NMR probe head comprising a releasable HF seal

1. An NMR probe head comprising: one or more HF coils arranged around a vertical (z) axis of symmetry and an HF network, surrounded by an apparatus for shielding from external HF radiation comprising:

an electrically conductive shielding tube that is arranged along the (z) axis and can be moved around the HF coils and the HF network in a z-direction relative to the (z) axis towards a base disc,

a shielding disc at an axial distance from the base disc, and

a tensible HF seal arranged between the shielding disc and the shielding tube, when the shielding tube is in a mounted state

wherein, in a first mounting state, the tensible HF seal is geometrically configured such that the shielding tube can slide over the shielding disc in an unbraced and force-free manner; and

wherein, in a second mounting state, the tensible HF seal is mechanically braced between the shielding disc and the shielding tube such that an electrically conductive connection to the shielding tube is ensured over the periphery of the shielding disc.

2. The NMR probe head according to claim 1 , wherein the shielding tube is prism-shaped.

3. The NMR probe head according to claim 1 , wherein the shielding tube is formed in at least two parts in the z-direction.

4. The NMR probe head according to claim 3 , wherein the shielding tube comprises a first sub-portion that surrounds an analysis sample below the shielding disc when the NMR probe head is in an operating state.

5. The NMR probe head according to claim 4 , wherein the first sub-portion of the shielding tube is configured to have a standard length of between 100 mm and 500 mm, and wherein a second sub-portion of the shielding tube is configured to have a selectable, arbitrary length in the z-direction.

6. The NMR probe head according to claim 5 , wherein the first sub-portion and the second sub-portion of the shielding tube are integrally interconnected before being mounted in the NMR probe head.

7. The NMR probe head according to claim 4 , wherein at least the first sub-portion of the shielding tube has an electrical conductivity of σ≥30*10 6 Siemens/meter.

8. The NMR probe head according to claim 1 , wherein the tensible HF seal comprises a spring element which presses against an edge portion of the shielding disc when in the second mounting state.

9. The NMR probe head according to claim 8 , wherein the edge portion of the shielding disc is conical.

10. The NMR probe head according to claim 8 , further comprising a clamping ring arranged radially between the shielding tube and the shielding disc.

11. The NMR probe head according to claim 9 , further comprising a clamping ring arranged radially between the shielding tube and the shielding disc, wherein the spring element comprises a plurality of contact fingers which are pressed by the clamping ring over a cone between the shielding disc and the shielding tube to establish electrical contact between the shielding tube and the shielding disc.

12. The NMR probe head according to claim 10 , wherein the spring element comprises a plurality of contact fingers which are pressed by the clamping ring over a cone between the shielding disc and the shielding tube to establish electrical contact between the shielding tube and the shielding disc.

13. The NMR probe head according to claim 12 , wherein the edge portion of the shielding disc is conical.

14. The NMR probe head according to claim 13 , wherein the conical edge portion of the shielding disc is configured to prevent self-locking of the contact fingers when the HF seal is released, wherein the cone angle is ≥15°.

15. The NMR probe head according to claim 1 , further comprising a chuck key configured to clamp or release the tensible HF seal.

16. The NMR probe head according to claim 15 , wherein the chuck key to clamp or release the tensible HF seal is temporarily attached at the side or from below.

17. The NMR probe head according to claim 1 , wherein the shielding tube is formed in multiple parts in the z-direction.

18. The NMR probe head according to claim 5 , wherein the shielding tube is configured to be in the shape of a cylinder.

19. The NMR probe head according to claim 3 , wherein the first sub-portion and second sub-portion of the shielding tube are adhesively bonded or welded before being mounted in the NMR probe head.

20. The NMR probe head according to claim 4 , wherein the shielding tube further comprises a second sub-portion configured to have a selectable, arbitrary length in the z-direction, and wherein the first sub-portion and the second sub-portion of the shielding tube are integrally interconnected before being mounted in the NMR probe head.

21. A NMR measurement assembly comprising an NMR probe head, an NMR magnet system, a shim system, a turbine and a device for transporting a sample tube from outside the NMR magnet system into a measuring position of the sample tube in the NMR probe head, wherein the NMR probe head comprises:

one or more HF coils arranged around a vertical (z) axis of symmetry and an HF network, surrounded by an apparatus for shielding from external HF radiation, comprising an electrically conductive shielding tube that is arranged along the (z) axis and can be moved around the HF coils and the HF network in a z-direction relative to the (z) axis towards a base disc,

wherein a shielding disc is provided at an axial distance from the base disc;

wherein a tensible HF seal is arranged between the shielding disc and the shielding tube, when the tube is in a mounted state;

wherein, in a first mounting state, the tensible HF seal is geometrically configured such that the shielding tube can slide over the shielding disc in an unbraced and force-free manner; and

wherein, in a second mounting state, the HF seal is mechanically braced between the shielding disc and the shielding tube such that an electrically conductive connection to the shielding tube is ensured over the periphery of the shielding disc.