JPH10134753A - Transmission electron microscope and scintillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the insulation characteristic of optical fiber used for a scintillator to thereby enable detection of a good electron image by applying a conductive characteristic to clad glass or absorptive glass constituting the optical fiber. SOLUTION: An optical fiber comprises core glass 1 transmitting light, clad glass 12 covering the glass 1 and absorptive glass 13 absorbing the light leaked from the glass 11 and the light incident to the glass 12 and making small crosstalk. Material having an electric conductive characteristic is mixed in glass 12 and the glass 13 which are not required to transmit light and static destruction preventive measure is given thereto. Accordingly, it is possible to leak electrons entered the optical fiber without electrically charging the same, whereby a scintillator using the optical fiber resistant to the static destruction is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection apparatus for an apparatus such as an electron microscope and an accelerator for detecting and analyzing the intensity of an electron beam or an ion beam.

[0002]

2. Description of the Related Art In a transmission electron microscope, sample information contained in an electron beam is converted into a visible light image by a scintillator such as a fluorescent plate, and the image is visually observed by an operator directly or with a magnifier or the like. Some devices use a TV camera to observe the image of an electron microscope.
In particular, there is an apparatus in which a scintillator and a TV camera are connected by an optical fiber so that an optical image of the scintillator can be efficiently transmitted so that a brighter image can be observed when observing a high-magnification image.

[0003]

SUMMARY OF THE INVENTION In a scintillator using an optical fiber, when a current value per unit time of an electron beam applied to the scintillator becomes larger than a leakage current, electrons entering the inside of the optical fiber become specific. It may become charged in place and cause dielectric breakdown of the optical fiber.

An object of the present invention is to provide a scintillator in which the insulating properties of an optical fiber used for a scintillator are improved and a high quality electron microscope image or the like can be detected.

[0005]

The electron beam applied to the scintillator is converted by a fluorescent screen into an optical microscope image. Further, a part of the electron beam transmitted through the fluorescent plate enters into an optical fiber connected thereto. The electron beam travels in the fiber by a distance commensurate with the kinetic energy at the time of entry, and some electrons leak out of the fiber as a leakage current, while other electrons are charged at that position. When the charged electrons exceed a certain amount, that is, exceeding a dielectric breakdown voltage of the optical fiber, the charged electrons are destroyed and lose their function.

A means for solving this problem is that if the optical fiber itself is made of a conductive material, for example, lead glass, electrons are less likely to be charged in the optical fiber. However, when such a material is used, the light transmittance of the glass decreases, and it is impossible to transmit an electron microscope image, which is the original purpose, with high efficiency. In order to improve the optical fiber in consideration of such a situation, it is necessary to minimize the charge amount of the entered electrons. To do so, so as not to lose the light transmission efficiency
The best means is to make the clad glass, the absorber glass, and the like constituting the optical fiber conductive.

[0007] By employing this conductive absorber glass for the optical fiber, the ratio of at least the electrons that have entered the optical fiber to the cladding glass or the absorber glass increases to the area ratio or more, which means that Will be reduced. By reducing the volume resistivity, the amount of electrons charged on the core glass can be reduced, and the insulation performance of the optical fiber can be improved.

[0008]

FIG. 2 shows a configuration of a general transmission electron microscope. Electron beam 2 from electron gun / acceleration tube 21
2 sets a desired current value and a spot size with a condenser lens 23 and irradiates the sample 24. The electron beam 22 transmitted through the sample 24 and containing the sample information is
At 5, the image is focused on the fluorescent plate 28, enlarged by the intermediate lens 26 and the projection lens 27, and an electron microscope image 29 of the sample 24 is formed on the fluorescent plate 28.

The transmission electron microscope has a camera room 31 for taking a film of an electron microscope image 29 below the fluorescent plate 28,
There is a scintillator 32 and the like arranged for photographing the electron microscope image 29 with a TV camera. The photographing of the electron microscope image 29 and the observation with the TV camera are executed by opening and closing the fluorescent plate 28.

In photographing the electron microscope image 29 with a TV camera, the fluorescent material 33 at the top of the scintillator 32 converts the image into a visible electron microscope image, and forms an image on a TV camera 35 with an optical fiber 34.
The image on the CRT monitor 36 can be observed.

FIG. 3 shows an example of the structure of the scintillator 32. A thin aluminum film 37 is deposited on the phosphor 33 which is a main part of the scintillator 32, and serves to protect the phosphor 33. In addition, a conductive film 38 such as a Nesa film is deposited on the entire surface of the optical fiber 34, and is connected to a ground wire 39 for the purpose of eliminating charges and the like in the optical fiber 34. This is because the optical fiber 34 is entirely an insulator, and the charged electric charge is not discharged to the ground through the ground wire 39.
This is because the entire optical fiber may be charged up.

Further, the optical fiber 34 is a TV camera 35
(Not shown), and uses the electron microscope image obtained by the phosphor 33 as a means for efficiently transmitting light loss with a minimum.

FIG. 4 shows that the electron beam 22 is applied to the scintillator 32.
FIG. 4 is a diagram in which the behavior and the trajectory of the optical signal 42 and the transmitted electrons 41 inside the scintillator 32 are estimated when the light is irradiated. (Here, the aluminum film 37 shown in FIG. 3 is omitted because it is not necessary to explain). When the individual electrons of the electron beam 22 irradiate the phosphor 33, some of the electrons cause the particles of the phosphor 33 to emit light, resulting in an optical signal 42 which is an individual element of the electron microscope image. And is incident on the TV camera 35.

The remaining transmitted electrons 41 pass through the phosphor 33 and enter the optical fiber 34 as incident electrons 43.
Since the electron beam 22 is accelerated by a voltage with high stability, the incident electrons 43 stop at a certain distance (range) in the optical fiber 34 and are charged at that position. However, the charged electrons 44 flow as leak current from the inside of the optical fiber 34 as leak electrons 45 from the conductive film 38 to the ground line 39, and return to the electron gun / acceleration tube 21 via the ground.

At this time, the relationship between the amount of incident electrons 22 per unit time and the amount of leak electrons 45 per unit time is such that when the latter is larger than the former, the potential of the charged electrons 44 remains at a low value. When the latter is equal to the former, there is no change in the potential, and when the latter is smaller than the former, it can be easily imagined that the potential of the charged electrons 44 gradually increases with time.

As a result, when the incident electrons 43 are more than the leak electrons 45 from the inside of the optical fiber 34, the potential of the charged electrons 44 rises with time, and the dielectric breakdown voltage of the optical fiber 34 at that position increases. If it exceeds, it is considered that the charged electrons 44 are discharged at a stretch and the optical fiber is broken. Therefore, it can be said that an optical fiber having as many leak electrons 45 as possible, that is, a component having a low volume resistivity of the optical fiber has a higher resistance to dielectric breakdown.

FIG. 1 shows the structure of a general optical fiber. The optical fiber includes a core glass 11 for transmitting light, a cladding glass 12 for covering the light, and an absorber glass for absorbing light leaked from the core glass 11 and light incident on the cladding glass 12 to reduce crosstalk. 13
It is composed of Since the core glass 11 has a function of transmitting optical information, it is difficult to configure the core glass 11 from a material having conductivity without reducing transmittance. However, the clad glass 12 and the absorber glass 13 are portions that do not need to transmit light. Therefore, by mixing and using a material having an electric conduction property in this portion, electrons that have entered the optical fiber 34 can leak out of the optical fiber without being charged.

That is, as a result, a scintillator using an optical fiber resistant to electrostatic breakdown is obtained, and a transmission electron microscope using the scintillator is obtained.

[0019]

According to the present invention, a highly reliable scintillator used for an electron microscope or the like can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a structural example of an optical fiber according to the present invention.

FIG. 2 is an explanatory diagram of a configuration principle of an optical system and an observation system of a general transmission electron microscope.

FIG. 3 is a cross-sectional view of a scintillator.

FIG. 4 is an explanatory diagram of a behavior and a trajectory of electrons in a phosphor and an optical fiber.

[Explanation of symbols]

11: core glass, 12: clad glass, 13: absorber glass.

Claims (2)

[Claims] 1. A transmission electron microscope comprising an electron gun / acceleration tube, a condenser lens, a sample holder, an objective lens, an intermediate lens, an electron optical system including a projection lens, and a camera room for film shooting. TV image
A transmission electron microscope characterized in that a scintillator containing a phosphor is made of an optical fiber that has been protected from electrostatic damage by an electron beam for photographing with a camera. 2. An optical fiber comprising a core glass for transmitting light, a cladding glass of a coating material thereof, and an absorber glass for absorbing crosstalk light leaked from the cladding glass. A scintillator in which the absorber glass or both are mixed with a metal material or the like to have a property of having conductivity, and an optical fiber having a relatively large leak current is used to improve the dielectric strength.