JP3114137U - Electron beam source equipment - Google Patents

Abstract

【Task】
In the conventional electron beam source device, the change in the amount of thermoelectrons due to uncertain deformation of the filament wire and the hindrance to taking out to an appropriate orbit are prevented, and the stability of the electron beam source device is improved. It also increases the useful life of the filament wire and improves the maintenance.
[Solution]
In the filament portion FA, the filament wire 4 is surrounded in the vicinity of the filament wire 4 by a hollow cylindrical ceramic tube 11 having an electron emission hole 13 in a part of the tube body 12, and the ceramic tube 11 is, for example, an adhesive for ceramics. Thus, the positive electrode 1 and / or the negative electrode 2 are fixed to the positive electrode 1 and / or the negative electrode 2 with the direction of the electron emission holes 13 being aligned with the appropriate direction of emitted electrons.
[Selection] Figure 1

Description

  The present invention relates to a device incorporating an electron beam source device having a filament wire for emitting thermal electrons, such as a gas chromatograph mass spectrometer.

  The filament portion for the electron beam source is used to heat the filament wire and emit thermoelectrons by passing a current through the filament wire built in the filament portion. As a material for the filament wire, for example, a tungsten wire or a rhenium wire is used, and the filament wire is heated by passing a current through a coiled, linear, or V-shaped bare wire, and thermoelectrons are emitted from the surface. As a conventional electron beam source device, a direct heating type method using the filament wire or a method of generating cold electrons without using the filament wire is adopted (for example, see Patent Documents 1 and 2). There is also an indirectly heated system using thermionic emission from a sleeve circumscribing the filament wire. The direct heat type electron beam source apparatus will be described below. Electrons generated in the electron beam source device are used for various purposes. For example, in a gas chromatograph mass spectrometer, electrons are accelerated at a voltage of several tens to several hundreds volts, and are guided to an ionization chamber to generate ions of an analyte. The ions are subjected to mass analysis in a mass analyzer in the gas chromatograph mass spectrometer and output as a mass spectrum.

  The basic structure and operation of the filament portion F of the conventional electron beam source device shown in FIG. 3 will be described below. Reference numeral 1 denotes a metal positive electrode, which is also held by an insulator 3 together with the metal negative electrode 2 and penetrates the insulator 3 and is connected to the filament wire 4. Reference numeral 4 denotes a filament wire for emitting thermoelectrons. The filament wire 4 is supplied from the plus electrode 1 and is heated by a current flowing through the filament wire 4 and the minus electrode 2 to emit thermoelectrons. The plus electrode 1 and the filament wire 4 and the minus electrode 2 and the filament wire 4 are fixed by means such as electric welding.

  The filament part F is usually used in a vacuum apparatus (not shown) that provides a vacuum atmosphere. The filament wire 4 basically emits electrons almost isotropically. However, the filament wire 4 is usually directed in a specific direction by applying an electric field or a magnetic field (not shown) around the filament portion F. Take out the electrons and use them. FIG. 3 shows an example of the electron extraction direction as the radiated electron direction. The filament part F is usually fixed by means (not shown) detachably attached to an external device (not shown) through an insulator 3, and lead wires for supplying current from the external device to the positive electrode 1 and the negative electrode 2. (Not shown) is connected.

JP 2001-167688 A Japanese Patent Laid-Open No. 05-242853

  The structure of the conventional electron beam source device is as described above, but in this structure, the filament wire undergoes indefinite deformation during long-term use of the filament wire, and the stability of the electron beam source device is impaired. Reduces maintainability. That is, the filament wire undergoes repeated thermal cycles of high-temperature heating during energization and normal temperature retention during non-energization, so that repeated stress is generated each time it is used. In addition, for example, in a gas chromatograph mass spectrometer, a magnetic field is applied in the vicinity of the filament wire in order to converge the thermoelectrons, so that the filament wire is repeatedly stressed each time it is used due to the interaction between the magnetic field and the current flowing through the filament wire. Has occurred. Since the filament diameter of the filament wire material is generally as thin as about 0.2 mm, its rigidity is small, and these stresses cause indefinite deformation of the filament wire as described above.

  This deformation changes the amount of thermionic electrons taken out, impairs the efficiency of extracting thermionic electrons to the proper orbit, and impairs the stability of the electron beam source device. For example, in the gas chromatograph mass spectrometer, ions of the analyte are produced by the electron impact of the thermoelectrons, but if the thermoelectrons are not taken out to the proper orbit, proper ionization is inhibited, and the mass of the gas chromatograph mass spectrometer is reduced. The spectral characteristics change and the reliability of the analysis is impaired. Further, because of the inhibition of the appropriate ionization, it is necessary to replace the filament wire in a much shorter period of time, that is, the life of the original filament wire, in other words, the life until the wire breaks. That is, the useful life of the filament wire is shortened and the maintainability is impaired. An object of the present invention is to provide means for solving such problems.

  In order to solve the above problems, the electron beam source device provided by the present invention surrounds the outer periphery of the filament wire other than the electron extraction region with a cylindrical insulator having a shape close to the filament wire and extending along the longitudinal direction of the filament wire. To do. As another means, an insulator having a shape close to the inner periphery of the filament wire and extending along the longitudinal direction of the filament wire is inserted into the inner space of the spiral filament wire.

  According to the present invention, the change in the shape of the filament wire is prevented by the insulator, which is much more rigid than the filament wire, so that indefinite deformation of the filament wire is prevented, and the heat to the proper position is prevented. Electron emission is maintained. For example, in a gas chromatograph mass spectrometer, as a result of maintaining proper ionization, a change in analytical characteristics of the gas chromatograph mass spectrometer is prevented. Further, as a result of improving the effective life of the filament wire, maintainability is improved.

  The electron beam source apparatus provided by the present invention has the following features. The first feature is that the outer periphery of the filament wire other than the electron extraction region is configured to be surrounded by a cylindrical insulator that is close to the filament wire and extends along the longitudinal direction of the filament wire. The second feature is that an insulator having a shape close to the inner periphery of the filament wire and extending along the longitudinal direction of the filament wire is inserted into the inner space of the spiral filament wire. Therefore, the basic configuration of the best mode includes means for surrounding the outer periphery of the filament wire other than the electron beam generation region of the filament wire with a cylindrical insulator having a shape close to the filament wire and along the longitudinal direction of the filament wire. An electron beam source device.

  This will be described with reference to the illustrated example. FIG. 1A is a configuration diagram of the filament portion FA of the first embodiment of the present invention. In FIG. 1A, the structure and operation of components having the same reference numerals as those in FIG. 3 are the same as those in FIG. The filament wire 4 is surrounded by a hollow cylindrical ceramic cylinder 11. FIG. 1B is a detailed view of the ceramic cylinder 11. The ceramic cylinder 11 is provided with an electron emission hole 13 in a part of the cylinder body 12, and the electron emission hole 13 is fixed so that the direction of the electron emission hole 13 coincides with the appropriate emission electron direction. . The ceramic cylinder 11 is fixed to both or one of the positive electrode 1 and the negative electrode 2 with a ceramic adhesive (not shown), for example.

  FIG. 2 is a configuration diagram of the filament part FB according to the second embodiment of the present invention. In FIG. 2, the structure and operation of components having the same reference numerals as those in FIG. The ceramic cylinder 14 is inserted in contact with the filament wire 4. The ceramic cylinder 14 is fixed to both or one of the positive electrode 1 and the negative electrode 2 with, for example, a ceramic adhesive (not shown).

  The present invention is not limited to the above-described embodiments, and various modifications can be given. For example, in Example 1 or 2 shown in FIG. 1 or FIG. 2, the cross-sectional shape of the ceramic cylinder 11 or 14 is a hollow cylinder or a cylinder, but the present invention can be applied even if the cross-sectional shape of the ceramic cylinder 11 is a polygon. Obviously, the present invention is not limited to the cross-sectional shape of the ceramic cylinder 11. The material of the ceramic cylinder 11 or 14 is not limited to ceramics as long as it is a heat-resistant insulator having rigidity that prevents deformation of the filament wire 4.

  In the embodiment of FIG. 1, the shape of the filament wire 4 is a coiled spiral shape, but the present invention can be applied even if the shape of the filament wire 4 is a linear shape. Further, the cross-sectional shape of the filament wire 4 may be, for example, a ribbon-like rectangle, and the present invention is not limited to the cross-sectional shape of the filament wire 4. Further, the present invention is not limited to the material of the filament wire 4. The present invention encompasses all of these.

  The present invention can be applied to a device such as a gas chromatograph mass spectrometer that incorporates an electron beam source device having a filament wire for emitting thermal electrons.

It is a block diagram of Example 1 of this invention. It is a block diagram of Example 2 of this invention. It is a block diagram of the conventional filament part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Insulator 4 Filament wire 11 Ceramic cylinder 12 Cylinder body 13 Electron emission hole 14 Ceramic cylinder F Filament part FA Filament part FB Filament part

Claims (2)

  In an electron beam source device equipped with a filament wire for generating thermoelectrons, the outer circumference of the filament wire other than the electron beam generation region of the filament wire is in the form of a cylindrical insulation close to the filament wire and along the longitudinal direction of the filament wire An electron beam source device characterized by being surrounded by an object.   In an electron beam source device having a filament wire for generating thermoelectrons, an insulator having a shape close to the inner periphery of the filament wire and along the longitudinal direction of the filament wire is disposed in the inner space of the spiral filament wire. An electron beam source device characterized by being inserted.

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