WO2019124309A1 - Dispositif à rayons x et procédé de commande de dispositif à rayons x - Google Patents

Dispositif à rayons x et procédé de commande de dispositif à rayons x Download PDF

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WO2019124309A1
WO2019124309A1 PCT/JP2018/046351 JP2018046351W WO2019124309A1 WO 2019124309 A1 WO2019124309 A1 WO 2019124309A1 JP 2018046351 W JP2018046351 W JP 2018046351W WO 2019124309 A1 WO2019124309 A1 WO 2019124309A1
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target
electron beam
temperature
ray apparatus
ray
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PCT/JP2018/046351
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English (en)
Japanese (ja)
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一明 鈴木
山本　昌志
中西　康介
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株式会社ニコン
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/12—Cooling non-rotary anodes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor

Definitions

  • the present invention relates to an X-ray device and a control method of the X-ray device.
  • Patent Document 1 There is known an X-ray apparatus (for example, Patent Document 1) which generates X-rays from a target by colliding electrons with a metal target.
  • Patent Document 1 X-ray apparatus
  • X-rays are frequently used for various X-ray examinations and diagnoses such as X-ray CT taking advantage of the strong ability to transmit X-rays.
  • An X-ray apparatus is based on a target that generates an X-ray upon incidence of an electron beam, an electron beam source that emits an electron beam toward the target, and information on the state of the electron beam.
  • a control unit configured to control the electron beam source based on the state of the target estimated by the estimation unit.
  • a control method of an X-ray apparatus comprises: estimating a state of a target irradiated with an electron beam; and controlling an electron beam source emitting the electron beam based on the estimated state of the target Controlling parameters; and emitting X-rays from the target by emitting the electron beam from the electron beam source and irradiating the target.
  • a control method of an X-ray apparatus comprising: controlling a control parameter of an electron beam source for emitting the electron beam based on a state of a target estimated from the state of the electron beam; Emitting X-rays from the target by emitting the electron beam from a beam source and irradiating the target.
  • FIG. 2 is a plan sectional view of an electron gun, an acceleration tube, and a target used in an X-ray apparatus. It is a figure which shows the pulse waveform of the electron beam which the accelerating tube used with X-ray apparatus outputs, (a) in a figure shows a macro pulse, The figure (b) shows the micro pulse which comprises a macro pulse. It is a block diagram which shows the example of an equipment configuration of X-ray apparatus. It is a block diagram for demonstrating the example of the control method of a X-ray apparatus. It is a block diagram which shows the example of an equipment configuration of X-ray apparatus.
  • FIG. 2 is a block diagram showing an apparatus configuration of an X-ray apparatus used in the X-ray apparatus. It is a control block diagram for demonstrating the operation
  • FIG. 2 is a block diagram showing an apparatus configuration of an X-ray apparatus used in the X-ray apparatus. It is a control block diagram for demonstrating the operation
  • FIG. 2 is a block diagram showing an apparatus configuration of an X-ray apparatus used in the X-ray apparatus. It is a control block diagram for demonstrating the operation
  • FIG. 1 is a block diagram showing an apparatus configuration of an X-ray apparatus according to the present invention. It is a control block diagram for demonstrating the operation
  • CT Current Transformer
  • FIG. 1 is a block diagram showing an exemplary configuration of an X-ray apparatus according to an aspect of the present invention.
  • the X-ray apparatus 1001 shown in FIG. 1 when the spot size of the electron beam 105 emitted toward the target 102c is reduced, the amount of heat generation per unit area at the irradiation position on the target 102c becomes large. Become high and cause damage to the target.
  • the present inventors estimate the temperature reached by the target 102c based on the information on the state of the electron beam 105, and parameters related to the emission of the electron beam 105 so that the estimated reached temperature does not exceed a predetermined temperature.
  • An example of the X-ray apparatus for embodying the control method includes an X-ray target 102c, an X-ray generation unit 102 that generates an X-ray 100, and a power supply 101 that supplies high voltage and high frequency to the X-ray generation unit 102.
  • the X-ray apparatus 1001 is an X-ray apparatus 1001 including an estimation unit 108 which obtains information on the state of the electron beam 105 from the respective parts and estimates the reached temperature of the target 102c (FIG. 1).
  • the power source 101 includes an electron gun power source 101a for supplying power to the electron gun 102a, a high voltage power source 101b for supplying high voltage and high frequency to the accelerating tube 102b, and a high frequency source 101c.
  • the electron beam is integrated by combining the portion related to the electron beam irradiation to the X-ray target 102c in the X-ray generation unit, the power source 101, and the component related to the emission of the electron beam. It is called a source.
  • the electron beam source includes an electron gun for generating an electron beam and its additional components, an accelerating electrode or accelerating tube for accelerating the electron beam and its additional components, the direction of the electron beam, Magnetic lenses and the like that control diameter, divergence and focusing, and their additional components, control electrodes (grid electrodes) that control the generation timing of the electron beam, a control unit that integrally controls them, and their required frequency It may include a power supply unit or the like that supplies current and voltage.
  • the estimation unit 108 includes an arithmetic unit 103 and a storage unit 106 that holds a relational expression for target temperature estimation and / or a reference conversion table.
  • the estimation unit 108 estimates the reached temperature of the target 102 c with respect to the temperature rise of the target 102 c due to the irradiation of the electron beam 105. Then, a control parameter regarding emission of the electron beam of the X-ray apparatus 1001 is determined so that the estimated ultimate temperature does not exceed the predetermined upper limit temperature.
  • the control parameters relating to the emission of the electron beam 105 control the state of the electron beam with which the target 102c is irradiated, that is, the energy of the electron beam, beam current, beam size, macro pulse width, repetition frequency of macro pulse, etc.
  • Parameters of the electron beam source include the electron gun voltage, the electron gun current, the driving voltage of the RF source, and the driving current of the RF source. Also, actual measurements of the state of the electron beam 105 may be included in the control parameters in aspects of the invention. These control parameters will be described in detail later.
  • the above-mentioned predetermined upper limit temperature may be a temperature at which the target 102c is actually damaged, or may be a temperature obtained by subtracting a constant value from the temperature at which the target 102c is damaged. Furthermore, it may be a temperature calculated by multiplying the temperature at which the target 102c is damaged by a predetermined safety factor.
  • the constant value may be, for example, an absolute value of temperature such as 10 ° C., 20 ° C.,... 100 ° C.
  • the safety factor is a factor lower than 100% such as 95%, 90%, 85%, 80% It may be.
  • the aforementioned constant value and safety factor should be determined within the scope of the effect of the aspect of the present invention that the target 102c is not damaged.
  • the above-mentioned predetermined temperature may be referred to as threshold temperature or allowable temperature.
  • the estimated ultimate temperature of the target in the aspect of the present invention an estimated value of the maximum temperature reached by the target in a macro pulse described later can be adopted.
  • the melting point of the material of the target 102c can be selected as the temperature at which the target 102c is damaged.
  • the melting point may be replaced with a softening point.
  • the recrystallization temperature may be employed instead of the melting point or the softening point.
  • the material of the target 102c may be directly heated experimentally to confirm the relationship between the temperature and the presence or absence of damage.
  • the temperature at which the target is damaged in the present specification is a concept including the temperature at which the target starts to be damaged. These temperatures are sometimes referred to as damage onset temperatures in the present invention.
  • the control parameter related to the emission of the electron beam may be a set value or a measured value.
  • the temperature of the target 102c may be directly measured, and the control parameter related to the emission of the electron beam may be controlled based on the measured temperature.
  • control parameters can be controlled by the following procedure.
  • a computer simulation is performed to obtain a relational expression between the control parameter relating to the emission of the electron beam and the estimated arrival temperature of the target 102c.
  • the control parameters set for the emission of the electron beam are applied (substituted) to calculate (estimate) the estimated arrival temperature of the target 102c.
  • the control parameter is corrected to decrease the estimated attainment temperature
  • the estimated ultimate temperature is recalculated, and this is repeated to set control parameters so that the target 102c is not eventually damaged.
  • the allowable temperature threshold temperature which is a temperature lower than the damage start temperature by a predetermined temperature
  • the estimated ultimate temperature calculated by the above relational expression is allowable.
  • the allowable temperature may be a temperature obtained by multiplying the damage initiation temperature by a predetermined safety factor, for example, a temperature obtained by expressing the melting point of the material in degrees Celsius by a 90% safety factor.
  • the estimated arrival temperature may be calculated using the relation obtained in the above (1) from the setting value of the control parameter as described above, or the measured value of the control parameter (measured The estimated arrival temperature may be calculated using the value) in the above relation. If a certain correlation exists between the set value and the actual value, the actual value may be estimated based on the set value. Further, the above relational expression may be stored in the storage unit 106, and the estimated arrival temperature may be calculated using the setting value or the measured value of the control parameter, and instead of the relational expression, the above relational expression or experimental expression etc. The relationship between the control parameter and the estimated ultimate temperature is created as a table and stored in the storage unit 106, and the estimated ultimate temperature corresponding to the set value or measurement value of the control parameter is determined using this table. You may do so.
  • the control parameter of the electron beam source is first set and the ultimate temperature of the target 102c is initially estimated, if the estimated ultimate temperature becomes equal to or higher than a predetermined temperature, the control parameter is changed and the target is again set. The ultimate temperature of 102c is estimated and this process is repeated until there is no risk of damage to the target 102c.
  • the control parameter to be changed in the above process is at least one of the control parameters of the electron beam source.
  • components other than the electron gun power supply 101a and the high frequency power supply high voltage power supply 101b may be controlled. If the estimated ultimate temperature becomes equal to or higher than the temperature that damages the target 102c or the above-described allowable temperature, the display device displays a warning that the control parameter is to be changed because the estimated ultimate temperature has exceeded the limit. It may be notified by voice or sound.
  • the X-ray apparatus and the control method of the X-ray apparatus are, for example, an X-ray source (a configuration in which the power supply 101 and the X-ray generation unit 102 are combined or The temperature of the target 102c (in the case of an X-ray tube, the target 104c) is estimated from the state of the configuration), and the control parameter of the X-ray source is adjusted to a temperature at which the target is not damaged.
  • an X-ray source a configuration in which the power supply 101 and the X-ray generation unit 102 are combined or
  • the temperature of the target 102c in the case of an X-ray tube, the target 104c
  • the specific control method will be described.
  • the maximum temperature in the macro pulse is estimated as the estimated ultimate temperature of the target unless otherwise specified, and control of the X-ray source is performed so that the estimated ultimate temperature does not exceed the damage initiation temperature or the allowable temperature of the target.
  • the mode to carry out will be described. Although the following description may be made using either the damage start temperature or the allowable temperature, these are merely examples of the embodiment, and in practice, the configuration of the X-ray apparatus and the control loop Depending on the time constant or the like, whether the threshold temperature is the damage start temperature or the allowable temperature can be arbitrarily selected.
  • the damage state of the target 102c is determined by the temperature of the position irradiated with the electron beam. However, direct measurement of the temperature is extremely difficult.
  • the temperature of the target 102c can be estimated by calculation. If the temperature of the target 102c can be estimated, damage to the target 102c can be prevented by controlling the control parameters of the X-ray source.
  • the parameters of the electron beam that can be used to estimate the temperature of the target 102c are shown below.
  • Kinetic energy or accelerating voltage of electron beam (2) Electron beam current (3) Electron beam size (4) Macro pulse width and repetition frequency
  • a method of acquiring these electron beam parameters a method of measuring an electron beam directly There is a method to calculate indirectly from control parameters of X-ray source and X-ray source. In the case of the former, it can be measured by the method shown in Table 1.
  • Various numerical values derived from the measured amounts or control parameters (also referred to as operating parameters) shown in Table 1 or Table 2 are input to the arithmetic device 103.
  • the arithmetic unit 103 calculates the state of the electron beam from these input values.
  • the state of the electron beam can be specified by parameters such as energy, voltage value, current amount, pulse width (macro pulse) and repetition frequency.
  • the arrival temperature of the target 102c is estimated from the state of the electron beam. If it is estimated that the ultimate temperature will be above the temperature that damages the target 102c, the control parameters of the X-ray source are limited to prevent the damage. Control parameters of the X-ray source in the present embodiment are shown in Table 3 below. By properly controlling one or more of the control parameters, damage to the target 102c can be prevented.
  • the energy density of the electron beam 105 on the target 102c is inversely proportional to the square of the diameter of the electron beam when the energy of the electrons is constant. Therefore, as the spot size of the electron beam is narrowed by the magnetic lens, the temperature reached by the target 102c rises sharply.
  • the electron beam generated by the electron gun 102a is guided to the accelerating tube 102b and accelerated there to an energy of 950 [keV].
  • energy for acceleration is supplied by RF of 9.3 GHz.
  • the electron beam is bunched (mass of electrons: one micro pulse) to a frequency of 9.3 [GHz] in the accelerating tube. Then, the bunched electron beam collides with the target 102c, and part of the energy is converted into X-rays. Most of the energy is heat.
  • energy for acceleration is supplied by RF of 1 to 20 GHz.
  • the energy 950 [keV] of the electron beam and the frequency 9.3 [GHz] of the RF are one example and may be changed according to the required system.
  • the energy of the electron beam is often several hundred keV to several tens of MeV.
  • FIG. 3 shows a time axis waveform of a bunched electron beam.
  • the macro pulse shown in (a) there is a bunched micro pulse as shown in (b).
  • F rep in the figure is the repetition frequency of the macro pulse.
  • pulsed high power RF pulsed RF
  • the macro pulse width is approximately 0.2 to 2.4 [ ⁇ sec]. Since a bunch of electron beams is generated at 9.3 [GHz] in the macro pulse, as shown in FIG. 3 (b), about 1800 to 22000 micro pulses (bunches) are contained in one macro pulse. Exists.
  • I b is the average current of the electron beam in the macro pulse
  • t w is the macro pulse width.
  • the relationship between the size of the electron beam on the target (equal to the spot size of the x-ray) and the temperature reached of target 102c can be calculated.
  • the estimated ultimate temperature which is the maximum temperature reached by the target 102c is the temperature when the beam does not hit the target 102 c and the temperature rise within the macro pulse width. It is also possible to express by the sum of the average temperature rise by the electron beam. According to the study of the present inventors, in the X-ray apparatus having the above-described configuration, the estimated ultimate temperature T [K] reached by the target 102c is It can be expressed as.
  • the first term T w on the right side represents the temperature [K] at the inlet of the target cooling water
  • the second term represents the temperature rise within the macro pulse width time
  • the third term represents the temperature rise of the base.
  • I b is the average current [A] of the electron beam
  • tw is the macro pulse width [sec]
  • f rep is the repetition frequency of the macro pulse [pps]
  • D is the diameter of the electron beam (FWHM) [mm].
  • ⁇ , ⁇ and ⁇ are constants depending on the electron beam voltage and the electron beam energy.
  • the second term represents the maximum value of the temperature rise of the target 102c in the macro pulse. This temperature rise is proportional to the beam current and the macro pulse width, and inversely proportional to the square of the electron beam size (D + ⁇ ) in the target 102c. ⁇ represents the spread of the electron beam in the target 102c.
  • a radiation simulation code is used to calculate heat generation in a simulation used when an electron beam is incident on the target 102c. Based on this heat generation, the temperature is calculated by a simulation code that solves the heat diffusion equation to calculate the temperature rise at the position where the estimated reaching temperature is reached. ( ⁇ , ⁇ , ⁇ ) can be obtained by performing the least square approximation on the calculation result with the above equation (1).
  • the above equation (1) and various setting numerical values and input numerical values (control parameters, operating parameters) show an example of calculation, and the relationship between the electron beam parameters and the reached temperature of the target 102c is also shown under other conditions. Can be calculated.
  • the reached parameter of the electron beam source and the reached temperature of the target 102c previously obtained by computer simulation using the above equation (1) are stored in the storage unit 106 as a table. It is also possible to make a table the numerical values obtained in the experiment.
  • FIG. 4 is a block diagram showing an apparatus configuration of a modified example 1002 of the X-ray apparatus according to the aspect of the present invention.
  • symbol and description in a figure are suitably abbreviate
  • Table 4 below shows control parameters of the X-ray apparatus 1002.
  • the X-ray apparatus 1002 of FIG. 4 includes an ML power source 110 for driving the magnetic lens ML and the magnetic lens ML, in addition to the elements of the X-ray apparatus 1001 described in FIG. 1.
  • the x-ray apparatus 1002 accelerates the electron beam to high energy at radio frequency (RF). Then, the electron beam is focused on the target 102c by a magnetic lens (ML: Magnetic Lens).
  • Power supply (101)... Supply power to the X-ray generation unit. It includes an electron gun power source 101a, a high frequency source high voltage source 101b, and a high frequency source 101c described below.
  • X-ray generation unit (102) It includes an electron gun 102a, an accelerating tube 102b, and a target 102c described below.
  • Electron gun power supply (101a)... Supplies power for driving the electron gun 102a.
  • Radio frequency source (101c) .. Generate radio frequency (RF) necessary for acceleration. Usually, a magnetron or a klystron is used. Magnetic lens power supply (ML power supply) ⁇ ⁇ ⁇ Supply a current for generating a magnetic field to the magnetic lens.
  • Electron gun (102a) ⁇ ⁇ ⁇ Generates electrons, accelerates to a certain extent, and supplies an electron beam to the accelerating tube.
  • the accelerating tube (102b) accelerates the electron beam to high energy using high frequency.
  • the electron beam is focused by the magnetic field (see FIG. 26).
  • the target (102c)... Made of metal such as tungsten and generates X-rays by collision of the electron beam.
  • Target current monitor (102d) ⁇ Monitor for observing the current waveform of the target 102c (see FIG. 25).
  • Arithmetic unit (103) ⁇ ⁇ ⁇ To determine the control parameters of the X-ray source and control the X-ray source, calculate the ultimate temperature of the target 102c from the measurement results of the state of the X-ray source and the control parameters of the X-ray source apparatus.
  • Storage unit (106) ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ presume estimation information and allowable temperature.
  • the estimated information is, for example, information representing the above equation (1).
  • a computer is used in the arithmetic device (103) and the storage unit (106), and the input / output device of the computer also functions as the input / output device of the device of this aspect.
  • FIG. 5 shows a block diagram of control for preventing damage to the target 102c.
  • the control method in the apparatus of FIG. 5 estimates the ultimate temperature of the target 102c from various measurement data, and resets the electron beam current emitted from the electron gun 102a so that the temperature does not exceed the damage start temperature of the target 102c. .
  • This control loop prevents the ultimate temperature of the target 102c from exceeding the damage initiation temperature of the target 102c.
  • An example of a specific operation is as follows. (1) From the electron beam current I b and the macro pulse width t w , the macro pulse repetition frequency f rep , the electron beam energy E b and the electron beam size D, the ultimate temperature T of the target 102 c at the irradiation position of the electron beam is calculated.
  • control parameters necessary for the calculation are obtained as follows.
  • the electron beam current I b By analyzing the current waveform at the target 102c, the electron beam current I b , the macro pulse width t w and the macro pulse repetition frequency f rep are obtained.
  • RF power P rf is obtained by analyzing the supply voltage V RF of the magnetron. The relationship between V RF and P rf is previously measured or calculated. Obtain the energy of the electron beam from the electron beam current I b and the RF power P rf . The relationship between I b and P rf is previously measured or calculated. Obtain the size D of the electron beam on the target 102 c from the current I C of the magnetic lens (ML) and the electron beam energy E b . These relationships are previously measured or calculated.
  • the reached temperature T of the target 102c is estimated using these control parameters. It is determined whether the estimated ultimate temperature T of the target 102c is lower than the temperature that damages the target 102c. (3) If the ultimate temperature T is lower than the damage initiation temperature of the target 102c (T ⁇ T d ), the control unit uses the control parameters used for estimation to control the outgoing beam current of the electron gun 102a. (4) When the ultimate temperature T is equal to or higher than the damage start temperature of the target 102c (T ⁇ T d ), the ultimate temperature T of the target 102c is estimated by changing the value of the control parameter used for estimation. This is repeated until the temperature is lower than the damage initiation allowable temperature of the target 102c.
  • Changing the values of the control parameters for example, varying the electron beam current by changing the grid pulse voltage V g of the electron gun.
  • the damage of the target 102c is prevented by controlling the electron beam current Ib, but the damage of the target 102c is prevented by controlling the beam energy and the beam duty ratio (macro pulse width ⁇ macro pulse repetition frequency).
  • a control vector value such as an increase / decrease speed of the current value or the voltage value may be transmitted. The same applies to the other embodiments in the present specification.
  • the initial state of the electron beam may be T ⁇ Td , in which case target damage may occur in a short time. . Therefore, in the case of an apparatus that performs control based on measured values such as the electron beam state, it is desirable to start the electron beam irradiation after setting conditions that are confirmed in advance that no target damage will occur. Further, in the apparatus according to the aspect of the present invention, instead of the temperature T d at which the target 102 c is actually damaged, for example, an allowable temperature T L that is lower than the temperature at which the target 102 c is damaged is preset as the threshold temperature. You may leave it. Also, changing the value of the control parameter, instead of the grid pulse voltage V g, for example it may be performed by varying the electron beam current I b.
  • FIG. 6 is a diagram showing an apparatus configuration of the X-ray apparatus 1003.
  • FIG. 7 is a block diagram showing an example of control of the X-ray apparatus 1003.
  • a target current monitor 102d is added to the target 102c so that the actual target current can be measured.
  • the target current monitor 102d is used to measure an electron beam incident on the target. The principle of operation will be described later.
  • the target current monitor 102d can measure the waveform of the macro pulse. Further, the repetition frequency (f rep ), the electron beam current (I b ) and the macro pulse width (t w ) can be obtained by the waveform analysis of the macro pulse.
  • the electron beam size can also be stored in the storage unit.
  • the storage unit 106 stores in advance estimated information and an allowable temperature TL .
  • the estimated information is, for example, information representing the above equation (1). That is, the estimation information is information for estimating the estimated arrival temperature which is the highest temperature reached at the target 102c.
  • the allowable temperature T L is a temperature lower than the damage initiation temperature of the target 102 c. That is, the allowable temperature T L is a temperature in a temperature range that does not damage the target 102 c, and is set, for example, lower than a temperature that damages the target 102 c (minimum temperature in a temperature range that damages the target 102 c) It is a temperature.
  • the computing device 103 sets the following initial parameters based on the electron beam size D and the desired X-ray energy. .
  • Arithmetic unit 103 estimates the estimated arrival temperature from the above-mentioned parameters using the above-mentioned estimation information.
  • (temperature at the cooling water inlet) T w in the formula (1) the user may be detected by a sensor (not shown) may be manual input.
  • Arithmetic unit 103 compares the estimated temperature that has been estimated with the allowable temperature stored in storage unit 106 before starting operation. If the estimated ultimate temperature is equal to or lower than the allowable temperature, the computing device 103 adopts the set parameter. That is, the arithmetic device 103 controls the electron beam current based on the set parameters at the start of operation. Then, after the start of operation, the estimated arrival temperature can be estimated using various parameters obtained from the measurement results of the target current monitor 102d.
  • the arithmetic device 103 When the estimated ultimate temperature exceeds the allowable temperature, if the parameter is adopted as it is and operation is started, the target 102c is damaged. Therefore, the arithmetic device 103 resets the control parameter so that the estimated arrival temperature becomes lower, and performs the above operation again. Arithmetic unit 103 repeats this operation until the estimated ultimate temperature becomes equal to or lower than the allowable temperature, and then starts operation.
  • the estimation information may be a table indicating the relationship between the control parameters described above.
  • the table which shows the relationship between the above-mentioned control parameter and presumed arrival temperature in Drawing 8 is illustrated.
  • the table 400 includes a plurality of different combinations of the electron beam current I b , the macro pulse width t w, and the macro pulse repetition frequency f rep . Even when such a table is used, the same control as in the case of using the above-described equation (1) can be performed.
  • the electron beam size exceeds a certain threshold determined by the maximum temperature of the target, the system is configured to issue a message prompting the user to reset the electron beam size.
  • the pulse repetition number can be lowered, the macro pulse width can be narrowed, and the beam current can be decreased. It is also possible to display a message prompting the user to make these settings.
  • FIG. 9 is a flowchart of control processing in the estimation unit.
  • the arithmetic unit 103 sets initial control parameters.
  • the computing device 103 estimates the estimated arrival temperature from the set control parameter.
  • the arithmetic unit 103 compares the allowable temperature with the estimated ultimate temperature. If the estimated ultimate temperature is equal to or higher than the allowable temperature, the arithmetic device 103 proceeds with the process to step S40.
  • the arithmetic unit 103 resets the control parameter so that the estimated ultimate temperature becomes lower, and the process proceeds to step S20.
  • step S50 the arithmetic unit 103 controls the electron gun power supply 101a and the high frequency power supply high voltage power supply 101b to emit an electron beam from the X-ray generation unit 102 toward the target 102c.
  • the emission of the electron beam may be performed automatically, or a message for permitting the user to start driving may be displayed to prompt the emission of the electron beam.
  • FIG. 10 is a block diagram showing an apparatus configuration of the X-ray apparatus 1004.
  • the electron gun power supply 101a is controlled based on the target current waveform at the target 102c.
  • control parameters related to the electron beam source include parameters related to the high frequency power supply 101b as well as parameters related to the electron gun power supply 101a.
  • the apparatus of this configuration since the electron beam is subjected to high frequency modulation by the accelerating tube, it is desirable to measure the electron beam current irradiated to the target 102c and the waveform thereof.
  • the reached temperature of the target 102c can be estimated from these measurement results.
  • These electron beam parameters are input to the arithmetic unit 103 to estimate the reached temperature of the target 102c. Then, the electron gun power supply 101a is controlled so that the temperature does not reach the damage start temperature of the target 102c.
  • FIG. 11 is a control block diagram in the case of controlling the electron gun power supply 101a from the current waveform in the target 102c.
  • the following parameters are input to the arithmetic device 103 in advance.
  • Electron beam size D In order to estimate the reached temperature of the target 102c, the electron beam current I b and the macro pulse width t w and the repetition frequency f rep are calculated by waveform analysis from the measurement value of the target current monitor. Instead of the target current monitor, it is also possible to use a CT or a wall current monitor. Estimating the temperature from the measured results to control the grid pulse voltage V g of the electron gun 102a based on it. By this voltage control, the electron beam current is controlled by the grid (not shown) voltage to prevent damage to the target 102c.
  • FIG. 12 is a diagram showing an apparatus configuration of the X-ray apparatus 1005.
  • a specific control method of the device of FIG. 12 will be described with reference to FIG.
  • FIG. 13 is a control block diagram in the case of controlling the high-frequency source high-voltage power supply 101b using the current waveform of the target 102c.
  • the following parameters are input to the arithmetic unit 103 in advance.
  • Electron beam size D In order to estimate the reached temperature of the target 102c, the electron beam current I b and the macro pulse width t w and the repetition frequency f rep are calculated by waveform analysis from the measurement value of the target current monitor. Instead of the target current monitor, it is also possible to use a CT or wall current monitor described later.
  • the electron beam energy E b is calculated from the voltage V RF of the high frequency source 101 c . It is also possible to measure the RF power and then calculate the electron beam energy E b . The reached temperature of the target 102c is estimated from these measurement results and calculation results, and based on that, the voltage V RF of the high frequency source 101c is controlled. This voltage control controls the electron beam current to prevent damage to the target 102c.
  • FIG. 14 is a block diagram showing the apparatus configuration of the X-ray apparatus 1006, which controls the electron gun power supply 101a from the information of the high frequency power source high voltage power supply 101b and the electron gun power supply 101a.
  • the X-ray apparatus 1006 controls the electron gun power supply 101a from the information of the high frequency power source high voltage power supply 101b and the electron gun power supply 101a.
  • an accelerating tube it is possible to calculate electron beam parameters using the operation parameters of the high frequency power source high voltage power source 101b and the electron gun power source 101a.
  • the calculated electron beam parameters are input to the arithmetic unit 103 to estimate the target temperature.
  • the electron gun power supply 101a is controlled so that the temperature does not exceed the allowable temperature of the target 102c.
  • the storage unit 106 stores the following relationships in advance as a table, an expression, or the like. Relationship between cathode current I k and RF power P rf of electron gun 102 a and target current (beam current) I b Relationship between voltage V RF of RF source 101 c and RF power P rf Target current (beam current) I Relationship between b and RF power P rf and electron beam energy E b These relationships can be obtained in advance by calculation and measurement.
  • the control system 15 controls the grid pulse voltage V g of the electron gun 102a on the basis of the information about the state of the electron gun power supply 101a and RF source high voltage power source 101b (operating parameter). This voltage control controls the electron beam current to prevent damage to the target 102c.
  • FIG. 16 is a block diagram showing an apparatus configuration of the X-ray apparatus 1007.
  • the X-ray apparatus 1007 includes a spot size measurement unit 111, and measures an X-ray spot size to control the electron gun 102a.
  • the spot size of the X-ray fluctuates with constant electron beam energy, electron beam current, macro pulse width and repetition frequency.
  • the spot size of the x-rays can be considered identical to the beam size of the electron beam striking the target 102c. In this case, the ultimate temperature of the target 102c can be calculated from the measurement results of the X-ray spot size.
  • a specific control method will be described with reference to FIG. FIG. 17 is a control block diagram in the case of controlling the electron gun power supply 101a from the X-ray spot size. The following parameters are input to the arithmetic device 103 in advance. ⁇ Electron beam energy E b .
  • FIG. 18 is a view showing the device configuration of the X-ray apparatus 1008, and is a block diagram in the case of measuring the X-ray spot size and controlling the high frequency power supply 101b.
  • FIG. 19 is a control block diagram in the case of controlling the high frequency power supply 101 b from the X-ray spot size.
  • the following parameters are input to the arithmetic device 103 in advance.
  • the arithmetic device 103 holds the following relationship in advance as a table or a relational expression.
  • FIG. 20 is a diagram showing an apparatus configuration of the X-ray apparatus 1009.
  • an X-ray tube 104 is used as an X-ray generator.
  • This type of X-ray tube is widely used for medical and industrial applications, and is an apparatus in which an electron gun 104a, an electrostatic acceleration unit 104b, and a target 104c are integrated.
  • FIG. 20 is a block diagram showing the configuration of an apparatus that controls the power supply 101d of the X-ray tube 104 to prevent damage to the target 104c.
  • the energy and current of the electron beam irradiating the target 104c correspond to the voltage and current output from the X-ray tube power supply 101d to the electron beam source.
  • the voltage and current output from the X-ray tube power supply are measured, and the measurement results are input to the arithmetic unit 103 to calculate (estimate) the ultimate temperature of the target 104c. Then, the arithmetic device 103 sets the voltage and current of the X-ray tube power supply so that the calculated ultimate temperature of the target 104c does not exceed the allowable temperature of the target 104c.
  • a specific control method of the configuration of FIG. 20 will be described using a control block diagram of FIG.
  • the electron beam parameters required to calculate the ultimate temperature of the target 104c are the electron beam current Ib and the electron beam voltage Vb . This is because the conventional X-ray tube operates continuously and the electron beam size at the target 104c is constant.
  • parameters for determining the temperature of the target 104c are the electron beam current Ib and the electron beam voltage Vb .
  • the operation of this control is as follows. (1) The measurement results of the electron beam current Ib and the electron beam voltage Vb of the X-ray tube power supply are transmitted to the arithmetic unit 103. (2) The computing device 103 calculates the ultimate temperature T m of the target 104 c from the parameters (I b , V b ) sent. (3) The calculated ultimate temperature T m of the target 104 c is compared with the damage start temperature T d of the target 104 c . (4) computing unit 103 in accordance with the following transmits the set value of the electron beam current I b to the X-ray tube power supply.
  • FIG. 22 is a cross-sectional view schematically showing the structure of the electron gun 102a.
  • the electron gun 102 a includes a cathode electrode 303, an anode electrode 304, a Wehnelt electrode 305, a grid 306, a heater 307, a first insulating portion 308, and a second insulating portion 309.
  • the electron gun 102a is provided with an H terminal, an HK terminal, and a G terminal.
  • the H terminal is connected to the heater 307.
  • the HK terminal is connected to the heater 307 and the cathode electrode 303.
  • the G terminal is connected to the grid 306 and the Wehnelt electrode 305.
  • the heater power supply 310 is connected to the H terminal and the HK terminal.
  • a grid power supply 311 is connected to the HK terminal and the G terminal.
  • a high voltage power supply 312 is connected to the G terminal.
  • the heater 307 generates heat due to the voltage applied by the heater power source 310 and applies heat to the cathode electrode 303.
  • the cathode electrode 303 is heated by the heater 307 and emits thermionic electron (electron beam) from the surface.
  • the cathode electrode 303 is heated to, for example, about 1000 degrees. With the emission of the electron beam, a beam current flows to the HK terminal.
  • the Wehnelt electrode 305 is an electrode on the cathode side.
  • the Wehnelt electrode 305 forms a predetermined electric field. This electric field focuses the electron beam emitted from the cathode electrode 303.
  • the anode electrode 304 is an electrode on the anode side. A hole is provided at the center of the anode electrode 304. The electron beam emitted from the cathode electrode 303 passes through this hole.
  • the grid 306 has, for example, a thin mesh shape.
  • the grid 306 controls the current of the electron beam emitted from the cathode electrode 303 by the voltage applied by the grid power supply 311.
  • the high voltage power supply 312 applies a voltage to the cathode side (for example, the Wehnelt electrode etc.) and the anode side (the anode electrode 304 side).
  • the voltage applied by the high voltage power supply 312 creates an electrostatic field to accelerate the electron beam.
  • the first insulating portion 308 electrically insulates the cathode side from the anode side.
  • the second insulating portion 309 electrically insulates the grid 306 and the Wehnelt electrode 305 from the cathode electrode 303.
  • the second insulating portion 309 requires, for example, a withstand voltage of about 100V.
  • the first insulating portion 308 requires a higher withstand voltage than the second insulating portion 309.
  • the beam current is changed. That is, the beam current is controlled by the voltage between the cathode electrode 303 and the grid 306. For example, the higher the potential of the grid 306 compared to the potential of the cathode electrode 303, the larger the beam current. Also, when the potential of the grid 306 is lower than a certain threshold value compared to the potential of the cathode electrode 303, the beam current emitted from the cathode electrode 303 becomes zero.
  • FIG. 23 is a perspective view and a cross-sectional view for explaining a basic principle (a) of CT (Current Transformer) and a basic configuration (b) when used for measurement of an electron beam current emitted from an accelerating tube.
  • the electron beam current can be known.
  • the electron beam travels in a vacuum, and the CT (ferrite core, secondary winding, etc.) itself is placed in the atmosphere. Therefore, the vacuum and the atmosphere have to be divided by the metal beam pipe 201d and the ceramic 201e.
  • the metal beam pipe 201d When all covered with metal, a mirror image current of the opposite current flows on the surface, and the current inside the ferrite is canceled, so no current flows in the secondary winding.
  • a ceramic 201e of an insulator is used as a part of the beam pipe 201d.
  • FIG. 24 is a diagram showing a basic principle (a) of a wall current monitor and a basic configuration (b) when it is used for measuring an electron beam current in an accelerating tube.
  • the wall current monitor is a monitor that measures the current due to the flow of the mirror image charge 202b inside the beam pipe 202a.
  • a mirror image charge (positive charge) 202b is generated as shown in FIG. 24 (a). It moves in the same direction as the beam. If the insulator is in the middle of the beam pipe 202a, the mirror image charge can not move there. However, when the pipe is connected by the conductor 202c as shown in FIG. 24 (b), the mirror image charge 202b moves there.
  • the current due to the mirror image charge is known. This current is the same amount and opposite in sign to the electron beam current. Therefore, the electron beam current can be known from the voltage across the resistor 202d.
  • the actual wall current monitor mounts multiple resistances along the beam pipe 202a. Thereby, the current due to the mirror image charge is made to flow smoothly.
  • FIG. 25 shows the configuration of the target current monitor.
  • the tungsten target 203a with which the electron beam collides is electrically connected to the ground potential via the resistor 203b. By measuring the potential difference across the resistor 203b, it is possible to measure the target current.
  • a magnetic lens (ML: Magnetic Lens) will be described as another component.
  • the schematic is shown in FIG.
  • a magnetic lens is a device that focuses an electron beam.
  • Magnetic field lines 204b created by flowing direct current through the coil 204a are confined in a yoke 204c made of metal with high permeability, and a notch is formed in a part of the yoke 204c to leak the magnetic field lines 204b into space and to be rotated make.
  • the electron beam incident along the central axis of the coil spirals in the magnetic field and is narrowed and focused at the focal point 204d.
  • FIG. 27 is an explanatory view schematically showing the relationship between the coil current of the magnetic lens ML and the spot diameter of the electron beam.
  • the magnetic lens ML has a coil 204a.
  • the spot diameter of the electron beam on the target 102c is controlled by a current (hereinafter referred to as a coil current Ic) supplied to the coil 204a.
  • a coil current Ic a current supplied to the coil 204a.
  • the focal length of the magnetic lens ML is shorter than the double shown in FIG. 27A, the electron beam is still not condensed on the target 102c.
  • the spread D2 of the electron beam on the target 102c is smaller than the spread D1 shown in FIG. 27A (having a spot diameter D2 smaller than D1).
  • the electron beam converges on the focal length of the magnetic lens ML at this current, and then diffuses and reaches the target 102c. Therefore, the electron beam has a spread D4 (large spot diameter D4) larger than the spread D3 shown in FIG. 27 (c).
  • FIG. 28 is an explanatory view schematically showing the relationship between the coil current Ic and the spot diameter of the electron beam in the target 102c.
  • the horizontal axis in FIG. 28 indicates the coil current Ic of the magnetic lens ML, and the vertical axis indicates the beam size (spot diameter) on the target 102c.
  • the beam size on the target 102c changes depending on the coil current Ic.
  • FIG. 29 shows a basic configuration of an X-ray CT (Computer Tomography) apparatus for a nondestructive inspection apparatus.
  • the X-rays emitted from the optional X-ray apparatus 100a according to the present invention disposed in the X-ray shielding chamber 205d pass through the test object 205a, and the transmitted X-rays are detected by the image detector 205b. Since the test subject 205a is mounted on the rotating sample stage 205c, it is possible to obtain fluoroscopic images viewed from various angles.
  • the X-ray data detected by the image detector 205b can be converted into a perspective stereoscopic image and reconstructed on the monitor 205f by being reconstructed by the image processing device (computer 205e).
  • the computing device 103 may estimate the temperature of the target 102 c using information different from the information described in each of the above-described devices. For example, the computing device 103 may directly use information representing beam energy, beam current, beam size, pulse width, etc.
  • the temperature information of the target 102c may be estimated using (2)
  • the state of the target 102c estimated by the arithmetic device 103 may be other than the temperature of the target 102c. For example, a state other than the temperature representing the damaged state of the target 102c may be estimated.
  • the X-ray apparatus and the method of using the X-ray apparatus according to the aspects of the present invention can be widely used not only in the nondestructive inspection X-ray apparatus but also in the field using X-rays.

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  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
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  • X-Ray Techniques (AREA)
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Abstract

L'invention concerne un dispositif à rayons X comprenant : une cible qui génère des rayons X lorsqu'elle est irradiée avec un faisceau d'électrons ; une source de faisceau d'électrons qui émet le faisceau d'électrons vers la cible ; une unité d'évaluation qui évalue l'état de la cible sur la base d'informations concernant l'état du faisceau d'électrons ; et une unité de commande qui commande la source de faisceau d'électrons sur la base de l'état de la cible évalué par l'unité d'évaluation.
PCT/JP2018/046351 2017-12-18 2018-12-17 Dispositif à rayons x et procédé de commande de dispositif à rayons x WO2019124309A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52101375U (fr) * 1976-01-28 1977-08-01
JPS5730299A (en) * 1980-07-12 1982-02-18 Philips Nv Method and device for controlling power supplied to rotary anode type x-ray tube
US4363971A (en) * 1979-07-05 1982-12-14 U.S. Philips Corporation Method of and apparatus for controlling the electric power applied to a rotary-anode X-ray tube
JP2012526345A (ja) * 2009-05-05 2012-10-25 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Ｘ線生成装置の焦点スポットの負荷依存サイズ変更のための方法および装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52101375U (fr) * 1976-01-28 1977-08-01
US4363971A (en) * 1979-07-05 1982-12-14 U.S. Philips Corporation Method of and apparatus for controlling the electric power applied to a rotary-anode X-ray tube
JPS5730299A (en) * 1980-07-12 1982-02-18 Philips Nv Method and device for controlling power supplied to rotary anode type x-ray tube
JP2012526345A (ja) * 2009-05-05 2012-10-25 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Ｘ線生成装置の焦点スポットの負荷依存サイズ変更のための方法および装置

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