NMR probe

1. An NMR probe for use with a sample tube which can be introduced into and withdrawn from the probe while the probe is kept mounted in a magnetic field generator, said NMR probe comprising:

a sample tube insertion port through which the sample tube is inserted into and withdrawn from the NMR probe;

a sample tube support that supports the sample tube during NMR measurements;

a tubular sample tube passage connecting together the sample tube insertion port and the sample tube support and permitting the sample tube to be conveyed therebetween;

a gas stream generator for producing a gas stream in the sample tube passage to convey the sample tube between the sample tube support and the sample tube insertion port, the gas stream generator being mounted at an intermediate position in the sample tube passage,

wherein said gas stream generator has means for ejecting gas into said tubular passage directed toward the sample tube insertion port from a gas port at an intermediate position in the sample tube passage and having an inside diameter smaller than the inside diameter of the sample tube passage.

2. An NMR probe as set forth in claim 1 , wherein

said magnetic field generator is a superconducting magnet having an access space in the form of an elongated slot,

said sample tube support is a MAS device adapted for solid-state NMR measurements,

a direction converter for converting the direction of transport of the sample tube is mounted at a non-end position in the sample tube passage, and

said gas stream generator is mounted at an intermediate position in the sample tube passage between the sample tube insertion port and the direction converter and located physically closer to the sample tube support than the midway point of the sample tube passage.

3. An NMR probe as set forth in claim 2 , wherein a gas port having an inside diameter smaller than the inside diameter of said sample tube passage is formed in said direction converter to eject gas toward the sample tube in response to operation of the gas stream generator such that the sample tube is urged to change its direction.

4. An NMR probe as set forth in claim 3 , wherein said gas port defines a gas ejection angle lying in a range of 10° to 30° relative to the direction of the axis of a portion of the sample tube passage defining the gas port, and wherein the gas port has a diameter lying in a range of 1/10 to ⅓ of the inside diameter of the sample tube passage.

5. An NMR probe as set forth in any one of claims 1 to 3 , wherein pressure gauges for detecting the pressure inside the sample tube passage are connected to said sample tube passage at positions close to ends of the gas stream generator which face the sample tube insertion port and the sample tube support, respectively.

6. An NMR probe as set forth in any one of claims 1 to 3 , wherein a gas port permitting the gas to escape to the outside from inside the sample tube passage is formed in the sample passage at a position close to an end of the gas stream generator which faces the sample tube insertion port, and wherein there is further provided a valve for adjusting the flow rate of the escaping gas.

7. An NMR probe as set forth in any one of claims 1 to 3 , wherein said sample tube support has a reflection type optical detection system for detecting the angular position of the sample tube, and wherein the optical detection system is located such that the sample tube is interposed in the optical detection system on an extension to the direction along which light is emitted from the optical detection system to detect the presence or absence of the sample tube in the sample tube support.