JPH09259814A - Secondary electron multiplier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary electron multiplier having good linearity across a wide output current range, including less dark current and noise and having a simple structure. SOLUTION: A cylindrical secondary electronic multiplier tube 2 made of semiconductive material having secondary electronic discharging capacity is supported by supporting members 6, 7 made of insulating material and capacitors 44, 45 and 46 are fixed to the supporting member 7. Lead wires 41, 42 and 43 formed by being drawn out from the output terminal part of the secondary electronic multiplier tube 2 are connected to the abovementioned capacitors 44, 45 and 46 inside of a vacuum container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary electron multiplying device, and more specifically, a secondary electron multiplying tube which is made of a semiconductor material having a secondary electron emitting ability and outputs a secondary electron multiplying tube. The present invention relates to a secondary electron multiplying device that detects electrons to detect ions and electrons in space.

[0002]

2. Description of the Related Art In recent years, in a device for detecting ions and electrons existing in outer space, a mass spectrometer for analyzing the mass of various ions and atoms, etc., a semiconductor material having a secondary electron emission ability is formed into a cylindrical shape. Using a secondary electron multiplier that
There is used a secondary electron multiplying device called a so-called channel electron multiplier (CEM) that can be directly attached to a device for detecting ions or electrons and used.

This type of secondary electron multiplier is for multiplying the secondary electrons generated in the secondary electron multiplier while applying an electric field to the secondary electron multiplier, so that the ions in the secondary electron multiplier are An incident end on which electrons and the like enter serves as a cathode, and an output end serves as an anode. In the secondary electron multiplier, there are two grounding methods, an anode grounding method and a cathode grounding method, depending on whether the anode of the secondary electron multiplier is grounded and used or the cathode is grounded and used. . FIG. 2 shows an example of a circuit configuration of a conventional secondary electron multiplying device of this type.

The above-mentioned secondary electron multiplying device is formed by cylindrically forming a semiconductor material having a secondary electron emitting ability, and has an input electrode 1 on the outer peripheral surface of a funnel-shaped portion 2a on which ions enter the input side. A secondary electron multiplier 2 is provided. This secondary electron multiplier 2
Gap of 0.5 mm to 1.0 mm from the output end of
Place the collector 3 made of a circular metal plate,
A high voltage E _H of −3 kV to −4 kV is applied to the input electrode 1 while accelerating −100 V to −200 V to the acceleration electrode 4 formed at the output end. The voltage E _L is applied, and the multiplication current is collected in the collector 3 by the acceleration voltage E _L.
The acceleration voltage E _L applied to the output end electrode 4 is obtained by the voltage drop due to the resistance R connected between the output end electrode 4 and the ground. The output secondary electron flow collected at the collector 3 is charged in the stray capacitance C _S generated between the collector 3 and the ground, and the charged electric charge is discharged through the load resistance R _L , at this time, the load resistance R _L. The voltage generated at both ends of is amplified by the preamplifier 5.

The secondary electron multiplier having the above circuit structure has a concrete structure as shown in FIG. That is,
Insulator plates 6 and 7 made of an insulator material having a good insulating property such as alumina are brought into contact with both end faces of the relay support rods 8, 9 and 10 and fixed by screws 11, 11 ,. A secondary electron multiplier tube 2 is supported between 6 and 7. The secondary electron multiplier 2 is supported near the neck and output end of the funnel-shaped portion 2a by support fittings 12 and 13 welded to the relay support rods 8 and 10, respectively. The input electrode 1 and the output electrode 4 of the secondary electron multiplier 2 are electrically connected to the relay support rods 8 and 10 through the support fittings 12 and 13, respectively. The collector 3 is welded to the relay support rod 9 so as to face the opening at the output end of the secondary electrode multiplier tube 2. On the other hand, the insulator plates 6 and 7
A terminal fitting 14 is fixed between each one end of each of the two by means of a screw 11 and a nut 15, and the insulating plates 6 and 7 are
An electrode plate 16 having an ion introduction hole 16a and a Faraday cup Fc is fixed between the other end portions of the same as the terminal fitting 14. As shown in FIG. 2, a voltage of E ′ _H is applied to the Faraday cup Fc with respect to the ground. Further, a positive voltage E _H is applied to the electrode plate 16 (see FIG. 2).

The terminal fitting 14 has terminals 17, 18 and 19, and the terminal 17 is connected to the electrode plate 16 by a lead wire 21 and the terminal 18 is connected to the relay support bar 8 by a lead wire 22. The terminal 19 is connected to the relay support bar 9 by the lead wire 23. Further, the conductive film 3 formed on the insulator plate 6 between the terminal fitting 14 and the relay support rod 10 to which the support fitting 13 is welded and electrically connected to the terminal fitting 14 and the relay support rod 10.
A film-shaped resistor 33 formed over 1, 32 is connected.

[0007]

By the way, it is generally desired that the secondary electron multiplier also has good linearity over a wide range of output current.
In the secondary electron multiplier, the following method has been conventionally used to improve the linearity over a wide range of output current.・ Lower the element resistance of the secondary electron multiplier.・ Increase the inner diameter of the secondary electron multiplier.

However, if the element resistance of the secondary electron multiplier is lowered, the power consumption increases, the high-voltage power source becomes large, and the element resistance of the secondary electron multiplier has a negative temperature characteristic. If so, thermal runaway may occur, so it is difficult to reduce the element resistance of the secondary electron multiplier. Further, if the diameter of the secondary electron multiplier is increased, the gain limitation due to space charge can be reduced,
There arises a problem that the multiplication effect becomes small. For this reason, it has been difficult for the conventional secondary electron multiplier described above to take out an output current of 10 microamperes or more in a state in which good linearity is maintained without being saturated.

On the other hand, in a multi-stage type secondary electron multiplier in which dynodes made of a material having a secondary electron emission capability are arranged in multiple stages from the input side to the output side, the final stage including the final stage dynode is included. Therefore, a capacitor is inserted between the dynodes of two to three stages and the charge stored in these capacitors is supplied to the output portion where the space charge due to the multiplication current becomes large, thereby improving the linearity. .

However, in this device, since the capacitor and the dividing resistance between the dynodes are installed outside the vacuum container accommodating the dynodes, a large number of terminals must be provided in the vacuum container, and the structure is It ’s complicated,
These terminals are the connection between the inside of the vacuum container and the atmosphere.Leakage current flows to the outside of the vacuum container through these terminals, and this leakage current causes dark current and noise in the secondary electron multiplier. There was a problem of becoming.

It is an object of the present invention to provide a secondary electron multiplying device which has a good linearity over a wide output current range, has little dark current and noise, and has a simple structure.

[0012]

In order to achieve the above object, the invention according to claim 1 of the present application provides a cylindrical secondary electron multiplier tube made of a semiconductor material having a secondary electron emitting ability, and A supporting member made of an insulative material for supporting the secondary electron multiplier, a plurality of capacitors fixed to the supporting member, and drawn out from the output end portion of the secondary electron multiplier to obtain the capacitor. It is characterized in that the connected lead wire is housed in a vacuum container.

[0013] The invention according to claim 2 is based on claim 1.
In the secondary electron multiplying device described in (1), the capacitor is a monolithic ceramic capacitor.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. One embodiment of the secondary electron multiplying device according to the present invention is shown in FIG.

The above secondary electron multiplying device is shown in FIGS.
In the secondary electron multiplying apparatus described in 1., three lead wires 41, 42 and 43 are wound at 5 mm intervals from the output end of the channel type secondary electron multiplier, and these lead wires 41, 42 and 43 are wound. The extraction end is connected to the three capacitors 44, 45 and 46 fixed to the insulator plate 7. These capacitors 44, 45 and 46
For example, with a withstand voltage of 100 V, the capacitance is 1
Microfarad monolithic ceramic capacitors (size 8 × 6.3 mm) are used. The capacitor can be used in a high vacuum of 10 ^-9 Torr and is fixed to the insulator plate 7 with an adhesive material, such as an epoxy resin, which can withstand baking at 120 degrees Celsius.

As a material forming the channel type secondary electron multiplier 2, for example, a zinc titanate-based ceramic semiconductor, a barium titanate-based semiconductor, or the like can be used, and the secondary electron multiplier is also used. The entire tube 2 may be made of semiconductive glass.

In FIG. 1, the parts corresponding to those in FIG. 3 are designated by the corresponding reference numerals, and the duplicated description will be omitted.

With such a configuration, capacitors 44, 45 and 46 are provided at the output end portions of the secondary electron multiplier 2 from which the lead wires 41, 42 and 43, which increase the space charge due to the multiplication current, are drawn out. The stored charge is supplied. As a result, the linearity of the secondary electron multiplier using the channel type secondary electron multiplier 2 is improved over a wide output current range. Further, since the capacitors 44, 45 and 46 and the lead wires 41, 42 and 43 are connected in the vacuum container, the number of terminals required to be provided in the vacuum container can be reduced. Therefore, dark current and noise caused by the terminals of the vacuum container can be significantly reduced.

The present invention can be applied not only to the secondary electron multiplier having the structure shown in FIG. 3 but also to the secondary electron multiplier having another structure. For example, the secondary electron multiplier 2 is not limited to an insulator plate, and a support substrate may be provided to support it.

The present invention can be applied not only to the anode-grounded secondary electron multiplier as in the above-described embodiment but also to the cathode-grounded secondary electron multiplier.

[0021]

As described above, the electric charge stored in the capacitor is supplied to the output end portion of the secondary electron multiplier tube from which the lead wire having the increased space charge due to the multiplication current is drawn out, and the linearity is improved. The capacitor and the lead wire are connected in a vacuum container. Therefore, according to the present invention, the charge stored in the capacitor is supplied to the output end portion of the secondary electron multiplier tube in which the space charge due to the multiplication current increases, through the lead wire drawn from the output end portion. So
The linearity of the secondary electron multiplier using a channel-type secondary electron multiplier is improved over a wide output current range, and the response to a large continuous input can be made faster. Since the capacitor and the lead wire are connected, the number of terminals that need to be provided in the vacuum container is reduced, and dark current and noise due to the terminals provided in the vacuum container can be significantly reduced, and the secondary electron The structure of the multiplier is also simplified.

Further, since the multilayer capacitor generally has high heat resistance and can obtain a relatively large electrostatic capacity in a small size, the electric charge is supplied to the output end portion of the secondary electron multiplier through the lead wire. By using a multilayer capacitor for the capacitor, the components of the secondary electron multiplier are downsized and can be easily housed in a vacuum container, and a small secondary electron multiplier can be obtained, which is heat resistant. A highly reliable secondary electron multiplier can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a secondary electron multiplying device according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional secondary electron multiplier.

FIG. 3 is a perspective view of a conventional secondary electron multiplying device.

[Explanation of symbols]

 2 Secondary electron multiplier 3 Collector 4 Accelerating electrode 6 Insulator plate 7 Insulator plate 14 Terminal fitting 16 Electrode plate 41 Lead wire 42 Lead wire 43 Lead wire 44 Capacitor 45 Capacitor 46 Capacitor

Claims (2)

[Claims] 1. A cylindrical secondary electron multiplier tube made of a semiconductor material having a secondary electron emission capability, a support member made of an insulating material for supporting the secondary electron multiplier tube, and this support member. A secondary container characterized in that a plurality of capacitors fixed to each other and a lead wire drawn from an output end portion of the secondary electron multiplier and connected to the capacitor are housed in a vacuum container. Electronic multiplier. 2. The secondary electron multiplying device according to claim 1, wherein the capacitor is a laminated ceramic capacitor.