JP4851265B2 - Cooled NMR probe head and NMR analyzer equipped with the same - Google Patents

Description

  The present invention relates to a cooled NMR probe head for detecting an NMR signal in an NMR (Nuclear Magnetic Resonance) analyzer used for chemical analysis or the like.

  As means for detecting an NMR signal, an NMR probe head having an NMR antenna coil is known. The NMR antenna coil generally has a cylindrical shape, irradiates a sample inserted inside with a radio frequency (RF) pulse, and outputs a magnetic resonance signal emitted from the sample after a lapse of a certain time from the irradiation. Pick up. However, since the NMR signal detected in this way is weak, it is required to improve its detection sensitivity.

  As a method for this purpose, a technique for reducing thermal noise by cooling the antenna coil to a cryogenic temperature using a refrigerant such as helium has been developed. Since the S / N ratio (SNR) of the NMR signal is inversely proportional to the square root of the value including the product of the temperature Tc and the resistance value Rc of the antenna coil as shown in the following equation (1), the antenna coil is cooled. This significantly improves the detection sensitivity of the NMR signal.

SNR∝1 / √ [T _c R _c + T _s R _s + T _a (R _c + R _s ) ² ] (1)
Here, Ts is the temperature of the sample to be measured, Rs is the effective resistance value of the sample, and Ta is the temperature of the preamplifier for amplifying the signal.

As means for cooling the antenna coil, the following Patent Document 1 discloses a probe including a cylindrical heat conductor that supports the antenna coil and a heat exchanger into which helium gas cooled by a GM refrigerator is introduced. A head is disclosed. Specifically, FIG. 2 of Patent Document 1 shows a structure in which the lower end of the heat conductor is coupled to the upper surface of the heat exchanger in an upright state.
US Patent Application Publication No. 2004/0004478 and drawings

  As apparent from the equation (1), it is desirable that the temperature of the antenna coil is as low as possible in order to improve the S / N ratio of the NMR signal. However, the conventional cooling type NMR probe head has a limit in cooling the antenna coil.

  In view of such circumstances, the present invention provides a cooled NMR probe head capable of effectively reducing the temperature of an antenna coil and increasing the detection sensitivity of an NMR signal, and an NMR analyzer including the same. It is aimed.

  The present inventor has conceived that a feed line for transmitting high-frequency power to an antenna coil works as a factor that inhibits cooling of the antenna coil.

  That is, since the feed line has a small cross-sectional area and a large electric resistance compared to the antenna coil, a part of the transmitted power is consumed in the feed line as Joule heat, and the temperature of the feed line The temperature of the antenna coil is also increased by transmitting the feeder line. On the other hand, the specific heat of the metal (for example, copper or aluminum) forming the antenna coil is extremely small under extremely low temperature conditions during operation, and therefore a slight Joule heat significantly increases the temperature of the antenna coil. In addition, the electrical resistance value of copper or aluminum, which is the material of the antenna coil, increases with the temperature of the material, and this increase in electrical resistance promotes the temperature rise due to Joule heat of the feeder line.

Therefore, in order to solve the above-mentioned problems, the present invention is provided with an antenna coil, and is connected to the antenna coil in a cooled NMR probe head that detects an NMR signal in a state where the antenna coil is cooled. And a cooling member thermally connected to the antenna coil so as to cool the antenna coil, and at least a part of the feeder line is connected to the cooling member. The cooling member includes a refrigerant container having an outer wall that forms a cooling space through which the refrigerant can flow, and the power supply line is thermally connected to the outer wall of the refrigerant container . A cooled NMR probe head is provided.

  According to the present invention, since at least a part of the feed line and the cooling member are thermally connected, not only the antenna coil but also the feed line connected to the antenna coil is used for cooling. It can be cooled by the member.

  Therefore, even under extremely low temperature operating conditions where the specific heat of the metal forming the antenna coil is significantly reduced, the amount of heat transferred from the feeder line to the antenna coil can be reduced by suppressing the temperature rise of the feeder line. Therefore, the antenna coil can be effectively cooled correspondingly.

  Therefore, according to the present invention, it is possible to effectively reduce the temperature of the antenna coil by suppressing the temperature rise of the feeder line, and increase the detection sensitivity of the NMR signal.

Furthermore, in the present invention, the cooling member includes a refrigerant container having an outer wall that forms a cooling space through which the refrigerant can flow, and the power supply line is thermally connected to the outer wall of the refrigerant container. .

This ensures that by the refrigerant inside the cooling space the feed line to the outer wall of the refrigerant vessel is cooled thermally connected by circulation, can effectively reduce the temperature of the antenna coil.

  A thermal connection mode between the refrigerant container and the power supply line is not particularly limited, but the refrigerant container has a through-hole that penetrates the outer wall and does not communicate with the cooling space. It is preferable that at least a part of the electric wire is disposed through the through hole and is thermally connected to the inner surface of the through hole.

  In this case, since the power supply line can be arranged through the through hole formed in the refrigerant container, the power supply line is thermally connected to the outer surface of the refrigerant container so as to avoid the refrigerant container; In comparison, it is possible to reduce the space required for the wiring of the power supply line and to form a compact probe head as a whole.

  Further, since the power supply line is arranged in the through hole, heat exchange between the power supply line and the refrigerant container can be performed with a relatively large area between the outer peripheral surface of the power supply line and the inner peripheral surface of the through hole. Can be done.

  When the power supply line is arranged in the through hole of the refrigerant container as described above, the distance between the antenna coil and the portion close to the antenna coil in the power supply line and the refrigerant container is closer. As a result, the shape of the refrigerant container may be complicated due to restrictions on the layout of the antenna coil, but the cooling member is the power supply line arranged between the refrigerant container and the antenna coil. A covering member that surrounds at least a part of the outer peripheral surface of the portion that is not thermally connected to the refrigerant container; and the covering member is at least partially thermally connected to the outer wall of the refrigerant container. By adopting the configuration, the power supply line can be cooled by a covering member separate from the refrigerant container, so that the power supply line can be cooled while maintaining the shape of the refrigerant container. It is possible to expand the circumference.

  In the cooling type NMR probe head, it is preferable that the power supply line is thermally connected to the cooling member via an insulating member capable of electrically insulating the power supply line and the cooling member. .

  According to this configuration, even if the cooling member is composed of a conductive member, it is possible to prevent a short circuit, so that there is almost no influence on the detection of the NMR signal, and the power supply line and the cooling member are not affected. The member can be thermally connected.

  Here, at least a portion of the insulating member interposed between the power supply line and the cooling member is made of at least one material selected from single crystal sapphire, zirconia, quartz, and diamond. Particularly preferred.

  In this way, since a material with particularly high thermal conductivity can be interposed between the power supply line and the cooling member, the cooling efficiency of the power supply line can be further improved.

  The present invention also provides an NMR analyzer comprising the above-described cooled NMR probe head, a superconducting coil provided around the cooled NMR probe head, and a low-temperature container that accommodates the superconducting coil. I will provide a.

  According to the present invention, it is possible to effectively reduce the temperature of the antenna coil by suppressing the temperature rise of the feeder line, and increase the detection sensitivity of the NMR signal. For this reason, the NMR analyzer which was excellent in the detection sensitivity can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of an NMR (nuclear magnetic resonance) analyzer.

  This apparatus includes a cryogenic container 1 that contains a refrigerant such as liquid helium, a superconducting coil 2 that is immersed in the refrigerant, and a cooled NMR probe head 3.

  The superconducting coil 2 is composed of a cylindrical winding frame centered on the vertical axis and a superconducting wire wound around the superconducting coil 2, and the cryocontainer 1 also covers the superconducting coil 2 from the inside in the radial direction. It has a donut shape. That is, an inner space 4 extending in the vertical direction is formed in the center of the cryogenic container 1. The cooled NMR probe head 3 is inserted into the inner space 4 from below.

  The cooled NMR probe head 3 has an electrode portion 5 and a cylindrical probe body 6 connected to the electrode portion 5, and the probe body 6 is inserted into the inner space 4 from below.

  FIG. 2 shows the internal structure of the upper part of the probe body. FIG. 3 is an enlarged perspective view showing a main part of FIG. FIG. 4 is an enlarged cross-sectional view showing a main part of FIG.

  The probe body 6 includes a sample insertion tube 7 positioned on the central axis J1 (see FIG. 4), a substantially cylindrical antenna coil 8 surrounding the sample insertion tube 7, and the antenna coil 8 and a resonance circuit (not shown). Are provided with a feeding line 9 and a feeding line 10 for transmitting high-frequency power between them, a cooling member 11 for cooling the antenna coil 8, and an outer cylinder 12.

  The sample insertion tube 7 is made of quartz or the like, and the inside space 14 is kept at normal temperature and pressure. A sample tube 15 is inserted into the space 14 from above. The sample tube 15 accommodates a sample 16 to be subjected to NMR analysis.

  The antenna coil 8 has a substantially cylindrical peripheral wall, which is formed by rolling a metal foil plate as shown in FIG. The specific shape of the antenna coil 8 is not limited, and is appropriately set according to the frequency of the RF pulse used for NMR detection and other specifications. The feed lines 9 and 10 are electrically connected to the feed point 9a and the feed point 10a below the antenna coil 8, respectively.

  The cooling member 11 includes a coil support member 17 for supporting the antenna coil 8, a refrigerant container 18 capable of circulating a refrigerant such as helium gas, and a refrigerant introduction for introducing the refrigerant into the refrigerant container 18. A pipe 19 and a refrigerant discharge pipe 20 for extracting the refrigerant from the refrigerant container 18 are provided.

  The cooling member 11 cools the antenna coil 8 supported by the coil support member 17 by cooling the coil support member 17 with the refrigerant container 18, and each supply unit electrically connected to the antenna coil 8. The electric wires 9 and 10 can also be cooled by the refrigerant container 18. Details thereof will be described later.

  The outer cylinder 12 is disposed so as to surround the coil support member 17 and the refrigerant container 18 around the central axis J1 of the probe body 6. The outer cylinder 12 has an upper cylinder part 28 provided in a height region surrounding the coil support member 17 and the refrigerant container 18, and a lower cylinder part 29 below the upper cylinder part 28. For example, the lower cylinder portion 29 is made of a metal material such as an aluminum alloy or stainless steel, while the upper cylinder portion 28 is made of a nonmetal material such as a synthetic resin. A ceiling wall 30 connected to the upper end of the sample insertion tube 7 extends from the upper end of the upper cylindrical portion 28 while covering the antenna coil 8 and the coil support member 17 from above, and a space S2 below the ceiling wall 30 is formed. Isolated from outside. In this space S2, a vacuum is formed by a pump (not shown). That is, the antenna coil 8 and the like are accommodated in the vacuum space S2.

  A part of the height region including the antenna coil 8 in the upper cylindrical portion 28 is configured by the PFG coil 31. The PFG coil 31 is for applying a pulsed gradient magnetic field to the sample 16 in the sample tube 15, and is not essential in the present invention. The PFG coil 31 can be molded together with the resin-made upper cylindrical portion 28.

  Next, a specific structure of the cooling member 11 will be described with reference to FIGS.

  The coil support member 17 has a cylindrical shape and is arranged coaxially with the central axis J1 of the probe body 6. The upper portion of the coil support member 17 supports the antenna coil 8. Specifically, the inner peripheral surface of the antenna coil 8 is joined to the upper outer peripheral surface of the coil support member 17.

  The coil support member 17 is made of an insulating material that is transparent to electromagnetic waves. This is to prevent the presence of the coil support member 17 from affecting the detection of the NMR signal by the antenna coil 8. The material of the coil support member 17 is preferably further excellent in thermal conductivity. Specifically, single crystal sapphire, zirconia, quartz and diamond are preferable examples. In particular, single crystal sapphire has excellent thermal conductivity in a low temperature region, and greatly contributes to effective cooling of the antenna coil 8. Incidentally, the thermal conductivity of single crystal sapphire in the vicinity of 4K is 150 [W / m / K].

  The refrigerant container 18 is formed of a metal material such as copper together with the refrigerant introduction pipe 19 and the refrigerant discharge pipe 20. The refrigerant container 18 has an outer wall that forms a cooling space S <b> 1 through which the refrigerant can flow. The outer wall forms a hollow container that has a donut shape so as to surround the sample insertion tube 7.

  Specifically, the outer wall integrally includes an outer peripheral wall 21a, an inner peripheral wall 21b, an upper lid 21c, and a lower lid 21d. The outer peripheral wall 21a is disposed on the radially outer side of the cooling space S1 around the central axis J1 of the probe body 6. The inner peripheral wall 21b is disposed on the radially inner side of the cooling space S1 around the central axis J1. The upper lid 21c and the lower lid 21d are arranged so as to sandwich the outer peripheral wall 21a and the inner peripheral wall 21b vertically.

  The upper lid 21c is integrally provided with a connecting cylinder 22 standing on its upper surface. The connecting cylinder 22 and the coil supporting member 17 are connected in a state where the lower end portion of the coil supporting member 17 is inserted inside the connecting cylinder 22.

  Specifically, a silver alloy brazing agent is filled between the inner side surface of the connecting tube 22 and the outer surface of the coil support member 17, and the connecting tube 22 and the coil support member 17 are heated by the brazing agent. Connected. Therefore, the antenna coil 8 is thermally connected to the refrigerant container 18 via the brazing agent and the coil support member 17.

  The refrigerant container 18 includes eight through holes 23 that penetrate the outer peripheral wall 21a in the vertical direction. That is, these through holes 23 are formed in the vertical direction in a state where they do not communicate with the cooling space S1.

  Each of the power supply lines 9 and 10 is disposed through two through holes 23 a and 23 b of the through holes 23. The outer side surfaces of the feeder lines 9 and 10 and the inner side surfaces of the through holes 23a and 23b are thermally connected. Specifically, an insulating member 24 and an insulating member 25 are provided between the outer side surfaces of the power supply lines 9 and 10 and the inner side surfaces of the through holes 23a and 23b, respectively. The outer surfaces of the power supply lines 9 and 10 and the inner surfaces of the through holes 23a and 23b are thermally connected via the insulating members 24 and 25. Therefore, when the refrigerant flows through the refrigerant container 18, heat exchange is performed between the refrigerant container 18 and the power supply lines 9 and 10 via the insulating members 24 and 25, and the power supply lines 9 and 10 are cooled. Is done.

  The insulating members 24 and 25 are each formed of an insulating material. This is to prevent the power supply lines 9 and 10 from being short-circuited via the refrigerant container 18. Furthermore, the material of the insulating members 24 and 25 is preferably excellent in thermal conductivity. Specifically, single crystal sapphire, zirconia, quartz and diamond are preferable examples. In particular, since single crystal sapphire is excellent in thermal conductivity in a low temperature region as described above, it greatly contributes to effective heat exchange between the feeders 9 and 10 and the refrigerant container 18.

  Here, when sapphire is employed as the insulating members 24 and 25, the inner side surfaces of the through holes 23a and 23b and the outer side surfaces of the feeder lines 9 and 10 are used in order to make the thermal connection state stronger. And a silver alloy brazing agent may be further interposed between the insulating members 24 and 25. That is, in order to form such a connection structure, first, a brazing agent layer is formed on the inner side surfaces of the through holes 23a and 23b and the outer side surfaces of the power supply lines 9 and 10, respectively, and these through holes 23a and 23b are formed. The feeder lines 9 and 10 are inserted into the inside. Next, a temporary assembly is formed by filling the insulating members 24 and 25 between the inner side surfaces of the through holes 23a and 23b and the outer side surfaces of the power supply lines 9 and 10 (between the layers of the respective brazing agents). . Then, the temporary assembly is heated in a vacuum furnace to dissolve the brazing agent, and when cooled, the inner members of the insulating members 24 and 25 and the through holes 23a and 23b and the feeder lines 9 and 10 are cooled. It is possible to establish a strong connection state filled with the brazing agent between the outer surfaces of the two.

  4 illustrates the configuration in which the cylindrical insulating members 24 and 25 are filled in the entire range of the feeders 9 and 10 disposed in the through holes 23a and 23b, as shown in FIG. In addition, the disk-shaped insulating members 26 and 27 may be filled intermittently. Even in such a configuration, since the refrigerant container 18 and the power supply lines 9 and 10 are thermally connected via the insulating members 26 and 27, the refrigerant container 18 and the power supply lines are not connected. The heat exchange is performed, and the feeders 9 and 10 are cooled. Further, in this configuration, when the impedance of the high frequency current transmitted to the feeder lines 9 and 10 is greatly disturbed by filling the cylindrical insulating members 24 and 25, the insulating members 26 and 27 are replaced. By adopting, the disturbance of impedance can be reduced.

  As described above, according to the embodiment, since the power supply lines 9 and 10 and the refrigerant container 18 are thermally connected, not only the antenna coil 8 but also the antenna coil 8 is connected. The supplied power lines 9 and 10 can also be cooled by the refrigerant container 18.

  Therefore, even under extremely low temperature operating conditions in which the specific heat of the metal forming the antenna coil 8 is extremely low, the temperature increase of the power supply lines 9 and 10 is suppressed, so that the power is transmitted from the power supply lines 9 and 10 to the antenna coil 8. Therefore, the antenna coil 8 can be effectively cooled by that amount.

  And like the said embodiment, by setting it as the structure which arrange | positions each feeder 9 and 10 through the through-holes 23a and 23b formed in the refrigerant | coolant container 18, the refrigerant | coolant container 18 of the said refrigerant | coolant container 18 is avoided. Compared with the case where the power supply lines 9 and 10 are thermally connected to the outer side surface (the outer peripheral wall 21a), the space required for the wiring of the power supply lines 9 and 10 can be reduced, and the overall size is compact. A cooled NMR probe head 3 can be formed.

  Further, since the power supply lines 9 and 10 are arranged in the through holes 23a and 23b, heat exchange between the power supply lines 9 and 10 and the refrigerant container 18 is performed through the outer peripheral surface of the power supply lines 9 and 10 and the through holes 23a and 23b. It can be performed in a relatively wide area between the inner peripheral surfaces of the holes 23a and 23b.

  In addition, in the said embodiment, although it is set as the structure which arrange | positions each feeder 9 and 10 in the through-holes 23a and 23b of the refrigerant | coolant container 18, as shown to FIG.6 and FIG.7, the groove | channel formed in the refrigerant | coolant container 18 is shown. Each of the feeder lines 9 and 10 may be fitted in 32.

  Specifically, eight grooves 32 are formed around the central axis J <b> 1 of the probe body 6 on the outer surface of the outer peripheral wall 21 a of the refrigerant container 18. These grooves 32 are recessed in the outer peripheral wall 21a so as to open in a direction away from the central axis J1 and to extend in the vertical direction.

  Of the grooves 32, the feeder lines 9 and 10 are fitted in the grooves 32 a and 32 b. An insulating member 33 is provided between the outer peripheral surface of each of the power supply lines 9 and 10 and the inner surface of each of the grooves 32a and 32b.

  The insulating member 33 is made of the same material as the insulating members 24 and 25 (see FIG. 4). Further, the above-described brazing agent can be interposed between each insulating member 33 and the outer peripheral surface of each of the power supply lines 9 and 10 and the inner surface of the grooves 32a and 32b.

  Also in this embodiment, since the refrigerant container 18 and the power supply lines 9 and 10 can be thermally connected, heat exchange is performed between the refrigerant container 18 and the power supply lines 9 and 10. Each feeder 9 and 10 can be cooled.

  Furthermore, in the above-described embodiment, since the feeder lines 9 and 10 can be arranged in a state of being fitted in the grooves 32a and 32b formed in the refrigerant container 18, the outer surface (the outer peripheral wall 21a) of the refrigerant container 18 is left as it is. Compared with the case where the power supply lines 9 and 10 are brought into contact with each other, it is possible to suppress the space required for the wiring of the power supply lines 9 and 10 from being bulky outside the refrigerant container 18 and to be a compact cooling NMR probe head as a whole. 3 can be formed.

  And when it is set as the structure which arrange | positions the feeders 9 and 10 in the through-holes 23a and 23b or groove | channels 32a and 32b of the refrigerant | coolant container 18 like said each embodiment, it is close to the antenna coil 8 among the feeders 9 and 10. If the portion and the refrigerant container 18 are to be thermally connected, the shape of the refrigerant container 18 may be complicated due to restrictions on the layout of the antenna coil 8 as the distance from the antenna coil 8 decreases. Therefore, in addition to the refrigerant container 18, a cooling boot (covering member) 35, 36 as shown in FIG.

  Each of the cooling boots 35 and 36 includes a pair of semi-cylindrical bodies 35a, 35b, 36a and 36b (hereinafter referred to as semi-cylindrical bodies 35a to 36b) each having a shape in which a cylinder is vertically divided by a plane including its axis. ing. These semi-cylindrical bodies 35a to 36b are formed of the same material as the insulating members 24 and 25, respectively.

  Grooves 37a and 37b are formed in the mating surfaces of the semi-cylindrical bodies 35a to 36b, respectively. These grooves 37a and 37b are formed so as to extend along the axis of the semi-cylindrical bodies 35a to 36b, respectively, and open to the other half-cylindrical bodies 35a to 36b. Each of the feeder lines 9 and 10 can be disposed between the groove 37a and the groove 37b.

  In this manner, the lower surfaces of the semi-cylindrical bodies 35a to 36b are thermally connected to the upper surface (upper lid 21c) of the refrigerant container 18 via the brazing agent 39, with the power supply lines 9 and 10 being sandwiched therebetween. . Moreover, it is preferable to interpose the brazing agent 40 between the inner side surfaces of the grooves 37 a and 37 b and the outer side surfaces of the power supply lines 9 and 10.

  According to this embodiment, since the thermal connection area between the refrigerant container 18 and each of the power supply lines 9 and 10 can be increased by the amount covered by the cooling boots 35 and 36, each of the power supply lines 9 can be more effectively used. 10 can be cooled.

  Furthermore, if the cooling boots 35 and 36 are provided separately from the refrigerant container 18 as in this embodiment, the cooling range of the feeder lines 9 and 10 can be expanded while maintaining the shape of the refrigerant container 18. .

1 shows the overall configuration of an NMR (nuclear magnetic resonance) analyzer. The internal structure of the upper part of a probe main body is shown. It is a perspective view which expands and shows the principal part of FIG. It is sectional drawing which expands and shows the principal part of FIG. FIG. 5 is a view corresponding to FIG. 4 showing another embodiment of the present invention. FIG. 5 is a view corresponding to FIG. 4 showing another embodiment of the present invention. It is a top view which shows the refrigerant | coolant container of FIG. FIG. 4 is a view corresponding to FIG. 3 showing another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Cooling type NMR probe head 6 Probe main body 8 Antenna coil 9 Feed line 10 Feed line 11 Cooling member 17 Coil support member 18 Refrigerant container 21a Outer wall (an example of outer wall)
21b Inner wall (example of outer wall)
21c Top lid (example of outer wall)
21d Lower lid (example of outer wall)
23a, 23b Through-holes 24 to 26, 33 Insulating members 32a, 32b Groove 35 Cooling boot (an example of a covering member)

Claims (6)

In a cooled NMR probe head that includes an antenna coil and detects an NMR signal in a state where the antenna coil is cooled,
A feed line connected to the antenna coil and transmitting high frequency power to the antenna coil;
A cooling member thermally connected to the antenna coil so as to cool the antenna coil;
At least a portion of the feeder is thermally connected to the cooling member ;
The cooling member includes a refrigerant container having an outer wall that forms a cooling space through which a refrigerant can flow, and the power supply line is thermally connected to the outer wall of the refrigerant container. Formula NMR probe head. The refrigerant container is formed with a through hole that penetrates the outer wall and does not communicate with the cooling space, and at least a part of the power supply line is disposed through the through hole and is provided on an inner surface of the through hole. The cooled NMR probe head according to claim 1, wherein the cooled NMR probe head is thermally connected. The cooling member further includes a covering member that surrounds at least a part of an outer peripheral surface of a portion of the feeder line disposed between the refrigerant container and the antenna coil that is not thermally connected to the refrigerant container. The cooled NMR probe head according to claim 2, wherein at least a part of the covering member is thermally connected to the outer wall of the refrigerant container. The power supply line is thermally connected to the cooling member via an insulating member capable of electrically insulating the power supply line and the cooling member. The cooled NMR probe head according to any one of the above. Of the insulating member, at least a portion interposed between the power supply line and the cooling member is made of at least one material selected from single crystal sapphire, zirconia, quartz, and diamond. The cooled NMR probe head according to claim 4. A cooling-type NMR probe head according to any one of claims 1 to 5, a superconducting coil provided around the cooling-type NMR probe head, and a cryogenic container that accommodates the superconducting coil. A featured NMR analyzer.

Images