HELIUM ATMOSPHERIC PRESSURE-DIELECTRIC BARRIER DISCHARGE ...mech-ing.com/journal/Archive/2011/8/113_Dineff_ENG.pdf · HELIUM ATMOSPHERIC PRESSURE-DIELECTRIC BARRIER DISCHARGE IN DIODE

HELIUM ATMOSPHERIC PRESSURE-DIELECTRIC BARRIER DISCHARGE IN

DIODE CO-PLANAR PLASMATRON

Assoc. Prof. Peter Dineff Ph.D., Assoc. Prof. Dilyana Gospodinova, M.Sc.-Eng. Momchil Shopov Faculty of Electrical Engineering– Technical University, Sofia, Bulgaria

Abstract: The main advantage of atmospheric pressure-dielectric barrier discharge (AP-DBD) is that non-equilibrium plasma conditions in atmospheric-pressure gases can be established in an economic and reliable way. These discharges consist generally of a great number of filaments in parallel. It has been demonstrated in the past that homogeneous barrier discharges can also be established in special electrode arrangements and in limited working domains under atmospheric pressure without any filaments. Diffuse helium barrier AP-DBDs would provide interesting new aspects if reliable control and average power densities can be achieved, comparable to those of filament discharges. Diffuse discharges have obvious advantages over filament discharges for homogeneous treatment of surfaces or for the deposition of thin films. An AP-DBD generated in diode co-planar direct plasmatron in helium was examined by monitoring the current and the voltage.

Keywords: atmospheric pressure-dielectric barrier discharge (AP-DBD), cold plasma, diode co-planar plasmatron, helium DBD, non-equilibrium plasma, surface plasma-chemical modification, surface plasma treatment.

1. Introduction The dielectric barrier discharge (DBD), also referred to as

dielectric barrier or just barrier discharge, silent discharge, or „corona” discharge, is characterized by the presence of at least one (two) insulating (dielectric) barrier in the form of a sheet, layer or coating, which is in direct contact with the electric dis-charge and is located between two planar or cylindrical elec-trodes, supplied with alternating voltage. Depending on the con-ditions, the size of the working (discharge) gap changes from 0,1 to about 100 mm, and the frequency of the applied voltage of industrial frequency (50 Hz) to up to several GHz. The materials used for the dielectric barrier are glass, quartz, ceramics, but also enamel or plastic, [4, 5].

The barrier discharges produce highly non-equilibrium (and non-isothermal) plasma under atmospheric pressure in various plasma-forming (diluted) gases, such as air, helium, argon, gas mixtures, vapour etc., with varying temperature. The barrier dis-charges provide controllable and efficient chemical active parti-cles generation (atoms, radicals, excited molecules and atoms, CASs) under normal conditions, by electrons with high enough energy - from 3 to 10 eV, [9].

Many of the barrier discharges used under high (atmospheric) pressure exist in the form of filament (discrete) discharges sets with short lifetime, appearing continuously at the same place and thus forming stable spatial structure of so-called micro dis-charges. There is also a diffuse (homogeneous) form of the bar-rier discharge, whose structure is very similar to that of the glow discharge (under low pressure), called „ pseudoglow” discharge at one of its first implementations in helium (R. Bartnikas, 1968).

2. Atmospheric pressure homogeneous barrier discharge

It is known that the glow discharge burns steadily only in vacuum at pressures of about 80100 Ра (about 1 mbar), creating technological non-equilibrium cold plasma in relatively large volumes. The glow discharge, however, becomes extremely un-stable at high pressure, striving to turn either in arc electric dis-charge, or in barrier discharge, which contains in its volume a great number of separate discharges arranged in a spatial struc-ture (S. Kanazawa., 1988; S. Okazaki, 1993; F. Massines, 1998; J. Tepper, 2000), the latter depending highly on the nature of the gas, the material of the dielectric barrier, the frequency of the applied voltage, the discharge (working) gap between the dielec-tric barrier and the electrode, or between the two dielectric barri-ers, on the gas humidity and purity.

The possibility to realize a diffuse (without filament, homo-geneous) atmospheric pressure glow discharge, APGD, was first reported in 1930 (von Engle). After this many authors (S. Kanazawa and M. Kogoma, 1988; T. Yokoyama, 1990; J. Harry, 1999) reported that they have managed to make APGD, defining three necessary conditions for this: i –supplying voltage frequency above 1 kHz; ii – presence of dielectric barrier (one or two) between the electrodes; iii – use of helium as plasma-forming gas.

The capacity of helium to produce atmospheric pressure glow (or rather homogeneous barrier) discharge is determined by its low electric strength - about 3 kV/cm, which is about ten times lower that that of the air under normal conditions (Y. P. Raizer, 1991). These conditions allow easy production of the required set of separate avalanches, composing it. (Y. Sawada, 1995). The presence of metastable levels with relatively long lifetime, make helium prone to ionization (penning) degree and explain this behaviour. To this must be added the modern idea of the positive charge's ability, or the so-called remnant, to absorb in its volume "slow" electrons, which play crucial role in the discharge devel-opment after each electrodes polarity change (F. Massines, 2005).

At the same time many research groups obtain diffuse non-equilibrium plasma through atmospheric pressure barrier dis-charges in various gases, including helium, neon, argon, nitrogen, oxygen, and air. Since 1987 results have been published of exten-sive research carried out by the groups of: S. Okazaki (Tokyo, Japan), F. Massines (Toulouse, France), J. R. Roth (Tennessee, USA), [5, 6].

The ability of the dielectric barrier to retain (absorb) electrons in its surface layer also contributes to the stable existence of APGD. The dielectric barrier, which is in electrets (electrically polarized) state, can retain sufficient quantity of electrons, which further enhances the memory effect observed at repetition of the elementary discharges, constituting the individual micro-discharge (J. Tepper, 19982000).

Surprisingly, however, an announcement appeared (S. Okazaki, 1993), indicating another possibility to stabilize APGD in air, argon or oxygen, and this at industrial frequency (50 Hz), using fine wire mesh electrodes. These initial studies were later confirmed (T. Yokoyama, 1990; J. Tepper, 2000), sug-gesting that fine steel wire mesh electrodes (for example a 325 mesh/inch, made of steel wire Ø 0,035 mm) are to be preferred to coarse grid electrodes (J. Tepper, 2002).

56

New research (Z. Buntat, 2010) shows, that the fine gauze can be replaced by a perforated aluminium sheet, which stabilizes the APGD even better at low frequencies.

3. Diode co-planar plasmatron with atmospheric pressure dielectric barrier discharge

A diode co-planar plasmatron has been created with pseudo-APGD (according to R. Bartnikas), that burns in helium stream (99, 95 %) at atmospheric pressure (1 atm; 101,325 kPa; 1 mbar; 760 Torr), and room temperature, fig. 1.

Fig. 1. Co-planar diode plasmatron with glass barrier (εr = 10), working with helium at atmospheric pressure (1 atm), and room temperature – semi-opened plasma technology system.

HV-E – high voltage electrode; GE – grounded electrode; DB – dielectric (glass) barrier; B – a bottle of helium; М – pres-sure gauge ; RM – pressure reducing valve; MV – electromag-netic valve; С – insulation cage.

The picture of the discharge, as seen through the transparent plasmatron insulation cage, shown on fig. 2, reveals the "pseudo-homogeneous” character of the barrier discharge.

Fig. 2. General appearance of barrier discharge at URMS = 20 kV (50 Hz) in co-planar electrode plasmatron with glass barrier at helium constant flow D = 0,7 dm3/min and atmospheric pressure (101,325 kPa or mbar; 760 Torr). The reflection of the discharge on the glass barrier can also be seen, as well as the „bush-like” discharges at the edge of the cage – where the helium leaves the plasmatron's semi-opened volume.

Three characteristics could de clearly discerned: i – the discharge homogeneous character inside the plasma-

tron volume; ii – the discharge filament character on the edge of the

grounded electrode GE; iii – the “bush-like” (non homogeneous) type of the discharge

outside the cage С, i.e. where the outgoing under pressure helium meets the ambient air.

Fig. 3. Distribution of the temperature in the plasmatron's vol-ume at different voltages URMS: a and b – 10 kV; c – 15 kV; d – 20 kV (termovision camera Flir i5, Flir Systems AD, Sweden, sensitivity 0,10 0C).

Therefore, in this paper hereafter will be used the generalized appellation AP-DBD, instead of APGD, fig. 2.

RM

He

He He He GE

Earth

НV

b d

MV

M1

C p1

p0

p0

p0

p0 Въздух Въздух

B

M2

DB HV-E

URMS = 10 kV

a)

20 30 25

26 24,5

32 29 29

24

27

b)

URMS = 20 kV

20 30 25

URMS = 15 kV

20 30 25

26 24,5 c)

URMS = 10 kV

d)

57

The insulation cage С, together with the grounded aluminium electrode GE, can slither over the glass barrier DB, moving in the plane, so that wide surfaces (not shown on the picture) of a prod-uct (foil, textile, corrugated cardboard, cardboard, thin wood panel) could be processed, placed between the edge of the insula-tion cage С and the glass barrier DB, fig. 2.

Table 1. Burning voltage Ubr, basic (Bi, Ai) parameters and voltage

(Ucr,i; i = 0, 1, 2...) and discharge current (Icr,i, i = 0, 1, 2,...) critical parameters of AP-DBD in helium.

The helium is fed inside the insulation bell-shaped cage С in the form of a continuous flow at a rate of 0.7 dm3/min and at constant pressure 1 atm, which is controlled by the mounted pres-sure gauge М2. The bell-shaped cage allows the helium to keep inside even if the gap between the cage and the glass barrier is considerably increased. Since helium is lighter than air (on sea level) – 0.1785 kg/m3 << 1.2 kg/m3, it stays inside even if the cage is carefully lifted and removed from the surface of the glass barrier (without turning the aperture upwards), fig. 1.

The half-opened type of plasmatron implementation, [4], al-lows operation at significantly lower helium flow rate compared to the jet-plasma system with helium atmospheric pressure radio frequency (RF-) discharge, [8].

A two co-planar two electrodes (diode) system comprises a single glass barrier DB made of alkaline glass 3 mm thick, di-rectly contacting the discharge and carrying on its external sur-face the high-voltage electrode HVE, representing an aluminium foil firmly stuck to it. The electrode system is supplied with al-ternating voltage - up to 30 kV (RMS), at industrial frequency (50 Hz).

Photos on Fig. 3 submit the thermograms, showing the ther-mal field distribution within the plasmatron's volume in three of the most commonly used AP-DBD operating modes. The maxi-mum temperature within the plasmatron's volume does not ex-ceed 32 0С, and the incoming helium temperature in the dis-charge zone is about 24.5 0С at ambient temperature of about 19 0С. The glass barrier reflects from its surface the cage with the grounded electrode inside GE, as well as the AP-DBD itself, which burns between the glass barrier DB and the electrode GE.

The more intensive heating of the grounded electrode is clearly seen, but despite this its temperature does not exceed 27.5 0С. Its reflection on the glass barrier does not allow "to see"

the heating of the lower electrode HVE, which is in better thermal condition than the upper grounded electrode GE, fig. 1 and 3.

Table 2. Burning voltage Ubr, basic (Bi, Ai) parameters and voltage

(Ucr,i; i = 0, 1, 2...) and discharge current (Icr,i, i = 0, 1, 2,...) critical parameters of AP-DBD in helium.

4. External static characteristic For each operating mode the AP-DBD external static charac-

teristic in air can be represented by a linear dependence between the average value of current IAVG (or the density of current JAVG) and the voltage effective value applied to the electrode system URMS, or as a whole it can be presented by a system of lines, [6].

The AP-DBD external static characteristic in helium has the same type and can be represented as a whole in the same way as AP-DBD in air, which shows that the barrier discharges charac-teristic feature can be observed also in its burning in helium - each operating mode is characterized by burning voltage constant value Ubr,i (i = 1, 2, ...). The critical voltage Ucr,i (i = 0, 1, 2, ...), characterizing either the ignition (burning) voltage (Ucr,0), or the transition from one operating mode to another (Ucr, i, i = 1, 2, 3,...), is always greater than its corresponding burning voltage Ubr,i, table 1 and 2, fig. 4.

The biggest difference (Ucr,i – Ubr,i) can be observed in the transition to the third (C) AP-DBD helium burning operating mode, as the increase of the working gap distance d leads to a slight increase of both voltages - the burning voltage Ubr,i and its corresponding critical voltage Ucr,i, fig. 4.

The AP-DBD discharge plasma deviation from the local thermodynamic equilibrium (LTE) is estimated by the relative difference in the temperatures of the heavy Tg and the light Te plasma component according to the criterion of Finkelnburg and Maecker (1956), and at constant pressure (p = p0 = const) and constant temperature (T = T0 = const) it is determined by the following expression, [7, 9]:

2221

nE

Tkσe

mm

aT

TTFM

eee

g

e

ge (1)

or the given electric field intensity (Е/n) determines the dis-charge non-equilibrium level.

Discharge gap d = 3 mm B0 = 12.534 A/kV A0 = 0 A R2 = 0.9999 B1 = 19.67671 A/kV A1 = -11.5663 A R2 = 0.9651 B2 = 183.0744 A/kV A2 = -869.551 A R2 = 0.9985 Ucr,0 = 1.619 kV Icr,0 = 20.289 A Ucr,1 = 5.251 kV Icr,1 = 91.766 A Ubr,1 = 0.588 kV Ubr,2 = 4.750 kV


Discharge gap d = 9 mm B0 = 11.261 A/kV A0 = 0 A R2 = 0.9999 B1 = 28.27866 A/kV A1 = -37.2276 A R2 = 0.9493 B2 = 156.11 A/kV A2 = -793.1 A R2 = 0.9996 B3 = 222.89 A/kV A3 = -1804.8 A R2 = 0.9980 Ucr,0 = 2.188 kV Icr,0 = 24.636 A Ucr,1 = 5.913 kV Icr,1 = 129.985 A Ucr,2 = 15.149 kV Icr,2 = 1571.927 A Ubr,1 = 1.316 kV Ubr,2 = 5.080 kV Ubr,3 = 8.097 kV

Discharge gap d = 12 mm B0 = 7.003 A/kV A0 = 0 A R2 = 0.9999 B1 = 38.54545 A/kV A1 = -77.8182 A R2 = 0.9660 B2 = 144.6004 A/kV A2 = -755.297 A R2 = 0.9997 B3 = 200.2087 A/kV A3 = -1615.45A R2 = 0.9992 Ucr,0 = 2.467kV Icr,0 = 17.277 A Ucr,1 = 6.388 kV Icr,1 = 168.41 A Ucr,2 = 15.468 kV Icr,2 = 1481.392 A Ubr,1 = 2.019 kV Ubr,2 = 5.223 kV Ubr,3 = 8.069 kV

Discharge gap d = 15 mm B0 = 4.1384 A/kV A0 = 0 A R2 = 0.9999 B1 = 31.92146 A/kV A1 = -96.3636 A R2 = 0.9643 B2 = 163.0245 A/kV A2 = -876.74061 A R2 = 0.9993 B3 = 238.6667 A/kV A3 = -2255.5556 A R2 = 0.9992 Ucr,0 = 3.468 kV Icr,0 = 14.354 A Ucr,1 = 5.952 kV Icr,1 = 93.645 A Ucr,2 = 18.228 kV Icr,2 = 2094.891 A Ubr,1 = 3.019 kV Ubr,2 = 5.378 kV Ubr,3 = 9.451 kV


58

Fig. 4. Burning voltages Ubr,i and critical voltages Ucr,i,

characterizing the different operating modes A, B and C of the helium atmospheric pressure barrier discharge burning at room temperature.

The given intensity Е/n, characterizing the helium AP-DBD collision ionization, has a low value - for example, when the electric field intensity is near to the helium electric strength – 3 kV/cm (Up = US = 3 kV, d = 1 cm), and the particles concentra-tion n = 2.5 1019 cm-3 (p0 = 1,01.105 Pa), the given intensity is 1.2 10-16 V.cm2, while for air when the electric field intensity is 30 kV/cm (pick value), the given intensity is ten times bigger.

Fig. 5. Plasmatron external static characteristic "density of

the discharge current JAVG – discharge gap size d” at voltages URMS up to 6 kV (experiment).

Helium reduces the AP-DBD non-equilibrium, which means that the shock interaction between the light and the heavy plasma component is improved and the electrons' "overheating" is sig-nificantly reduced. From technological point of view this means that the following AP-DBD advantages should be expected: greater ionization degree, greater densities of current and dis-charge active power, which will determine greater plasma-chemical changes' intensity in the helium plasma.

On the other hand, however, the reduced overheating and electrons temperature (Те) increases the helium plasma non-equilibrium, which compensates to a certain extent the above effect, equation 1.

The intersection of shock interaction between the electron е and the helium is one of the smallest, since the helium atom di-ameter exceeds only the hydrogen atom diameter (the diameter of the hydrogen molecule, however, is bigger). This also compen-sates to a certain extent the decrease of the helium plasma non-equilibrium. The end result, however, is helium plasma, which compared to the air plasma has significantly lower non-equilibrium degree.


the discharge current JAVG – discharge gap size d" at voltages URMS from 7 to 21 kV (experiment).

All parameters of the external static characteristic operating modes, as well as the critical parameters of ignition and transition from one helium AP-DBD operating mode to another are given in table 1 and 2.

It should be noted, however, that the exact transitions' loca-tion can not be determined directly from the external static char-acteristic. The threshold character (by voltage) of this transition does not allow its definition through the discharge current, re-spectively through the current's density. If during an electrolysis the process (of oxidation and reduction) remains constant and the anode or cathode behaviour can be monitored through the cur-rent, for the electrical discharges with clearly pronounced thresh-old processes (by voltage) the active power change remains the only means of integral monitoring of the plasma-chemical changes within the volume or on the surface.

The critical voltage burning Ucr,0 of AP-DBD, however, can be determined by the external static characteristic, as the transi-tion is from a capacitive character current mode to a transition with capacitive-active character of the current. In the transitions from one operating mode to another a shift of the critical voltage by power can be observed to grater voltage values: Ucr,p > Ucr. Therefore the place of these transitions on the voltage scale can be determined exactly only after setting the technological charac-teristic "active power or active power density - voltage RMS value".

5. Helium discharge burning stages The external static family characteristics, obtained by chang-

ing the working gap distance d, allows building a new family characteristics “density of current JAVG – discharge gap size d” at

Burn

ing

volta

ge U

br, i

and

criti

cal v

olta

ge U

cr,i,

kV

0 2 4 6 8

10 12 14 16 18 20

0 3 6 9 12 15 18 21 Discharge gap d, mm

Ubr,1

Ubr,2

Ubr,3

Ucr,1

Ucr,1

Ucr,2

A

B

B B

C

0

50

100

150

200

250


10

8 7

9

14

12 11

13

18

16 15

17

20 19

21

Parameter: Voltage URMS, kV

A B C

Barrier: b = 3 mm (alkaline glass)

Dis

char

ge c

urre

nt d

ensit

y J A

VG, m

A/m

2

0

2

4

6

8

10

12

14

16

3 6 9 12 15 18 21 Discharge gap d, mm

5

3

6

2

4

1



A

B

C Dis

char

ge c

urre

nt d

ensit

y J A

VG, m

A/m

2

59

constant value of the voltage applied to the electrodes, fig. 5, 6 and 7.


the discharge current JAVG – discharge gap size d" at voltages URMS from 21 to 30 kV (extrapolation).

The change in the working gap distance d, at constant pres-sure (p = p0 = const), violates the electric discharges similarity conditions at one and the same voltage: (U1 = U2 = U) - p1 d1 = p2 d2 = a = const, where a is the similarity scale:

12

12

21

EE

pp

dda .

(2)

At these conditions the different stages (mechanisms) of AP-DBD development in helium appear in the form of typical peaks, fig. 5, 6 and 7.

Fig. 5 and 6 present family characteristics, drawn in a known way, [6], from the experimentally obtained external static charac-teristics, and fig. 7 – a family of prognostic characteristics, ob-tained in the same way, but out of the experimental field.

Fig. 8 shows, for the sake of comparison, a family of analogi-cal characteristics, but for AP-DBD in air.

The comparison between the two studied AP-DBD, in air and in helium, allows the following conclusions, fig. 5, 6 and 8:

- the helium discharge has significantly greater current IAVG, respectively current density JAVG – more than three times;

- the main stages (forms, phases) of the AP-DBD develop-ment are presented – the avalanche (the typical maximum А), the stage of cathode directed streamers or negative streamers (В), and the stage of anode directed streamers or positive streamers (С);

- the three stages of helium AP-DBD present themselves completely at voltages above URMS = 2 kV (Up = 2,82 kV), while for the air AP-DBD this can be observed at voltages above URMS = 16 kV;

- the three stages (A, B and C) of helium AP-DBD are fully manifested at working gap above 15 mm, while in air this hap-pens above 12 mm, – the three stages, however, have almost similar current (or current density), while for AP-DBD it is not so.

Fig. 8. Change of the current density JAVG due to discharge

gap size d change of the co-planar diode system at different volt-age URMS, which reveals peaks A, B and C, corresponding to different mechanism of atmospheric pressure barrier discharge burning in air.

The exact location of the stages (peaks) on the discharge gap size d scale can be established only after setting the correspond-ing technological family characteristics. Therefore at this stage the analysis is limited to the type and number of these peaks.

Conclusion A half-opened plasma system has been created, called cold

plasma direct plasmatron, which can produce helium, air or other gases non-equilibrium plasma.

The plasmatron consists of two parts: upper, representing an insulated high voltage electrode with dielectric barrier placed on its surface; lower, representing a bell-shaped cage with grounded metal electrode (with or without dielectric barrier).

The two parts can move without limitation in relation to each other within the working plane. A co-planar electrode system has been demonstrated, but the same idea can be applied to the cylin-drical electrode system. The great advantage of the created plas-matron is the ability to process wide areas of materials - polymer foils and sheets, textiles, leather, cardboard, corrugated card-board, paper, plywood.

The plasmatron created is particularly important when work-ing with lighter than air gases (helium), as the insulation bell-shaped cage allows the gas to fill its volume quickly, expelling the air. With continuous helium supply under pressure (1 atm) this environment can be maintained for a long time, moving the helium-air mixing at the plasmatron cage exit. Compared to the open jet plasma systems, [8], the helium consumption is consid-erably reduced. It can be supposed that there is occasional helium - air mixture, but by increasing the flow this influence can be significantly limited.

The helium atmospheric pressure barrier discharge has the following main advantages as compared to the same discharge in air:

Den

sity

of th

e di

scha

rge

curr

ent

J AVG

, mA

/m2

0

15

30

45

60

0 2 4 6 8 10 12 14 16 Discharge gap d, mm

20

19

18

17

16

15

14 13

12

11 10 9

8 7 6 543

Al-Al



A

B

C

100

150

200

250

300

350


Den

sity

of th

e di

scha

rge

curr

ent J

AVG,

mA

/m2

24

22 21

23

28

26 25

27

30 29

A B C

Parameter: VoltageURMS, kV


60

1) The helium AP-DBD carries the characteristic of all barrier discharges – the discharge burns at constant burning voltage, which is different for different operating modes – the burning voltage increases slowly with the working (discharge) gap dis-tance increase;

2) all helium AP-DBD operating modes are characterised by linear correlation (high linear correlation coefficient – almost functional characteristic!) between the average discharge current value (measured by tools) and the applied voltage RMS- value (measured as well by tools);

3) the helium AP-DBD external static characteristic can be modelled with sufficient accuracy by determinate number of lines including all operation modes and the pre-discharge AP-DBD mode;

4) the helium AP-DBD external static characteristic allows exact determination of the discharge burning voltage, but does not allow to determine exactly the critical voltages of the opera-tion mode transitions – this can be done only by the discharge technological characteristic „active power, surface or volume density of the active power – voltage RMS- value”;

5) adopting the current critical voltage as indicator of the op-eration mode transition leads to technological discharge charac-teristic, which have no physical basis, the real power critical voltage is determinant for this transition's location;

6) the helium AP-DBD is characterized by lower non-equilibrium level than the analogical discharge in air, according to the criterion of Finkelnburg and Maecker, which means, that the discharge's increased intensity is accompanied by lower tem-perature and energy electrons production (lower overheating)– it can turn out that the plasma-chemical discharge effectiveness is lower, despite its increased intensity;

7) the helium AP-DBD provides considerably greater elemen-tary processes intensity within the volume and on the surface, including those, which provide plasma-chemical treatment - the current density under comparable conditions can increase more than three times;

8) the helium AP-DBD provides the same discharge current density at significantly lower voltages;

9) a direct helium plasmatron has been created for techno-logical cold plasma atmospheric pressure production, which can find its application both in technological lines and outside them, at manual or automatic operation mode.

Acknowledgements The present work was carried out with the exclusive financial

support of the National fund for scientific research with the Ministry of education, youth and science through the research project HS-TSc 2005/2006.

References [1] Kogelschatz, U. Filamentary patterned, and Diffuse Bar-

rier Discharges. IEEE Transaction on Plasma Science, 2002, vol.: 30, Issue: 4, pp. 14001408.

[2] Golubovskii, Y., V. Maiorov, J. Behnke1, J. Behnke1. In-fluence of Elementary Processes Over a Homogeneous Barrier Discharge in Helium. Journal of Physics D: Applied Physics, 2003, Vol.: 36, Issue 1, pp. 39 44.

[3] Tepper J., M. Lindmayer. Investigations on two Different Kinds of Homogeneous Barrier Discharges at Atmospheric Pres-sure. HAKONE VII International Symposium on High Pressure, Low Temperature Plasma Chemistry, Greifswald, Germany, September 1013, 2000, pp. 16.

[4] Wagnera, H.-E, R. Brandenburga, K. Kozlov, A. Son-nenfeldc, P. Michela, J. Behnke. The barrier discharge: basic properties and applications to surface treatment. Vacuum, 2003, Vol.: 71, pp. 417436.

[5] Dineff, P. Industrial plasma surface processes at atmos-pheric pressure. Х. International scientific conference on cutting-edge materials and processing „АМО ‘10”, 2729 June, 2010, Varna, Bulgaria. Abstracts collection, 2010, pp. 104105. Pro-ceedings, Sofia, Publishing house „St. Ivan Rilski”, 2010, pp. 182 190 (in Bulgarian).

[6] Dineff, P., D. Gospodinova, М. Shopov. Plasma tech-nologies. – Laboratory exercises manual. Sofia, Avangard-Prima, 2008. (in Bulgarian)

[7] Dineff, P., D. Gospodinova. Technological characteris-tics of magnetically driven barrier discharge. International Vir-tual Magazine for Science and Innovations for Industry „Ma-chines, Technologies, Materials”, 2010, Year ІV, Issue 45, pp. 3944. (in Bulgarian)

[8] Babayan, S., R. Hicks, and G. Selwyn. Deposition of Coatings Using an Atmospheric Pressure Plasma Jet. U. S. Pat-ent 6 194 035 B1, Issued February 27, 2001.

[9] Becker, K., U. Kögelschatz, K. Schoenbach, R. Barker (Eds). Non-equilibrium Air Plasmas at Atmospheric Pressure. Bristol and Philadelphia: Institute of Physics Publishing, 2005.

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HELIUM ATMOSPHERIC PRESSURE-DIELECTRIC BARRIER DISCHARGE ...mech-ing.com/journal/Archive/2011/8/113_Dineff_ENG.pdf · HELIUM ATMOSPHERIC PRESSURE-DIELECTRIC BARRIER DISCHARGE IN DIODE