JP4828895B2 - Voltage application method for X-ray tube apparatus and X-ray tube apparatus - Google Patents

Description

  The present invention relates to a voltage application method for an X-ray tube apparatus and an X-ray tube apparatus in which X-rays are emitted from an anode by the incidence of electrons from the cathode to the anode.

  Conventionally, in operation, the X-ray tube apparatus is accelerated by the high voltage applied between the cathode assembly and the anode target, and the thermal electrons emitted from the cathode assembly are collided with the focal plane of the anode target. X-rays are generated from this focal plane. At this time, the thermoelectrons that have collided with the anode target are converted into heat and X-rays when the anode target collides, but in reality they are not all converted into heat or X-rays, and the electrons are repeatedly scattered. The direction and intensity of recoil electrons due to this scattering vary depending on the applied voltage and the electric field near the focal point, but about 40% or more of the incident electrons recoil in all directions. The recoil electrons are various such as those returning to a part other than the focal plane of the anode target and those entering the vacuum envelope. The out-of-focus X-rays generated by the recoil electrons are It becomes a noise component for X-rays generated from the focal plane. The heat generated by the recoil electrons is also a factor that raises the temperature of the anode target and the like.

  In view of this, an X-ray tube apparatus using a rotating anode X-ray tube having a structure that captures these recoil electrons without returning them to the anode target as much as possible has been proposed. In this X-ray tube apparatus using a rotating anode X-ray tube, a recoil electron capture structure as a recoil electron trap that captures recoil electrons recoiled by the anode target between the cathode assembly and the anode target. Is provided. The recoil electron capturing structure is formed in a cylindrical shape so as to surround the trajectory of electrons emitted from the cathode assembly. Furthermore, the heat generated by the recoil electrons in the recoil electron capturing structure is enormous, and a liquid path for passing a cooling medium is provided for cooling the heat generation, and the liquid path for the cooling medium is provided outside the vacuum envelope. There is known a configuration that is extended to a heat exchanger and connected to a heat exchanger (for example, see Patent Document 1).

  The voltage application method when this recoil electron capture structure is used is a grounded anode type in which the recoil electron capture structure has the same potential as the anode target, or the recoil electron capture structure has a cathode potential and an anode potential. A neutral point grounding type is used as an intermediate potential, and a fixedly set voltage is applied to each of these anode grounding type and neutral point grounding type.

For example, when a voltage of 120 kV is applied between the anode and the cathode, the anode target including the recoil electron capturing structure is 0 V of the ground potential and the cathode assembly is −120 kV in the grounded anode type. In addition, in the neutral point grounding, the vacuum envelope including the recoil electron capturing structure is 0 V of the ground potential, the anode target is +60 kV, the cathode assembly is −60 kV, and the ground potential is always the anode voltage. It is applied so as to be a neutral point with respect to the cathode tube voltage.
JP 2002-352756 A (page 3-5, FIG. 1)

  As described above, in the X-ray tube apparatus using the recoil electron capture structure, a fixed voltage is applied to each of the anode grounded type and the neutral point grounded type.

  The grounded anode type has the advantage that a large amount of recoil electrons are captured and a large amount of input can be input to the anode target. On the other hand, most of the recoil electrons are in the recoil electron capture structure and the surrounding vacuum enclosure. Since it enters the chamber, the amount of heat generated by the recoil electron capture structure and the like becomes enormous, and there is a problem that a high cooling capacity is required. In particular, in an X-ray tube apparatus using a rotating anode X-ray tube, even if it has a high cooling capacity, the recoil electron capture structure fixed to a large rotating anode target has an input limit. In many cases, the limit of heat input to the recoil electron capture structure determines the input specifications of the X-ray tube apparatus. That is, the input limit is reached without fully using the performance of the large capacity anode target. In the case of the grounded anode type, the electrons collide with the anode target through the area surrounded by the recoil electron capturing structure, so that the electrons are anti-converged, making it difficult to form a small focal point, and the resolution is lowered. There are also problems.

  In addition, in the case of the neutral grounding type, the amount of recoil electrons that enter the recoil electron capturing structure and the nearby vacuum envelope is smaller than that of the grounded anode type. While the amount of heat generation is reduced and the cooling capacity of the recoil electron capture structure can be reduced, there is a problem that the amount of heat generated at the anode target and out-of-focus X-rays increase.

  As described above, the X-ray tube apparatus using the recoil electron capture structure has advantages and problems in both the anode grounded type and the neutral point grounded type. It was difficult to respond appropriately.

  The present invention has been made in view of such points, and an object thereof is to provide an X-ray tube apparatus voltage application method and an X-ray tube apparatus capable of arbitrarily variably setting the recoil electron capture amount, the focal size, and the like. To do.

The present invention captures a cathode that emits electrons, an anode that emits X-rays upon incidence of electrons emitted from the cathode opposite to the cathode, and recoil electrons that are emitted from the cathode and bounced off at the anode. A voltage application method for an X-ray tube apparatus comprising a recoil electron capture structure, wherein the potential difference between the cathode and the recoil electron capture structure is between the anode and the recoil electron capture structure. And the cooling capacity for cooling the recoil electron trapping structure is varied according to the variable potential difference ratio .

Further, the X-ray tube device of the present invention includes a cathode that emits electrons, an anode that emits X-rays by incidence of electrons emitted from the cathode so as to face the cathode, and an anode that emits electrons from the cathode and The ratio of the recoil electron capture structure that captures the recoiled electrons bounced back and the potential difference between the cathode and the recoil electron capture structure and the potential difference between the anode and the recoil electron capture structure is variable. And a cooling means for cooling the recoil electron capturing structure and for changing the cooling capacity in accordance with the potential difference variable by the power supply control device .

  Then, when a voltage is applied by the power supply control device, electrons emitted from the cathode enter the anode, and X-rays are emitted from the anode. Some of the electrons incident on the anode recoil, and the recoil electrons are captured by the recoil electron capturing structure. The ratio between the potential difference between the cathode and the recoil electron capture structure and the potential difference between the anode and the recoil electron capture structure is varied by the power supply control device in accordance with the exposure conditions. For example, when the amount of recoil electron capture is increased, the potential difference between the cathode and the recoil electron capture structure is varied to be larger than the potential difference between the anode and the recoil electron capture structure, When the electron focal size is reduced, the potential difference between the cathode and the recoil electron capture structure is varied so as to be smaller than the potential difference between the anode and the recoil electron capture structure.

  According to the present invention, since the ratio between the potential difference between the cathode and the recoil electron capture structure and the potential difference between the anode and the recoil electron capture structure can be varied, the recoil can be adjusted according to the exposure conditions. The amount of electron capture and focus size can be variably set.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes an X-ray tube device using a rotating anode X-ray tube. The X-ray tube device 1 includes a housing 2 as a spherical tube that is hollow inside and filled with insulating oil or the like. The housing 2 is provided for X-ray shielding. In the housing 2, a vacuum envelope 3 as a container for holding the inside in a vacuum is accommodated and installed. The vacuum envelope 3 is a tube made of an insulator or an insulator containing a part of metal. On the one end side in the axial direction of the vacuum envelope 3, a cylindrical enlarged diameter portion 4 having an enlarged diameter is provided. An X-ray output window 5 for emitting X-rays L generated in the vacuum envelope 3 to the outside is provided on the outer peripheral portion of the enlarged diameter portion 4.

  On the other end side of the vacuum envelope 3 in the axial direction, an elongated cylindrical reduced diameter portion 6 as an insulator is provided concentrically and integrally. One end side of the reduced diameter portion 6 is concentrically penetrated and continuous with the other end side of the enlarged diameter portion 4, and the other end surface of the reduced diameter portion 6 is closed.

  On one end side of the enlarged diameter portion 4 of the vacuum envelope 3, a cylindrical cathode accommodating portion 7 that penetrates and opens into the enlarged diameter portion 4 is provided. The cathode accommodating portion 7 is provided at the peripheral edge of the enlarged diameter portion 4 and penetrates toward the one end side of the housing 2. In the cathode accommodating portion 7, a cathode 12, which is a cathode assembly body as an electron gun provided with an emitter source 11 that emits thermoelectrons e as electrons, is concentrically attached via an insulator 13. The insulator 13 is made of alumina ceramic, for example, and is a cathode support that supports the cathode 12 with respect to the vacuum envelope 3 and electrically insulates the cathode 12.

  Further, in the enlarged diameter portion 4 of the vacuum envelope 3, a rotary trapezoidal anode target 14 which is a rotary anode structure as an anode is rotatably arranged. The anode target 14 is electrically insulated from the cathode 12 via the insulator 13 in a state of being opposed to the cathode 12 and is rotatably installed in the circumferential direction of the vacuum envelope 3. . On the outer peripheral edge on one end side that is the side facing the cathode 12 of the anode target 14, an inclined surface portion 15 that is inclined in a tapered shape on the other end side in the outer diameter direction of the anode target 14 is formed. The inclined surface portion 15 is provided with a focal plane 16 that emits X-rays when irradiated with thermionic electrons e.

  The focal plane 16 is a raceway formed in a disc shape along the circumferential direction of the anode target 14. Specifically, the focal plane 16 is such that X-rays L generated by bremsstrahlung due to the impact of thermoelectrons e emitted from the cathode 12 are emitted from the X-ray output window 5 of the enlarged diameter portion 4 of the vacuum envelope 3. It is configured to be released to the outside. The cathode 12 and the anode target 14 are applied with a high voltage between the cathode 12 and the anode target 14 to accelerate the thermoelectrons e emitted from the cathode 12 and to focus the rotating anode target 14. X-rays L are generated by impacting thermoelectrons e on the surface 16.

  The anode target 14 is coaxially fixed and supported on one end side in the axial direction of the rotating member 22 as an elongated cylindrical rotating body by a fixing nut 21. The rotating member 22 has an opening 23 that opens toward the other end. A spiral groove (not shown) is formed on the inner peripheral surface of the opening 23 to form a radial bearing surface. The rotating member 22 has the other end of the rotating member 22 disposed in the reduced diameter portion 6 of the vacuum envelope 3.

  Further, one end side of the elongated columnar fixed shaft 24 in the axial direction is inserted into the opening 23 of the rotating member 22 to be rotatable. The fixed shaft 24 includes an elongated cylindrical bearing portion 25, and the bearing portion 25 is rotatably inserted into the opening 23 of the rotating member 22. The rotating member 22 can rotate in the circumferential direction. To support. On the outer peripheral surface of the bearing portion 25, a radial bearing surface for forming a plain bearing is formed between the inner peripheral surface in the opening 23 of the rotating member 22. On the other end side of the bearing portion 25, a fixed portion 26 having an outer diameter smaller than the outer diameter of the bearing 25 is provided concentrically. The fixing portion 26 protrudes outward from one end surface of the reduced diameter portion 6 of the vacuum envelope 3 and is fixed to the vacuum envelope 3.

  The fixed shaft 24 and the rotation member 22 constitute a rotation mechanism 27. The rotating mechanism 27 is a sliding bearing structure using liquid metal lubrication that enables the anode target 14 to rotate via the rotating member 22. An active liquid metal 28 as a metal lubricant is interposed between the radial bearing surface of the opening 23 of the rotating member 22 of the rotating mechanism 27 and the radial bearing surface of the bearing portion 25 of the fixed shaft 24.

  A cylindrical stator 29 which is an induction electromagnetic coil as a driving means is installed outside the reduced diameter portion 6 of the vacuum envelope 3. The stator 29 is accommodated in the housing 2.

  In addition, a mortar serving as a trap portion projecting inward along the circumferential direction of the cathode housing portion 7 is formed on the inner edge of the opening on the one end side which is the diameter expansion portion 4 side of the cathode housing portion 7 of the vacuum envelope 3. A cylindrical recoil electron capturing structure 31 is provided. The recoil electron capturing structure 31 captures recoil electrons emitted from the cathode 12 and bounced off by the anode target 14. The thermoelectrons e generated and emitted from the cathode 12 are focused on the anode target 14. It is arranged so as to surround the electron trajectory when moving to the surface 16.

  On one side surface of the recoil electron capturing structure 31 facing the cathode 12, there is a tapered inclined surface 32 inclined toward the other end side of the cathode accommodating portion 7 toward the central axis direction of the cathode accommodating portion 7. Is provided. Further, on the other side surface of the recoil electron capturing structure 31 facing the anode target 14 side, there is a flat surface 33 that is flush with the inner surface on the other end side of the enlarged diameter portion 4 of the vacuum envelope 3. Is formed. The recoil electron capturing structure 31 captures recoil electrons on each of the inclined surface 32 and the flat surface 33.

  Inside the recoil electron capturing structure 31, a liquid path 34 penetrating in the circumferential direction of the recoil electron capturing structure 31 is formed. The liquid passage 34 is connected to a cooler device 35 as a cooling means installed outside the housing 2 via a cooling pipe 36. The cooler device 35 circulates the cooling medium C as a refrigerant cooled by the cooler device 35 through the cooling pipe 36 to the liquid path 34 of the recoil electron capture structure 31 to thereby capture the recoil electron capture. Each of the structure 31 and the portion of the vacuum envelope 3 that faces the center of rotation of the anode target 14 is cooled.

  The recoil electron capturing structure 31 has the same potential as the vacuum envelope 3 and is electrically insulated from the anode target 14 via the reduced diameter portion 6 which is an insulator, Are electrically insulated via an insulator 13. Positive and negative voltages are applied to the cathode 12 and the anode target 14 from the power supply control device 41, and the values of these voltages are controlled by the power supply control device 41. In the structure shown in FIG. 1, the vacuum envelope 3 including the recoil electron capturing structure 31 is always fixed to the ground potential (0 V), and only the applied voltage of the cathode 12 and the anode target 14 is variable.

  By the way, since proper X-ray quality is required for normal imaging by the X-ray imaging apparatus using the X-ray tube apparatus 1 depending on the imaging region and method, the anode-cathode voltage is inevitably determined to some extent. End up. Therefore, the power supply control device 41 does not change the voltage between the anode and the cathode, but changes the potential difference with the vacuum envelope 3 including the recoil electron capture structure 31 according to the exposure conditions. Variable by 14 each. That is, the power supply control device 41 keeps the potential difference between the cathode 12 and the anode target 14 constant (does not change), and changes between the cathode 12 and the recoil electron capturing structure 31 according to the exposure conditions. And the potential difference between the anode target 14 and the recoil electron capturing structure 31 are varied. The exposure conditions include various conditions such as limitation of the amount of heat generated by the anode target 14 and the recoil electron capturing structure 31, the use conditions of the X-ray tube apparatus 1, and the imaging region of the subject. .

  For example, when the anode-cathode voltage required for imaging is 120 kV, the anode target 14 is 0 kV, the recoil electron capturing structure 31 is 0 kV, and the cathode 12 is -120 kV, as in the grounded anode type shown in FIG. Or the anode target 14 is set to +60 kV, the recoil electron capture structure 31 is set to 0 kV, and the cathode 12 is set to −60 kV, or the cathode-grounded type shown in FIG. Thus, the anode target 14 is set to +120 kV, the recoil electron capturing structure 31 is set to 0 kV, and the cathode 12 is set to 0 kV. Such a change in the ratio of the potential difference may be continuously changed or may be changed stepwise by a preset voltage width. Specifically, for example, in the case of an exposure condition that increases the amount of recoil electrons captured, the potential difference between the cathode 12 and the recoil electron capture structure 31 is different from that of the anode target 14 and the recoil electron capture structure. When the exposure condition is such that the potential difference between the cathode 31 and the body 31 is larger and the focal point is reduced, the potential difference between the cathode 12 and the recoil electron capture structure 31 is opposite to that of the anode target 14. It is variable so as to be smaller than the potential difference with the positron capture structure 31.

  The power supply control device 41 includes a storage unit and a control unit (not shown), stores a ratio of a potential difference according to a preset exposure condition in the storage unit, and a ratio of a potential difference according to the exposure condition by the control unit Is selected from the stored contents of the storage unit and set. The combination of the exposure condition and the potential difference ratio can be selected by creating a database in advance through experiments or the like.

  In addition, the cooler device 35 includes a cooling control unit (not shown), and has a function of varying the cooling capacity according to the ratio of the potential difference varied by the power supply control device 41 by the cooling control unit. For example, when the amount of recoil electrons captured by the recoil electron capture structure 31 is large depending on the ratio of the potential difference, and when the amount of heat generated by the recoil electron capture structure 31 increases, the cooling capacity is increased. When the amount of recoil electrons captured by the electron capture structure 31 is small and the amount of heat generated by the recoil electron capture structure 31 is small, the cooling capacity is lowered.

  Next, the operation of the X-ray tube apparatus 1 of the present embodiment will be described.

  First, during operation of the X-ray tube apparatus 1, the thermoelectrons e emitted from the cathode 12 are accelerated by a high voltage applied between the cathode 12 and the anode target 14, and then the focus of the anode target 14 is increased. The X-ray L is generated from the focal plane 16 by colliding with the plane 16.

  At this time, in order to relieve local heat generation at the focal plane 16 due to the collision energy at the time of collision of the thermoelectrons e with the focal plane 16, a rotating magnetic field is applied to the rotating member 22 from the stator 29, The anode target 14 is rotated by rotating the rotating member 22.

  The X-ray L emitted from the focal plane 16 of the anode target 14 is irradiated from the X-ray output window 5 of the enlarged diameter portion 4 of the vacuum envelope 3 to the outside, and then passes through a non-irradiated object such as a human body. The film is taken out by a film or a detector (not shown).

  Further, the thermoelectrons e colliding with the focal plane 16 of the anode target 14 are converted into heat and X-rays L at the focal plane 16, but in reality, all conversion does not occur at the focal plane 16, The thermoelectrons e are bounced back and scattered as recoil electrons r (see FIG. 3 and the like). Recoil electrons r bounced off at the focal plane 16 of the anode target 14 are captured by the recoil electron capture structure 31.

  During operation of the X-ray tube apparatus 1, the cooling medium C cooled by the cooler apparatus 35 is circulated through the liquid path 34 of the recoil electron capturing structure 31 by the cooler apparatus 35. Each of 31 and the portion of the vacuum envelope 3 facing the center of rotation of the anode target 14 is cooled.

  Next, with the power supply control device 41, the potential difference between the cathode 12 and the anode target 14 is constant, the potential difference between the cathode 12 and the recoil electron capture structure 31, and the anode target 14 and recoil electron capture structure Changes in the amount of recoil electrons r and the focus size when the ratio of the potential difference with the body 31 is varied will be described with reference to FIGS.

  FIG. 2 shows an example of voltage distribution at the anode target 14, recoil electron capture structure 31, and cathode 12 when the anode-cathode voltage is 120 kV. Three patterns are shown. 3, 4, and 5 are schematic diagrams corresponding to three patterns of an anode grounding type, a neutral point grounding type, and a cathode grounding type, respectively.

  FIG. 3 shows an anode ground type case in which the anode target 14 is 0 kV, the recoil electron capturing structure 31 is 0 kV, and the cathode 12 is −120 kV.

  In the case of this grounded anode type, the anode target 14 and the recoil electron capturing structure 31 are at the same potential, so that the recoil electrons r having a relatively low energy after recoiling at the anode target 14 can be easily reflected. Since it can be captured by the capture structure 31, the amount of recoil electrons r that can be captured by the recoil electron capture structure 31 is maximized. Therefore, recoil electrons r returning to a portion other than the focal plane of the anode target 14 and recoil electrons r entering the vacuum envelope 3 are reduced, and out-of-focus X-rays generated by the recoil electrons r are reduced. To do. Therefore, a noise component with respect to the X-ray L generated from the focal plane 16 of the anode target 14 can be reduced.

  At the same time, the amount of heat generated by the recoil electron capturing structure 31 is also maximized. The amount of heat generated by the recoil electron capturing structure 31 is about 30 to 40% of the total energy input from the cathode 12 to the anode target 14 depending on the structure and applied voltage. That is, the amount of heat generated at the anode target 14 is about 60 to 70% of the total energy input from the cathode 12 to the anode target 14.

  Corresponding to the enormous amount of heat generated in the recoil electron capture structure 31, the cooling capacity of the cooler device 35 is increased, and the inside of the recoil electron capture structure 31 is cooled by a cooling refrigerant such as boiling heat transfer cooling. To cool.

  A beam of thermoelectrons e traveling from the cathode 12 to the anode target 14 is spread by the recoil electron capturing structure 31 having the same potential as the anode target 14 and the focus is widened. The spread of the thermoelectron e beam becomes more pronounced as the opening of the recoil electron capturing structure 31 is narrower.

  FIG. 4 shows a neutral point grounding type in which the anode target 14 is +60 kV, the recoil electron capture structure 31 is 0 kV, and the cathode 12 is −60 kV.

  In this neutral point grounding type, since there is a potential difference between the anode target 14 and the recoil electron capture structure 31, the recoil electrons r recoiled at the anode target 14 go back to the potential difference and recoil electrons. Since the trapping structure 31 must be rushed, the recoil electrons r having energy that can be reached are limited. Therefore, compared with the case of the grounded anode type shown in FIG. 3, the amount of recoil electrons r captured by the recoil electron capture structure 31 is reduced, and the out-of-focus X-rays generated by the recoil electrons r are increased. The amount of heat generated in the recoil electron capturing structure 31 is reduced.

  The amount of heat generated by the recoil electron capturing structure 31 is about 8 to 16% of the total energy input from the cathode 12 to the anode target 14 depending on the structure and applied voltage. That is, the amount of heat generated at the anode target 14 is about 84 to 92% of the total energy input from the cathode 12 to the anode target 14.

  In this case as well, the recoil electron capturing structure 31 needs to be cooled, but the cooling capacity of the cooler device 35 may be lower than that of the grounded anode type shown in FIG.

  The beam of thermoelectrons e traveling from the cathode 12 to the anode target 14 is relatively less susceptible to the recoil electron capture structure 31, and therefore the focal spread is also reduced.

  FIG. 5 shows a case of a grounded cathode type in which the anode target 14 is +120 kV, the recoil electron capturing structure 31 is 0 kV, and the cathode 12 is 0 kV.

  In the case of the grounded cathode type, recoil electrons r recoiled at the anode target 14 cannot enter the recoil electron capture structure 31 in terms of potential. Therefore, the heat generated in the recoil electron capturing structure 31 is only radiant heat from the anode target 14 or radiant heat from the cathode filament 11, and is slight, and there is no need for cooling by the cooler device 35. Cooling capacity is low. However, since all recoil electrons r return to the anode target 14, the heat generation at the anode target 14 is maximized.

  The thermoelectron e beam traveling from the cathode 12 to the anode target 14 is in a converging direction because the recoil electron capture structure 31 becomes a part of the focusing electrode, so that a small focal point is easily formed, and the resolution of the captured image is reduced. Can be increased.

  The applied voltages shown in FIG. 3, FIG. 4, and FIG. 5 are representative examples, and an arbitrary applied voltage can actually be selected.

  Next, the criteria for selecting the applied voltage will be described with reference to FIG.

  In FIG. 6, the horizontal axis shows the voltage between the anode and recoil electron capture structure, that is, the voltage applied to the anode target 14, and the cathode-recoil electron capture structure voltage, ie, the voltage applied to the cathode 12. On the axis, the ratio of the amount of heat generated in the anode target 14 and the recoil electron capture structure 31 (including the nearby vacuum envelope 3) with respect to the total energy input from the cathode 12 to the anode target 14, and the beam of thermionic e The relative value of the focal dimension is shown as 1 for the neutral point grounding type.

  Assume that the anode target 14 can continuously use a calorific value of 48 kW for 30 seconds, and the recoil electron capture structure 31 has a structure that can be used up to a calorific value of 16 kW. In this case, since the recoil electron capture structure 31 is forcibly cooled inside, the saturation temperature is reached in 5 to 7 seconds, and it is assumed that continuous use of 16 kW is possible.

  In this case, since the total input = the amount of heat generated by the anode target 14 at the applied voltage A point, the maximum allowable amount of heat generated by the anode target 14 exceeds 48 kW-30 seconds. Therefore, the maximum input specification is 48 kW-30 seconds. This is the input limit limitation of the anode target 14.

Conversely, at the applied voltage point B, the amount of heat generated by the anode target 14 is 70%, so 48 / 0.7 = 68.57, and it is possible to input apparently up to about 68.6 kW-30 seconds. At this time, since the recoil electron capturing structure 31 has a heat value of 30%, the heat value is about 20.6 kW. In this case, the maximum allowable heat generation amount 16 kW of the recoil electron capturing structure 31 is exceeded, so that it cannot be used. Therefore, the total input 16 / 0.3 = 53.3 is 16 kW = 30%, and about 53 kW is the maximum. At the applied voltage B point, 53 kW-30 seconds is the maximum input specification value. . This is the input limit limitation of the recoil electron capturing structure 31.

  Furthermore, at the applied voltage C point, the anode target 14 generates 75% of heat and the recoil electron capture structure 31 generates 25%. In this case, 48 / 0.75 = 64 on the anode target 14 side, and it is possible to input up to 64 kW, and 16 / 0.25 = 64 on the recoil electron capture structure 31 side, which is also up to 64 kW. It will be able to withstand total tube input. In this case, since both limit values match, this 64 kW is the maximum input specification. That is, the input specification is maximized in the distribution of the applied voltage at the applied voltage C point.

  However, when the same focal point is used, the focal point increases in the order of applied voltage A point → C point → B point. Therefore, under the condition that the maximum input is not used, the voltage with which the focal point with high resolution is rather small is used. Since a combination of applications may be selected, it is desirable that an appropriate applied voltage distribution, that is, a potential difference ratio is selected in accordance with the exposure conditions. The combination can be automatically selected by the power supply control device 41 by creating a database in advance through experiments or the like.

  Thus, the power supply control device 41 makes the potential difference between the cathode 12 and the anode target 14 constant, and the potential difference between the cathode 12 and the recoil electron capture structure 31 and the anode target 14 and recoil electron capture structure. Since the ratio of the potential difference between the body 31 and the body 31 can be varied, the recoil electron capture amount, the focal size, and the like can be arbitrarily variably set.

  Further, since the power supply control device 41 stores the ratio of the potential difference according to the preset exposure condition, the ratio of the potential difference according to the exposure condition can be automatically selected from the stored contents and set appropriately. .

  Further, in the cooler device 35, the cooling capacity is varied according to the ratio of the potential difference varied by the power supply control device 41, so that the temperature management of the recoil electron capturing structure 31 can be appropriately performed.

  In the above embodiment, the case where the control of the ratio of the potential difference by the power supply control device 41 is applied to the rotary anode X-ray tube has been described. However, the X-ray tube device using a fixed anode X-ray tube in which the anode does not rotate The same applies to.

It is sectional drawing of the X-ray tube apparatus which shows one embodiment of this invention. It is a table | surface which shows the applied voltage of an anode grounding type, a neutral point grounding type, and a cathode grounding type of an X-ray tube apparatus same as the above. It is a schematic diagram which shows the recoil electron in the case of the anode grounding type of an X-ray tube apparatus same as the above. It is a schematic diagram which shows recoil electrons in the case of a neutral point grounding type X-ray tube apparatus. It is a schematic diagram which shows the recoil electron in the case of a cathode grounding type of the same X-ray tube apparatus. It is a graph which shows the relationship between the applied voltage of a X-ray tube apparatus same as the above, the emitted-heat amount, and a focal dimension.

Explanation of symbols

1 X-ray tube device
12 Cathode
14 Anode target as anode
31 Recoil electron capture structure
35 Cooler device as a cooling means
41 Power supply control device e Thermoelectron as electron L X-ray r Recoil electron

Claims (6)

A cathode that emits electrons, an anode that emits X-rays by the incidence of electrons emitted from the cathode opposite to the cathode, and a recoil electron that captures recoil electrons emitted from the cathode and bounced off by the anode A voltage application method for an X-ray tube device comprising a capture structure,
With varying the ratio of the potential difference between the potential difference between the anode between said cathode recoil electron capturing structure and the recoil electron capturing structure,
A method of applying a voltage to an X-ray tube apparatus, wherein a cooling capacity for cooling the recoil electron capturing structure is varied in accordance with a variable potential difference ratio . The potential difference between the cathode and the anode is constant, and the ratio between the potential difference between the cathode and the recoil electron capture structure and the potential difference between the anode and the recoil electron capture structure is variable. The voltage application method of the X-ray tube apparatus of Claim 1. 3. The voltage application method for an X-ray tube apparatus according to claim 1, wherein the potential difference ratio is selected from a potential difference ratio set in advance according to the exposure conditions . A cathode that emits electrons;
An anode that emits X-rays upon incidence of electrons emitted from the cathode facing the cathode;
A recoil electron capture structure that captures recoil electrons emitted from the cathode and bounced off the anode;
A power control unit for varying the ratio of the potential difference between the potential difference between the anode and the recoil electron capturing structure between the cathode and the recoil electron capturing structure,
An X-ray tube apparatus comprising: a cooling unit that cools the recoil electron capturing structure and changes a cooling capacity in accordance with a potential difference variable by the power supply control device. The potential difference between the cathode and the anode is constant, and the ratio between the potential difference between the cathode and the recoil electron capture structure and the potential difference between the anode and the recoil electron capture structure is variable. The X-ray tube apparatus according to claim 4, wherein the apparatus is an X-ray tube apparatus. Power control device stores the percentage of potential difference corresponding to a preset exposure conditions, according to claim 4 or 5, wherein selecting a percentage of the potential difference corresponding to the exposure conditions from the stored contents X-ray tube device .

Images