DE1192760B - Arrangement in corpuscular beam devices, in particular electron microscopes, for removing and inserting pole shoe systems or parts thereof - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN S / fflWWl · PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
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HOIj

German class: 21g-37/10

S 83762 VIII c / 21g
February 15, 1963
May 13, 1965

The invention relates to an arrangement in particle beam devices, in particular electron microscopes, for removing and inserting pole shoe systems or parts thereof from or into the bore of a magnetic pole piece lens, whose the magnetic flux generating parts surround the inserted pole shoe system laterally.

With magnetic pole piece lenses, as they are in corpuscular beam devices, in particular electron microscopes are used, it is often necessary the pole shoe system or parts thereof located in the bore of the lens to remove the hole and, if necessary, another pole shoe system or parts of it in the Introduce hole.

This is the case, for example, if one does not, or not only, changes the example Use the magnetic flux generated in a winding to change the focal length of the lens want, but also the possibility of gradually adjusting the focal length by changing it the geometry of the magnetic flux acting on the corpuscular beam Parts of the lens, i.e. the pole piece system.

It is also used to carry out direct diffraction examinations, which are to be made, for example, with electron microscopes, required the entire pole shoe system from the Remove the hole in order to allow the largest possible diffraction cone to pass through.

The removal or replacement of pole shoe systems or parts thereof is known per se. at Pole shoe lenses, which are constructed in such a way that the pole shoe systems or the parts to be removed thereof arranged above or below the parts of the lens which are used to generate the magnetic flux you can, as is the case with many electron microscopes, a pole shoe turret use, which takes several pole shoe systems or parts thereof and these by rotation about an axis running eccentrically to the axis of the corpuscular beam optionally into the Pivoting the beam path is permitted. It is also known to have a holder for several pole pieces use, in which the pole shoe systems are arranged one behind the other and by sliding the Holder can optionally be brought into the beam path.

It does not always have to be a complete pole piece system, each consisting of two pole pieces; rather, it is also known to arrange in corpuscular beam devices,
especially electron microscopes, for
Removal and insertion of pole shoe systems
or parts of it

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,

Munich 2, Witteisbacherplatz 2

Named as inventor:

Horst Schmidt,

Willi Schomburg,

Hans-Joachim Kempien,

Dr. Karl-Heinz Herrmann, Berlin

for the purpose of gradually changing the focal length of the pole piece lens, assign a fixed pole piece to it and this optionally one with regard to the pole shoe bore and / or gap according to the desired Facing focal length dimensioned second pole piece.

The use of such pole shoe changing devices, which allow a shift in the pole shoe systems or make the parts thereof in a plane transverse to the axis of the corpuscular beam is but limited to lenses in which the pole shoe systems or the parts to be removed from them located outside of the lens parts used to generate the magnetic flux. Well have However, with regard to the magnetic conditions, such lenses have proven to be particularly advantageous, in which the pole shoe system used is within the magnetic flux generating lens parts is located, so these surround the pole shoe system used laterally.

In order to achieve a step-by-step change in the focal length of the described To be able to do this, it is known to supply the flux with permanent magnetic lenses to form the pole pieces like a yoke. Such a construction is in view of the magnetic Conditions are unfavorable mainly because there is a strong external magnetic field. One

509 569/273

Another solution provides several pole shoe systems arranged one behind the other in the beam path, which by means of a drive that can be actuated from outside the vacuum chamber is moved in the direction of the beam axis and can therefore optionally be used. However, this construction allows removal the pole shoe systems from the pole shoe bore, as they are used to carry out direct diffraction examinations is not required and also enables the focal length to be changed in stages only within certain limits.

These disadvantages are avoided if, according to the invention, above and / or below the pole piece lens actuatable by means that are inserted into the vacuum housing of the corpuscular beam device are provided that when the respective pole shoe system or parts thereof are in the beam path of the corpuscular beam device, a longitudinal movement in the direction of the particle beam axis and, if the respective pole shoe system or the parts thereof by longitudinal movement out of the bore are removed, a pivoting movement of the pole shoe system or the parts thereof transversely to the corpuscular beam axis enable. These can be electromagnetic or permanent magnetic lenses.

The means can be used by longitudinal and pivoting movement of the respective pole shoe system to generate a free bore in its entirety for direct diffraction studies; But you can also change the focal length of the pole piece lens in coarse steps Carry out the longitudinal and swivel movement of only one pole piece of the respective pole piece system. the Free bore can also serve as a lens with a long focal length, with one pivoted into the beam path Intermediate screen forms the aperture. If the means are available several times, so can exchange pole shoe systems or parts thereof with them.

In an advantageous embodiment of the arrangement described, the means are on the Arranged upper and / or lower surface of the pole shoe lens body and with their drives over Joints permitting movements of the pole piece lens connected. This construction principle offers the possibility to use the pole piece lens in to move any directions in a plane transversely to the corpuscular beam without a Influence of the means described occurs or these hinder the lens movement.

The means expediently contain a holder for the respective pole shoe system or the Parts thereof, the one with one of the drives in connection device for longitudinal movement of the respective pole shoe system or the parts thereof; furthermore, the holder is to be carried out the pivoting movement of the respective pole shoe system or the parts thereof by means of one of it associated pivoting device connected to one of the drives. While so in this embodiment only the pole shoe system or the movable ones in the longitudinal movement Parts of it take part, the pivoting movement is both of the holder and of those held in it Parts of the pole shoe system carried out.

In this embodiment, the holder can essentially consist of the respective pole shoe system or the parts thereof receiving after removal from the bore, against rotation about the corpuscular beam axis secured and with longitudinal slots running in the direction of the corpuscular beam axis provided guide sleeve and a surrounding threaded sleeve exist, which by means of the their associated drive rotatable about the corpuscular beam axis and with an internal thread, preferably large slope, is provided. Your internal thread

ίο causes in cooperation with cam-like, extensions on the respective pole shoe system that extend through the longitudinal slots in the guide sleeve or the parts thereof when the threaded sleeve is rotated, the longitudinal movement.

In order to keep the friction as small as possible, the cam-like extensions advantageously carry rollers in the area of the longitudinal slots and in the area of the internal thread.
With corpuscular beam devices in which the

If the object and the corpuscular beam are in a vacuum, it is important to use as few as possible Bushings through the vacuum housing of the device get along. For this reason, the Pivoting device expediently a coupling through which the to generate the longitudinal movement Serving drive is also used to generate the pivoting movement.

This is characterized by the requirement of only one drive and thus only one vacuum-tight implementation The distinctive variant expediently provides for the arrangement of a parallel to the corpuscular beam axis extending, with the guide sleeve firmly connected axis on the pole shoe lens body between the holder and the drive before, which rotatably carries a driven by the drive first coupling half, which by means of a lever with one on the Rotation of the axis participating second coupling half. Can be brought into engagement, so that then actuation of the drive instead of rotating the threaded sleeve causes the holder to pivot.

Another embodiment is in the sense of largely avoiding vacuum-tight feedthroughs of the drive for the longitudinal and the pivoting movement in such a way that it is at the same time the Has actuating means for the lever.

To limit the pivoting movement, expediently in the two opposite one another Pivoting directions, adjustable stops serve on the pole piece lens body or else arranged on a base plate attached to this and supporting the axis for the coupling halves are.

Often it is desirable by means of an intermediate screen and a window in the vacuum wall of the device to be able to view an intermediate image above the projective lens. In addition to the described Construction is therefore proposed that an intermediate screen under the action of a Spring rests against the holder and after its pivoting out of the beam path in turn the spring action is pivoted into the beam path.

Around the intermediate screen with the holder for the pole shoe system pivoted out of the beam path or to remove the parts thereof from the beam path as well, is expediently an actuator present, which by lifting the spring

5 6

effect keeps the intermediate screen in its position To keep the friction forces to be overcome outside of the beam path. This device lends to keep small, carry the extensions 13, 14 im can work in such a way that between the loading area of the longitudinal slots 17, 18 and the internal actuator and the intermediate screen a thread 19 rollers 22, 23 or 24, 25.
Knee lever is arranged, one leg of which is in FIG. 5 Both the guide sleeve 15 and the connection with the actuating member and the threaded sleeve 20 have, on their lower support, the other leg with a fork-like guide surface recesses 12 a, which are dimensioned so that they can be pivoted on one mounted carrier for that the holder 12 cooperates pivoted out of the beam path end screen. can be when the pole shoe system 5 in the

The arrangement described is used in the following to bore 9. The extensions 13 and 14

on the basis of the execution shown in the figures are then on the lens body 3, while

example explained. The rollers 22 and 24 are exposed so that they are from

F i g. 1 shows a vertical section through the internal thread 19 of the guide sleeve 15 again

eating parts of a corpuscular beam device can be grasped,

for example an electron microscope; 15 Securing the guide sleeve 15 against rotation

F i g. 2 shows a horizontal section in height around the corpuscular beam axis 16 in this

of these parts and finally the exemplary embodiment given by the fact that the

F i g. 3 a plan view of the holder. approximately sleeve 15 which is also on the base plate 26

Enclosed within the axis 27 arranged by the vacuum housing 1 of the. The axis 27 ver-corpuscular beam device The enclosed vacuum 20 runs parallel to the particle beam axis 16 and is located in this exemplary embodiment between the holder 12 and the drive 11 attached electromagnetic pole shoe lens that arranges for example. It is through the pegging 28 as well the projection of an electron microscope shows the bearing part 15 a attached to the guide sleeve 15 represents. The rotationally fixed connection to the guide sleeve 15 which generates the magnetic flux. on The energizing winding 2 is of the flux guide 25 of the axis 27 is rotatable the first coupling half Nenden actual lens body 3 surrounded. The 29 arranged, which by means of the lever 30 with the The lens body 3 points in the direction of the magnetic second, which is non-rotatably arranged on the axis 27 Flux with non-magnetic material, with coupling half 31 can be connected. The second way of coupling Brass, filled recess 4, lung half 31 is therefore firmly seated on the axis 27, through the magnetic flux is forced in 30 rend the first coupling half 29 when actuated the pole shoes 6 of the drive 11, which form the pole shoe system 5, can rotate, since the rotation and 7, between which the lens movement of the drive via the gears 32, 33 gap 8, in which the influence of the corpuscular on the first coupling half 29 and over the The beam is followed by the magnetic field of the pole piece lens, gears 34, 35 onto the threaded sleeve 20, extends. 35 will wear.

The arrangement solves in this embodiment the lever 30, when actuated, that, for example, the task of removing the entire pole shoe system 5, the second coupling half 31 against the action of the spring 36 in engagement with the first coupling half or from the bore 9 of the pole piece lens. to be used again in order to bring about a possibility of 29, so that now a firm coupling of diffraction receptacles can be created with a free hole between the first coupling half 29 and the joint. To solve this problem, an upper surface of the pole piece lens body 3 is provided on the axis 27 via the second coupling part 31. For this reason, an arrangement is now provided that is no longer connected to the drive 11 via the articulated connection of the drive 11, which would allow a coordinate movement of the pole piece or the threaded sleeve 20 and thus a longitudinal movement of the lens. 45 of the pole shoe system 5, but a pivot. This arrangement contains the holder 12, which by means of the entire arrangement around the axis 27 protrudes from the cam-like extensions 13 and 14 on the pole. With 26 b is a guide rail bezeichschuhsystem5 (see in particular Fig. 3) this holds. net. The pin 28 moves in an off-The holder 12 consists essentially of the savings in the extension 26 a of the base plate 26. The pole shoe system 5 after removal from the bore 9 50 holder 12 with the bearing part 15 a takes after this receiving guide sleeve 15 which, in a pivoting movement that has yet to be performed, in the manner shown in broken lines in FIG.

This axis extending longitudinal slots 17,18 ver The lever 30 is by means of the actuating sleeve see is. Furthermore, the 55 37 brought into effect in the drive 11 belongs to the holder 12. He will Guide sleeve 15 surrounding, with the two-start then around the axis 38 in its support 39, the inner thread 19 provided threaded sleeve 20, which acts as a guide for the drive shaft 40 of the drive. by means of the actuated by the button 21 drive drive 11 is used, pivoted so that it is with 11 is rotatable about the particle beam axis 16. his two on the collar-like ledge

It can be seen that a rotation of the threaded sleeve 60 41 rests on the second coupling half 31

20 with its internal thread 19 a longitudinal movement ends this coupling half, which by means of the in

of the pole shoe system 5 due to the interaction of elongated holes guided pin 42 rotatably with the

its cam-like extensions 13,14 is connected to the inner axis 27, against the action of the

Thread 19 causes the leadership of the continued spring 36 pushes down.

sets 13, 14 in the longitudinal slots 17, 18 of the against 65. The actuating sleeve 37 can be by means of the

Rotation about the particle beam axis 16 secured second button 43 of the drive 11 in the direction

th guide sleeve 15 the rotation of the pole piece move transversely to the axis 16 of the corpuscular beam,

systems 5 prevented. the rotary movement of the knob 43 via the

Thread 44 is converted into the displacement movement of the socket 37.

It is understood that there is also a possibility of securing against pivoting of the holder 12, which is effective as long as the pole shoe system 5 is still located within the pole shoe bore 9, is provided can be; it is expediently through appropriate design of the coupling or the drive elements for the lever 30 are formed. This is used in the exemplary embodiment shown the hold-down 70 held by a pin, the lower surface of which is profiled so that the lever can only move darm into the position shown when the holder 12 is pivoted into the beam path is. Fig. La shows the lower surface of the hold-down 70 and the formation of the Lever 30.

To limit the pivoting movement, as shown in FIG. 2 reveals adjustable stops 45 and 46, which in this embodiment are formed by eccentric screws, in the base plate 26 or the pole shoe lens body 3 is arranged.

To limit the rotational movement of the threaded sleeve 15, the stop 71 is used, which is provided with a corresponding, Stop, not shown in the figures, cooperates on the threaded sleeve 20.

The image generated by the corpuscular beam is often viewed from above, for example the projective lens of an electron microscope is desirable, including in the one shown in the figures Embodiment of the intermediate screen 47 is used. It rests under the action of the spring 48 the holder 12 and is accordingly activated by the spring action after the holder 12 has been pivoted from the beam path in turn into the beam path, d. H. into that designated in Fig. 2 with 47 ' Location, panned.

Since there is often a desire to have neither the PoI shoe system nor the intermediate screen in the To have a beam path, the actuator 49 is provided in the embodiment according to the figures, that by canceling the action of the spring 48, the intermediate screen in the Holds position outside the beam path when the holder 12 is pivoted into the position indicated by 15 a will. This actuator consists essentially of the actuator axis 50 and the with this connected union-like button 51, which is broken after pressing the axis 50 in the position shown can be secured in this position by turning.

The position of the axis 50 shown in dashed lines corresponds to the position shown in solid lines for the provided for holding the intermediate screen 47 in its position outside the beam path Lever. It is pivotable about the axis 52 between the actuating member 49 and the intermediate screen 47 the toggle lever 53 is arranged, one leg of which is in connection with the axis 50 and its other leg with the fork-like guide 54 on the pivoted about the axis 55 Support 56 for the intermediate screen 47 cooperates.

It is often desirable to get by with relatively weakly dimensioned drives. For this is it is necessary to weaken the magnetic flux at least when the pole shoe system or the parts thereof are to be moved in the longitudinal direction, d. H. while moving under the influence of the force produced by the magnetic field. A functional one Further development for the case of an electromagnetic pole piece lens therefore looks like that described Means actuated contacts before which during the longitudinal movement at least a reduction the number of ampere turns of the pole piece lens. Generally one will be during

ίο the longitudinal movement the number of ampere turns up to decrease to the value zero.

Reducing the number of ampere-turns can either be achieved by reducing the number of turns Excitation winding through the contacts with constant excitation current (switching in the area of the winding) or by reducing the excitation current with a constant number of turns. Understandably the contacts can be switched in such a way that • they carry out both measures at the same time.

The same or additional contacts can also be used to provide a device for displaying the position to operate the pole shoe system or parts thereof and / or the respective position of the holder. Such a use of contacts is of course not in the case of an electromagnetic one Lens limited.

Conveniently, the contacts have several positions that are chosen so that from the Beam path pivoted pole shoe system in order to achieve a long focal length a reduction the number of ampere turns is made that the contacts, however, are located in the beam path Pole shoe system, but with the holder pivoted out of the beam path, the full number of ampere-turns turn on; during the longitudinal movement of the pole shoe system, the contacts then take place again at least a reduction in the number of ampere-turns, so that the drives are loaded as little as possible will.

This advantageous further development should be based on the example shown schematically in FIGS. 4 to 6 explained. In these figures the contact positions are for three different positions of the pole shoe system 5 and two different positions of the holder 12 are shown. One recognises, that in the vacuum housing 1 of the particle beam device in this embodiment, a contact arrangement 81 is inserted, the actuating member of which is the plunger 82, of the three bearing surfaces 83, 84 and 85, of which one in each case corresponds to the position of the pole shoe system 5 or of the holder 12 cooperates with one of these parts. For this purpose, the holder 12 has a correspondingly shaped one Recess for the plunger 82.

In the case of FIG. 4, the pole shoe system 5 and the holder 12, the structure of which is shown in FIG. 1 to 3 has been explained, from the beam path pivoted, d. i.e., those shown in FIG. 1 with 9 designated hole of the pole shoe lens is for example to achieve a long focal length. Since this z. B. only half the number of ampere turns required is, by means of the supporting surface 83 of the cooperating with the pole shoe system 5 Plunger 82, the contact 86 closed by snapping into the recess 88, for example, while the contact 87 is located outside the recess 89 assigned to it and accordingly in the example is open.

F i g. 5 illustrates the case in which the pole piece system 5 is in the bore 9 of the pole piece lens is located and the holder 12 is pivoted out of the beam path. The full number of ampere-turns is switched on by the contacts 86 and 87 that now the support surface 84, which is with the circumference of the holder 12 cooperates for the position of the plunger 82 and thus its recesses 88 and 89 is decisive. As a result, the contact 87 is now closed, but the contact 86 open.

Fig. 6 shows the contact position during the longitudinal movement of the pole shoe system, i. H. then, when both the pole shoe system 5 and the holder 12 are in the beam path of the corpuscular beam device are located. For this reason, the two parts mentioned are not shown. Under the Action of a spring, not shown, the plunger 82 rests with its bearing surface 85 on a corresponding shaped counter surface in the vacuum housing 1, and the recesses 88 and 89 assume a position in which none of the contacts 86 and 87 is closed.

Understandably, this contact arrangement, which is only described schematically, can be largely used vary and adapt to the respective circumstances.

For example, it can also be useful to have a corresponding arrangement below the To provide pole shoe lens, so that then, for example, a pole shoe lens system with the upper arrangement and with the lower arrangement a second pole shoe lens system optionally into the bore 9 can be introduced or removed from it. It is also possible instead of the entire pole shoe system only to replace one pole piece of the system or to remove it from the bore 9 remove. Furthermore, if necessary, several of the arrangements described above or Provide below the pole piece lens. Another construction for the coupling can also be used use.

Finally, as indicated in FIGS. 7 to 9, it is also possible above or below the lens to provide two holders 60, 61 with corresponding pivoting devices, which can be divided into three different Positions can be brought: either the holder 61 is located in the beam path (FIG. 7), or the holder 60 is brought into the operating position (FIG. 8), or else both holders 60 and 61 are pivoted out of the operating position so that the intermediate screen 62 then protrudes into the beam path (Fig. 9). With such a construction, each of the holders is expediently a gripper executed after the end of the pivoting of the respective pole shoe system or the pole to be moved Parts of it from the beam path the pole shoe system or parts of it turns off and a another pole shoe system takes effect.

The described arrangement creates the possibility of pole shoe systems or parts then also to remove from the bore of a pole piece lens or to insert it into it, if Due to the construction chosen, the known ones that work with a simple pivoting movement Solutions are not applicable. Because the intended means outside of the magnetic Circle of the pole shoe lens, do not call them

Effect of the lens out disturbing influences.

Claims (21)

Patent claims: 1. Arrangement in particle beam devices, in particular electron microscopes, for removal and inserting pole shoe systems or parts thereof from or into the bore a magnetic pole piece lens, the parts of which generate the magnetic flux that are used Laterally surrounded pole shoe system, characterized in that above and / or below the pole shoe lens through into the vacuum housing (1) of the corpuscular beam device used drives (11) actuatable means are provided which, when the respective pole shoe system (5) or the parts thereof are located in the beam path of the particle beam device, in the direction of the particle beam axis (16) a longitudinal movement and, if the respective pole shoe system (5) or the parts thereof are removed from the bore (9) by longitudinal movement, a pivoting movement of the pole shoe system (5) or the parts thereof enable transverse to the particle beam axis (16). 2. Arrangement according to claim 1, characterized in that the means on the upper and / or the lower surface of the pole shoe lens body (3) and arranged with their drives (11) via articulated connections (10) permitting movements of the pole piece lens are. 3. Arrangement according to claim 1 or 2, characterized in that the means have a Contain holder (12) for the respective pole shoe system (5) or the parts thereof, the one with one of the drives (11) connected device for the longitudinal movement of the respective Pole shoe system (S) or the parts thereof, and that the holder (12) for implementation the pivoting movement of the respective pole shoe system (5) or the parts thereof by means of a swiveling device assigned to it and connected to one of the drives (11) is pivotable. 4. Arrangement according to claim 3, characterized in that the holder (12) substantially from one the respective pole shoe system (5) or the parts thereof after removal the bore (9) receiving, secured against rotation about the corpuscular beam axis (16) and provided with longitudinal slots (17, 18) running in the direction of the particle beam axis (16) Guide sleeve (15) and one surrounding it, connected to it by means of the Drive (11) rotatable about the corpuscular beam axis (16), with an internal thread (19), preferably large pitch, provided threaded sleeve (20), the internal thread (19) in cooperation with cam-like, through the longitudinal slots (17, 18) in the guide sleeve (15) penetrating extensions (13, 14) on the respective pole shoe system (5) or the Parts of it causes the longitudinal movement when the threaded sleeve (20) is rotated. 5. Arrangement according to claim 4, characterized in that the cam-like extensions 509 569/273 (13, 14) in the area of the longitudinal slots (17, 18) and in the area of the internal thread (19) rollers (22, 23, 24, 25) wear. 6. Arrangement according to one of claims 3 to 5, characterized in that the holder (12) such selected recesses (12 a) for the cam-like extensions on its lower surface (13, 14) has that when the respective pole shoe system (5) or the parts thereof are in the beam path from which the beam path can be pivoted. 7. Arrangement according to one of claims 3 to 6, characterized in that the pivoting device contains a coupling through which the drive (11) serving to generate the longitudinal movement is also used to generate the pivoting movement is used. 8. Arrangement according to claim 7, characterized in that the pole piece lens body (3) between the holder (12) and the drive (11) a parallel to the corpuscular axis (16), with the guide sleeve (15) fixedly connected axis (27) is arranged, which is rotatable a first coupling half (29) driven by the drive (11), which by means of an as Lever (30) with a second coupling half participating in the rotation of the axis (27) (31) can be brought into engagement, so that the actuation of the drive (11) instead of the Rotation of the threaded sleeve (20) causes the holder (12) to pivot. 9. Arrangement according to claim 8, characterized in that the drive (11) for the Longitudinal and pivoting movement of the respective pole shoe system (5) or parts thereof at the same time the actuating means for the lever (30). 10. Arrangement according to claim 8 or 9, characterized in that on the axis (27) a hold-down device (70) for the lever (30) is arranged, which this only when in the beam path pivoted holder (12) releases. 11. Arrangement according to one of claims 1 to 10, characterized in that for the limitation the pivoting movement, expediently in the two opposite pivoting directions, adjustable stops (45, 46) are provided on the pole shoe lens body (3). 12. Arrangement according to one of claims 3 to 11, characterized in that a Intermediate screen (47) rests against the holder (12) under the action of a spring (48) and after its pivoting out of the beam path in turn by the spring action in the Beam path is pivoted. 13. Arrangement according to claim 12, characterized in that an actuating member (49) is present, which by canceling the spring action, the intermediate screen (47) in its Position outside of the beam path. 14. Arrangement according to claim 13, characterized in that between the actuating member (49) and the intermediate screen (47) a toggle lever (53) is arranged, one of which Leg is in connection with the actuator (49) and the other leg with a fork-like guide (54) on a pivotably mounted carrier (56) for the Intermediate screen (47) interacts. 15. Arrangement according to one of claims 1 to 14, characterized in that when used an electromagnetic pole piece lens actuated by the means (86, 87) are provided that during the longitudinal movement at least a reduction in the number of ampere turns the pole piece lens. 16. The arrangement according to claim 15, characterized in that the contacts (86, 87) are several Have positions and with the pole shoe system (5) pivoted out of the beam path reduce the number of ampere turns to achieve a long focal length, with the pole shoe system (5) in the beam path and pivoted out of the beam path Switch on the holder (12) to the full number of ampere turns and at least during the longitudinal movement of the pole shoe system (5) reduce the number of ampere-turns. 17. Arrangement according to claim 15 or 16, characterized in that the contacts (86, 87) are inserted into the vacuum housing (1) of the corpuscular beam device and via the plunger (82) actuated by the means and possibly the pole shoe system (5) or parts thereof will. 18. Arrangement according to one of claims 15 to 17, characterized in that the contacts (86, 87) or other contacts a device for displaying the position of the pole shoe system (5) or the parts thereof and / or the position of the holder (12). 19. Arrangement according to one of claims 1 to 18, characterized in that the means by longitudinal and pivoting movement of the respective pole shoe system (5) in its entirety for direct diffraction examinations or to achieve a long focal length a free bore (9) generate. 20. Arrangement according to one of claims 1 to 18, characterized in that the means for a coarse change in the focal length of the pole piece lens, the longitudinal and pivoting movement a pole piece (6, 7) of the respective pole piece system (5). 21. Arrangement according to one of claims 1 to 20, characterized in that the means are present several times and an exchange of pole shoe systems or parts thereof make. In addition 3 sheets of drawings 509 569/273 5.65 © Bundesdruckerei Berlin