Cell unit

Abstract

The present invention provides a cell unit that can appropriately suppress the deposition of alkali metals on the inner surface of the light-transmitting wall portion of the cell's main body during heater operation. [Solution] The cell unit includes a cell 11 containing an alkali metal, which has a main body portion 11a through which the laser beam L passes; a heat conductive member 5, at least a portion of which is disposed on the main body portion 11a; and a heater 12 that is thermally connected to the heat conductive member 5. The heat conductive member 5 covers the outer surface 111a of the wall portion 111 through which the laser beam L passes, and is transparent to the laser beam L.

Description

Technical Field

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[0001] The present invention relates to a cell unit used, for example, in a photoexcited magnetic sensor.

Background Art

[0002] As a cell unit used, for example, in a photoexcited magnetic sensor, there is known one including a main body through which light passes, a cell in which an alkali metal is enclosed, and a heater that generates heat for heating the main body of the cell (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​The cell unit of the present invention is [1] a cell comprising a main body portion through which light passes and containing an alkali metal, a first heat conductive member whose part is disposed on the main body portion, and a heater thermally connected to the first heat conductive member, wherein the first heat conductive member covers the outer surface of the wall portion of the main body portion through which the light passes and is transparent to the light.

[0007] In the above cell unit, the outer surface of the wall portion of the cell body through which light passes is covered with a first heat conductive member that is transparent to light. As a result, the heat generated in the heater is transferred to the wall portion via the first heat conductive member, thereby suppressing a relative decrease in the temperature of the wall portion of the cell body through which light passes when the heater is operating. Therefore, with the above cell unit, the deposition of alkali metals on the inner surface of the wall portion of the cell body through which light passes can be appropriately suppressed when the heater is operating.

[0008] The cell unit of the present invention may also be [2] "the cell unit according to [1] above, wherein the first heat conductive member is formed of sapphire." According to this cell unit, a first heat conductive member can be obtained in which both heat conduction and light transmission are ensured.

[0009] The cell unit of the present invention may also be [3] "the cell unit according to [1] or [2] above, wherein the thickness of the first heat conductive member in the direction through which the light passes is 0.1 mm or more and 1 mm or less." With this cell unit, sufficient heat transfer can be ensured by making the thickness of the first heat conductive member 0.1 mm or more, and the size of the cell unit can be suppressed by making the thickness of the first heat conductive member 1 mm or less.

[0010] The cell unit of the present invention may also be [4] "a cell unit according to any one of [1] to [3] above, wherein the main body and the first heat conductive member are joined to each other via a first adhesive layer, and the first adhesive layer is transparent to light." In this case, heat transfer and light transmission between the main body and the first heat conductive member can be ensured.

[0011] The cell unit of the present invention may also be [5] "a cell unit according to any one of [1] to [4] above, further comprising a second heat conductive member, at least a portion of which is disposed on the main body, and the heater being disposed on the second heat conductive member." With this cell unit, the heat generated in the heater can be efficiently transferred to the main body of the cell via the second heat conductive member.

[0012] The cell unit of the present invention may also be [6] "the cell unit according to [5] above, wherein the second heat conductive member is formed of sapphire or alumina." According to this cell unit, a second heat conductive member with at least heat transfer properties can be obtained.

[0013] The cell unit of the present invention may also be the cell unit according to [5] or [6] above, wherein the first heat conductive member and the second heat conductive member are in contact with each other or joined to each other via a second adhesive layer. With this cell unit, heat is directly transferred between the first heat conductive member and the second heat conductive member, so that the heat generated in the heater can be efficiently transferred to the main body of the cell. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a cell unit that can appropriately suppress the deposition of alkali metals on the inner surface of the light-passing wall portion of the cell body when the heater is in operation. [Brief explanation of the drawing]

[0015] [Figure 1]This is a diagram for explaining the operation of a photoexcited magnetic sensor module. [Figure 2] (a) is a perspective view of the photoexcited magnetic sensor module, and (b) is a perspective view of the photoexcited magnetic sensor module with the outer cover removed. [Figure 3] FIG. 2(b) is a perspective view of the photoexcited magnetic sensor module with the housing cover of the housing removed. [Figure 4] It is a cross-sectional view taken along line IV-IV of FIG. 3. [Figure 5] FIG. 3 is a plan view of the photoexcited magnetic sensor module with the case cover of the cell case removed. [Figure 6] It is a perspective view of a part of the cell unit. [Figure 7] It is a cross-sectional view taken along line VII-VII of FIG. 6. [Figure 8] It is a cross-sectional view taken along line VIII-VIII of FIG. 6. [Figure 9] FIG. 6 is a schematic plan view of the heater. [Figure 10] (a) and (b) are cross-sectional views of the cell unit according to a modified example. [Figure 11] This is a diagram for explaining the operation of the photoexcited magnetic sensor module according to a modified example.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations are omitted.

[0017] The photoexcitation magnetic sensor module 1 shown in FIGS. 1 to 5 (hereinafter also referred to as "sensor module 1") is an optically pumped magnetometer (OPM) and is used, for example, for biomagnetic field measurement. As an example, the sensor module 1 can be used as a magnetoencephalograph that measures the magnetic field generated in the brain, or a magnetocardiograph or a magnetomyelograph that measures the magnetic field generated in the heart or spinal cord. [Configuration of Sensor Module]

[0018] As shown in FIGS. 1 to 5, the sensor module 1 includes a cell unit 2, a housing 3 that houses the cell unit 2, and an outer cover 4 that covers the outer surface of the housing 3. The cell unit 2 has a cell 11, a plurality of heat conduction members 5 to 9, a heater 12, a heat insulating member 13, and a cell case 14, and at least a part thereof is surrounded by a coil unit 15. The sensor module 1 further includes a light source 21, a lens 22, a mirror 23, a quarter-wave plate 24, a photodetector 25, a connector member 26, and a connector cover 27. [Operation of Sensor Module]

[0019] The operation (principle of detecting magnetic field changes) of the sensor module 1 will be described while referring to FIG. 1. During measurement, the sensor module 1 (cell 11) is placed near the measurement target. A gas GS containing an alkali metal is enclosed in the cell 11. During measurement, the alkali metal in the cell 11 is heated by the heater 12 (see FIG. 5), and the inside of the cell 11 is filled with alkali metal vapor. In this state, the laser beam L output from the light source 21 passes through the cell 11. The laser beam L is incident on the cell 11 in a state of being circularly polarized by the quarter-wave plate 24. The circularly polarized laser beam L polarizes the spin of the alkali metal vapor in the cell 11 by optical pumping (photoexcitation). That is, the laser beam L functions as a pump beam that polarizes the spin of the alkali metal vapor in the cell 11 by optical pumping.

[0020] The laser light L that has passed through cell 11 is detected by photodetector 25. At this time, the intensity of the laser light L detected by photodetector 25 (i.e., the degree to which the laser light L is absorbed by the alkali metal vapor in cell 11) changes according to the spin polarization state of the alkali metal vapor in cell 11. Here, the spin polarization state of the alkali metal vapor in cell 11 changes under the influence of the magnetic field of the object being measured. Therefore, based on the intensity of the detected laser light L, changes in the magnetic field of the object being measured can be detected. In this way, the laser light L also functions as a probe light for detecting the spin polarization state of the alkali metal vapor in cell 11. In this case, sensor module 1 is a single-laser sensor module in which the laser light L serves as both the pump light and the probe light. [Configuration of each part of the sensor module]

[0021] The configuration of each part of the sensor module 1 will be explained with reference to Figures 2 to 5. The following explanation will refer to the X direction, the Y direction perpendicular to the X direction, and the Z direction perpendicular to both the X and Y directions as shown in Figures 2 to 5. The housing 3 is formed in a roughly rectangular parallelepiped shape from, for example, a resin material, and has a housing body 3a and a housing lid 3b. Figure 2(b) shows the state with the housing lid 3b attached, and Figure 3 shows the state with the housing lid 3b removed.

[0022] As shown in Figures 4 and 5, the housing 3 contains a cell unit arrangement section 3c where the cell unit 2 is placed, an optical component arrangement section 3f where the light source 21, lens 22, and mirror 23 are placed, and a photodetector arrangement section 3g where the photodetector 25 is placed. The optical component arrangement section 3f contains an optical path section 3h, which is the space through which the laser light L output from the light source 21 and directed toward the cell unit 2 travels. The photodetector arrangement section 3g is located on the opposite side of the optical path section 3h from the cell unit arrangement section 3c.

[0023] The light source 21 is, for example, a vertical cavity surface-emitting laser, which outputs laser light L. In this example, the light source 21 is mounted on the connector member 26.

[0024] Lens 22 aligns the laser light L output from light source 21. Mirror 23 reflects the laser light L, which has been aligned by lens 22, toward cell unit 2. A quarter-wave plate 24 is placed between mirror 23 and cell unit 2. The quarter-wave plate 24 introduces a phase difference of π / 2 (=λ / 4) between the vertically polarized components of the incident light. The quarter-wave plate 24 converts the linearly polarized laser light L output from light source 21 into circularly polarized light.

[0025] Cell unit 2 is located in cell unit arrangement section 3c. Cell unit 2 has a cell 11 filled with gas GS containing alkali metals. Details of cell unit 2 will be described later. Circularly polarized laser light L, converted by a quarter-wave plate 24, is incident on cell unit 2. The laser light L incident on cell unit 2 passes through cell 11 and is emitted from cell unit 2 toward photodetector 25. In this example, the laser light L passes through cell 11 along the X direction. The photodetector 25 is located in photodetector arrangement section 3g. The photodetector 25 is, for example, a photodiode and detects the laser light L that has passed through cell unit 2.

[0026] The connector member 26 is provided on one side of the housing 3 in the Z direction. The heater 12, coil unit 15, light source 21, and photodetector 25 are electrically connected to the connector member 26, and the connector member 26 is used for the electrical connection of each of these parts to the outside. A connector cover 27 is detachably attached to the connector member 26. As shown in Figure 2, the outer cover 4 is formed in a substantially rectangular parallelepiped shape and covers the outer surface of the housing 3, except for the surface on the side where the connector cover 27 is located (one side in the Z direction). [Cell Unit]

[0027] The details of the cell unit 2 will be explained with reference to Figures 3 to 5. As described above, the cell unit 2 has a cell 11, a plurality of heat conductive members 5 to 9, a heater 12, an insulating member 13, and a cell case 14, and is at least partially surrounded by a coil unit 15. The cell 11, the plurality of heat conductive members 5 to 9, the heater 12, and the insulating member 13 are housed inside the cell case 14, and the coil unit 15 is located outside the cell case 14.

[0028] Cell 11 has a main body 11a and a protrusion 11b. Cell 11 is formed of a translucent material such as glass or silicon. Cell 11 is sealed with gas GS consisting of an alkali metal and an inert gas. The alkali metal sealed in cell 11 is one or more of potassium, lithium, sodium, rubidium, and cesium. The inert gas sealed in cell 11 is one or more of helium, neon, argon, krypton, xenon, nitrogen, or hydrogen. The main body 11a is, for example, a rectangular parallelepiped container portion. The protrusion 11b is a tubular portion connected to the main body 11a, and is a portion that has been sealed after being used mainly as a passage for gas intake and exhaust, such as exhaust or introduction of gas GS.

[0029] Multiple heat conductive members 5 to 9 cover the main body portion 11a of the cell 11. The heater 12 is placed on the heat conductive member 7. The heater 12 is thermally connected to the cell 11 via the heat conductive member 7. The heater 12 is configured in a sheet shape and includes, for example, an electric heating element (a resistor such as a metal wire) that generates heat when an electric current is passed through it. The heater 12 generates heat when an electric current is passed through it, thereby heating the cell 11 via the multiple heat conductive members 5 to 9. Details of the multiple heat conductive members 5 to 9 and the heater 12 will be described later.

[0030] The thermal insulation member 13 is positioned inside the cell case 14 so as to be located outside the cell 11, the plurality of heat conductive members 5 to 9, and the heater 12 (hereinafter referred to as "cell 11, etc."). In this example, the thermal insulation member 13 is composed of a plurality of plate-shaped members 13a. The plurality of plate-shaped members 13a are arranged to fill the space between the cell 11, etc. and the cell case 14. More specifically, in the space between the plurality of heat conductive members 5, 6, 9 covering the main body portion 11a of the cell 11 and the cell case 14, the plurality of plate-shaped members 13a are arranged to fill as little gap as possible except for the laser light L transmission area in the main body portion 11a, and in the space between the protrusion 11b of the cell 11 and the cell case 14, the plate-shaped members 13a are arranged to surround and fill the entire protrusion 11b while having a region spaced apart from the outer surface of the protrusion 11b of the cell 11. The plate-shaped members 13a are members whose thermal insulation properties are enhanced by, for example, the formation of an air layer inside. The cell case 14 is formed in a substantially rectangular parallelepiped shape from, for example, a resin material, and has a case body portion 14a and a case lid portion 14b. Figure 3 shows the case with the case lid portion 14b attached, and Figure 5 shows the case with the case lid portion 14b removed. Note that the hatching of the plate-shaped member 13a is omitted in Figure 4.

[0031] As shown in Figure 5, the case body 14a has a pair of first wall portions 14c facing each other in the X direction and a pair of second wall portions 14d facing each other in the Z direction. Multiple (two in this example) plate-like members 13a are placed between each first wall portion 14c and the cell 11, etc., and multiple (four in this example) plate-like members 13a are placed between each second wall portion 14d and the cell 11, etc. Although not shown, heat insulating members 13 (multiple plate-like members 13a) are also placed between the wall portion in the Y direction of the case body 14a (the wall portion facing the case lid portion 14b in the Y direction) and the cell 11, etc., and between the case lid portion 14b and the cell 11, etc. Thus, in this example, the cell 11, etc. is housed in the cell case 14 with the heat insulating members 13 interposed between it and the cell case 14. As shown in Figure 4, one of the pair of first wall portions 14c has an aperture 14e through which the laser light L reflected by the mirror 23 and heading toward the cell 11 passes, and the other of the pair of first wall portions 14c has an aperture 14f through which the laser light L that has passed through the cell 11 passes.

[0032] As shown in Figure 3, the coil unit 15 is located outside the cell case 14. The coil unit 15 is composed of, for example, multiple coils, which generate a magnetic field acting on the cell 11. The sensor module 1 generates a magnetic field acting on the cell 11 using the coil unit 15 and detects changes in the magnetic field within the cell 11 using laser light L (probe light).

[0033] The coil unit 15 generates a corrective magnetic field, for example, so that the influence of magnetic fields other than the magnetic field being measured on the cell 11 approaches zero. For example, the coil unit 15 may generate a magnetic field in the opposite direction to the Earth's magnetic field so that the influence of the Earth's magnetic field is canceled out. Alternatively or in addition, the coil unit 15 may generate a modulated magnetic field that acts on the cell 11. For example, the coil unit 15 may generate an alternating magnetic field modulated at a predetermined frequency for increased sensitivity, or it may generate a modulated magnetic field to enable detection of the direction of magnetic field changes (positive and negative directions in each axis). In this example, the coil unit 15 is made of a flexible circuit board and is arranged to surround the four sides of the cell case 14 (cell 11) (sides of the cell case 14 other than each second wall portion 14d) (sides of the cell 11 other than the two sides in the extending direction of the protrusion 11b), and is drawn out to one side in the Z direction and electrically connected to the connector member 26. [Multiple heat conductive members and heaters]

[0034] As shown in Figures 6-8, in cell 11, the main body 11a includes one wall 111 in the X direction, the other wall 112 in the X direction, one wall 113 in the Y direction, the other wall 114 in the Y direction, one wall 115 in the Z direction, and the other wall 116 in the Z direction. The protrusion 11b extends from the wall 115 to one side in the Z direction. In cell 11, laser light (light) L enters the main body 11a through the wall 111, passes through the gas GS inside the main body 11a, and exits the main body 11a through the wall 112. In this way, the laser light L passes through the main body 11a. The optical path P of the laser light L extends in the X direction within the main body 11a. The width (beam diameter) of the optical path P of the laser light L is determined, for example, by the lens 22 (see Figure 5).

[0035] The heat conduction member (first heat conduction member) 5 is joined to the outer surface 111a of the wall portion 111 via the adhesive layer 16 (first adhesive layer). The heat conduction member (first heat conduction member) 6 is joined to the outer surface 112a of the wall portion 112 via the adhesive layer 16. The heat conduction member (second heat conduction member) 7 is joined to the outer surface 113a of the wall portion 113 via the adhesive layer 16. The heat conduction member 8 is joined to the outer surface 114a of the wall portion 114 via the adhesive layer 16. The heat conduction member 9 is joined to the outer surface 116a of the wall portion 116 via the adhesive layer 16. The adhesive layer 16 is transparent to laser light L. However, transparency to the laser beam L is essential only for the adhesive layer 16 on the heat conduction members 5 and 6 through which the laser beam L passes. The adhesive layer 16 on the heat conduction members 7, 8 and 9 through which the laser beam L does not pass does not need to be transparent to the laser beam L. In this way, each of the heat conduction members 5 to 9 is arranged on the main body 11a. Note that each of the heat conduction members 5 to 9 may be arranged on the main body 11a so as to be in contact with the main body 11a without the adhesive layer 16 in between.

[0036] Each of the heat conductive members 5 to 9 is formed in a plate shape (for example, a rectangular plate shape) from a non-conducting material. A non-conducting material is a material with low conductivity, a so-called electrical insulating material. The heat conductive member 5 covering the outer surface 111a of wall 111, which is a wall portion of the main body 11a through which the laser beam L passes, is transparent to the laser beam L. Similarly, the heat conductive member 6 covering the outer surface 112a of wall 112, which is a wall portion of the main body 11a through which the laser beam L passes, is transparent to the laser beam L. In addition, the heat conductive members 7, 8, and 9 covering the outer surfaces 113a, 114a, and 116a of wall portions 113, 114, and 116a of the main body 11a that are not walls through which the laser beam L passes may or may not be transparent to the laser beam L. In this example, each of the heat conductive members 5 and 6 is made of sapphire, and each of the heat conductive members 7 to 9 is made of sapphire or alumina. The thickness of each heat conductive member 5 to 9 is 0.1 mm or more and 1 mm or less. The thermal conductivity of the material of each heat conductive member 5 to 9 is higher than the thermal conductivity of the material constituting each wall portion 111, 112 through which the laser beam L passes in the main body portion 11a. In other words, the heat conductive member in this embodiment is a member having a thermal conductivity higher than the thermal conductivity of the material constituting each wall portion 111, 112 through which the laser beam L passes in the main body portion 11a.

[0037] Heat conduction member 5 is in contact with each of the heat conduction members 7 and 8 at each of its edges in the Y direction, and with heat conduction member 9 at the other edge in the Z direction. Heat conduction member 6 is in contact with each of the heat conduction members 7 and 8 at each of its edges in the Y direction, and with heat conduction member 9 at the other edge in the Z direction. Heat conduction member 7 is in contact with each of the heat conduction members 5 and 6 at each of its edges in the X direction, and with heat conduction member 9 at the other edge in the Z direction. Heat conduction member 8 is in contact with each of the heat conduction members 5 and 6 at each of its edges in the X direction, and with heat conduction member 9 at the other edge in the Z direction. Heat conduction member 9 is in contact with each of the heat conduction members 5 and 6 at each of its edges in the X direction, and with heat conduction members 7 and 8 at each of its edges in the Y direction. In this way, among the multiple heat conduction members 5 to 9, adjacent heat conduction members are in contact with each other. In other words, the main body portion 11a is entirely surrounded by the heat conductive members 5 to 9, except for the wall portion 115 on which the protrusion 11b is provided. Among the multiple heat conductive members 5 to 9, adjacent heat conductive members may be joined to each other via a second adhesive layer. In this embodiment, the second adhesive layer includes a part of the adhesive layer 16. The second adhesive layer does not have to include the adhesive layer 16 and may be formed from a material different from the adhesive layer 16. In this case, the second adhesive layer may not be transparent to the laser light L.

[0038] The heater 12 is bonded to the surface 7a of the heat conductive member 7 opposite to the cell 11 via an adhesive layer 17. In this way, the heater 12 is positioned on the heat conductive member 7. The heater 12 is thermally connected to a plurality of heat conductive members 5 to 9. The heater 12 has a heating region 12a that generates heat when electricity is applied. The heating region 12a is a layered region with the Y direction as the thickness direction, and the shape of the heating region 12a when viewed from the Y direction is, for example, rectangular. Details of the heating region 12a will be described later.

[0039] When viewed from the Y direction, which is the direction in which the main body 11a and the heat conduction member 7 overlap, the center C of the heating region 12a overlaps with the heat conduction member 7 and is shifted from the optical path P of the laser beam L in the Z direction, which is the direction intersecting the Y direction. In other words, when viewed from the Y direction, the center C of the heating region 12a is away from the optical path P of the laser beam L in the Z direction. In this example, when viewed from the Y direction, the center C of the heating region 12a is shifted to one side in the Z direction from the optical path P of the laser beam L by a distance greater than or equal to the width (thickness) W of the heat conduction member 7 in the Y direction. When viewed from the Y direction, the heating region 12a is located on the heat conduction member 7, spanning the first part 71 and the second part 72 of the heat conduction member 7, and the center C of the heating region 12a overlaps with the second part 72 of the heat conduction member 7. That is, the center C of the heating region 12a is located on the second part 72 of the heat conduction member 7. The first part 71 is the part of the heat conduction member 7 located on the main body 11a. The second portion 72 is the portion of the heat conductive member 7 that extends from the first portion 71 to one side in the Z direction. In the second portion 72, a gap is formed between the surface 7b on the cell 11 side of the heat conductive member 7 and the outer surface of the protrusion 11b. The center C of the heating region 12a refers to the centroid of the shape of the heating region 12a when viewed from the Y direction. In this embodiment, the entire heating region 12a is shifted to one side in the Z direction from the optical path P of the laser beam L (there is no overlapping region when viewed from the Y direction), but the heating region 12a may have a region that overlaps with the optical path P when viewed from the Y direction to the extent that the effect of noise can be suppressed. For example, the other end 12b of the heating region 12a in the Z direction may overlap with the optical path P when viewed from the Y direction.

[0040] Furthermore, when viewed from the Y direction, the entire heating region 12a is shifted to one side in the Z direction from the optical path P of the laser beam L, and at least a portion of the heating region 12a is located inside the main body 11a. Specifically, when viewed from the Y direction, the other end 12b of the heating region 12a in the Z direction is shifted to one side in the Z direction from the optical path P of the laser beam L and is located inside the main body 11a. In this embodiment, the entire heating region 12a is arranged on the heat conductive member 7.

[0041] As shown in Figure 9, the heater 12 includes a pair of first electrode sections 121a and 121b, a pair of second electrode sections 122a and 122b, a first heating element 123, and a second heating element 124. One end of the first heating element 123 is connected to the first electrode section 121a, and the other end of the first heating element 123 is connected to the first electrode section 121b. One end of the second heating element 124 is connected to the second electrode section 122a, and the other end of the second heating element 124 is connected to the second electrode section 122b. The first heating element 123 and the second heating element 124 are heating elements (resistors such as metal wires) that generate heat when an electric current is passed through them.

[0042] In this example, a pair of first electrode portions 121a and 121b are aligned in the X direction. The first heating wire 123 extends from the first electrode portion 121a to the other side in the Z direction in a meander or zigzag pattern, and extends from the other side in the Z direction to the first electrode portion 121b in a meander or zigzag pattern. Similarly, a pair of second electrode portions 122a and 122b are aligned in the X direction. The second heating wire 124 extends from the second electrode portion 122a to the other side in the Z direction in a meander or zigzag pattern, and extends from the other side in the Z direction to the second electrode portion 122b in a meander or zigzag pattern.

[0043] The first heating element 123 and the second heating element 124 extend side by side. That is, the first heating element 123 and the second heating element 124 are separated from each other in a predetermined direction and overlap when viewed from that predetermined direction. In this example, the first heating element 123 and the second heating element 124 are separated from each other in the Y direction and overlap when viewed from the Y direction. The first heating element 123 and the second heating element 124 are electrically insulated from each other, for example, by covering each with a heat-resistant and electrically insulating sheet (not shown). In the heater 12, the heating region 12a is defined by the first heating element 123 and the second heating element 124. In this example, the heating region 12a is a rectangular parallelepiped region of minimum volume that includes the first heating element 123 and the second heating element 124 extending in a meander or zigzag pattern.

[0044] When the heater 12 is operating, current flows through the first heating element 123 from the first electrode portion 121a to the first electrode portion 121b, and current flows through the second heating element 124 from the second electrode portion 122b to the second electrode portion 122a. As a result, in the parts that overlap each other when viewed from the Y direction (i.e., the parts that are side by side), the direction of the current flowing through the first heating element 123 and the direction of the current flowing through the second heating element 124 are opposite. In this way, the first heating element 123 and the second heating element 124 generate heat due to the current flowing in opposite directions. At this time, the magnetic field generated in the first heating element 123 and the magnetic field generated in the second heating element 124 due to the current cancel each other out. For this to happen, the distance between the parts of the first heating element 123 and the second heating element 124 that are side by side is 1 mm or less. [Mechanism of Action and Effects]

[0045] In cell unit 2, the outer surface 111a of the wall portion 111 through which the laser beam L passes is covered with a heat conductive member 5 that is transparent to the laser beam L. Similarly, the outer surface 112a of the wall portion 112 through which the laser beam L passes is covered with a heat conductive member 6 that is transparent to the laser beam L. As a result, the heat generated in the heater 12 is transferred to the respective wall portions 111 and 112 via the respective heat conductive members 5 and 6, thereby suppressing a relative decrease in the temperature of the respective wall portions 111 and 112 through which the laser beam L passes when the heater 12 is operating. Therefore, cell unit 2 can appropriately suppress the deposition of alkali metals on the inner surfaces of the respective wall portions 111 and 112 through which the laser beam L passes when the heater 12 is operating. Furthermore, since each heat conduction member 5, 6 is made of a non-conducting material, it is possible to suppress the generation of magnetic noise in each heated heat conduction member 5, 6 compared to, for example, the case where each heat conduction member 5, 6 is made of a conductive material.

[0046] In cell unit 2, each heat conductive member 5, 6 is formed from sapphire. This makes it possible to obtain each heat conductive member 5, 6 that ensures both heat transfer and light transmission.

[0047] In cell unit 2, the thickness of each heat conductive member 5 and 6 in the X direction through which the laser beam L passes is 0.1 mm or more and 1 mm or less. By making the thickness of each heat conductive member 5 and 6 0.1 mm or more, sufficient heat transfer can be ensured, and by making the thickness of each heat conductive member 5 and 6 1 mm or less, the size of cell unit 2 can be suppressed.

[0048] In cell unit 2, the adhesive layer 16 is light-transmitting. This ensures heat transfer and light transmission between the main body 11a of cell 11 and the heat conductive member 5, and between the main body 11a and the heat conductive member 6.

[0049] In the cell unit 2, a heat conductive member 7 made of a non-conducting material is placed on the main body portion 11a of the cell 11, and the heater 12 is placed on the heat conductive member 7. This allows the heat generated by the heater 12 to be efficiently transferred to the main body portion 11a of the cell 11 via the heat conductive member 7. Furthermore, because the heat conductive member 7 is made of a non-conducting material, it is possible to suppress the generation of magnetic noise in the heated heat conductive member 7 compared to, for example, a case where the heat conductive member 7 is made of a conductive material.

[0050] In the cell unit 2, the heat conductive member 7 is made of sapphire or alumina. This makes it possible to obtain a heat conductive member 7 that ensures at least heat transfer properties.

[0051] In cell unit 2, heat conduction member 5 and heat conduction member 7 are in contact with each other, and heat conduction member 6 and heat conduction member 7 are in contact with each other. Alternatively, heat conduction member 5 and heat conduction member 7 are joined to each other via an adhesive layer 16, and heat conduction member 6 and heat conduction member 7 are joined to each other via an adhesive layer 16. In either case, heat is directly transferred between each heat conduction member 5, 6 and heat conduction member 7, so that the heat generated in heater 12 can be efficiently transferred to the main body 11a of cell 11.

[0052] In cell unit 2, a heat conduction member 7 is positioned on the main body portion 11a of cell 11, and the heater 12 is positioned on the heat conduction member 7 such that, when viewed from the Y direction, the center C of the heating region 12a of the heater 12 overlaps with the heat conduction member 7. This allows the heat generated by the heater 12 to be efficiently transferred to the main body portion 11a of cell 11 via the heat conduction member 7. Furthermore, since the heat conduction member 7 is made of a non-conducting material, it is possible to suppress the generation of magnetic noise in the heated heat conduction member 7 compared to, for example, when the heat conduction member 7 is made of a conductive material. Moreover, when viewed from the Y direction, the center C of the heating region 12a of the heater 12 is shifted from the optical path P of the laser beam L in the Z direction, so the influence of magnetic noise generated in the heating region 12a due to current flow can be suppressed. Therefore, cell unit 2 allows for efficient transfer of heat generated by the heater 12 to the main body portion 11a of cell 11 while suppressing the influence of magnetic noise on measurements in the main body portion 11a of cell 11.

[0053] In the cell unit 2, the main body 11a of the cell 11 is covered by a plurality of heat conductive members 5 to 9. This allows the heat generated in the heater 12 to be efficiently transferred to the main body 11a of the cell 11 via the plurality of heat conductive members 5 to 9, enabling uniform heating of the main body 11a. Furthermore, since each heat conductive member 5 to 9 is made of an insulated material, the generation of magnetic noise in each heated heat conductive member 5 to 9 can be suppressed.

[0054] In cell unit 2, when viewed from the Y direction, the center C of the heating region 12a is shifted from the optical path P of the laser beam L in the Z direction by more than the width W of the heat conductive member 7 in the Y direction. This ensures that the effects of magnetic noise generated in the heating region 12a by the application of current are reliably suppressed.

[0055] In cell unit 2, when viewed from the Y direction, the entire heating region 12a is shifted in the Z direction from the optical path P of the laser beam L. This makes it possible to more reliably suppress the effects of magnetic noise generated in the heating region 12a by the application of current.

[0056] In the cell unit 2, when viewed from the Y direction, the entire heating region 12a is shifted from the optical path P of the laser beam L in the Z direction, and the end 12b of the heating region 12a is located inside the main body 11a. This allows for more efficient transfer of heat generated in the heater 12 to the main body 11a, while also suppressing the influence of magnetic noise on measurements in the main body 11a.

[0057] In cell unit 2, the protrusion 11b in cell 11 extends from the main body 11a to one side in the Z direction, and the center C of the heating region 12a is shifted to one side in the Z direction from the optical path P of the laser beam L. This makes it possible to suppress the increase in the area of ​​cell unit 2 when viewed from the Y direction.

[0058] In the cell unit 2, the center C of the heating region 12a is positioned on the second portion 72. This ensures a heat transfer path while keeping the center C of the heating region 12a of the heater 12 away from the optical path P of the laser beam L, thereby reliably suppressing the effects of magnetic noise generated in the heating region 12a due to the application of power.

[0059] In the cell unit 2, the heater 12 has a first heating element 123 and a second heating element 124 that define the heating region 12a, and these two heating elements generate heat when current is passed in the opposite direction. As a result, the magnetic field generated in the first heating element 123 and the magnetic field generated in the second heating element 124 cancel each other out, thus suppressing the generation of magnetic noise in the heating region 12a when current is passed.

[0060] In the example where the main body 11a of cell 11 was not covered by any material, the sensitivity was 45.1 fT / rtHz under predetermined conditions. In contrast, in the example where the main body 11a of cell 11 was covered with aluminum foil, the sensitivity was 147 fT / rtHz under the same predetermined conditions. This indicates that when the main body 11a of cell 11 is covered with a conductive material, magnetic noise increases relative to the signal, and sensitivity decreases. Furthermore, in the example where the main body 11a of cell 11 was not covered by any material, the temperature difference generated in the main body 11a under predetermined conditions was 23.5°C. In contrast, in the example where the main body 11a of cell 11 was covered with multiple heat conductive members 5-9, the temperature difference generated in the main body 11a under the same predetermined conditions was 10.5°C. This indicates that when the main body 11a of cell 11 is covered with multiple heat conductive members 5-9, the main body 11a is heated sufficiently uniformly. [Differentiation]

[0061] The present invention is not limited to the examples described above. For example, as shown in Figures 10(a) and (b), the main body 11a of the cell 11 may be composed of an intermediate member 117 and a pair of light-transmitting members 118, 119. Figure 10(a) is a cross-sectional view perpendicular to the Z direction, and Figure 10(b) is a cross-sectional view perpendicular to the X direction.

[0062] In the examples shown in Figures 10(a) and (b), the intermediate member 117 has a pair of surfaces 117a and 117b facing each other in the X direction, and through holes 117c opening in each surface 117a and 117b. The intermediate member 117 is formed in the shape of a rectangular frame, for example, from silicon. The light-transmitting member 118 is positioned on surface 117a of the intermediate member 117 and covers the through holes 117c from one side in the X direction. The light-transmitting member 119 is positioned on surface 117b of the intermediate member 117 and covers the through holes 117c from the other side in the X direction. Each light-transmitting member 118, 119 is formed in the shape of a rectangular plate, for example, from glass. The intermediate member 117 and the light-transmitting member 118 are joined, for example, by anodic bonding or direct bonding. Similarly, the intermediate member 117 and the light-transmitting member 119 are joined, for example, by anodic bonding or direct bonding. The sides of the intermediate member 117 and the pair of light-transmitting members 118 and 119 are flush with each other and constitute the side surface 11c of the main body 11a.

[0063] In the examples shown in Figures 10(a) and (b), the heat conduction member 5 is located on the outer surface 118a of the light-transmitting member 118 opposite to the intermediate member 117. The heat conduction member 6 is located on the outer surface 119a of the light-transmitting member 119 opposite to the intermediate member 117. The heater 12 is located on one side surface 11c of the main body 11a in the Y direction. The heat conduction member 8 is located on the other side surface 11c of the main body 11a in the Y direction. The heat conduction member 10 is located on one side surface 11c of the main body 11a in the Z direction. The heat conduction member 9 is located on the other side surface 11c of the main body 11a in the Z direction.

[0064] Even in a cell unit 2 having the main body portion 11a of the cell 11 as described above, when the heater 12 is in operation, the deposition of alkali metals on the inner surfaces of the light-transmitting members 118, 119, which are the walls through which the laser light L passes, can be appropriately suppressed.

[0065] Not limited to the examples described above, when viewed from the Y direction, the center C of the heating region 12a of the heater 12 may be shifted in a direction other than "one side in the Z direction" from the optical path P of the laser beam L, or it may overlap with the optical path P of the laser beam L. Each heat conductive member 5, 6 may be formed of an "insulated material that is transparent to the laser beam L" other than sapphire. Each heat conductive member 7~9 may be formed of an insulated material other than sapphire and alumina. Each heat conductive member 7~9 does not have to be an insulated material; for example, it may be a semiconductor material or a conductive material. Each heat conductive member 5~9 does not have to be entirely placed on the main body 11a of the cell 11, and it is sufficient if at least a part of each is placed on the main body 11a of the cell 11. The thickness of each heat conductive member 5~9 may be less than 0.1 mm or greater than 1 mm.

[0066] In the example described above, the entire heating region 12a of the heater 12 was placed on the heat conductive member 7, but it is sufficient if at least a portion of the heating region 12a is placed on the heat conductive member 7. In this case, the center C of the heating region 12a does not have to overlap with the heat conductive member 7. The heat conductive members 5 and 6 do not have to be transparent to the laser light L. In this case, the heat conductive members 5 and 6 may have windows to allow the laser light L to pass through.

[0067] In the example described above, the sensor module 1 was configured as a one-laser system in which the laser light L served as both the pump light and the probe light. However, as shown in the modified example in Figure 11, the sensor module 1 may be configured as a two-laser system in which the pump light L1 and the probe light L2 are independent. The modified sensor module 1 includes a light source 21A that outputs linearly polarized pump light L1 and a light source 21B that outputs circularly polarized probe light L2, instead of the light source 21. Furthermore, in the modified sensor module 1, the photodetector 25 is configured as a differential detector consisting of a first photodetector 25A and a second photodetector 25B.

[0068] In the modified sensor module 1, the alkali metal vapor in cell 11 is brought into a spin-polarized state by optical pumping using pump light L1 output from light source 21A. Probe light L2 output from light source 21B and passing through cell 11 is detected by photodetector 25. Here, since the spin-polarized state of the alkali metal vapor in cell 11 changes under the influence of the magnetic field of the object being measured, the polarization direction of the probe light L2 that has passed through the alkali metal vapor is changed to tilt. The first photodetector 25A detects the intensity of the light component in the deflection direction corresponding to the polarization direction of the probe light L2 before the polarization direction change, and the second photodetector 25B detects the intensity of the light component in the deflection direction corresponding to the polarization direction of the probe light L2 after the polarization direction change. This allows for the detection of the difference in light intensity between the two polarization direction components of the probe light L2. Based on this difference, the spin-polarized state of the alkali metal vapor in cell 11 can be detected, and consequently, changes in the magnetic field of the object being measured can be detected. In the two-laser system, for example, the probe light L2 passes through the main body 11a of the cell 11 along the X direction. The pump light L1 passes through the main body 11a of the cell 11 along the Y direction.

[0069] The cell unit 2 is not limited to optically pumped magnetic sensors like the sensor module 1, but can also be applied to other devices such as atomic clocks. [Explanation of Symbols]

[0070] 2...Cell unit, 5,6...Heat conductive member (first heat conductive member), 7...Heat conductive member (second heat conductive member), 11...Cell, 11a...Main body, 12...Heater, 16...Adhesive layer, 111,112...Wall section, 111a,112a...Outer surface, L...Laser light (light).

Claims

1. The main body, through which light passes, contains a cell containing alkali metals, A first heat conductive member, at least a portion of which is disposed on the main body, The device comprises a heater thermally connected to the first heat conductive member, The first heat conductive member covers the outer surface of the wall portion of the main body through which the light passes, and is transparent to the light, in the cell unit.

2. The cell unit according to claim 1, wherein the first heat conductive member is formed of sapphire.

3. The cell unit according to claim 1 or 2, wherein the thickness of the first heat conductive member in the direction through which the light passes is 0.1 mm or more and 1 mm or less.

4. The main body and the first heat conductive member are joined to each other via the first adhesive layer. The cell unit according to claim 1 or 2, wherein the first adhesive layer is transparent to light.

5. The system further comprises a second heat conductive member, at least a portion of which is disposed on the main body, The cell unit according to claim 1, wherein the heater is disposed on the second heat conductive member.

6. The cell unit according to claim 5, wherein the second heat conductive member is formed of sapphire or alumina.

7. The cell unit according to claim 5 or 6, wherein the first heat conductive member and the second heat conductive member are in contact with each other or are joined to each other via a second adhesive layer.

Images