Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/26—Measuring, controlling or protecting
  • H05G1/265—Measurements of current, voltage or power
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/10—Power supply arrangements for feeding the X-ray tube
  • H05G1/22—Power supply arrangements for feeding the X-ray tube with single pulses
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/02—Constructional details
  • H05G1/04—Mounting the X-ray tube within a closed housing
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/10—Power supply arrangements for feeding the X-ray tube
  • H05G1/20—Power supply arrangements for feeding the X-ray tube with high-frequency ac; with pulse trains
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/26—Measuring, controlling or protecting
  • H05G1/30—Controlling
  • H05G1/34—Anode current, heater current or heater voltage of X-ray tube
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/70—Circuit arrangements for X-ray tubes with more than one anode; Circuit arrangements for apparatus comprising more than one X ray tube or more than one cathode
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J35/00—X-ray tubes
  • H01J35/02—Details
  • H01J35/14—Arrangements for concentrating, focusing, or directing the cathode ray
  • H01J35/147—Spot size control

Definitions

• a method for driving an X-ray tube is known, for example, from US Pat. No. 7,751,528 B2.
• the x-ray system is designed as a tomosynthesis system which has a large number of stationary x-ray sources arranged in a row.
• x-ray tubes have electron emitters whose function can be based on various physical principles.
• dispenser cathodes are mentioned as thermal emitters.
• Electronic control devices for multi-focus X-ray tubes whose cathodes are provided for the thermal emission of electrons, are known for example from the documents EP 1 617 764 Bl and EP 1 618 368 Bl.
• Emitters that contain nanorods, in particular carbon nanotubes are particularly suitable for the field emission of electrons.
• a method for emission current control for X-ray tubes is disclosed in DE 10 2009 017 649 B4.
• a current regulation can be superimposed on a voltage regulation.
• the invention is based on the object, the control of X-ray tubes, in particular X-ray tubes with field emission cathodes, compared to the prior art
• the drive device is provided for actuating an X-ray tube which comprises an anode formed as an X-ray emitter and a plurality of cathodes which are provided for generating electron beams directed onto the anode.
• a housing designed as a shield, in which an anode current control unit is arranged.
• the anode current control unit is connected to a cathode power supply unit, with a plurality of each to be connected to a cathode cathode voltage switching, as well as with a
• the cathode power supply unit, the cathode voltage switch, and the programmable module are arranged in said housing.
• the shielded housing of the power and control electronics for the X-ray tube in the common housing together with a suitable board layout the electromagnetic radiation is significantly reduced compared to conventional solutions.
• the programmable module of the drive device comprises, for example, an FPGA (Field Programmable Gate Array) and at least one digital-to-analog converter.
• Power source is controlled by the FPGA or other programmable device or an array of such devices via the at least one digital-to-analog converter.
• the FPGA or an equivalent feature controls a number of subsystems. Possible subsystems in the present case are the voltage supply unit-that is to say the energy supply unit-of the cathodes, an anode energy supply unit, various supply units for focusing devices and gratings, and a current source to be allocated to the anode current control unit
• the FPGA is already programmed prior to performing a pulse train of the cathodes in such a way that the pulse sequence is triggered in real time.
• the timing of the pulse sequence is purely by the FPGA or a functionally identical element.
• two A / D converters are respectively programmed with the voltage value corresponding to the equivalent current.
• the boost here means a peak generated at the beginning of the pulse with which a rectangular shape of the pulse is achieved in comparison to pulses which are generated without a short-term voltage increase, with improved approximation to the theoretical ideal shape.
• High voltage switch bank formed with a number of MOSFETs.
• a plurality of MOSFETs are optionally connected in series within a single cathode voltage switch.
• the anode current control unit makes it possible to regulate the electron current emitted by the cathodes, that is to say electron emitters, from cathode to cathode in real time.
• an actual current flowing through the anode and an assigned desired value enter into the regulation.
• currents which flow through extraction grids and through focusing devices can enter into the control.
• the order in which the high-voltage switches are controlled by the FPGA is freely programmable, the order and number of emitters used can also be freely programmed. Thus, not all emitters must be operated and the X-ray tube can also be operated as a single-beam tube. If a corresponding multiplexer is used, several or all channels can also be activated simultaneously and thus electron emitters activated in parallel.
• the thermal spot size on the anode can be adjusted individually from emitter to emitter.
• the thermal focal spot size is to be considered without projection.
• the X-ray focal spot size to be considered under a projection.
• the focal spot size can be adjusted by the variation of the grid voltage, also in the form of a fine tuning. This applies both in continuous mode and for a pulsed mode, wherein in each case different settings are possible from emitter to emitter.
• a monitoring of the drive device is particularly important in terms of flashovers, which are conceivable during operation of the X-ray tube due to the high voltages at the anode, of importance.
• a rollover is a short between
• the electron emitter and anode In the anode current can lead to a current peak that lasts only nanoseconds. Due to the speed of the anode current control in the microsecond range, this current pulse is controlled by the controller
• Detection mechanism depends almost exclusively on the duration of the detection of the comparator. Depending on the comparator, this is in the pico or nanosecond range. As soon as the maximum value is exceeded, the digital value of the comparator is transmitted by means of an optocoupler via a further connecting cable between the anode power supply unit and the voltage supply unit of the cathodes and
• dispenser cathodes are used as electron emitters.
• the cathodes of the x-ray tube are field emission cathodes, in particular cathodes with nanorods, that is nanosticks.
• pulsed operation of the cathodes pulsed operation of the anode of the x-ray tube is also possible in a preferred embodiment. This is by a
• Anodennapssmakersshim provided a DC voltage in the form of a pulsed unipolar voltage.
• the anode voltage supply unit which is attributable to the drive device, preferably comprises a Marx generator.
• the level of voltage pulses applied to the anode may differ from pulse to pulse.
• Cathode current is different. Therefore, even without active control by determining the transmission factor in an initial calibration run and storing the transmission factor in a lookup table, the anode current can be adjusted. These two control methods can also be combined so that the transmission factor is first determined and the anode current is adjusted with this and thereafter the anode current is kept constant even with a change in the transmission rate with the analog or digital control.
• the X-ray tube can be generated by the aforementioned focusing devices, which are each associated with a cathode, focal spots on the anode, which are different from cathode to cathode.
• a variation of the focal spot size is possible both with constant anode voltage and with pulsed anode voltage with different voltage from pulse to pulse. Likewise, the possibility exists, the
• Wavelengths are tunable to X-ray absorption properties of various materials located in the object of interest. In this way it is very easy to distinguish between different materials in the examination subject. This is preferably done in a stationary, in particular non-rotating, arrangement of the X-ray sources.
• FIG. 11 is a block diagram of the structure of a high-voltage switch bank, which is supplied via the power source in Fig. 10 with energy,
• Fig. 17 is a block diagram showing the structure of a cathode drive device of the
• X-ray device according to Fig. 1 generated current pulse.
• Components of the X-ray tube 2 are a cathode 4 as an electron source and a
• a focusing device 6 for the electron beam EB is a focusing device 6 for the electron beam EB.
• the electron source 4 is formed as a field emission cathode.
• a metallization 8 and an emitter layer 9, which contains carbon nanotubes, are located on a ceramic substrate 7.
• An extraction grid 10 is slightly spaced from the emitter layer 9.
• FIGS. 13 and 14 relate to X-ray devices 1 which are operated with dispenser cathodes.
• the X-ray device 1 supplied with the anode power supply unit 14 according to FIG. 13 has, within the X-ray tube 2, two gratings which are connected to electrical voltage via grid connections GA1, GA2. Furthermore, a heating element is present, which has a heating connection HA
• T1J2J3 trigger signals

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• X-Ray Techniques (AREA)
• Cold Cathode And The Manufacture (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2018
  • 2018-08-31 JP JP2020533345A patent/JP2020532089A/ja active Pending
  • 2018-08-31 WO PCT/EP2018/025225 patent/WO2019042587A2/de active Application Filing
  • 2018-08-31 US US16/643,526 patent/US11558950B2/en active Active
  • 2018-08-31 EP EP18765807.5A patent/EP3677100A2/de active Pending
  • 2018-08-31 CN CN201880056386.4A patent/CN111602470B/zh active Active

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