US3873831A

US3873831A - Particle-beam device equipped with a foundation supported to permit swinging movement

Info

Publication number: US3873831A
Application number: US384754A
Authority: US
Inventors: Ernst Ruska; Franz Stocklein
Original assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Current assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Priority date: 1971-02-05
Filing date: 1973-08-01
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25

Abstract

A particle-beam device such as an electron microscope or the like has a column containing a beam generator and optical components and a foundation for carrying said column. The foundation is supported to permit swinging movement at a low characteristic frequency. A control center configured as a desk console is arranged on a platform separate from the foundation and having space sufficient for accommodating an operator of the particle-beam device. A flexible transmitting structure for connecting the control center with said column is also provided.

Description

United States Patent [191 Ruska et al.

[ Mar. 25, 1975 3,361,398 1/1968 Brinkman ct a1. 248/18 OTHER PUBLICATIONS The Electron Microscope by E. F. Burton ct al. published by Reinhold Publishing Corp., New York, 1946, page 225.

Primary Examiner-James W. Lawrence Assistant E.taminerC. E. Church Attorney, Agent, or FirmHerbert L. Lerner [57] ABSTRACT A particle-beam device such as an electron microscope or the like has a column containing a beam generator and optical components and a foundation for carrying said column. The foundation is supported to permit swinging movement at a low characteristic frequency. A control center configured as a desk console is arranged on a platform separate from the foundation and having space sufficient for accommodating an operator of the particlebeam device. A flexible transmitting structure for connecting the control center with said column is also provided.

10 Claims, 5 Drawing Figures 1 PARTICLE-BEAM DEVICE EQUIPPED WITH A FOUNDATION SUPPORTED TO PERMIT SWINGING MOVEMENT [75] Inventors: Ernst Ruska; Franz Stocklein, both of Berlin, Germany [73] Assignee: Max-Planck-Gesellschat't Zur Forderung Der Wissenschaften e.V., Gottingen, Germany [22] Filed: Aug. 1, 1973 [21] Appl. No.1 384,754

Related U.S. Application Data [63] Continuation of Ser. No. 162,767, July 15, 1971,

abandoned,

[30] Foreign Application Priority Data Feb. 5, 1971 Germany 2106378 [52] U.S. Cl. 250/306, 250/311 [51 Int. Cl. H0lj 37/26 [58] Field of Search 52/167, 749. 750; 73/430;

[56] References Cited UNITED STATES PATENTS 2,268,495 12/1941 Petty 248/18 PATENTEB MR 251975 sum 1 or Hg. 1 I

PMENTEBHARZSISYS SHEET 2 OF 4 PATENIH] W 2 5 I975 SHEET u gr 4 Fllg. 4

PARTICLE-BEAM DEVICE EQUIPPED WITH A FOUNDATION SUPPORTED TO PERMIT SWINGING MOVEMENT This is a continuation of application Ser. No. 162,767, filed July 15, 1971, now abandoned.

Our invention relates to a particle beam device such as an electron microscope or the like equipped with a column containing the beam generator and the optical components. The particle beam device also has a desklike control console and a base which can swing at a low characteristic frequency.

In the development of the electron microscope it was early recognized that the resolutions obtainable with electron optics are substantially affected by earth vibrations caused mostly by traffic and industry. This is especially the case for making photographic pictures of electron images where long illumination times are required. With the advance of imaging technology, which in the meantime has led to a resolution capability of only a few angstroms, the problem has taken on significance. Especially bending movements of the microscope column are damaging, which occur because of horizontal swings of the earth or floor on which the microscope is placed. The suppression of such swinging movements is especially difficult with microscopes having a high beam voltage of more than 100 kV and the correspondingly greater column lengths of several meters.

For the foregoing reasons, a 500 kV electron microscope including the control console has already been placed on a heavy foundation. The foundation, on the one hand, is isolated against the floor by means of rubber dampers. In this connection, reference may be hat to the Journal of Scientific lnstruments 1967, Vol. 44, starting at page 747, especially page 749. The foundation has a characteristic frequency of approximately 3 Hz. In this way, it is possible to reduce the frequency of floor swings which amounts to approximately 13-15 Hz to a swinging movement having a frequency of 3 Hz.

It is an object of our invention to improve the isolation for particle beam apparatus of the above mentioned type against vibration that originates in the region surrounding the apparatus.

It is another object of our invention to provide an arrangement for reducing the characteristic frequency with which the foundation upon which the microscope column is mounted swings in response to vibrations emanating from environment of the microscope.

According to a feature of the invention, we provide an arrangement wherein only the column is carried on a foundation, whereas the control console is located on a platform separated from the foundation. The platform includes space sufficient for accommodating an observer. The console is connected to the column only by flexible transmission means. In the arrangement of the invention, the observer or operator himself is prevented either from his own movements or by actuating the control console to transfer vibrations to the column. The observer can move about freely on the platform during the time a photographic picture is made without having to fear that his movements might affect the sharpness of the picture.

The characteristic frequency of the foundation and column considered as a unit has a characteristic frequency of preferably at most 1 Hz, so that the accelerations imparted to the parts of the column during swinging movements are only very small. Making the characteristic frequency this low has, in addition, the advantage that it is widely separated from the characteristic frequency of a bending movement of the column, which can amount to approximately Hz, so that the foundation swinging movement can cause a bending movement of the column only with considerable damping.

In a preferred embodiment of the invention, the foundation is pendulum-like supported. The pendulum length can, for example, amount to 10 meters, so that the frequency of swinging movement amounts to approximately l/6 Hz. Vertical swings can be retarded by means of low frequency air springs, for example, less than 3 Hz.

The suspension of the unit consisting of the foundation and microscope column in a manner similar to that of a gravity pendulum has in the situation at hand an especially valuable characteristic. A bending swinging movement of the column can only be initiated when portions of the column which lie at different elevations experience various horizontal accelerations. However, if the total height of the microscope column over the foundation is small-relative to the pendulum length, the aforementioned accelerations are all the same in the final approximation, so that the parts of the column relative to each other are subjected to only very small horizontal forces. If the foundation is suspended by several parallel lines, so that the microscope column with a pendulum swing undergoes a movement parallel to itself, these residual forces also are completely eliminated.

The quiet of the foundation can be further improved by surrounding the particle beam apparatus by a double walled building whose walls are separated from each other at the ceiling and on the sides by means of an intermediate air space. In this construction, the platform is joined only to the outer wall and the foundation is suspended from the ceiling of the inner wall. The suspension of the foundation is in this way isolated from wind forces and floor pressures. The walls of the building are preferably anchored at least 10 meters deep in the earth, so that the amplitudes of vibrations generated on the earths suface are substantially reduced as they travel to the base of the inner wall.

According to another embodiment of the invention, the foundation can also rest on one or more bending elastic columns which likewise should be anchored at great depth under the earths surface, preferably at least 10 meters.

The stability of the microscope column can be further increased by means of a strengthening support for increasing rigidity mounted on the foundation. Such a support is rigid and has a somewhat pyramidal or conical configuration. The rigid support is tightly connected to the column at its lower end and embraces the column at its top end in the region of the upper half of the column. lt is advantageous to dimension the portion of the rigid support gripping the upper half of the column as a horizontally adjustable collar, which makes it possible to apply a bending prestress to one side of the column. In this way, the fact can be taken into account that the microscope column does not need to have the same bending elasticity in all directions because of construction reasons. If a bending pre-stress is imparted to the column in a direction in which the bending moment is a minimum, a deflection first occurs when the force produced by an outside vibration exceeds the prestressed force. The initiation of a bending swinging movement in this direction is then made more difficult.

Also, floor vibrations do not, as a rule, occur in the same magnitude in all directions. These vibrations more often can be especially intense in a definite direction according to the spacial relationships. Also, in this instance, it is advantageous to impart a bending prestress to the column in the direction of maximum vibration.

The invention will now be described with reference to the drawings, wherein:

FIG. 1 illustrates, in section, an elevation view of a double-walled tower-like building in which an electron microscope is arranged as required by the invention;

FIG. 2 illustrates an alternate embodiment of FIG. 1 in which the microscope column is supported on a foundation secured in the earth via long, slender columns",

FIG. 3 is a perspective view of an electron microscope illustrating the disposition or supporting members including a strengthening support for the microscope column;

FIG. 4 illustrates the upper portion ofa strengthening support for increasing the rigidity of the microscope column; and

FIG. 5 illustrates a plan view of the portion of the strengthening support shown in FIG. 4.

FIG. 1 illustrates, in section, a double-walled towerlike building in which the electron microscope is housed. The electron microscope in its totality is designated by reference numberal 1 and comprises essentially a column la and a desk-like control console 1b. These parts are not rigidly connected together mechanically. A column 1a contains typically the beam generator, the electron optical lenses and equipment for observing and registering an image.

The two walls of the building are designated by

reference numerals

5 and 6, respectively. A walking platform 7 is connected by horizontal beams with the outer wall 6. The beams pass, without touching, through the inner wall 5. The depth T with which the

building

5, 6 is anchored in the earth should, as is possible, be more than meters.

The column 10 of an electron microscope 1 is carried by a heavy foundation by means of a plate 2 and three supports 3. The foundation can weigh approximately 10 to metric tons and be suspended pendulously by several nylon lines 8 from the ceiling of the inner wall 5. For this purpose, three nylon lines can be used, for example. The supports 3 and the suspension of the foundation 4 pass, without touching, through the walking platform 7. Low frequency air springs 9 can be arranged in the pullies of the nylon lines 8 for limiting or attenuating vertical swinging movements. The pendulum length L can, for example, amount to 10 meters, so that the foundation 4 with the column la has a swinging movementfrequency of approximately 1/6 Hz.

The control console 1b is carried by the walking platform 7 and the latter also includes the observers place. Therefore, no vibration on the microscope column is imparted by the movements of the observer on the walking platform 7 or by actuating the control console lb, for example, by turning the positioning and adjusting knobs or by throwing switches. The control console lb is connected with the column 1a by means of flexible conductors. As conductors, in this connection, the

electrical conductors which, for example, are used for supplying current to the lenses and for supplying the positioning motors are especially to be considered. Also, mechanical movements can be undertaken, for example, movement of the specimen table by means of flexible shafts which run between the control console lb and the column la. Also, the cooling water conduits which connect with the column la and which are not directed via the control console lb should be as flexible as possible. The prevacuum pump can be arranged on the Walking platform 7. It, too, is connected to the high vacuum pump arranged directly on the column. The connection can be made with a flexible vacuum conduit, for example, in the form ofa rubber hose or bendable corrugated tube.

Because the

building

5,6 is double walled, with an intermediate air space 10, the inner building wall 5 is protected against outside air movements and ground movements. A wind force or ground force applied to the outer wall 6 does not lead, therefore, to a vibration of the inner wall 5 from which the foundation 4 with the column 1a are suspended.

Beneath the foundation 4 is a concrete column 11 on which the foundation 4 can be lowered. Above the microscope 1 there is an intermediate ceiling 12.

For further stabilizing the microscope la, there is provided a strengthening support which includes essentially the plate 2, three struts 13 and an annular member 14; this additional feature will be explained below in connection with FIGS. 3 to 5.

In the embodiment according to FIG. 2', foundation 4 carries the microscope column 1a as in FIG. 1. Here, however, the foundation is supported by several steel columns 20 which, for example, can be three in number and be in the form of rods or pipes. The steel columns 20 bend elastically and, therefore, make possible a swinging movement of the composite of the foundation 4 with the column 10. The steel beams 20 are anchored at a great depth, for example, 10 meters beneath the earths surface. The mass of the foundation 4 and of the column 1a on the one hand, and the elastic return force of the steel columns 20 on the other hand, are so dimensioned that the swinging movement period of the elastic pendulum corresponds to less than 1 Hz, for ex ample, l/5 Hz. The building 21 in which the micro scope 1 is arranged can, in this instance, consist ofonly one wall 21. The same reference numerals used in FIG. 2 as used in FIG. 1 correspond to similar items in FIG. 1.

In FIG. 3, the electron microscope with its carrying members is illustrated in detail. Here the same features as appear in FIG. 1 are designated with the same reference numerals. The column is again designated by reference numeral la and the control console configured in two parts is designated by reference numeral 1b. The plate 2, the three struts l3 and the annular member 14 which surrounds the column 1a, conjointly constitute the already mentioned strengthening support which here takes the form of a tetrahedral. The struts 13 can be, for example, steel pipes. Bending movement of the column 1a is effectively suppressed if the annular member 14 grips the column at its upper half, for example, at a location two-thirds the height of the column.

A table plate 15 can be joined to the control console 1b and arranged not to touch the plate 2 to serve as a shelf or writing surface for the observer.

FIGS. 4 and 5 show the upper portion ofthe strengthening support in elevation and plan view, respectively. Referring to FIG. 4, the annular member 14 comprises two parts, namely a ring 14a, which is secured rigidly or tightly to the struts l3, and a collar 14b, which by means of screws 15 is adjustable in a horizontal direction with respect to the ringv 14a. The collar 14b is joined tightly to the column by means of two conical clamping rings l6, l7 and screws 18. For a one sided adjusting of the screws 15, the collar 14b can be shifted horizontally in any desired direction. In this way, the column 1a can receive a corresponding bending prestress, which makes difficult, as already mentioned, an initiation of bending swing movements in the prestressed direction by means of earth vibrations. The column la is secured tightly to the plate 2 at its end cross section, see FIG. 3. The collar 14b can, by means of additional screws 19, be held in the desired position on the ring 14a.

In the illustrated embodiments, the rigid strengthening support includes several struts 13 which are arranged in the form of a pyramid, especially a tetrahedral. Instead of this kind of configuration using struts, a conical covering or jacket, for example, preferably made of metal, can be used, whose lower edge is braced against the plate 2 and whose upper edge is joined with the annular body 14.

While the invention has been described by means of specific examples and in specific embodiments, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art, without departing from the essential features of the invention and within the scope of the claims annexed hereto.

We .claim:

1. A charged particle-beam device such as an electron microscope or the like, comprising a column containing a beam generator, electron optical lenses and means for observing and registering an image, a foundation for carrying said column, supporting structure for said foundation to permit swinging movement at a low characteristic frequency of not more than 1 Hz, a platform, a control center configured as a desk console and arranged on said platform, said platform being separate from said foundation and having space sufficient for accommodating an operator of the particle-beam device, flexible transmission means for connecting said control center with said column, and pendular suspension means for pendulou'sly suspending said foundation from said supporting structure, said pendular suspension means including a plurality of parallel cables.

2. A charged particle-beam device according to claim 1, said suspension means comprising low frequency air springs for attenuating vertical swinging claim 1, wherein a double wall building surrounds the particle-beam device, the two walls of said building being mutually separated by an intermediate air space at the top and sides of said building, and pendular suspension means for pendulously suspending said foundation from the ceiling of the inner wall of said building, said platform being joined to only the outer wall of said building, said pendular suspension means including a plurality of parallel cables.

4. A charged particle-beam device according to claim 3, wherein said two walls extend to a depth of at least 10 meters into the earth at the sides of said buildmg.

5. A charged particle-beam device according to claim 1, comprising a rigid strengthening support braced against said foundation, said support having a base joined to the lower end of said column and a top part embracing said column at its upper half portion.

6. A charged particle-beam device according to claim 5, said support being configured so as to have a pyramidal shape.

7. A charged particle-beam device according to claim 5, said support being configured so as to have a conical shape.

8. A charged particle-beam device according to claim 5 said top part of said strengthening support comprising a collar, and adjusting means engaging said collar for positioning said collar horizontally with respect to said column for imparting a bending pre-stress to the latter.

9. A charged particle-beam device such as an electron microscope or the like, comprising a column containing a beam generator, electron optical lenses and means for observing and registering an image, a foundation for carrying said column and being supported to permit swinging movement at a low characteristic frequency of not more than 1 Hz, a platform, a control center configured as a desk console and arranged on said platform, said platform being separate from said foundation and having space sufficient for accommodating an operator of the particle-beam device, and flexible transmission means for connecting said control center with said column, said foundation comprising a base portion and at least one vertical bar upon which the base portion rests, said bar having elastically bendable characteristics.

10. A charged particle-beam device according to claim 9, said bar being anchored in the earth to a depth of at least 10 meters below the earths surface.

Claims

1. A charged particle-beam device such as an electron microscope or the like, comprising a column containing a beam generator, electron optical lenses and means for observing and registering an image, a foundation for carrying said column, supporting structure for said foundation to permit swinging movement at a low characteristic frequency of not more than 1 Hz, a platform, a control center configured as a desk console and arranged on said platform, said platform being separate from said foundation and having space sufficient for accommodating an operator of the particle-beam device, flexible transmission means for connecting said control center with said column, and pendular suspension means for pendulously suspending said foundation from said supporting structure, said pendular suspension means including a plurality of parallel cables.

2. A charged particle-beam device according to claim 1, said suspension means comprising low frequency air springs for attenuating vertical swinging movements of the composite of said foundation and said column.

3. A charged particle-beam device according to claim 1, wherein a double wall building surrounds the particle-beam device, the two walls of said building being mutually separated by an intermediate air space at the top and sides of said building, and pendular suspension means for pendulously suspending said foundation from the ceiling of the inner wall of said building, said platform being joined to only the outer wall of said building, said pendular suspension means including a plurality of parallel cables.

4. A charged particle-beam device according to claim 3, wherein said two walls extend to a depth of at least 10 meters into the earth at the sides of said building.

8. A charged particle-beam device according to claim 5, said top part of said strengthening support comprising a collar, and adjusting means engaging said collar for positioning said collar horizontally with respect to said column for imparting a bending pre-stress to the latter.

10. A charged particle-beam device according to claim 9, said bar being anchored in the earth to a depth of at least 10 meters below the earth''s surface.