Improvement of MAS-NMR

Abstract

A coil 1 for a probe head 2 of a magnetic resonance spectrometer comprising a rotor 3 is configured to transmit radio frequency signals for exciting a sample received in the rotor 3 and / or configured to receive radio frequency signals emitted by the sample. The coil 1 comprises a number of turns 4, 4a, ... arranged along a coil axis C extending along the coil 1 and defining an elliptical shape, preferably a spherical shape. A probe head 2 for a probe of a magnetic resonance spectrometer comprises the rotor 3, a rotation device 9 configured to cause a rotation of the rotor 3, and the coil 1. The rotation device 9 comprises a fluid supply device 6 and / or a fluid directing device 10. The fluid supply device 6 comprises a number of fluid openings 7, 7a, ... arranged in a common plane P. The fluid directing device 10 comprises or consists of the coil 1.

Description

[Technical field]

[0001] The present invention relates to a coil for a probehead of a magnetic resonance spectrometer and to a probehead for a probe of a magnetic resonance spectrometer. [Background technology]

[0002] Magic angle spinning [1-3] (MAS) is necessary in solid-state nuclear magnetic resonance (NMR) to obtain high-resolution spectra that characterize the local chemical environment of biomolecules and inorganic solids [4-17]. Conventional MAS uses a cylindrical sample vessel that rotates around an axis tilted at the magic angle, which is 54.74° relative to the external magnetic field. A solenoid coil is tightly wound around the cylindrical rotor for optimal NMR sensitivity. However, to set the magic angle, the rotor, coil, and stator must be oriented along the magic angle, resulting in only 80% of the radio frequency (RF) power being used. The stator assembly consists of about 12 precisely machined components that house the rotor and provide the bearings and driving gas flow, requiring a large probe headspace. Rotor wobble during spinning at high frequencies can cause rotor collisions and stator damage.

[0003] In 2018, a new platform for MAS NMR was shown, in which a spherical rotor is rotated in a hemispherical stator cup and a single gas flow is used for both bearing and drive

[18] . Spherical rotors exhibit very good rotational stability and resistance to collisions due to their symmetry axis being aligned with their highest axis of inertia

[19] . The spherical geometry of the rotor and the single gas flow relax the space requirements for the probe head. Higher spin frequencies and RF fields have been achieved using smaller rotors [20, 21]. However, MAS spheres have one major drawback: a much lower NMR filling factor compared to cylindrical rotors. This is due to the smaller sample volume in the sphere and the larger gap between the RF coil and the rotor. Efforts have been made to improve the NMR filling factor. The four-turn split coil has been replaced by a double saddle coil tightly wound around the stator cup [19-22]. The cylindrical sample chamber has been expanded to hold more sample

[18] . A new stator design, replacing the stator cup walls with saddle coils, further increases NMR sensitivity by a factor of three

[21] .

[0004] However, while the high precision requirements associated with component manufacturing are relaxed, there remains a general need to further improve the sensitivity in MAS NMR experiments. Summary of the Invention

[0005] It is an object of the present invention to provide a coil for a probe head and a probe head for a magnetic resonance spectrometer that improve the sensitivity of NMR experiments.

[0006] This object is achieved by a coil according to claim 1 and a probe head according to claims 4 and 7, respectively.

[0007] Thus, in a first aspect, a coil for a probe head of a magnetic resonance spectrometer is provided, the coil being configured to transmit at least one radio frequency signal to excite a sample received in the rotor. Additionally or alternatively, the coil is configured to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by the radio frequency signal. That is, the coil preferably corresponds to a radio frequency coil, such as a transmit / receive coil capable of transmitting and receiving radio frequency signals. The coil comprises a number of turns arranged along a coil axis extending along the coil. The number of turns of the coil defines an ellipsoid shape, preferably a sphere.

[0008] The expression "defining an elliptical shape" is understood as the turns of the coil being arranged along the coil axis such that an imaginary surface enclosing the turns has the shape of an ellipse.

[0009] The turns of the coil can be designed and / or arranged to form different elliptical shapes, for example, the turns can be designed and / or arranged to form an elliptical shape in the form of a sphere or a spheroid such as an oblate or prolate spheroid.

[0010] For this purpose, it is particularly preferred that the elliptical shape has the shape of a sphere, in other words, it is particularly preferred that the turns of the coil define a sphere, in other words, it is particularly preferred that the coil is a spherical coil.

[0011] That is, the shape of the coil does not correspond to a cylindrical shape as is the case with linear solenoid coils for cylindrical rotors known in the current art.

[0012] The ellipsoidal coil allows the coil axis to be aligned perpendicular to the direction of the external magnetic field of the NMR spectrometer, regardless of the axis of rotation of the rotor. Thus, if we define the direction of the external magnetic field as the z-axis, all of the magnetic field B1 generated by the radio frequency pulses is generated along the x,y plane spanned by the x- and y-axes extending perpendicular to the z-axis. In this way, NMR experiments such as dynamic-angle spinning (DAS) and variable-angle spinning can be performed without compromising the B1 field, thereby significantly improving sensitivity.

[0013] Throughout this application, the terms spin and spin are used interchangeably, e.g., a spinning rotor corresponds to a spinning rotor and vice versa.

[0014] The circumference of the individual turns of the coil with respect to the circumferential direction of the turns is preferably elliptical, particularly preferably circular, i.e. the individual turns preferably have an elliptical, particularly preferably circular, shape when the coil is viewed in cross section, i.e. as a planar cross section at an angle of 90° to the coil axis.

[0015] Furthermore, the circumference of the individual turns with respect to the circumferential direction of the turns preferably varies with respect to the coil axis, i.e. the turns preferably extend different distances from the coil axis, or in other words different sized turns, such as smaller turns and larger turns, are preferred.

[0016] With respect to the extension direction extending from the start of the coil provided by the first turn of the coil to the end of the coil provided by the last turn of the coil, the circumference of the turns preferably becomes gradually larger and then gradually smaller, i.e. the circumference of the turns in the region of the start of the coil and the circumference of the turns in the region of the end of the coil are preferably smaller than the circumference of the turns in the intermediate region of the coil, i.e. particularly preferably the circumference of one or more turns in the intermediate region is maximum.

[0017] A preferred extension of the coil along an axis extending through a center of the coil and along the coil axis is preferably between 1 millimeter and 20 millimeters, more preferably between 5 millimeters and 15 millimeters.

[0018] A preferred extension of the coil along an axis extending through the center of the coil and perpendicularly to the coil axis is preferably between 1 millimeter and 20 millimeters, more preferably between 5 millimeters and 15 millimeters.

[0019] When the coil has a spherical shape, the extension can be regarded as the diameter of the coil, i.e., the coil diameter of the coil is preferably 1 mm to 20 mm, more preferably 5 mm to 15 mm.

[0020] That is, various coil extensions or coil diameters are contemplated, with the coil extension (diameter) preferably depending on the size of the rotor. In practice, the coil extension (diameter) is preferably larger than the rotor diameter of the rotor. The coil extension (diameter) is particularly preferably 0.001 mm to 15 mm, more preferably 0.001 mm to 4 mm, larger than the rotor diameter.

[0021] The distance between successive turns of the coil may remain constant with respect to the coil axis or may vary, in the latter case, by way of example, the distance between successive turns of the coil is preferably smaller in the central region of the coil, i.e. preferably there is a greater number of turns in the middle region of the coil and preferably there are fewer turns in the outer regions of the coil, i.e. at the beginning and end of the coil.

[0022] Various numbers of turns are contemplated, with the number of turns preferably depending on the size of the rotor, with the preferred number of turns being between 2 turns and 10 turns.

[0023] Furthermore, in case of coils with turns of different sizes, the coil diameter is preferably defined by the maximum turn, i.e. the coil diameter preferably corresponds to the diameter of the maximum turn of the coil.

[0024] In addition, the coil, and in particular its turns, are preferably formed by a wire. The wire diameter of the wire may remain constant or may vary with respect to the coil axis. The wire diameter of the wire is preferably between 0.0001 mm and 2 mm. Furthermore, various distances between successive turns with respect to the coil axis are contemplated. For example, a preferred distance between successive turns with respect to the coil axis is between 0.0001 mm and 5 mm.

[0025] Furthermore, as will be explained in more detail below, it is further preferred that the rotor is at least partially, preferably entirely, received within the coil. In other words, the coil is preferably at least partially, preferably entirely, wrapped around the rotor. The shape of the rotor preferably corresponds to the shape of the coil, i.e., the shape of the rotor is preferably elliptical, particularly preferably spherical. It is also preferred that the rotor is rotatable relative to the coil. In other words, the rotor can rotate or spin within the coil. The main advantage of receiving an ellipsoidal rotor within an ellipsoidal coil is that the NMR filling factor and therefore the sensitivity in NMR experiments is significantly improved.

[0026] In another aspect, a probe head for a magnetic resonance spectrometer probe is provided. The probe head comprises a rotor configured to rotate about a rotation axis, at least one rotation device configured to rotate the rotor about the rotation axis, and at least one coil. The rotation device comprises at least one fluid supply device configured to supply a fluid to the rotor. The coil is configured to transmit at least one radio frequency signal to excite a sample received in the rotor. Additionally or alternatively, the coil is configured to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by the radio frequency signal. The rotation device further comprises at least one fluid directing device configured and / or arranged to direct a fluid supplied by the fluid supplying device to the rotor, the fluid directing device comprising or consisting of a coil.

[0027] The coils may correspond to those described above, however it should be noted that various types of coils as known in the art may be used as well, for example the coils may be saddle coils, Helmholtz coils etc.

[0028] In both cases, the probe head comprises a rotating device comprising a coil. In other words, the coil is part of the stator, which is understood as the mechanism that provides and influences the flow of the fluid used to rotate the rotor. Current solutions for rotating the rotor require a stator placed between the coil and the rotor containing the sample. These devices have drawbacks such as i) requiring precise design and manufacturing of the stator cups and fluid channels that provide fluid for stable spinning, ii) limiting the use of inductors such as solenoid coils due to the geometry of the stator, iii) not performing well in cryogenic environments, and iv) not being durable due to damage caused by the rotating rotor to the softer stator cups. Inaccurate design and manufacturing, damage, and poor operation in cryogenic environments adversely affect the sensitivity of NMR experiments. In addition, the high precision requirements for manufacturing are associated with high costs. These drawbacks are overcome by the probe head of the present invention, where the ability of the rotor to rotate or spin within the coil relaxes the high precision requirements and makes stator development for smaller rotors easier, again significantly improving the NMR filling factor and therefore the sensitivity.

[0029] The fluid directing device is particularly preferably constructed and / or arranged to generate a bearing force and / or a driving force which causes the rotor to rotate about the axis of rotation.

[0030] The bearing and driving forces are preferably generated by a fluid flowing through a gap between the rotor and the coil, as will be explained in more detail below, and in this regard it is noted that the initial speed of the rotor is preferably obtained from a fluid supply device.

[0031] As will be explained in more detail below, the fluid supply device preferably comprises at least one fluid opening for supplying fluid to the rotor. However, it is also contemplated that the fluid supply device comprises two or more, in particular a plurality of, fluid openings for supplying fluid to the rotor. Furthermore, the two or more fluid openings are preferably arranged to rotate the rotor about the rotation axis. Additionally or alternatively, the two or more fluid openings are preferably arranged in at least one or one common plane.

[0032] In another aspect, a probehead for a magnetic resonance spectrometer is provided, the probehead comprising a rotor configured to rotate about an axis of rotation, at least one rotation device configured to rotate the rotor about the axis of rotation, and at least one coil. The coil is configured to transmit at least one radio frequency signal to excite a sample received in the rotor. Additionally or alternatively, the coil is configured to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by the radio frequency signal. The rotation device comprises at least one fluid supply device configured to supply a fluid to the rotor. The fluid supply device comprises a plurality of fluid openings for supplying a fluid to the rotor. The plurality of fluid openings are arranged to rotate the rotor about the axis of rotation. Additionally or alternatively, the plurality of fluid openings are arranged in at least one or a common plane.

[0033] The one or more common planes in which the fluid openings are disposed preferably extend perpendicular to the axis of rotation of the rotor.

[0034] Providing multiple fluid openings in at least one or exactly one common plane results in an overall fluid flow that provides improved, in particular higher, driving forces at the surface of the rotor, which results in higher spin or rotation frequencies of the rotor about the axis of rotation during magic angle spinning, thereby improving NMR sensitivity.

[0035] In particular, the fluid openings are preferably arranged and / or configured such that the fluid flow is split into fluid streams, one fluid stream per fluid opening, and further, the fluid openings are arranged and / or configured such that the individual fluid streams partially cancel each other out while summing the driving forces, providing a balance control between the bearing forces and the driving forces.

[0036] Also in this case, the probe head is preferably equipped with a coil corresponding to the coil described above, although it should be noted that various types of coils as known in the state of the art may be used as well.

[0037] The following description applies equally to both of the above probe heads. Indeed, inter alia, a probe head comprising a rotation device comprising a fluid directing device comprising or consisting of a coil preferably comprises a fluid supply device comprising a plurality of fluid openings arranged in a common plane, and vice versa. Thus, any description made herein with respect to one of the probe heads applies equally to the other probe head. In particular, it is noted that all aspects described herein may be present in a single probe head. For simplicity, reference will be made below to a probe head.

[0038] The coil surrounds the rotor at least partially, particularly preferably entirely. That is, as mentioned above, the rotor is preferably received at least partially, preferably entirely, within the coil. In other words, the coil is preferably wound at least partially, preferably entirely around the rotor. Furthermore, the rotor is preferably rotatably received within the coil and / or rotatable relative to the coil.

[0039] The gap between the coil and the rotor is preferably 4 millimeters or less. Additionally or alternatively, the gap between the coil and the rotor is preferably 50 micrometers to 4 millimeters, more preferably 100 micrometers to 2 millimeters, particularly preferably about 500 micrometers. The gap can be understood as the distance formed between the inner surface of the turn of the coil facing the outside of the rotor and the outside of the rotor, with respect to a direction extending perpendicular to the coil axis. The coil is thus tightly wound around the rotor, minimizing the distance between the sample accommodated in the rotor and the coil. Thereby, the NMR filling factor and therefore the sensitivity of the NMR experiment is further improved.

[0040] The shape of the rotor preferably corresponds to the shape of the coil. Additionally or alternatively, the rotor preferably comprises a sample chamber configured to receive a sample, and the shape of the coil preferably corresponds to the shape of the sample chamber. Thus, the rotor preferably has an elliptical shape, particularly preferably a spherical shape. Furthermore, the sample chamber preferably has an elliptical shape, particularly preferably a spherical shape. By providing an elliptical sample chamber, the sample volume is increased, which again significantly improves the NMR filling factor.

[0041] The fluid delivery device preferably comprises a receptacle and the coil is at least partially, preferably entirely, disposed within the receptacle.

[0042] In other words, the fluid supply device is preferably arranged outside the coil. Additionally or alternatively, the coil is preferably arranged at least partially, particularly preferably entirely, within the fluid supply device.

[0043] The receptacle particularly preferably corresponds to a through hole extending through the fluid supply device, in other words the coil is preferably not received in a stator cup or the like.

[0044] To ensure a stable spin of the rotor, it is further preferred that the coil is positioned in a central area of ​​the fluid supply device, which preferably corresponds to the geometric centre of the fluid flow or the geometric centre of the fluid opening, respectively. The geometric centres of the fluid flow or the fluid opening are preferably located in a common plane in which the fluid openings are located (see above). In this way, a balanced fluid pressure can be applied to the rotor.

[0045] Since the coil preferably at least partially surrounds the rotor, it is further preferred that the rotor is at least partially, preferably entirely, received within the fluid delivery device, in particular also within a receptacle of the fluid delivery device, and thus the rotor is preferably located within the coil, and the coil is preferably located within the fluid delivery device.

[0046] The fluid opening or openings, in particular the fluid openings, are preferably arranged in the area of ​​the receptacle. In practice, the fluid opening(s) are preferably arranged to face towards the receptacle, in particular preferably towards the receptacle and thus towards the coil and rotor arranged in the receptacle. Various designs of the fluid openings are contemplated. For example, the fluid openings can be arranged flush with the surface of the fluid supply device that defines the receptacle. Alternatively, the fluid openings may protrude from the surface of the fluid supply device that defines the receptacle.

[0047] Furthermore, the fluid openings may be disposed at an angle relative to a surface of the fluid delivery device that defines the receptacle and / or relative to the outer surface of the rotor, and to this end, the opening direction of the fluid openings is preferably tangential to the outer surface of the rotor.

[0048] The plurality of fluid openings are preferably arranged at least partially, and particularly preferably entirely, around the circumference of the receptacle. Additionally or alternatively, the plurality of fluid openings are preferably arranged at least partially, and particularly preferably entirely, around the circumference of the coil. For example, in the case of a spherical coil, the plurality of fluid openings are preferably arranged equatorially around the coil.

[0049] The arrangement of the fluid openings preferably corresponds to the shape of the rotor and / or the shape of the coil when viewed in cross section, for example in the case of a spherical coil having a spherical cross section, the cross section of the receptacle of the fluid delivery device preferably has a circular shape and the arrangement of the fluid openings is also preferably circular.

[0050] Preferably, the circumferential direction of the receptacle and / or the circumferential direction of the coil extends around an axis extending perpendicular to the coil axis. However, it should be noted that other arrangements are also contemplated. In particular, as mentioned further below, the coil axis can be in any direction on a plane that is perpendicular to the direction of the static magnetic field of the magnetic resonance spectrometer when the probe head is received in the magnetic resonance spectrometer, i.e., an x,y plane extending perpendicular to the z-axis when the z-axis is defined as the direction of the external magnetic field, as is common in the field of NMR.

[0051] The fluid supply device is preferably configured to adjust the rotation axis of the rotor relative to an adjustment axis of the probe head. Additionally or alternatively, the fluid supply device is preferably configured to adjust the rotation axis of the rotor relative to the direction of a static magnetic field of the magnetic resonance spectrometer when the probe head is received in the magnetic resonance spectrometer.

[0052] That is, the fluid supply device can be considered as an adjustment device configured to adjust the rotation axis of the rotor relative to the adjustment axis of the probe head or relative to the direction of the static magnetic field. The adjustment axis of the probe head preferably extends parallel to the direction of the static magnetic field of the magnetic resonance spectrometer when the probe head is received in the magnetic resonance spectrometer. The fluid supply device can therefore be used to find the so-called magic angle.

[0053] The coil is preferably configured to be stationary during adjustment by the fluid supply device relative to the probe head. Additionally or alternatively, the fluid supply device is preferably configured to be movable during adjustment relative to the probe head.

[0054] Preferably, the fluid delivery device non-mechanically adjusts the axis of rotation of the rotor.

[0055] In fact, it is preferred that there is no physical connection between the rotor and the fluid supply device. Instead, the rotational axis of the rotor is preferably perpendicular to one or more common planes in which the fluid openings are located, and a movement, such as a rotation, of the fluid supply device changes the flow direction of the fluid supplied by the fluid supply device, whereby the rotor is reoriented to rotate or spin on an axis perpendicular to the fluid supply device. In other words, it is preferred that no mechanical adjustment is established between the fluid supply device and the rotor, and that the fluid supply device is mechanically adjusted.

[0056] Furthermore, the fluid supply device is preferably arranged movably, in particular pivotably, in the probe head. It is particularly preferred that during adjustment by the fluid supply device, the orientation of the fluid supply device relative to the probe head is also adjusted, e.g. by rotating the fluid supply device, and thereby the rotation axis of the rotor is also adjusted.

[0057] In addition, it is preferred that the fluid directing device, particularly the coil, remains stationary during adjustment by the fluid supply device, e.g. the coil remains stationary while the fluid supply device is rotated to adjust the axis of rotation of the rotor. It is further preferred that the fluid directing device, particularly the coil, is arranged immovably, i.e. stationary, within the probe head.

[0058] As mentioned above, the coil preferably defines a coil axis. In the probehead, the coil axis preferably extends perpendicular to the adjustment axis A of the probehead. Additionally or alternatively, the coil axis preferably extends perpendicular to the direction of the static magnetic field B of the magnetic resonance spectrometer when the probehead is received in the magnetic resonance spectrometer. Additionally or alternatively, the coil axis preferably extends in a plane that extends perpendicular to the adjustment axis A of the probehead and / or perpendicular to the direction of the static magnetic field B of the magnetic resonance spectrometer when the probehead is received in the magnetic resonance spectrometer. The plane can be seen as an x,y plane spanned by the x and y axes extending perpendicular to the z axis, if the z axis is defined as the direction of the external magnetic field, as is common in the field of NMR.

[0059] As previously mentioned, all of the above aspects can be present within a single probe head, i.e. the preferred probe head comprises an ellipsoidal rotor surrounded by an ellipsoidal coil, the coil being part of or providing a fluid directing device for the rotational device, the rotational device further comprising a fluid supply device preferably comprising a plurality of fluid openings arranged in a common plane, the coil being surrounded by the fluid supply device.

[0060] Preferred embodiments of the invention are described below with reference to the drawings, which are intended to illustrate presently preferred embodiments of the invention and not to limit it. [Brief description of the drawings]

[0061] [Figure 1]FIG. 1 shows a perspective view of an NMR probehead comprising a rotation device and a rotor, the rotation device comprising a fluid supply device and a fluid directing device. [Diagram 2] FIG. 2 is a side view of the NMR probehead according to FIG. [Diagram 3] FIG. 3 is a front view of the fluid supply device and rotor of the NMR probehead according to FIG. [Figure 4] FIG. 4 is a side view of the fluid supply device and rotor of the NMR probehead according to FIG. [Figure 5a] FIG. 5a is a front view of a spherical coil being wrapped around a spherical rotor. [Figure 5b] FIG. 5b shows a high frequency finite element simulation of a spherical coil wrapped around a spherical rotor according to FIG. 5a. [Figure 6a] FIG. 6a is a front view of a cylindrical coil wound around a cylindrical rotor as known in the state of the art. [Figure 6b] FIG. 6b shows a high frequency finite element simulation of a cylindrical coil wound around a cylindrical rotor according to FIG. 6a. [Figure 7a] FIG. 7a shows a first embodiment of a rotor for an NMR probehead. [Figure 7b] FIG. 7b is a cross-sectional view of the rotor according to FIG. [Figure 8a] FIG. 8a shows a second embodiment of the rotor of the NMR probehead. [Figure 8b] FIG. 8b is a cross-sectional view of the rotor according to FIG. 8a. [Figure 9a] FIG. 9a shows a third embodiment of the rotor of the NMR probehead. [Figure 9b] FIG. 9b is a cross-sectional view of the rotor according to FIG. 9a. [Figure 10a] FIG. 10a shows the 79Br spectrum of KBr in the rotor of FIGS. 7a to 9b. [Figure 10b]FIG. 10b is a close-up of the central peak of FIG. 10a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] Various aspects of the invention will now be described in more detail with reference to the drawings.

[0063] 1-4 show an NMR probehead 2 according to the invention comprising a rotor 3 configured to rotate about a rotation axis R, a rotation device 9 configured to generate rotation of the rotor 3 about the rotation axis R, and a coil 1 configured to transmit radio frequency signals to excite a sample received in the rotor 3 and to receive radio frequency signals emitted by the sample in response to excitation of the sample by the radio frequency signal. The rotation device 9 comprises a fluid supply device 6 configured to supply a fluid to the rotor 3, and a fluid directing device 10 constructed and arranged to direct the fluid supplied by the fluid supply device 6 to the rotor 3.

[0064] Notably, in the illustrated example, the probe head 2 is designed for a 9.5 mm spherical rotor 3 on a customized small-bore transmission line probe

[21] , but can be retrofitted to any type of probe. Furthermore, as described in more detail below, the coil 1 in the illustrated probe head 2 corresponds to a spherical solenoid coil tightly wound around the spherical rotor 3. The spherical solenoid coil 1 functions as an RF coil and maintains the position of the rotor 3 at the center of the fluid delivery device 6 (see FIG. 1). Additionally, the illustrated probe head 2 includes a capacitor 11 that is used to tune and match the electrical circuitry of the entire probe. This ensures efficient transmission of the correct RF signal.

[0065] As mentioned above, the rotation device 9 comprises a fluid supply device 6 configured to supply a fluid to the rotor 3. As best seen in Figs. 3 and 4, the fluid supply device 6 comprises a receptacle 8 in the form of a through hole extending through the fluid supply device 6, and the coil 1 and the rotor 3 are arranged in said receptacle 8. That is to say, as can be easily seen from Figs. 1 to 4, the fluid supply device 6 is arranged outside the coil 1. Indeed, in the illustrated example, the fluid supply device 6 has the shape of a ring, in which the coil 1 and the rotor 3 are arranged. The fluid supply device 6 may therefore be referred to as a ring stator. In addition, in the illustrated example, a gas tube 12 made of rubber is used to deliver the fluid used to rotate the rotor 3 into the ring stator 6, while maintaining the rotational flexibility of the ring stator 6 for magic angle adjustment (see Figs. 1 and 2 and the additional explanation provided further below). The fluid corresponds to a gas that may be referred to as a spinning gas.

[0066] Furthermore, the fluid supply device 6 comprises a number of fluid openings 7, 7a, ... for supplying the fluid to the rotor 3, the fluid openings 7, 7a, ... being arranged in a common plane P. In particular, the fluid openings 7, 7a, ... are arranged and configured in such a way that the fluid flow is divided into fluid streams, i.e. here one fluid stream per fluid opening 7, 7a, ... corresponding to the six streams exiting from the six fluid openings 7, 7a, .... The fluid openings 7, 7a, ... are arranged in the area of ​​the receptacle 8. In fact, the fluid openings 7, 7a, ... are arranged in such a way that they face into the receptacle 8, towards the coil 1 and towards the rotor 3, which is arranged in the receptacle 8. Furthermore, in the illustrated example, the fluid openings 7, 7a, ... protrude from the surface 13 of the fluid supply device 6 that defines the receptacle 8. Moreover, the fluid openings 7, 7a, ... are arranged at an angle β with respect to the surface 13 of the fluid supply device 6 that defines the receptacle 8, and also at an angle γ with respect to the outer surface 14 of the rotor 3. Here, the fluid openings 7, 7a, ... are arranged at an angle γ of 22° with respect to the outer surface 14 of the rotor 3. In FIG. 3, the flow direction F of the spinning gas is indicated by an arrow. The division of the spinning gas into different gas flows by the ring stator 6 differs from the stator with hemispherical stator cups known in the current art [18-21] that provides a single gas flow. Both types of stators known from the prior art lack individual control of the bearing and driving forces, while the six gas flows flowing from the ring stator 6 towards the rotor 3 according to the invention can partially cancel each other and sum the driving forces, resulting in a balance control between the bearing and driving forces. In addition, the spinning of the spherical rotor 3 in the coil 1 according to the invention relaxes the requirement of high-precision 3D printing that was essential for previous stator designs with hemispherical cups. Once a stable spin is established, the spherical rotor 3 spins about a central axis Z perpendicular to the ring stator 6. The spin frequency of the spherical rotor 3 can be measured using optical fibers.

[0067] Furthermore, in the illustrated example, the fluid openings 7, 7a, ... of the fluid supply device are arranged generally along a circumferential direction CR of the receptacle 8 and generally along a circumferential direction CC of the coil 1. Said circumferential direction CR of the receptacle 8 and said circumferential direction CC of the coil 1 each run about an axis extending perpendicularly to the coil axis C of the coil 1, which axis corresponds here to the central axis Z. In particular, said circumferential directions CR, CC run in a ring plane RP of the fluid supply device 6 in the form of a ring stator. Said ring plane RP runs parallel to a common plane in which the fluid openings 7, 7a, ... are arranged.

[0068] The fluid supply device 6 is arranged movably, in particular pivotably, in the probe head 2. For this purpose, the fluid supply device 6 is pivotally mounted on two rods 16 that allow the fluid supply device 6 to pivot in the probe head 2. Furthermore, the fluid supply device 6 is configured to adjust the rotation axis R of the rotor 3 with respect to the adjustment axis A of the probe head 2 and with respect to the direction of the static magnetic field B of the magnetic resonance spectrometer when the probe head 2 is received in the magnetic resonance spectrometer. As shown in FIG. 4, the adjustment axis A of the probe head 2 runs parallel to the direction of the static magnetic field B of the magnetic resonance spectrometer when the probe head 2 is received in the magnetic resonance spectrometer. The fluid supply device 6 can therefore be used to adjust the rotation axis R of the rotor 3 to a so-called magic angle α of 54.7° (see FIG. 4). The magic angle α can therefore be adjusted by a mechanical movement, such as a pivot or a rotation, of the ring stator 6 via the rods 16 connected to the ring stator 6. During the magic angle adjustment, the coil 1 remains stationary while the axis of rotation R of the rotor 3 is synchronized with the movement of the ring stator 6.

[0069] As can be seen from figures 1 and 5a, the coil 1 according to the invention comprises a number of turns 4, 4a, ... arranged along a coil axis C extending along the coil 1. In the probe head 2, said coil axis C extends perpendicular to the adjustment axis A of the probe head 2 and to the direction of the static magnetic field B of the magnetic resonance spectrometer when the probe head 2 is received in the magnetic resonance spectrometer. Furthermore, said coil axis C extends in a plane extending perpendicular to the adjustment axis A of the probe head 2 and to the direction of the static magnetic field B.

[0070] As can be further seen from Figures 1 and 5a, the rotor 3 is entirely received within the coil 1. In other words, the coil 1 is entirely wound around the rotor 3, the shape of the rotor 3 corresponding to the shape of the coil 1, i.e. both the rotor 3 and the coil 1 are spherical. In addition, the coil 1 is tightly wound around the rotor 3, the gap G between the coil 1 and the rotor being less than or equal to 4 millimeters. Said gap G corresponds to the interval formed between the inner faces 17 of the turns 4, 4a, ... of the coil 1 facing the outer face 14 of the rotor 3 and said outer face 14 of the rotor 3, with respect to a direction extending perpendicular to the coil axis C.

[0071] As mentioned at the beginning, the coil 1 according to the invention not only serves the purpose of transmitting and receiving radio frequency signals, but also constitutes a fluid directing device 10 configured and arranged to direct a fluid provided by a fluid supply device 6 to the rotor 3. For this purpose, the coil is configured and arranged to generate a bearing force and a driving force which rotates the rotor 3 about its axis of rotation R. Said bearing force and driving force are generated by a fluid provided by the fluid supply device 6 and flowing through a gap G formed between the rotor 3 and the coil 1.

[0072] An embodiment of the coil 1 according to the invention will now be described in more detail: as can be seen in figure 5a, the turns 4, 4a, ... of the coil 1 define an elliptical shape, in the example shown a sphere.

[0073] As can be further seen from Fig. 5a, the circumference of the individual turns 4, 4a, ... of the coil 1 with respect to the circumferential direction CT of the turns 4, 4a, ... is elliptical and in the illustrated example circular. Moreover, the circumference of the individual turns 4, 4a, ... with respect to the circumferential direction CT of the turns 4, 4a, ... varies with respect to the coil axis C. With respect to the extension direction E extending from the beginning of the coil 1 provided by the first turn 4 of the coil 1 to the end of the coil 1 provided by the last turn 4f of the coil 1, the circumference of the turns 4, 4a, ... becomes gradually larger and then gradually smaller. Thus, the circumference of the turns 4, 4a, ... in the region of the beginning of the coil 1 and the circumference of the turns 4e, 4f in the region of the end of the coil 1 are smaller than the circumference of the turns 4c, 4d in the intermediate region of the coil 1, the circumference of one or more turns 4c, 4d in the intermediate region being maximum. This is in contrast to the solution known in the prior art and shown in Fig. 6a, in which all turns 4', 4a', ... of the coil 1' have the same circumference. Moreover, in the coil 1 according to the invention shown in Fig. 5a, the distance between successive turns 4, 4a, ... of the coil 1 remains constant with respect to the coil axis C. Moreover, the diameter dt of the individual turns 4, 4a, ... of the coil 1 likewise remains constant with respect to the coil axis C.

[0074] A high frequency finite element simulation was performed to compare the RF characteristics of a linear solenoid coil 1' with a cylindrical rotor 3' known in the current art and a spherical solenoid coil 1 with a spherical rotor 3 according to the present invention. The simulation model includes a spherical rotor 3 with a diameter of 3.9 mm and a spherical solenoid coil 1 with 7 turns (see FIG. 9a), and the magnetic field strength along the coil axis C is 24.5 A / m to 27.5 A / m in the spherical rotor 3 (see FIG. 5b). FIG. 6a shows a standard for comparison, here a commercially available cylindrical rotor 3' with a diameter of 2.2 mm with a sample volume of 30 microliters and an 8-turn solenoid coil 1'. FIG. 6b shows the magnetic field strength along the coil axis, where the magnetic field strength is 36 A / m at the sample center and drops to 15 A / m at the ends. For the linear solenoid coil 1', the magnetic field was downscaled to take into account the orientation along the magic angle. In order to maintain the same sample volume as the cylindrical rotor 3', a spherical rotor 3 with a diameter of 3.9 mm was used. Furthermore, the gap G between the coils 1, 1' and the sample in both simulations is kept the same, i.e., 0.6 mm. The number of turns 4, 4a, ..., turns 4', 4a', ... in each coil 1, 1' and the wire diameter dt were optimized (see Tables S1 and S2 below).

[0075] [Table 1]

[0076] [Table 2]

[0077] The average magnetic field above the sample area was calculated assuming a perfectly tuned and matched circuit with 5 mW RF input power. The maximum magnetic field of the cylindrical rotor is 57.3 A / m with an 8-turn coil of 7 mm and a wire diameter of 0.6 mm (see Table 1 below). The Bruker coil with a length of 7 mm, 7 turns and a wire diameter of 0.5 mm shows a slightly lower magnetic field. The spherical solenoid coil with the same windings and wire diameter shows a similar magnetic field to the linear solenoid coil. The coil with 9 turns and a wire diameter of 0.4 mm shows a higher magnetic field of 63.1 A / m, but the impedance is too high to match the circuit. The average magnetic field generated by both coils is similar, but the homogeneity is much better in the spherical solenoid coil (see Figure 5b). The linear solenoid coil shows a strong central magnetic field of 36 A / m, dropping to 15 A / m at the ends of the sample (see Figure 6b).

[0078] [Table 3]

[0079] From the simulation results, it can be concluded that with the same sample volume and sample coil spacing, the spherical coil 1 according to the present invention exhibits a comparable RF magnetic field to the linear solenoid coil 1' known in the current technology, but with better uniformity.

[0080] Furthermore, as can be seen from figures 7a to 9b, the rotors 3, 3' comprise sample chambers 5, 5' configured to receive a sample. The sample chambers 5, 5' can have various designs. For example, the sample chambers 5, 5' can be cylindrical, as shown in figures 7a to 8b, or can be ellipsoidal, in particular spherical, as shown in figures 9a and 9b.

[0081] Most spherical rotors reported to date have been machined with a cylindrical sample chamber.[18–21] This design provides stable spin due to the large moment of inertia from the thick rotor walls, but at the expense of sample volume and NMR filling factor.

[0082] Figures 7a and 7b show a spherical rotor 3' (rotor a) in the form of a high-precision 9.525 mm diameter yttria-stabilized zirconia (ZrO2) ball with a 2.54 mm diameter through hole and longitudinal turbine grooves, purchased from O'Keefe Ceramics (Woodland Park, Colorado) and known in previous publications [18, 19, 22]. The rotor 3' is equipped with turbine grooves 18 in the form of twelve 60° notch grooves, and the through hole defines a sample chamber 5' that can only hold 39 microliters of sample. As is known, zirconia is a commonly used material for cylindrical rotors because it is collision-resistant. However, this concern is less important for spherical rotors, since in a spherical geometry, the largest moment of inertia is always along the spin axis

[19] . Therefore, sapphire / ruby as rotor material was further investigated, considering the feasibility of machining to obtain a larger sample volume. Other advantages of sapphire / ruby include high thermal conductivity and excellent microwave transmission properties, which are important for applications in dynamic nuclear polarization (DNP) NMR experiments. More importantly, the single-crystal Al2O3 in sapphire / ruby is sensitive to the magic angle offset, allowing the magic angle to be tuned in situ

[23] .

[0083] Rotor b shown in Figures 8a and 8b is a high-precision 9.525 mm diameter ruby ​​(99% Al2O3 + 1% Cr2O3) spherical rotor 3' purchased from Saphirwerk AG (Bruck, Switzerland) with a through hole of 5.08 mm diameter. It further has 12 hemispherical grooves 18 on the equator. The grooves are 0.23 mm deep. The sample chamber 5' formed by the through hole and with two flat end caps defines a sample volume of 131 microliters.

[0084] Rotor c shown in Figures 9a and 9b is a high-precision ruby ​​spherical rotor 3 according to the invention with a diameter of 9.525 mm, which is further hollowed out to define a sample chamber 5 with a volume of 219 microliters. In particular, said sample chamber 5 is here formed by a through hole with a diameter of 5.08 mm and an additional spherical chamber of 7.5 mm. That is, the shape of the sample chamber 5 corresponds to the shape of the rotor 3. The hollow sample chamber 5 is machined using a 5-axis milling technique (DMU 50, DMG MORI). It is important to note here that this rotor 3 does not have turbine grooves for easier machining, as is the case for the rotor shown in Figures 7a-8b, but has a more robust rotor shell. It has been demonstrated that spherical rotors without grooves have similar spin frequencies to other rotor designs

[19] .

[0085] All spherical rotor caps were 3D printed on a Projet MJP 2500 (3D Systems) using an ABS-like resin (VisiJet M2R-CL).

[0086] These three types of spherical rotors were filled with KBr powder to evaluate the probe heads shown in Figures 1-4. The sample masses in rotor a, rotor b, and rotor c are 70.6 mg, 270.1 mg, and 405.3 mg, respectively. Rotors a and c were filled by compressing the sample using a rod that matched the diameter of the hole, while rotor b was packed more densely by sonicating while constantly applying force to the sample. The spherical solenoid coil 1 was hand-wound using 0.4 mm polyurethane / nylon coated copper wire. A 3D printed mold was used as a coil winding guide. Both the ring stator 6 and the mold were 3D printed on a Form 3 SLA 3D printer (Formlabs Inc., Somerville, MA) using clear v4 resin. After the spherical rotor is loaded into the spherical coil 1, the coil position is adjusted so that the spherical rotor is centered in the ring stator 6 and rotates around a rotation axis R perpendicular to the ring stator 6. The rotation axis 3 is then optimized by mechanically rotating the ring stator 6 to obtain the highest sideband intensity in the KBr spectrum.

[0087] Figures 10a and 10b show the MAS spectra of 79Br for all three rotor types. All NMR experiments were performed at room temperature on a Bruker Avance 600 MHz spectrometer using a customized single-resonance, small-aperture transmission line probe

[21] . A Bloch-damped pulse sequence with a 1 s interscan delay was used. 79Br spectra were acquired at 150.37 MHz using 14 μs π / 2 pulses at 200 W incident RF power. A spin frequency of approximately 4 kHz was maintained during data acquisition using nitrogen gas at a pressure of 2 bar. Four scans were acquired for each spectrum. Note that the spinning sidebands that gradually invert at higher frequencies are due to the long 90° pulses (14 μs), which efficiently excite only a limited frequency range. The highest NMR sensitivity was obtained with rotor c, a rotor according to the invention containing 405.3 mg KBr, while the lowest sensitivity was obtained from rotor a with 70.6 mg KBr, see the zoom of the central peak of FIG. 10a shown in FIG. 10b. The ratio of the signal integrals of each spectrum is 1:0.66:0.15, as is the ratio of the sample masses in each rotor (1:0.67:0.17). The zirconia spheres (rotor a) have the thickest walls on the equator, providing a large moment of inertia, and therefore the most stable spinning was expected. However, the inventors surprisingly found that the rotor according to the invention with thin walls and no grooves (rotor c) also showed extremely stable spinning over several hours. It was found that the KBr powder in the rotor was subjected to centrifugal forces during spinning, forming a hollow space in the center. The redistribution of the KBr sample in the rotor builds up a large moment of inertia for stable spinning.

[0088] Thus, the usefulness of a spherical coil tightly wound around a spherical rotor as an RF coil, as well as part of a rotating device for MAS, has been demonstrated. One particular advantage of this device is that the coil axis C is fixed perpendicular to the external magnetic field B, regardless of the rotation axis R of the rotor 3. All B1 magnetic fields generated are along the x / y axis, and experiments such as dynamic angle spinning (DAS) and variable angle spinning can be performed without compromising the B1 magnetic field. In other words, since the coil axis C is aligned perpendicular to the external magnetic field B, the invention utilizes all the RF power and further allows magic angle adjustment without coil movement. In addition, the ability of the spherical rotor to spin within the RF coil 1 relaxes the high precision requirements for stator fabrication, making stator development easier for smaller rotors. Furthermore, the fluid supply device 6 in the form of a ring stator that supplies the spinning gas and adjusts the magic angle α outside the coil 1 minimizes the gap G between the sample and the coil 1. It has also been confirmed that the NMR filling factor is significantly improved by increasing the sample volume and minimizing the sample coil distance. In particular, compared to a spherical rotor with a cylindrical sample chamber, the hollow spherical rotor leads to a six-fold higher signal integral. In addition, a comparison of the NMR sensitivity between the spherical rotor and a commercial cylindrical rotor using high-frequency finite element simulations shows similar B1 fields between the spherical rotor with a spherical solenoid coil and the cylindrical rotor with a straight solenoid coil.

[0089] References [1] Andrew, ER, Bradbury, A. & Eades, RG Nuclear Magnetic Resonance Spectra from a Crystal Rotated at High Speed. Nature 182, 1659 (1958). [2] Lowe, IJ Free induction decays of rotating solids. Phys. Rev. Lett. 2, 285-287 (1959). [3] Andrew, E. R. Magic angle spinning. Int. Rev. Phys. Chem. 1, 195-224 (1981). [4] Schaefer, J. & Stejskal, E. O. Carbon-13 Nuclear Magnetic Resonance of Polymers Spinning at the Magic Angle. J. Am. Chem. Soc. 1031, 1031-1032 (1975). [5] McDermott, A. Structure and Dynamics of Membrane Proteins by Magic Angle Spinning Solid-State NMR. Annu. Rev. Biophys. 38, 385-403 (2009). [6] Bougault, C., Ayala, I., Vollmer, W., Simorre, J. & Schanda, P. Studying intact bacterial peptidoglycan by proton-detected NMR spectroscopy at 100 kHz MAS frequency ☆. J. Struct. Biol. 0-1 (2018) doi:10.1016 / j.jsb.2018.07.009. [7] Clauss, J., Schmidt-Rohr, K. & Spiess, H. W. Determination of domain sizes in heterogeneous polymers by solid-state NMR. Acta Polym. 44, 1-17 (1993). [8] Trebosc, J., Wiench, J. W., Huh, S., Lin, V. S. & Pruski, M. Studies of Organically Functionalized Mesoporous Silicas Using Heteronuclear Solid-State Correlation NMR Spectroscopy under Fast Magic Angle Spinning. J. Ameican Chem. Soc. 127, 7587-7593 (2005). [9] Lesage, A. et al. Polarization Transfer over the Water - Protein Interface in Solids ** Angew. Chemie 47, 5851-5854 (2008).

[10] Doty, F. D. & Ellis, P. D. Design of high speed cylindrical NMR sample spinners. Rev. Sci. Instrum. 52, 1868-1875 (1981).

[11] Knight, M. J. et al. Structure and backbone dynamics of a microcrystalline metalloprotein by solid-state NMR. Proc. Natl. Acad. Sci. U. S. A. 109, 11095-11100 (2012).

[12] Retel, J. S. et al. Structure of outer membrane protein G in lipid bilayers. Nat. Commun. 8, 1-10 (2017).

[13] Theint, T. et al. Species-dependent structural polymorphism of Y145Stop prion protein amyloid revealed by solid-state NMR spectroscopy. Nat. Commun. 8, (2017).

[14] Petkova, a. T. et al. Self-propagating, molecular-level polymorphism in Alzheimer’s beta-amyloid fibrils. Science (80-. ). 307, 262-265 (2005).

[15] Kong, X. et al. Mapping of Functional Groups in Metal-Organic Frameworks. Science (80-. ). 341, 882-886 (2013).

[16] Wang, S. et al. Solid-state NMR spectroscopy structure determination of a lipid-embedded heptahelical membrane protein. Nat. Methods 10, 1007 (2013).

[17] Cegelski, L. et al. Rotational-Echo Double Resonance Characterization of the Effects of Vancomycin on Cell Wall Synthesis in Staphylococcus aureus †. Biochemistry 13053-13058 (2002) doi:10.1021 / bi0202326.

[18] Chen, P. et al. Magic angle spinning spheres. Sci. Adv. 4, 1-8 (2018).

[19] Osborn Popp, TM et al. Highly stable magic angle spinning spherical rotors. Magn. Reson. 1, 97-103 (2020).

[20] Gao, C. et al. Four millimeter spherical rotors spinning at 28 kHz with double-saddle coils for cross polarization NMR. J. Magn. Reson. 303, 1-6 (2019).

[21] Chen, P.-H. et al. Two millimeter diameter spherical rotors spinning at 68 kHz for MAS NMR. J. Magn. Reson. Open 8-9, 100015 (2021).

[22] Popp, TMO et al. Pneumatic angle adjustment for magic angle spinning spherical rotors. J. Magn. Reson. Open 6-7, 100014 (2021).

[23] Popp, TMO, Alaniva, NH & Barnes, AB Setting the Magic Angle Using Single Crystal Sapphire Rotors. J. Magn. Reson. Open 8-9, 100019 (2021). [Explanation of symbols]

[0090] 1 coil 1' Coil 2 Probe head 3 Rotor 3' rotor 4, 4a, ... turn 4', 4a'... turn 5. Sample Chamber 5' Sample chamber 6 Fluid Supply Device 7, 7a, ... fluid opening 8 Receptacles 9 Rotational Devices 10 Fluid Directing Device 11 Capacitor 12 tubes 13 sides 14 sides 15 Optical Fiber 16 Rod 17 sides 18 Groove C Coil shaft CT circumferential direction CR circumferential direction CC circumferential direction Z center axis F Flow direction E Extending direction A adjustment axis R rotation axis B. Static magnetic field direction P plane RP plane G gap at Distance dt diameter α Magic Angle β angle γ angle

Claims

1. A coil (1) for a probe head (2) of a magnetic resonance spectrometer having a rotor (3), comprising: the coil (1) is configured to transmit at least one radio frequency signal to excite a sample received in the rotor (3) and / or to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by a radio frequency signal; The coil (1) comprises a plurality of turns (4, 4a, ...) arranged along a coil axis (C) extending along the coil (1), The coil (1), characterized in that the turns (4, 4a, ...) of the coil (1) define an elliptical shape, preferably a sphere.

2. A coil (1) according to claim 1, the circumference of each of said turns (4, 4a, ...) in the circumferential direction (CT) of said turns (4, 4a, ...) is elliptical, preferably circular, and / or The coil, wherein the circumference of each of the turns (4, 4a, ...) in a circumferential direction (CT) of the turns (4, 4a, ...) varies with respect to the coil axis (C).

3. A coil (1) according to claim 1 or 2, The distance (at) between successive turns (4, 4a, ...) of the coil (1) and / or the wire diameter (dt) of the individual turns (4, 4a, ...) of the coil (1) remain constant or vary with respect to the coil axis (C).

4. A probe head (2) for a probe of a magnetic resonance spectrometer, comprising: A rotor (3) configured to rotate about a rotation axis (R); at least one rotating device (9) configured to rotate the rotor (3) about the rotation axis (R); At least one coil (1), preferably according to any one of claims 1 to 3, Equipped with The rotating device (9) comprises at least one fluid supply device (6) configured to supply a fluid to the rotor (3), the coil (1) is configured to transmit at least one radio frequency signal to excite a sample received in the rotor (3) and / or to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by a radio frequency signal; the rotating device (9) further comprises at least one fluid directing device (10) constructed and / or arranged to direct the fluid provided by the fluid supply device (6) to the rotor (3); The probe head, characterized in that the fluid directing device (10) comprises or consists of the coil (1).

5. A probe head (2) according to claim 4, The probe head, wherein the fluid directing device (10) is constructed and / or arranged to generate a bearing force and / or a driving force that rotates the rotor (3) about the axis of rotation (R).

6. A probe head (2) according to claim 4 or 5, said fluid supply device (6) comprises at least one fluid opening (7, 7a, ...), preferably a plurality of fluid openings (7, 7a, ...) for supplying said fluid to said rotor (3), The plurality of fluid openings (7, 7a, ...) of the probe head are preferably arranged at least one of: i) to rotate the rotor (3) about the axis of rotation (R); or ii) in at least one common plane (P).

7. A probe head (2) for a magnetic resonance spectrometer, comprising: A rotor (3) configured to rotate about a rotation axis (R); at least one rotating device (9) configured to rotate the rotor (3) about the rotation axis (R); At least one coil (1), preferably according to any one of claims 1 to 3, Equipped with The rotating device (9) comprises at least one fluid supply device (6) configured to supply a fluid to the rotor (3), the coil (1) is configured to transmit at least one radio frequency signal to excite a sample received in the rotor (3) and / or to receive at least one radio frequency signal emitted by the sample in response to excitation of the sample by a radio frequency signal; said fluid supply device (6) comprising a plurality of fluid openings (7, 7a, ...) for supplying said fluid to said rotor (3); The probe head, characterized in that the plurality of fluid openings (7, 7a, ...) are arranged at least one of: i) to rotate the rotor (3) about the axis of rotation (R); or ii) in at least one common plane (P).

8. A probe head (2) according to any one of claims 4 to 7, The coil (1) surrounds the rotor (3) at least partially, particularly preferably entirely, of the probe head.

9. A probe head (2) according to claim 8, the gap (G) between the coil (1) and the rotor (3) is less than or equal to 4 mm; and / or The probe head, wherein the gap (G) between the coil (1) and the rotor (3) is 50 micrometers to 4 millimeters, preferably 100 micrometers to 2 millimeters, and particularly preferably about 500 micrometers.

10. A probe head (2) according to any one of claims 4 to 9, the shape of the rotor (3) corresponds to the shape of the coil (1), and / or The probe head, wherein the rotor (3) comprises a sample chamber (5) configured to receive a sample, and the shape of the coil (1) corresponds to the shape of the sample chamber (5).

11. A probe head (2) according to any one of claims 4 to 10, The fluid supply device (6) comprises a receptacle (8); The coil (1) is at least partially, preferably entirely, disposed within the receptacle (8), said probe head.

12. A probe head (2) according to claim 11, said at least one fluid opening (7, 7a, ...) is arranged in the region of said receptacle (8) and / or The probe head, wherein the plurality of fluid openings (7, 7a, ...) are arranged at least partially, preferably entirely, along a circumferential direction (CR) of the receptacle (8) and / or at least partially, preferably entirely, along a circumferential direction (CC) of the coil (1).

13. A probe head (2) according to any one of claims 4 to 12, The fluid supply device (6) is configured to adjust the rotation axis (R) of the rotor (3) relative to an adjustment axis (A) of the probe head (2) and / or relative to a direction of a static magnetic field (B) of the magnetic resonance spectrometer when the probe head (2) is received in a magnetic resonance spectrometer.

14. A probe head (2) according to claim 13, the coil (1) is configured to be stationary during adjustment by the fluid supply device (6) relative to the probe head (2); and / or The fluid supply device (6) is configured to be movable during adjustment relative to the probe head (2).

15. A probe head (2) according to any one of claims 4 to 14, The coil (1) defines a coil axis (C); The coil axis (C) extends in at least one of the following directions: i) perpendicular to an adjustment axis (A) of the probe head (2); ii) perpendicular to a direction of a static magnetic field (B) of a magnetic resonance spectrometer when the probe head (2) is received in the magnetic resonance spectrometer; and iii) within a plane extending perpendicular to at least one of the adjustment axis (A) of the probe head (2) and the direction of a static magnetic field (B) of a magnetic resonance spectrometer when the probe head (2) is received in the magnetic resonance spectrometer.

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