Field emission electron gun driving circuit

Abstract

The invention discloses a field emission electron gun driving circuit which comprises an FEG data transmission module, an extraction electrode voltage module, a cathode heating current module, a suppression electrode voltage module, an ion pump power supply module and an analog quantity detection module. The FEG data transmission module is used for converting a digital control signal sent by the upper computer through the IC bus into an analog signal, transmitting the analog signal to other modules in the driving circuit, receiving an analog quantity detection signal of the analog quantity detection module, converting the analog quantity detection signal into a digital quantity, and transmitting the digital quantity back to the upper computer through the IC bus; the ion pump power module is used for providing working power for the ion pump; the cathode heating current module is used for generating constant current to heat a cathode filament; the suppression electrode voltage module is used for generating suppression electrode voltage; the leading-out electrode voltage module is used for generating leading-out electrode voltage; the analog quantity detection module is used for detecting analog quantity signals of all the modules and transmitting the analog quantity signals to the FEG data transmission module. The method has the advantages of good stability, high reliability and the like.

Description

Technical Field

[0001] This invention relates to the field of electron beam technology, specifically to a field emission electron gun driving circuit. Background Technology

[0002] Transmission electron microscopy (TEM) is a high-resolution microscope that uses an electron beam with an extremely short wavelength to penetrate a sample and achieve multi-stage magnification imaging through electromagnetic lenses. The electron beam is generated by an electron gun; a field emission electron gun (FEG) is one type of electron gun. In an ultra-high vacuum environment, an applied strong electric field emits electrons from the tip of a metal cathode through which a constant heating current flows. After passing through a suppressor electrode, the electrons are accelerated by a high voltage to form a high-energy electron beam, which serves as the illumination source for the TEM. The performance of the FEG directly determines the imaging quality and maximum resolution of the TEM. The drive circuit system of the field emission electron gun is the core guarantee of its performance. It is responsible for driving the stable extraction and emission of the electron beam from the cathode tip and maintaining the ultra-high vacuum environment for electron beam emission. Therefore, designing a structurally optimized FEG drive circuit system with ultra-high stability, extremely low noise, fast response capability, and reliable durability is crucial for TEM equipment. Summary of the Invention

[0003] To address the technical problems existing in the prior art, the present invention provides a field emission electron gun driving circuit with good stability and high reliability.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A field emission electron gun driving circuit includes an FEG data transmission module, a lead-out electrode voltage module, a cathode heating current module, a suppressor electrode voltage module, an ion pump power supply module, and an analog quantity detection module. The FEG data transmission module is used to convert the digital control signals sent by the host computer through the I²C bus into analog signals and transmit them to other modules in the drive circuit. At the same time, it receives the analog detection signals from the analog quantity detection module, converts them into digital quantities, and transmits them back to the host computer through the I²C bus. The ion pump power supply module is connected to the FEG data transmission module and is used to provide working power to the ion pump according to the switching signal of the FEG data transmission module. The cathode heating current module is connected to the FEG data transmission module and is used to generate a constant current to heat the cathode filament according to the switching signal and drive signal of the FEG data transmission module. The suppression voltage module is connected to the FEG data transmission module and is used to generate a suppression voltage according to the switching signal and drive signal of the FEG data transmission module. The lead-out voltage module is connected to the FEG data transmission module and is used to generate lead-out voltage according to the switching signal and drive signal of the FEG data transmission module. The input terminal of the analog signal detection module is connected to the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module, and the output terminal is connected to the FEG data transmission module. The analog signal detection module is used to detect the analog signals of the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module and transmit them to the FEG data transmission module.

[0005] Preferably, the FEG data transmission module adopts a two-wire to three-wire I²C bus design, converting the half-duplex two-wire I²C bus protocol into a full-duplex three-wire I²C bus, with the three wires including SCL, SDA-IN, and SDA-OUT.

[0006] Preferably, the two-wire to three-wire I²C bus design is implemented by combining NAND gate chips.

[0007] Preferably, the FEG data transmission module includes an ADC chip and a DAC chip, used to realize the mutual conversion between digital signals and analog signals.

[0008] Preferably, the ion pump power supply module includes a switching power supply control chip, used to control the switching on and off of the ion pump power supply module according to the switching level signal of the FEG data transmission module, and output a voltage at the kilovolt level.

[0009] Preferably, the analog signal detection module includes an analog signal multiplexer for transmitting multiple analog signals.

[0010] Preferably, the analog signals detected by the analog quantity detection module include the ion pump current measurement value and ion pump overvoltage monitoring voltage measurement value of the ion pump power supply module, the cathode filament current measurement value and electron beam emission current measurement value of the cathode heating current module, the suppression electrode voltage measurement value of the suppression electrode module, and the lead-out electrode voltage measurement value of the lead-out electrode module.

[0011] Compared with the prior art, the advantages of the present invention are as follows: This invention integrates six functional modules—FEG data transmission, ion pump power supply, cathode heating, suppressor voltage, lead-out voltage, and analog quantity detection—through a modular design. It innovatively employs a two-wire to three-wire I²C bus to achieve full-duplex communication, significantly improving system response speed and real-time data transmission. Each power supply module achieves high stability and low noise in high-voltage output through digital control and analog feedback closed-loop, ensuring the brightness and purity of the electron beam emission. Simultaneously, comprehensive status monitoring and remote control capabilities effectively guarantee the long-term reliable operation of the field emission electron gun in an ultra-high vacuum environment, thereby comprehensively improving the imaging quality and durability of the transmission electron microscope. Attached Figure Description

[0012] Figure 1 This is a structural diagram of the field emission electron gun driving circuit of the present invention in an embodiment. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0014] like Figure 1 As shown, the field emission electron gun driving circuit provided in this embodiment of the invention includes an FEG data transmission module, a lead-out electrode voltage module, a cathode heating current module, a suppressor electrode voltage module, an ion pump power supply module, and an analog quantity detection module. The FEG data transmission module is used to convert digital control signals sent by the host computer via the I²C bus into analog signals and transmit them to other modules in the drive circuit. At the same time, it receives analog detection signals from the analog quantity detection module, converts them into digital quantities, and transmits them back to the host computer via the I²C bus. The ion pump power supply module is connected to the FEG data transmission module and is used to provide working power to the ion pump and maintain the ultra-high vacuum environment of the electron gun by selecting and turning it on and off according to the switching signal of the FEG data transmission module. The cathode heating current module (constant current source) is connected to the FEG data transmission module and is used to generate a constant current to heat the cathode filament according to the switching signal and drive signal of the FEG data transmission module. The suppressor voltage module is connected to the FEG data transmission module and is used to generate the suppressor voltage according to the switching signal and drive signal of the FEG data transmission module. The lead-out voltage module is connected to the FEG data transmission module and is used to generate the lead-out voltage according to the switching signal and drive signal of the FEG data transmission module. The input terminal of the analog signal detection module is connected to the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module, and the output terminal is connected to the FEG data transmission module. The analog signal detection module is used to detect the analog signals of the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module and transmit them to the FEG data transmission module.

[0015] Specifically, the control signals transmitted from the FEG data transmission module to the host computer of the drive circuit system mainly include the ion pump power module switch signal, the cathode heating current module turn-on signal and drive signal, the suppressor voltage module turn-on signal and drive signal, and the lead-out voltage module turn-on signal and drive signal; the analog detection values ​​transmitted from the FEG data transmission module to the host computer mainly include the ion pump overvoltage monitoring voltage measurement value, the ion pump current measurement value, the cathode filament current measurement value, the electron beam emission current measurement value, the suppressor voltage measurement value, and the lead-out voltage measurement value.

[0016] To achieve simultaneous transmission of signals sent from the host computer and signals returned from analog signal detection, this invention innovatively introduces a two-wire to three-wire I²C bus design. By using NAND gate chips for logic combination, the traditional half-duplex two-wire I²C bus protocol is converted into a full-duplex three-wire I²C bus. Specifically, the I²C bus is transformed from a two-wire combination of SCL and SDA to a three-wire combination of SCL, SDA-IN, and SDA-OUT.

[0017] The internal digital-to-analog signal conversion within the FEG data transmission module is achieved through ADC and DAC chips. Switching signals from each module are converted to high and low levels after transmission via the I²C protocol and then transmitted to the switching level input terminals of each module through the I / O ports. Drive signals from each module are converted to analog quantities by the DAC chip, processed again by the operational amplifier circuit, and finally transmitted to the drive input terminals of each module. Analog detection signals from each module are sampled and held, converted to digital quantities by the ADC chip, and finally transmitted back to the host computer via the I²C bus.

[0018] Specifically, an ultra-high vacuum environment is a necessary condition for the electron gun to emit electron beams; the FEG requires a vacuum environment of 10... -8 The ion pump power module provides power for the normal operation of the ion pump. Its output voltage is in the kilovolt range and is adjusted according to the ion pump model. Once the ion pump model is selected, the output voltage becomes a fixed value.

[0019] The ion pump power module selects and turns off based on the switching level signal transmitted by the FEG data transmission module, using a switching power supply control chip as the actuator for module selection and shutdown. The switching level signal transmitted by the FEG data transmission module, after passing through a series of intermediate circuits, controls the switching power supply control chip's selection and shutdown, which in turn controls the on / off state of the ion pump power module's power supply circuit. When the ion pump power module's power supply circuit is on, the boost module starts working, generating a kilovolt-level voltage to maintain the normal operation of the ion pump. Simultaneously, the module transmits the analog signals of the ion pump overvoltage monitoring voltage and ion pump current to the analog quantity detection module. In the analog quantity detection module, these signals are processed by a detection circuit and then transmitted via the FEG data transmission module to the host computer software for final measurement.

[0020] Specifically, the cathode heating current module generates a constant current that flows through the FEG cathode filament, heating the tip of the cathode filament through the Joule effect, which promotes thermal excitation of electrons and enhances stable emission under the action of the lead-out electrode electric field, thereby generating a high-brightness, low-noise electron beam.

[0021] The output current of the cathode heating current module can be set via host computer software. The module is selected by a switching level signal transmitted from the FEG data transmission module. Simultaneously, the module drive signal transmitted from the FEG data transmission module drives the current source circuit to generate a constant current, with a maximum output current of 2.8A within a safe range. The cathode heating current module transmits analog signals of the cathode filament current and electron beam emission current to the analog quantity detection module. In the analog quantity detection module, the signals are processed by a detection circuit and then transmitted via the FEG data transmission module to the host computer software for processing, yielding the final measurement results of the cathode filament current and electron beam emission current.

[0022] Specifically, the suppressor voltage module provides a stable voltage to the suppressor of the FEG, forming an antiphase electric field with the cathode to precisely control the emission intensity and initial focusing of the electron beam, ensuring that the electron beam is emitted stably and controllably.

[0023] The suppressor voltage module is selected by the switching level signal transmitted by the FEG data transmission module. After the module is selected, the module drive signal transmitted by the FEG data transmission module passes through the operational amplifier circuit in the module to generate the drive voltage of the transformer circuit in the module. The transformer circuit boosts the drive voltage to generate a negative high voltage of -2.2kV and outputs it to the FEG suppressor.

[0024] In the suppressor voltage module, an initial detection analog signal for the module's output voltage is obtained by cascading resistors in series. This signal is then transmitted to the analog quantity detection module for processing by the detection circuit within the module. Finally, the signal is transmitted to the host computer software via the FEG data transmission module for further processing, resulting in the final measurement result of the suppressor voltage module's output voltage.

[0025] Specifically, the output voltage of the lead-out voltage module provides a stable voltage to the lead-out electrode of the FEG, allowing electrons to escape from the tip of the cathode filament.

[0026] The lead-out voltage module is selected by the switching level signal transmitted from the FEG data transmission module. After selection, the module drive signal transmitted from the FEG data transmission module is converted into the input voltage of the subsequent amplifier circuit in the lead-out voltage module through the operational amplifier circuit. The subsequent amplifier circuit amplifies the voltage a second time, up to a maximum of 8kV. In the lead-out voltage module, the voltage signal before amplification by 1000 times is used as the lead-out voltage detection object. The module transmits the detected analog voltage signal to the analog quantity detection module, and finally, after being transmitted to the host computer software via the FEG data transmission module, it is multiplied by 1000 and processed to obtain the final output voltage measurement value of the lead-out voltage module.

[0027] Specifically, the analog quantity detection module is the core module for all analog quantities in the drive circuit. The detected values ​​of each analog quantity are fed back to the host computer software for processing and display, allowing users to observe them. The analog signals detected by the analog quantity detection module mainly include the ion pump current measurement value and ion pump overvoltage monitoring voltage measurement value from the ion pump power supply module, the cathode filament current measurement value and electron beam emission current measurement value from the cathode heating current module, the suppressor voltage measurement value from the suppressor voltage module, and the lead-out voltage measurement value from the lead-out voltage module.

[0028] The analog signal detection module includes an analog multiplexer channel for transmitting the detected analog signals. After the initial analog measurement signals are transmitted to the module, they are processed by different detection circuits based on the characteristics of each analog signal to obtain the measured analog signal, which is then transmitted to the internal analog multiplexer. The analog multiplexer can only process one analog signal at a time, transmitting it to the sampling and holding terminals of the FEG data transmission module, where it is converted from analog to digital.

[0029] This invention integrates six functional modules—FEG data transmission, ion pump power supply, cathode heating, suppressor voltage, lead-out voltage, and analog quantity detection—through a modular design. It innovatively employs a two-wire to three-wire I²C bus to achieve full-duplex communication, significantly improving system response speed and real-time data transmission. Each power supply module achieves high stability and low noise in high-voltage output through digital control and analog feedback closed-loop, ensuring the brightness and purity of the electron beam emission. Simultaneously, comprehensive status monitoring and remote control capabilities effectively guarantee the long-term reliable operation of the field emission electron gun in an ultra-high vacuum environment, thereby comprehensively improving the imaging quality and durability of the transmission electron microscope.

[0030] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A field emission electron gun driving circuit, characterized in that, It includes a FEG data transmission module, a lead-out electrode voltage module, a cathode heating current module, a suppressor electrode voltage module, an ion pump power supply module, and an analog quantity detection module; The FEG data transmission module is used to convert the digital control signals sent by the host computer through the I²C bus into analog signals and transmit them to other modules in the drive circuit. At the same time, it receives the analog detection signals from the analog quantity detection module, converts them into digital quantities, and transmits them back to the host computer through the I²C bus. The ion pump power supply module is connected to the FEG data transmission module and is used to provide working power to the ion pump according to the switching signal of the FEG data transmission module. The cathode heating current module is connected to the FEG data transmission module and is used to generate a constant current to heat the cathode filament according to the switching signal and drive signal of the FEG data transmission module. The suppression voltage module is connected to the FEG data transmission module and is used to generate a suppression voltage according to the switching signal and drive signal of the FEG data transmission module. The lead-out voltage module is connected to the FEG data transmission module and is used to generate lead-out voltage according to the switching signal and drive signal of the FEG data transmission module. The input terminal of the analog signal detection module is connected to the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module, and the output terminal is connected to the FEG data transmission module. The analog signal detection module is used to detect the analog signals of the ion pump power supply module, the cathode heating current module, the suppressor voltage module, and the lead-out voltage module and transmit them to the FEG data transmission module.

2. The field emission electron gun driving circuit according to claim 1, characterized in that, The FEG data transmission module adopts a two-wire to three-wire I²C bus design, which converts the half-duplex two-wire I²C bus protocol into a full-duplex three-wire I²C bus. The three wires include SCL, SDA-IN and SDA-OUT.

3. The field emission electron gun driving circuit according to claim 2, characterized in that, The two-wire to three-wire I²C bus design is implemented through logic combination using NAND gate chips.

4. The field emission electron gun driving circuit according to claim 1, 2, or 3, characterized in that, The FEG data transmission module includes an ADC chip and a DAC chip, which are used to convert between digital signals and analog signals.

5. The field emission electron gun driving circuit according to claim 1, 2, or 3, characterized in that, The ion pump power supply module includes a switching power supply control chip, which controls the switching on and off of the ion pump power supply module according to the switching level signal of the FEG data transmission module, and outputs a voltage at the kilovolt level.

6. The field emission electron gun driving circuit according to claim 1, 2, or 3, characterized in that, The analog signal detection module includes an analog multiplexer for transmitting multiple analog signals.

7. The field emission electron gun driving circuit according to claim 1, 2, or 3, characterized in that, The analog signals detected by the analog quantity detection module include the ion pump current measurement value and ion pump overvoltage monitoring voltage measurement value of the ion pump power supply module, the cathode filament current measurement value and electron beam emission current measurement value of the cathode heating current module, the suppression electrode voltage measurement value of the suppression electrode module, and the lead-out electrode voltage measurement value of the lead-out electrode module.

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