
44
Corona discharge in dense heliumLiquide
Light emission
Transport zone : E ~ kV/cm µe and µ+
Ionization zone : Ep~ MV/cm
Densities of the plasma particles (Ne and Np), Temperature, etc
4
Crucial importance for the modelling of plasmas produced by electric discharges
I ~ 0.1-50µA, DC V ~ kV
Applied power : 0.5-100mW
gap distance~mm
Rp ~ 0.1-0.2µm
Gas pressure ~ 1-100 bar
CCD Camera picture
55
Electronic mobility
Ntr1021cm-3
0 50 100 150 200 2500,01
0,1
1
10
100
(c
m2 /V
.s)
N(1020cm-3)
T=6K T=7K T=10K
e- bubble
Transition
5
Electrons in condensed 4He
e- repulses surrounding atoms He
Repulsive interaction
Free e-
Electron bubbles are formed by excess electrons in condensed He
6
Optical Spectroscopic Investigation
Discharge in helium supercriticalat 300 K and 150 K
Discharge in helium liquidat 4.2 - 5.1KIn helium supercritical T<12K
N ALLARD, et al EPL 88 (2009) 53002N ALLARD, et al EPJ D 61 (2011) 365-372
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Ionization zoneTransport zone
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NPlasma~ NNe 1015-1016cm-3
Tkinetic~ 300-320K
NT= 300 K
Nplasma and Tkinetic at T = 300 K
Discharge in helium gas at 300 K
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Discharge in liquid helium at 4.2 K
Discrepancy between the rotational temperature of He2(d3Su+-b3g)
and He2(D1Su+- B1g) Tkinetic
He2(d3Su+-b3g)
He2(D1Su+- B1g) Tr=700K
Tr=220K
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Discharge in liquid helium at 4.2 KShape of Line 706 nm in Liquid He at 4.2K.
685 690 695 700 705 710 715 720-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
Inte
nsity
l nm
P=0.1MPa P=0.6MPa P=1.6MPa P=3.5MPa
696 698 700 702 704 706 708 710 712 7140,0
0,2
0,4
0,6
0,8
1,0
Inte
nsity
l (nm)
P=0.5MPa P=1.3MPa P=2.6MPa P=4.7MPa P=5.7MPa
Strongly Blueshifted
Gas
300 K
706 nm line (3S-3P) observed
in liquid helium
symmetrical Gaussian profile
696 698 700 702 704 706 708 710 712 7140,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
Inte
nsity
l nm
P=1MPa N=2.40 1020
P=1.6MPa N=3.83 1020
P=2.4MPa N=5.73 1020
P=3.2MPa N=7.61 1020
P=3.9MPa N= 9.25 1020
P=5.9MPa N=1.38 1021
Gas
150 K
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New Autocorrelation function liquid helium
D
rdrtrVi
ei
fi
3
/1exp
is the liquid density in the electronic ground state around 3s calculated using Bosonic Density Functional Theory DFT
i
He*(3s)
Ab initio potentials of the excited state He(3 3S)-He
In Analogy to electron bubbleRepulsion between excited atom (Rydberg e-) and surrounding atoms in the ground state forms bubble Atomic bubble
He* fluorescence lines originate from outside the discharge region
Bulk helium
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Liquid density around He*(3s)
Bubble Radius Rb depends on applied pressure P.
Liquid density around 3s3S excited state calculated using Density Functional Theory (DFT) 1 bar
6 bar16 bar
LHe3s
35 bar
Empty cavity aroundexcited atom (radiator).
Bulkliquid
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706.5 nm He* line (3S-3P)
Experimental (continuous) vs theoretical (dashed)
wth≈wexp
e-+He ->He*+e-+heat
the increased local temperature
3s
Electron impact excitation
« Local heating »
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Shape of Line 706 nm in Fluid He at 11 K.
Fixed temperatures 11 K, different pressures, the increasing density.the line has symmetrical Gaussian profile with shift and width dependent on Pressure
He line 706,5nmLarge blue shiftGaussian Line ShapeThe line profile have been interpreted in terms of « bubble model » over extended temperature rangeHe* fluorescence lines originate from outside the discharge region