A method and system for pulsing a particle beam current

Abstract

The present invention discloses a method and a system for pulsing a particle beam. The method includes: Step 1, sending the beam cutting signal that has been received, amplified, and shaped into a pulse signal to a frequency divider, and forming square wave pulse signals with different frequencies in the frequency divider; Step 2, the square wave pulse signal forms two separate pulses, namely a pulse on signal and a pulse off signal. The time interval between the two pulse signals is the pulse width, and the pulse width is continuously adjustable. Then, the two signals are respectively sent to two pulse delay circuits as delay start pulses; Step 3, based on the pulse sequence generated by the pulse delay circuit, generating a narrow pulse of 70V@20ns and driving the pulse transformer in the pulse power amplifier; Step 4, the pulse transformer generates high-frequency high-voltage pulses of ±450V and sends them to the deflection plates, where a ±450V DC power supply is output to the pulse amplifier.

Description

Technical Field

[0001] The present invention relates to the field of accelerators, and specifically to a method and system for pulsing a particle beam; Background Art

[0002] A particle beam refers to a flowing collection composed of a large number of particles. These particles have similar properties and motion states, and are gathered together in space with high speed and high current density. The particle beam can include different types of particles such as electron beams, ion beams, and neutron beams.

[0003] The formation of a particle beam can be achieved through different methods. One common method is to use a particle accelerator. A particle accelerator can accelerate charged particles (such as electrons or ions) to high energies and focus them into a beam. This can be achieved through an electric field, a magnetic field, or a combination of both. The focusing system can make the particle beam gather and maintain its relatively narrow diameter for experiments, applications, or further processing.

[0004] However, currently, there is no efficient and stable way proposed for converting a continuous beam into a pulsed beam. Summary of the Invention

[0005] Object of the Invention: To provide a method and system for pulsing a particle beam, which is used to pulse a continuous particle beam of low-energy particles. The role of the cutter is to cut the beam into a form of pulse train for output, so as to solve the above problems existing in the prior art.

[0006] Technical Solution: A method for pulsing a particle beam includes:

[0007] Step 1: Send the beam-cutting signal that has been received, amplified, and shaped into a pulse signal to a frequency divider, and form square-wave pulse signals of different frequencies in the frequency divider;

[0008] Step 2: The square-wave pulse signal forms two separate pulses, namely a pulse-on signal and a pulse-off signal. The time interval between the two pulse signals is the pulse width, and the pulse width is continuously adjustable. Then send the two signals to two pulse delay circuits respectively as delay start pulses;

[0009] Step 3: Based on the pulse sequence generated by the pulse delay circuit, generate a narrow pulse of 70V@20ns and drive the pulse transformer in the pulse power amplifier;

[0010] Step 4: The pulse transformer generates high-frequency high-voltage pulses of ±450V and sends them to the deflection plates. Among them, a ±450V DC power supply outputs to the pulse amplifier, so as to obtain the required waveform on the load and provide it to the deflection plates. At this time, the beam generated by the ion source is deflected, and the continuous beam is cut into a pulsed beam.

[0011] In a further embodiment, the pulse delay circuit includes a coarse delay unit and a fine delay unit;

[0012] When the delay parameter is greater than 5 ns, the coarse delay unit is adopted;

[0013] When the delay parameter is less than 5 ns, the fine delay unit is adopted.

[0014] In a further embodiment, the coarse delay unit is a counting module. After the counter is full, the counting is terminated by hardware and waits for the next start pulse;

[0015] The fine delay unit is implemented by cascading programmable absolute delay units in the high-performance IO module of the FPGA. The programmable absolute delay unit consists of a 32-stage tapped delay line and a 5-bit delay counter. The tap accuracy is calibrated by the corresponding control unit. The delay accuracy calibrated by the 200 MHz system clock is 78 ps, that is, the delay of a single delay line is 78 ps;

[0016] The dynamic range is 0 to 2.5 ns. The programmable absolute delay units are cascaded to achieve a delay of 0 to 5 ns, and a delay pulse output with an adjustment accuracy of 78 ps is realized.

[0017] In a further embodiment, a pair of pulse amplifiers are designed in total. One is used for the +450V high-frequency pulse amplifier and is loaded on the corresponding positive plate;

[0018] The other is used for the -450V high-frequency pulse amplifier and is loaded on the corresponding negative plate;

[0019] In a further embodiment, the load of the pulse power amplifier is a pair of symmetric plates;

[0020] A narrow pulse corresponding to the pulse front edge makes the switch tube A conduct quickly, charging the load capacitor to a voltage of 450V;

[0021] Another narrow pulse corresponding to the pulse trailing edge makes the switch tube B conduct quickly, discharging the load capacitor, so as to obtain the required waveform on the load.

[0022] A particle beam pulse system includes:

[0023] A cutter power supply, which consists of a frequency division, pulse formation, pulse width adjustment, pulse delay, trigger pulse formation, transmission, pulse amplification circuit, and the corresponding control interface circuit and controller;

[0024] The frequency division, pulse formation, pulse width adjustment, pulse delay, trigger pulse formation, and pulse amplification circuits adopt ECL circuits (Emitter Coupled Logic integrated circuits). Utilizing the characteristics that the basic ECL gate circuits operate in a non-saturated state and have extremely high working speeds, the average delay time of the pulse processing circuit is several nanoseconds. The emitter follower is used for output, with strong driving ability. In actual use, the high level is about -0.88V and the low level is about -1.72V.

[0025] The cutter, connected to the cutter power supply, is composed of two identical deflection plates, namely the positive plate and the negative plate, which are symmetrically placed at a predetermined position in the beam pipe to form a vacuum deflection chamber.

[0026] The cutter power supply provides a pulsed voltage signal to the cutter and forms a pulsed electric field between the electrode plates to achieve the electric field excited deflection of the beam.

[0027] Beneficial effects: The present invention discloses a method and system for pulsing a particle beam. In the present invention, the cutter power supply provides a pulsed voltage signal to the deflection plates, forms a pulsed electric field between the deflection plates, realizes the deflection of the beam excited by the electric field, and further completes the cutting of the continuous beam into pulsed beams. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the system implementation principle of the present invention.

[0029] Figure 2 It is the equivalent circuit of the cutter electrode of the present invention.

[0030] Figure 3 It is a schematic diagram of the generation of the pulse on and pulse off signals of the present invention.

[0031] Figure 4 It is a schematic diagram of the fine delay unit of the present invention.

[0032] Figure 5 It is a block diagram of the principle of the pulse width formation circuit of the present invention.

[0033] Figure 6 It is a block diagram of the principle of the pulse drive circuit of the present invention.

[0034] Figure 7 It is a schematic diagram of the pulse amplifier circuit of the present invention.

[0035] Figure 8 It is a schematic diagram of the structure of the pulse transformer of the present invention.

[0036] Figure 9 It is a schematic diagram of the positive and negative pulse waveforms of the power supply output of the present invention. Detailed Embodiments

[0037] This application relates to a method and system for pulsing a particle beam, which will be explained in detail through specific embodiments below.

[0038] A method for pulsing a particle beam includes:

[0039] Step 1: Send the beam cutting signal that has been received, amplified, and shaped into a pulse signal to a frequency divider, and form square wave pulse signals with different frequencies within the frequency divider;

[0040] Step 2: The square wave pulse signal forms two separate pulses, namely a pulse on signal and a pulse off signal. The time interval between the two pulse signals is the pulse width, and the pulse width is continuously adjustable. Then send the two signals to two pulse delay circuits respectively as delay start pulses;

[0041] Step 3: Based on the pulse sequence generated by the pulse delay circuit, generate a narrow pulse of 70V@20ns and drive the pulse transformer in the pulse power amplifier;

[0042] Step 4: The pulse transformer generates high-frequency high-voltage pulses of ±450V and sends them to the deflection plates. Among them, the ±450V DC power supply outputs to the pulse amplifier, so as to obtain the required waveform on the load and provide it to the deflection plates. At this time, the beam generated by the ion source is deflected, and the continuous beam is cut into pulsed beams.

[0043] The pulse delay circuit includes a coarse delay unit and a fine delay unit;

[0044] When the delay parameter is greater than 5ns, the coarse delay unit is adopted;

[0045] When the delay parameter is less than 5ns, the fine delay unit is adopted.

[0046] The coarse delay unit is a counting module. After the counter is full, the counting is terminated by hardware and waits for the next start pulse;

[0047] The fine delay unit is implemented by cascading programmable absolute delay units in the high-performance IO module of the FPGA. The programmable absolute delay unit consists of a 32-stage tapped delay line and a 5-bit delay counter. The tap accuracy is calibrated by the corresponding control unit. The 200MHz system clock calibrates the delay accuracy to 78ps, that is, a single delay line has a delay of 78ps;

[0048] The dynamic range is 0 - 2.5ns. Cascading the programmable absolute delay units can achieve a delay of 0 - 5ns, and realize the output of a delay pulse with an adjustment accuracy of 78ps.

[0049] A pair of pulse amplifiers are designed in total. One of them is used as a +450V high-frequency pulse amplifier and is loaded on the corresponding positive plate;

[0050] Another one is for the -450V high-frequency pulse amplifier and is loaded on the corresponding negative plate;

[0051] The load of the pulse power amplifier is a pair of symmetric plates;

[0052] A narrow pulse corresponding to the pulse front edge makes the switching transistor A conduct rapidly, charging the load capacitor to a voltage of 450V;

[0053] Another narrow pulse corresponding to the pulse trailing edge makes the switching transistor B conduct rapidly, discharging the load capacitor, thereby obtaining the required waveform on the load.

[0054] A particle beam pulsing system, comprising:

[0055] A cutter power supply, which consists of a frequency divider, a pulse former, a pulse width adjuster, a pulse delay unit, a trigger pulse former, a transmitter, a pulse amplifier circuit, and corresponding control interface circuits and a controller;

[0056] The frequency divider, pulse former, pulse width adjuster, pulse delay unit, trigger pulse former, and pulse amplifier circuit adopt ECL circuits (Emitter Coupled Logic integrated circuits). By utilizing the characteristics that the ECL basic gate circuits operate in a non-saturated state and have extremely high operating speeds, the average delay time of the pulse processing circuit is several nanoseconds. An emitter follower is used for output, with strong driving ability. In actual use, the high level is about -0.88V and the low level is about -1.72V.

[0057] A cutter, connected to the cutter power supply, is composed of two identical deflection plates, namely a positive plate and a negative plate, which are symmetrically placed at a predetermined position in the beam pipe to form a vacuum deflection chamber.

[0058] The cutter power supply provides a pulse voltage signal for the cutter and forms a pulse electric field between the electrode plates to achieve the electric field-excited deflection of the beam.

[0059] Example 1:

[0060] The cutter power supply provides a pulse voltage signal for the cutter, forming a pulse electric field between the deflection plates to achieve the electric field-excited deflection of the beam.

[0061] The cutter is composed of two identical electrode plates, which are symmetrically placed at a suitable position in the beam pipe to form a vacuum deflection chamber. Its equivalent circuit is as Figure 2 shown.

[0062] Among them, C is the capacitance between the cutter plates, and C1 and C2 are the capacitances of the two cutter plates to the ground respectively. In the example, the capacitance C between the plates is about 2.5pF, and the capacitances of the plates to the ground are both about 26pF;

[0063] The cutter power supply provides a pulsed high voltage with fast pulses for the cutter. When an appropriate working voltage is applied, the beam current generated by the ion source is deflected, and the continuous beam is cut into pulsed beams.

[0064] During the rising or falling edge stage of the pulsed output of the cutter power supply, the beam current has significant instability and may be accelerated and lost elsewhere. Therefore, the output high voltage pulse of the cutter power supply should have the characteristics of fast rising and falling edges, high voltage, and small ripple on the pulse flat top.

[0065] As shown in the Figure 1 attachment, the cutter power supply consists of a frequency divider, pulse formation, pulse width adjustment, pulse delay, trigger pulse formation, transmission, pulse amplification circuits, as well as corresponding control interface circuits and a controller.

[0066] The cutter power supply has high requirements for pulse accuracy and pulse frequency. Pulse processing circuits such as frequency division, pulse formation, pulse width adjustment, pulse delay, and trigger pulse formation use ECL circuits (Emitter Coupled Logic integrated circuits). Utilizing the characteristics that the basic ECL gate circuits operate in a non-saturated state and have extremely high working speeds, the average delay time of the pulse processing circuit is several nanoseconds. It uses an emitter follower output with strong driving ability. In actual use, the high level is about -0.88V and the low level is about -1.72V.

[0067] The 1 - 12MHz RF beam cutting signal of the system is sent through a high-frequency cable, received, amplified, and shaped into a pulsed signal, and then sent to the frequency divider.

[0068] In the frequency divider, square wave pulse signals with different frequencies can be formed under software control. Each signal forms 2 independent pulses. One is the "pulse on" signal, and the other is the "pulse off" signal. The time interval between these 2 pulses is the pulse width, which is set by software and is continuously adjustable. These 2 signals are respectively sent to 2 pulse delay circuits as delay start pulses.

[0069] As shown in the Figure 3 attachment, the pulse delay circuit mainly sends an external reference signal into the FPGA, and corresponding pulse delay units are designed inside the FPGA.

[0070] At the same time, the FPGA receives an external trigger signal generated by the accelerator system synchronous timer, which not only plays a role in system synchronization but also an interlock role.

[0071] The interlock signal is input to the safety interlock system, and system interlock can be achieved by blocking the pulse output.

[0072] The pulse delay unit is divided into a coarse delay unit and a fine delay unit. For the part of the delay parameter greater than 5 ns, we use a coarse delay module to implement it, and for the part less than 5 ns, we use a fine delay module to implement it.

[0073] The coarse delay module is actually a counting module, and the counting length is set by software. After the counter is full, the counting is terminated by hardware and waits for the next start pulse.

[0074] As shown in the appendix Figure 4 As shown, the fine delay unit is implemented by cascading programmable absolute delay units in the high-performance IO module of the FPGA. The programmable absolute delay unit consists of a 32-stage tapped delay line and a 5-bit delay counter. The tap accuracy is calibrated by the corresponding control unit. The delay accuracy calibrated by a 200 MHz system clock is 78 ps, that is, a single delay line has a delay of 78 ps. The dynamic range is 0 to 2.5 ns. The programmable absolute delay units are cascaded to achieve a delay of 0 to 5 ns, so as to realize the output of a delay pulse with an adjustment accuracy of 78 ps.

[0075] The pulse sequence generated by the pulse delay unit is sent to the pulse drive circuit (trigger pulse circuit) through the ECL circuit and coaxial cable. The pulse drive circuit generates a narrow pulse of 70V@20ns through the shaping circuit and pushes the pulse transformer in the pulse power amplifier through the coaxial cable;

[0076] The pulse transformer drives the MOS tube to generate high-frequency high-voltage pulses of ±450V and sends them to the deflection electrode. Among them, the ±450V DC power supply outputs a ±450V DC power supply to the pulse amplifier under the control of the control unit.

[0077] As shown in the appendix Figures 5 - 6 As shown, the pulse on and pulse off signals are uniformly adjusted to 20 ns in pulse width through the shaping circuit and output high-voltage pulse signals through the drive and amplification circuits.

[0078] Among them, the amplifying tubes of the drive stage amplifier and the final stage amplifier both use high-speed RF MOSFET amplifying tubes. The switching speed can reach 3 - 4 ns, the maximum operating voltage is 1000V, and the pulse peak current is 90A.

[0079] The pulse drive circuit outputs 2 pairs of 70V pulses through a 50Ω coaxial cable to drive the +450V and -450V pulse amplifiers respectively.

[0080] There is a total of 1 pair of pulse amplifiers, and the circuits are exactly the same. One of them is used for the +450V high-frequency pulse modulator (pulse amplifier) and is loaded on the corresponding positive plate, and one is used for the -450V high-frequency pulse modulator (pulse amplifier) and is loaded on the corresponding negative plate.

[0081] For the -450V high-frequency pulse modulator, the circuit is exactly the same as that of the +450V high-frequency pulse modulator.

[0082] As shown in the appendix Figure 7 The load of the pulse power amplifier is a pair of symmetric plates, which can be equivalent to a capacitor of about 30 pF. A narrow pulse corresponding to the pulse front edge makes the switching transistor A conduct rapidly, charging the load capacitor to a voltage of 450V. A narrow pulse corresponding to the pulse trailing edge makes the switching transistor B conduct rapidly, discharging the load capacitor, so that the required waveform can be obtained on the load.

[0083] Since the repetition frequency of the output pulse is as high as 12 MHz, the front and trailing edges are better than 15 ns, and the pulse voltage amplitude is required to reach 450V.

[0084] The gates of all switching transistors are isolated and driven by magnetic core (NXO-100) pulse transformers.

[0085] Since the gate input capacitance of the RF MOSFET is about 2000 pF, a 6:1 transformer is used for the pulse transformer. As shown in the appendix Figure 8 It has 6 turns in the primary and 1 turn in the secondary. The 70V drive pulse is reduced to 12V. Moreover, the secondary is wound with 4 groups of wide copper strips in parallel to reduce the inductance and resistance of the secondary and provide a large current pulse drive.

[0086] At the same time, considering the self-output capacitance of the RF MOSFET, the distributed parameter capacitance and the equivalent capacitance of the plates, the output equivalent capacitance of the RF MOSFET is about 400 pF.

[0087] The pulse amplifier is designed in the way of liquid cooling with copper plates.

[0088] The RF MOSFET and the absorption resistor R1 are both welded to the cooling copper plate. The higher the operating frequency and the operating voltage, the greater the cooling requirement for the R1 resistor, and the higher the power level required for the R1 resistor.

[0089] For example, for a 4 MHz 450V pulse signal, the charging and discharging power of the capacitor is about 170W (W = 1 / 2CV2·Freq), and basically all the above power is consumed on the R1 resistor.

[0090] The cutter power supply needs to output two groups of signals. As shown in the appendix Figure 9 One group is the +V0~+HV waveform, and the other group is the -V0~-HV waveform. The two groups of signals are synchronous.

[0091] In the figure, T is the period, Δt is the pulse width, Δt1 is the rising edge width, Δt2 is the falling edge width, +HV is the positive peak value, -HV is the negative peak value, and +V0 and -V0 are the zero points.

[0092] Description of the working principle:

[0093] The beam cutting signal, which has been received, amplified, and shaped into a pulse signal, is sent to a frequency divider, where square wave pulse signals of different frequencies are formed.

[0094] The square wave pulse signal forms two separate pulses, namely the pulse on signal and the pulse off signal. The time interval between the two pulse signals is the pulse width, which is continuously adjustable. Then the two signals are sent to two pulse delay circuits respectively as delay start pulses.

[0095] Based on the pulse sequence generated by the pulse delay circuit, a narrow pulse of 70V@20ns is generated to drive the pulse transformer in the pulse power amplifier.

[0096] The pulse transformer generates high-frequency high-voltage pulses of ±450V and sends them to the deflection plates. Among them, the ±450V DC power supply is output to the pulse amplifier, so that the required waveform can be obtained on the load and provided to the deflection plates. At this time, the beam current generated by the ion source is deflected, and the continuous beam is cut into a pulsed beam.

[0097] The preferred specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above specific embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A particle beam pulsing method, characterized in that: include: Step 1: Send the beam-cutting signal received, amplified and shaped into a pulse signal to the frequency divider, and form square wave pulse signals of different frequencies in the frequency divider; Step 2: The square wave pulse signal forms two separate pulses, namely a pulse on signal and a pulse off signal. The time interval between the two pulse signals is the pulse width, and the pulse width is continuously adjustable. The two signals are sent to two pulse delay circuits respectively as delayed start pulses. Step 3: Based on the pulse sequence generated by the pulse delay circuit, a narrow pulse with an amplitude of 70V and a pulse width of 20ns is generated, and the pulse transformer in the pulse power amplifier is driven; Step 4: The pulse transformer generates ±450V high-frequency high-voltage pulses and sends them to the deflection plates. The ±450V DC power supply is output to the pulse amplifier, thereby obtaining the required waveform on the load and providing it to the deflection plates. At this time, the beam generated by the ion source is deflected and the continuous beam is cut into a pulse beam.

2. A particle beam pulsing method according to claim 1, characterized in that: The pulse delay circuit includes a coarse delay unit and a fine delay unit; When the delay parameter is greater than 5ns, a coarse delay unit is used; When the delay parameter is less than 5ns, a fine delay unit is used.

3. A particle beam pulsing method according to claim 2, characterized in that: The coarse delay unit is a counting module. When the counter is full, the hardware stops counting and waits for the next start pulse. The fine delay unit is implemented by cascading programmable absolute delay units in the FPGA high-performance IO module. The programmable absolute delay unit consists of a 32-order tap delay line and a 5-bit delay counter. The tap accuracy is calibrated by the corresponding control unit. The calibrated delay accuracy of the 200MHz system clock is 78ps, that is, a single delay line has a delay of 78ps. The dynamic range is 0 to 2.5ns. The programmable absolute delay units are cascaded to achieve a delay of 0 to 5ns, realizing a delayed pulse output with an adjustment accuracy of 78ps.

4. The particle beam pulsing method according to claim 1, characterized in that: The pulse amplifier is designed in pairs, one of which is used for +450V high-frequency pulse amplifier and loaded on the corresponding positive plate; The other one is used for -450V high frequency pulse amplifier and is loaded on the corresponding negative plate.

5. A particle beam pulsing method according to claim 4, characterized in that: The load of the pulse power amplifier is a symmetrical plate; A narrow pulse corresponding to the leading edge of the pulse turns on the switch tube A quickly, charging the load capacitor to a voltage of 450V. Another narrow pulse corresponding to the trailing edge of the pulse causes the switch tube B to turn on quickly, discharging the load capacitor, thereby obtaining the required waveform on the load.

6. The particle beam pulsing method according to claim 1, characterized in that: include: Cutter power supply; a cutter, connected to the cutter power supply, and composed of two identical deflection plates, namely a positive plate and a negative plate, which are axially symmetrically placed at predetermined positions of the beam pipeline to achieve uniform distribution of the pulse electric field and control of beam deflection accuracy, forming a vacuum deflection chamber; The cutter power supply provides a pulse voltage signal for the cutter and forms a pulse electric field between the electrode plates to achieve electric field excitation deflection of the beam.

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