DE1923075U - ELECTRON BUNDLE DEVICE WITH A LON GENERATOR AND ION GENERATOR FOR SUCH DEVICES. - Google Patents

Description

RA.382 582 * 7/22/65

Dr. Herbert Scholz _{§ the 2} , _{# Jul} . , _g65

Patent attorney MBnckeberestrofle 7 _a / _,

Telephone: 321017 & 2 / .DU

Telegraph: 2-15288 a hmb

P 21 835 / 21g Gbm My files; PH-18.302

Philips Electronics and Pharmaceutical Industries Corporation, 100 East 42nd Street, Few York, N.I./USA

"Electron beam device with an ion generator and Ion generator for such devices "

The purpose of the innovation is to convert electrical charges into electrical bundling devices, e.g. B. electron microscopes, electron diffraction devices and the like. To render harmless. at Electron microscopes that are operated with relatively low acceleration voltages are the result Electric charges on the surface of a photographic film placed in such a microscope is to record an image of the object to be examined,

The photographic film used is a poor conductor of electricity. As a result, the electrons are in the imaging beam from where they hit the film strike, not carried away. laughed a short time ago accumulated sufficient electrical charge to cause a significant change in the electrostatic field, especially near the film surface. Consequently with continuous irradiation, electrons are deflected in increasing numbers towards different areas, away from the places where they should hit the film, thereby distorting the picture. Before the film is sufficiently exposed to make a record on the emulsion of the

In order to create a film, the harmful charge application is sufficient to cause a deflection of the electron trajectories that is detrimental to the image quality. -: " ^:

The same accumulation of a negative charge occurs at 8xm in their electron bundle devices, 2. B, electron diffraction devices in which the object to be examined is either non-conductive or is supported by an insulator. As with electron microscopes, distortion of the electron beam as a result of an accumulation of electrical charge should be avoided as far as possible. : ■ --...

It is known that a thin conductive layer is sufficient -, -. to divert such charges. Preferably bring one conductive layer not on the surface of the photographic The film or the electron diffraction object is absorbed some of the electrons required for image formation and may be the cause of that in the electron diffraction device a diffraction image of the visual material is created. Therefore the charge must be removed in some other way will. According to the innovation, a lohen generator is provided, which generates positive ions and the positively charged ions on the surface of the object or photographic film be directed and flood the surface. However, care must be taken that not at the same time with Ions also produce light. A suitable for this purpose * The ion source consists of a filament which, with a binder and an alkali salt, is relatively less Volatility is coated, which emit positive ions, can, if only it is heated to a dark red glow. the The ion source is preferably in the vicinity of the path of the electron beam arranged and close to the surface of the

-3 -

Electron diffraction object or the photographic film in the electron microscope.

The innovation is described below with reference to the 'enclosed Drawing explained in more detail in the

Pig. 1 shows a simplified cross section through an electron microscope is where the hiring applies while

Fig. 2 shows a simple image on a photographic film in the device of Fig. 1 shows.

The electron microscope 11 of FIG. 1 has a housing or a sheath 12 enclosing a filament or cathode 13 which is the source of a beam 14 of electrons. A capacitor 16 sets up das.Elektronenbündel on a Object to be examined 17 · This object influences the electron beams passing through, which continue to be transmitted by a Objective 18 and a projection lens 19 in an enlarged Image of the object 17 can be focused on the emulsion coating on the surface of a photographic film 21.

The film is in a cassette 22 from outside of the microscope by means of a button 23 and a shaft 24 is operated, which is provided with a vacuum-tight bushing through the shell 12. Using the button 23 and the Shaft 24, the film cassette 22 can be rotated to the side, so that the electron beam 14 can be seen on a viewing window 26 fall at the end of the microscope. This insight window carries a fluorescent screen 27 on its inner surface

Both the photographic film 21 and the phosphor screen 27 are isolators. Because of the insulating nature of: Film 21 and of the screen 27 electrons of the bundle 14 have the slope on the surface of the film or on the luminous

~ 4

to accumulate umbrella.

FIG. 2 shows a single image of the elm 21 with a simple rectangular image 28, line such image is only generated on the film 21 when a sufficient number of electrons have arrived on the film to bring about the necessary changes in the sensitive emulsion. Therefore it often happens that long before a sufficient number of electrons has arrived to produce a good image 28 on film 21, the electrical charge built up by the first arriving electrons creates a distorting field. Electrons arriving later must migrate through this distorting field ⁷ and as a result, instead of the correct rectangular pattern 28, the pattern recorded on the film 21 or perceptible on the luminescent screen 27, which is formed by a sufficiently long exposure to the electron beam, becomes the pattern of the accumulated electrical charge deflected, so that a distorted rectangle 28a is formed.

To neutralize the accumulated electrical charge, If the microscope 11 contains an ion generator 29 lh shape a filament in the area around the electron beam and between the electron lens 19 and the photographic Film 21 is arranged. This ion generator consists of one Electrically conductive filament, usually made of platinum, which is coated with a substance that, when the Filament emits positive ions because any radiation from the filament onto film 21 or the Fluorescent screen 27 would fall, it is desirable that this Radiation is kept to a minimum in order to avoid » that a haze is caused on the film or the contrast of the image on the luminescent screen is reduced » This means that the temperature of the filament 29 as possible must be kept low. The filament cover must be

■ »5 - ■

thus ions at a relatively low temperature generate, and experiments have shown that alkali metal salts have the best properties for ion generation at low [temperature, and further that of the alkali metal salts Potassium salts are particularly suitable.

Although electron microscopes, including the above type, are usually disassemblable so that it is relatively easy to open them and change the filament 29, it is desirable to use an ion emissive material that is not excessively volatile and / when heated does not disappear from the filament 29 too quickly. Potash hydrogen phosphates and potassium diphosphates provide ion generators with the longest lifespan and the highest ion emission. To prevent these salts from peeling off, an alkali metal silver silicate binder, e.g. B. ^{Potash Waterglass:} Find use to attach the salts to the filament 29, after which the ion generator can be used for several weeks before it needs to be replaced. - - -

The inventive ion generator is not only useful for canceling the negative charge that can be built up on: a photographic film or the fluorescent screen of an electron microscope, but it can also be useful in other electron beam devices in which the electron beam is aimed at some isolated part which is either an insulator itself or is conductive but is supported by insulators. For example, the object or sample to be examined with the aid of an electron diffraction instrument may be exposed to the same accumulation of electrical charge as the photographic ulm 21 or the fluorescent screen 27 of an electron microscope. Because with an electron diffraction instrument an electron image must be generated on the basis of the points at which electrons of the beam hit the sample

Any accumulation of an electrical charge that causes the electrons to hit other places, if possible can be avoided, and the post-inflation ion generating coated filament 29 makes it possible.

It goes without saying that the hiring is not based on what has been described Embodiment limited.

Eye protection requirements:

Claims (8)

RÄ.382 582 * 7/22/65 "7 claims for protection see chap 1. Electron bundle device containing an electron source, an electron lens system and an isolated part, who is in the path of this bundle and through the electrons of the beam is hit, characterized in that an ion generator within the device mentioned which generates positive ions and directs this on the surface of the mentioned isolated part, so that one by the electrons on this Part of the built-up negative electron charge is canceled, 2. Apparatus according to claim 1, in particular an electron microscope for recording images on a photographic IiIm through direct exposure through the electron beam, characterized in that the ion generator is located outside the orbit of the electron beam and is positive Ions are generated and these on the same surface of the film on which the electrons of the bundle impinge. 3. Electron microscope according to claim 2, characterized in that the ion generator in the area between the lens system and the film and located outside the orbit of the electron beam, and the whole emulsion of the elm with positive Ions flooded to break the negative charge built up on the film by the electrons in the bundle. 4. Apparatus according to claim 1, characterized in that the ion generator is a conductive filament coated with an alkali salt capable of emitting ions. 5. Apparatus according to claim 4, characterized in that the mentioned salt is a potassium salt » 6. Gate direction according to claim 5, characterized in that the mentioned salt is potassium hydrogen phosphate * 7. Apparatus according to claim. 5, characterized in that the mentioned salt is potassium diphosphate. 8. Apparatus according to claim 5, characterized in that an alkali metal silicate binder is provided which binds the mentioned potassium salt to the mentioned filament « 9 »Device according to claim 8, characterized in that the binder is potassium silicate and that the filament is made of platinum.