Fiber optic communication for embedded electronics in x-ray generators

Abstract

The X-ray source includes an optical communications link to provide galvanic isolated communications between the system controller and the gun controller. In a particular example, the link is provided through one or more optical fibers. In addition, the gun controller is preferably remotely programmed by the system controller during start-up. This addresses the problem of reprogramming the processor in locations / environments that are difficult to access. A watchdog timer is also useful for the gun digital processor of the gun controller.

Description

Technical Field

[0001] This application relates to the field of electron emission, and more specifically to an X-ray source. Background Technology

[0002] X-rays are widely used in microscopy due to their short wavelengths and ability to penetrate objects. Typically, the best X-ray sources are synchrotrons, but these are expensive systems. Therefore, so-called tube or laboratory X-ray sources are commonly used, in which a generated electron beam bombards a target. The resulting X-rays include characteristic lines determined by the target's composition and a wide range of bremsstrahlung radiation.

[0003] X-ray microscopy systems have several basic configurations. Some employ a condenser to focus X-rays onto the object under study and / or the objective lens, imaging the X-rays after interaction with the object. The resolution and aberrations associated with these types of microscopes are typically determined by the spectral characteristics of the X-rays. Some microscopy systems use a projection configuration, where a small X-ray source spot is typically used in conjunction with geometric magnification to image the object.

[0004] Performance, especially resolution, is affected by various factors. Because projection configurations have no aberrations, resolution is typically determined by the size of the X-ray source spot. Ideally, the X-ray source spot is a single point. In practice, X-ray source spots are much larger. Typically, the source spot size is determined by the electron optics and their ability to focus the electron beam to a point. Source spot sizes are generally around 50–200 micrometers (μm) with good electron optics; although in other examples, where power is a more significant quality factor, the X-ray source spot size may be 1–5 millimeters (mm). For transmission-target X-ray sources, spot sizes are typically a few micrometers, for example, 1 μm to 5 μm. In fact, some transmission sources have spot sizes as low as 150 nanometers (nm). In any case, the size of the X-ray source generally limits the resolution of X-ray projection microscopy.

[0005] For many microscopic applications, transmission target X-ray sources are frequently used. In the basic configuration of an X-ray tube, thermionic or field-emission electrons are generated at the cathode (filament) in a vacuum tube and accelerated to the anode (forming an electron beam shaped by various electrostatic and (electro)magnetic optical elements). For example, magnetic lenses typically use copper wire coils within iron poles. A current through the coil generates a magnetic field in the holes of the poles. Electrostatic lenses use charged dielectrics to generate an electrostatic field. The electron beam then strikes a target, typically thin, at its back. Common target materials are tungsten, copper, and chromium. The X-rays emitted from the front of the target are then used to irradiate the object.

[0006] X-ray sources typically require control electronics to adjust, control, and / or monitor the electron emission system (or electron "gun"). These electronic devices are often referred to as "gun controllers".

[0007] The gun controller is electrically connected to components of the electron gun, such as the filament, suppressor cathode, and lead-out cathode.

[0008] In many designs, the gun electronics rise to high voltages of several thousand volts during operation and require current isolation. This is because electrons are accelerated toward the positive electrode (anode). If the target needs to be close to the sample, it also needs to be grounded to avoid arcing on the sample. Therefore, the filament needs to be under a high negative voltage. Furthermore, the gun controller now also needs to be under a very high negative voltage.

[0009] Typically, gun control electronics are also encapsulated in epoxy resin or immersed in insulating oil. In any case, the gun control electronics are located in places that are difficult or impossible for maintenance personnel to reach. Summary of the Invention

[0010] More complex gun controllers require more intelligent control systems that employ digital control via digital processors such as central processing units (CPUs), digital signal processors (DSPs), or field-programmable gate arrays (FPGAs). All these digital control subsystems require programming, and if possible, reprogramming "in the field." Because they are typically located in physically inaccessible high-voltage environments, digital control is achieved remotely through current isolation provided to that high-voltage environment.

[0011] This invention relates to optical communication links to provide electrically isolated communication between a system controller and a gun controller. In a particular example, the link is provided via one or more optical fibers.

[0012] In this implementation, each optical fiber can transmit one or more signals together, and these signals are encoded using a specific communication protocol. Even bidirectional optical communication via a shared optical fiber can be employed.

[0013] The main advantages are the versatility of the communication method and the fact that only one or two optical fibers are needed in total to carry a virtually unlimited number of signals in each direction. Specific protocols include Gigabit Ethernet over one or more optical fibers.

[0014] This invention also relates to a digital control system and remote programming for a gun controller. The gun controller's digital processor requires some configuration to operate. Typically, this configuration is a program (for CPUs and DSPs) or a configuration file (for FPGAs) and is stored in non-volatile memory close to the processor. Upon power-up, the program or configuration file is loaded and executed by the digital processor. Sometimes the information is stored directly inside the processing chip, and sometimes it is stored in additional memory (such as flash memory).

[0015] The only drawback of this typical setup is the fact that the gun controller may operate in harsh X-ray environments, making the use of flash memory extremely dangerous. Sustained X-ray bombardment will slowly erase the memory and render it unreliable. It would be better if the program could be loaded "on the fly".

[0016] In this method, the gun controller includes a gun digital processor, and the system controller configures the digital processor upon power-up. This ensures that the operation of the digital processor is not damaged by long-term radiation surrounding the gun controller.

[0017] This configuration can be provided via a fiber optic link. One or more fibers of this link are then preferably used to continuously transmit data to the gun controller. Another fiber, or the same fiber, can transmit information from the gun controller back to the main system digital controller. This includes all necessary telemetry data, such as digitized voltage, current, temperature, etc.

[0018] The invention also relates to a monitor timer for a gun digital processor. If no communication occurs within a certain period, the gun digital processor will be reset. This allows the processor to be reprogrammed at any time.

[0019] Generally, according to one aspect, the present invention is characterized by an X-ray source comprising a system controller, a target, an electron source for generating electrons to form a beam that strikes the target to generate X-rays, a high-voltage generator for accelerating the beam, and a gun controller for controlling the electron source and receiving configuration from the system controller at each startup.

[0020] The source may include a source coil controlled by the gun controller.

[0021] The gun controller may include a field-programmable gate array (FPGA), and the system controller provides a configuration file to the digital processor upon power-up. In other cases, the gun controller includes a central processing unit (CPU) or a digital signal processor (DSP), and the system controller provides a program to the digital processor upon power-up.

[0022] An optical communication link can be used between the system controller and the gun controller, through which the system controller provides configuration to the gun controller. This optical communication link may include at least a downlink optical fiber for transmitting data from the system controller to the gun controller and at least an uplink optical fiber for transmitting data from the gun controller to the system controller.

[0023] In the example, the optical communication link encodes the detected voltage of the gun controller into the frequency of optical pulses. Typically, this link includes at least a downlink optical fiber for transmitting data from the system controller to the gun controller and at least an uplink optical fiber for transmitting data from the gun controller to the system controller.

[0024] The gun controller can be or includes a field-programmable gate array (FPGA) or a complex programmable logic device (CPLD), and the system controller provides a configuration file to the digital processor upon power-up. However, the gun controller can also be a central processing unit (CPU) or a digital signal processor (DSP), and the system controller provides a program to the digital processor upon power-up.

[0025] Typically, according to another aspect, the present invention is characterized by an X-ray source comprising a system controller, a target, an electron source for generating electrons to form a beam to strike the target and thereby generate X-rays, a high-voltage generator for accelerating the beam, and a gun controller for controlling the electron source and beamforming under the control of the system controller. The gun controller includes a digital processor and a watchdog timer for resetting the digital processor after a period of inactivity.

[0026] During operation, the watchdog timer receives a keep-alive signal from the system controller and resets the digital processor if the keep-alive signal is not received.

[0027] Typically, according to another aspect, the present invention is characterized by an X-ray source comprising a system controller, a target, an electron source for generating electrons to form a beam that strikes the target to generate X-rays, a high-voltage generator for accelerating the beam, and a gun controller for controlling the electron source. An optical fiber link is used to enable communication between the system controller and the gun controller.

[0028] Typically, according to another aspect, the present invention is characterized by an X-ray source comprising a target, a system controller for monitoring the target current, an electron source for generating electrons to form a beam that strikes the target to generate X-rays, a high-voltage generator for powering the electron source under the control of the system controller, a source coil for manipulating the beam, and a gun controller for controlling the electron source and the source coil and receiving target current information for controlling the source coil.

[0029] Typically, according to another aspect, the present invention is characterized by an X-ray source comprising a target, a system controller for monitoring the target current, an electron source for generating electrons to form a beam that strikes the target to generate X-rays, a high-voltage generator for accelerating the beam, and a gun controller for controlling the electron source, the gun controller including an analog interface unit for digitizing the parameters of the gun controller and generating analog control signals.

[0030] Generally speaking, according to another aspect, the present invention is characterized by a gun controller for controlling the electronic source and monitoring the power supply for the gun controller to control the operation of the power supply.

[0031] Generally speaking, according to another aspect, the present invention is characterized by a gun controller for monitoring the current of an electronic source.

[0032] The above and other features of the invention, including various novel construction details and combinations of components, as well as other advantages, will now be described in more detail with reference to the accompanying drawings, which are pointed out in the claims. It should be understood that the specific methods and apparatus embodying the invention are shown by way of illustration and not by way of limitation. The principles and features of the invention can be used in various and numerous embodiments without departing from the scope of the invention. Attached Figure Description

[0033] In the accompanying drawings, reference numerals refer to the same parts in different views. The drawings are not necessarily drawn to scale; instead, the focus is on illustrating the principles of the invention. In the figures:

[0034] Figure 1 This is a schematic cross-sectional view of the X-ray source according to the present invention;

[0035] Figure 2 This is a schematic diagram illustrating the control of an X-ray source between a system controller and a gun controller based on the principles of this invention.

[0036] Figure 3 It is a swimlane diagram showing the operation of the system digital processor 210 and the gun digital processor 305 during reset, configuration, and operation; and

[0037] Figure 4 This is a simplified block diagram showing the details of the gun controller. Detailed Implementation

[0038] The invention will now be described more fully below with reference to the accompanying drawings, which illustrate illustrative embodiments of the invention. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0039] As used herein, the term “and / or” includes any and all combinations of one or more of the related listed items. Furthermore, all conjunctions used should be understood in the most inclusive sense possible. Thus, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive OR”, unless the context explicitly requires otherwise. Additionally, the singular forms and the articles “a,” “an,” and “the” are also intended to include the plural forms, unless explicitly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including,” and / or “comprising,” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more additional features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, it should be understood that when an element comprising a component or subsystem is mentioned and / or shown as connected or coupled to another element, it may be directly connected or coupled to the other element or there may be intermediate elements present.

[0040] It should be understood that although terms such as "first" and "second" are used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. Therefore, an element discussed below may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the teachings of the invention.

[0041] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense, unless explicitly defined herein.

[0042] Figure 1 This is a schematic cross-sectional view of an X-ray source 100 constructed according to the principles of the present invention.

[0043] The illustrated embodiment is a "transmission target" source. An electron beam B strikes the target of the target assembly 500, and X-rays emitted from the opposite side of the target are used to illuminate the object. That is, many aspects of the following innovations are equally applicable to other X-ray tube source configurations, including side windows, rotating anodes, and metal jet anodes.

[0044] Typically, the X-ray source includes a vacuum container 112 and an oil container 114 disposed within the vacuum container. Preferably, the vacuum container 112 is a metal, such as aluminum or stainless steel, to withstand the strength of the vacuum. The oil container 114 is preferably constructed of a non-conductive material such as ceramic (e.g., sintered alumina) to provide electrical insulation against arcing of the high-voltage components contained within the oil container.

[0045] Vacuum generator 118 is used to evacuate and / or maintain a vacuum on vacuum container 112. In one example, an ion pump is used.

[0046] Arranged inside the oil container is a heat exchanger 119. For this purpose, a plate heat exchanger can be used to transfer heat energy (heat) from the oil to the coolant, such as water circulating in the exchanger. Some embodiments further employ an oil-immersed pump 121 to circulate the oil within the oil container 114. In a preferred embodiment, a circulator 152 is used to allow coolant to flow through the heat exchanger 119 and remove heat from the oil.

[0047] Typically, the vacuum container 112 defines a volumetric evacuation region through which the electron beam B propagates from an electron emitter 126 (filament or cathode) typically located near the distal end of the oil container 114 to a target held by the target assembly 500. The evacuation region also preferably surrounds at least a portion of the oil container containing high-voltage components to provide high-voltage insulation.

[0048] The system controller 200 is located outside the two containers 112 and 114. It includes a main controller and data interfaces to external devices. It also includes a power supply for connecting to the main power supply. In addition, it controls the vacuum generator 118 and the circulator 152.

[0049] A high-voltage generator 116 is located within an oil container 114. The base of the high-voltage generator is located near the end of the oil container 114, allowing the high-voltage generator to receive power from the system controller 200. The high-voltage generator 116 is immersed in the oil contained within the oil container 114 for thermal control and high-voltage insulation. The generator 116 is relatively small and primarily requires oil. However, the generator 116 can also be hermetically sealed. Moving distally, the high-voltage generator 116 is further electrically isolated from the environment by the oil and the vacuum surrounding the vacuum container 112.

[0050] In the current example, the high-voltage generator 116 produces a negative 20-160kV accelerating voltage and powers the gun controller 300, which controls the electronic source (emitter or filament), etc. The high-voltage generator biases the entire gun controller to this large negative voltage so that the generated electrons will be accelerated toward a smaller negative voltage and the ground.

[0051] The inner container 120 is located distal to the high-voltage generator 116. The inner container 120 is immersed in oil in the oil container 114. In the current embodiment, the inner container is preferably made of a metal such as aluminum or soft iron. It is also filled with oil, which helps to transfer heat from the electronic equipment, as well as from the source coil, which will be explained later.

[0052] The gun controller 300 is encapsulated within the inner unit 120, which also serves as a Faraday cage to electrically protect the controller 300. The gun controller 300 drives the electronic transmitter and provides control over the electronic transmitter, beam generation, modulation, and manipulation.

[0053] An electron emitter, such as a filament, 126 is held within a filament base 124. In the current example, the electron emitter 126 comprises a lanthanum hexaboride (LaB6) crystal and a carbon heater rod. It projects electrons into the vacuum of the vacuum container, serving as a thermionic electron source or an electron emitter (cathode). Other configurations are also possible, such as W, CeB6, HfC, and carbon nanotube filaments.

[0054] The vacuum feed device 122 provides an electrical connection between the gun controller 300 in the inner container 120 and the outer wall of the oil container 114 through the oil contained in the oil container 114.

[0055] The suppressor electrode or Wernett cover 127 is mounted to the distal side of the filament base 124 and covers the filament 126. Electrons emitted from the filament 126 pass through the central hole of the suppressor electrode 127. The voltage of the suppressor electrode 127 is controlled by the gun controller 300.

[0056] The protective field cover 138 has a general bell shape, extending above the electron transmitter 126 and its filament holder 124 and surrounding the distal end of the return oil container 114. The distal end of the protective field cover 138 carries the first or extraction anode 140. The voltage of the first anode and the cover is controlled by the gun controller 300 to accelerate the emitted electrons into a beam B and pass through the central hole 141 of the first anode 140. Therefore, in operation, the electron beam passes through the central hole 141 of the first anode 140.

[0057] However, a first anode is not necessary. The system can also be designed without a first anode and rely on other methods to accelerate electrons.

[0058] Beam B is guided through a hole in the flight aperture assembly 142 in the distal wall of the vacuum container 112. This aperture assembly serves as a second anode and is currently held at ground potential 143. Therefore, as the gun controller is biased to a large negative voltage, electrons are further accelerated in the gap between the first anode 140 and the flight aperture assembly 142.

[0059] On the other hand, in other embodiments, the aperture assembly 142 is electrically isolated from the vacuum container 112 by an insulating gasket such as diamond. Furthermore, a voltage generator is added to provide a controlled potential to the flight aperture assembly. In this configuration, the system controller 200 also controls the voltage of the second anode to provide further control over the electron beam B, such as further acceleration. The flight tube assembly 400 extends the vacuum to the target of the target assembly 500. The flight tube manifold 150 provides liquid cooling to the target assembly through the flight tube assembly wall using a coolant such as water from the circulator 152.

[0060] A flight tube beam manipulation and shaping system 600 is arranged along the flight tube assembly 400 to adjust the electronic beam and guide it to any position on the target. This is accomplished by the flight tube assembly 400 and the beam manipulation and shaping system 600, which guides the electronic beam B through the magnetic focusing lens 700 at a desired angle and position. Typically, as the target is consumed during operation, beam manipulation positions the spot at different locations on the target.

[0061] A magnetic focusing lens 700 is further arranged along the flight tube assembly 400 to focus beam B onto the target.

[0062] Preferably, the flight tube beam manipulation and shaping system 600 and the magnetic focusing lens 700 are both cooled by coolant circulated by the circulator 152 and controlled by the system controller 200.

[0063] A set of source coils 132N, 132S (not shown (before and after the image plane): 132E, 132W) and their respective cores 134N, 134S (not shown: 134E and 134W) are integrated with an oil container 114, a gun controller inner container 120, and a protective field cover 138. The coils are located outside the vacuum of the vacuum container. In one example, they may be located on the outer wall of the vacuum container, exposed to the ambient atmosphere. In the example shown, the source coils 132N, 132S, 132E, and 132W are located in the oil container and are therefore effectively cooled by the contained oil, although the coils may alternatively be sealed.

[0064] More generally, oil can be replaced with potting compound or any other high-pressure compatible cooling material, such as Sigma-Aldrich's Fr-77, 3M's Sf6-Novec4710, or C3F7CN.

[0065] More specifically, the two source coils 132N and 132S are typically located above and below the filament 126. Two additional source coils 132E and 132W are located at two other axes, one below and one above the plane of the drawing. The north pole piece 130N and the south pole piece 130S extend from the cores 134N and 134S of the source coils 132N and 132S, respectively, surrounding the inner side of the protective field cover 138, and converging above and below the central hole 141 of the first anode 140. Similarly, the east pole piece 130E and the west pole piece 130W (located at two other axes, one below and one above the plane of the drawing) extend from the cores 134E and 134W of the source coils 132E and 132W, surrounding the inner lateral side of the protective field cover 138, and converging to the left and right sides of the central opening 141, respectively, thus forming a magnetic circuit around the emitter in a vacuum.

[0066] Electrodes 130N, 130S, 130E, and 130W can be mechanically connected to virtually anything in the transmitter region. Therefore, although they are carried by a protective field cover in the illustrated embodiment, they do not need to be directly connected. That is, in the current example, electrodes 130N, 130S, 130E, and 130W are connected to a protective field cover electrically at the potential of the first anode 140.

[0067] An annular yoke 135 is located near the cores 134N, 134S, 134E, and 134W and is fabricated as part of the container 120 to improve the magnetic circuit. In fact, in the current embodiment, the distal end of the inner container 120 is soft iron, thus the magnetic circuit is completed by guiding the magnetic flux between the cores.

[0068] In a preferred embodiment, the magnetic circuitry of the source coils 132N, 132S, 132E, and 132W is further enhanced by magnetizable or ferromagnetic wall-mounted inserts 136N, 136S, 136E, and 136W. These wall-mounted inserts are inserted into holes formed in the oil container 114, which are opposite the distal ends of the respective cores 134N, 134S, 134E, and 134W. This increases the magnetic flux through the circuit. Specifically, the inserts minimize the gaps between the coil cores 134N, 134S, 134E, and 134W and the corresponding pole pieces 130N, 130S, 130E, and 130W.

[0069] Possibly, insert plates 136N, 136S, 136E, and 136W are inserted into holes previously drilled into the ceramic oil container 114. Alternatively, this can be achieved by welding nickel-cobalt-iron alloy or soft iron insert plates to pre-drilled holes in the stainless steel vacuum chamber 112. Other combinations are also possible.

[0070] In the current embodiment, source coils 132N, 132S, 132E, and 132W are driven and operated by gun controller 300 in a current-controlled mode. Feedback is indirectly obtained by system controller 200 measuring the amount of beam reaching the target through the "anode aperture," and this information is provided to the gun controller. The source coils are controlled by gun controller 300 to manipulate the electronic beam near its source, and specifically within the gap between filament 126 and the first anode 140, thereby manipulating the beam during initial acceleration.

[0071] However, it should be noted that in other embodiments, the high-pressure generator may be a separate component outside the vacuum container.

[0072] Figure 2 The diagram illustrates how the control of the X-ray source 100 is distributed between the system controller 200 and the gun controller 300, and their communication, according to the principles of the invention.

[0073] The system controller 200 has a system digital processor 210 that serves as the main controller for the X-ray source 100. Typically, this is a central processing unit that receives user commands from the host computer via a digital interface such as an Ethernet (IEEE 802.3) interface. The system digital processor 210 uses system memory 212. This system memory stores the configuration of the system digital processor, i.e., the program, as well as the gun processor configuration 214. It also typically stores system calibration data 215.

[0074] The gun processor 305 can take several different forms. If the gun processor 305 is a CPU, DSP, or other type of microcontroller, the gun processor configuration 214 stored in system memory 212 is a program that includes a bootloader for the gun digital processor 305. On the other hand, if the gun digital processor 305 is an FPGA or CPLD, then the gun processor configuration 214 is typically referred to as a configuration file. In any case, the configuration of the gun digital processor 305 is stored in an environment free from any radiation generated by the X-ray source 100. Another reason for sending the configuration to the gun controller each time is on-demand configuration, eliminating the need to reprogram the flash memory within the gun controller. However, the processor 305 typically also includes memory 306. In some examples, radiation shielding is added to protect this memory 306.

[0075] In addition, the system controller 200 includes numerous other drivers and monitoring devices for operating the source 100. Specifically, it includes a target current receiver 220 that detects the target current from the target assembly 500. It also includes a magnetic lens driver 222, which enables the system digital processor 210 to control the operation of the magnetic focusing lens 700. Furthermore, a beam manipulation and shaping system driver 224 enables the system digital processor 210 to control the beam manipulation and shaping system 600. A vacuum driver 232 allows the system digital processor to supply power to a vacuum generator, such as an ion pump 116, to maintain a vacuum. It also receives analog feedback from the vacuum pump.

[0076] The system digital processor 210 controls the high-voltage generator 116 via the high-voltage generator driver 226. It also includes a power supply 228.

[0077] In the high-voltage generator 216, the high-voltage multiplier 170 is used to generate the high voltage supplied to the gun controller 300. Furthermore, the isolation transformer 172 supplies power received from the power supply 228 to the gun controller 300. This transformer isolates the power supply 228 of the system controller 200 from the high potential at which the gun controller 300 operates.

[0078] In some examples, the isolation transformer 172 is not used. Instead, power is derived from the high-voltage power supplied by the high-voltage multiplier. However, the advantage of a separate isolation transformer 172 is that the gun controller 300 can be powered on along with its gun digital processor 305 without the high-voltage output of the high-voltage multiplier.

[0079] On the electron gun controller 300, the electron gun digital processor 305 controls components related to electron beamforming. Specifically, the filament heater and driver 312 provide power to heat the filament 126. The filament U / I sensing module 314 monitors the operation of the filament 126 and provides feedback to the gun digital processor 305.

[0080] Suppressor voltage controller 316 controls the potential of suppressor electrode 127. First anode voltage controller 318 allows digital processor 305 to adjust the voltage of first anode 140. Gun digital processor 305 controls the manipulation of the electronic beam by controlling source coil drivers 310 of source coils 132N, 132S, 132E, and 132W.

[0081] A bidirectional fiber optic link 180 provides communication between the system digital processor 210 of the system controller 200 and the gun digital processor 305 of the gun controller 300. The fiber optic link is maintained between the system controller optoelectronic interface 230 and the gun controller optoelectronic interface 320. Typically, the fiber optic link includes one or more optical fibers, usually two or more. Preferably, these are multimode fibers, but single-mode fibers can also be used. On the other hand, each optoelectronic interface 230, 330 includes a transmitter comprising a diode laser that optically encodes information for transmission over the fiber optic cable. Furthermore, each optoelectronic interface 230, 330 includes a receiver, typically a photodiode, that detects modulated light from another laser diode to decode the light into electronic signals for use by the system digital processor 210 and the gun digital processor 305.

[0082] During operation, the gun digital processor 305 reports the operation of the filament 126, suppressor electrode 127, first anode 140, and transmitter control coil 132 to the system digital processor via optical link 180. Typically, the gun digital processor 305 transmits status data (overcurrent, system health), temperature, supply voltage, and supply current. On the other hand, the system digital processor 210 transmits the following information to the gun digital processor: interlock status (for emergency beam shutdown), software monitoring signals, enable data for all subsystems, and all requested voltages and currents (Wehnelt, first anode 140, filament, source coil).

[0083] During startup, the gun digital processor 305 receives power from the system controller via isolation transformer 172 and immediately begins searching for the configuration received via fiber optic link 180 through optoelectronic interface 320. As a result, during startup, system digital processor 210 reads gun processor configuration 214 and forwards it to optoelectronic interface 230 for transmission to gun digital processor 305 via fiber optic link 182. Gun processor configuration 214 is stored in its system memory 212. In the current example, gun digital processor 305 is an FPGA and is programmed to be "serial slave," receiving an asynchronous clock configuration bitstream upon reset.

[0084] The gun controller also includes a monitor 322. It monitors communication on the fiber optic link to receive periodic keep-alive clock signals sent by the system controller 200. If the monitor 322 fails to detect the clock after a set timeout period (e.g., less than 5 milliseconds), the monitor 322 resets the gun's digital processor.

[0085] During reset, the output pins of the gun digital processor 305 have a specified state. FPGAs typically pull all pins high during reset. The gun control electronics are implemented by shutting down the electronic beam, filament heater, and control coil during reset.

[0086] The gun digital processor 305 controls the source coils 132N, 132S, 132E, and 132W. More specifically, in the current embodiment, the system digital processor 210 monitors the target current via the target current receiver 220. This target current information is used to determine the drive current to each of the source coils 132N, 132S, 132E, and 132W. These desired drive currents are then relayed to the gun digital processor 305 via fiber optic link 180. The gun digital processor uses these current settings to control the source coils 132N, 132S, 132E, and 132W to manipulate the beam through the aperture to reach the target during operation.

[0087] However, in other embodiments, the target current information is sent to the gun digital processor, which then determines the drive current for the different coils.

[0088] Figure 3 The communication between the system digital processor 210 and the gun digital processor 305 is shown.

[0089] More specifically, during the reset, the system digital processor 210 does not send communication to the gun digital processor 305 via fiber optic link 180, which in this example includes two optical fibers F1 and F2. As a result, in step 610, a predetermined timeout period, such as one second, is waited for, and then in step 612, the gun digital processor 305 performs a self-reset, awaiting configuration.

[0090] During configuration, the first fiber F1 transmits a clock signal and the second fiber F2 transmits a bit stream encoding the gun configuration 214 of the gun digital processor 305. During this communication, the gun digital processor 305 receives its configuration in step 614 and then executes the configuration.

[0091] During connection and normal operation, optical fibers F1 and F2 send data streams to the gun digital processor 305, and the third optical fiber F3 transmits the data stream from the gun digital processor 305 to the system digital processor 210 according to the operation provided by the gun configuration 214.

[0092] In other examples, only one optical fiber is used. Instead of F1 (clock) and F2 (data), only F1 has a predetermined bit rate and protocol, such as standard RS232 or RS485 communication.

[0093] Then, in the subsequent reset phase, if no signal is received from the system digital processor after timeout 616, the gun digital processor 305 undergoes another self-reset in step 618, waiting for configuration.

[0094] Figure 4 This is a schematic block diagram showing the details of the gun controller.

[0095] In the example shown, the bidirectional fiber optic link 180 includes three fibers F1, F2, and F3. They terminate at the optical / electrical module 320. In this example, the system functions similarly to direct memory access, where data from the fibers is written directly to memory 306. Simultaneously, the contents of the memory are sent from the digital processor 305 to the system controller 200.

[0096] The gun power supply 340 receives 20 volts of AC power from the isolation transformer 172. It then generates 12 volts and 3.3 volts of DC power for the operation of the gun controller 300.

[0097] The analog interface unit 342 serves as an interface between the gun digital processor 305 and the analog components, which include a source coil driver array 310, a filament heater / driver 312, a filament sensing unit 314, a first anode voltage controller 318, and a suppressor voltage controller 316. Specifically, for this operation, the analog interface 342 includes stages of several analog-to-digital converters 344 and stages of several digital-to-analog converters 346.

[0098] The source coil driver array 310 includes a north coil driver 348 for driving the north coil 132N, a south coil driver 350 for driving the south coil 132S, an east coil driver 352 for driving the east coil 132E, and a west coil driver 354 for driving the west coil 132W. Each of these coil drivers 348-354 receives a separate current selection signal from the digital-to-analog converter stage 346. These selection signals are used to set the current level of the corresponding driver / coil pair.

[0099] The filament heater / driver 132 includes a DC-DC converter 356. It receives 12VDC from the gun power supply 340. A voltage selection signal provided by the digital-to-analog stage 346 sets the voltage generated by the DC-DC converter 356, thereby controlling the drive current to the filament 126.

[0100] The filament U / I sensing unit 314 includes a current sensor 358 and a voltage sensor 360. These generate current and voltage sensing signals digitized by the analog-to-digital converter stage 344, allowing the current and voltage of the filament 126 (generated by the DC-DC converter 356) to be monitored by the gun digital processor 305. Furthermore, the processor 305 can now monitor the power dissipated in the filament and use this information to indirectly estimate the filament temperature.

[0101] In one example, the gun's digital processor monitors the voltage across filament 126 and the current through filament 126, especially over time. Based on this information, the resistance of filament 126 is monitored, particularly how that resistance changes over time, to assess the wear and current condition of filament 126. In many examples, this information is further used to optimize filament control to improve its long-term operation and lifespan. This is particularly useful when using tungsten filaments.

[0102] The first anode voltage controller 318 includes a DC-DC converter 362. A voltage selection signal from the analog-to-digital converter stage 346 allows the gun digital processor 305 to set the voltage applied to the first anode 140. A voltage sensing signal allows the gun digital processor 305 to monitor the actual voltage of the first anode 140 via the analog-to-digital converter stage 344.

[0103] The suppressor voltage controller 316 also includes a DC-DC converter 364 that generates a voltage applied to the suppressor electrode 127. The voltage sensing signal allows the gun digital processor 305 to monitor the actual voltage of the suppressor 127 via the analog-to-digital converter stage 344.

[0104] The gun controller 300 also reads the voltage supplied by the output of the isolation transformer 172 and provides feedback control to the power supply 228 of the system controller 200 to regulate the voltage to the nominal 20VAC. This supply voltage varies with the load in the gun controller (by changing the coil current and heating the filament with different power). The analog interface 342 samples the voltage from the isolation transformer 172 and reports the digitized voltage to the gun digital processor 305, which sends the voltage reading back to the system controller 200. The system controller 200 sequentially adjusts the power output from the power supply 228 to the isolation transformer 172 until feedback from the gun controller 300 indicates that the gun controller's power supply is at the desired voltage.

[0105] In the current embodiment, power supply 228 performs pulse width modulation on the isolation transformer. The "on time" during which power is delivered varies according to the power demand from the gun controller 300. More specifically, power supply 228 turns on the positive phase AC power supply for duration t1 and turns it off for duration t2, turns on the negative phase AC power supply for duration t1 and turns it off for duration t2. The power supply controls the ratio of t1 / (t1+t2) to achieve the desired output power and voltage, and controls (t1+t2) to achieve the desired switching frequency. At the same switching frequency, as t1 increases, t2 decreases by the same amount.

[0106] Although the invention has been specifically shown and described with reference to its preferred embodiments, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the scope of the invention as covered by the appended claims.

[0107] Cross-reference to related applications

[0108] This application relates to U.S. application number filed on the same day. 17 / 238,785 The patent application, entitled "X-ray Source with Liquid-Cooled Source Coil," was invented by Claus Flachenecker and Thomas A. Case, with attorney number 0002.0085US1(2020ID00440), and is currently published in the United States Patent Publication No.: ______.

[0109] The U.S. application number filed on the same day is 17 / 238,799 The application, entitled "Method and System for Liquid Cooling and Isolating X-ray Transmission Targets," was invented by Claus Flachenecker, Bruce Borchers, and Thomas A. Case, with agent number 0002.0086US1(2020ID00442), and is currently under US Patent Publication No.: ______.

[0110] All of the above applications are incorporated herein by reference in their entirety.

Claims

1. An X-ray source, comprising: The system controller includes system memory that stores the gun processor configuration and the system digital processor; target; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller for controlling the electronic source and receiving the gun processor configuration from the system controller at each startup, the gun controller including a gun digital processor, the system digital processor reading the gun processor configuration from the system memory and providing the gun processor configuration to the gun digital processor; as well as An optical communication link exists between the system controller and the gun controller, through which the system controller provides the gun processor configuration to the gun controller.

2. The source according to claim 1, further comprising a source coil controlled by the gun controller.

3. The source according to claim 1, wherein, The gun controller includes a field-programmable gate array (FPGA) that serves as the gun's digital processor, and the system controller provides the gun's digital processor with a configuration file corresponding to the gun processor's configuration after power-on.

4. The source according to claim 1, wherein, The gun controller includes a central processing unit (CPU) or a digital signal processor (DSP) that serves as the gun's digital processor, and the system controller provides the gun's digital processor with a program corresponding to the gun processor's configuration after power-on.

5. The source according to claim 1, wherein, The optical communication link between the system controller and the gun controller includes at least a downlink optical fiber for transmitting data from the system controller to the gun controller and at least an uplink optical fiber for transmitting data from the gun controller to the system controller.

6. An X-ray source, comprising: The system controller includes system memory that stores the gun processor configuration and the system digital processor; target; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller, which controls the electronic source and the beam formation under the control of the system controller, the gun controller includes a gun digital processor and a watchdog timer for resetting the gun digital processor after a period of no response, the system digital processor reads the gun processor configuration from the system memory and provides the gun processor configuration to the gun digital processor; as well as An optical communication link exists between the system controller and the gun controller, through which the system controller provides the gun processor configuration to the gun controller.

7. The source according to claim 6, wherein, The watchdog timer receives a keep-alive signal from the system controller and resets the gun digital processor if the keep-alive signal is not received.

8. The source of claim 6, wherein the optical communication link between the system controller and the gun controller comprises at least a downlink optical fiber for transmitting data from the system controller to the gun controller and at least an uplink optical fiber for transmitting data from the gun controller to the system controller.

9. An X-ray source, comprising: The system controller includes system memory that stores the gun processor configuration and the system digital processor; target; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller for controlling the electronic source and receiving the gun processor configuration from the system controller upon each startup, the gun controller including a gun digital processor, the system digital processor reading the gun processor configuration from the system memory and providing the gun processor configuration to the gun digital processor; and An optical fiber link is used to enable communication between the system controller and the gun controller.

10. The source according to claim 9, wherein, The gun digital processor is a field-programmable gate array (FPGA), and the system controller provides the gun digital processor with a configuration file corresponding to the gun digital processor configuration upon power-up.

11. The source according to claim 9, wherein, The gun digital processor is a central processing unit (CPU) or a digital signal processor (DSP), and the system controller uses the fiber optic link to provide the gun digital processor with a program corresponding to the gun digital processor configuration.

12. The source according to claim 9, wherein, The fiber optic link between the system controller and the gun controller includes at least a downlink fiber for transmitting data from the system controller to the gun controller and at least an uplink fiber for transmitting data from the gun controller to the system controller.

13. An X-ray source, comprising: target; A system controller for monitoring the target current of the target, the system controller including a system memory for storing gun processor configuration and a system digital processor; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator, used to supply power to the electronic source under the control of the system controller; A source coil, used to manipulate the beam; A gun controller is used to control the electronic source and the source coil, and to receive target current information for controlling the source coil. The gun controller includes a gun digital processor, which receives a gun processor configuration from the system controller each time it is started. The system digital processor reads the gun processor configuration from the system memory and provides the gun processor configuration to the gun digital processor. as well as A fiber optic link is used to enable communication between the system controller and the gun controller and to transmit the gun processor configuration.

14. The source according to claim 13, wherein, The system controller forwards the target current information to the gun controller via the fiber optic link.

15. An X-ray source, comprising: The system controller includes system memory that stores the gun processor configuration and the system digital processor; target; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller for controlling the electronic source includes an analog interface unit for digitizing the parameters of the gun controller and generating analog control signals. The gun controller includes a gun digital processor. The system digital processor reads the gun processor configuration from the system memory and provides the gun processor configuration to the gun digital processor. as well as An optical communication link exists between the system controller and the gun controller, through which the system controller provides the gun processor configuration to the gun controller.

16. An X-ray source, comprising: target; A system controller for monitoring the target current of the target, the system controller including a system memory for storing gun processor configuration and a system digital processor; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller for controlling the electronic source and monitoring the power supply for the gun controller in order to control the operation of the power supply, the gun controller including a gun digital processor, the system digital processor reading the gun processor configuration from the system memory and providing the gun processor configuration to the gun digital processor; as well as An optical communication link exists between the system controller and the gun controller, through which the system controller provides the gun processor configuration to the gun controller.

17. An X-ray source, comprising: target; A system controller for monitoring the target current of the target, the system controller including a system memory for storing gun processor configuration and a system digital processor; An electron source, used to generate electrons to form a beam that strikes the target to produce X-rays; A high-voltage generator is used to accelerate the beam; A gun controller is used to monitor the current of the electronic source and receive the gun processor configuration from the system controller each time it is started. The gun controller includes a gun digital processor, which reads the gun processor configuration from the system memory and provides the gun processor configuration to the gun digital processor. as well as An optical communication link exists between the system controller and the gun controller, through which the system controller provides the gun processor configuration to the gun controller.

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