JP4268280B2 - Accelerating tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an accelerating tube for accelerating charged particles such as electrons used in an electron microscope or the like, and is a connection terminal fixing insulating ring made of ceramics and the like, and a connection due to a difference in thermal expansion coefficient between the insulating ring and the connection terminal The present invention relates to an insulating ring for fixing a terminal and an element for preventing damage to the insulating ring.
[0002]
[Prior art]
A conventional accelerator tube K is shown in FIGS. 3 is a perspective view of the basic configuration of the acceleration tube K, and FIG. 4 is a cross-sectional view taken along line BB of FIG. In these drawings, 11 is made of a Ti-6Al-4V alloy or the like, and a plurality of ring electrodes stacked with an insulating ring 12 interposed therebetween, 12 is an insulating ring made of an electrically insulating material such as alumina ceramics, and 13 is A connection terminal made of a metal material such as iron (Fe) -nickel (Ni) -cobalt (Co) alloy, for applying an acceleration voltage of about 10 kV to about 50 kV to each ring electrode 11, 14 is made of alumina ceramics, etc. It is a connection terminal fixing insulating ring made of an electrically insulating material and provided at one end of the accelerating tube K main body and fixing one end of each connection terminal 13.
[0003]
As shown in FIG. 4, silver brazing or the like so that the central axes of the plurality of ring-shaped electrodes 11 and the insulating ring 12 substantially coincide with each other and the insulating ring 12 is sandwiched between the ring-shaped electrodes 11. These are joined via a metal brazing material to constitute an acceleration tube K main body. Then, when a predetermined acceleration voltage is applied to each ring electrode 11 to form an electric field due to a high potential difference between the ring electrodes 11 and an electron flow is passed through the acceleration tube K, the electron flow is generated by the plurality of ring electrodes 11. (See Japanese Patent Application Laid-Open No. 8-222162).
[0004]
As shown in FIG. 2, each connection terminal 13 has a metal brazing material such as a metallized layer such as Mo-Mn, a Ni plating layer, or silver brazing at one end thereof in the through hole 14a of the insulating ring 14 for fixing the connection terminal. The other end is joined to the hole of the ring-shaped electrode 11 via a metal brazing material such as silver brazing. In this case, the shape of the connection terminal 13 is linear. In the middle of the through hole 14a, a stepped portion having a large diameter portion and a small diameter portion is formed, and a flange is provided at the end of the connection terminal 13 on the connection terminal fixing insulating ring 14 side. It is locked to the stepped portion in 14a and is fixedly bonded with the metal brazing material or the like as described above. In general, one end of the connection terminal 13 and the connection terminal fixing insulating ring 14 are first bonded and fixed, and then the other end of the connection terminal 13 and the ring electrode 11 are bonded.
[0005]
Such an accelerating tube K is used for an electron gun or the like of an electron microscope, and accelerates thermoelectrons generated by heating a cathode such as a tungsten wire end by a ring-shaped electrode 11 forming a plurality of anodes. To do. This acceleration voltage is up to about 120 kV for a transmission electron microscope and up to about 50 kV for a scanning electron microscope. Further, in order to stably operate thermionic emission of the tungsten wire as the electron source, the inside of the acceleration tube K is set to a high vacuum of about 10 ⁻¹⁰ Torr.
[0006]
[Problems to be solved by the invention]
However, when the other end of the connection terminal 13 and the ring-shaped electrode 11 are joined and after joining, the connection terminal fixing insulating ring 14 and the insulation due to the difference in thermal expansion coefficient between the connection terminal 13 and the connection terminal fixing insulating ring 14. There was a problem that the ring 12 was damaged such as cracks and cracks. That is, since the thermal expansion coefficient of the connection terminal 13 is larger than that of the connection terminal fixing insulating ring 14 and the insulation ring 12, the connection terminal 13 is greatly expanded and contracted by heating and cooling at the time of joining. 14 and the insulating ring 12 were damaged. In particular, the insulating ring 12 was broken in half, and damage was caused such that one insulating ring 12 was divided into two rings. Since damage such as cracks and cracks are used by evacuating the inside of the accelerating tube K, the degree of vacuum is reduced or the vacuum is broken even if a fine crack occurs, and the accelerating tube K cannot be used. Was causing a serious problem.
[0007]
Further, as shown in FIG. 3, the conventional ring electrode 11 needs to be formed with a recess 11 a in order to avoid contact with the connection terminal 13 for another ring electrode 11. The number of processing steps has increased, leading to lower productivity and higher costs.
[0008]
Accordingly, the present invention has been completed in view of the above circumstances, and its purpose is to provide each ring-shaped electrode in an acceleration tube having a basic structure in which a plurality of ring-shaped electrodes and insulating rings are alternately stacked. Due to the difference in thermal expansion coefficient between the connection terminal for inputting the acceleration voltage and the connection terminal fixing insulating ring and the insulating ring provided at one end of the acceleration tube, the connection terminal fixing insulating ring and the insulating ring are damaged. There is to prevent. Another object is to simplify the shape of the ring-shaped electrode, improve the productivity of the acceleration tube, and enable manufacture at a low cost.
[0009]
[Means for Solving the Problems]
The acceleration tube of the present invention is an acceleration tube in which a plurality of insulating rings and ring-shaped electrodes having a larger diameter than the insulating ring are alternately stacked, and an acceleration voltage is applied to the ring-shaped electrodes to accelerate charged particles inside. A main body, a connecting terminal fixing insulating ring that is larger in diameter than the ring-shaped electrode and is installed at one end of the acceleration tube main body, and a ring-shaped electrode that is fixed to the connecting terminal fixing insulating ring , each being different A plurality of connection terminals for accelerating voltage input, and the ring-shaped electrode includes a hole having an opening on an outer peripheral surface, and the connection terminal extends from the connection terminal fixing insulating ring. A straight portion extending linearly along the length direction of the acceleration tube main body, a first curved portion bent in a direction away from the linear acceleration portion from the straight portion, and the ring than the first curved portion Provided on the electrode side, And a second curving portion bent on the side of the serial acceleration tube body, the end of the second curving portion is characterized in that it is inserted into the hole of the ring-shaped electrode.
[0010]
With the above configuration, the present invention absorbs the expansion and contraction of the connection terminal due to the difference in thermal expansion coefficient between the connection terminal, the connection terminal fixing insulating ring, and the insulation ring by elastic deformation of the bent portion formed on the connection terminal. By relieving the stress generated in the connection terminal fixing insulating ring and the insulating ring, damage such as cracks and cracks due to stress concentration of the connection terminal fixing insulating ring and the insulating ring is prevented, and the degree of vacuum inside the accelerator tube is reduced. A drop and a vacuum break can be eliminated. In addition, the shape of the ring-shaped electrode is simplified, and as a result, the productivity of the acceleration tube is improved and it can be manufactured at low cost.
[0011]
In the present invention, it is preferable that the bent portion of the connection terminal has an arc shape, the length of one bent portion is 3 to 15 mm, and the curvature radius is 1 to 5 mm. Thereby, the deformation due to the thermal expansion and contraction of the connection terminal is effectively absorbed by the elastic deformation of the bending portion, and the damage to the connection terminal fixing insulating ring and the insulation ring is effectively prevented.
[0012]
More preferably, α2−α1 ≦ 3 × 10 ⁻⁶ (/ ° C.), where α1 is the thermal expansion coefficient of the insulating ring for fixing the connection terminal and the insulating ring, and α2 is the thermal expansion coefficient of the connection terminal. With this configuration, deformation of the connection terminal is suppressed, and the connection terminal fixing insulating ring and the insulating ring are more unlikely to be damaged.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The acceleration tube of the present invention will be described below. An acceleration tube K1 of the present invention is shown in FIGS. FIG. 1 is a perspective view of the basic configuration of the acceleration tube K1, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. In these drawings, reference numeral 1 is a Ti-6Al-4V alloy, Fe-Ni-Co alloy, Ti, etc., and a plurality of ring-shaped electrodes stacked with an insulating ring 2 interposed therebetween, and 2 is an electrical material such as alumina ceramics. An insulating ring made of an insulating material, 3 is made of a metal material such as an Fe-Ni-Co alloy, and a connection terminal for applying an acceleration voltage of about 10 kV to about 50 kV to each ring electrode 1, 4 is made of alumina ceramics, etc. It is a connection terminal fixing insulating ring made of an electrically insulating material and provided at one end of the accelerating tube K1 main body and fixing one end of each connection terminal 3. The ring-shaped electrode 1 has a larger diameter than the insulating ring 2, and the connection terminal fixing insulating ring 4 has a larger diameter than the ring-shaped electrode 1.
[0014]
Then, as shown in FIG. 2, the central axes of the plurality of ring-shaped electrodes 1 and the insulating rings 2 are substantially aligned, and the insulating rings 2 are sandwiched between the ring-shaped electrodes 1. These are joined through a metal brazing material such as brazing to constitute the main body of the acceleration tube K1. The configuration such as the joint structure between the connection terminal fixing insulating ring 4 and the connection terminal 3 is the same as that shown in FIGS.
[0015]
The connection terminal 3 of the present invention forms one or more bent portions in the middle of the linear portion, except for the case where the end portion of the connection terminal 3 is bent to about 90 °. For example, when the end portion of the connection terminal 3 is joined to the side portion of the ring electrode 1 or the connection terminal fixing insulating ring 4, the joint portion may be bent from the middle straight portion to about 90 °. However, the bending of about 90 ° for such joining does not have a stress relaxation effect. Therefore, a bent part is formed in the linear part of the connection terminal 3 that is originally formed linearly.
[0016]
The bent portion of the present invention may be formed at a plurality of locations on the straight portion of one connection terminal 3. For example, as shown to Fig.5 (a), it can also be set as the structure which formed the bending part which consists of a semicircle or a part of circular arc in several places. In addition, a configuration in which one bent portion having one corner is formed as in (b), a configuration in which the bent portion in (b) is formed in a plurality of locations as in (c), and 2 as in (d). A configuration in which one bending portion having one corner is formed, a configuration in which the bending portion in (d) is formed in a plurality of locations as in (e), a configuration in which a coiled bending portion is formed as in (f), etc. Can be taken.
[0017]
These bent portions are preferably formed on the ring electrode 1 side of the connection terminal 3. That is, when the end of the connection terminal 3 on the connection terminal fixing insulating ring 4 side is joined and then the end of the connection terminal 3 on the ring electrode 1 side is joined, the end of the ring electrode 1 side is large. This is because thermal expansion and cooling contraction occur. More preferably, the bent portion is formed in the region of the half of the connection terminal 3 on the ring electrode 1 side, and optimally, it is formed on the end of the connection terminal 3 on the ring electrode 1 side.
[0018]
In the present invention, preferably, the length d of the bent portion of the arc-shaped connection terminal 3 as shown in FIGS. 1, 2, and 5A is 3 to 15 mm, and the radius of curvature is 1 to 5 mm. good. If the length d is less than 3 mm, the stress relaxation effect is insufficient. If the length d exceeds 15 mm, an improvement in the stress relaxation effect cannot be expected and the structure becomes too large and there is a risk of contact with other parts. is there. Further, if the radius of curvature is less than 1 mm, the stress relaxation effect is insufficient, and if the radius of curvature exceeds 5 mm, the improvement of the stress relaxation effect cannot be expected and the structure becomes too large and there is a risk of contact with other parts. .
[0019]
The connecting terminal fixing insulating ring 4 of the present invention is made of an insulating material such as alumina ceramics, and the connecting terminal 3 is made of Fe—Ni—Co alloy, Fe—Ni alloy, Ni, Ti, oxygen-free copper (OFHC copper: Oxygen Free High). Conductivity copper).
[0020]
If the thermal expansion coefficient of the connection terminal fixing insulating ring 4 and the insulating ring 2 is α1, and the thermal expansion coefficient of the connection terminal 3 is α2, α2−α1 ≦ 3 × 10 ⁻⁶ (/ ° C.) is preferable. . When α2−α1> 3 × 10 ⁻⁶ (/ ° C.), the stress relaxation effect due to the bent portion decreases. The material of the connecting terminal fixing insulating ring 4 and the insulating ring 2 and the connecting terminal 3 having such characteristics is, for example, that the connecting terminal fixing insulating ring 4 and the insulating ring 2 are made of alumina ceramics (α1 = 7.9 × 10 ^−6. In the case of (° C.), the connection terminal 3 is an Fe—Ni—Co alloy (α2 = 10.8 × 10 ⁻⁶ / ° C.).
[0021]
The acceleration tube K1 of the present invention is used for an electron gun or the like of an electron microscope, but can be applied as long as charged particles such as electrons are accelerated by an electric field.
[0022]
Thus, the present invention absorbs expansion and contraction of the connection terminal by elastic deformation of the bent portion formed in the connection terminal, and relaxes the stress generated in the connection terminal fixing insulating ring and the insulating ring, thereby fixing the connection terminal. It is possible to prevent breakage such as cracks and cracks due to stress concentration of the insulation ring and the insulation ring, and it is possible to eliminate a decrease in vacuum degree and breakage of the vacuum inside the acceleration tube. Further, the shape of the ring-shaped electrode is simplified, so that the productivity of the accelerating tube is improved and it can be manufactured at a low cost.
[0023]
In addition, this invention is not limited to said embodiment, A various change does not interfere in the range which does not deviate from the summary of this invention.
[0024]
【The invention's effect】
The present invention relates to a plurality of connection terminals in which one end is joined to a connection terminal fixing insulating ring and the other end is joined to any one ring-shaped electrode to linearly connect the connection terminal fixing insulating ring and the ring electrode. By having one or more bent parts in the straight line part in the middle, the expansion and contraction of the connection terminal due to the difference in thermal expansion coefficient between the connection terminal and the connection terminal fixing insulating ring By absorbing the elastic deformation and relieving the stress generated in the insulating ring for fixing the connection terminal, it is possible to prevent damage such as cracks and cracks due to the stress concentration of the insulating ring for fixing the connection terminal. Can be eliminated. Further, the shape of the ring electrode is simplified, the productivity of the acceleration tube is improved, and it can be manufactured at a low cost.
[Brief description of the drawings]
FIG. 1 is a perspective view of a basic configuration of an acceleration tube of the present invention.
FIG. 2 is a cross-sectional view of the acceleration tube taken along line AA in FIG.
FIG. 3 is a perspective view of a basic configuration of a conventional acceleration tube.
4 is a cross-sectional view of the acceleration tube taken along line BB in FIG.
FIGS. 5A to 5F show various shapes of connection terminals, and are schematic partial side views of the connection terminals. FIGS.
[Explanation of symbols]
1: Ring-shaped electrode 2: Insulation ring 3: Connection terminal 4: Insulation ring for fixing the connection terminal

Claims (3)

An accelerating tube main body in which a plurality of insulating rings and ring-shaped electrodes having a larger diameter than the insulating ring are alternately stacked, and the charged particles are accelerated by applying an accelerating voltage to the ring-shaped electrodes;
An insulating ring for fixing a connection terminal that is larger in diameter than the ring-shaped electrode and is installed at one end of the acceleration tube body;
A plurality of acceleration voltage input connection terminals fixed to the connection terminal fixing insulating ring , each connected to a different ring electrode ;
The ring-shaped electrode includes a hole having an opening on the outer peripheral surface,
The connection terminal includes a straight portion extending linearly along the length direction of the acceleration tube main body from the connection terminal fixing insulating ring, and a first portion bent from the straight portion in a direction away from the acceleration tube main body. A first curved portion, and a second curved portion that is provided on the ring-shaped electrode side of the first curved portion and is bent toward the accelerating tube main body. An acceleration tube inserted into the hole of the ring electrode.   2. The acceleration tube according to claim 1, wherein a bent portion of the connection terminal has an arc shape, a length of one bent portion is 3 to 15 mm, and a curvature radius is 1 to 5 mm. Α2−α1 ≦ 3 × 10 ⁻⁶ (/ ° C.) where α1 is a thermal expansion coefficient of the insulating ring for fixing the connection terminal and the insulating ring, and α2 is a thermal expansion coefficient of the connection terminal. The acceleration tube according to claim 1 or 2.

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