Gas discharge device

The invention relates to a plasma technique, and can be used for generation of beams of charged particles, for instance, ions, in technological goals and in the space electric propulsion installations. Gas discharge device comprises an axially symmetric chamber with at least one face wall, a HF power input unit and a magnetic system providing the generation of stationary non-uniform magnetic field inside the chamber. The induction of magnetic field decreases not only in the radial direction towards the chamber axis of symmetry but also in the longitudinal direction towards the face part of the chamber opposite to the area of HF power input unit arrangement. The invention is characterized in that the HF power input unit is fabricated as conductor of zigzag recurrent symmetric shape and is located on the lateral and face walls of the chamber comprising the region of plasma generation and in that the horizontal size of the chamber exceeds its longitudinal size.

TECHNICAL FIELD 
The invention relates to a plasma technique, and can be used for generation 
of the charged particles flows, for instance, ions, in ground technologies 
and in ion engines of space installations. 
BACKGROUND ART 
The known gas discharge device (GB, A, 1399603, HO1J27/00, 1072) consists 
of an axially symmetric chamber with two face walls, one of which is 
fabricated partially transparent, a magnetic system producing inside the 
chamber a stationary non-uniform magnetic field and a HF power input unit 
connected to the HF generator. The HF power input unit is formed by at 
least two conductors of current. 
Plasma generation in the known device is conducted by excitation in plasma 
waves in itself. In this case the effective HF power input in plasma is 
provided and satisfactory values of ionization coefficient are achieved at 
sufficiently low specific energy expenditures for ionization. 
Resonance absorption of the input power occurs at the gas pressures 
(0.015-1.5 Pa) and values of magnetic field induction B less than 0.1 T1. 
However, under said conditions the plasma density increases considerably 
due to the decrease of the gas of the gas discharge device. 
It is also known the gas discharge device (RU, application 95110327/07, 
published 10.08.96) which consists of a magnetic system producing in the 
discharge chamber a stationary axially-symmetric non-uniform magnetic 
field of which a magnetic induction decreases to the chamber axis of 
symmetry. The HF power input unit is formed by several conductors of 
current, for instance in the form of n-pole capacitor and is adapted for 
excitation of longitudinal irrotational electrical component of HF field 
in the chamber. 
This construction gives an opportunity to excite plasma waves in itself by 
choosing the maximum value of magnetic field induction in the range from 
0.01 to 0.05 TI and HF in the range from 40 to 100 MHZ. Resonance 
excitation of plasma waves in itself under said conditions gives an 
opportunity to increase an energy and gas efficiency of the gas discharge 
device. 
The closest prototype of the invention is gas discharge device (GB, A, 
2235086, HO1J 27/16,1991), consisting of a cylindrical chamber with one 
open face wall, a HF power supply unit formed with several conductors of 
current, which is located symmetrically on the lateral surface of the 
chamber, and a magnetic system providing in the chamber the stationary 
magnetic field of which the magnetic induction decreases not only in the 
radial direction towards the chamber axis of symmetry but also in the 
longitudinal direction from the position of power input unit. 
The known gas discharge device gives an opportunity to increase the 
efficiency of the power input due to the choice of the optimal magnetic 
field configuration a nd the construction of the power input unit. 
However all above mentioned devices do not provide the full utilization 
(for ionization of the working body) of the input power. 
DISCLOSURE OF THE INVENTION 
The present invention is aimed to provide an increase of energy and gas 
efficiency of gas discharge devices of the described type and thus 
decreases expenditures for generating plasma with the given parameters. 
The noticeable technical result is as follows: Gas discharge device 
comprising an axially symmetric chamber at least having one face wall, an 
HF power input unit for inputting the HF power to the chamber, coaxially 
arranged on the exteral wall of the chamber, and a magnetic system for 
providing a stationary magnetic field of which the magnetic induction 
decreases not only in the radial direction towards the chamber axis of 
symmetry but also in the longitudinal direction from the area in which the 
HF power input unit is located inside the chamber, characterized in that 
the HF power input unit is fabricated as an conductor of zigzag recurrent 
symmetric shape arranged on the face wall and lateral wall of the chamber, 
and in that the magnetic system is adjusted to generate the magnetic field 
of which the magnetic induction decreases in the longitudinal direction 
towards the face part of the chamber opposite to the area where the HF 
power input unit is arranged. 
In order to increase gas efficiency of the device it is worth to use the 
chamber of which a horizontal dimension is larger than longitudinal. 
It is worth to provide the chamber with gas distributor arranged on its 
face surface from the side of the HF power input unit arrangement. 
Gas discharge device can be accommodated by the assembling flange where the 
chamber is fixed. In this case air-tight gaskets for electrical terminals 
of the HF power input unit and for a gas distributor, and also-an elements 
of plug connection for fixing an assembling flange to an adjusting flange 
of the vacuum chamber are mounted on the assembling flange. 
It is advisable to fabricate air-tight gaskets as two bolsters with 
obturator collar between the bolsters, and obturator blot, arranged 
coaxially with one of the bolsters.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS 
The gas discharge device according to the invention can be used as a 
component of different technological installations with some 
modifications, for example, as a component of plasma chemical reactors and 
ion beam installations as well as a part of electric propulsion systems. 
The gas discharge device according to the invention which is realized as a 
part of ion beam installation will be described in the following with 
reference to the accompanying drawing. The installation (see FIG. 1) 
comprises a chamber 1 as an axially symmetric bulb, a HF antenna 2, to be 
the HF power input unit, an ion optic system, consisting of two 
electromagnetic reels 6, gas inlet 7, air-tight gaskets 8 of electrical 
terminals of HF antenna 2 and electrodes 3, 4 and 5, an air-tight gasket 9 
of gas inlet 7, assembling flange 10 and adjusting flange 11. 
Antenna 2 to be the HF power input unit is fabricated as a conductor of 
zigzag, recurrent symmetric shape one part of which is located on the 
lateral wall of the chamber (see FIG. 1) and the other part of which is 
located on the face wall of the chamber 1 (see FIG. 2). 
The output face part of the chamber 1 is located in the area of decreasing 
magnetic field produced with the help of electromagnetic reels 6 (see FIG. 
1). 
The walls of the chamber 1 are fabricated from dielectric material but it 
is worth to mention that dielectric material can be used for manufacturing 
only the part of the walls of the chamber 1 situated in the area of the HF 
antenna 2 location. 
The size of the chamber 1 along its longitudinal axis of symmetry is equal 
to the radius of the internal cylindrical surface of its lateral wall. 
Each air-tight gasket 8 or 9 (see FIG. 3) contains two bolsters 12 made 
from fluoride layer with obturator collar between them, made from rubber. 
The air tight gaskets are crunched by special crunching bolts 14, adjusted 
thruthly with bolsters 12. 
The operation of the installation is conducted in the following way. 
The working gas-argon is supplied to the chamber 1 through the gas inlet 7. 
In the chamber 1 with the help of electromagnetic reels 6 it is provided 
the axially symmetric non-uniform magnetic field which induction decreases 
in the radial direction towards the chamber axis of symmetry and in the 
longitudinal direction from the area where the HF power input unit is 
located towards the opposite face part of the chamber 1 where the ion 
optic system is located. 
The given distribution of magnetic field in the chamber 1 can be provided 
with the help of different facilities, known to specialists in this field 
of techniques. 
After supplying of argon to the chamber 1 is accomplished with the help of 
antenna 2, fabricated as a conductor of zigzag shape comprising face and 
lateral walls of the chamber in the region of the presence of the magnetic 
field of the given configuration. 
Under the action of the electrical component of the HF field in the 
discharge volume of the chamber the HF discharge is ignited and plasma is 
formed. 
The increase of the efficiency of the HF power input and consequently the 
increase of the charged particles density and plasma temperature in the 
said device is provide is provided by localization of the magnetic field 
in the area of HF fields generation produced by the antenna 2 of the 
special configuration. 
It was found experimentally that the increase of the energy and gas 
efficiency of the ions generation in the chamber 1 and ion source as a 
whole in comparison with the closest prototypes can be achieved only in 
the case of HF power input unit fabrication in the form of conductor of 
zigzag recurrent symmetric shape comprising the face wall of the chamber 1 
in the area of the maximal induction of magnetic field decreasing towards 
the chamber axis of symmetry. 
In case of utilization argon as working gas the frequency of the generated 
HF field is chosen in the range from 10 to 100 MHZ, maximal value of 
stationary magnetic filed is chosen in the range from 0.01 to 0.1 T1, and, 
the value of the input HF-in the range from 20 to 200 W in dependence on 
required plasma density and density of extracted ion current. 
Extraction and forming of the ion beam in the considered modification of 
the ion source is carried out with the help of ion extraction system, 
consisting of three electrodes and realizing the principle "acceleration 
deceleration". 
Between the generated gas discharge plasma of which the potential is et by 
the emission electrode 3 and accelerating electrode 4 and grounded 
electrode 5 the electrical field is created to extract ions and form ion 
beam with a given ion current density (0.2-2 mA/cm.sup.2). 
In order to provide the possibility of getting out the gas discharge device 
from the vacuum chamber independently from the other elements of the ion 
source construction, the chamber 1 is fixed on the demountable assembling 
flange 11. Magnetic system and ion-optic system are mounted on the 
adjusting flange 10 of the vacuum chamber. 
The demountable air-tight gaskets 8 of electrical terminals of power input 
unit and the air-tight gasket of the gas inlet are mounted on the 
assembling flange. 
Demounting of the chamber 1, for example while conducting technological 
work, is carried out by resolution of the assembling flange 11 from the 
adjusting flange 10 of the vacuum chamber with the help of plug connection 
(not shown of the Figure). 
Resolution of the chamber 1 from the assembling flange 11 is conducted 
after demounting of the demountable air-tight gaskets 8 and 9. To do it 
the crunching bolts 14 is unscrewed from the aperture in the flange 11, 
the external fluoride layered bolster 14 is taken out, rubber collar 13 
and internal fluoride layered bolster 12 are taken out coherently. After 
demounting of all air-tight gaskets, the assembling flange 11 is set free 
from electrical terminals of HF antenna 2 and from gas inlet 7. 
The above described arrangement of the antenna 2 (HF power input unit into 
the chamber 1) on the chamber 1 and the utilization of magnetic system 
adjusted for generation of the stationary non-uniform magnetic field with 
given gradient in the place of the antenna 2 give an opportunity to 
provide effective HF power into generated magnitoactive plasma which can 
be characterized by the value of the specific power expenditures for the 
generation of the ion beam with the current of 1 Amp. 
For the considered modification of the realization of the being patented 
invention as a component of the ion source the achieved value of specific 
energy expenditures does not exceed 450 W/A at the extracted ion beam 
current density ranging from 0.2 to 2 mA/cm.sup.2. 
Thus, the gas discharge device being patented gives the opportunity to 
increase the efficiency of plasma generation which is characterized for 
this kind of devices by energy and gas efficiency in the given range of 
operation parameters. 
INDUSTRIAL APPLICATION 
In accordance with the invention the gas discharge device can be used in 
technological ion-beam installations assigned for manufacturing 
microelectronic and optical devices, in plasma-chemical reactors and in 
space technique as a component of electric propulsion. 
In spite of the fact that the invention is described in relation to the 
preferred way of realization it is clear for specialists in this field of 
technique that changes and other kinds of utilization can take place 
without deviation from the general idea and the subject of invention. 
These changes and modifications are considered not to go out from the 
frames of the rights asserted by the applied claims.