Patent Publication Number: US-2023145398-A1

Title: Angle Adjuster for NMR

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-184360 filed Nov. 11, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure relates to a technique of adjusting the angle of a sample tube placed inside an NMR probe device used for nuclear magnetic resonance (NMR) measurement. 
     Description of Related Art 
     A nuclear magnetic resonance (NMR) apparatus is an apparatus which applies a static magnetic field to atomic nuclei having spin magnetic moments so as to induce Larmor precession of the spin magnetic moments, irradiates thereto radiofrequency waves having the same frequency as the precession so as to cause resonance, and thereby detects signals from the atomic nuclei having the spin magnetic moments. 
     In NMR measurements performed with respect to solid samples, the MAS (magic angle spinning) method is typically employed. In the MAS method, a sample tube containing a solid sample is spun at a high speed while being tilted at the magic angle (of approximately 54.7 degrees) relative to the direction of the static magnetic field, and an NMR signal is detected in that state. 
     An NMR probe device for implementing the MAS method is used for NMR measurements by being inserted into a measurement space having the form of an elongate cavity provided in a magnetic field generator, a typical example of which is a superconducting magnet. In a MAS probe device, a sample tube containing a solid sample is placed in a sample tube support device in a state of being tilted at the magic angle relative to the magnetic field. 
     The sample tube, a detection coil, and the like are held in a MAS module, and the angle of this MAS module is adjusted to the magic angle by an angle adjustment mechanism. Conventional angle adjustment mechanisms are mechanisms which include a screw and a coupling, and which serve to convert rotation of the screw into tilt of the MAS module. An operator rotates the screw to thereby tilt the MAS module and adjust the angle of the MAS module to the magic angle. 
     JP 5117903 B discloses a sample tube for holding therein an unknown sample, which is the measurement target, and a standard sample used for magic angle adjustment. The space within the sample tube is divided by a partition wall, and the unknown sample and the standard sample are respectively held in separate spaces. 
     JP 2009-92424 A discloses a device in which signals derived from a sample by applying NMR pulses are stored together with corresponding tilt angles of the sample, and from the stored data, a tilt angle at which the maximum signal is obtained is extracted. 
     JP 2001-6302 A describes a configuration in which an elastic member is used to urge a gear against another gear. 
     Since conventional angle adjustment mechanisms are operated manually, there are difficulties in precisely adjusting the angle of a sample tube inside an NMR probe device. 
     The present disclosure is directed to precisely adjusting the angle of a sample tube inside an NMR probe device. 
     SUMMARY OF THE DISCLOSURE 
     According to one aspect of the present disclosure, an angle adjuster for NMR includes: a linear motion member configured to change, in an NMR probe device, an angle of a sample tube by a linear motion; a conversion mechanism configured to convert a rotary motion of a rotary member rotated by a drive device into a linear motion of the linear motion member; and a first elastic member which, at a portion where the linear motion member and the rotary member are in engagement with each other, provides a force that urges the linear motion member in one direction toward the rotary member. 
     According to the above-described configuration, a force that urges the linear motion member in one direction toward the rotary member is provided at the portion where the linear motion member and the rotary member are in engagement with each other, so that mechanical clearance (i.e., backlash) between the rotary member and the linear motion member can be reduced. It is therefore possible to control, with high precision, the linear motion of the linear motion member by the rotary motion of the rotary member, and the angle of the sample tube can be adjusted with high precision. 
     The above-noted one direction may be a direction opposite to the direction in which the linear motion member is linearly moved in order to tilt the sample tube from a vertical state to a tilted state. For example, a spring is used as the first elastic member. The spring is placed at a position where the spring is compressed when the linear motion member is linearly moved in order to tilt the sample tube from a vertical state to a tilted state. When the spring is compressed, elastic force of the spring increases, so that the linear motion member can be urged with a greater force. As a result, backlash can be further reduced. 
     The angle adjuster for NMR may further include a support member, which is configured to linearly move together with the linear motion member, and at that time, support the linear motion member while being supported by a guide. 
     The angle adjuster for NMR may further include: a shaft connected to the drive device and the rotary member, and configured to be rotated by the drive device and to transmit rotation to the rotary member; an engaging member which causes the shaft and the rotary member to be engaged with each other; and a second elastic member which, at the engaging member, urges the shaft against the engaging member. 
     The conversion mechanism and the drive device may be provided outside a device for forming a magnetic field for NMR measurement. 
     The angle adjuster for NMR may further include a control device configured to control the angle of the sample tube by controlling the rotary motion of the rotary member caused by the drive device. The control device may adjust the angle of the sample tube to a set angle by controlling the angle of the sample tube in such a manner that precision of a first control for linearly moving the linear motion member in order to rotate the sample tube from a vertical state to a tilted state is set higher than precision of a second control for linearly moving the linear motion member in order to rotate the sample tube from a tilted state to a vertical state. 
     The angle adjuster for NMR may further include: a control device configured to control the angle of the sample tube by controlling the rotary motion of the rotary member caused by the drive device; and a storage device configured to store a control value of the drive device used when an angle of a sample tube containing a standard sample was adjusted to a set angle by a rotary motion of the rotary member caused by the drive device. The control device may adjust an angle of a sample tube containing a measurement target sample to the set angle by controlling, according to the control value stored in the storage device, a rotary motion of the rotary member caused by the drive device. 
     According to the present disclosure, the angle of a sample tube can be precisely adjusted in an NMR probe device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiment(s) of the present disclosure will be described based on the following figures, wherein: 
         FIG.  1    is a diagram showing an NMR apparatus according to an embodiment; 
         FIG.  2    is a diagram showing an angle adjuster for NMR according to an embodiment; 
         FIG.  3    is a diagram showing a MAS module; 
         FIG.  4    is a perspective view showing a conversion mechanism and its surrounding configuration; 
         FIG.  5    is a cross-sectional view showing a conversion mechanism and its surrounding configuration; 
         FIG.  6    is a cross-sectional view showing a support member and a rotary member; 
         FIG.  7    is a cross-sectional view showing a support member and a rotary member; 
         FIG.  8    is a perspective view showing an engaging member; 
         FIG.  9    is a perspective view showing a tip portion of a shaft; 
         FIG.  10    is a cross-sectional view showing a conversion mechanism and its surrounding configuration; and 
         FIG.  11    is a diagram illustrating rotation of a MAS module. 
     
    
    
     DESCRIPTION OF NON-LIMITING EMBODIMENTS OF THE DISCLOSURE 
       FIG.  1    shows an example NMR apparatus according to an embodiment. The NMR apparatus  10  is an apparatus for measuring an NMR signal generated from observed nuclei in a sample. 
     A static magnetic field generator  12  is a device for generating a static magnetic field, and has, at its central part, a bore  14  in the form of a vertically-extending cavity. An NMR probe device  16  has a vertically-extending cylindrical shape as a whole, and is inserted into the bore  14  of the static magnetic field generator  12 . The NMR probe device  16  is a device for implementing the MAS method. In the NMR probe device  16 , a MAS module  18  is mounted. The MAS module  18  holds therein a sample tube and coils for transmission and for reception. The sample tube has, for example, a cylindrical shape, and contains a solid sample. The MAS module  18  is tilted at the magic angle relative to the static magnetic field. Accordingly, the sample tube held in the MAS module  18  is tilted at the magic angle relative to the static magnetic field. The sample tube is supported at its peripheral portion by a precision gas bearing on a spin axis tilted at the magic angle, and is spun at a high speed during measurement. 
       FIGS.  1  to  3    illustrate the outline of the configuration of an angle adjuster for NMR.  FIG.  2    is a diagram showing the angle adjuster for NMR. In  FIG.  2   , a part of a shaft  20  is not shown.  FIG.  3    is a diagram showing the MAS module  18 . The angle adjuster for NMR is a device for adjusting the angle of the MAS module  18 , that is, the angle of the sample tube. 
     The angle adjuster for NMR includes a shaft  20 , a support member  22 , a rotary member  24 , a conversion mechanism  26 , a shaft  28 , and a motor  30 . The motor  30  is an example of a drive device. 
     The shaft  20  is a columnar member, which is supported by the support member  22  and which linearly moves downward Z 1  or upward Z 2  together with the support member  22 . The shaft  20  and the support member  22  correspond to an example of a linear motion member. 
     The rotary member  24  is a cylindrical member. As will be described later, thread grooves are formed in the surface of the rotary member  24 . 
     As shown in  FIG.  2   , the MAS module  18  is rotatably supported by a rotation shaft  32 . One end  20   a  of the shaft  20  is in contact with an end portion of the MAS module  18  or a nearby portion thereof, and by linearly moving the shaft  20  and the support member  22 , the MAS module  18  is caused to rotate, which results in a change in the tilt of the MAS module  18 . 
     When the shaft  20  and the support member  22  are linearly moved downward Z 1  in the NMR apparatus  10 , the end portion of the MAS module  18  or a nearby portion thereof, with which the shaft  20  is in contact, is moved downward Z 1  in the NMR apparatus  10 , and as a result, the MAS module  18  is rotated from a vertical state to a tilted state. The direction of rotation from the vertical state to the tilted state is shown as rotation direction R 1  in  FIGS.  2  and  3   .  FIG.  2    shows the MAS module  18  in the tilted state. After the angle of the MAS module  18  is adjusted to the magic angle, a measurement is performed. 
     When the shaft  20  and the support member  22  are linearly moved upward Z 2  in the NMR apparatus  10 , the end portion of the MAS module  18  or a nearby portion thereof, with which the shaft  20  is in contact, is pushed upward Z 2  from the downward Z 1  position in the NMR apparatus  10 , and as a result, the MAS module  18  is rotated from the tilted state to the vertical state. The direction of rotation from the tilted state to the vertical state is shown as rotation direction R 2  in  FIGS.  2  and  3   .  FIG.  3    shows the MAS module  18  in the vertical state. At the time of replacing a sample, the MAS module  18  is rotated to the vertical state. The sample tube that has been placed inside the MAS module  18  in the vertical state via an opening formed at an upper part of the bore  14  is taken out of the static magnetic field generator  12  from the opening formed at the upper part of the bore  14 . Further, the sample tube is introduced into the bore  14  via the opening formed at the upper part of the bore  14 , and is placed inside the MAS module  18 . 
     The conversion mechanism  26  converts a rotary motion of the rotary member  24  rotated by the motor  30  into a linear motion of the shaft  20  and the support member  22 . A rotary motion of the rotary member  24  is converted into a linear motion of the shaft  20  and the support member  22  according to the feed screw principle. The configuration of the support member  22  and the rotary member  24  will be described later in detail. 
     The shaft  28  is a columnar member connecting between the motor  30  and the rotary member  24 . One end of the shaft  28  is connected to the motor  30 , and the other end of the shaft  28  is connected to the rotary member  24 . The motor  30  causes the shaft  28  to be rotated, which causes the rotary member  24  to be rotated. By means of the rotary motion of the rotary member  24 , the shaft  20  and the support member  22  are linearly moved downward Z 1  or upward Z 2 . 
     The shaft  20  and the support member  22  are linearly moved downward Z 1  or upward Z 2  according to the rotation direction of the motor  30 , that is, the rotation direction of the rotary member  24  connected to the motor  30  via the shaft  28 . 
     As the motor  30 , for example, a stepping motor or an ultrasonic motor is used. Naturally, a motor other than these may also be used. 
     As shown in  FIG.  1   , the shaft  20  is provided inside the NMR probe device  16 . The support member  22 , the rotary member  24 , the conversion mechanism  26 , the shaft  28 , and the motor  30  are provided outside the static magnetic field generator  12 . 
     In cases where a motor that uses magnetic forces is employed as the motor  30 , if the motor  30  is provided inside the static magnetic field generator  12 , the motor  30  is undesirably affected by magnetic force from the static magnetic field generator  12 . By providing the motor  30  outside the static magnetic field generator  12 , the motor  30  can be operated at a location where there is little influence of magnetic force from the static magnetic field generator  12 . 
     Further, in cases where a motor  30  unaffected by magnetic force such as an ultrasonic motor is used, if the motor  30  is provided inside the static magnetic field generator  12 , the motor  30  may possibly become a source of noise. By providing the motor  30  outside the static magnetic field generator  12 , it is possible to prevent the motor  30  from being a source of noise. 
     Further, by providing the support member  22 , the rotary member  24 , the conversion mechanism  26 , the shaft  28 , and the motor  30  outside the static magnetic field generator  12 , there is no need to reserve a space for providing these elements inside the NMR probe device  16 . 
     As shown in  FIG.  1   , the NMR apparatus  10  additionally includes a control device  34  and a storage device  36 . 
     The control device  34  controls the operation of the motor  30  and thereby controls the rotary motion of the rotary member  24  rotated by the motor  30 . By controlling the rotary motion of the rotary member  24 , the linear motion of the shaft  20  and the support member  22  is controlled, and as a result, the angle of the MAS module  18 , i.e., the angle of the sample tube, is adjusted. The control device  34  is, for example, a computer. 
     Functions of the control device  34  are implemented, for example, by cooperation of hardware and software. For example, the functions of the control device  34  are implemented by a processor such as a CPU (central processing unit) by reading out and executing a program stored in a memory of the control device  34 . The program is stored into the memory via a recording medium such as a CD or a DVD, or via a communication path such as a network. Functions of respective sections of the control device  34  may be implemented by an ASIC (application-specific integrated circuit), an FPGA (field-programmable gate array), or other programmable logic devices, or may be implemented by hardware such as electronic circuits. 
     The storage device  36  is a device constituting a storage area for storing data, and is, for example, a memory (such as a RAM, a DRAM, or a ROM), a hard disk drive, a solid-state drive (SSD), an optical disk, or the like. The storage device  36  stores a control value of the motor  30 . The control value is, for example, a value of an encoder of the motor  30 . 
     The angle adjuster for NMR will now be described in detail by reference to  FIGS.  4  to  7   .  FIG.  4    is a perspective view showing the conversion mechanism  26  and its surrounding configuration.  FIG.  5    is a cross-sectional view showing the conversion mechanism  26  and its surrounding configuration.  FIGS.  6  and  7    are cross-sectional views of the support member  22  and the rotary member  24 , and show expanded views of the part indicated by reference sign A in  FIG.  5   . 
     As shown in  FIGS.  4  and  5   , the support member  22  has formed therein holes  22   a  and  22   b  penetrating through the support member  22  in the extending direction of the shaft  20 . The shaft  20  is inserted into the hole  22   a  and supported by the support member  22 . 
     The rotary member  24  is inserted into the hole  22   b  formed in the support member  22 . As shown in  FIGS.  6  and  7   , thread grooves  22   c  are formed in the inner surface of the hole  22   b  (that is, in the surface of the passageway formed by the hole  22   b ), and thread grooves  24   a  are formed in the surface of the rotary member  24 . When the rotary member  24  is inserted into the hole  22   b , the thread grooves  22   c  in the inner surface of the hole  22   b  and the thread grooves  24   a  in the surface of the rotary member  24  mesh with each other. In this way, the support member  22 , which constitutes a part of the linear motion member, and the rotary member  24  are engaged with each other. Here, the shape and pitch of the thread grooves  22   c ,  24   a  shown in  FIGS.  6  and  7    are only schematically depicted as a matter of convenience for explaining the operations of the support member  22  and the rotary member  24 . The actual shape and pitch are not limited to the shape and pitch shown. 
     A rotary motion of the rotary member  24  is converted into a linear motion of the shaft  20  and the support member  22  according to the feed screw principle. In other words, when the rotary member  24  is rotated, the support member  22  in engagement with the rotary member  24  by means of the thread grooves  22   c ,  24   a  is caused to linearly move downward Z 1  or upward Z 2 . The shaft  20  supported by the support member  22  is also linearly moved downward Z 1  or upward Z 2  in accordance with the linear movement of the support member  22 . 
     As shown in  FIG.  5   , the rotary member  24  is rotatably supported in the conversion mechanism  26  by bearings  38   a  and  38   b.    
     In the conversion mechanism  26 , a spring  40  is provided. The spring  40  is an example of a first elastic member, and, at the portions where the support member  22  constituting a part of the linear motion member and the rotary member  24  are in engagement with each other, provides a force that urges the support member  22  in one direction toward the rotary member  24 . The spring  40  will now be described in detail. 
     The spring  40  is located along the extending direction of the columnar rotary member  24  (that is, along the vertical direction). As shown in  FIGS.  4  and  5   , one end of the spring  40  is in contact with a wall  26   a  provided at a lower part of the conversion mechanism  26 . 
     As shown in  FIGS.  5  to  7   , a spring receiving portion  22   d  is formed on the support member  22 . The spring receiving portion  22   d  is formed at a position facing the wall  26   a  across the spring  40 . The other end of the spring  40  is in contact with this spring receiving portion  22   d.    
     The spring  40  is located along the extending direction of the rotary member  24  by being sandwiched between the wall  26   a  and the spring receiving portion  22   d . With this arrangement, the spring  40  provides, to the support member  22 , a force that urges the support member  22  upward Z 2 . More specifically, as shown in  FIGS.  6  and  7   , at the portions where the support member  22  and the rotary member  24  are in engagement with each other, a force that urges the support member  22  upward Z 2  is provided by the spring  40 . As a result, the upper side surfaces of the thread grooves  22   c  of the support member  22  are placed into contact with the lower side surfaces of the thread grooves  24   a  of the rotary member  24 . Here, the upward Z 2  direction is an example of the one direction. 
       FIG.  6    shows a state before the elastic force of the spring  40  is made to act on the support member  22 .  FIG.  7    shows a state in which the elastic force of the spring  40  is acting on the support member  22 . At a point before the elastic force of the spring  40  is made to act on the support member  22 , a gap (i.e., backlash) occurs between the thread grooves  22   c  of the support member  22  and the thread grooves  24   a  of the rotary member  24 . On the other hand, in a state in which the elastic force of the spring  40  is acting on the support member  22 , the support member  22  is urged upward Z 2 , so that no gap (i.e., no backlash) occurs between the thread grooves  22   c  of the support member  22  and the thread grooves  24   a  of the rotary member  24 , or the gap is reduced. In this way, by urging the support member  22  upward Z 2  using the spring  40 , occurrence of backlash between the thread grooves  22   c  and the thread grooves  24   a  can be suppressed. This makes it possible to suppress errors that may occur when a rotary motion of the rotary member  24  is converted into a linear motion of the linear motion member (i.e., the shaft  20  and the support member  22 ) in the conversion mechanism, and accordingly, the angle of the MAS module  18  can be controlled with high precision. 
     The upward Z 2  direction, namely, the one direction, is a direction opposite to the direction (the downward Z 1  direction) in which the linear motion member (i.e., the shaft  20  and the support member  22 ) is linearly moved in order to tilt the MAS module  18  from the vertical state to the tilted state. In other words, the one direction is the direction in which the linear motion member is linearly moved in order to rotate the MAS module  18  from the tilted state to the vertical state. 
     Further, as shown in  FIGS.  4  and  5   , a support member  42  is provided. The support member  42  is a member that linearly moves together with the linear motion member (i.e., the shaft  20  and the support member  22 ) while supporting the linear motion member. An end portion of the support member  22 , which is located on a side opposite to the hole  22   a  across the hole  22   b , is fixed to the support member  42 . The support member  42  is a columnar member and is supported by a guide  44 , which is provided on a side opposite to the support member  22  across the support member  42 . The support member  42  linearly moves downward Z 1  or upward Z 2  while being in contact with a sliding surface  44   a  of the guide  44  and thereby being supported by the guide  44 . Although the shaft  20  is supported by the support member  22 , the shaft  20  is supported by the support member  22  in a cantilever manner. By using the support member  42  to support the support member  22  constituting the linear motion member, the shaft  20  can be linearly moved stably. 
     Furthermore, an engaging member  46  is provided. The engaging member  46  and its surrounding configuration will now be described by reference to  FIGS.  5 ,  8 , and  9   .  FIG.  8    is a perspective view showing the engaging member  46 .  FIG.  9    is a perspective view showing an end portion of the shaft  28 . 
     The engaging member  46  is a member which is fixed to a lower end portion of the rotary member  24  and which causes the rotary member  24  and the shaft  28  to be engaged with each other. A tip portion  28   a  of the shaft  28  has a polygonal shape. In the example shown in  FIG.  9   , the tip portion of the shaft  28  has a hexagonal shape. The engaging member  46  has a hole  46   a  formed therein. The hole  46   a  has a shape corresponding to the tip portion  28   a  of the shaft  28 . In the example shown in  FIG.  8   , the hole  46   a  has a hexagonal shape. The tip portion  28   a  of the shaft  28  is inserted into the hole  46   a  of the engaging member  46 , and the rotary member  24  and the shaft  28  are thereby connected via the engaging member  46 . Rotation performed by the motor  30  is transmitted via the shaft  28  and the engaging member  46  to the rotary member  24 , and the rotary member  24  is rotated. 
     A spring  48  is provided inside the hole  46   a  of the engaging member  46 . The spring  48  is an example of a second elastic member, and is a member that urges the tip portion  28   a  of the shaft  28  against the engaging member  46  (more specifically, against a side surface of the hole  46   a  of the engaging member  46 ). Specifically, the spring  48  causes the tip portion  28   a  inserted in the hole  46   a  to be pushed against and placed into contact with one surface of the polygonal hole  46   a . With this arrangement, a gap (i.e., backlash) is eliminated at the part where the tip portion  28   a  is in contact with the one surface of the hole  46   a . As a result, it is possible to suppress occurrence of mechanical clearance at the time the shaft  28  is rotated. 
     Operations of the angle adjuster for NMR in adjusting the angle of the MAS module  18  will now be described by reference to  FIGS.  2 ,  3 ,  5 , and  10   .  FIG.  10    is a cross-sectional view showing the conversion mechanism  26  and its surrounding configuration. 
     The rotary member  24  is rotated by an operation of the motor  30 , and this rotation is transmitted to the support member  22 , as a result of which the support member  22  and the shaft  20  are linearly moved downward Z 1  or upward Z 2 . 
       FIG.  5    illustrates a state in which the support member  22  and the shaft  20  have moved upward Z 2 . In this state, as shown in  FIG.  3   , the shaft  20  pushes upward Z 2  the end portion of the MAS module  18  or a nearby portion thereof, with which the shaft  20  is in contact. This causes the MAS module  18  to be rotated from the tilted state to the vertical state. When the support member  22  is in the state of having moved upward Z 2 , the spring  40  is placed in an extended state. 
       FIG.  10    illustrates a state in which the support member  22  and the shaft  20  have moved downward Z 1 . In this state, as shown in  FIG.  2   , the MAS module  18  is rotated from the vertical state to the tilted state. When the support member  22  is in the state of having moved downward Z 1 , the spring  40  is placed in a compressed state. 
     When the support member  22  is in the state of having moved downward Z 1 , compared to when the support member  22  is in the state of having moved upward Z 2 , the spring  40  is more compressed, so that the force by which the spring  40  urges the spring receiving portion  22   d  is greater. In other words, in the operation of rotating the MAS module  18  from the vertical state to the tilted state, the force by which the spring  40  urges the spring receiving portion  22   d  becomes greater. Accordingly, the force by which the upper side surfaces of the thread grooves  22   c  of the support member  22  push against the lower side surfaces of the thread grooves  24   a  of the rotary member  24  becomes greater (see  FIG.  7   ), so that occurrence of backlash can be further suppressed. As a result, the precision of the operation performed in linearly moving the linear motion member (i.e., the shaft  20  and the support member  22 ) in order to rotate the MAS module  18  from the vertical state to the tilted state becomes higher than the precision of the operation performed in linearly moving the linear motion member in order to rotate the MAS module  18  from the tilted state to the vertical state. In other words, occurrence of backlash can be further suppressed, and the angle of the MAS module  18  can be adjusted with higher precision. 
     The control device  34  may adjust the angle of the MAS module  18  to a set angle (e.g., the magic angle) while changing the precision of control between a first control for linearly moving the linear motion member in order to rotate the MAS module  18  from the vertical state to the tilted state, and a second control for linearly moving the linear motion member in order to rotate the MAS module  18  from the tilted state to the vertical state. Specifically, the control device  34  adjusts the angle of the MAS module  18  to the magic angle with the precision of the first control set higher than the precision of the second control. The first control and the second control will now be described by reference to  FIG.  11   .  FIG.  11    is a diagram illustrating rotation of the MAS module  18 . 
     For example, in the first control, compared to in the second control, the control device  34  may rotate the motor  30  at a lower speed to thereby reduce the rotation speed of the MAS module  18 , or may rotate the motor  30  in smaller increments to thereby cause the MAS module  18  to be rotated in smaller increments. In other words, when rotating the MAS module  18  from the vertical state to the tilted state (that is, when rotating the MAS module  18  in the rotation direction R 1 ), compared to when rotating the MAS module  18  from the tilted state to the vertical state (that is, when rotating the MAS module  18  in the rotation direction R 2 ), the control device  34  reduces the rotation speed of the MAS module  18 , causes the MAS module  18  to be rotated in smaller increments, and the like. 
     Reference sign  50  in  FIG.  11    indicates the magic angle. For example, the MAS module  18  containing a standard sample is placed in the NMR probe device  16 , and while the MAS module  18  is being rotated, an NMR signal from the standard sample is detected. The control device  34  causes the MAS module  18  to be rotated from the vertical state to the tilted state (i.e., performs the first control), and when the angle of the MAS module  18  exceeds the magic angle (e.g., when a peak is detected in the NMR signal), causes the MAS module  18  to be rotated in the rotation direction R 2  (i.e., performs the second control). Further, when the angle of the MAS module  18  moves past the magic angle (e.g., when a peak is detected in the NMR signal), the control device  34  causes the MAS module  18  to be rotated in the rotation direction R 1  (i.e., performs the first control). By repeating this operation, the control device  34  adjusts the angle of the MAS module  18  to the magic angle. For example, the control device  34  adjusts the angle of the MAS module  18  to the magic angle by gradually reducing the range by which the angle of the MAS module  18  is varied. 
     As shown in  FIG.  11   , in the first control and in the second control, the control device  34  may employ different ranges by which the angle of the MAS module  18  is varied. For example, in the first control, compared to in the second control, the control device  34  reduces the range by which the angle of the MAS module  18  is varied. At the time of rotation of the MAS module  18  in the rotation direction R 1 , the spring  40  is compressed, and backlash can be further suppressed. For this reason, when rotating the MAS module  18  in the rotation direction R 1 , compared to when rotating the MAS module  18  in the rotation direction R 2 , the MAS module  18  can be rotated while reducing the range by which the angle of the MAS module  18  is varied with high precision 
     For example, when adjusting the angle of the MAS module  18  to the magic angle, a standard sample is used. The angle of the MAS module  18  containing the standard sample is adjusted to the magic angle, and the control value (e.g., the encoder value) of the motor  30  used at the time of this adjustment is stored in the storage device  36 . This control value is the value corresponding to the magic angle. After the sample is changed from the standard sample to a measurement target sample, the control device  34  adjusts the angle of the MAS module  18  to the magic angle by operating the motor  30  according to the control value stored in the storage device  36  and controlling the rotary motion of the rotary member  24 . This process will now be described in detail. 
     First, a sample tube containing a standard sample is placed inside the MAS module  18 . The control device  34  operates the motor  30  to repeatedly perform the above-described first control and second control, and to thereby cause the MAS module  18  to be rotated in the rotation direction R 1  or rotation direction R 2 . For example, the controls illustrated in  FIG.  11    are performed. During this rotation, an NMR signal from the standard sample is detected. The angle of the MAS module  18  at which a peak is detected in the NMR signal is detected as the magic angle. This detection may be performed automatically by the control device  34 , or may be performed manually by an operating person. The control value (e.g., the encoder value) of the motor  30  used when this angle is detected is stored in the storage device  36  as the control value corresponding to the magic angle. 
     Next, the MAS module  18  is rotated to the vertical state, and the sample contained in the MAS module  18  is changed from the standard sample to a measurement target sample. The sample tube containing the measurement target sample is placed inside the MAS module  18 . The control device  34  operates the motor  30  according to the control value stored in the storage device  36 , and thereby adjusts the angle of the MAS module  18  to the angle corresponding to that control value. As a result, the angle of the MAS module  18  containing the measurement target sample is adjusted to the magic angle. 
     According to the angle adjuster for NMR according to an embodiment, by urging the support member  22  in the one direction using the spring  40 , backlash can be reduced, and as a result, the angle of the MAS module  18  can be adjusted with high precision. For example, by urging the support member  22  in the upward Z 2  direction, which is the direction opposite to the downward Z 1  direction in which the linear motion member is linearly moved in order to rotate the MAS module  18  from the vertical state to the tilted state, the elastic force of the spring  40  becomes greater as the linear motion member is linearly moved downward Z 1 , so that backlash is reduced more, and the angle of the MAS module  18  can be adjusted with higher precision. 
     Further, by urging the shaft  28  against the engaging member  46  using the spring  48 , backlash between the shaft  28  and the engaging member  46  is reduced, so that the rotation of the rotary member  24  can be controlled with high precision. 
     For example, in a case where a stepping motor in which rotation can be controlled with a precision of 1/1000 rotation is used as the motor  30 , and the pitch of the thread grooves  22   c  of the support member  22  and the thread grooves  24   a  of the rotary member  24  is 0.5, the minimum rotation angle of the MAS module  18  of 0.002 degrees can be achieved. As such, the angle of the MAS module  18  can be adjusted with higher precision compared to when the angle of the MAS module  18  is adjusted manually by an operating person.