The Effect of Electronic Disposition of Spherical Electrode on Plasma

Behavior in Argon Gas Media

David Suban Koten, Monalisa Malelak and Mikael Namas

Institute Department of Electrical Engineering, State Polytechnic of Kupang, Kupang, Indonesia

Keywords

Plasma Reactor, Spherical Electrode, Argon Gas, Paschen Curve, Breakdown Voltage.

Abstract:

Plasma is an ionized gas, a substance whose electrons leave the orbit of each atom and can be created by

heating a gas or exposing a sufficiently strong electromagnetic field using a laser or microwave generator.

This study examines how to design a high voltage plasma generator so that it can supply direct current (DC)

voltage to generate plasma in the reactor chamber containing low-pressure argon gas. In this study, the

breakdown voltage analysis was also carried out until a plot of the relationship between the breakdown

voltage, gas pressure, and distance between the electrodes was found. It is expected that the plotting can be

adjusted to the curve according to Paschen's Law and get results that are close to the ideal curve. This research

also aims to see the condition, behavior, and discharge of plasma that results from the release of spherical

electrode electrodes, so that the results of this research can carry out in an industry, agriculture, and electro-

medical.

INTRODUCTION

Plasma is an ionized gas, a substance whose

electrons come out of the orbit of each atom and can

be created by heating the gas or by exposing a

sufficiently strong electromagnetic field using a laser

or microwave generator. The increase or decrease in

the number of electrons present in the plasma results

in particles with positive or negative charges called

ions. This can usually be followed by the untying of

the molecule. The appearance of a large electric

charge makes the plasma conductive, so it reacts very

strongly to electromagnetic fields. Like gas, plasma

does not have a fixed shape or volume unless it is in

a closed space. However, unlike gases under the

influence of magnetic fields, plasma can form a

variety of structures such as filaments, beams, and

bilayers. Industrial and commercial applications of

plasma technology include plasma cutting (a

technology that emerged from plasma welding in the

1960s) and is a highly productive way to cut sheet

metal and plate.

Plasma welding, in this application, uses high

frequency and voltage. Plasma welding is much better

than tungsten welding because the welding process

can be faster. Besides, there is also the plasma

nitriding method, which is a function of plasma in the

hardening process of metal materials. In this

application, a metal material is placed between the

cathode and the anode electrode in a vacuum tube,

releasing an electric current. Applications in other

commercial and industrial fields, namely the

manufacture of ozone, sterilization of pool water,

removing various unwanted volatile organic matter,

such as chemical pesticides, solvents or chemicals

from the atmosphere, and as ionizing air which is

good for health. Of the various applications of plasma

technology, both in the industrial and commercial

world that have begun to be developed, there are still

obstacles in the application of plasma technology in

the form of devices that are not yet available on the

market or freely sold. One of the contributing factors

is how to design a plasma reactor system that has low

pressure (vacuum) and produces a high plasma

discharge.

Based on the description above, this research will

design a plasma generator that will generate from an

HVT (high voltage transformer) that produce a

voltage to activate the plasma on the electrodes

installed in an airtight tube. HVT functions to convert

an AC voltage of 220 V to an AC voltage of 2000 V,

while the high voltage diode and capacitor function

as a rectifier and filter circuit and then converts the

2000 V AC voltage to 2000 V DC voltage. From the

plasma generator made, an optimization of the plasma

Koten, D., Malelak, M. and Namas, M.

The Effect of Electronic Disposition of Spherical Electrode on Plasma Behavior in Argon Gas Media.

DOI: 10.5220/0010967300003260

In Proceedings of the 4th International Conference on Applied Science and Technology on Engineering Science (iCAST-ES 2021), pages 1459-1466

ISBN: 978-989-758-615-6; ISSN: 2975-8246

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

1459

formation process parameters will be carried out,

namely knowing the Paschen curve of the gas used

(argon gas). This research will use a ball electrode

type. The choice of the shape of the spherical

electrode is based on its function, which is to obtain a

very high electric field so that it can produce a large

enough plasma debit.

The research to be carried out is also in line with

the 2017-2045 National Research Master Plan

(RIRN) to support the direction of national

development in the field of science and technology,

as well as respond to the government's commitment

to supporting the development of advanced materials.

BASIC THEORY

2.1 Plasma

Plasma is one of the four basics forms of matter,

apart

from solid, liquid, and gas. Plasma has different

properties compared to the other. Plasma can be

created by heating a gas or exposing it to a strong

electromagnetic field, which can generate using a

laser or a microwave generator. Basically, plasma is

an ionized gas, which has atoms whose electrons

bounce out of their orbits. This results in the plasma

being able to conduct electricity because the atoms

themselves no longer have a positive balance between

the positive and negative charges, but the atoms are

positively charged due to the presence of protons in

the core, while the electron cloud that exists between

the atoms is negatively charged. The concept of

plasma was first described by Langmuir and Tonks in

1928. They defined plasma as a gas that is ionized in

an electric discharge, so plasma can also be defined

as a neutral-neutral mixture of electrons, radicals,

positive and negative ions. The mixing of positively

charged ions with negatively charged electrons has

very different properties from that of the general gas

and matter in this phase is called the plasma phase.

2.2 Collecting the Data

Plasma is an ionized gas. Ionization events are

always present in the process of plasma. Ionization is

the process of releasing electrons from an atom or

molecule from its bonds. The energy required to

remove one or more electrons from its orbit in an

atom is called the ionization energy E. The amount of

ionization energy is expressed in electron-Volts (eV).

In a stable state, ionization can occur if the energy of

the colliding electron is greater than or equal to the

ionization energy of the atom or molecule collided,

which is shown in Equation (1).













2≥ 𝑒𝑉

𝑖

(1)

Where:

= rest mass of the electron (9.109534 · 10- 31 kg)

νe

= velocity of the electrons (m s-1)

= elementary charge (1.6021892 · 10-19 C)

Vi = ionization potential of an atom or molecule

(eV)

In the process of collisions between electrons and gas

particles not only ionization occurs but also causes

other events. The opposite of the ionization process is

the recombination process. Recombination occurs by

binding of electrons by ions and binding between

atoms to become molecules so that they become

neutral species or negative ions accompanied by

photon emission (Nur, 2011).

2.3 Analyzing the Data

The discharge of electricity in gases has been a

long-standing subject in physics. The release in the

gas that is best known in nature is lightning. Gas,

which is an insulator by nature, will turn into a

conductor under certain conditions. The following is

the mechanism of lightning. Clouds that are close to

the earth's surface have a very high potential

difference from the earth's surface. Due to cosmic

radiation, there is the ionization of the gas between

the cloud and the ground.

This ionized gas increases in volume and allows

chain ionization to occur because the electrons

produced in the ionization are accelerated towards the

cloud and on their way collide with gas atoms and

molecules.

This event continues and in a certain condition,

there

is an electronic avalanche. The air (gas)

between the

clouds and the earth becomes a conduit in

the form of

a canal and emits white light. Electrical

discharge

(electrical discharge) has occurred in nature,

followed

by the sound of lightning which is the

sound of

meeting between air separated in a short

time by a

channel of discharge between cloud and

earth and

between cloud and cloud.

In the laboratory, the discharge of electricity can

carried out in a gas-filled tube. If two electrodes in

the form of parallel plates are placed in a tube

containing

gas with a certain pressure and the two

electrodes are connected to a high voltage DC source,

there will be a discharge of electricity between the

electrodes. Gas discharge tube can be seen in Fig.1.

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Figure 1: Gas Discharge Tube.

The electrons from the cathode will move towards

the

anode and during their travel, the electrons will hit

the

molecules or gas atoms between the two

electrodes. For chain ionization to occur, the first step

that must be passed is the ionization to produce free

electrons. Scientists believe the first electrons came

from the ionization of gases by cosmic ray radiation.

This first electron is accelerated by the potential

difference between the two plate electrodes in the

discharge tube. In their journey, these electrons will

collide and ionize other atoms or gas molecules in

succession. The process of consecutive collisions will

produce electronic avalanches and can lead to chain

ionization.

2.4 Electric Field Generating

Electrodes

The electric field distribution, which is greatly

influenced by the shape and dimensions of the

electrodes, the distance between the electrodes, and

the number of electrodes arranged. In selecting the

electrode material, it is emphasized on its function,

which is to produce a very high electric field

(Davidson, 2000). Fig.

2 shows the types of electrodes

used to generate high

electric fields.

Figure 2: Types of High-Field Generating Electrodes.

2.5 Electric Field Intensity

The electric field is an area around an electric

charge which is affected by an electric force. Michael

Faraday describes the electric field as a vector of

electric field lines coming out of the positive charge

into the negative one. The greater the intensity of the

electric field is depicted by the denser of field lines.

Each point in the electric field is a quantity that

expresses the level of strength of it, which is called

the electric field intensity. The intensity of the electric

field is the electric force that rests on one unit of

electric charge (Iskander, 1992). Electric field

intensity is the

electric force defined by Coulomb as

the force that

arises between two points of charges

separated by a

certain distance. This law states that

if there are two

points of charge there will be a force

between them

which is proportional to the

multiplication of the

values of the two charges and

is inversely

proportional to the square of the

distance between

them (Koefl and Saengl,2000), Fig.

3 shows vector electric field line

generated by

electric charges.

Figure 3: Vector electric field line generated by electric

charges (a) one point of positive charge, (b) one point of

negative charge, (c) two like charges, (d) two dissimilar

charges.

RESEARCH METHODS

This research begins with the design of tools,

manufacture, and testing of tools to determine the

shape of the plasma which is produced from the

release of spherical electrons in the argon gas medium

and to determine the plasma debit generated in the

plasma reactor. The results of this research will be

used as initial data for further research on the

application of plasma technology in industry,

agriculture and medicine. The stages of this research

can be seen in Fig. 4, which explains the procedures

for implementing the research to be carried out.

The Effect of Electronic Disposition of Spherical Electrode on Plasma Behavior in Argon Gas Media

1461

Figure 4: Research Flow Chart.

The stages in this research are:

Plasma generator system design.

Manufacture of a plasma generator system

consisting of manufacturing a power supply,

manufacturing a vacuum tube, installing a

vacuum

pump, installing pipes and valves,

installing an argon

gas reservoir, installing

measuring instruments, and

manufacturing an

electrode system.

Plasma behavioral testing.

Data retrieval.

Analysis of the performance of the resulting

plasma.

The airtight tube as a reactor filled with low-pressure

argon gas is evacuated through the pipe using a

vacuum pump and controlled by a valve, the cylinder

containing high-pressure argon gas also acts as a

supplier of argon gas and is controlled by a valve. The

gas pressure in the reactor can be observed with a

pressure gauge. The anode and cathode are made of

spherical copper. The electrodes are arranged in

parallel. The power supply used for the anode and

cathode is a source with a maximum voltage of 2000

VDC. The Plasma generator system design is shown

in Fig. 5.

Figure 5: Plasma Generator System Design.

RESEARCH RESULTS AND

DISCUSSION

By the research method, the first step taken in

designing the tools, then making the tools, and testing

them, then analyzing the results and making

conclusions.

4.1 Research Tools

The tools used to conduct research are divided

into

several parts. The first is the power supply, which

functions to supply direct high voltage (DC). This

section converts the input in the form of an alternating

voltage of 220 V into a direct voltage that can be

adjusted from 0 V to 2000 V. Fig. 6 shows parts of

the power supply.

Figure 6: Parts of the Power Supply.

The second part is the plasma reactor, which must

a transparent, airtight space so that visual

observations can be made. In the room, there is a ball

electrode that can be changed the distance between

the anode and cathode.

Star

Design Tools

tool making

Plasma behavior testing

Performance analysis

Conclusion

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Figure 7: Plasma Reactors Used in Research.

Fig. 7. shows the plasma reactor used in this study.

the base there is a flat metal platform covered by a

silicon glue seal to create a vacuum when the reactor

glass is closed from above, thus preventing gas

leakage from outside into the reactor. Fig. 7 also

shows the ammeter at the bottom of the reactor

platform, which is used to measure the amount of

current when plasma occurs in the reactor. The

plasma contours of the reactor are shown using

special software, namely FEMM. The illustration in

the software calculation results shows a slice of the

electric field intensity and electric field flux in 2

dimensions using a vacuum.

Figure 8: The Intensity of The Electric Field at The

Spherical Electrode with a Distance of 1 cm and a Voltage

of 200 V.

Fig. 8 shows the electric field intensity of a

spherical

electrode with a distance of 1cm and a

voltage of

200 V. From Fig.8 it can be analyzed the

behavior of

the electric field that occurs at a spherical

electrode in

the form of a field that collects at the

cathode and

is spread along the spherical electrode

surface as

well. The distribution of the electric field

is also

visible at the anode, but very little. When

viewed

from Appendix 3, the higher the voltage used,

the

higher the intensity and the slightly more scattered

the

shape of the electric field is in the spherical

geometry. In this simulation, voltage 200 V, 500 V,

1,000V, and 1,500 V. As for the greater distance

between the electrodes, it can be seen that the shape

of the electric field is constant. In this simulation, a

distance of 1 cm, 5 cm, and 10 cm are used. The

results of plotting the electric field intensity of the ball

electrode with a distance of 1 cm and a voltage of 200

V are shown in Fig. 9.

Figure 9: The results of plotting the electric field intensity

of the ball electrode with a distance of 1cm and a

voltage of

200 V. Source: Software Simulation FEMM.

4.2 Retrieval of Data

Data was collected by gradual iteration in

accordance

with the aim of obtaining a Paschen curve

which

shows the relationship between the breakdown

voltage and the electrode distance and the argon gas

pressure.

Retrieval of data starts from the electrode distance

of 0.25 cm. First, the distance between the electrodes

is adjusted until the tip of the anode needle with the

tip of the cathode needle is 0.25 cm, then the

adjustment bolt is locked and the reactor is closed.

Table I shows an example of data collection carried

out at a pressure of 0.8 Torr and an electrode distance

of 0.25 cm.

In Table I, one of the observations of the

breakdown voltage that occurs in argon gas with a

pressure of 0.8 Torr and the distance between the

electrodes (using a needle) is 0.25 cm. In Table I, the

voltage data is skipped up to 265 V because the

current values are both 0 mA. It can be seen that when

the voltage reaches 268 V a sudden 120 mA of current

is formed, and visually a plasma is formed in the

reactor.

An example of plasma display is shown in

Figure

10. In taking this data, it can be concluded that

the

breakdown voltage for a pressure of 0.8 Torr and a

The Effect of Electronic Disposition of Spherical Electrode on Plasma Behavior in Argon Gas Media

1463

needle electrode distance of 0.25 cm is 268 V.

Observations by increasing the voltage are no longer

needed because the breakdown voltage has been

obtained. Figure 15 shows the relationship between

current and voltage.

Data collection was carried out continuously for

different pressures with a pressure gap of 0.1 Torr. At

the next level, data collection is carried out for

different electrode distances (made further).

Figure 10: One of the Experiments when there was Plasma

in The Reactor.

Table 1: Combined Average Breakdown Voltage Data

from

Each Electrode Distance and Type of Ball Electrode.

Table 1, shows the average breakdown voltage of

the spherical and plate electrodes. Fig. 11 shows a

data comparison graph of all electrode distances for

the spherical electrode.

Figure 11: Retrieval of Argon Gas Breakdown Voltage

Data

for All Spherical Electrode Data at a Distance of

0.25cm to 2.00cm.

4.3 Searching the Ideal Paschen Curve

From the results, the actual Paschen Curve is

obtained in accordance with the results of the ball

electrode data collection. From this data, several

values can be taken, including values A, B, and γSE.

Because there are difficulties in getting the Ideal

Paschen Curve using the equation in Paschen's Law,

the strategy for finding the Ideal Paschen Curve is

divided into two, the first uses the Paschen's Law

equation approach, and the second uses the

polynomial approach.

Fig. 12 shows the results of plotting the average

breakdown voltage from all distances in the

experiment, where the Ideal Paschen Curve will be

searched based on the results of this plotting. In both

approaches, MSE (mean squared error) is used as an

indicator of the similarity of the observed data with

the ideal curve data sought. The search for the MSE

value is based on the error or difference between the

observed data and the ideal curve data which is

squared to avoid negative values (called SE or

squared error) and from all SE values the average is

sought so that the MSE value appears. The lower the

MSE value, the more similar the observation results

will be to the ideal curve.

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Figure 12: The result of plotting the mean breakdown

voltage over all experimental distances.

4.4 Polynomial Approach

In the polynomial approach, the Microsoft Excel

tool

is used after plotting the average breakdown

stress

over all distances. The tool in Microsoft Excel

is able

to display trend lines as well as their equations.

The

trend line that is formed can use one of several

types,

namely exponential, linear, logarithmic,

polynomial,

quadratic, and moving average. The only

curve that is

able to form a pattern close to the result

of plotting

the average breakdown stress is the

polynomial.

The 6th order polynomial approximation is shown

as in Fig. 13, which produces a line equation as in

Equation (2).

𝑉



=0.1168(pd)

- 2.5984

(

)

+ 23.461

(

p) (2)

=- 108.67

(

)

+ 264.42

(

)

Where

- 291.36

(

)

+ 329.26

= breakdown voltage (V)

p = gas pressure (Pa)

= distance between electrodes (m)

Visually, it can be seen that the polynomial

approach of the sixth order has been very detailed in

describing the Paschen Curve as shown in Fig.13

below.

Figure 13: Results of the order 6 polynomial approximation.

4.5 Paschen's Legal Approach

In the Paschen Law approach, the values A, B, and

γSE

are taken according to the results of previous

research. The γSE value is determined to be 1.32

according to the results of research on secondary

electron emission constants for copper metal (as the

electrode material used in this study) at a voltage of

240 V.

Meanwhile, the value of A as the gas ionization

constant was determined to be 16 Pa · m-1 and B as

the excitation constant and the ionization energy was

240 V · Pa · m-1, according to the experimental

results for argon gas. The next step is

to fill in the three

values while observing the shape of

the curve that

occurs. The following is the equation

of Paschen's

Law as in Equation (3).

𝑉

𝐵





(3)

Where:

VB = breakdown voltage (V)

A = gas ionization constant (Pa m-1)

B = excitation constant and ionization energy

(V Pa m-1)

γSE = secondary electron emission coefficient

p = gas pressure (Pa)

d = distance between electrodes (m)

In Fig. 14, the results of the Paschen's Law curve

approach are shown using a value of A of 16 Pa · m -

1, B of 240 V · Pa · m-1, and γSE of 1.32.

Fig. 14. shows the curve of the results of the

approach from Paschen's Law using an A value of 16

Pa · m-1, B of 240 V · Pa · m-1, and γSE of 1.32,

which results in an MSE value of 12,654.49. Some of

Paschen's Law theoretical curves fall below the graph

boundary line on the y-axis.

Breakdown

Voltage

(Volt)

The Effect of Electronic Disposition of Spherical Electrode on Plasma Behavior in Argon Gas Media

1465

Figure 14: Paschen's Law Approach with A = 16 Pa m-1, B

= 125 V Pa m-1, and γSE = 1.32, with a minimum

breakdown voltage limit of 200 V.

REFERENCES

Davidson, J. H. ( 2000). Recent Trends In Electrostatic

Precipitation. New York: McGraw-Hill Inc.

E., Kuffel, W.S., Saengl, J., Kuffel. (2000). High Voltage

Enggineering Fundamental. Published by Butterworth-

Heinemann. Typeset by Laser Words, Madras, India.

Iskander, M.F. ( 1992). Electromagnetic Fields and

Waves. New Jersey: Prentice Hall Inc.

Nur, Muhammad. ( 2011). Fisika Plasma dan

Aplikasinya. Universitas Diponegoro. Semarang.

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