System for reducing vibrations

Abstract

A system (2) is disclosed for reducing vibrations is disclosed. The system (2) comprises a first element (4), a second element (6), and one or more spring systems (12a,12b,12c), preferably geometric anti-spring systems (12a,12b,12c), that are configured to prevent vibrations, in particular vertical vibrations, from travelling from the first element (4) to the second element (6). Each spring system (12a,12b,12c) of the one or more spring system (12a,12b,12c) comprises a plurality of compressed springs (14). Further, each spring (14) out of the plurality of compressed springs (14) comprises a first end (A) and a second end (B). Herein, the first end (A) is connected to the first element (4) and the second end (B) is connected to the second element (6). Further, the plurality of compressed springs (14) comprises a first spring and a second spring and a distance (d1) between the first end (A) of the first spring and the second end (B) of the first spring is equal to or larger than a distance (d2) between the first end (A) of the first spring and the second end (B) of the second spring.

Description

[0001] System for reducing vibrations

[0002] FIELD OF THE INVENTION

[0003] This disclosure relates to a system for reducing vibrations, in particular to such system comprising one or more spring systems, preferably one or more geometric anti-spring systems. This disclosure further relates to a cryogenic device comprising such system for reducing vibrations.

[0004] BACKGROUND

[0005] Systems for reducing vibrations comprising so-called geometric anti-spring systems (GAS) are known in the art. Geometric anti-spring systems are typically used to prevent vertical vibrations from reaching some element, such as an optical table. The following references disclose systems for reducing vibrations that comprise geometric anti-spring systems:

[0006] -{Bertolini et al. I Nuclear Instruments and Methods in Physics Research A 435 (1999) 475 - 483}, and

[0007] -{G. Celia et al. I Nuclear Instruments and Methods in Physics Research A 540 (2005) 502 - ni et al. I New seismic atenuation system (SAS) for the advanced LIGO configurations Conf. Proc. 523, 320-324 (AIP, 2000)}, and no et al. I The Seismic Atenuation System (SAS) for the Advanced LIGO gravitational metric detectors. I Nucl. Instrum. Methods Phys. Res. Sect. Accel. Spectrometers Detect. Assoc. Equip. 598, 737-753 (2009)}, and

[0008] -{Beker et al. I Seismic Atenuation Technology for the Advanced Virgo Gravitational Wave Detector I Phys. Procedia 37, 1389-1397 (2012)}.

[0009] A drawback of these known vibration reduction systems is that they are relatively large, which complicates their use in experimental set-ups in which the available space is limited. To illustrate, the space below optical tables is usually quite limited. Hence, there is a need in the art for more compact systems for reducing vibrations.

[0010] SUMMARY

[0011] To that end, a system for reducing vibrations is disclosed. The system comprises a first element, a second element, and one or more spring systems, preferably geometric anti-spring systems, that are configured to prevent vibrations, in particular vertical vibrations, from travelling from the first element to the second element. Each spring system of the one or more spring systems comprises a plurality of compressed springs. Further, each spring out of the plurality of compressed springs comprises a first end and a second end. Herein, the first end is connected to the first element and the second end is connected to the second element. Further, the plurality of compressed springs comprises a first spring and a second spring and a distance between the first end of the first spring and the second end of the first spring is equal to or larger than a distance between the first end of the first spring and the second end of the second spring. This system allows for very compact designs. In known geometric anti-spring systems, for example, the compressed springs are radially disposed around a central element and each spring has a first end connected to some other element and a second end connected to the central element. Hence, in such known systems, a first end of one spring will never sit relatively close to a second end of another spring. Herein, relatively close may be understood as closer than a length of the spring itself as viewed in a vertical direction. Such known geometric anti-spring systems, roughly speaking, occupy an area of at least IT * L2, wherein L indicates the length of the compressed spring as viewed in a vertical direction. However, in the vibrations reduction system disclosed herein, a first end of one spring is indeed positioned relatively closely to a second end of another spring, which allows for a compact design. For proper functioning of the GAS it is not strictly required that the respective second ends of the springs are connected to the second element at roughly the same position. The respective second ends can very well be connected to the second element at quite different positions. Hence, indeed, a second end of at least one compressed spring can sit relatively close to a first end of another compressed spring. The area occupied by a vibrations reduction system as disclosed herein can thus be far smaller than IT * L2.

[0012] As referred to herein, a spring system may be understood as a smallest set of compressed springs of which a horizontal component of a vector sum of the forces respectively exerted on the second element by these springs equals zero.

[0013] Typically, the springs of a geometric anti-spring system are critically loaded, meaning that the mass is chosen such that at a given horizonal pre-tension, the total forces lead to a very low effective spring constant in the vertical direction.

[0014] Any spring system referred to in this disclosure may be a geometric anti-spring system. A geometric anti-spring system may be understood as a spring system having critically loaded springs that are geometrically arranged for reducing the spring system’s effective spring constant in the vertical direction, preferably for reducing the effective spring constant in the vertical direction as much as possible.

[0015] As referred to herein, a distance may indicate a horizontal distance, i.e. a distance as viewed in a vertical direction.

[0016] In an embodiment, the distance between the first end of the first spring and the second end of the first spring is at least twice, preferably at least three times, more preferably at least five times, the distance between the first end of the first spring and the second end of the second spring.

[0017] This embodiment is advantageous in that the first end of the first spring and the second end of the second spring are quite close to each other, thus allowing a very compact design.

[0018] In an embodiment, of at least one spring system, preferably of each spring system, each spring out of the plurality of compressed springs exerts a respective force on the second element in a first horizontal direction or in a second horizontal direction that is opposite the first horizontal direction.

[0019] Additionally or alternatively, all springs of each spring system are substantially parallel to each other, as viewed in a vertical direction, which allows for an even more compact design.

[0020] In an embodiment, one or more springs out of the plurality of compressed springs, preferably each spring out of the plurality of compressed springs, comprises steel and / or iron-containing alloys and / or titanium and / or titanium alloys and / or phosphorous bronze and / or molybdenum and / or beryllium copper and / or gold plated version of these materials.

[0021] Phosphorous bronze, beryllium copper and gold plated versions of for example steel and / or of iron-containing alloys and / or of titanium and / or of titanium alloysare beneficial because they in general lead to increased thermal conduction with leads to better, and faster thermalization.

[0022] In an embodiment, one or more springs out of the plurality of compressed springs, preferably each spring out of the plurality of compressed springs, is a pre-bent blade.

[0023] In an embodiment, the one or more spring systems comprises at least two spring systems. Having several spring systems is beneficial in that it can better cope with tilting motion.

[0024] In an embodiment, the one or more spring system comprises three and only three spring systems.

[0025] In an embodiment, the experiment is attached to a mass that is connected to the second element via a string.

[0026] In an embodiment, the first element is a first horizontally oriented plate and / or the second element is a second horizontally oriented plate. In such embodiment, the first element and second element may be arranged one below the other.

[0027] This embodiment further reduces the size of the vibrations reduction system. Especially if both the first and the second element are plate-shaped, they can be nicely arranged below each other herewith occupying only a limited space vertically.

[0028] A horizontally oriented plate may be understood to have a thickness extending in the vertical direction.

[0029] In an embodiment, the first element comprises one or more first apertures and the second element comprises one or more second protrusions at least partially extending through the one or more first apertures, wherein one or more second ends of one or more respective springs of one or more spring systems are connected to the one or more second protrusions. Additionally or alternatively, the second element comprises one or more second apertures and the first element comprises one or more first protrusions at least partially extending through the one or more second apertures, wherein one or more first ends of one or more respective springs of one or more spring systems are connected to the one or more first protrusions.

[0030] This embodiment enables to arrange the first and second element one below the other in a convenient manner. To illustrate, the second element can be positioned below the first element and can have protrusions that extend in the upward vertical direction through apertures in the first element. Then, springs of the one or more spring systems can simply be positioned on the first element such that their first end is connected to the first element and the second end is connected to the protrusion of the second element.

[0031] In an embodiment, the system comprises one or more inverted pendulums for reducing horizontal vibrations.

[0032] The inverted pendulums referred to herein may be any of the inverted pendulums as described in any of the references cited in the background section of this disclosure. In an embodiment, the system comprises a third element and one or more inverted pendulums that are configured to prevent vibrations, in particular horizontal vibrations, from travelling from the third element to the first element. Herein, the third element supports the one or more inverted pendulums and the one or more inverted pendulums support the first element.

[0033] In an embodiment, the second element, as viewed from a top view, has one or more outer edges and the second element is associated with a span distance, the span distance being equal to a largest distance, as viewed from a top view, that can be identified between any two points on any of the outer edges. In this embodiment, the system comprises a mass that is positioned at a distance from the second element by means of one or more elongated elements, such as pole-like elements, the distance being greater than half the span distance, preferably greater than the span distance.

[0034] In use, an experiment can be attached to the mass. This embodiment is advantageous in that due to the relatively long elongated elements, xy vibrations of the second element translate, at least to some extent, to a tilt and / or roll motion of the mass. In this manner, the mass (and thus any experiment attached to the mass) is not only isolated from z-vibrations, but also from xy vibrations. In some cases, when the pole is very long compared to the span distance, the gravitational force on the mass might further cause lower vibrations, similar to an inverted pendulum. Such embodiment is especially advantageous if tilt / roll is less of a problem for an experiment than xy vibrations.

[0035] The mass is preferably significantly heavier than the elongated structures.

[0036] Preferably, each elongated element is a relatively stiff element, for example made out of Al, Steel, Cu, or combinations thereof. Irrespective of this, each elongated element is typically connected at one end to the second element and at another end to the mass.

[0037] The mass may be positioned above or below the second element. If the mass is positioned above the second element, the one or more elongated elements support the mass. If the mass is positioned below the second element, then the mass is suspended from the second element via the one or more elongated elements.

[0038] An aspect of this disclosure relates to a cryogenic device, such as a dilution refrigerator. The cryogenic device comprises any of the systems for reducing vibrations disclosed herein. The cryogenic device is configured to cool down a space within the cryogenic device to below 80K. Preferably, the cryogenic device is configured to cool down that space to below 60K. More preferably, the cryogenic device is configured to cool down the space to below 50K, such as to below 5K. Further, the one or more spring systems are positioned in said space. The space may also be referred to herein as the cold space.

[0039] Such a cryogenic device is highly advantageous for experiments that require an environment that is to be kept at a very low temperature and is substantially without vibrations, such as scanning probe experiments or experiments to probe or investigate gravity or gravitational waves. The system for reducing vibrations disclosed herein, since it can be made very compact, can be conveniently placed inside of the cryogenic device. Having the spring systems inside of the cryogenic device enables to locally suppress vibrations. This is advantageous in that it reduces the risk of vibrations entering the system after the filter and reaching the space that should be kept without vibrations. To illustrate, if the cryogenic device would have one or more spring systems positioned at room temperature, then relatively long wires would be required that would hang from these spring systems all the way down into the lowest temperature regions of the cryogenic device. These spring systems would need to be physically connected to the cold parts of the cryostat to cool down the system, which in turn would lead to a picking up of external vibrations. Further advantages of having the spring systems inside of the cryogenic device are that no thermal gradient is required in the connection between room temperature GAS and low temperature, and that one generally has higher thermal stability at the GAS, and that no mechanical connection / opening is required from the cold part to the warm part.

[0040] If the cryogenic device is a dilution refrigerator that comprises a mixing chamber, then the one or more spring systems may be positioned in the mixing chamber and / or at the mixing chamber stage. The space referred to herein may thus be the mixing chamber of a dilution refrigerator.

[0041] In an embodiment, the cryogenic device comprises a cryocooler, such as a pulse tube (PT) cryocooler, GM cryocooler, or Joule-Tomson cryocooler.

[0042] The cryogenic device disclosed herein may comprise a cryocooler, which is a source of vibrations. This may be problematic if a vibration-less environment is required for an experiment. The cryogenic device disclosed herein enables the use of a cryocooler even when scanning probe experiments are to be conducted in the cryogenic device.

[0043] As used herein, a cryocooler may be understood as a device that is configured to cool down a space to below 120K. Typically, a cryocooler is used to precool some region in the cryogenic device to below 4K. This allows further cooling with liquified helium mixture.

[0044] In an embodiment of the cryogenic device, the system for reducing vibrations comprises a damping system that is configured to dampen vibrations of the second element by generating counteracting forces that act on the second element and that counteract the vibrations of the second element. The damping system comprises one or more conductive structures. Each conductive structure out of the one or more conductive structures has a first part that is positioned in the space and a second part that is positioned outside of the space. The first part comprises, preferably essentially consists of, more preferably consists of, superconductor material. Further, the damping system is configured to cause an electrical current in the first part when the damping system is generating the counteracting forces.

[0045] This embodiment is advantageous in that the damping system allows to dampen vibrations of the second element without having energy dissipation in the low temperature regions of the cryogenic device. Instead, the dissipation of current and possibly the generation of current will occur at higher temperatures where cooling power is higher, or at room temperature outside the cryogenic device. Of course, the skilled person will understand that for this to happen, the temperature of the first part should be below the critical temperature of the superconductor that forms the first part and / or that is present in the first part. Irrespective of whether the damping system is a so-called active system that is configured to actively generate the counteracting forces or a passive damping system, typically an electrical current will be present in the low temperature regions of the cryogenic device. This can be a current though a wire, or a current generated in any non-insulating material. To illustrate, for an active system, electrical currents are typically actively provided to one or more coils in the low temperature region so that these one or more coils can generate counteracting magnetic forces against each other or against permanent magnets. A passive system typically has a magnet that moves near an electrical conductor if some element is vibrating. The movement of the magnet near the electrical conductor causes currents in the electrical conductor that, in turn, cause magnetic forces that counteract the movement of the magnet. However, electrical currents in non-superconducting metals are undesired in the low-temperature regions of the cryogenic device as they may dissipate herewith representing a thermal load. Due to the first parts of the one or more conductive structures being superconductive during an experiment, no current dissipation occurs in these first parts. The dissipation would occur in the second parts of the conductive structures, which may be placed at room temperature, or at any temperature higher than the experiment temperature where cooling power is higher. The second part of the conductive structure may be electrically connected to a resistor (which may also be positioned at room temperature or at least at a higher temperature than the experiment temperature) so that the current dissipation occurs in the resistor.

[0046] Non-limiting examples of superconductor materials are NbTi, Al, and Nb.

[0047] In an embodiment, the damping system comprises a superconductor magnetic shield that at least partially surrounds, preferably completely surrounds, the first part of at least one conductive structure out of the one or more conductive structures. The superconductor magnetic shield is a superconductor element. This means that it becomes superconductive below some critical temperature. The superconductor magnetic shield is configured to block a magnetic field caused by the electrical current in the first part of the at least one conductive structure.

[0048] Preferably, the superconductor magnetic shield is configured to be superconductive when it has a temperature lower than 5K.

[0049] Superconducting magnetic shields generate just enough supercurrents to shield the magnetic field, but not more, so outside of the shield, there will not be any fields. Preferably, the damping system comprises a superconductor magnetic shield for each conductive structure out of the one or more conductive structures.

[0050] As referred to herein, a magnetic shield can comprise different shield elements, which are typically parts that overlap and / or that are concentric.

[0051] Typically, no or very few conductive but non-superconductive parts are inside the shielded area. In an embodiment, the damping system comprises a sensor that is configured to detect vibration of the second element. In this embodiment, the one or more conductive structures comprise a first conductive structure. The first part of the first conductive structure comprises one or multiple coils. Further, the damping system comprises an electrical current control system that is configured to cause an electrical current through the coil in dependence of the detected vibrations of the second element for causing the coil or the coils to generate magnetic forces as the counteracting forces. Preferably, in this embodiment, the damping system comprises a magnet, such as a permanent magnet, against which the generated magnetic forces can work.

[0052] In an embodiment, the electrical current control system is configured to provide a current to the coil, wherein the current has a constant direct current component so that a predetermined load is applied continuously to the compressed springs of the one or more spring systems. This embodiment is advantageous in that it enables to ensure that the springs of the anti-spring systems are always correctly loaded. Correctly loading these anti-spring systems is not trivial because the properties of the springs, such as the spring constants, may be different at very low, cryogenic temperatures than at room temperature. By providing a direct current (component) to the coil, the coil may be understood to, disregarding the generated counteracting forces to combat the vibrations, continuously generate a constant force on the first or second element. As such, this embodiment may be understood to enable to control the effective mass of the first and / or second element during an experiment in order to compensate for changing spring properties at very low temperatures.

[0053] Typically, the actually provided current would be a superposition of the currents required for compensating vibrations measured by the sensor and the direct current provided for finetuning the spring loading of the spring system. For this embodiment, the control system might also be placed on parts of the springs.

[0054] In an embodiment, the one or more conductive structures comprise a second conductive structure. The damping system comprises a magnet that is fixed to the first or second element. Further, the first part of the second conductive structure is fixed to the second or, respectively, first element. The first part of the second conductive structure and the magnet are positioned relative to each other such that movement of the magnet relative to the first part of the second conductive structure causes a current in the first part of the second conductive structure. The current is dissipated outside of the space, which causes a drag force on the magnet herewith causing the counteracting forces.

[0055] Advantageously, since the second conductive structure also comprises a second part that is positioned outside of the cold space, any electrical current generated in the first part will, if the first part is superconductive, dissipate in the second (non-superconductive) part of the conductive structure. The current dissipation thus occurs outside of the cold space. It should be appreciated that the current dissipation is required otherwise no vibrations are damped.

[0056] The first conductive structure and second conductive structure may be the same conductive structure.

[0057] One aspect of this disclosure relates to a method for controlling a current in any of the cryogenic devices disclosed herein that comprises a coil. The method comprises providing a current to the coil so that a predetermined load is applied continuously to the compressed springs of the one or more spring systems, wherein the current comprises a constant direct current component.

[0058] It should be appreciated that the damping system referred to herein can be advantageously used in any cryogenic device that comprises any system for reducing vibrations not necessarily the new system disclosed herein. Hence, a distinct aspect of this disclosure relates to any of the cryogenic devices disclosed herein that comprises any of the damping systems disclosed herein, yet that does not necessarily comprise a system for reducing vibrations disclosed herein.

[0059] Thus, a distinct aspect of this disclosure relates to a further cryogenic device that is configured to cool down a space within the cryogenic device to below 80K, preferably to below 60K, more preferably to below 50K, such as to below 5K, and that comprises a damping system. The damping system is configured to dampen vibrations in the cryogenic device by generating counteracting forces that counteract the vibrations. The damping system comprises one or more conductive structures, each conductive structure out of the one or more conductive structures having a first part that is positioned in the space and a second part that is positioned outside of the space. The first part comprises, preferably essentially consists of, superconductor material. Further, the damping system is configured to cause an electrical current in the first part when the damping system is generating the counteracting forces. In this aspect, the damping system may be any of the damping systems disclosed herein. Further, in this aspect, the further cryogenic device may comprise elements of any other cryogenic device disclosed herein, such as the compact system for reducing vibrations disclosed herein.

[0060] It should be appreciated that the construction with the mass being separated from the second element by means of one or more long elements can be beneficial irrespective of what kind of systems is used for reducing vibrations in the first place. Hence, a distinct aspect of this disclosure relates to a further system for reducing vibrations that comprises a subsystem for reducing vibrations in the z- direction. This subsystem is configured to prevent vibrations, in particular vertical vibrations, from travelling from a first element to a second element. As a side note, such subsystem may be any of the systems disclosed herein for reducing vibrations. In this aspect, the further system comprises a mass that is positioned at a distance from the second element by means of one or more elongated elements, such as pole-like elements. As before, in this further system, the second element, as viewed from a top view, has one or more outer edges and the second element is associated with a span distance, the span distance being equal to a largest distance, as viewed from a top view, that can be identified between any two points on any of the outer edges.

[0061] Preferably, this further system comprises a spring system, preferably a GAS system, (not necessarily having the new configuration disclosed herein) configured to prevent vertical vibrations from travelling from the first element to the second element. This further system may comprise any element of any other system for reducing vibrations as disclosed herein.

[0062] It should be appreciated that providing a current having a constant direct current component to a coil in a cryogenic device in order to compensate for changed spring properties of springs of spring systems, preferably geometric anti-spring systems, at very low temperatures is beneficial irrespective of the type of the spring systems that are implemented and irrespective of whether a damping system is present in the cryogenic device. Hence, a distinct aspect of this disclosure relates to a third cryogenic device, such as a dilution refrigerator. This third cryogenic device is configured to cool down a space within the cryogenic device to below 80K. This space comprises one or more spring systems that are configured to prevent vertical vibrations from travelling from a first element to a second element. Each spring system comprises a plurality of compressed springs. Preferably, each spring out of the plurality of compressed springs comprises a first end and a second end, the first end being connected to the first element and the second end being connected to the second element. The spring systems may comprise any of the spring system disclosed herein, but this is not per se required. This third cryogenic device comprises one or more conductive structures, such as one or more wires, wherein each conductive structure out of the one or more conductive structures has a first part that is positioned in the space and a second part that is positioned outside of the space, wherein the first part comprises, preferably essentially consists of, superconductor material. In at least one of the conductive structures the first part is embodied as a coil. This third cryogenic device also comprises a current control system that is configured to provide a current to the coil, wherein the current has a constant direct current component so that a predetermined load is applied to the compressed springs of the one or more spring systems.

[0063] Preferably, the coil is fixed to the first or second element and a magnet is fixed to the second or, respectively, first element. The coil receiving a constant direct current component means that a constant magnetic field component is continuously generated by the coil that interacts with the magnet. As such, the effective weight of the first and / or second element can be tuned. As explained, this is beneficial if the spring properties have changed due to the very low temperatures.

[0064] A distinct aspect of this disclosure relates to a method involving this third cryogenic device. In this aspect, the method comprises providing a current to the coil, the current having a constant direct current component so that a predetermined load is applied continuously to the compressed springs of the one or more spring systems, which are preferably geometric anti-spring systems.

[0065] Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise. Embodiments of the present invention will be further illustrated with reference to the attached drawings, which schematically will show embodiments according to the invention. It will be understood that the present invention is not in any way restricted to these specific embodiments.

[0066] BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Aspects of the invention will be explained in greater detail by reference to exemplary embodiments shown in the drawings, in which:

[0068] FIG. 1 illustrates a system for reducing vibrations according to an embodiment;

[0069] FIG. 2 is a top view of the system shown in figure 1 ;

[0070] FIG. 3 is a side view of the system shown in figure 1 ;

[0071] FIG. 4 illustrates an embodiment of the system that comprises damping systems;

[0072] FIG. 5 illustrates a cryogenic device according to an embodiment;

[0073] FIG. 6 illustrates more a damping system according to an embodiment in more detail;

[0074] FIG. 7 schematically shows a side view cross section of the damping system shown in figure 6; FIG. 8 illustrates the parts of the damping system of figure 7 that are fixed to the first element;

[0075] FIG. 9 illustrates the parts of the damping system of figure 7 that are fixed to the second element;

[0076] FIG. 10 shows in more detail the parts of the damping system that are fixed to the second element, according to an embodiment;

[0077] FIG. 11 shows an embodiment comprising a mass supported by elongated elements.

[0078] DETAILED DESCRIPTION OF THE DRAWINGS

[0079] In the figures, identical reference numbers indicate identical or similar elements. Figures 1 , 2, 3 illustrate a system 2 for reducing vibrations according to an embodiment. Figure 2 shows a top view of this system and figure 3 a side view. The system 2 comprises a first element 4 and a second element 6. In the depicted embodiment, the first element is a first horizontally oriented plate 4 and the second element is also a horizontally oriented plate 6. Further, in the depicted embodiment, the first plate 4 and second plate 6 are arranged one below the other. As viewed from a top view in a vertical direction (see figure 2), at least part of the first or second element sits in front of the second or, respectively, first element.

[0080] The first element 4 comprises one or more first apertures 8. These first apertures 8 are more clearly visible in figure 4 and are indicated therein as 8a, 8b, 8c, respectively. The second element 6 comprises one or more “second” protrusions 10. Visible in figure 1 are second protrusions 10a, 10b, 10c, 10d, 10e and 10f. The protrusions 10 at least partially extend through the one or more first apertures 8. This can be clearly seen in figure 3, which shows a side view of protrusions 10a and 10b extending through the first plate 4.

[0081] Figure 1 also indicates a mechanism 9 that can be used to set the distance between protrusion 10a and protrusion 10b. The mechanism 9 comprises a nut-like structure in the middle that accommodates a left thread bolt that extends to and is fixed to protrusion 10a (or 10b) and that accommodates a right thread bolt that extend to and is fixed to protrusion 10b (or 10a), respectively. By turning the nut-like structure in a certain direction, the protrusions 10a and 10b either move over the same distance towards the nut-like structure or move over the same distance away from the nutlike structure, because both bolts are either moving into the nut-like structure or, respectively moving out of the nut-like structure. This mechanism 9 can be used to pre-tension the springs 14 as desired. During pre-tensioning the springs, the protrusions 10 themselves can move relative to the second plate, in particular through a slot in the second plate. After the springs have been pre-tensioned, the protrusions 10 can be secured to the second plate so that they can no longer move relative to the second plate, for example using nuts and bolts. Preferably, each geometric anti-spring system comprises such a mechanism 9 for pre-tensioning the springs.

[0082] The depicted embodiment comprises three geometric anti-spring systems 12a, 12b, 12c (see figure 1) configured to prevent vibrations, in particular vertical vibrations, from travelling from the first element 4 to the second element 6. Each geometric anti-spring system 12 comprises four compressed springs 14. To illustrate, geometric anti-spring system 12c comprises compressed springs 14i, 14j, 14k, 141. The compressed springs of geometric anti-spring systems 12a and 12b are indicated in figure 2 as 14a - 14h.

[0083] In the depicted embodiment, of each geometric anti-spring system 12a, 12b, 12c each spring 14 is embodied as a pre-bent blade 14, in particular one that exerts a force on the second element 6 in either a first horizontal direction or second horizontal direction. To illustrate, (see figure 2) springs 14a and 14d of spring system 12a, exert a force on the second element 6 in a direction indicated by arrow 18, whereas springs 14b and 14c exert a force on the second element 6 in a direction indicated by arrow 20. Further, of spring system 12b, springs 14e and 14h exert a force on the second element 6 in a direction indicated by arrow 22, whereas springs 14f and 14g exert a force on the second element 6 in a direction indicated by arrow 24. Further, of spring system 12c, springs 14i and 141 exert a force on the second element 6 in a direction indicated by arrow 26, whereas springs 14 j and 14k exert a force on the second element 6 in a direction indicated by arrow 28. Thus, in the depicted embodiment, the springs belonging to one geometric anti-spring system exert forces, as viewed from a top view, along either one of two opposite directions.

[0084] The springs 14 may comprises steel and / or iron-containing alloys and / or titanium and / or titanium alloys and / or phosphorous bronze and / or molybdenum and / or beryllium copper and / or gold plated version of these materials.

[0085] As can be clearly seen in figure 2, each spring 14 comprises a first end A and a second end B. The first end A is connected to the first element 4 and the second end B is connected to the second element 6. Figure 3 clearly shows for springs 14c and 14d how their first ends, A_14c and A_14d respectively, are connected to the first element 4, in particular to protrusions 16a and 16b of the first element 4, and how their second ends, B_14c and B_14d respectively, are connected to the second element 6, in particular to second protrusions 10a and 10b thereof.

[0086] As can be clearly seen in figure 2, a distance d1 between the first end A and second B of for example spring 14d, is larger than distance d2 between first end A of spring 14d and second end B of spring 14c. Likewise, the distance d1 between the first end A and second B of for example spring 14d, is larger than distance d3 between first end A of spring 14d and second end B of spring 14b.

[0087] Likewise, the distance between the first end A and second end B of for example spring 14c, is larger than the distance between first end A of spring 14c and second end B of spring 14d. Likewise, the distance between the first end A and second end B of for example spring 14c, is larger than the distance between first end A of spring 14c and second end B of spring 14a.

[0088] Likewise, the distance between the first end A and second end B of for example spring 14b, is largerthan the distance between first end A of spring 14b and second end B of spring 14d. Likewise, the distance between the first end A and second end B of for example spring 14b, is larger than the distance between first end A of spring 14b and second end B of spring 14a.

[0089] Likewise, the distance between the first end A and second end B of for example spring 14a, is largerthan the distance between first end A of spring 14a and second end B of spring 14b. Likewise, the distance between the first end A and second end B of fer example spring 14a, is larger than the distance between first end A of spring 14a and second end B of spring 14c.

[0090] Such configurations allows for a very compact design of the GAS systems. This is very advantageous if there is little room for such a system, as is the case with optical tables and / or in cryogenic devices, for example.

[0091] The system 2 for reducing vibrations works very well for preventing vibrations from travelling from the first element 4 to the second element 6. Devices that are to be kept vibration free can subsequently be mechanically connected to the second element 6. For example, a further plate may be suspended through strings from the second element and further devices may be placed on this further plate. Additionally or alternatively, a device may be simply placed on the second element 6.

[0092] It should be appreciated that multiple systems 2 for reducing vibrations can be mechanically connected to each other. To illustrate, the first plate 4 from one system 2 for reducing vibrations can be suspended from a second plate 6 of another system 2 for reducing vibrations. Effectively, herewith multiple vibration filters are placed one after the other, wherein the effect of each filter multiplies with the previous one.

[0093] Figure 4 shows that the first element 4 may be supported by support elements 30a, 30b, 30c, 30d. Theses support elements may be inverted pendulums. In particular, the inverted pendulums may be supported by a third element in which case the inverted pendulums may be understood to prevent vibrations, in particular horizontal vibrations, from travelling from the third element to the first element.

[0094] The system 2 optionally comprises one or more damping systems. The system 2 depicted in figure 4 comprises three damping systems 32a, 32b, 32c. Each damping system 32 is configured to dampen vibrations of the second element 6 by generating counteracting forces that act on the second element 6 and that counteract the vibrations of the second element 6 as will be explained in more detail below.

[0095] These damping systems 32 are preferably implemented in a cold environment, such as in a cryostat. Their functioning may namely improve if some materials of the damping system are superconductive, which requires low temperatures. Hence, preferably, the damping system is used in a cryogenic device.

[0096] Figure 5 schematically illustrates a cryogenic device 33 according to an embodiment. Such cryogenic device 33 may or may not be a dilution refrigerator. In this embodiment, the cryogenic device 33 comprises a first system 2a for reducing vibrations as disclosed herein and a second system 2b for reducing vibrations disclosed herein. The cryogenic device 33 may be any cryogenic device known in the art. The depicted device 33 comprises a top flange 34, a 50K plate 36, a 4K plate 38, a still plate 40 and a mixing chamber plate 42.

[0097] The first element of system 2a is supported by inverted pendulums 48a and 48b known in the art, which are supported by the mixing chamber plate 42. System 2b, in particular the first plate thereof, is suspended from the system 2a by means of suspension lines 50a and 50b. A platform 44 for supporting an experiment 46 may then be suspended from system 2b, in particular from the second plate thereof through further suspension lines 52a and 52b. Additional cooling wires may then connect platform 44 with the mixing chamber plate (42).

[0098] Both systems 2a and 2b for reducing vibrations, and thus their geometric anti-spring systems, are positioned in spaces which the cryogenic device is configured to cool to below 50K. In fact, in the depicted embodiment, the systems 2a and 2b are in spaces which the cryogenic device is configured to cool to below 4K.

[0099] Figure 6 shows a damping system 32 according to an embodiment as may be implemented in a cryogenic device according to an embodiment. The damping system 32 comprises a conductive structure. A first part 54 of the conductive structure is positioned in the space that is cooled down to below 50K. In the depicted embodiment, the first part 54 of the conductive structure is embodied as a coil 54 that is made out of superconductor material. The coil 54 is also indicated in figure 7, which shows a schematic side view cross section of the damping system 32.

[0100] The conductive structure also has a second part (now shown) that is positioned outside of the space that is cooled down to below 50K. This second part would typically be a wire that is connected to the coil 54 and that extends to outside of the cryogenic device. The second part may or may not comprise superconductor material. The second part may also be shielded by superconducting tubing. The second part may be embodied as a copper wire that is connected to the coil 54.

[0101] The depicted damping system 32 can operate in two respective modes, namely a passive mode and an active mode. In passive mode, the damping system causes an electrical current in the coil 54 when the damping system 32 is generating the counteracting forces.

[0102] In the embodiment of figure 6, the damping system 32 comprises a magnet 56, which is preferably a permanent magnet. Further, in this embodiment, the magnet 56 is fixed to the second element 6, meaning that it moves along with the second element 6. The magnet, in particular is northpole N and south-pole S, are more clearly visible in figure 7 and in figure 9. Figure 9 only shows the parts of the damping system 32 that are fixed to the second element 6.

[0103] The first part 54 of the conductive structure is fixed to the first element 4, which can be seen more clearly in figure 7 and in figure 8. Figure 8 only shows the parts of the damping system 32 that are fixed to the first element 4. The magnetic field lines, two magnetic field lines are respectively indicated by the respective arrows in respective figures 6 and 7, travel from the north-pole to the south-pole via electrical steel elements 58 and 59. The coil 54 is positioned relative to the magnet 56 such that movement of the magnet 56 relative to the coil 54 causes a current in the coil 54. When this current is dissipated at higher temperatures, it provides for a drag force on the magnet 56. As such, the damping element 32 causes a force on the second element 6 (and a reactive force on the first element 4) that counteracts the first element’s and second element’s movement relative to each other. The currents advantageously do not dissipate in the coil 54, because the coil 54, when the cryogenic is in use, is superconductive. Any heat dissipation in the coil 54 would generate heat. This would be highly undesired if the damping system is implemented in a cryogenic device in a space that is to be cooled down to a very low temperature. The currents may flow to the second part of the conductive structure, e.g. to a wire, that is for example positioned at room temperature. The currents then dissipate at room temperature. The heat generated at the second part does not form a problem. In the passive mode of operation, the coil 54 is preferably short-circuited at room temperature.

[0104] In the active mode of operation, the damping system 32 makes use of a sensorthat is configured to detect vibrations of the second element 6, for example an accelerometer, a velocity or position detection element. In the depicted embodiment of figure 6, the sensor comprises a first coil 60, a second coil 62 and a third coil 64 (also indicated in figure 7). The first coil 60 and the second coil 62 are fixed to the first element 4 and the third coil 64 is fixed to the second element 6. By providing a signal, e.g. a sinusoidal signal having a frequency of for example 50 kHz, to the third coil 64, if the third coil 64 sits exactly halfway the first coil 60 and the second coil 62, the first coil 60 and second coil 62 should measure the same amount of flux change per unit of time. After all, the AC signal in coil 64 causes a changing magnetic field. Depending on whether the third coil sits at a higher or lower position, the induced voltage or current in coil 64 will change. As such, coils 60, 62, 64 allow to determine the relative position of the first 60 and second 62 coil relative to the third coil 64, and thus to determine the relative position of the first element 4 relative to the second element 6. Then, based on a known transfer function, which indicates how vibrations of the first element are transferred to the second element, it can be determined, given a vibration of the first element 4 relative to the second element 6 as measured by the sensor, whether, and optionally what kind of, active damping is required for keeping the second element 6 free of vibrations.

[0105] In the active mode, coil 54 is used for generating the counteracting forces. In this mode, the damping system comprises an electrical current control system. The electrical current control system is configured to cause an electrical current through the coil 54 in dependence of the detected vibrations of the second element 6 for causing the coil 54 to generate magnetic forces as the counteracting forces.

[0106] The electrical current control system may be configured to continuously provide a direct current to the coil so that, as described above, a predetermined load is applied continuously to the compressed springs of the one or more geometric anti-spring systems.

[0107] The current control system is typically positioned at room temperature. Again, advantageously, because the coil 54 is superconductive when the system is used, e.g. during an experiment, no current dissipates in the coil 54. However, the coil 54 is connected to a second part of the conductive structure, e.g. to a wire that connects the coil 54 to the current control system at room temperature. The heat dissipation then occurs elsewhere, preferably outside of the cryogenic device, where heat generation is not an issue.

[0108] The damping system of figure 6 also comprises a superconductor magnetic shield. In the depicted embodiments, the superconductor magnetic shield comprises superconductor shield elements 70, 72, 74 and 76. The superconductor magnetic shield, in particular its shield elements 70 and 72, surrounds the coil 54. The superconductor magnetic shield is configured to block a magnetic field caused by any electrical current in coil 54. In a preferred embodiment, the magnetic field is configured to shield magnetic fields from the one or more second parts of the respective one or more conductive structures as well. No or almost no elements that are both metallic and at the same time non-superconductive are present inside the shield.

[0109] Figure 7 shows a schematic side view cross section of the damping system 32 shown in figure 6.

[0110] Figure 8 illustrates the parts of the damping system 32 shown in figure 7 that are fixed to the first element 4.

[0111] Figure 9 illustrates the parts of the damping system 32 shown in figure 7 that are fixed to the second element 6.

[0112] Figure 10 show a detailed projection of the part of the damping system 32 that is fixed to the second element 6.

[0113] Figure 11 illustrates an embodiment of the system comprising a mass 78 that is positioned at a distance L from the second element 6 by means of three elongated elements 80a, 80b, 80c.

[0114] As viewed from a top view, the second element 6 has outer edges. The span distance SD is defined as the largest distance that can be identified between any two points on any of the outer edges. The distance L is preferably greater than half the span distance. In the depicted embodiment, the distance L is greater than greater than the span distance SD.

[0115] As a side note, the second element 6 is positioned above the first element 4 in this embodiment.

Claims

CLAIMS1 . A system for reducing vibrations, the system comprising a first element and a second element; and one or more spring systems, preferably one or more geometric anti-spring systems, configured to prevent vibrations, in particular vertical vibrations, from travelling from the first element to the second element, wherein each spring system of the one or more spring systems comprises a plurality of compressed springs, wherein each spring out of the plurality of compressed springs comprises a first end and a second end, the first end being connected to the first element and the second end being connected to the second element, wherein the plurality of compressed springs comprises a first spring and a second spring, wherein a distance between the first end of the first spring and the second end of the first spring is equal to or larger than a distance between the first end of the first spring and the second end of the second spring.

2. The system according to claim 1 , wherein the distance between the first end of the first spring and the second end of the first spring is at least twice, preferably at least three times, more preferably at least five times, the distance between the first end of the first spring and the second end of the second spring.

3. The system according to claim 1 or 2, wherein of at least one spring system, preferably of each spring system, each spring out of the plurality of compressed springs exerts a respective force on the second element in a first horizontal direction or in a second horizontal direction that is opposite the first horizontal direction.

4. The system according to any of the preceding claims, wherein one or more springs out of the plurality of compressed springs, preferably each spring out of the plurality of compressed springs, comprises steel and / or iron-containing alloys and / or titanium and / or titanium alloys and / or phosphorous bronze and / or molybdenum and / or beryllium copper and / or gold plated version of these materials.

5. The system according to any of the preceding claims, wherein one or more springs out of the plurality of compressed springs, preferably each spring out of the plurality of compressed springs, is a pre-bent blade.

6. The system according to any of the preceding claims, wherein the one or more spring systems comprises at least two spring systems.

7. The system according to any of the preceding claims, wherein the first element is a first horizontally oriented plate and / or the second element is a second horizontally oriented plate, wherein the first element and second element are arranged one below the other.

8. The system according to any of the preceding claims, wherein the first element comprises one or more first apertures and the second element comprises one or more second protrusions at least partially extending through the one or more first apertures, wherein one or more second ends of one or more respective springs of one or more spring systems are connected to the one or more second protrusions, and / or wherein the second element comprises one or more second apertures and the first element comprises one or more first protrusions at least partially extending through the one or more second apertures, wherein one or more first ends of one or more respective springs of one or more spring systems are connected to the one or more first protrusions.

9. The system according to any of the preceding claims, further comprising one or more inverted pendulums for reducing horizontal vibrations.

10. The system according to any of the preceding claims, wherein the second element, as viewed from a top view, has one or more outer edges, and wherein the second element is associated with a span distance, the span distance being equal to a largest distance, as viewed from a top view, that can be identified between any two points on any of the outer edges, the system comprising a mass that is positioned at a distance from the second element by means of one or more elongated elements, such as pole-like elements, the distance being greater than half the span distance, preferably greater than the span distance.11 . A cryogenic device, preferably a dilution refrigerator, comprising the system for reducing vibrations according to any of the preceding claims, wherein the cryogenic device is configured to cool down a space within the cryogenic device to below 80K, wherein the one or more spring systems are positioned in said space.

12. The cryogenic device according to claim 11 , further comprising a cryocooler.

13. The cryogenic device according to claim 11 or 12, wherein the system for reducing vibrations further comprises a damping system that is configured to dampen vibrations of the second element by generating counteracting forces that act on the second element and that counteract the vibrations of the second element, whereinthe damping system comprises one or more conductive structures, such as one or more wires, wherein each conductive structure out of the one or more conductive structures has a first part that is positioned in the space and a second part that is positioned outside of the space, wherein the first part comprises, preferably essentially consists of, superconductor material, wherein the damping system is configured to cause an electrical current in the first part when the damping system is generating the counteracting forces.

14. The cryogenic device according to claim 13, wherein the damping system comprises a superconductor magnetic shield at least partially surrounding, preferably completely surrounding, the first part of at least one conductive structure out of the one or more conductive structures, the superconductor magnetic shield being configured to block a magnetic field caused by the electrical current in the first part of the conductive structure.

15. The cryogenic device according to claim 13 or 14, wherein the damping system comprises a sensorthat is configured to detect vibration of the second element, wherein the one or more conductive structures comprise a first conductive structure, wherein the first part of the first conductive structure comprises a coil, wherein the damping system comprises an electrical current control system that is configured to cause an electrical current through the coil in dependence of the detected vibrations of the second element for causing the coil to generate magnetic forces as the counteracting forces.

16. The cryogenic device according to the preceding claim, wherein the electrical current control system is configured to provide a current to the coil, the current having a constant direct current component so that a predetermined load is applied continuously to the compressed springs of the one or more spring systems.

17. The cryogenic device according to any of the claims 12-16, wherein the one or more conductive structures comprise a second conductive structure, wherein the damping system comprises a magnet that is fixed to the first or second element, wherein the first part of the second conductive structure is fixed to the second or, respectively, first element, wherein the first part of the second conductive structure and the magnet are positioned relative to each other such that movement of the magnet relative to the first part of the second conductive structure causes a current in the first part of the second conductive structure, which is dissipated outside of the space, causing a drag force on the magnet herewith causing the counteracting forces.

18. A method for controlling a current in a cryogenic device according to claim 15 or 16, the method comprising providing a current to the coil, the current having a constant direct current component so that a predetermined load is applied continuously to the compressed springs of the one or more spring systems.

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