Macroparticle Movement Velocity in Dusty Structures of Various Compositions

0.14 MB·English

by  A. D. Khakhaev

A.D.KHAKHAEV,A.A.PISKUNOV,S.F.PODRYADCHIKOV
MACROPARTICLE MOVEMENT VELOCITY IN DUSTY
STRUCTURES OF VARIOUS COMPOSITIONS
A.D. KHAKHAEV, A.A. PISKUNOV, S.F. PODRYADCHIKOV
2
1
Petrozavodsk State University, Research and Educational Center on Basic Problems
0
of Applicationof Low Temperature Plasma Physics
2 PACS71.20.Nr;72.20.Pa
(cid:13)c2011 (10, UniversitetskayaStr., Petrozavodsk 185910, Russia; e-mail: [email protected])
n
a
J

8
1 Theresultsofexperimental investigationsofthemovementveloc- It is known from the previous experiments that the
ityof amacroparticle inthe dusty structures of various physical- macroparticles embedded into plasma acquire a kinetic

] chemical compositions formed inastratified column of adc glow temperature much more than the temperature of ambi-
h
p discharge, are presented. The macroparticle substances are alu- ent gas, i.e., the interaction between charged macropar-
mina (r = 10−35 µm), polydisperse Zn (r = 1−20 µm) and
m- Zn′ (r=20−35µm). Plasma-forminggases are inert gases (Ne, ticles and ambient plasma in ordered structures results
intheessentialheatingofmacroparticles[3]. Inwork[4],
Ar). The inverse relation between the velocity and the gas pres-
s sure(intherange40–400Pa)isfoundand,forthesamematerial the theoretical justification of the heating of macropar-
a
l ofmacroparticles indifferent gasplasmas, isconfirmed bytheory ticles due to a fluctuating electric field of plasma is pro-
p
anddoesnotcontradictobservations. But,toexplainadifference posed. An important result of that work is the expres-
.
s ofquantitativedataformacroparticles madefromdifferentmate- sionforthe kinetic temperatureofmacroparticleswhich
ic rialsinArplasma,theadditionalresearch isrequired. is propotionalto the electrontemperature Te. However,
s noquantitativeexperimentaldata,whichwouldconfirm
y
it for the complex plasma of a dc glow discharge, are
h
p available.
[ Inpresentwork,westudytheinfluenceofthephysical-

1 Complex plasma is a widespread state of matter in the chemical composition and some parameters of complex
v nature and technological operations. The problem of plasma on the velocity of macroparticles. In experi-
3 particles’kinetics in complex plasma arises,because the ments,weusethecomplexplasmaofadcglowdischarge
9
appearanceofmacroparticlesinplasmamodifiesplasma at low currents and pressures. The ordered structures
8
properties and gives rise to various processes: an in- (Fig. 1) are formed from macroparticles levitating in
3
. teractionbetweenmacroparticlesandionsandelectrons strata of a positive column.
1
0 gives rise to the charging of macroparticles, power from A vertically oriented gas discharge tube (the internal
2 plasma to macroparticles transfers through plasma os- diameter 2R = 30 mm) is employed [1,5]. The shape
1 cillations, macroparticles lose energy because of neu- of electrodes is a cylinder with a diameter of 25 mm.
v: tral impacts, negative charge of macroparticles gives A narrowing (diameter 2.5 mm) is placed within the
i rise to forming the particle flows in plasma, etc. The tube. The narrowing is necessary to the generation of
X
investigation of these and many other processes has a stablestandingstriationsinawiderangeofparameters.
ar high significance for power machines (tokamaks, lasers, Macroparticles are injected in plasma from a container
rocket engines, etc.), plasma technologies of material which is placed at the top of the tube. The macroparti-
processing and producing, astrophysics, for the phys- cle materials are Al2O3 (r = 10–35 µm, hri = 23 µm),
ical modeling of condensed matter, microcosmic ob- polydisperse Zn (r = 1–20 µm, hri = 8 µm), and Zn’
jects, and astrophysical objects inaccessible for exper- (r = 20–35 µm, hri = 28 µm). Plasma-forming gases
iments. are inert gases (Ne, Ar).
The plasma-dust structures in complex plasma repre- Powderisinjectedintoplasmabyshakingacontainer.
sent an unusual state of matter. We may expect that Macroparticles fall through the grid bottom and are
a variation of the physical-chemical characteristics of a trapped in strata. The glass tube is evacuated by a dif-
plasma-forming gas and a macroparticle material will fusion pump, and the base vacuum is about 10−5–10−4
result in quantitative changes of the characteristics of Torr. Thepressureofaplasma-forminggaspisvariedin
a structure, as well as in a macroparticle motion [1,2] theinterval0.3–3Torr,thedischargecurrentI is0.4–1.2
under similar conditions. mA(theelectrondensityne indust-freeplasmaisabout
1284
ISSN 2071-0186. Ukr. J. Phys. 2011. Vol. 56, No. 12
MACROPARTICLEMOVEMENTVELOCITY
Fig.2. Experimentaldependenceoftheaveragevelocityofmotion
of macroparticles on the discharge current: a)Ar+Al2O3 [2], b)
Ne+Al2O3 [2],c)Ar+Zn
Fig. 3. Macroparticle velocity versus the gas pressure (figures –
experiment,lines–approximationbytheinverserelation)atroom
temperature
macroparticle mean velocity of a displacement for 4 s
and the dispersion were calculated for 100 vi. Then the
ensemble averaging for N macroparticles (visible in a
cross-section) was made taking into account the disper-
sionofvelocityvalues. Errorswereestimated,bybasing
Fig. 1. Structures of macroparticles in a stratum glow discharge
on 3 measurements for each point in Fig. 2 and Fig. 3.
(agaspressureof0.6Torr, adischarge current of1mA)
The slight influence of the electron density on the
macroparticle velocity is evident from the dependence
108cm−3,theelectrontemperatureisaboutseveraleV). ofthe meanmacroparticlevelocityonthedischargecur-
Theprobemeasurementsundersimilarconditionscanbe rent(Fig.2). ThedischargecurrentI ≈eneveR2,where
found in [6]. ve is the electron drift velocity.
Macroparticles in a cross-section of the macroparti- Aninverserelationbetweenthemacroparticlevelocity
cle structure were observed by a CCD-camera for 4 s andthegaspressure(Fig. 3)wasfoundforordereddusty
(a picture frequency of 25 Hz). 100 displacements was structuresofvariouscompositions. Adecreaseoftheve-
done by every macroparticle for this time. Every dis- locity (Fig. 3)is causedby both the frictiononneutrals
placement dsi occurs for 1/25 s at a velocity vi. The and a decrease of the electron temperature. The trend
1285
ISSN 2071-0186. Ukr. J. Phys. 2011. Vol. 56, No. 12
A.D.KHAKHAEV,A.A.PISKUNOV,S.F.PODRYADCHIKOV
to curves v(p) for similar macroparticles (Al2O3) in Ar 4. O.S.Vaulina,A.Yu.Repin,O.F.Petrovetal.,JETP102,
andNeplasmacorrelateswithcurvesTe(p)forthe same 986 (2006).
gas plasma [7]. These experimental data are in agree- 5. A.V.Bulba,L.A.Luizova,S.F.Podryadchikovetal.,High
ment with the theory [4]. The influence of the electron Energy Chemistry 40, 125 (2006).
temperature on the macroparticlemotion was observed,
6. S.A.Khrapak,S.V.Ratynskaia,A.V.Zobninet al.,Phys.
for example, in experiments with a high-energy electron Rev. E72, 016406 (2005).
beam(tensofeV)undersimilardischargeconditions[8],
7. V.L. Granovskii, Electric Current in a Gas (Nauka,
but without quantitative measurements.
Moscow, 1971) (in Russian).
The conductedresearchesgive us anexperimentalev-
8. L.M. Vasilyak, M.N. Vasiliev, S.P. Vetchininet al., JETP
idence that the macroparticle material also influences,
96, 440 (2003).
in particular, the kinetic temperature of macroparticles
Received19.01.11
in ordered dusty plasma structures. This result is not
follow from[4] and cannotbe also explained by the fric-
tion on neutrals, because the macroparticles have ap- ШВИДКIСТЬПЕРЕМIЩЕННЯМАКРОЧАСТИНОК
′ УПИЛОВИХСТРУКТУРАХРIЗНОГО
proximately identical size (Al2O3 and Zn). To explain
КОМПОНЕНТНОГОСКЛАДУ
a difference of quantitative data for different materials
of macroparticles in Ar plasma, the additional research А.Д.Хахаєв, А.А. Пiскунов, С.Ф. Подрядчиков
is required.
Резюме
This work was partially supported by CRDF on
Наведено результати експериментальних дослiджень швидко-
Grants RUX0-013-PZ-06/BF7M13,the Ministry of Ed-
стi перемiщення мiкрочастинок у пилових структурах рiзно-
ucationandScienceofthe RussianFederation;theGov-
го фiзико-хiмiчного складу. Плазмово-пиловi структури фор-
ernment of Karelia.
мувались у стратах позитивного стовпа жеврiючого розряду.
Уролi пилової компоненти використовували частинки оксиду
1. A.V. Bulba, L.A. Luizova, S.F. Podryadchikov et al., in алюмiнiю (r = 10–35 мкм) i цинку (r = 1–20 мкм i r = 20–
AIPConf. Proc. on New Vistas inPlasmas ICPDP4 799 35мкм).Газовиминаповнювачамивиступалиiнертнiгази(Ne,
(2005), p. 359. Ar). Було отримано зворотнi залежностi швидкостi перемiще-
ннямiкрочастиноквiдтискугазу(вдiапазонi40–400Па).При
2. A.D. Khakhaev, L.A. Luizova, A.A. Piskunov et al., AIP
цьому для мiкрочастинок iз однакового матерiалу, але у пла-
Conf. Proc. on Multifacets of Dusty Plasmas: ICPDP5
змi рiзних газiв данi узгоджуються з теоретичними передба-
1049, 309 (2008).
ченнями i не суперечать спостереженням. Але, щоб пояснити
3. V.V. Zhakhovskii, V.I. Molotkov, A.P. Nefedov et al., розбiжнiстьушвидкостях макрочастинок рiзного матерiалу в
JETP Letters 66(6), 419 (1997). аргоновiйплазмi,потрiбнi додатковi дослiдження.
1286
ISSN 2071-0186. Ukr. J. Phys. 2011. Vol. 56, No. 12