JPH09177975A - Vacuum container - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a novel vacuum container having a bake-out mechanism that enables sufficient degassing. An exhaust device attached to a mirror body 1 is operated to start exhausting the inside of the mirror body. At this time, the DC current power supply 4 and the DC voltage power supply 7 are also operated. Then, the current from the direct current power source 4 flows to the filament 3, so that the filament is heated and turned incandescent. Radiant heat due to incandescence of the filament heats the inner wall of the mirror, so that the inner wall of the lens is degassed. On the other hand, since a positive voltage is applied between the filament 3 and the mirror body at the ground potential from the DC voltage power source 7, thermoelectrons are emitted from the filament 3. Since the thermoelectrons impact the inner wall of the mirror body, the inner wall of the mirror body is heated and the inner wall of the mirror body is degassed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vacuum container having a bake-out mechanism.

[0002]

2. Description of the Related Art When a vacuum container is evacuated, the inside of the vacuum container is exhausted by an exhaust device (exhaust pump) provided in the vacuum container. At that time, in order to realize a higher vacuum, the vacuum container is burned out and degassed. A higher vacuum is realized when the degassing by the bakeout is sufficiently performed, and the degassing is efficiently performed as the bakeout temperature is higher.

[0003]

As a vacuum container, for example, when a mirror body of an electron microscope is considered, the mirror body itself is a part that realizes a plurality of magnetic field lenses, or the mirror body itself has various types. Since the electromagnetic coil is incorporated, the wall of the mirror body is extremely thick and its shape is complicated. Further, the mirror body itself is not integrated, but the plurality of lenses and the like are assembled in multiple stages. For this reason, in the electron microscope (particularly, the ultra-high vacuum electron microscope), a heater is provided inside the yoke or the flange of the lens to heat the entire mirror body. Therefore, it takes time to raise the temperature for performing bakeout and cool down for stopping bakeout, requires a large amount of electric power, and causes distortion between the multi-stage assembled lens body constituent parts. However, there is a problem that leaking is likely to occur, and the temperature cannot be raised so high to avoid thermal influence on the electromagnetic coil, etc., so that efficient degassing cannot be performed.

Recently, a mechanism has been adopted in which a halogen lamp is incorporated in the mirror body, the filament of the halogen lamp is heated, and the inner wall surface of the mirror body is heated by radiant heat, but the radiant heat is limited by the filament temperature (that is, However, if the filament temperature is too high, the filament will be broken), and the baking temperature cannot be so high, and degassing cannot be performed sufficiently efficiently.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel vacuum container provided with a baking-out mechanism that enables sufficient degassing.

[0006]

A vacuum container according to the invention of claim 1 is a vacuum container provided with an exhaust device, in which a filament is arranged so as to be electrically insulated from the container. It is characterized in that a current source is connected in series to the filament to form a closed circuit including the filament and the current source, and a DC voltage source is connected between the closed circuit and the container.

[0007]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows, as an example of the present invention, a cross section of, for example, a cylindrical vacuum container (eg, a mirror body of an electron microscope).

In the figure, reference numeral 1 denotes a mirror body, which is made of metal such as stainless steel and is grounded. Inside the mirror,
Insulator supports 2A, 2B fixed to the inner wall of the mirror,
A filament 3 is provided which is supported by 2C, 2D and 2E and is spirally wound from the upper part to the lower part inside the mirror body. Reference numeral 4 denotes a direct current power source connected in series to the filament 3 via a lead wire 5 outside the lens barrel. The filament 3 and the lead wire 5 are connected by a current introducing terminal 6 which can maintain the hermeticity of the mirror body 1 and is insulated from the mirror body and attached to the mirror body. Reference numeral 7 is a DC voltage power supply for applying a positive voltage between the closed circuit formed by connecting the filament 3 and the DC current power supply 4 in series and the ground.

The operation of such a configuration will be described below.

First, an exhaust device (not shown) attached to the mirror body 1 is operated to start exhausting the inside of the mirror body. At this time, the DC current power supply 4 and the DC voltage power supply 7 are also operated. Then, the current from the direct current power source 4 flows to the filament 3, so that the filament is heated and turned incandescent. Radiant heat due to incandescence of the filament heats the inner wall of the mirror, so that the inner wall of the lens is degassed. On the other hand, since a positive voltage is applied from the DC voltage power supply 7 between the filament 3 and the mirror body at the ground potential, the thermoelectrons emitted from the filament 3 are transferred to the mirror body 1 at the positive potential. Since it flies in the direction and impacts the inner wall of the mirror, the inner wall of the mirror is heated, and the inner wall of the mirror is degassed. This degassing is due to degassing due to temperature and desorption due to electronic excitation. In this way, since the inner wall of the mirror body is heated by radiant heat from the high-temperature filament and thermionic impact, the surface of the inner wall of the mirror body becomes the highest temperature, and degassing from the surface of the lens body and its vicinity without heating the entire lens body. Can be done very efficiently.

The power supply for supplying a current for heating the filament may be an AC power supply. Also, since the total amount of energy due to the latter thermionic impact is determined by the product of the amount of radiated current of thermions and the voltage applied between the filament and the mirror,
Even if the amount of current flowing through the filament 3 is suppressed, it can be covered by increasing the voltage value, so that there is no fear of filament breakage due to excessive temperature rise.

Further, according to the present invention, since the inner wall of the mirror body is heated, it is possible to easily provide the heat shield plate only to the part having a problem when the temperature rises too much.

[Brief description of the drawings]

FIG. 1 schematically shows a vacuum container as an embodiment of the present invention.

[Explanation of symbols]

 1 Mirror 2A, 2B, 2C, 2D, 2E Support 3 Filament 4 First DC power supply 5 Lead wire 6 Current introduction terminal 7 Second DC power supply

Claims (1)

[Claims] 1. A vacuum container provided with an exhaust device, wherein a filament is arranged in the container electrically insulated from the container, and a current source is connected in series to the filament to connect the filament and the current source. A vacuum container comprising a closed circuit including a DC voltage source connected between the closed circuit and the container.