PNP_03_PE

hammercoupleMécanique

22 févr. 2014 (il y a 3 années et 6 mois)

201 vue(s)


1

Annual Moscow Workshop
“Physics of Nonideal Plasma”

(PNP

200
3
)


(
2
-
3

December 200
3
, Moscow,

Presidium RAS
)


ABSTRACTS


P
OSTER
S

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =


2

STABILITY OF NEGATIVE IONS NEAR THE SURFAC
E OF A SOLID


D. I. Zhukhovitskii
a,
*, W. F. Schmidt
b
, and E. Illenberger
b


a
Joint Institute for High Temperatures, Russian Academy of Sciences,

Izhorskaya ul. 13/19, Moscow, 125412 Russia

b
Institut für Physikalische und Theoretische Chemie, Freie Un
iversität Berlin D
-
14195,

Berlin, Germany

*e
-
mail:
dmrzh@orc.ru


Abstrac
t

Stationary states of molecular negative ions (anions) near the surface of a solid

are
investigated. The lone electron is assumed to interact with

a diatomic molecule and the

surface of
the solid. The energies of electron levels are determined by solving the 2D

Schrödinger equation. It
is shown that its stable solutions exist at distances from the surface

greater than some critical
distance, otherwi
se the electron is detached from the anion. In the

case of attraction between the
electron and the solid, the interaction potential between the

anion and the solid appears to have the
Lennard

Jones form and the ion is separated from

the surface by some equ
ilibrium distance.


3

ON PLASMA COUPLING AND TURBULENCE EFFECTS


AT DENSE PLASMA STOPPING


Yu. K. Kurilenkov
1

and G. Maynard
2


1
Institute for High Temperatures of Russian Academy of Sciences, 13/19 Izhorskaya Str., 125412 Moscow,
Russia (
ykur@online.ru

)

2
Laboratoire de Physique des Gaz et des Plasmas, UMR
-
8578, Bât. 210, Université Paris XI, F
-
91405 Orsay,
France


The problem of stopping power (SP) for projectile ions is addressed and analyzed in terms of
dielectric f
unction and dynamic collision frequency for moderately dense and strongly coupled
plasma (SCP). We concern the role of few aspects for calculation of stopping power for correlated
ensembles of particles and oscillators, in particular:

A) Consequent defini
tion and calculation of SCP dynamic collision frequency,

(k,

)
;

B) Effects of poorly defined (group) collective modes domain,
r
0




k
-
1



a,

appearing for non
-
Debye plasmas (
r
0



v
Te

/

pe
, a =(3/4


n
i

)
1/3
, k



wave number);

C) Transition from positi
ve to negative dispersion



/

k



0 (specifically low group velocity of
modes) at strong coupling (




1);

D) Excitation of collective modes up to suprathermal level (





therm
) at dense plasmas as a
target
(


= <E
2
>/8

nT
, E


the strength of plasma osc
illations fields)).


Quasilinear stopping of dense suprathermal (nonlinear) plasma targets under different level of
induced plasma turbulence is calculated. The force of suprathermal plasma oscillations on the
beam ions is mostly in the nature of increase
d frictional drag. The results obtained show the
possibility of essential increasing of low velocity anomalous (“turbulent”) stopping in comparison
with losses at equilibrium dense plasma targets (partially, in analogy with the anomalously low
dense plasma

conductivity and anomalous optical properties). The critical target plasma
parameters,
energy loss functions at different approximations,
synergism (or combination) of
different factors to influence the stopping as well as connection between stopping phen
omena, and
SCP optical and transport properties are discussed. Some of the experimental conditions to create
specific turbulent targets (laser produced plasmas,
dense pinched plasmas
, isochoric heating of
solid density matter, etc.) as well as related mole
cular dynamics simulations data are analyzed.



#
Short paper and references related are also in the
Proceedings of XXX European. Conference on Plasma
Physics and Controlled .Fusion, St
-
Petersburg, July 2003, http://eps2003.ioffe.ru/


4

REAL PROPERTIES

OF FORCED TRANSPORT AND HEATING DYNAMICS OF
ELECTRONS IN BOLTZMANN GAS OF ATOMS


I.A. Boriev


Institute for Energy Problems of Chemical Physics (Branch) RAS


Using concepts of statistical physics and kinetics a logical consistent approach to description
of
transport and heating dynamics for ensemble of electrons under the force of electric field in
disordered medium of elastically scattering atoms is developed [1]. The approach is based on
application of quantitative mutual relation between two elastic lo
ss processes for electron (its
energy and transport impulse) by means of number of total elastic collisions required for relaxation
of that impulse and provides relation of time reversible equations of dynamics with irreversible
equations of kinetics what
is necessary for study of open dissipative system.

It’s established from analysis of existent experimental data and easy confirmed by a priory
arguments based on properties of elastic scattering that for thermal electrons the number of such
collisions is
equal to ~16, but for heavily forced transport heated (10
2
-
10
3

times) electrons this
number diminishes till ~4 [1,2]. As shown this unavoidable heating of electrons due to their forced
transport in such medium is accomplished by significant axially symmetr
ic stretching of initially
isotropic electron velocity space along transport direction, what causes such reduction of collision
number. At stationary transport in strong field this phenomenon leads to ~3 times exceeding of
mean electron velocity in transpo
rt direction over that of in opposite one, signifying that mean
energy of such electrons differs (each other) ~9 times. It’s found that effective mass of electron
(with respect to its forced transport) depends on stretching extend of electron velocity spac
e and is
several orders higher than the mass of free electron, being only 4
-
16 times ( the number of required
total elastic collisions) less than the mass of scattering atom.


The results obtained show that conventional assumptions about entire loss of ele
ctron transport
impulse in each one total elastic collision and about practical isotropy of velocity space of forced
transport heated electrons in boltzmann gas of atoms are both erroneous.

The established fundamental phenomenon of stretching of electron
velocity space under the action
of external directing force, which undoubtedly is important for adequate description of collision
ionization in electric discharge plasma, is directly confirmed by existent experimental data for field
dependence of electron
drift velocity in liquid rare gases. The account of this phenomenon allows to
give at first time clear qualitative and quantitative explanations both of peculiar (with two breaks)
behavior of this dependence for logarithmic coordinates (as display of two b
ifurcations of quasi
-
stationary states of electron velocity space) and of long time known effects of saturation of electron
drift velocity in these media at strong fields and of its multiple increase at small addition of
molecular impurity [1
-
3].


1.

Boriev
I.A. “Explanation of saturation effect of excess electron drift velocity under strong
electric field in condensed rare gases” (in Russian) //
Khim.Fiz
., 2003, V. 22, P. 80.

2.

Boriev I.A.

“About reasons of increase of quasi
-
free electron drift velocity in liq
uid rare gases at
small addition of molecular impurities” (in Russian) //

Khim.Fiz
., 2003, V. 22, P. 103.

3.

Boriev I.A. “New features of forced transport and heating dynamics of quasi
-
free electrons
under electric field in dielectric medium”

30th EPS Confer
ence on Controlled Fusion and
Plasma Phys., St. Petersburg, 7
-
11 July 2003 ECA Vol.
27A
, P
-
2.185
(http://eps2003.ioffe.ru/PDFS/P2_185.PDF).


5

ENSEMBLES OF METASTABLE CLUSTERS COMPOSED OF ELEMENTS

WHICH DO NOT FORM THE CONDENSED MA
T
TER

IN NORMAL CONDITIONS


V.F.Elesin,
N.N.Degtyarenko
, N.V.Matveev, L.A.Openov, A.I.Podlivaev

Moscow Engineering Physics Institute (State University)


The purpose of this work was to study theoretically a possibility of formation of the nitrogen
and helium clusters and their ensemb
les, as well as an accumulation of high energy in the cluster
structures. The existence of such metastable systems is predicted. It is shown that they are capable
to accumulate the energy up to (2


10) eV/atom that greatly exceeds the energy of the famili
ar
chem
i
cal materials. The structure and energetics of the clusters are determined. The cluster stability
and the processes of the energy release are studied. It is shown that up to 100% of the accumulated
energy is released upon the decay of nitrogen and
helium systems. Contrary to the combustion
processes, the energy release is due to the fi
s
sion of clusters and their ensembles into isolated
molecules and/or atoms, suggesting the practical advantages. So, the cluster structures are
promising candidates fo
r the energy a
c
cumulation.


6

FOUR PHASES OF DEVELOPMENT OF AN ELECTRODELESS DISCHARGE

OF UNIPOLAR BREAKDOW
N OF GAS (
UBG) AND
NECESSITY OF THE NEW

WAY
OF LOOKING TO AN EXP
LANATION ON A NATURE

OF THE
DISCHARGES


A.I. Gerasimov, I.V.Gerasimov, A.K.Suhov, M.N.P
yrshev, A.N.Selyankin


Kostroma State Univ., Kostroma, Russia
.

e
-
mail
s
:

ellips@kmtn.ru
;
giv@ksu.kostroma.net


The phenomenology of the discharge of unipolar breakdown of g
as (UBG) [1
-
3] puts many
questions having the direct relation not only to mechanisms of discharges pro
c
esses, but also
touching the basic situation of the classical theory of
electricity
.

The discharge tube
of discharge
UBG
has only one covering
-

electrod
e (CE),

which is placed outside of one end of the long (

5
m
)
tube;

length of CE,
CE
l
5
,
0

m
. Parameters of di
s
charge UBG are:
frequency of the unipolar (one
sign) pulses potential on C
E,
1000
40


i
f
Hz
; amplitude of p
o
tential pulses,
i

=
0
.
7
0
.
2

kV
;
duration of the pulse of
i

,
10
2


i
t
s

;
radius of
the tube,
)
30
3
(


t
r
mm
; pressure of gas,

)
30
10
3
(
3




p
Torr
.

In experiments with UBG four phases of development of the discharge are observed. The
first phase


dark, not observable (inductions phase), when at presence of pu
lse pote
n
tial on coat
-

electrode (CE) some time (about 5 minutes [1,

2]) the discharge
-

the lumine
s
cence of gas
-

is
absent. The second phase


an appearance of area of a luminescence in vo
l
ume of gas d
i
rectly under
a surface CE. The third phase
-

an app
earance on some distance from CE of free volume
t
ric charges
(FVC
hs) of a negative sign (at any polarity of high
-
voltage pulses on CE). The fourth phase
-

longitudinal movement of FVChs inside volume of tube and occurrence of a lumine
s
cence of gas on
length

of the discharge pillar.

The use of cylindrical CE has allowed to establish the proportional dependence of the initial
size of FVChs from parameters (from each) excitation of the discharge: from e
n
ergy of an ele
c
trical
pulse on CE,
-



i
i
PS
t
i






i
CE
e
t
S
j



,









,

q
, from pressure of gas
p
, from the sizes of the
surface CE,
CE
S
, and duration
i
t

of sign FVChs (as a single whole) is ionize, e
x
cite and polarize the
molecules of
a vapor phase of the tested substance [3] or air [
2
] and is organize around FVChs the
l
u
minous shells from these molecules.

The existence of several sequential phases development of

discharge UBG
, their property
has allowed use CE of cylindrical geometry.

Thus the experiments installed d
e
pendence of
p
a
rameters describing each from 4 phases of
discharge
, from a gas pressure
p
, amplitudes
И


and
duration
И
t

of an impulse potential, from geometry

CE (plane CE on end walls of a tube or
c
y
lindrical CE on its surface), from it of square
ПЭ
S

and length
ПЭ
l
:
ПЭ
S
T
R

2



ПЭ
l
,
T
R
-

exte
r
nal radius of a tube).

The whole of properties distinguishing of the discharge UBG from known types of
di
s
charges requires of the new way of looking to an explanation of a nature not only of this
discharge, but also phenomenon of electri
cal discharges as a whole, from d
i
verse positions which
one should fundamentally of differ from known mechanisms of development of di
s
charges .

References

[1] I.V.

Gerasimov, Plasma Physics (Russia),
14

(1988), 1214
-
1221.

[2] I.V.

Gerasimov. Journal of Tec
hnical Physics (Russia),
65
(1994), 30
-
37.

[3].Gerasimov A.I., Gerasimov I.V.
Proc.
XXV Int. Symposium on Plasma Chemistry
,


O
r
leans. France. 2001
,
VIII
,

pp
.

3303
-
3309.