Device for parameterising a probe having two sealed enclosures and use thereof in the field of low-temperature nuclear magnetic resonance (NMR) spectroscopy analysis

Abstract

The invention relates to a device (1) comprising: - a sealed enclosure (2) comprising a sheath (6) that opens onto the outside (7) of the sealed enclosure; - a cryogenic chamber (3) arranged in the sealed enclosure and comprising an opening (19) that opens into the sealed enclosure; - an adjusting rod (25) translatably mounted in the cryogenic chamber in order to adjust the positioning of an element accommodated in the cryogenic chamber; - a transmission bar (10) that sealingly passes through the sheath and is translatably movable along the longitudinal axis of the sheath by means of an element outside the sheath, the transmission bar being connected to the adjusting rod in order to transmit the translation of the bar to the rod and vice versa; - a corrugated bellows (22) sealingly attached to the transmission bar and around the opening in order to seal the cryogenic chamber.

Description

[0001] Description

[0002] Title: Device for setting a probe with a double hermetic enclosure, Application to analysis by low-temperature nuclear magnetic resonance (NMR) spectroscopy.

[0003] Technical field

[0004] The present invention relates to dual-chamber systems, in particular systems comprising a low-temperature box, called a cryogenic box, contained in a hermetic vacuum chamber.

[0005] Although described for a nuclear magnetic resonance (NMR) spectroscopy application, the present invention can be implemented for any double hermetic enclosure system, i.e. for any system comprising a hermetic enclosure arranged inside another hermetic enclosure.

[0006] Prior art

[0007] Nuclear magnetic resonance (NMR) spectroscopy is a non-destructive analytical method that uses the phenomenon of nuclear magnetic resonance (NMR), particularly to analyze molecular structures. NMR occurs when unaffected spin-free 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.

[0008] In solid-state NMR spectroscopy, it is usual to place the sample to be analyzed on a rotor in order to rotate it around an axis inclined at 54°44', called the magic angle, relative to the static magnetic field.

[0009] It is also known that increasing the magnetic field strength, increasing the rotor rotation frequency, and / or using the dynamic nuclear polarization (DNP) phenomenon can improve the sensitivity and resolution of NMR spectroscopy.

[0010] It has been proven that, in NMR analysis, the lower the temperature, the higher the signal-to-noise ratio and the greater 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.

[0011] To achieve low temperatures, for example around or below 100 K, it is preferable for the NMR spectrometer to operate autonomously and in a closed loop. A device operating autonomously is one that does not require a cryogenic fluid supply. A closed loop device is one in which a working fluid circulates without exposure to the external environment and without transfer of fluid out of the loop.

[0012] In a stand-alone, closed-loop NMR spectrometer, it is important to maintain high purity of the working fluid, i.e. it must be as free as possible from impurities of any kind (gaseous, solid in the form of particles, from hydrocarbons, etc.).

[0013] NMR spectrometers operating autonomously and in a closed loop generally comprise a probe with a double hermetic enclosure, i.e. comprising a vacuum hermetic enclosure, for example at a pressure less than or equal to 10' 5 mbar, and a sealed box, arranged in the hermetic enclosure, pressurized, for example up to 4 bar, and at cryogenic temperature, for example around or below 100 K. This arrangement of the cryogenic box in the hermetic vacuum enclosure guarantees excellent thermal insulation and therefore allows the performance of NMR spectrometry at low or even very low temperatures.

[0014] Furthermore, the magnetic field of the NMR spectrometer can be slightly modified depending on the atomic nucleus of the material to be analyzed. To achieve this, the probe includes several components called tuning capacitors that are housed in the cryogenic box. Each of the tuning capacitors includes a movable core that allows the impedance of a probe coil to be precisely adjusted depending on the position of the core in the coil.

[0015] The arrangement of the tuning capacities in the probe's cryogenic box makes them difficult to access and therefore complicates their adjustment.

[0016] Similarly, in such NMR spectrometers, the stator, which rotates the sample mounted on a rotor at an inclination below the magic angle, is arranged in the probe's sealed cryogenic box. The stator is therefore difficult to access. One method considered for adjusting the tuning capabilities and / or the stator tilt angle consists of dismantling and then reassembling the sealed enclosure and the cryogenic box at room temperature. Such a method is tedious, time-consuming and requires purification of the cryogenic box after reassembly in order to operate the NMR spectrometer autonomously and in a closed loop. In addition, such a method is also complex to implement because it requires anticipation of electronic and mechanical changes to the tuning capabilities and / or the stator caused by the descent to very low temperature.

[0017] There is therefore a need for a device for easily and quickly adjusting the tuning capabilities and / or the stator tilt angle of an NMR spectrometer comprising a double hermetic enclosure probe.

[0018] More generally, there is a need for a device suitable for easily and quickly adjusting and moving elements housed in a box operating at cryogenic temperatures, itself arranged in a hermetic enclosure.

[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 do this, the invention relates to a device, comprising:

[0022] - a hermetic enclosure comprising at least one sheath opening outside the hermetic enclosure,

[0023] - a cryogenic box arranged in the hermetic enclosure and comprising at least one opening opening into the hermetic enclosure,

[0024] - at least one adjustment rod mounted in translation in the cryogenic box so as to adjust the positioning of an element housed in the cryogenic box,

[0025] - at least one transmission bar passing through the sheath in a sealed manner, the transmission bar being movable in translation along the longitudinal axis of the sheath by an element arranged outside the sheath, the transmission bar being connected to the adjustment rod so that the translation of the bar is transmitted to the rod and vice versa,

[0026] - at least one corrugated bellows tightly fixed to the transmission bar and around the opening so as to hermetically close the cryogenic box.

[0027] Preferably, the sheath comprises a stuffing box configured to be compressed with sealing onto the transmission bar while leaving it movable in translation. Preferably, the stuffing box comprises at least one, preferably at least two, sealing gasket(s), and clamping rings, the clamping ring(s) being configured to compress the sealing gasket(s) onto the transmission bar.

[0028] Preferably, the stuffing box comprises an annular chamber in which the sealing gasket(s) is / are partly housed, the annular chamber being at a pressure less than or equal to 1.10' 3 mbar.

[0029] Preferably, the sheath comprises a guide sleeve configured to guide the transmission bar in translation and at least one locking means to lock the transmission bar in rotation.

[0030] Preferably, the device comprises a wheel accessible from outside the sheath and a transformation mechanism configured to transform the rotation of the wheel into a translation of the transmission bar along the axis of the sheath. Preferably, the transmission bar comprises a threaded portion and the transformation mechanism comprises a nut or a toothed wheel to form, with the threaded portion, a screw jack, respectively a rack and pinion system.

[0031] Preferably, the device includes ball bearings configured to facilitate rotation of the wheel.

[0032] The rotation of the wheel can be done manually and / or motorized. The transformation mechanism can comprise a speed reducer configured to transmit the rotation of the wheel into an output rotation, the ratio between the output rotation speed and the rotation speed of the wheel being less than 1 / 15, the transformation mechanism being configured to transform the output rotation into a translation of the transmission bar.

[0033] Preferably, the corrugated bellows is metallic.

[0034] Preferably, the corrugated bellows is hermetically welded to the transmission bar.

[0035] Preferably, the device comprises an annular seal ensuring the sealing of the fixing of the corrugated bellows around the opening.

[0036] According to a first alternative, the device may comprise a transmission cable, one of its ends being fixed to the transmission bar and the other of its ends being fixed to the adjustment rod. Preferably, the device comprises a guide tube configured to guide the sliding of the transmission cable. Preferably, the guide tube extends along a curve, preferably in the shape of an S.

[0037] Preferably, the device comprises a return spring mounted around and fixed to the adjustment rod so as to cause it to translate towards the inside of the cryogenic box, when the cable is relaxed by a translation of the transmission bar towards the inside of the cryogenic box.

[0038] Alternatively, the adjustment rod can be attached directly to the transmission rod.

[0039] Preferably, the device comprises at least one tuning capacity arranged in the cryogenic box, the tuning capacity comprising a core movable in translation to vary the tuning capacity, the end of the adjustment rod opposite that connected to the transmission bar being connected, preferably fixed, to the core.

[0040] Preferably, the device comprises a stator arranged in the cryogenic box and mounted to rotate about a transverse axis, the adjustment rod being connected, preferably fixed, to the stator so that the translation of the adjustment rod sets the stator in rotation about the transverse axis.

[0041] Preferably, the sealed enclosure is at a pressure of less than 10' 5 mbar.

[0042] Preferably, the cryogenic box is at a pressure between 1000 and 4000 mbar and / or at a temperature below 30 K.

[0043] Preferably, the device constitutes a probe of a nuclear magnetic resonance (NMR) spectrometer. Preferably, the probe comprises a stator and at least one adjustment rod whose translation modifies the inclination of the stator, and / or at least one adjustment rod whose translation modifies a tuning capacity of the probe.

[0044] The present invention therefore essentially consists of a device comprising a hermetic enclosure, a cryogenic box arranged in the hermetic enclosure and a positioning adjustment rod for the elements contained in the cryogenic box which is connected to a transmission bar accessible from the outside so that the translation of one ensures that of the other and vice versa, even in the case of a non-rigid connection between them. The mounting of the adjustment rod and the transmission bar is carried out while keeping the cryogenic box and the hermetic enclosure sealed, in particular by means of a sealed bellows fixed to the transmission bar. The positioning adjustment of the elements contained in the box can, for example, make it possible to choose the impedance of a tuning capacitor contained in the cryogenic box.

[0045] Externally adjustable components are easy to implement and take up little space.

[0046] In particular, the bellows, preferably in the form of a corrugated bellows, ensures the sealing of the cryogenic box at room temperature as well as at low temperatures, for example at a temperature below 100 K. The corrugated bellows also guarantees sealing despite pressure and temperature differentials that may be significant between the hermetic enclosure and the cryogenic box. In addition, the use of a bellows ensures good thermal insulation between the hermetic enclosure and the cryogenic box.

[0047] Brief description of the drawings

[0048] 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:

[0049] [Fig 1] Figure 1 is a schematic view in longitudinal section of the device according to the invention, the guide tube of the device being straight and the corrugated bellows of the device being subjected to an internal pressure greater than the external pressure.

[0050] [Fig 2] Figure 2 is a schematic longitudinal sectional view of the device according to the invention, the device being a probe for NMR spectroscopy and the translation of the adjustment rod adjusting the tuning capacity of the probe.

[0051] [Fig 3] Figure 3 is a schematic longitudinal sectional view of the device according to the invention, the device being a probe for NMR spectroscopy and the translation of the adjustment rod adjusting the angle of inclination of the stator of the probe.

[0052] [Fig 4] Figure 4 is a schematic longitudinal sectional view of the device according to the invention, the guide tube of the device extending in the shape of an S and the corrugated bellows of the device working with an internal pressure greater than the external pressure.

[0053] [Fig 5] Figure 5 is a schematic longitudinal sectional view of the device according to the invention, the guide tube of the device extending in the shape of an S and the corrugated bellows of the device working with an internal pressure lower than the external pressure. Detailed description

[0054] 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.

[0055] Figure 1 illustrates a device 1 according to the invention, comprising a hermetic enclosure 2 and a cryogenic box 3 housed in the hermetic enclosure 2.

[0056] The internal medium 4 of the hermetic enclosure 2 is at a pressure less than or equal to 10' 5 mbar.

[0057] The cryogenic box 3 is sealed, pressurized, for example up to 4 bar, and at cryogenic temperature, for example around or below 100 K. This arrangement of the cryogenic box 3 in the hermetic enclosure 2 guarantees excellent thermal insulation.

[0058] Thermal insulating supports 5 support the cryogenic box 3 while limiting heat conduction.

[0059] The hermetic enclosure 2 comprises a sheath 6 opening on the one hand onto the external environment 7 of the hermetic enclosure 2 and on the other hand onto the internal environment 4 of the hermetic enclosure 2. The sheath 6 comprises a stuffing box 8 and a guide sleeve 9.

[0060] A transmission bar 10 is inserted into the sheath 6 with the stuffing box 8 in compression around the transmission bar 10 so as to ensure the sealing of the sheath 6. The transmission bar 10 is mounted in translation along the central axis of the sheath.

[0061] The stuffing box 8 comprises three clamping rings 11 and two sealing gaskets 12 housed in a hollow cylindrical structure 13. The internal diameter of the hollow cylindrical structure 13 is sufficient to allow the transmission bar 10 to pass through. The clamping rings 11 are tightened so as to compress the sealing gaskets 12 around the transmission bar and thereby seal the sleeve 6. The compression of the sealing gaskets 12 reduces their internal diameter which can thus be less than the external diameter of the transmission bar 10. The compression of the sealing gaskets 12 can be adjusted by a screw plunger.

[0062] The stuffing box 8 also includes an annular chamber 14 around the clamping rings 11 and the sealing gaskets 12. The annular chamber 14 is pumped under vacuum to a pressure, typically less than or equal to 1.10' 3 mbar. Thus, the volume between the clamping rings 11 and the seals 12 and the volume between the two seals 12 is at a pressure less than or equal to 1.10' 3 mbar. Such pressure makes it possible to guarantee better compression of the sealing gaskets 12 and better sealing of the closure of the sheath 6.

[0063] Furthermore, the transmission bar 10 is locked in rotation on itself in the guide sleeve 9. To do this, the transmission bar 10 may comprise a pin 15 arranged in a slot hollowed out in the guide sleeve 9.

[0064] The device 1 comprises a wheel 16 arranged outside the hermetic enclosure 2 and secured to a nut 17 into which the transmission bar 10 is screwed, forming a screw-nut system. This system 10, 17, similar to a screw jack, makes it possible to transform the rotation of the wheel 16 into a translation of the transmission bar 10 along the central axis of the sheath. The rotation of the wheel 16 can be done manually or in a motorized manner. Ball bearings 18 are arranged on either side of the nut 17 so as to facilitate the rotation of the wheel 16.

[0065] The screw-nut system 10, 17 makes it possible to precisely and easily translate the transmission bar 10. Furthermore, such a system guarantees that the bar 10 is kept in position, in the absence of any rotation of the wheel 16.

[0066] The cryogenic box 3 comprises an opening 19 around which is fixed, preferably screwed, a guide tube 20, in particular straight, which extends into the hermetic enclosure 2.

[0067] An annular seal 21 seals the fixing of the guide tube 20 around the opening 19. The annular seal 21 may be an elastic seal with a C-shaped section. Alternatively, the annular seal 21 may be formed by a metal wire, for example indium. Indium is particularly suitable for cryogenic temperatures. The annular seal 21 may be compressed between the guide tube 20 and the wall of the cryogenic box 3 with a compressive force of up to 50 N / mm.

[0068] The device 1 comprises a corrugated bellows 22, one end of which is tightly fixed to the guide tube 20. The other end of the corrugated bellows 22 is tightly fixed around the transmission bar 10 so that the translation of the transmission bar 10 in one direction contracts the corrugated bellows 22 and stretches it in the opposite direction. The corrugated bellows 22 may be hermetically welded to the transmission bar 10 and / or to the guide tube 20. The welds advantageously ensure better sealing for low temperatures, for example less than or equal to 100 K, and withstand high pressure and temperature differentials.

[0069] In the embodiment illustrated in Figure 1, pushing the transmission bar 10 towards the opening 19 contracts the corrugated bellows 22, and, conversely, pulling the transmission bar 10 outwards stretches the corrugated bellows 22.

[0070] The corrugated bellows 22 hermetically closes the opening 19 and ensures the sealing of the cryogenic box 3. The pressure exerted on the inside of the corrugated bellows 22 is equal to the pressure exerted in the cryogenic box 3. The pressure exerted on the outside of the corrugated bellows 22 is equal to the pressure of the internal medium 4 of the hermetic enclosure 2.

[0071] The corrugated bellows 22 is configured to withstand the differential between the pressure exerted on its interior and the pressure exerted on its exterior. In particular, the thickness of the wall of the corrugated bellows 22 may be greater than or equal to 0.1 mm, preferably between 0.05 and 0.012 mm. In addition, such a thickness limits thermal losses by conduction.

[0072] For example, the corrugated bellows 22 has, in the stretched state, a length equal to 80 mm and a diameter equal to 16 mm.

[0073] The device 1 also comprises a conduit 23 around the corrugated bellows 22 and configured to guide the corrugated bellows 22 during its contraction or stretching. The conduit 23 thus prevents the corrugated bellows 22 from buckling.

[0074] The device 1 comprises a cable 24, one of its ends being fixed to the transmission bar 10 and the other of its ends being fixed to an adjustment rod 25.

[0075] The cable 24 is arranged in the corrugated bellows 22 and the guide tube 20. The adjustment rod 25 is arranged in the cryogenic box 3 opposite the opening 19. Thus, the cable 24 exerts traction on the adjustment rod 25 when the transmission bar 10 is pulled towards the outside of the hermetic enclosure 2.

[0076] The device 1 comprises a return spring 26, one end of which is fixed to the cryogenic box 3 and the other end of which extends around and fixed to the adjustment rod 25. The return spring 26 makes it possible to keep the cable 24 under tension when the transmission bar 10 is pushed towards the cryogenic box 3. In fact, this push relaxes the cable 24 and the force of the return spring 26 again tightens the cable 24 and simultaneously pushes the adjustment rod 25.

[0077] The cable 24 and the return spring 26 thus transmit any translation of the transmission bar 10 along the axis of the sheath into a translation of the adjustment rod 25. As will appear later, the translation of the adjustment rod 25 in the cryogenic box 3 makes it possible to precisely position elements contained in the cryogenic box 3.

[0078] The cable 24 is preferably made of a metallic material. Preferably, the cable 24 is multi-stranded, thus it has great flexibility which facilitates its movement in the corrugated bellows 22 and the guide tube 20.

[0079] In order to limit thermal losses by conduction, the cable 24 may have a diameter less than or equal to 1 mm, preferably between 0.8 and 1.2 mm.

[0080] In order to ensure good thermal and electrical insulation, the adjustment rod 25 can be made of epoxy glass.

[0081] Figure 2 illustrates a device 1 according to the invention constituting a probe for NMR spectroscopy.

[0082] In addition to the elements of the device 1 described in relation to FIG. 1, the probe 1 comprises a tuning capacitor 27 arranged in the cryogenic box 3. The tuning capacitor 27 comprises a core 28 mounted to move in translation in an envelope so as to vary the impedance of the tuning capacitor 27.

[0083] The envelope of the tuning capacitor 27 is cylindrical in shape with a length of 60 mm and a diameter of 12 mm.

[0084] The adjustment rod 25 is fixed, at its end opposite the cable 24, to the core 28. Thus, the translation of the adjustment rod 25 drives the core 28 in translation in the envelope of the tuning capacitor 27 and thus adjusts its impedance of the tuning capacitor 27. In other words, with the transmission kinematics described, the impedance of the tuning capacitor 27 can be modified only by turning the wheel 16 on itself.

[0085] For example, the adjustment rod 25 can translate by 0.7 mm per complete turn of the wheel 16 on itself. The probe 1 also comprises a stator 29 in which a rotor 30 is arranged for NMR spectroscopy. The stator 29 comprises a coil 31 connected to the tuning capacitor 27 by an electric current supply 32. The coil 31 is configured to generate a static magnetic field for NMR spectroscopy. The variation of the impedance of the tuning capacitor 27 modifies the static magnetic field generated by the coil 31. It is thus possible to tune the static magnetic field during NMR spectroscopy of a sample contained in the rotor 30 according to the atomic nucleus of the material to be analyzed.

[0086] Figure 3 also illustrates a probe 1 for NMR spectroscopy, according to the invention. The probe 1 differs from the device 1 illustrated in Figure 1 in that it comprises a stepped speed reducer 34, arranged between the wheel 16 and the nut 17.

[0087] The speed reducer 34 transmits the rotation of the wheel 16 into an output rotation with a reduction ratio less than 1 / 15, for example equal to 1 / 19.

[0088] The nut 17 and the transmission bar 10 transform, similarly to a screw jack, the output rotation into a translation of the transmission bar 10 along the axis of the sheath.

[0089] The speed reducer 34 therefore allows precise adjustment of the translation of the transmission bar 10 and, thereby, of the adjustment rod 25.

[0090] For example, with a speed reducer 34, the adjustment rod 25 can translate by 0.037 mm per complete turn of the wheel 16 on itself.

[0091] The probe 1 also comprises a stator 29 intended to receive a rotor 30 for NMR spectroscopy. The stator 29 comprises a coil 31 configured to generate a static magnetic field for NMR spectroscopy.

[0092] The stator 29 is mounted to rotate about its transverse axis 33. The adjustment rod 25 is fixed, at its end opposite the cable 24, to the stator 29 so that the translation of the adjustment rod 25 drives the stator 29 to rotate about its transverse axis 33. Thus, with the transmission kinematics described, the angle of inclination θ of the stator 29 can be adjusted by rotating the wheel 16 on itself. The angle of inclination θ of the stator 29 corresponds to the angle between the longitudinal axis in which the stator 29 extends and the static magnetic field for NMR spectroscopy. For example, a complete turn of the wheel 16 on itself corresponds to a rotation of 00°04'42'' of the angle of inclination 9 of the stator 29. The probe 1 is therefore suitable for precisely adjusting the angle of inclination 9 of the stator 29 to 54°44'.

[0093] Figure 4 illustrates a device 1 according to the invention. It differs from that illustrated in Figure 2 in that the guide tube 29 is not straight but extends in the shape of an S, which makes it possible to reduce its bulk. In addition, this misaligns the translations of the transmission bar 10 and the adjustment rod 25, which reduces the space required for said translations.

[0094] Figure 5 illustrates a device 1 according to the invention. It differs from that illustrated in Figure 4 in that it is not the guide tube 20 which is fixed around the opening 19 but the corrugated bellows 22, one of the ends of which is fixed around the opening 19 while extending into the cryogenic box 3. A flange 28 arranged at the end of the corrugated bellows 22 crushes the annular seal 21 so as to ensure the sealing of the fixing of the corrugated bellows 22 around the opening 19. The other end of the corrugated bellows 22 is fixed, preferably welded, to the transmission bar 10 and to the guide tube 20. The guide tube 20 extends in the shape of an S in the cryogenic box 3.

[0095] Thus, the corrugated bellows 22 hermetically closes the opening 19 and ensures the sealing of the cryogenic box 3. The pressure exerted on the inside of the corrugated bellows 22 is equal to the pressure of the internal medium 4 of the hermetic enclosure 2. The pressure exerted on the outside of the corrugated bellows 22 is equal to the pressure exerted in the cryogenic box 3.

[0096] The embodiment of Figure 5 is advantageous when the pressure of the internal medium 4 is lower than the pressure exerted in the cryogenic box 3. Indeed, the corrugated bellows 22 is more resistant and less mechanically stressed when the pressure exerted on its exterior is greater than or equal to the pressure exerted on its interior. Thus, the thickness of the wall of the corrugated bellows 22 may be less than that of the embodiments of Figures 1 and 2, for example between 0.05 and 0.08 mm. The corrugated bellows 22 is then more flexible, which facilitates its contraction and its stretching, and, consequently, the translation of the transmission bar 10.

[0097] Other variants and improvements may be envisaged without departing from the scope of the invention. In particular, the device 1 may comprise a plurality of sheaths 6, as many openings 19, and for each sheath 6 and opening 19, a transmission bar and an adjustment rod connected together so as to translate an element contained in the cryogenic box 3. For example, in the case where the device 1 is a probe for NMR spectroscopy, the device 1 may comprise six adjustment rods each configured to adjust one of the tuning capacities 27 of the probe, and a seventh adjustment rod configured to adjust the angle of inclination 9 of the stator 29 of the probe.

[0098] References cited

[0099] [1]: Yoh Matsuki and Toshimichi Fujiwara, “Cryogenic Platforms and Optimized DNP sensitivity”, eMagRes, 2018, Vol 7: 9-24,

Claims

Claims 1. Device (1), comprising: - a hermetic enclosure (2) comprising at least one sheath (6) opening to the outside (7) of the hermetic enclosure, - a cryogenic box (3) arranged in the hermetic enclosure and comprising at least one opening (19) opening into the hermetic enclosure, - at least one adjustment rod (25) mounted in translation in the cryogenic box so as to adjust the positioning of an element housed in the cryogenic box, - at least one transmission bar (10) passing in a sealed manner through the sheath, the transmission bar being movable in translation along the longitudinal axis of the sheath by an element arranged outside the sheath, the transmission bar being connected to the adjustment rod so that the translation of the bar is transmitted to the rod and vice versa, - at least one corrugated bellows (22) fixed in a sealed manner to the transmission bar and around the opening so as to hermetically close the cryogenic box.

2. Device according to claim 1, the sheath comprising a stuffing box (8) configured to be compressed with sealing onto the transmission bar while leaving it movable in translation.

3. Device according to claim 2, the stuffing box comprising at least one, preferably at least two, sealing gasket(s) (12), and clamping rings (11), the clamping ring(s) being configured to compress the sealing gasket(s) onto the transmission bar, preferably the stuffing box comprising an annular chamber (14) in which the sealing gasket(s) is(are) partly housed, the annular chamber being at a pressure less than or equal to 1.10' 3 mbar.

4. Device according to one of the preceding claims, the sheath comprising a guide sleeve (9) configured to guide the transmission bar in translation and at least one locking means to lock the transmission bar in rotation.

5. Device according to one of the preceding claims, comprising a wheel (16) accessible from outside the sheath and a transformation mechanism configured to transform the rotation of the wheel into a translation of the transmission bar along the axis of the sheath, preferably the transmission bar comprising a threaded portion and the transformation mechanism comprises a nut (17) or a toothed wheel to form, with the threaded portion, a screw jack, respectively a rack and pinion system, preferably the device comprising ball bearings (18) configured to facilitate the rotation of the wheel.

6. Device according to one of the preceding claims, the corrugated bellows being metallic.

7. Device according to one of the preceding claims, the corrugated bellows being hermetically welded to the transmission bar.

8. Device according to one of the preceding claims, comprising an annular seal (21) ensuring the sealing of the fixing of the corrugated bellows around the opening.

9. Device according to one of the preceding claims, comprising a transmission cable (24) one of its ends being fixed to the transmission bar and the other of its ends being fixed to the adjustment rod, preferably the device comprising a guide tube (20) configured to guide the sliding of the transmission cable, preferably the guide tube extending along a curve, preferably in the shape of an S.

10. Device according to the preceding claim, comprising a return spring (26) mounted around and fixed to the adjustment rod so as to cause it to translate towards the inside of the cryogenic box, when the cable is relaxed by a translation of the transmission bar towards the inside of the cryogenic box.

11. Device according to one of the preceding claims, comprising at least one tuning capacity (27) arranged in the cryogenic box, the tuning capacity comprising a core (28) movable in translation to vary the tuning capacity, the end of the adjustment rod opposite that connected to the transmission bar being connected, preferably fixed, to the core.

12. Device according to one of the preceding claims, comprising a stator (29) arranged in the cryogenic box and mounted to rotate about a transverse axis (33), the adjustment rod being connected, preferably fixed, to the stator so that the translation of the adjustment rod sets the stator in rotation about the transverse axis.

13. Device according to one of the preceding claims, the hermetic enclosure being at a pressure lower than 10' 5 mbar.

14. Device according to one of the preceding claims, the cryogenic box being at a pressure between 1000 and 4000 mbar and / or at a temperature below 30 K.

15. Device according to one of the preceding claims, constituting a probe of a nuclear magnetic resonance (NMR) spectrometer, preferably the probe comprising a stator and at least one adjustment rod whose translation modifies the inclination of the stator, and / or at least one adjustment rod whose translation modifies a tuning capacity of the probe.

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