[0001] The present invention relates to an exhaust apparatus and a vacuum pumping unit including
the exhaust apparatus, which are specifically adapted for discharging a gas in a vacuum
vessel to produce an ultrahigh vacuum in the semiconductor process or the like.
[0002] Fig. 10 conceptionally illustrates a prior art vacuum equipment including the high
vacuum pump, wherein a vacuum chamber 1 is connected to a vacuum pump 2 through an
exhaust pipe 3. The vacuum pump 2, which comprises, for example, a turbo molecular
pump, an oil diffusion pump, an ion pump and the like and, exhausts only the gas molecules
which fly into the exhaust pipe 3 from the vacuum chamber 1.
[0003] However, in the above-constructed vacuum equipment, when a turbo molecular pump is
used to exhaust a gas with a low compression ratio such as hydrogen, helium or the
like, gas molecules may diffuse back to a high vacuum side i.e. to the vacuum chamber
1 and, thus causes a decrease in vacuum level.
[0004] In the case of an oil diffusion pump, the gas molecules, which were once exhausted
by the pump, may flow back into the vacuum chamber and further, the vapor of pumping
oil heated also diffuses back. Thus vacuum level decreases.
[0005] In the case of the ion pump, gas molecules absorbed into a titanium wall of the pump
are desorbed and flow back into the vacuum chamber, thus reducing a vacuum level.
[0006] In the prior art, no effective means were available against the back diffusion of
gas molecules with a low compression ratio or desorbed gas molecules from the vacuum
pump. Nevertheless, oil vapor of the oil diffusion pump may be prevented only by providing
a cold trap with liquid nitrogen, however, complete prevention for any counterflow
has been substantially difficult.
[0007] The present invention has been carried out in view of the circumstances, and its
object is to provide an exhaust apparatus capable of obtaining a high degree of vacuum
by exhausting gas molecules in the vacuum chamber through ionization and acceleration
of the gas molecules.
[0008] Then, another object of the present invention is to provide a vacuum pumping unit
for an exhaust apparatus which is combined with an auxiliary pump set on a back pressure
side for the pumping unit. The vacuum pumping unit is capable of producing a high
degree of vacuum by ionization and acceleration of the gas molecules in a vacuum chamber
toward the auxiliary pump, and also by ionization and acceleration of gas molecules
which flow back from the auxiliary pump toward the auxiliary pump.
[0009] To achieve the above described objects, an exhaust apparatus according to a first
aspect of the present invention comprises: a vessel; means provided in said vessel
for ionizing gases in said vessel; and means provided in said vessel for accelerating
said ionized gases to discharge said gases out of said vessel.
[0010] An exhaust apparatus according to a second aspect of the present invention comprises:
a cathode; an electron accelerating grid surrounding the cathode; an outer electrode
surrounding the electron accelerating grid; an ion accelerating grid intersecting
the axis of the outer electrode and installed apart from the outer electrode; a vessel
for accommodating the grids and the electrodes; a magnet disposed outside of the vessel
for generating a magnetic field almost parallel to the axis of said outer electrode;
a high voltage power supply for applying a high voltage between said cathode and said
electron accelerating grid; a DC power supply for applying a voltage between said
electron accelerating grid and said outer electrode; and a DC power supply for applying
a voltage between said outer electrode and said ion accelerating grid so as to get
said outer electrode positive.
[0011] An exhaust apparatus according to a third aspect of the present invention comprises:
a cold cathode; a cylindrical electron accelerating grid surrounding the cold cathode;
an outer electrode surrounding the electron accelerating grid; an ion accelerating
grid intersecting an axis of the outer electrode and installed apart from the outer
electrode; a vessel for accommodating the grids and the electrodes; a magnet disposed
outside of the vessel for generating a magnetic field almost parallel to the axis
of said outer electrode; a high voltage power supply for applying a high voltage between
said cold cathode and said electron accelerating grid; a DC power supply for applying
a voltage between said electron accelerating grid and said outer electrode; and a
DC power supply for applying a voltage between said outer electrode and said ion accelerating
grid so as to get said outer electrode positive.
[0012] An exhaust apparatus according to a fourth aspect of the present invention comprises:
a cold cathode; an outer electrode surrounding the cold cathode; an ion accelerating
grid intersecting an axis of the outer electrode and installed apart from the outer
electrode; a vessel for accommodating the grid and the electrodes; a magnet disposed
outside of the vessel for generating a magnetic field almost parallel to the axis
of said outer electrode; a high voltage power supply for applying a high voltage between
said cold cathode and said outer electrode; and a DC power supply for applying a voltage
between said outer electrode and said ion accelerating grid so as to get said outer
electrode positive.
[0013] An exhaust apparatus according to a fifth aspect of the present invention comprises:
an outer electrode, a grid electrode intersecting an axis of the outer electrode and
installed apart from the outer electrode; a vessel for accommodating said outer electrode
and said grid electrode; a magnet provided outside of the vessel for generating a
magnetic field almost parallel to the axis of said outer electrode; and a DC power
supply for applying a high voltage between said outer electrode and said grid electrode
so as to get said grid electrode negative.
[0014] An exhaust apparatus according to a sixth aspect of the present invention comprises:
a first grid electrode; a second grid electrode installed opposite to the first grid
electrode; a vessel for accommodating the first and second grid electrodes; a magnet
provided outside of the vessel for applying a magnetic field intersecting said first
and second grid electrodes; and a DC power supply for applying a high voltage between
said first and second grid electrodes so as to get the second grid electrode negative.
[0015] An exhaust apparatus according to a seventh aspect of the present invention comprises:
a first grid electrode; a second grid electrode installed opposite to the first grid
electrode; a vessel for accommodating the two electrodes; coils or electrodes disposed
outside of the vessel and connected to a high frequency power supply; and a DC power
supply for applying a voltage between said first and second grid electrodes so as
to get the second grid electrode negative.
[0016] A vacuum pumping unit of the present invention is constituted by combining an optionally
selected vacuum pump with the high vacuum device according to one of the aspects of
the present invention described above.
[0017] With an exhaust apparatus of the present invention, a high vacuum is achieved since
the gas molecules within the vacuum vessel are ionized and accelerated. With a vacuum
pumping unit of the present invention, the gas molecules diffused back or desorbed
from the vacuum pump may be ionized and accelerated to be returned to the vacuum pump,
and at the same time the gas molecules in the vacuum vessel may be ionized and accelerated
to be actively fed into the vacuum pump. Thus the discharge efficiency should be improved
to achieve a high degree of vacuum in the vacuum vessel.
[0018] The above and other objects, features and advantages of the present invention will
become more apparent from the following description when taken in conjunction with
the drawings in which preferred embodiments of the present invention are shown by
way of illustrative examples.
Fig. 1 is a view showing a first embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 2 is a view showing a second embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 3 is a view showing a third embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 4 is a view showing a fourth embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 5 is a view showing a fifth embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 6 is a view showing a sixth embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 7 is a view showing a seventh embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 8 is a view showing a eighth embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
Fig. 9 is a view showing a ninth embodiment of the high vacuum device and the vacuum
pumping unit including the high vacuum device according to the present invention;
and
Fig. 10 is a view showing a conventional evacuating method.
[0019] High vacuum devices according to the present invention and vacuum pumping unites
including the high vacuum devices will now be described with reference to Fig. 1 through
Fig. 9.
[0020] Fig. 1 shows a first embodiment of the present invention in which numeral 50 denotes
an exhaust apparatus of the present invention and numeral 100 denotes a vacuum pumping
unit also of the present invention including the high vacuum device 50. Said vacuum
pumping unit 100 is constituted by combining the high vacuum device 50 and a vacuum
pump 31 provided on the back pressure side of the high vacuum device 50. The vacuum
pump 31 may be a turbo-molecular pump, an oil pump or an ion pump.
[0021] Said high vacuum device 50 includes a vessel 25 for connecting the vacuum pump 31
and a vacuum vessel 32 to be evacuated. A rod-like cold cathode 21 is disposed at
the center of the vessel 25, and an electron accelerating grid 22 is installed so
as to surround the cold cathode 21. Further, a cylindrical electrode 23 forming an
outer electrode is installed so as to surround the electron accelerating grid 22.
An ion accelerating flat grid 24 is disposed so as to intersect the axis of the cylindrical
electrode 23 and is installed apart from the cylindrical electrode 23.
[0022] On the other hand, an electromagnet 26 is disposed outside of the vessel 25 so as
to produce a DC magnetic field almost parallel to the axis of the cylindrical electrode
23. Further, three DC power supplies 28, 29, 30 are provided outside of the vessel
25 so that the output of each of the DC power supplies are applied to each components
21, 22, 23, 24 through vacuum tight terminals provided at a portion of the vessel
25. The DC high voltage power supply 29 applies a high DC voltage between the cold
cathode 21 and the electron accelerating grid 22. The ion accelerating DC power supply
30 applies a voltage between the cylindrical electrode 23 and the ion accelerating
grid 24 so as to get the ion accelerating grid 24 negative. Further, the DC power
supply 28 applies a voltage between the electron accelerating grid 22 and the cylindrical
electrode 23 so as to get the cylindrical electrode 23 negative, and thereby the electrons
are decelerated in the space.
[0023] The DC high voltage power supply 29 generates a discharge in gases between the cold
cathode 21 and the electron accelerating grid 22. Electrons generated in the discharge
are accelerated toward the electron accelerating grid 22 and obtain sufficient energy
to pass the electron accelerating grid 22. Since a magnetic field perpendicular to
the direction of electron's movement is applied between the electron accelerating
grid 22 and the cylindrical electrode 23, the electrons are caused to move toward
the cylindrical electrode 23 while moving in a circular path in the plane perpendicular
to the axis of the cylindrical electrode 23. Under the circular movement of the electrons,
the electrons' path toward the cylindrical electrode 23 is greatly lengthened, whereby
they collide with a lot of gas molecules and a large amount of ions are generated.
The generated ions are accelerated toward the ion accelerating grid 24 and pass through
the grid 24 to be captured by the vacuum pump 31 for exhaustion.
[0024] It should be noted that, high speed electrons have a relatively smaller cross section
of collision with the gas molecules which lowers ionization efficiency for gases.
In the present invention, however, since an electric field for decelerating electrons
is applied by the DC power supply 28 between the electron accelerating grid 22 and
the cylindrical electrode 23, the electrons are gradually decelerated between the
components 22, 23, the cross section with the gas molecules increases and ionization
occurs effectively. Further, while it is difficult to generate discharge between the
cold cathode 21 and the electron accelerating grid 22 when the gas pressure is lowered,
discharge may be continued under the presence of the magnetic field created by the
electromagnet 26 and pumping effect is maintained even when the gas pressure in the
vessel 25 is lowered.
[0025] Further, in the case where the DC power supply 28 is removed to bring the cylindrical
electrode 23 and the electron accelerating grid 22 to the same potential, those electrons
which have passed the electron accelerating grid 22 by obtaining a large kinetic energy
lose their speed and are reversed when they have reached the cylindrical electrode
23. They are started to be accelerated again toward the electrode accelerating grid
22, repeating collision with gas molecules to generate ions.
[0026] In this way, gas in the vacuum vessel 32 and the molecules which are diffused back
or desorbed from the vacuum pump 31, which become the cause of the reduction in the
degree of vacuum, are ionized and accelerated by the high vacuum device according
to the present invention to be returned again to the vacuum pump 31. Thus a high degree
of vacuum may be achieved. Further, if only the vacuum pump 31 is used, only those
gas molecules having entered the exhaust hole are exhausted. However, since the high
vacuum device of the present invention is jointly used to actively ionize and to accelerate
the gas molecules to feed them into the vacuum pump 31, the discharging efficiency
is improved and a high degree of vacuum is achieved.
[0027] It should be noted that, the power supply 28 may also be variable so that the potential
at the cylindrical electrode 23 is adjusted to the best point for the discharging
efficiency of the pump. In this way, a high degree of vacuum may be achieved.
[0028] A second embodiment of the high vacuum device and the vacuum pumping unit including
the high vacuum device according to the present invention will now be described with
reference to Fig. 2. In Fig. 2, those components having the same effects and functions
as those components in Fig. 1 are denoted by the same reference numerals and description
thereof will be omitted.
[0029] A rod-like cold cathode 21 is disposed at the center of the vessel 25, and a cylindrical
electrode 23 forming the outer electrode surround the cold cathode 21. Further, an
ion accelerating grid 24 is disposed so as to intersect the axis of the cylindrical
electrode 23 and installed apart from the cylindrical electrode 23.
[0030] Further, an electromagnet 26 is disposed outside of the vessel 25. The electromagnet
26 is arranged to produce a DC magnetic field almost parallel to the axis of the cylindrical
electrode 23.
[0031] A DC high voltage power supply 29 for discharge applies a DC high voltage between
the cold cathode 21 and the cylindrical electrode 23. The ion accelerating DC power
supply 30 applies a voltage between the cylindrical electrode 23 and the ion accelerating
grid 24 so as to get the ion accelerating grid 24 negative.
[0032] Operation will now be described of the high vacuum device constructed as described
above and of the vacuum pumping unit including the high vacuum device.
[0033] The DC high voltage power supply 29 makes a discharge between the cold cathode 21
and the cylindrical electrode 23. Electrons generated by the discharge are accelerated
toward the cylindrical electrode 23. Since a magnetic field is applied by the electromagnet
26 orthogonally to the electron's movement in the space between the cold cathode 21
and the cylindrical electrode 23, the electrons move toward the cylindrical electrode
23 in circular paths within a plane perpendicular to the central axis of the cylindrical
electrode 23. Under the circular movement, the electrons' path toward the cylindrical
electrode 23 is greatly lengthened and they collide with a lot of gas molecules to
generate a large amount of ions. The generated ions are accelerated toward the ion
accelerating grid 24 and captured by the vacuum pump 31.
[0034] A third embodiment of the high vacuum device and the vacuum pumping unit including
the high vacuum device according to the present invention will now be described with
reference to Fig. 3. In Fig. 3, those components having the same effects and functions
as those components in Fig. 1 are denoted by the same reference numerals and description
thereof will be omitted.
[0035] In the vessel 25, a flat plate-like grid electrode 24 is installed apart from the
cylindrical electrode 41. Further, an electromagnet 26 is disposed outside of the
vessel 25 in a similar arrangement as in the embodiment shown in Fig. 1.
[0036] A DC high voltage power supply 42 applies potential between the cylindrical electrode
41 and the grid electrode 24 so as to get the grid electrode 24 negative.
[0037] Operation will now be described of the high vacuum device constructed as described
above and of the vacuum pumping unit including the high vacuum device. A discharge
occurs between the cylindrical electrode 41 and the grid electrode 24 by the DC high
voltage power supply 42 to generate a great amount of ions. The ions are accelerated
toward the grid electrode 24 and pass through the grid electrode 24 to be captured
by the vacuum pump 31. The electromagnet 26 has the effect of lengthening orbit of
the electrons so that discharge is continued to maintain the pumping effect even when
the gas pressure in the vessel 25 is lowered and the degree of vacuum increases.
[0038] A fourth embodiment of the high vacuum device and the vacuum pumping unit including
the high vacuum device according to the present invention will now be described with
reference to Fig. 4. In Fig. 4, those components having the same effects and functions
as those components in Fig. 1 are denoted by the same reference numerals and description
thereof will be omitted.
[0039] In the vessel 25, a cylindrical electrode 41 is disposed in a similar arrangement
as in the embodiment of Fig. 3, and a grid electrode 24 is installed apart from the
cylindrical electrode 41. A high frequency power supply 43 and a DC power supply 44
apply their output between the cylindrical electrode 41 and the grid electrode 24.
The DC power supply 44 is connected so as to get the grid electrode 24 negative. The
operation of the present embodiment is as follows.
[0040] A discharge occurs between the cylindrical electrode 41 and the grid electrode 24
by the high frequency power supply 43 to generate a large amount of ions. These ions
are accelerated by the DC power supply 44 toward the grid electrode 24 and pass through
the grid electrode 24 to be captured by the vacuum pump 31. The electromagnet 26 has
the effect of lengthening the orbit of the electrons so that discharge is continued
to maintain the pumping effect even when the gas pressure in the vessel 25 is lowered
and the degree of vacuum increases.
[0041] Fig. 5 shows a fifth embodiment of the high vacuum device and the vacuum pumping
unit including the high vacuum device according to the present invention. In this
figure, those components having the same effects and functions as those components
in Fig. 1 are denoted by the same reference numerals and description thereof will
be omitted.
[0042] In the vessel 25, a grid electrode 51 and a grid electrode 24 are installed opposite
to each other. A DC high voltage power supply 42 is connected between the two grid
electrodes 51, 24 so as to get the grid electrode 24 negative. The operation of the
present embodiment is as follows.
[0043] A discharge occurs between the grid electrode 51 and the grid electrode 24 by the
high voltage DC power supply 42 to generate a large amount of ions. The ions are accelerated
toward the grid electrode 24 and pass through the grid electrode 24 to be captured
by the vacuum pump 31. The electromagnet 26 has the effect of lengthening the orbit
of the electrons so that the discharge is continued to maintain the pumping effect
even when the gas pressure in the vessel 25 is lowered and the degree of vacuum increases.
[0044] Fig. 6 shows a sixth embodiment of the high vacuum device and the vacuum pumping
unit including the high vacuum device according to the present invention. In this
figure, those components having the same effects and functions as those components
in Fig. 1 are denoted by the same reference numerals and description thereof will
be omitted.
[0045] In the vessel 25, a grid electrode 51 and a grid electrode 24 are installed opposite
to each other. A high frequency power supply 43 and a DC high voltage power supply
44 are connected between the two grid electrodes 51, 24. The DC power supply 44 is
connected so as to get the grid electrode 24 negative. The operation of the present
embodiment is as follows.
[0046] A discharge occurs between the grid electrode 51 and the grid electrode 24 by the
high frequency power supply 43 to generate a large amount of ions. The ions are accelerated
by the DC power supply 44 toward the grid electrode 24 and pass through the grid electrode
24 to be captured by the vacuum pump 31. The electromagnet 26 has the effect of lengthening
the orbit of the electrons so that discharge is continued to maintain the pumping
effect even when the gas pressure in the vessel 25 is lowered and the degree of vacuum
increases.
[0047] In the embodiments shown in from Fig. 1 to Fig. 6, ions are produced by the collision
between the gas molecules and the electrons generated through cold cathode discharge.
As another method for gas ionization, a heat filament may be disposed in the vicinity
of the cold cathode 21 of the first and second embodiments (see Fig. 1, Fig. 2), or
installed between the grid electrode 24 and the cylindrical electrode 41 of the third
and fourth embodiments (see Fig. 3, Fig. 4) or between the grid electrode 24 and the
grid electrode 51 of the fifth and sixth embodiments (see Fig. 5, Fig. 6). When the
filament is heated to emit thermoelectrons, the electrons trigger discharge so as
to start the high vacuum device.
[0048] Fig. 7 shows a seventh embodiment of the present invention in which numeral 50 denotes
an exhaust apparatus of the present invention and numeral 100 denotes a vacuum pumping
unit also of the present invention using the high vacuum device 50. Said vacuum pumping
unit 100 is constituted by combining the high vacuum device 50 and a vacuum pump 31
provided on the back pressure side of the high vacuum device 50.
[0049] Said high vacuum device 50 includes a vessel 25 for connecting the vacuum pump 31
and a vacuum vessel 32 to be evacuated. The vessel 25 is cylindrical or rectangular
in cross section and is made of a glass or ceramic. In the vessel 25, a flat plate-like
ion collecting or attracting grid 24 and a flat plate-like grid electrode 51 are installed
opposite to each other.
[0050] A DC power supply 30 is connected so as to get the ion collecting grid 24 negative
with respect to the grid electrode 51. Further, a coil 21A is installed outside of
the vessel 25 so as to surround the vessel 25. A high frequency power supply 43 is
connected to the coil 21 A.
[0051] The vacuum pump 31 may be a turbo-molecular pump, an oil pump or an ion pump.
[0052] Operation will now be described of the high vacuum apparatus constructed as described
above and of a vacuum pumping unit using such high vacuum apparatus.
[0053] A high frequency current flows through the coil 21A by the high frequency power supply
43, and discharge occurs between the grid electrode 51 and the ion collecting grid
24 by the inductive coupling phenomenon which generates a large amount of ions. A
pumping effect is achieved such that the ions are accelerated toward the ion collecting
grid 24 by the DC power supply 30 and pass through it to be captured by the vacuum
pump 31.
[0054] It should be noted that the output of the power supply 30 is transmitted to the components
24 and 51 through vacuum tight terminals provided at a portion of the vessel 25.
[0055] In this way, gas molecules in the vacuum vessel 32 are ionized and accelerated by
the high vacuum device of the invention to be actively fed to the vacuum pump 31 and
at the same time the molecules which are diffused back or desorbed from the vacuum
pump 31. Thus a high degree of vacuum may be achieved.
[0056] A eighth embodiment of the high vacuum device and the vacuum pumping unit including
the high vacuum device according to the present invention will now be described with
reference to Fig. 8. In Fig. 8, those components having the same effects and functions
as those components in Fig. 7 are denoted by the same reference numerals and description
thereof will be omitted.
[0057] A pair of plate-like electrodes 22A are provided outside of the vessel 25 in contact
with the outer wall of the vessel 25 opposite to each other. And a high frequency
power supply 43 is connected to the pair of plate-like electrodes 22A. For the other
portions, the construction is the same as the construction in Fig. 7. Operation of
the present embodiment is as follows.
[0058] A high frequency voltage is applied to the electrodes 22A by the high frequency power
supply 43. Discharge by the capacitive coupling phenomenon between the grid electrode
51 and the ion collecting grid 24 makes a large amount of ions. Thus, in a similar
manner as in the case of Fig. 7, a pumping effect is achieved such that the ions are
accelerated toward the ion collecting grid 24 by the DC power supply 30 and pass through
it to be captured by the vacuum pump 31.
[0059] Fig. 9 shows a ninth embodiment of the high vacuum device and the vacuum pumping
unit including the high vacuum device according to the present invention. In this
figure, those components having the same effects and functions as those components
in Fig. 7 are denoted by the same reference numerals and description thereof will
be omitted.
[0060] The present embodiment is constructed by adding a heat filament to the seventh embodiment
(see Fig. 7). That is, a heat filament 26 is disposed in the vicinity of the grid
electrode 51 and a heating power supply 27 is connected to the heat filament 26.
[0061] In the seventh and eighth embodiments (see Fig. 7, Fig. 8), ions are produced by
bombardment of the electrons generated in discharge that is induced by inductive coupling
of a high frequency magnetic field or capacitive coupling of a high frequency electric
field. If however an attempt is made to start these high vacuum devices in the condition
where the pressure is low, there occurs a problem that the discharge is difficult
to be generated. To avoid this, a heat filament 26A is provided between the ion collecting
grid 24 and the grid electrode 51, and is heated by a power supply 27 to emit thermoelectrons.
These electrons trigger discharge.
[0062] As is apparent from the foregoing description, according to an exhaust apparatus
of the present invention, a high vacuum may be achieved in a vacuum vessel by ionizing
and accelerating the gas molecules within the vacuum vessel for discharge. Further,
according to a vacuum pumping unit of the present invention, those gas molecules diffused
back or desorbed from the vacuum pump may be ionized and accelerated to be returned
to the vacuum pump. At the same time the gas molecules in the vacuum vessel may be
ionized and accelerated so that they are actively fed into the vacuum pump. Thus the
discharge efficiency may be improved to achieve a high degree of vacuum in the vacuum
vessel. Furthermore, in the case of using an oil diffusion pump as the vacuum pump,
there is no need for jointly using a cold trap by means of liquid nitrogen. A reduction
in costs may thus be achieved and, because of the fact that problems associated with
supplying liquid nitrogen are eliminated, prolonged operation will be possible.
1. An exhaust apparatus comprising:
a vessel;
means provided in said vessel for ionizing gases in said vessel; and
means provided in said vessel for accelerating said ionized gases to discharge said
gases out of said vessel.
2. An exhaust apparatus comprising: a cathode; an electron accelerating grid surrounding
the cathode; an outer electrode surrounding the electron accelerating grid; an ion
accelerating grid intersecting the axis of the outer electrode and installed apart
from the outer electrode; a vessel for accommodating the grids and the electrodes;
a magnet disposed outside of the vessel for generating a magnetic field almost parallel
to the axis of said outer electrode; a high voltage power supply for applying a high
voltage between said cathode and said electron accelerating grid; a DC power supply
for applying a voltage between said electron accelerating grid and said outer electrode;
and a DC power supply for applying a voltage between said outer electrode and said
ion accelerating grid so as to get said outer electrode positive.
3. An exhaust apparatus of Claim 2, wherein the DC power supply connected between
said electron accelerating grid and said outer electrode is removed to equalize potentials
at said electron accelerating grid and said outer electrode.
4. An exhaust apparatus of Claim 2, wherein the DC power supply for applying a voltage
between said electron accelerating grid and said outer electrode generates a variable
output.
5. An exhaust apparatus comprising: a cold cathode; an electron accelerating grid
surrounding the cold cathode; an outer electrode surrounding the electron accelerating
grid; an ion accelerating grid intersecting the axis of the outer electrode and installed
apart from the outer electrode; a vessel for accommodating the grids and the electrodes;
a magnet disposed outside of the vessel for generating a magnetic field almost parallel
to the axis of said outer electrode; a high voltage power supply for applying a high
voltage between said cold cathode and said electron accelerating grid; a DC power
supply for applying a voltage between said electron accelerating grid and said outer
electrode; and a DC power supply for applying a voltage between said outer electrode
and said ion accelerating grid so as to get said outer electrode positive.
6. An exhaust apparatus of Claim 5, wherein the DC power supply connected between
said electron accelerating grid and said outer electrode is removed to equalize potentials
at said electron accelerating grid and said outer electrode.
7. An exhaust apparatus of Claim 5, wherein the DC power supply for applying a voltage
between said electron accelerating grid and said outer electrode generates a variable
output.
8. An exhaust apparatus of Claim 5, wherein the electron accelerating grid surrounds
the cold cathode.
9. An exhaust apparatus of Claim 5, wherein the outer electrode surrounds the electron
accelerating grid.
10. An exhaust apparatus comprising: a cold cathode; an outer electrode surrounding
cold cathode; an ion accelerating grid crossing the axis of the outer electrode and
installed apart from the outer electrode; a vessel for accommodating the grid and
the electrodes; a magnet disposed outside of the vessel for generating a magnetic
field almost parallel to the axis of said outer electrode; a high voltage power supply
connected between said cold cathode and said outer electrode; and a DC power supply
connected between said outer electrode and said ion accelerating grid so as to get
said outer electrode positive.
11. An exhaust apparatus of Claim 5 or 10, wherin the cold cathode is a rod-like cold
cathode.
12. An exhaust apparatus of Claim 5 or 10, wherin the cold cathode is disposed at
the center of the vessel.
13. An exhaust apparatus of Claim 10, wherein the outer electrode surrounds the cold
cathode.
14. An vacuum pumping unit comprising: an optionally selected vacuum pump; and an
exhaust apparatus of any one of Claims 1-36 provided between the vacuum pump and a
vessel to be evacuated.
15. An exhaust apparatus comprising: an outer electrode; a grid electrode crossing
the axis of the outer electrode and installed apart from the outer electrode; a vessel
for accommodating said outer electrode and said grid electrode; a magnet provided
outside of the vessel for generating a magnetic field almost parallel to the axis
of said outer electrode; and a DC power supply connected between said outer electrode
and said ion accelerating grid so as to get said outer electrode positive.
16. An exhaust apparatus of Claim 28, wherein a high frequency power supply is overlaid
upon the DC power supply provided between said outer electrode and said grid electrode.
17. An exhaust apparatus of any of Claims 1-36, wherein the outer electrode is a cylindrical
electrode.
18. An exhaust apparatus of any of Claims 1-36, wherein the ion accelerating grid
is disposed so that it orthogonally crosses the axis of the outer electrode.
19. An exhaust apparatus of any of Claims 1-36, wherein the ion accelerating grid
is a plate-like grid.
20. An exaust apparatus of any of Claims 1-36, wherein the vessel forms a structure
which serves as an exhaust hole of a vessel to be evacuated by the high vacuum device
or a structure which is in communication with the exhaust hole of the vacuum vessel.
21. An exhaust apparatus of any of Claims 1-36, wherein a heat filament for emitting
thermoelectrons is disposed between the grid electrode and the outer electrode.
22. A vacuum pumping unit comprising: an optionally selected vacuum pump; and an exhaust
apparatus of any one of Claims 1 to 34 provided between the vacuum pump and a vessel
to be evacuated.
23. An exhaust apparatus comprising: a first grid electrode; a second grid electrode
installed opposite to the first grid electrode; a vessel for accommodating the first
and second grid electrodes; a magnet provided outside of the vessel for applying a
magnetic field in a crossing direction with respect to said first and second grid
electrodes; and a DC power supply for applying a high voltage between said first and
second grid electrodes so as to get the second grid electrode negative.
24. An exhaust apparatus of Claim 23, wherein a high frequency power supply is overlaid
upon the DC power supply provided between said first and second grid electrodes.
25. An exhaust apparatus of Claim 23, wherein the first and second grid electrodes
are plate-like electrodes.
26. An exhaust apparatus of Claim 23, wherein the vessel forms a structure which serves
as an exhaust hole of a vessel to be evacuated by the high vacuum device or a structure
which is in communication with the exhaust hole of the vacuum vessel.
27. An exhaust apparatus of Claim 23, wherein a heat filament for emitting thermoelectrons
is disposed between the first grid electrode and the second grid electrode.
28. A vacuum pumping unit comprising: an optionally selected vacuum pump; and an exhaust
apparatus of any one of Claims 1 to 36 provided between the vacuum pump and a vessel
to be evacuated.
29. An exhaust apparatus comprising: a grid electrode; a second grid electrode installed
opposite to the first grid electrode; a vessel for accommodating the two electrodes;
a coil disposed outside of the vessel and connected to a high frequency power supply;
and a DC power supply for applying a high voltage between said first and second grid
electrodes so as to get the second grid electrode positive.
30. An exhaust apparatus of Claim 29, wherein said vessel is made of glass or ceramic.
31. An exhaust apparatus of Claim 29, wherein said first and second grid electrodes
are plate-like electrodes.
32. An exaust apparatus of Claim 29, further comprising a heat filament provided between
the first and second grid electrodes and a heating power supply connected to the heat
filament for emitting thermoelectrons from said heat filament.
33. An exhaust apparatus comprising: a first grid electrode; a second grid electrode
provided opposite to the first grid electrode; a vessel for accommodating the two
electrodes; electrode means provided at the outside of the vessel and connected to
a high frequency power supply and a DC power supply for applying a high voltage between
said first and second grid electrodes so as to get the second grid electrode positive.
34. An exhaust apparatus of Claim 33, wherein said electrode means is a pair of plate-like
electrodes in contact with the outer wall of the vessel and installed opposite to
each other.
35. An exhaust apparatus of Claim 33, further comprising a heat filament provided
between the first and second grid electrodes and a power supply connected to the heat
filament for emitting thermoelectrons from said heat filament.
36. A high vacuum pumping unit comprising: a vacuum pump optionally selected; and
a high vacuum apparatus as claimed in any one of Claims 1 to 36 provided between said
vacuum pump and a vessel to be evacuated.