Lockable rotor for low-temperature nmr spectroscopy

Abstract

Lockable rotor for low-temperature NMR spectroscopy. The invention relates to a rotor (1) for NMR spectroscopy, comprising: - a tubular body (2) comprising, at at least one of its longitudinal ends (4, 5), or open end(s), a cavity (3) which opens to the outside in order to contain a sample, and a blocking relief (6, 14); - a plug (7, 15) configured to fit into one of the open ends of the tubular body in order to seal it, the plug comprising a blocking relief (11, 18) so as to engage with the relief of the body in order to block the plug in the body, when fitting the plug into the body; and / or - a cap (22, 27) configured to fit around one of the open ends of the tubular body in order to seal it, the cap having a coefficient of thermal contraction greater than or equal to the coefficient of thermal contraction of the tubular body.

Description

[0001] Description

[0002] Title: Lockable rotor for low-temperature NMR spectroscopy.

[0003] Technical field

[0004] The present invention relates to the field of nuclear magnetic resonance (NMR) spectroscopy.

[0005] It relates more specifically to a rotor housing a sample to be analyzed by NMR.

[0006] Prior art

[0007] Nuclear magnetic resonance (NMR) spectroscopy is a non-destructive analysis method using the phenomenon of nuclear magnetic resonance (NMR), particularly to resolve molecular structures.

[0008] NMR occurs when unspinned atomic nuclei are placed in a static magnetic field and excited by electromagnetic radiation. This method is particularly used in organic chemistry, inorganic chemistry, biology, and materials science.

[0009] In solid NMR spectroscopy, it is usual to place the sample to be analyzed in a rotor in order to rotate it around an axis inclined at 54° 44', called the magic angle, relative to the static magnetic field.

[0010] The rotor, also called a sample holder, usually comprises a tubular body housing the sample conditioned in powder form within it and at least one cap to close the tubular body. A carrier fluid levitates the rotor arranged in a stator. The rotor is generally driven in rotation pneumatically. To ensure rotation, the rotor comprises blades at one of its longitudinal ends, forming a turbine which generally delimits the outer periphery of the cap. A working fluid projected onto the turbine thus sets the rotor in rotation at frequencies ranging from a few kHz to several tens of kHz.

[0011] To ensure physical integrity and pneumatic rotation for this range of rotation frequencies, the tubular body of the rotor is usually made of ceramic, for example an alloy comprising zirconium and yttrium. The tubular body can also be made of sapphire. These materials have the advantage, due to their low magnetic susceptibility, of not causing noise in the NMR measurement.

[0012] The material from which the turbine is made must withstand the mechanical stresses induced by high rotation frequencies. This material must also be sufficiently elastic so that the plug can be positioned during assembly in the tubular body while generating sufficient clamping force to ensure that it is held in position. Indeed, any variation in speed at these high rotation frequencies creates a torque that tends to separate the plug from the tubular body. The material generally used for the plug and the turbine is Vespel ®.

[0013] Furthermore, it is also known that increasing the magnetic field intensity, increasing the rotor rotation frequency, and / or using the dynamic nuclear polarization (DNP) phenomenon can improve the sensitivity and resolution of NMR spectroscopy.

[0014] It has been proven that, in NMR analysis, the lower the temperature, the higher the signal-to-noise ratio and the higher the gain due to the DNP phenomenon. Thus, high-resolution NMR spectrometers generally operate at low temperatures, especially around 100 K. Article [1] describes an NMR spectrometer using the DNP phenomenon and operating at temperatures below 100 K.

[0015] To date, the materials constituting the tubular body and the cap have different thermal contraction coefficients. This results in a contraction differential between the tubular body and the cap when the temperature is lowered, the cap contracting more than the tubular body. This contraction differential causes the clamping force of the cap in the tubular body to decrease to almost zero for temperatures around 100 K. Consequently, at these temperatures, the slightest variation in the rotation frequency of the rotor causes a torque that tends to separate the cap from the tubular body. There is then no longer any driving effect in rotation of the entire rotor by the turbine and the cap no longer closes the tubular body, which can lead to the loss of the sample.

[0016] To solve this problem, one could consider increasing the clamping force at room temperature between the stopper and the tubular body. This solution cannot be adopted because it would make it impossible to manually insert the stopper into the tubular body, and would complicate or even make it impossible to extract the stopper after the NMR measurement without damaging the tubular body.

[0017] US Patent 10,914,799 B2 describes a rotor for NMR spectroscopy comprising a tubular body and a cap comprising a hub whose material has a negative coefficient of thermal contraction. Thus, the hub expands when the temperature decreases, which allows the maintenance of sufficient tightening torque of the cap in the tubular body to carry out NMR spectroscopy at low temperature. However, the manufacture of the cap of US Patent 10,914,799 B2 is particularly complex, in particular, because the cap is very small and therefore requires extremely precise machining and preparation.

[0018] There is therefore a need for a rotor suitable for low-temperature NMR spectroscopy, which overcomes the aforementioned drawbacks. In particular, there is a need for a rotor suitable for low-temperature NMR spectroscopy, which is simple to manufacture, and whose cap does not separate from the tubular body during rotation of the rotor at low temperature.

[0019] The aim of the invention is to respond, at least in part, to this(these) need(s).

[0020] Statement of the invention

[0021] To this end, the invention relates to a rotor for nuclear magnetic resonance (NMR) spectroscopy, extending along a longitudinal axis and comprising:

[0022] - a tubular body comprising, at at least one of its longitudinal ends, called open end(s), a cavity opening outwards and intended to contain a sample to be analyzed by NMR, and within it, at least one blocking relief;

[0023] - at least one plug configured to fit at least partially into one of the open ends of the tubular body so as to close it, the plug comprising a blocking relief of complementary shape with the relief of the tubular body so that, when the plug is fitted into the body, said blocking reliefs engage in each other and thus block the plug in the body; and / or

[0024] - at least one cap configured to fit at least partially around one of the open ends of the tubular body of the tubular body so as to close it, the cap having a thermal contraction coefficient greater than or equal to the thermal contraction coefficient of the tubular body so as to block the cap in the body, during operation of the rotor.

[0025] The coefficient of thermal contraction of a part corresponds to its ability to contract when the temperature decreases. The higher the coefficient of thermal contraction, the greater the contraction will be.

[0026] Preferably, the locking relief of the tubular body is a radial groove formed internally in the thickness of the tubular body and the locking relief of the plug is a radial rib on the external periphery of the plug arranged to snap into the groove, when the plug is fitted into the body.

[0027] Alternatively, the locking relief of the plug may be a groove provided in the thickness at the radial external periphery of the plug and the locking relief of the tubular body may be a radial internal rib arranged to snap into the groove when the plug is fitted into the body.

[0028] Preferably, the groove and the rib each have an annular shape.

[0029] Preferably, the groove has a depth greater than or equal to 0.1 mm and / or the rib has a height greater than or equal to 0.1 mm.

[0030] Preferably, the plug comprises a cap and a sleeve configured to fit into the tubular body with the cap projecting, preferably in abutment, at the open end of the tubular body, the sleeve comprising, on its outer periphery, the blocking relief of the plug.

[0031] Preferably, the sleeve is split, preferably comprising at least two slots extending along the length of the sleeve.

[0032] Preferably, the sleeve comprises a length of between 1.2 and 1.8 mm.

[0033] Preferably, the sleeve has an outer diameter greater than the opening diameter of the open end, for example the outer diameter of the sleeve is between 2.4 and 2.7 mm.

[0034] Preferably, the difference between the outer diameter of the cap and the outer diameter of the body at its open end is less than or equal to 0.05 mm. Preferably, the outer diameter of the cap is substantially equal to the outer diameter of the body at its open end.

[0035] Preferably, the rotor includes an insert configured to fit within the sleeve so as to press the sleeve against the cavity wall and thereby mechanically lock the plug into the body.

[0036] Preferably, the cap comprises a threaded opening opening into the sleeve and the insert is configured to screw into said opening.

[0037] Preferably, the insert is made of polymer, preferably polyetheretherketone.

[0038] Preferably, the cap comprises a cap and a hollow sleeve configured to fit around the open end of the tubular body with the cap protruding.

[0039] Preferably, the sleeve is configured to fit tightly around the tubular body.

[0040] Preferably, the difference between the outer diameter of the cap and the outer diameter of the sleeve is less than or equal to 0.05 mm. Preferably, the outer diameter of the cap is substantially equal to the outer diameter of the sleeve.

[0041] Preferably, the portion of the tubular body around which the cap is intended to be fitted, called the fitting portion, has a reduced external diameter compared to that of the rest of the tubular body.

[0042] Preferably, the difference between the outer diameter of the cap sleeve and the outer diameter of the tubular body beyond its fitting portion is less than or equal to 0.05 mm. Preferably, the outer diameter of the sleeve is substantially equal to the outer diameter of the tubular body beyond its fitting portion.

[0043] Preferably, the stopper and / or cap are made of plastic, preferably a polyimide-based polymer, for example Vespel®. Advantageously, a stopper and / or cap made of these materials has a very low magnetic susceptibility, which limits noise during NMR spectroscopy. In addition, these materials are resistant to mechanical stresses due to high rotation frequencies during NMR spectroscopy. They are also flexible, which facilitates the fitting of the stopper and / or cap.

[0044] Preferably, the rotor comprises blades forming a turbine. According to a first embodiment, the cavity may open at only one end of the tubular body, called the open end, the rotor comprising a plug or a cap according to the above to close said open end.

[0045] The turbine may be comprised of the cap or the end cap. Preferably, the blades are formed in the end cap of the cap or in the end cap of the end cap.

[0046] Alternatively, the rotor may comprise a cylindrical part in which the blades of the turbine are formed, the cylindrical part being configured to attach, preferably by shrink fitting, to the end of the tubular body opposite the open end. The cylindrical part may be made of plastic, preferably polyimide-based plastic, for example Vespel®.

[0047] According to a second embodiment, the cavity may open at both ends of the tubular body, called open ends, the rotor comprising two plugs according to the above to close each of the open ends, at least one of the plugs comprising a turbine. Preferably, the blades are formed in the cap of the plug(s) comprising a turbine. Preferably, the cap of a plug not comprising a turbine is relatively smooth.

[0048] According to a third embodiment, the cavity may open at both ends of the tubular body, called open ends, the rotor comprising two caps according to the above to close each of the open ends, at least one of the caps comprising a turbine. Preferably, the blades are formed in the cap of the cap(s) comprising a turbine. Preferably, the cap of a cap not comprising a turbine is relatively smooth.

[0049] According to a fourth embodiment, the cavity may open at both ends of the tubular body, called open ends, the rotor comprising a plug and a cap according to the above to close each of the open ends, the plug and / or the cap comprising a turbine. Preferably, the blades are formed in the cap of the plug and / or the cap comprising a turbine. Preferably, the cap of the one between the plug and the cap not comprising the turbine is relatively smooth.

[0050] Preferably, the tubular body has a cylindrical shape with a length of between 10 and 20 mm and / or an outer diameter of between 0.7 and 4.0 mm. Preferably, the open end(s) have an opening diameter of between 0.5 and 3.6 mm.

[0051] Preferably, the tubular body is made of ceramic, preferably zirconium-based ceramic, for example a mixture of zirconium and yttrium. Advantageously, a body made of these materials has a very low magnetic susceptibility, which limits noise during NMR spectroscopy. In addition, these materials are resistant to mechanical stresses due to high rotation frequencies during NMR spectroscopy.

[0052] Preferably, the weight of the rotor is less than or equal to 1 g.

[0053] The invention also relates to a spectroscope for nuclear magnetic resonance (NMR) spectroscopy, comprising a rotor according to the present invention.

[0054] The present invention therefore essentially consists of a rotor for nuclear magnetic resonance spectroscopy comprising a plug and / or a cap for closing the cavity of the tubular body. The plug and / or the cap are adapted to be kept fitted in or around the tubular body even in the event of a strong decrease in temperature causing a contraction differential between the plug, respectively the cap, and the tubular body. During NMR spectroscopy, the plug and / or the cap remain integral with the tubular body even in the event of a variation in the rotation frequency of the rotor causing a rotation torque which may be significant between the plug, respectively the cap, and the tubular body.

[0055] Furthermore, the rotor according to the present invention is simple to manufacture and does not require precision machining which would prove expensive.

[0056] Brief description of the drawings

[0057] Other advantages and characteristics will become more apparent upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures:

[0058] [Eig 1] Figure 1 is a schematic longitudinal sectional view of a rotor for NMR spectroscopy according to the present invention, the rotor comprising a cap and a tubular-shaped body with an opening at one end, the other end being closed;

[0059] [Eig 2] Figure 2 is a schematic longitudinal sectional view of a rotor for NMR spectroscopy according to the present invention, the rotor comprising two caps and a tubular-shaped body with an opening at each of its ends; [Fig 3] Figure 3 is a schematic longitudinal sectional view of a rotor for NMR spectroscopy according to the present invention, the rotor comprising a cap and a tubular-shaped body with an opening at one end, the other end being closed;

[0060] [Fig 4] Figure 4 is a schematic longitudinal sectional view of a rotor for NMR spectroscopy according to the present invention, the rotor comprising two caps and a tubular-shaped body with an opening at each of its ends;

[0061] [Fig 5] Figure 5 is a schematic view in longitudinal section of a rotor for NMR spectroscopy according to the present invention, the rotor comprising a cap and a tubular body with an opening at one end, the other end being closed and on which a cylindrical part forming a turbine is fixed.

[0062] Detailed description

[0063] For reasons of clarity, the various elements of the figures are represented in free scale, the actual dimensions of the different parts not necessarily being respected.

[0064] Figure 1 illustrates an embodiment of a rotor 1 with a longitudinal axis X for NMR spectroscopy according to the present invention. The rotor 1 comprises a blind body 2 of hollow tubular shape, the cavity 3 of which extends over a portion of the length of the body 2. The blind cavity 3 opens at one of the longitudinal ends 4 of the body 2. The closed longitudinal end 5 of the body 2 may have a flat bottom. The body 2 also comprises a locking groove 6 formed in its thickness at the internal periphery of the cavity 3 and close to the open end 4.

[0065] The rotor 1 also comprises a plug 7 comprising a cap 8 and a split sleeve 9 in the longitudinal extension of the cap 8. The plug 7 is preferably in one piece. The cap 8 has an outside diameter greater than the inside diameter of the body 2 delimiting the cavity 3. The outside diameter of the cap 8 is in particular greater than the outside diameter of the split sleeve 9, thus forming a shoulder. The cap 8 has blades 10 on its radial outer periphery, forming a turbine. The split sleeve 9 comprises, on its radial outer periphery, a locking rib 11 in the form of a ring. The split sleeve 9 is configured to fit into the cavity 3 of the body 2. The slot(s) of said sleeve 9 make the latter flexible, which facilitates its insertion into the cavity.

[0066] 3.

[0067] When fitting, the locking rib 11 snaps into the locking groove 6, thus ensuring the mechanical locking of the plug 7 in the body 2.

[0068] When the sleeve 9 is inserted and locked in the cavity 3, the cap 8 is in abutment against the body 2.

[0069] The depth of the groove 6 and the height of the rib 11 are chosen so that, despite the contraction differential between the plug 7 and the body 2 during a decrease in temperature, for example from a temperature of 293 K to a temperature less than or equal to 100 K, for example to a temperature between 10 K and 80 K, the rib 11 remains snapped into the groove 6.

[0070] Furthermore, the cap 8 comprises a longitudinal opening 13 which is threaded over at least part of its length and that of the split sleeve 9.

[0071] Once the split sleeve 9 is fitted into the body 2, a threaded insert 12 can be screwed into the tapped opening 13 until it is inserted into the split sleeve 9.

[0072] This insert 12 thus screwed ensures mechanical locking of the split sleeve 9 blocked in the cavity 3.

[0073] In the embodiment illustrated in Figure 1, the rotor 1 has a length equal to 17 mm, a diameter equal to 3.2 mm and a total mass equal to 0.1 g.

[0074] Figure 2 illustrates another embodiment of a rotor 1 for NMR spectroscopy according to the present invention. The rotor 1 is similar to that illustrated in Figure 1, except that the cavity 3 of the body 2 is a through cavity, and therefore the other end 5 of the body 2 is open. The body 2 comprises a second locking groove 14 formed in its thickness at the internal periphery of the cavity 3 and close to the other open end 5.

[0075] The rotor 1 also comprises a second cap 15 comprising a cap 16 and a split sleeve 17 in the longitudinal extension of the cap 16. The cap 16 has an outside diameter greater than the opening diameter of the cavity 3 at the open end 5. The outside diameter of the cap 16 is in particular greater than the outside diameter of the split sleeve 17, thus forming a shoulder. The cap 16 has a relatively smooth outside surface. The split sleeve 17 comprises, on its radial outer periphery, a locking rib 18 in the form of a ring.

[0076] The split sleeve 17 is configured to fit into the cavity 3 of the body 2. The slot(s) of said sleeve 17 make the latter flexible, which facilitates its insertion into the cavity 3. During fitting, the rib 18 snaps into the second groove 14, thus ensuring the mechanical locking of the second plug 15 in the body 2. When the sleeve 17 is inserted into the cavity 3, the cap 16 abuts against the open end 5 of the body 2.

[0077] The depth of the second groove 14 and the height of the rib 18 are chosen so that, despite the contraction differential between the second plug 15 and the body 2 during a decrease in temperature, for example from a temperature of 293 K to a temperature less than or equal to 100 K, the rib 18 remains clipped into the second groove 14.

[0078] Furthermore, the cap 16 comprises a longitudinal opening 20 which is threaded over at least part of its length and that of the split sleeve 17.

[0079] Once the split sleeve 17 is fitted into the body 2, a threaded insert 19 can be screwed into the tapped opening 13 until it is inserted into the split sleeve 17.

[0080] This insert 19 thus screwed ensures mechanical locking of the split sleeve 17 blocked in the cavity 3.

[0081] Figure 3 illustrates another embodiment of a rotor 1 with a longitudinal axis X for NMR spectroscopy according to the present invention. The rotor 1 comprises a blind body 2 of hollow tubular shape, the cavity 3 of which extends over a portion of the length of the body 2. The blind cavity 3 opens at one of the longitudinal ends 4 of the body 2. The closed longitudinal end 5 of the body 2 may have a flat bottom. The body 2 also comprises, at its open end 4, a fitting portion 21 having a reduced external diameter compared to that of the rest of the body 2, forming a shoulder.

[0082] The rotor 1 also comprises a cap 22 comprising a cover 23 and a sleeve 24 in the longitudinal extension of the cover 13. The cover 23 comprises blades 25 on its radial outer periphery forming a turbine. The sleeve 24 has an opening 26 adapted to fit around the fitting portion 21 and thus close the cavity 3 to ensure the maintenance of a sample housed in the body 2. The fitting is carried out manually or automatically at a first temperature, for example at room temperature.

[0083] The sleeve 24 is made of a material having a thermal contraction coefficient greater than the thermal contraction coefficient of the material constituting the fitting portion 21. Thus, during a temperature decrease, for example to a second temperature less than or equal to 100 K, the contraction differential between the sleeve 24 and the fitting portion 21 creates a locking force by tightening the cap 22 around the body 2. This tightening force guarantees the mechanical maintenance between the cap 22 and the body 2 during low-temperature NMR spectroscopy.

[0084] Figure 4 illustrates another embodiment of a rotor 1 for NMR spectroscopy according to the present invention. The rotor 1 is similar to that illustrated in Figure 3, except that the cavity 3 of the body 2 is a through cavity and that the rotor 1 comprises a second cap 27. Thus, the end 5 is here open. The body 2 comprises at this open end 5 a second fitting portion 28 having a reduced outside diameter compared to that of the rest of the body 2 by forming a shoulder.

[0085] The second cap 27 comprises a cap 29 and a sleeve 30 in the longitudinal extension of the cap 29. The cap 29 has a relatively smooth outer surface. The sleeve 30 comprises an opening 31 adapted to fit around the fitting portion 28 and thus close the open end 5. The fitting is carried out manually or automatically at a first temperature, for example at 293 K.

[0086] The sleeve 30 is made of a material having a thermal contraction coefficient greater than the thermal contraction coefficient of the material constituting the fitting portion 28. Thus, during a temperature decrease, for example to a second temperature less than or equal to 100 K, the contraction differential between the sleeve 30 and the fitting portion 28 creates a locking force by clamping the second cap 27 around the body 2. This clamping force ensures that the second cap 27 is held with the body 2 during low-temperature NMR spectroscopy. Figure 5 illustrates another embodiment of a rotor 1 for NMR spectroscopy according to the present invention. The rotor 1 comprises a hollow body 2 of tubular shape whose cavity 3 is blind. The body 2 comprises a fitting portion 28 at its open end 5.A plug 27 is provided to fit around said fitting portion 28 and thereby close the open end 5.

[0087] The body 2 comprises at its closed end 4 a projecting portion forming a tenon 32. The rotor 1 also comprises a cylindrical part 33 comprising a mortise 34 and blades 35 on its outer radial surface forming a turbine. The mortise 34 can be fixed by shrinking around the tenon 32, and thus block the cylindrical part 33 on the body 2. The shrinking can be done at room temperature, that is to say around 293 K. During a decrease in temperature, for example to a temperature less than or equal to 100 K, the tenon 32 remains blocked in the mortise 34 ensuring the fixing of the cylindrical part 33 with the body 2.

[0088] In the embodiment of Figure 5, the conditioning (housing) of a sample in the cavity 3 is carried out by the open end 5. Thus, it is the cap 27 which guarantees the closure of the cavity 3 during NMR spectroscopy. Advantageously, this cap 27 has a cover 29 with a relatively smooth surface which allows it to be less subjected to the driving fluid of the spectroscope, and therefore less sensitive to variations in the rotation speed of the rotor 1.

[0089] Other variations and improvements may be envisaged without departing from the scope of the invention.

[0090] List of cited references

[0091] [1]: Yoh Matsuki and Toshimichi Fujiwara, “Cryogenic Platforms and Optimized DNP sensitivity”, eMagRes, 2018, Vol 7: 9-24.

Claims

Claims 1. Rotor (1) for nuclear magnetic resonance (NMR) spectroscopy, extending along a longitudinal axis (X) and comprising: - a tubular body (2) comprising, at at least one of its longitudinal ends (4, 5), called open end(s), a cavity (3) opening outwards and intended to contain a sample to be analyzed by NMR, and within it, at least one blocking relief (6, 14); - at least one plug (7, 15) configured to fit at least partially into one of the open ends of the tubular body so as to close it, the plug comprising a blocking relief (11, 18) of complementary shape with the relief of the tubular body so that, when the plug is fitted into the body, said blocking reliefs engage in one another and thus block the plug in the body, the blocking relief of the tubular body being a radial groove formed internally in the thickness of the tubular body and the blocking relief of the plug being a radial rib on the external periphery of the plug arranged to snap into the groove, when the plug is fitted into the body, the depth of the groove as well as the height of the rib being chosen so that, despite the contraction differential between the plug and the body during a decrease in temperature ranging from 293 K to at most 100 K,the rib remains clipped into the groove; and / or, - at least one cap (22, 27) configured to fit at least partly around one of the open ends of the tubular body so as to close it, the cap having a thermal contraction coefficient greater than or equal to the thermal contraction coefficient of the tubular body so as to block the cap around the body, during operation of the rotor, the cap comprising a cap (23, 29) and a hollow sleeve (24, 30) configured to fit around the open end of the tubular body with the cap projecting, the portion of the tubular body around which the cap is intended to fit, called the fitting portion (21, 28), having an outside diameter reduced compared to that of the rest of the tubular body, the difference between the outside diameter of the sleeve of the cap and the outside diameter of the tubular body beyond its fitting portion being less than or equal to 0.05 mm.

2. Rotor (1) for nuclear magnetic resonance (NMR) spectroscopy, extending along a longitudinal axis (X) and comprising: - a tubular body (2) comprising, at at least one of its longitudinal ends (4, 5), called open end(s), a cavity (3) opening outwards and intended to contain a sample to be analyzed by NMR, and within it, at least one blocking relief (6, 14); - at least one plug (7, 15) configured to fit at least partially into one of the open ends of the tubular body so as to close it, the plug comprising a blocking relief (11, 18) of complementary shape with the relief of the tubular body so that, when the plug is fitted into the body, said blocking reliefs engage in one another and thus block the plug in the body, the blocking relief of the plug being a groove formed in the thickness at the radial external periphery of the plug and the blocking relief of the tubular body being a radial internal rib arranged to snap into the groove, when the plug is fitted into the body, the depth of the groove as well as the height of the rib being chosen so that, despite the contraction differential between the plug and the body during a decrease in temperature ranging from 293 K to at most 100 K, the rib remains snapped into the groove; and / or - at least one cap (22, 27) configured to fit at least partly around one of the open ends of the tubular body so as to close it, the cap having a thermal contraction coefficient greater than or equal to the thermal contraction coefficient of the tubular body so as to block the cap around the body, during operation of the rotor, the cap comprising a cap (23, 29) and a hollow sleeve (24, 30) configured to fit around the open end of the tubular body with the cap projecting, the portion of the tubular body around which the cap is intended to fit, called the fitting portion (21, 28), having an outside diameter reduced compared to that of the rest of the tubular body, the difference between the outside diameter of the sleeve of the cap and the outside diameter of the tubular body beyond its fitting portion being less than or equal to 0.05 mm.

3. Rotor according to one of the preceding claims, the cap comprising a cap (8, 16) and a sleeve (9, 17) configured to fit into the tubular body with the cap projecting, preferably in abutment, at the open end of the tubular body, the sleeve comprising, on its external periphery, the blocking relief of the plug.

4. Rotor according to claim 3, comprising an insert (12) configured to be housed in the sleeve so as to press the sleeve against the wall of the cavity and thus mechanically lock the plug blocked in the body.

5. Rotor according to one of the preceding claims, the stopper and / or the cap being made of plastic, preferably of polyimide-based polymer, for example Vespel ®.

6. Rotor according to one of the preceding claims, comprising blades (10, 25, 35) forming a turbine.

7. Rotor according to one of the preceding claims, the tubular body having a cylindrical shape with a length of between 10 and 20 mm and / or an external diameter of between 0.7 and 4.0 mm.

8. Rotor according to one of the preceding claims, F (the) open end(s) having an opening diameter of between 0.5 and 3.6 mm.

9. Rotor according to one of the preceding claims, the tubular body being made of ceramic, preferably zirconium-based ceramic, for example a mixture of zirconium and yttrium.

10. Rotor according to one of the preceding claims, the weight of the rotor being less than or equal to 1 g.

11. Spectroscope for nuclear magnetic resonance (NMR) spectroscopy, comprising a rotor (1) according to one of the preceding claims.

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