JP2018198136A - Negative ion source device - Google Patents

Abstract

To provide a negative ion source device capable of accurately detecting a remaining quantity of cesium that is stored in a cesium supply part.SOLUTION: A cesium supply part 130 comprises: a conductive part 137 that is provided inside of a storage part 131; and a voltage application part 138 capable of applying a voltage between the conductive part 137 and the storage part 131. In a state where the conductive part 137 is contact with cesium C, inside of the storage part 131, a current path in which a current flows is formed from the conductive part 137, cesium C and the storage part 131. Resistance of the current path is changed by decreasing a remaining quantity of cesium C, thereby changing a relation of the voltage, the current and the resistance in the case where the voltage is applied by the voltage application part 138. Therefore, a remaining quantity detection part 150 measures the voltage, the current or the resistance between the conductive part 137 and the storage part 131, thereby detecting the remaining quantity of cesium C within the storage part 131 based on a measurement result.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a negative ion source device.

  As a negative ion source device used for an accelerator or the like, for example, a device described in Patent Document 1 is known. In the negative ion source device of Patent Document 1, a raw material gas is supplied into a chamber, and negative ions are generated by generating plasma in the chamber. Further, cesium is supplied to such a chamber as a promoting substance that promotes the generation of negative ions.

  Cesium is stored in a container outside the chamber, and cesium is supplied from the container into the chamber. Since the container is surrounded by a heating device and a heat insulating material, the remaining amount of cesium in the container cannot be grasped visually from the outside. Therefore, it is necessary to measure the remaining amount of cesium in the container. As described above, a method described in Patent Document 2 is known as a method for detecting the remaining amount of cesium in a container. In Patent Document 2, the remaining amount of cesium in a container is detected using a magnet.

JP, 2006-134281, A JP 2000-098070 A

  Here, when supplying cesium to the chamber of the negative ion source device, it is necessary to supply the cesium in a state of being heated and vaporized in the cesium supply unit. Thus, when the remaining amount is detected using a magnet at a high temperature accompanied by heating, there is a problem that the remaining amount of cesium cannot be accurately detected because the magnetic field changes.

  Accordingly, an object of the present invention is to provide a negative ion source device that can accurately detect the remaining amount of cesium stored in a cesium supply unit.

  A negative ion source device according to the present invention includes a negative ion generation unit that generates negative ions, a cesium supply unit that supplies cesium to the negative ion generation unit, and a remaining amount detection unit that detects the remaining amount of cesium in the cesium supply unit The cesium supply unit is provided with a storage unit that stores cesium, a heating unit that heats the storage unit, and a conductive unit that is provided inside the storage unit and is made of a conductive material and insulated from the storage unit. And a voltage applying unit capable of applying a voltage between the conductive unit and the storage unit, the remaining amount detection unit measures the voltage, current, or resistance between the conductive unit and the storage unit, and the measurement result Based on the above, the remaining amount of cesium in the reservoir is detected.

  In the negative ion source device according to the present invention, the cesium supply unit includes a conductive unit provided inside the storage unit, and a voltage applying unit capable of applying a voltage between the conductive unit and the storage unit. . The conductive portion is a member made of a conductive material and insulated from the storage portion. Here, cesium stored in the storage part is also a conductive substance. Therefore, if the conductive part is in contact with cesium in the storage part, a current path through which a current flows is formed by the conductive part, cesium, and the storage part. When the voltage application unit applies a voltage between the conductive unit and the storage unit in this state, a current corresponding to the resistance of the current path flows through the current path. From such a state, when the amount of contact between the conductive part and cesium changes due to a decrease in the remaining amount of cesium in the storage part, the resistance of the current path changes. Alternatively, when the conductive part is separated from cesium, the current path is disconnected. In this case, the relationship between the voltage, current, and resistance when the voltage is applied by the voltage applying unit changes. Therefore, the remaining amount detection unit can detect the remaining amount of cesium in the storage unit based on the measurement result by measuring the voltage, current, or resistance between the conductive unit and the storage unit. As described above, the remaining amount of cesium stored in the cesium supply unit can be accurately detected.

  In the negative ion source device, the conductive portion may extend in the vertical direction within the storage portion. In this case, the amount of contact between the conductive portion and cesium gradually decreases as the remaining amount of cesium in the storage portion decreases and the liquid level decreases in the vertical direction. That is, the resistance of the current path formed by the conductive part, cesium, and the storage part changes continuously. Therefore, the remaining amount detection unit can continuously detect the remaining amount of cesium.

  In the negative ion source device, the storage unit includes a bottom wall, a side wall, and a lid, the conductive unit passes through the lid, and the lid has a bottom surface disposed on the inner side of the storage unit. The bottom surface may have a height difference in the vertical direction. In the storage part, the stored cesium is vaporized, so that cesium adheres to the bottom surface of the lid. In this case, there is a possibility that the detection accuracy is affected by the contact of the conductive portion with cesium near the lid. On the other hand, since the bottom surface of the lid body has a height difference in the vertical direction, cesium attached to the bottom surface can flow to a low position. Thereby, it can suppress that a cesium and an electroconductive part contact in the cover body vicinity.

  ADVANTAGE OF THE INVENTION According to this invention, the negative ion source apparatus which can detect correctly the residual amount of the cesium currently stored by the cesium supply part can be provided.

It is the schematic which shows a neutron capture therapy apparatus provided with the negative ion source apparatus which concerns on embodiment of this invention. It is a schematic sectional drawing of a negative ion source apparatus. It is a schematic sectional drawing which shows the structure of the storage part of a cesium supply part. It is a schematic sectional drawing which shows the structure of the storage part of a cesium supply part. It is a schematic sectional drawing which shows the structure of the storage part of a cesium supply part.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, taking the neutron capture therapy apparatus 1 including the negative ion source apparatus 100 according to the embodiment of the present invention as an example, an outline of the neutron capture therapy apparatus 1 will be described with reference to FIG. A neutron capture therapy device 1 shown in FIG. 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). In the neutron capture therapy apparatus 1, for example, a neutron beam N is irradiated to a tumor of a patient (irradiated body) 50 to which boron ( ¹⁰ B) is administered.

  The neutron capture therapy apparatus 1 includes an accelerator 2. The accelerator 2 accelerates charged particles such as negative ions and emits a charged particle beam R. The accelerator 2 is configured by, for example, a cyclotron. In the present embodiment, the charged particle beam R is a proton beam generated by stripping charges from negative ions. The accelerator 2 generates a charged particle beam R having a beam radius of 40 mm and 60 kW (= 30 MeV × 2 mA), for example. The accelerator is not limited to a cyclotron, and may be a synchrotron, a synchrocyclotron, a linac, an electrostatic accelerator, or the like.

  The charged particle beam R emitted from the accelerator 2 is sent to the neutron beam generation unit M. The neutron beam generation unit M includes a beam duct 9 and a target 10. The charged particle beam R emitted from the accelerator 2 passes through the beam duct 9 and travels toward the target 10 disposed at the end of the beam duct 9. A plurality of quadrupole electromagnets 4, a current monitor 5, and a scanning electromagnet 6 are provided along the beam duct 9. The plurality of quadrupole electromagnets 4 adjust the beam axis of the charged particle beam R using, for example, an electromagnet.

  The current monitor 5 detects the current value of the charged particle beam R irradiated to the target 10 (that is, charge and irradiation dose rate) in real time. The current monitor 5 uses a non-destructive DCCT (DC Current Transformer) that can measure current without affecting the charged particle beam R. The current monitor 5 outputs the detection result to a control unit (not shown) described later. “Dose rate” means a dose per unit time.

  The scanning electromagnet 6 scans the charged particle beam R and controls irradiation of the charged particle beam R to the target 10. The scanning electromagnet 6 controls the irradiation position of the charged particle beam R with respect to the target 10.

  The neutron capture therapy apparatus 1 generates a neutron beam N by irradiating the target 10 with the charged particle beam R, and emits the neutron beam N toward the patient 50. The neutron capture therapy apparatus 1 includes a target 10, a shield 8, a moderator 39, and a collimator 20.

  The target 10 generates a neutron beam N when irradiated with the charged particle beam R. The target 10 here is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a disk shape with a diameter of, for example, 160 mm. Note that the target 10 is not limited to a disk shape, and may have another shape. Further, the target 10 is not limited to a solid, but may be a liquid (liquid metal).

  The moderator 39 decelerates the neutron beam N generated by the target 10 (decreases the energy of the neutron beam N). The moderator 39 may have a laminated structure including a layer 39A that mainly decelerates fast neutrons contained in the neutron beam N and a layer 39B that mainly decelerates epithermal neutrons contained in the neutron beam N. .

  The shield 8 shields the generated neutron beam N and the gamma rays generated by the generation of the neutron beam N so as not to be emitted to the outside. The shield 8 is provided so as to surround the moderator 39. The upper part and the lower part of the shield 8 extend upstream of the charged particle beam R from the moderator 39.

  The collimator 20 shapes the irradiation field of the neutron beam N, and has an opening 20a through which the neutron beam N passes. The collimator 20 is a block-shaped member having an opening 20a at the center, for example.

  Next, the configuration of the negative ion source device 100 will be described with reference to FIG. The negative ion source device 100 includes a negative ion generation unit 102, a vacuum box 104, a cesium supply unit 130, and a remaining amount detection unit 150. The negative ion generator 102 and the vacuum box 104 are connected by an insulating flange 106. The cesium supply unit 130 is connected to the negative ion generation unit 102 at a position opposite to the vacuum box 104.

  The negative ion generation unit 102 includes a chamber 108, a source gas supply unit 109, a magnet 110, a plasma generation unit 112, and a plasma electrode 116.

  The chamber 108 is connected to a vacuum pump (not shown) and can hold the inside in a vacuum state. The chamber 108 has a cylindrical main body 108a and a lid 108b provided on the other end of the main body 108a. The main body 108 a forms the side wall of the chamber 108. On one end side of the chamber 108, a plasma generation unit 112 and a vacuum box 104 described later are provided. At both ends of the main body portion 108a, flange portions 108c and 108d that protrude outward are provided. The lid portion 108b is detachably attached to the flange portion 108c located on the other end side of the main body portion 108a, and opens or closes the other end (open end) of the main body portion 108a.

  The source gas supply unit 109 includes a pipe 116b provided in the vicinity of a plasma electrode 116, which will be described later, and a gas supply source 122 connected to the pipe 116b. The pipe 116 b is located on the other end side of the chamber 108. The gas supply source 122 includes a source gas source (hydrogen gas source) and an inert gas source (argon gas source). That is, the source gas and the inert gas from the gas supply source 122 are supplied into the chamber 108 from the other end side of the main body 108a through the pipe 116b.

  The magnet 110 includes a plasma confinement unit 110A and a filter magnetic field generation unit 110B. The plasma confinement part 110 </ b> A is provided in a region on the other end side of the chamber 108. The plasma confinement unit 110 </ b> A generates a magnetic field so that the plasma generated in the chamber 108 is confined in the chamber 108. The filter magnetic field generation unit 110B is provided on one end side of the chamber 108 and generates a magnetic field that blocks electrons having a predetermined energy or higher. In the axial direction of the chamber 108, the plasma confinement unit 110A occupies a wider range than the filter magnetic field generation unit 110B. High energy electrons (hot electrons) cannot penetrate into the magnetic field region generated by the filter magnetic field generation unit 110B, but are confined in the region surrounded by the plasma confinement unit 110A. This region is referred to as a plasma generation region E1 (region on the left side of the alternate long and short dash line shown in FIG. 2). On the other hand, electrons having lower energy than the predetermined energy (cold electrons) can pass through the magnetic field region surrounded by the filter magnetic field generation unit 110B. Negative ions are easily destroyed by high-temperature electrons, but high-temperature electrons are prevented from entering the magnetic field region of the filter magnetic field generation unit 110B and low-temperature electrons are allowed to enter. Generated. Therefore, the magnetic field region by the filter magnetic field generation unit 110B is referred to as a negative ion generation region E2 (a region on the right side of the dashed line shown in FIG. 2).

  A plurality of magnets 110 are arranged on the outer peripheral surface side of the main body portion 108a. More specifically, the magnet 110 is located on the outer peripheral side of the chamber 108 in a state of being separated from the outer peripheral surface of the main body 108a. The plasma confinement part 110A is configured by alternately arranging the south pole and the north pole in the circumferential direction. The filter magnetic field generation unit 110B collects and arranges the S poles in a partial region in the circumferential direction, and collects and arranges the N poles in other regions in the circumferential direction. A cooling path (not shown) is provided between the magnet 110 and the outer peripheral surface of the main body 108a. In order to cool the magnet 110 or the wall portion of the main body 108a, a coolant such as water is circulated in the cooling path. The position where the cooling path is provided is not limited to the position between the magnet 110 and the outer peripheral surface of the main body 108a, but may be another position. For example, a cooling path may be provided on the outer peripheral surface of the magnet 110.

  The plasma generation unit 112 includes a filament 112a and a pair of electrodes 112b. The pair of electrodes 112b is provided on the lid portion 108b and is connected to the filament 112a. The electrode 112 b is connected to a current supply bus bar 112 c drawn out of the chamber 108. The current supply bus bar 112c is connected to a power source (not shown). Accordingly, the pair of electrodes 112b applies a voltage and a current to the filament 112a to cause the filament 112a to generate heat, and also causes a potential difference between the filament 112a and the chamber 108 (main body portion 108a).

  The plasma electrode 116 is disposed between the insulating flange 125 provided on the flange portion 108d located on one end side of the main body portion 108a and the insulating flange 106 on the vacuum box 104 side. The plasma electrode 116 is connected to a power source (not shown) having a variable voltage. By controlling the power supply to control the magnitude of the voltage applied to the plasma electrode 116, the plasma distribution in the chamber 108 is controlled, and the amount of negative ions extracted from the chamber 108 is controlled. The plasma electrode 116 has an extraction hole 116a through which negative ions generated in the chamber 108 can be extracted to the outside of the chamber 108 (in this embodiment, the vacuum box 104 side). In addition, although the plasma electrode 116 which concerns on this embodiment is flat plate shape, a shape is not specifically limited, You may be comprised by the taper shape etc.

  The vacuum box 104 is located on the downstream side of the chamber 108 from which the negative ion beam is extracted (one end side of the chamber 108). The vacuum box 104 can hold the inside in a vacuum state, like the chamber 108. In the vacuum box 104, an electrode 124 such as an extraction electrode, a Faraday cup (not shown) for measuring the beam amount of the negative ion beam, a steering coil (not shown) for changing the trajectory of the negative ion beam, and the like are arranged. ing.

  The cesium supply unit 130 supplies cesium to the negative ion generation unit 102. The cesium supply unit 130 includes a storage unit 131, introduction units 132 and 133, a valve 134, and a heating unit 136.

  The storage part 131 is a container for storing cesium. Cesium is stored in the storage unit 131 in a liquid state. The reservoir 131 is disposed outside the chamber 108. The storage part 131 is provided with the bottom wall 141, the side wall 142, and the cover body 143 (refer FIG. 3). The side wall 142 extends upward from the peripheral edge of the bottom wall 141. The lid 143 is provided so as to seal the opening at the upper end of the side wall 142. In addition, the shape of the storage part 131 is not specifically limited, A columnar shape may be sufficient, and polygonal column shapes, such as square column shape, may be sufficient.

  The introduction parts 132 and 133 are members extending from the storage part 131 toward the chamber 108. The introduction units 132 and 133 introduce cesium that is vaporized by heating and flows out of the storage unit 131 into the chamber 108. A valve 134 is provided between the introduction part 132 and the introduction part 133. The valve 134 can adjust the amount of cesium introduced from the reservoir 131 into the chamber 108.

  The heating unit 136 is a member that heats the storage unit 131. The heating part 136 includes a wall part that houses the storage part 131 and a heater provided on the wall part. Members constituting the heating unit 136 are also provided around the introduction units 132 and 133 and the valve 134. The heating unit 136 performs heating at a timing when the cesium supply unit 130 supplies cesium to the negative ion generation unit 102 based on a control signal from a control unit (not shown). The heated cesium becomes a gas and is supplied to the chamber 108 in the state of the gas.

  Next, a more detailed configuration of the cesium supply unit 130 and the remaining amount detection unit 150 will be described with reference to FIG. As shown in FIG. 3, the cesium supply unit 130 further includes a conductive unit 137 and a voltage applying unit 138. The liquid cesium stored in the storage unit 131 may be referred to as “cesium C”.

  The conductive part 137 is provided inside the storage part 131. In addition, the conductive part 137 is drawn out of the storage part 131. In the present embodiment, the conductive portion 137 extends in the vertical direction within the storage portion 131. The conductive portion 137 is a member that extends downward from the outside of the storage portion 131, passes through the lid 143, and extends toward the bottom wall 141. The conductive part 137 is a rod-shaped member. However, the shape of the conductive portion 137 is not particularly limited, and may be a long flat plate-like member.

  The lower end portion 137a of the conductive portion 137 is spaced upward from the bottom wall 141. The lower end portion 137a of the conductive portion 137 is disposed below the liquid surface F of the cesium C in a state where the remaining amount of cesium C is sufficient (the state shown in FIGS. 3 and 4). On the other hand, in a state where the remaining amount is low until it is necessary to replenish cesium C (the state of FIG. 5), the lower end portion 137a of the conductive portion 137 is disposed above the liquid surface F of the cesium C. The upper end portion 137 b of the conductive portion 137 is disposed above the lid body 143. The position of the upper end portion 137b is not particularly limited as long as a conducting wire portion 161 of a voltage applying portion 138 described later can be pulled out. Note that the conductive portion 137 is disposed at the center position of the storage portion 131 in the horizontal direction. However, the conductive portion 137 may be provided at any position in the horizontal direction as long as it does not contact the side wall 142 of the storage portion 131.

  The conductive portion 137 is made of a conductive material. In addition, the conductive portion 137 has an electric resistance value within a predetermined range. As described above, since the conductive portion 137 has an electric resistance value, an electric resistance value between a terminal 162 and a terminal 164 described later can be changed according to the remaining amount of cesium C. The upper limit value of the resistance of the conductive portion 137 is not particularly limited as long as the current flows to a measurable level. Further, since the conductive portion 137 only needs to have conductivity, the lower limit value of the resistance is not particularly limited, and the electric resistance value of the conductive portion 137 is desirably sufficiently larger than the electric resistance value of cesium C. As a material for the conductive portion 137, for example, tungsten, platinum, nichrome, or the like is used. The conductive portion 137 may be coated to adjust the electric resistance value. Although not particularly limited, an example of the electric resistance value of the conductive portion 137 will be described. For example, when a tungsten rod having a diameter of 1 mm is used as the conductive portion 137 and the height of the liquid level F of cesium C is measured in 1 mm increments, the resistance value change at room temperature corresponding to a change in the height of the liquid level F of 1 mm Is about 67 μΩ when the lead resistance of the cesium C, the storage unit 131, and the voltage applying unit 138 is ignored. Accordingly, the minimum resolution of the resistance value only needs to be 67 μΩ or less, and the minimum resolution of a typical micro-ohmmeter is about 0.1 μΩ, so that sufficient measurement is possible.

  The conductive part 137 is insulated from the storage part 131. Each wall portion of the storage portion 131 is made of a conductive material at least part of the portion where cesium C is stored. The conductive portion 137 is insulated from a portion made of a conductive material in the storage portion 131. For example, stainless steel or the like may be employed as the conductive material constituting each wall portion of the storage portion 131. Here, “insulation” indicates that a portion where the conductive portion 137 is electrically connected via cesium C which is a conductive liquid is allowed and is insulated at other portions. In the present embodiment, the bottom wall 141, the side wall 142, and the lid 143 of the storage part 131 are all made of a conductive material (except for an insulating part 144 of the lid 143 described later). Therefore, the conductive part 137 is separated from the bottom wall 141, the side wall 142, and the lid 143 of the storage part 131 so as not to contact each other, or is fixed via an insulating member.

  In the present embodiment, the conductive portion 137 penetrates the lid 143. Accordingly, the lid 143 has the insulating portion 144 at a position where the conductive portion 137 penetrates. As a result, the conductive portion 137 comes into contact with only the insulating portion 144 of the storage portion 131 and is thus insulated from the storage portion 131. The material of the insulating portion 144 is not particularly limited as long as it is an insulating material. For example, Kovar glass or the like may be employed.

  The lid body 143 has a bottom surface 143 a disposed on the inner side of the storage part 131. The bottom surface 143a has a height difference in the vertical direction. In the present embodiment, a portion of the bottom surface 143a corresponding to the insulating portion 144 forms a curved surface. The curved surface is curved so as to be convex upward, and is curved gradually toward the lower side from the center position toward the outer periphery. The curved surface may have a dome shape that curves over the entire circumference, or may have an arch shape that curves only in a predetermined direction. However, any shape may be adopted as long as the bottom surface 143a has a difference in height so that the attached water droplets of cesium easily fall downward. For example, the bottom surface 143a may be a curved surface that protrudes downward, may be a conical surface or a polygonal pyramid surface, or may be an inclined surface having an inclined plane.

  The voltage applying unit 138 is a member that can apply a voltage between the conductive unit 137 and the storage unit 131. The voltage application unit 138 includes an extraction unit 138A connected to the conductive unit 137 and an extraction unit 138B connected to the storage unit 131. Accordingly, the voltage applying unit 138 can apply a voltage between the conductive unit 137 and the storage unit 131 by connecting a power source to the drawing unit 138A and the drawing unit 138B.

  The lead portion 138 </ b> A includes a conductor portion 161 that is led out from the conductive portion 137, and a terminal 162 that is provided at an end portion of the conductor portion 161. The conductive wire portion 161 is connected to a portion of the conductive portion 137 that is drawn to the outside from the storage portion 131. Here, the conductive wire portion 161 is connected to the upper end portion 137 b of the conductive portion 137. The lead portion 138 </ b> B includes a lead wire portion 163 that is drawn from the storage portion 131 and a terminal 164 that is provided at an end portion of the lead wire portion 163. The conducting wire portion 163 is drawn from a portion of the storage portion 131 that is electrically connected to the stored cesium C. In the present embodiment, the conductive wire portion 163 may be connected anywhere in the storage portion 131 other than the insulating portion 144, but is connected to the position on the bottom wall 141 side.

  The remaining amount detection unit 150 detects the remaining amount of cesium in the cesium supply unit 130. The remaining amount detection unit 150 measures the voltage, current, or resistance between the conductive unit 137 and the storage unit 131, and detects the remaining amount of cesium C in the storage unit 131 based on the measurement result. The remaining amount detection unit 150 is connected to the terminal 162 and the terminal 164 of the voltage application unit 138. The remaining amount detection unit 150 may include a power source that applies a voltage between the conductive unit 137 and the storage unit 131 via the terminals 162 and 164. Therefore, in the state shown in FIG. 3, a current flows between the lead portion 138 </ b> A and the lead portion 138 </ b> B via the conductive portion 137, cesium C, and the wall portion of the storage portion 131. The current value of the current when a constant voltage is applied changes with a change in resistance between the lead portion 138A and the lead portion 138B. The resistance changes according to the remaining amount of cesium C. Accordingly, the remaining amount detection unit 150 can detect the remaining amount of cesium C based on a change in current value or a change in resistance obtained based on a current value and a voltage value. Alternatively, the voltage value when the voltage is applied so that the current value is constant changes with the change in resistance between the lead portion 138A and the lead portion 138B. The resistance changes according to the remaining amount of cesium C. Therefore, the remaining amount detection unit 150 can detect the remaining amount of cesium C based on a change in voltage value or a change in resistance obtained based on a current value and a voltage value. In particular, when the conductive portion 137 is positioned above the liquid level F of cesium C (state shown in FIG. 5), the resistance value becomes infinite. In this case, the remaining amount detection unit 150 can detect that the remaining amount of cesium C has decreased based on the fact that no current flows or based on the resistance exceeding a predetermined value. As described above, the remaining amount detection unit 150 can detect the remaining amount of cesium C by measuring the voltage, current, or resistance that changes according to the remaining amount of cesium C.

  The remaining amount detection unit 150 may be a stationary type that is installed on a floor or the like while being connected to the terminals 162 and 164. In this case, the remaining amount detection unit 150 may be installed together with a control device that controls the negative ion source device 100. In this case, the remaining amount detection unit 150 can constantly monitor the remaining amount of cesium. For example, the remaining amount of cesium may be automatically measured after the operation of the negative ion source device 100, and the operator may be automatically notified at the maintenance timing. Alternatively, the correlation between the heating time of the heating unit 136 and the amount of decrease in cesium may be measured to automatically estimate the maintenance timing. Or you may employ | adopt the handy type residual amount detection part 150 connected to the terminals 162 and 164 only at the timing which detects a residual amount. In addition, since the general thing is used as the conducting wire parts 161 and 163 and the terminals 162 and 164, it is not necessary to remove the heating part 136 when measuring the remaining amount detecting part 150.

  Next, operations and effects of the negative ion source device 100 according to the present embodiment will be described.

  In the negative ion source device 100 according to the present embodiment, the cesium supply unit 130 is provided with a voltage that can apply a voltage between the conductive unit 137 provided in the storage unit 131 and between the conductive unit 137 and the storage unit 131. Part 138. The conductive portion 137 is a member made of a conductive material and insulated from the storage portion 131. Here, cesium C stored in the storage part 131 is also a conductive substance. Therefore, if the conductive part 137 is in contact with cesium C in the storage part 131 (see FIG. 3), a current path through which a current flows is formed by the conductive part 137, cesium C, and the storage part 131. . In this state, when the voltage applying unit 138 applies a voltage between the conductive unit 137 and the storage unit 131, a current corresponding to the resistance of the current path flows through the current path.

  For example, when the state shown in FIG. 3 is changed to the state shown in FIG. 4 and the remaining amount of cesium C in the storage unit 131 decreases, the liquid level F decreases, and the contact amount between the conductive unit 137 and cesium C changes. To do. Thereby, the resistance of the current path formed by the conductive part 137, the cesium C, and the storage part 131 changes. Furthermore, when the remaining amount of cesium C decreases from the state shown in FIG. 4 to the state shown in FIG. 5, the conductive portion 137 is exposed and separated from the liquid surface F of cesium C. In this case, the resistance between the conductive part 137 and cesium C becomes infinite, and the current path formed by the conductive part 137, cesium C, and the storage part 131 is divided.

  As described above, when the remaining amount of cesium C decreases, the resistance of the current path formed by the conductive part 137, cesium C, and the storage part 131 changes or is divided. When voltage is applied, the relationship between voltage, current, and resistance changes. Therefore, the remaining amount detection unit 150 detects the remaining amount of cesium C in the storage unit 131 based on the measurement result by measuring the voltage, current, or resistance between the conductive unit 137 and the storage unit 131. Can do. As described above, the remaining amount of cesium C stored in the cesium supply unit 130 can be accurately detected.

  In the negative ion source device 100, the conductive portion 137 may extend in the vertical direction within the storage portion 131. In this case, as the remaining amount of cesium C in the storage unit 131 decreases and the liquid level F decreases in the vertical direction, the contact amount between the conductive unit 137 and cesium C gradually decreases. That is, the resistance of the current path formed by the conductive part 137, cesium C, and the storage part 131 changes continuously. Therefore, the remaining amount detection unit 150 can continuously detect the remaining amount of cesium.

  In the negative ion source device 100, the storage unit 131 includes a bottom wall 141, a side wall 142, and a lid 143, the conductive unit 137 passes through the lid 143, and the lid 143 is disposed inside the storage unit 131. It has the bottom face 143a arrange | positioned at the side, and the bottom face 143a may have a height difference in a perpendicular direction. In the storage part 131, the stored cesium C is vaporized, so that cesium adheres to the bottom surface 143a of the lid 143. In this case, the conductive part 137 may come into contact with cesium in the vicinity of the lid 143, which may affect the detection accuracy. For example, in this embodiment, the conductive portion 137 is insulated from the lid 143 by the insulating portion 144, but the conductive portion 137 is electrically connected to a portion outside the insulating portion 144 through cesium attached to the lid 143. May be connected. Accordingly, since the bottom surface 143a of the lid 143 has a height difference in the vertical direction, the cesium C attached to the bottom surface 143a can be flowed to a low position. Thereby, it can suppress that cesium C and the electroconductive part 137 contact in the cover body 143 vicinity.

  The present invention is not limited to the embodiment described above.

  For example, in the above-mentioned embodiment, although the electroconductive part has penetrated the cover body, you may penetrate any wall part of the storage part. For example, you may penetrate a side wall. However, in that case, it is necessary to insulate the storage part and the conductive part by providing an insulating part in the penetrating part. Moreover, in the above-mentioned embodiment, although the electroconductive part was extended | stretched to the perpendicular direction, the method for extending an electroconductive part is not specifically limited. For example, the conductive portion may extend in an oblique direction with respect to the vertical direction, or may extend in the horizontal direction. Alternatively, the conductive portion may be bent or curved to have a plurality of portions extending in different directions. A plurality of conductive parts may be provided in the storage part. For example, a plurality of conductive portions may be provided on the side wall portion of the storage portion at a predetermined pitch in the vertical direction. In this case, each conductive part may extend in the horizontal direction within the storage part. In addition, the voltage application unit may have a terminal for each conductive unit. When such a configuration is adopted, as the remaining amount of cesium in the storage portion decreases, the cesium liquid surface is exposed sequentially from the conductive portion arranged on the upper side. Therefore, the height of the liquid surface of cesium can be detected by grasping the conductive portion exposed from the liquid surface of cesium.

  DESCRIPTION OF SYMBOLS 100 ... Negative ion source apparatus, 102 ... Negative ion production | generation part, 130 ... Cesium supply part, 131 ... Storage part, 136 ... Heating part, 137 ... Conductive part, 138 ... Voltage application part, 141 ... Bottom wall, 142 ... Side wall, 143 ... Lid, 150 ... Remaining amount detection unit.

Claims (3)

A negative ion generator that generates negative ions;
A cesium supply unit for supplying cesium to the negative ion generation unit;
A remaining amount detection unit for detecting the remaining amount of cesium in the cesium supply unit,
The cesium supply unit is
A reservoir for storing the cesium;
A heating unit for heating the storage unit;
A conductive portion provided inside the storage portion, made of a conductive material and insulated from the storage portion;
A voltage application unit capable of applying a voltage between the conductive unit and the storage unit,
The remaining amount detection unit
A negative ion source device that measures a voltage, current, or resistance between the conductive portion and the storage portion, and detects the remaining amount of the cesium in the storage portion based on a measurement result.   The negative ion source device according to claim 1, wherein the conductive part extends in a vertical direction in the storage part. The storage unit includes a bottom wall, a side wall, and a lid,
The conductive part passes through the lid,
The negative ion source device according to claim 1, wherein the lid has a bottom surface disposed on an inner side of the storage unit, and the bottom surface has a height difference in a vertical direction.

Images