JPH0138512Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to improvements in Penning vacuum gauges.

A Penning vacuum gauge is widely used as a vacuum measuring device used in electron microscopes and the like, and its structure is shown in FIG. 1 and FIG. 2, which is a view of FIG. 1 from the direction A-A'. In the figure, reference numeral 1 indicates a tubular member as a cathode, and recesses 2 and 3 are provided at two outside locations of the member 1. Two permanent magnets 4 and 5 are fitted into the recesses 2 and 3. The magnets 4 and 5 form a vertical magnetic field B inside the tubular member 1. A connecting tube 8 for connecting to another vacuum container is attached to one open end of the tubular member 1 using an O-ring 6 and screws 7, and a connecting tube 8 for connecting to another vacuum container such as an electron microscope is connected through a communication port 8a. It communicates with An O-ring 9 and a screw 10 are attached to the other open end of the tubular member 1.
A cover 11 is attached to the cover 11 through an electrically insulating element 12, and an anode 13 consisting of a short cylindrical ring as shown in FIG. 3 is inserted into the magnetic field B. It is installed so that The output of a DC high voltage power supply 14, which is a constant voltage power supply, is applied to the anode 13, and the current flowing through the power supply 14 is measured by an ammeter 15, which has various resistance values and A shunt circuit 15' composed of a selection switch is connected. The current measured by the ammeter 15 is
The pressure is converted and displayed up to 10 ^-6 Torr.

The Penning vacuum gauge with the above configuration is 10 ^-3 ~
Used to measure pressures around 10 ^-6 Torr,
When a high voltage of several kilovolts is applied between the anode 13 and the tubular member 1 as a cathode by the high voltage power supply 14, electrons are emitted from the opposing surface 1a of the anode 13 of the tubular member 1 by cold cathode emission. These electrons ionize the gas molecules in the vacuum chamber 16 while spirally moving due to the magnetic field B formed by the magnets 4 and 5, and as shown by the broken line A in the graph of FIG.
The discharge current is several hundred μA. The degree of vacuum is measured by measuring this discharge current with an ammeter 15 and converting the current into pressure.

By the way, in the above-mentioned conventional Penning vacuum gauge, the anode 13 uses a single cylindrical anode as shown in FIG. 10 ^-3 Torr
In this case, a discharge current of about 800 to 900 μA flows,
At 10 ^-6 Torr, the discharge current is 5 to 50 μA, and at 10 ^-7 Torr
There is almost no flow. Therefore, conventional equipment
When measuring pressures below 10 ^-7 Torr, install multiple anodes to increase the discharge current, or
Or it was necessary to make the anode larger. However, if multiple anodes are used or the anode is made larger and measurements are taken using a conventional high-voltage power supply,
As shown by the solid line (b) in Figure 4, the discharge current near 10 ^-7 Torr increases and becomes measurable, but when it reaches 10 ^-3 to
The discharge current around 10 ^-4 Torr stopped changing much, making it difficult to measure the pressure around this area. Therefore, in order to be able to measure the range around 10 ^-3 to 10 ^-4 Torr, the high voltage power supply 14 should be connected to the fourth
This has the disadvantage that it requires a large capacity power source that can supply the current shown by the dashed line C in the figure, making the device expensive.

The present invention was developed in view of the above points, and involves applying the output of a constant voltage power source between the anode and the ground electrode placed in the measurement space and measuring the output current.
The apparatus for converting the measured output into pressure and displaying it is characterized by comprising means for displaying the measured output current in different converted pressures in response to replacement or switching of the anode.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 5 is a schematic configuration diagram of an embodiment of the present invention, FIG. 6 is a sectional view taken along line C-C' in FIG. 5, and FIG. 7 is an electrical configuration diagram of an embodiment of the device shown in FIG. 5. It is.
It should be noted that the same components as in FIG. 1 are given the same numbers and their explanations will be omitted. In the figure, reference numeral 17 denotes an anode composed of a plurality of electrodes placed in the vertical magnetic field B formed inside the tubular member 1 by the magnets 4 and 5. As shown, a first anode 17a formed from one cylindrical anode;
Two anodes of the second anode 17b, which are also formed from five cylindrical anodes, are electrically insulated by an insulating member 18 and formed integrally. Reference numeral 19 denotes a selection switch for selectively connecting the first anode 17a and the second anode 17b, and when the terminal c of the selection switch 19 and the terminals a ₁ and a ₂ are connected (as indicated by the solid line in Fig. 7), In the illustrated connection state), the high voltage from the high voltage power supply 14 is applied only to the first anode 17a.
Also, when terminal c of selection switch 19 and terminals a ₂ and a ₃ are connected (connection state shown by broken lines in Figure 7)
A high voltage from the high voltage power supply 14 is applied to both the first anode 17a and the second anode 17b. 20
is the ammeter 1 that operates in conjunction with the selection switch 19.
This is a selection switch for selecting the shunt circuit 15' or the shunt circuit 15'' of No. 5, and the selection switch 1
9 selects the first anode 17a, the terminal c and the terminal _b1 are connected and the shunt circuit 15'' is selected.
Further, the selection switch 19 selects the first anode 17a and the second anode.
When both anodes of the anode 17b are selected, the terminal c and the terminal _b2 are connected and the shunt circuit 15' is selected.
The shunt circuit 15'' is detected by the ammeter 15, for example.
It is used when measuring pressures in the range of 10 ^-3 to 10 ^-5 Torr, and the branch circuit 15' is used when measuring pressures in the range of 10 ^-5 to ^{10 -7} Torr. Further, the scale of the ammeter 15 is engraved with scales that indicate the pressure when each shunt circuit is selected.

When measuring pressure with the Penning vacuum gauge constructed in this manner, first, the selection switch 19 connects the terminal c and the terminals a ₁ and a ₂ to apply a high voltage only to the first anode 17a. In this case, the selection switch 20 selects the shunt circuit 15'', and the ammeter 1
5, for example, the current shown by the broken line A in Figure 4 flows, and the current is converted to pressure on the scale plate from 10 ^-3 to
Expressed as pressure in the range up to 10 ^-5 Torr.
Next, the selection switch 19 selects terminal c and terminal a ₂ ,
a ₃ to connect the first anode 17a and the second anode 17b
Apply high voltage to. In this case, the shunt circuit 1
5' is selected by the selection switch 20 and the ammeter 1
For example, the current shown by the solid line B in Figure 4 flows through 510 ^-5
Expressed as pressure ranging up to ~10 ^-7 Torr.
Therefore, by selecting and using the anode formed in this way as described above, ^it is possible to ^reduce the
It is possible to measure a wide range of pressures, including the low pressure side of the system, using a relatively small capacity power source.

It should be noted that the present invention is not limited to the above embodiments and can be modified. For example, in this embodiment, the cylindrical anode 1
I prepared multiple sets of 7 in advance and switched them, but
The anode attached to the lid 11 of the vacuum gauge may be replaced depending on whether the purpose of measurement is on the low pressure side or the high pressure side.

As described above, the present invention provides an apparatus for measuring vacuum by applying a high voltage between a cathode and an anode provided in a vacuum and utilizing the discharge phenomenon that occurs between the cathode and anode. By selectively using multiple anodes, the capacity of the power supply can be reduced, and by increasing the discharge current in the high vacuum region, the discharge current can be reduced to 10 ^-3 Torr.
To provide an inexpensive Penning vacuum gauge that can measure pressures up to ~10 ^-7 Torr with a single ammeter.

[Brief explanation of the drawing]

1, 2, and 3 are diagrams for explaining a conventional device, FIG. 5 is a schematic diagram showing an embodiment of the present invention, and FIG. 6 is a C-C diagram of an embodiment of the present invention. 7 is a schematic view of the essential parts of the apparatus of the embodiment shown in FIG. 5, and FIG. 4 is a graph for comparing the performance of the conventional apparatus and the apparatus of the embodiment of the present invention. 1: cathode, 4, 5: magnet, 6, 9: O ring,
7, 10: Screw, 8: Connection pipe, 11: Lid, 1
2: Insulator, 13: Anode, 14: DC high voltage power supply,
15: Ammeter, 16: Vacuum chamber, 17: Cylindrical anode.

Claims (1)

[Scope of utility model registration request] In a device that applies the output of a constant voltage power source between an anode and a ground electrode arranged in a measurement space, measures the output current, and displays the measured output by converting it into pressure, the anode is replaced or A Penning vacuum gauge characterized by comprising means for displaying pressure in different conversions of the measured output current according to switching.