NMR probe head with heated housing
An NMR probe head for investigating a temperature-sensitive test object in a volume under investigation with at least one RF receiver coil which is cooled to cryogenic temperatures during operation, and is surrounded by a housing, wherein at least one heatable separating wall is provided between the RF receiver coil and the test object, is characterized in that the separating wall is produced from a material having excellent heat conducting properties, wherein the separating wall is coupled in a heat conducting fashion to at least one heating element at a separation from the volume under investigation via at least one contact location. The inventive NMR probe head permits disposition of the RF receiver coil in close proximity to the test object to be measured without inadvertently cooling it.
1. An NMR probe head for investigating a temperature-sensitive test object in a volume under investigation, the probe head comprising:
a housing;
at least one RF receiver coil disposed within said housing, said receiver coil being cooled to a cryogenic temperature during operation of the probe head;
a separating wall disposed between said RF receiver coil and the test object, said separating wall comprising a material having excellent heat conduction properties;
a heating element disposed at a separation from the volume under investigation; and
means for thermally coupling said separating wall to said heating element.
2. The NMR probe head of claim 1 , wherein said housing is an evacuated housing.
3. The NMR probe head of claim 1 , wherein said separating wall is integral with said housing.
4. The NMR probe head of claim 1 , wherein said separating wall has a thickness of less than 1 mm or of approximately ½ mm.
5. The NMR probe head of claim 1 , wherein an electrical conductivity of a material of said separating wall at an operating temperature thereof is less than 10 −3 S/m, less than 10 −5 S/m, or less than 10 −8 S/m.
6. The NMR probe head of claim 1 , wherein a thermal conductivity of a material of said separating wall at an operating temperature thereof is more than 15 WK −1 m −1 or more than 80 WK −1 m −1 .
7. The NMR probe head of claim 1 , wherein material of said separating wall comprises aluminium nitride (AlN), beryllium oxide (BeO), aluminium oxide (Al 2 O 3 ), boron nitride (BN), or magnesium oxide (MgO).
8. The NMR probe head of claim 1 , wherein a separation between said RF receiver coil and an accessible volume under investigation is <2 mm or ≦1 mm.
9. The NMR probe head of claim 1 , wherein said housing is produced from a ceramic material containing aluminium nitride or from a machineable ceramic material of AlN with BN.
10. The NMR probe head of claim 9 , wherein said housing is produced in one piece.
11. The NMR probe head of claim 1 , wherein said thermal coupling means is electrically heated or heated using warm fluids.
12. The NMR probe head of claim 1 , wherein a cryogenic temperature of said RF receiver coil is less than 100K or less than 40K.
13. The NMR probe head of claim 1 , wherein said RF receiver coil is cooled by a refrigerator or by cooling means having a heat-transmitting coolant.
14. The NMR probe head of claim 1 , wherein the probe head is an MRI probe head for imaging.
15. The NMR probe head of claim 1 , wherein investigated nuclei comprise protons.
16. The NMR probe head of claim 1 , wherein an operating frequency of said at least one RF receiver coil is matched to a resonance frequency of investigated nuclei at an operating magnetic field strength of at least 4.6 T.
17. The NMR probe head of claim 1 , wherein investigated nuclei comprise 2 H, 3 He, 129 Xe, 13 C, 17 O, 19 F, 23 Na, or 31 P nuclei.
18. The NMR probe head of claim 1 , wherein said separating wall is provided with a thermometer for measuring a temperature thereof.
19. A method for operating the NMR probe head of claim 1 , wherein a temperature of said housing is measured and preferably adjusted.
20. The method of claim 19 , wherein the temperature of said housing is adjusted to a temperature which is well suited for the temperature-sensitive test object.
21. The method of claim 20 , wherein the temperature-sensitive test object is a small animal, a mouse, or a rat.
22. The method of claim 19 , wherein the temperature of said housing is measured using at least one electrical temperature sensor.