JP6430264B2 - Negative ion source device - Google Patents

Description

  The present invention relates to a negative ion source device.

  As an ion source device used for an accelerator or the like, for example, a plasma sputtering type negative ion source device using a solid as a raw material (see Patent Document 1) or a negative ion beam generating a negative ion beam using a gas (for example, hydrogen gas) as a raw material. Ion source devices are known. The latter negative ion source device includes, for example, a chamber, a filament for generating plasma in the chamber, a hydrogen gas supply unit for supplying hydrogen gas into the chamber, and a cesium for supplying cesium vapor into the chamber. A supply source. Since an electric current is passed through the filament, thermoelectrons are emitted from the heated filament and collide with hydrogen gas in the chamber to generate plasma. And the negative ion is produced | generated when the slow electron in plasma or the electron of the plasma electrode surface reacts with a hydrogen molecule, a hydrogen atom, or a hydrogen ion.

  Since the work function is reduced on the surface of the substance to which cesium has adhered, cesium has a function of promoting the generation of negative ions. Therefore, when cesium is supplied into the chamber by the cesium supply source, the amount of negative ions extracted from the negative ion source is increased.

JP 2004-030966 A

  Incidentally, there has been a demand for further increasing the amount of negative ions generated in the negative ion source device as described above. An object of the present invention is to provide a negative ion source device that can increase the amount of negative ions generated.

  A negative ion source apparatus according to the present invention generates a plasma using a chamber that generates negative ions therein, a source gas supply unit that supplies source gas into the chamber, and a source gas supplied by the source gas supply unit A plasma generation unit, a plasma electrode provided on one end side of the chamber and having an extraction hole for drawing out the generated negative ions, a promotion material supply unit for supplying a promotion material for promoting the generation of negative ions into the chamber, A filter magnetic field generation unit that is provided on one end of the chamber and generates a magnetic field that blocks electrons of a predetermined energy or higher, and a magnetic field region in which the magnetic field is generated, and increases the area of the portion to which the accelerating substance is attached. A promoting substance adhesion area increasing portion.

  The negative ion source device according to the present invention includes a filter magnetic field generation unit that generates a magnetic field that blocks electrons of a predetermined energy or higher, and an area of a portion that is provided in a magnetic field region in which the magnetic field is generated and to which a promoting substance is attached. A promoting substance adhesion area increasing portion to be increased. In the magnetic field region by the filter magnetic field generation unit, intrusion of electrons with a predetermined energy or higher is blocked and entry of electrons with a lower energy than the predetermined energy is allowed. Therefore, the high-energy electrons are destroyed in the magnetic field region. Instead, negative ions are generated by low energy electrons. In the surface of the portion where the promoting substance adheres in the magnetic field region, the work function is lowered by the promoting substance, so that the surface of negative ions is generated. Therefore, by providing the promoting substance adhesion area increasing portion in the magnetic field region, the area of the portion where the negative ion surface generation is performed increases. As a result, the amount of negative ions generated can be increased.

  In the negative ion source device according to the present invention, the promoting substance adhesion area increasing portion may be constituted by an uneven portion formed on the surface of the plasma electrode. Thereby, the area which concerns on the surface production | generation of a negative ion can be increased, without using another member.

  In the negative ion source device according to the present invention, the promoting substance adhesion area increasing portion may be configured by a member provided apart from the surface of the plasma electrode. Thereby, even if it does not process a plasma electrode etc., the area which concerns on the surface production | generation of a negative ion can be easily increased by providing another member.

  In the negative ion source device according to the present invention, the member may have a through hole. As a result, atoms, molecules, and electrons for generating negative ions can pass through the through hole of the member and move to the plasma electrode side.

  According to the present invention, the amount of negative ions generated can be increased.

FIG. 1 is a diagram schematically showing a neutron capture therapy apparatus. FIG. 2 is a diagram illustrating the negative ion source device according to the first embodiment. 3A is a view of the plasma electrode as viewed from the axial direction from the inside of the chamber, and FIG. 3B is an enlarged view of a portion indicated by A in FIG. 3A. 4A to 4C are diagrams illustrating an example of the cross-sectional shape of the uneven portion. FIG. 5 is a diagram showing a negative ion source device according to the second embodiment. FIGS. 6A and 6B are diagrams illustrating an example of the configuration of the promoting substance adhesion area increasing member and the support portion. FIG. 7 is a diagram illustrating a negative ion source device according to a modification. FIG. 8 is a diagram illustrating a negative ion source device according to a modification.

  Embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are exemplifications for explaining the present invention and are not intended to limit the present invention to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

[First Embodiment]
First, taking the neutron capture therapy apparatus 1 including the negative ion source apparatus 100 according to the first embodiment of the present invention as an example, an outline of the neutron capture therapy apparatus 1 will be described with reference to FIG. Neutron capture therapy apparatus 1 is boron neutron capture therapy (BNCT: Boron Neutron Capture Therapy) is a device used to perform such as cancer treatment with boron ^{(10 B)} is the tumor patient 50 administration Irradiate neutron beam N.

  The neutron capture therapy apparatus 1 includes a cyclotron 2. The cyclotron 2 is an accelerator that generates a charged particle beam R by accelerating negative ions (also referred to as negative ions) generated by the negative ion source device 100. The cyclotron 2 has a capability of generating a charged particle beam R having a beam radius of 40 mm and 60 kW (= 30 MeV × 2 mA), for example. The neutron capture therapy apparatus 1 is not limited to the cyclotron 2 as an accelerator, and a synchrotron, a synchrocyclotron, a linac, or the like may be used.

  The charged particle beam R emitted from the cyclotron 2 travels toward the target 6 through the beam duct 3. A plurality of quadrupole electromagnets 4 and scanning electromagnets 5 are provided along the beam duct 3. The scanning electromagnet 5 scans the charged particle beam R and controls the irradiation position of the charged particle beam R with respect to the target 6.

  The neutron capture therapy apparatus 1 includes a control unit (calculation means) S. The control unit S is an electronic control unit having a CPU, a ROM, a RAM, and the like, and comprehensively controls the neutron capture therapy apparatus 1.

  The control unit S is connected to a current monitor M that measures in real time the current value of the charged particle beam R irradiated to the target 6 (that is, charge and irradiation dose rate), and neutron capture therapy according to the measurement result. Control of each part of the apparatus 1 is performed. As the current monitor M, for example, a non-destructive DCCT (Direct Current Current Transformer) that can be measured without affecting the charged particle beam R can be used.

  The target 6 receives a charged particle beam R and generates a neutron beam N. The target 6 has a disk shape with a diameter of 160 mm, for example. The target 6 may be formed of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W). The target 6 is not limited to a plate shape (solid) and may be liquid.

  The shield 7 shields the generated neutron beam N and gamma rays generated by the generation of the neutron beam N from being emitted to the outside of the neutron capture therapy apparatus 1. The moderator 8 has a function of decelerating the neutron beam N (attenuating the energy of the neutron beam N). The moderator 8 is configured by laminating first and second moderators 8A and 8B. The first moderator 8A mainly decelerates fast neutrons contained in the neutron beam N. The second moderator 8B mainly decelerates epithermal neutrons contained in the neutron beam N.

  The collimator 9 forms an irradiation field of the neutron beam N (irradiation range in a plane orthogonal to the traveling direction of the neutron beam N), and has an opening 9a through which the neutron beam N passes. The neutron beam N generated by the target 6 passes through the moderator 8 and then partially passes through the opening 9 a of the collimator 9, while the remaining part is shielded by the peripheral part that defines the opening 9 a of the collimator 9. As a result, the neutron beam N that has passed through the collimator 9 is formed into a shape corresponding to the shape of the opening 9a.

  The neutron dose measuring device 10 is a device that measures the dose and dose distribution of the neutron beam N irradiated to the patient 50 on the treatment table 51.

  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 source 102 and a vacuum box 104. The negative ion source 102 and the vacuum box 104 are connected by an insulating flange 106.

  The negative ion source 102 includes a chamber 108, a source gas supply unit 109, a magnet 110, a plasma generation unit 112, a promotion substance supply unit 115, a plasma electrode 116, and a promotion substance adhesion area increase unit 117.

  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. A through hole 108e having a circular shape is formed in a substantially central portion of the lid portion 108b. The through hole 108e communicates the inside and outside of the chamber 108 when the lid portion 108b closes the other 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 generator 112 includes a main body 112a having a cylindrical shape, and a pair of filaments 112b extending outward from the end surface of the main body 112a (the other end of the chamber 108 and the plasma electrode 116). The main body 112a has an outer shape corresponding to the through hole 108e of the lid 108b, and is detachable from the lid 108b (through hole 108e). When the main body portion 112a is attached to the lid portion 108b (through hole 108e), airtightness in the chamber 108 is maintained by interposing an O-ring or the like between the main body portion 112a and the through hole 108e. A DC power supply (not shown) is connected to the main body 112a. The DC power supply applies a voltage and a current to the filament 112b to generate heat, and causes a potential difference between the filament 112b and the chamber 108 (main body portion 108a).

  The accelerating substance supply unit 115 includes an accelerating substance introduction unit 114 that introduces an accelerating substance that promotes the generation of negative ions, and an accelerating substance supply source 118 connected to the accelerating substance introduction unit 114. The accelerating substance introduction part 114 is provided in the lid part 108b so as to penetrate the lid part 108b. The tip of the accelerating substance introducing portion 114 is located in the chamber 108. As the accelerating substance, a substance having an accelerating effect on the generation of negative ions such as cesium and other alkaline substances may be employed. Further, the promoting substance may be supplied into the chamber 108 in any state of gas, liquid, and solid.

  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 promoting substance adhesion area increasing unit 117 is provided in a magnetic field region (negative ion generation region E2) in which a magnetic field is generated, and has a structure that increases the area of the portion to which the promoting substance is attached. As shown in FIG. 3A, in this embodiment, the promoting substance adhesion area increasing portion 117 is obtained when the surface 116c of the plasma electrode 116 (the surface on the inner space side of the chamber 108) is viewed from the axial direction of the chamber 108. Further, it is formed in a predetermined area F (hatched area) set for the surface 116c. Here, the conventional negative ion source device has the surface 116c of the plasma electrode 116 and the inner peripheral surface of the main body 108a as a portion to which the promoting substance is attached in the negative ion generation region E2. Further, the entire surface 116c of the plasma electrode 116 is formed as a flat surface, and the inner peripheral surface of the main body 108a is smooth at least in the negative ion generation region E2 (no grooves or steps are formed). It was formed as a rough surface. The area of the portion where the accelerating substance is attached in the negative ion generation region E2 of such a conventional negative ion source device is defined as “attachment area SP1”. On the other hand, in the negative ion source device 100 according to the present embodiment, since the promoting substance adhesion area increasing portion 117 is formed, the adhesion area SP2 of the portion where the promotion substance is adhered in the negative ion generation region E2 is greater than the adhesion area SP1. Also grows.

  In the example shown in FIG. 3A, the region F where the promoting substance adhesion area increasing portion 117 is formed is set in a circular shape at a part of the central position of the plasma electrode 116. The diameter D of the region F is set based on the size of the chamber 108, the gas pressure, and the like. For example, the size of the region F may be set based on the mean free path of negative ions. The mean free path is the distance that the generated negative ions can fly through the chamber 108. For example, negative ions generated at a position that is too far from the extraction hole 116a, that is, a position that is further away from the mean free path, are not extracted from the extraction hole 116a. Therefore, the region F where the promoting substance adhesion area increasing portion 117 is formed may be set within a range within the mean free path from the extraction hole 116a. The shape of the region F is not particularly limited, and may be other shapes such as a rectangular shape. When the radius of the chamber 108 is smaller than the mean free path, it may be formed on the inner peripheral surface of the main body 108a of the chamber 108.

  In the present embodiment, as shown in FIG. 3B, the promoting substance adhesion area increasing portion 117 is constituted by a plurality of uneven portions 120 formed on the surface 116 c of the plasma electrode 116. The concavo-convex portion 120 is formed by arranging a plurality of grooves concentrically around the extraction hole 116a. The surface area of the surface 116c in the region F where the uneven portion 120 is formed is larger than the surface area when the surface 116c in the region F is a flat surface. Therefore, in the negative ion source device 100 according to the present embodiment, the uneven portion 120 having a larger surface area than the plane is formed in the region F, so that the promoting substance in the negative ion generation region E2 is attached. Is larger than the adhesion area SP1 of the conventional negative ion source device. In addition, the uneven | corrugated | grooved part 120 does not need to be formed by the concentric groove | channel, and may be formed by arranging a plurality of linear grooves. Or the uneven | corrugated | grooved part 120 may be formed by arranging a some groove | channel in mesh shape. Alternatively, the uneven portion 120 may be formed by arranging a plurality of protrusions.

  As shown in FIGS. 4A to 4C, the cross-sectional shape of the uneven portion 120 is not particularly limited. For example, as shown in FIG. 4A, the uneven portion 120 may be rectangular. Moreover, as shown in FIG.4 (b), the uneven | corrugated | grooved part 120 may be wavy. Moreover, as shown in FIG.4 (c), the uneven | corrugated | grooved part 120 may be triangular shape. The concavo-convex portion 120 is configured by performing groove processing such as cutting or laser processing on the planar surface 116 c of the plasma electrode 116. Instead, a plurality of protrusions may protrude from the planar surface 116 c of the plasma electrode 116, and a space between the protrusions may be formed as the uneven portion 120.

  In the negative ion source device 100 described above, when generating negative ions, the chamber 108 and the vacuum box 104 are first evacuated by a vacuum pump. Next, a source gas (hydrogen gas) is supplied into the chamber 108 from the gas supply source 122, and a promoting substance is supplied into the chamber 108 from the promoting substance supply source 118. The supply amount of the promotion substance by the promotion substance supply source 118 may be adjusted according to the beam amount of the negative ion beam to be extracted. Since the work function is reduced on the surface of the substance to which the promoting substance is attached, the promoting substance has a function of promoting the generation of negative ions. FIG. 2 shows a deposition layer C of the promoting substance attached to the inner wall surface of the chamber 108 and the surface 116 c of the plasma electrode 116.

  Next, a current is passed through the plasma generation unit 112, and a voltage is applied between the plasma generation unit 112 and the chamber 108. When a voltage is applied between the filament 112b heated by the current flow and the chamber 108, thermoelectrons are emitted from the filament 112b to the chamber 108, and arc discharge occurs. The thermoelectrons collide with the hydrogen gas filled in the chamber 108 and eject electrons to make the hydrogen gas into plasma.

  Among electrons existing in the plasma, hot electrons and cold electrons are discriminated by the magnet 110. That is, the high-temperature electrons are confined in the plasma generation region E1 by the plasma confinement unit 110A, and are blocked by the magnetic field of the filter magnetic field generation unit 110B and are blocked from moving to the negative ion generation region E2. On the other hand, the low-temperature electrons move to the negative ion generation region E2. Negative ions are generated by the reaction of low-temperature electrons or electrons on the surface 116c of the plasma electrode 116 with hydrogen molecules, hydrogen atoms, or hydrogen ions in the plasma. The negative ions generated in this way are extracted out of the chamber 108 through the extraction hole 116 a of the plasma electrode 116 and introduced into the cyclotron 2 through the vacuum box 104.

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

  The negative ion source device 100 according to the present embodiment is provided in a filter magnetic field generation unit 110B that generates a magnetic field that blocks electrons having a predetermined energy or higher, and a magnetic field region (negative ion generation region E2) in which a magnetic field is generated. And an accelerating substance attachment area increasing portion 117 for increasing the area of the portion to which the accelerating substance is attached. In the magnetic field region by the filter magnetic field generation unit 110B, intrusion of electrons having a predetermined energy or higher is blocked, so that negative ions are generated in the magnetic field region without being destroyed by high energy electrons. In the surface of the portion where the promoting substance adheres in the magnetic field region, the work function is lowered by the promoting substance, so that the surface of negative ions is generated. Therefore, by providing the promoting substance adhesion area increasing portion 117 in the magnetic field region, the area of the portion where the surface generation of negative ions is performed increases. As a result, the amount of negative ions generated can be increased.

  In the negative ion source device 100 according to the present embodiment, the promoting substance adhesion area increasing portion 117 is configured by the uneven portion 120 formed on the surface 116 c of the plasma electrode 116. Thereby, the area which concerns on the surface production | generation of a negative ion can be increased, without using another member.

[Second Embodiment]
With reference to FIG.5 and FIG.6, the negative ion source apparatus 200 which concerns on 2nd Embodiment is demonstrated. In the negative ion source device 200 according to the second embodiment, the configuration of the promoting substance adhesion area increasing unit 217 is different from the configuration of the promoting substance adhesion area increasing unit 117 of the negative ion source device 100 according to the first embodiment.

  As shown in FIGS. 5 and 6, the accelerating substance adhesion area increasing portion 217 is configured by an accelerating substance adhesion area increasing member 218 provided apart from the surface 116 c of the plasma electrode 116. The promoting substance adhesion area increasing member 218 is disposed in a space within the negative ion generation region E2. The promoting substance adhesion area increasing member 218 is disposed at a position separated from the surface 116c so as to cover the surface 116c in the region F (see FIG. 3A). In addition, although the separation distance between the accelerating substance adhesion area increasing member 218 and the surface 116c is not particularly limited, it is preferably disposed at a position where the distance from the extraction hole 116a is smaller than the mean free path.

  The promoting substance adhesion area increasing member 218 is supported by the support member 219. The support member 219 is made of an insulating material. Therefore, the accelerating substance adhesion area increasing member 218 can apply a voltage independently of the plasma electrode 116 and the chamber 108 so that the plasma sheath can be adjusted. The structure of the support member 219 is not particularly limited, and may be a plurality of leg members as shown in FIG. 6A, or a cylindrical member as shown in FIG. The support member 219 may be connected to the plasma electrode 116, but may be connected to the chamber 108.

  As shown in FIG. 6, the accelerating substance adhesion area increasing member 218 has a through-hole 220 having a size capable of passing at least electrons. Specifically, the accelerating substance adhesion area increasing member 218 is constituted by a mesh-like metal member. The size of each through-hole 220 is not particularly limited as long as it is set to a size through which electrons can pass. Further, the ratio of the through-hole 220 to the area of the entire promoting substance adhesion area increasing member 218 may be in a range that does not prevent the electrons and negative ions from moving to the surface 116c and the extraction hole 116a side. The accelerating substance adhesion area increasing member 218 may be configured by stretching a plurality of metal wires, or may be configured by forming a plurality of through holes 220 in a metal plate.

  As described above, in the negative ion source device 200 according to the present embodiment, the promoting substance adhesion area increasing portion 217 is configured by the promoting substance adhesion area increasing member 218 provided apart from the surface 116 c of the plasma electrode 116. Yes. Accordingly, even if the plasma electrode 116 is not processed or the like, the area related to the surface generation of negative ions can be easily increased by providing the promoting substance adhesion area increasing member 218 which is a separate member.

  In the negative ion source device 200 according to the present embodiment, the promoting substance adhesion area increasing member 218 has a through hole 220. Accordingly, atoms, molecules, and electrons for generating negative ions can move to the plasma electrode 116 side through the through hole 220 of the promoting substance adhesion area increasing member 218.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to above-described embodiment. For example, the ion source device employs both the uneven portion 120 formed on the plasma electrode 116 and the promoting substance adhesion area increasing member 218 spaced from the surface 116c of the plasma electrode 116 as the promoting substance adhesion area increasing part. It's okay.

  For example, the plasma generation unit 112 may be an internal antenna type instead of the filament 112b. In this case, plasma is generated in the chamber 108 by applying a high frequency to the antenna.

  The pipe 116b connected to the gas supply source 122 is not located on the other end side of the chamber 108, but may be provided at another location. For example, the pipe 116b may be provided on the other end side of the chamber 108, or may be provided between one end and the other end of the chamber 108.

  Further, the overall configuration of the negative ion source device is not limited to that shown in FIGS. 2 and 5, and the one shown in FIG. 7 may be adopted. The negative ion source device 300 shown in FIG. 7 differs from the negative ion source device 100 of FIG. 1 in, for example, the shape of the filament 312 and the plasma electrode 316 arranged in the chamber 308, the arrangement of the filter magnetic field generation unit 310B, and the like. Yes. In the negative ion source device 300, a negative ion generation region E2 is formed in the vicinity of the plasma electrode 316, and a promoting substance adhesion area increasing portion 317 is formed in the region. The negative ion source device 400 shown in FIG. 8 differs from the negative ion source device 100 of FIG. 1 in the configuration of the plasma generation unit 412, the shape of the chamber 408, the shape of the plasma electrode 416, and the like. In the negative ion source device 400, a negative ion generation region E2 is formed in the vicinity of the plasma electrode 416, and a promoting substance adhesion area increasing portion 417 is formed in the region.

DESCRIPTION OF SYMBOLS 1 ... Neutron capture therapy apparatus, 100, 200, 300, 400 ... Negative ion source apparatus, 108, 308, 408 ... Chamber, 110B, 310B ... Filter magnetic field production | generation part, 112 ... Plasma production part, 115 ... Promoter supply part, 116, 316, 416 ... plasma electrode, 116a ... extraction hole, 116c ... surface, 117, 217, 317, 417 ... accelerating substance adhesion area increasing part, 120 ... irregularity part, 218 ... accelerating substance adhesion area increasing member (member).

Claims (3)

A chamber for generating negative ions therein;
A source gas supply unit for supplying source gas into the chamber;
A plasma generation unit that generates plasma using the source gas supplied by the source gas supply unit;
A plasma electrode provided on one end side of the chamber and having an extraction hole for extracting the generated negative ions;
An accelerating substance supply unit for supplying an accelerating substance that promotes the generation of the negative ions into the chamber;
A filter magnetic field generation unit that is provided on the one end side of the chamber and generates a magnetic field that blocks electrons of a predetermined energy or higher;
A promoting substance attachment area increasing portion that is provided in a magnetic field region where the magnetic field is generated and increases the area of the part to which the promoting substance is attached as compared to a plane ;
The magnetic field generated in the filter magnetic field generation unit blocks the electrons having a predetermined energy or higher from the plasma generation unit side from entering the magnetic field,
The promoting substance adhesion area increasing part is a negative ion source device configured by an uneven part formed on the surface of the plasma electrode . 2. The negative ion source device according to claim 1, wherein the promoting substance adhesion area increasing portion is configured by a member provided apart from a surface of the plasma electrode. The negative ion source device according to claim 2 , wherein the member has a through hole.

Images