CN117915539A - Particle beam pulsing method and system - Google Patents

Abstract

The invention discloses a particle beam pulsing method and a system, wherein the method comprises the following steps: step 1, transmitting a beam cutting signal which is 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, forming two paths of independent pulses by using square wave pulse signals, namely pulse on signals and pulse off signals, wherein the time interval between the two paths of pulse signals is pulse width, the pulse width is continuously adjustable, and the two paths of signals are respectively sent to two pulse delay circuits to be used as delay starting pulses; step 3, generating a 70V@20ns narrow pulse based on a pulse sequence generated by a pulse delay circuit, and pushing a pulse transformer in a pulse power amplifier; and 4, generating high-frequency high-voltage pulses of +/-450V by the pulse transformer, and sending the high-frequency high-voltage pulses to the deflection polar plate, wherein a direct-current power supply of +/-450V is output to the pulse amplifier.

Description

Particle beam pulsing method and system

Technical Field

The invention relates to the field of accelerators, in particular to a particle beam pulsing method and a system;

Background

Particle beam refers to a flowing collection of a large number of particles that have similar properties and states of motion and are collected together in space at high velocities and high flow densities. The particle beam may include different kinds of particles such as electron beam, ion beam, neutron beam, etc.

The formation of the particle beam can be achieved in different ways, one common approach being the use of particle accelerators. Particle accelerators can accelerate charged particles (e.g., electrons or ions) to high energies and focus them into a beam stream. This may be achieved by an electric field, a magnetic field or a combination of both. The focusing system may focus the particle beam and maintain its relatively narrow diameter for ease of experimentation, application or further processing.

However, no efficient and stable way is currently proposed for how to convert a continuous beam into a pulsed beam.

Disclosure of Invention

The invention aims to: a particle beam pulsing method and system for realizing low-energy particle continuous particle beam pulsing is provided, and a cutter is used for cutting the beam into pulse strings and outputting the pulse strings to solve the problems in the prior art.

The technical scheme is as follows: a method of particle beam pulsing comprising:

Step1, transmitting a beam cutting signal which is 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, forming two paths of independent pulses by using square wave pulse signals, namely pulse on signals and pulse off signals, wherein the time interval between the two paths of pulse signals is pulse width, the pulse width is continuously adjustable, and the two paths of signals are respectively sent to two pulse delay circuits to be used as delay starting pulses;

Step 3, generating a 70V@20ns narrow pulse based on a pulse sequence generated by a pulse delay circuit, and pushing a pulse transformer in a pulse power amplifier;

And 4, generating high-frequency high-voltage pulses of +/-450V by a pulse transformer, and sending the high-frequency high-voltage pulses to a deflection polar plate, wherein a direct-current power supply of +/-450V is output to a pulse amplifier, so that a required waveform is obtained on a load and is provided to the deflection polar plate, and at the moment, the beam current generated by an ion source is deflected, and the continuous beam is cut into pulse beams.

In a further embodiment, the pulse delay circuit comprises a coarse delay unit and a fine delay unit;

when the delay parameter is greater than 5ns, a coarse delay unit is adopted;

And when the delay parameter is smaller than 5ns, adopting a fine delay unit.

In a further embodiment, the coarse delay unit is a counting module, and after the counter is full, the hardware stops counting and waits for the next starting pulse;

The fine delay unit is realized by adopting a programmable absolute delay unit cascade in an 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 precision is calibrated by a corresponding control unit, and the calibration delay precision of a 200MHz system clock is 78ps, namely the single delay line is 78ps delay;

and the dynamic range is 0-2.5 ns, and the programmable absolute delay units are cascaded to achieve 0-5 ns delay, so that delay pulse output with the adjustment precision of 78ps is realized.

In a further embodiment, the pulse amplifiers are designed in a pair, wherein one block is used for the +450V high-frequency pulse amplifier and is loaded on the corresponding positive plate;

The other block is used for a-450V high-frequency pulse amplifier and is loaded on a corresponding negative plate;

In a further embodiment, the load of the pulse power amplifier is a symmetric plate;

A narrow pulse corresponding to the pulse front edge enables the switch tube A to be rapidly conducted, and charges a load capacitor to reach 450V voltage;

the other narrow pulse corresponding to the trailing edge of the pulse causes the switching tube B to be rapidly conducted, and the load capacitor to be discharged, so that a required waveform is obtained on the load.

A particle beam pulsing system comprising:

The cutter power supply consists of a frequency division circuit, a pulse forming circuit, a pulse width adjusting circuit, a pulse delay circuit, a trigger pulse forming circuit, a transmission circuit, a pulse amplifying circuit, a corresponding control interface circuit and a controller;

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), the characteristics that an ECL basic gate circuit works in a non-saturated state and the working speed is extremely high are utilized, the average delay time of a pulse processing circuit is several ns, the output of an emitter follower is adopted, the driving capability is strong, the actual use of the pulse processing circuit is about-0.88V, and the low level is about-1.72V.

The cutter is communicated with the cutter power supply and consists of two identical deflection polar plates, namely a positive plate and a negative plate, which are axially symmetrically arranged at a preset position of the beam pipeline to form a vacuum deflection chamber,

The cutter power supply provides pulse voltage signals for the cutter, and a pulse electric field is formed between the electrode plates, so that the electric field excitation deflection of beam current is realized.

The beneficial effects are that: the invention discloses a particle beam pulsing method and a system, wherein a cutter power supply provides pulse voltage signals for deflection polar plates, a pulse electric field is formed between the deflection polar plates, deflection excited by the electric field of the beam is realized, and then continuous beams are cut into pulse beams.

Drawings

Fig. 1 is a schematic diagram of the system implementation principle of the present invention.

Fig. 2 is a cutter electrode equivalent circuit of the present invention.

Fig. 3 is a schematic diagram of the pulse on and pulse off signal generation of the present invention.

Fig. 4 is a schematic diagram of a fine delay cell of the present invention.

Fig. 5 is a schematic block diagram of a pulse width forming circuit of the present invention.

Fig. 6 is a schematic block diagram of a pulse drive circuit of the present invention.

Fig. 7 is a schematic diagram of a pulse amplifier circuit of the present invention.

Fig. 8 is a schematic diagram of the pulse transformer structure of the present invention.

Fig. 9 is a schematic diagram of the power output positive and negative pulse waveforms of the present invention.

Detailed Description

The application relates to a particle beam pulsing method and a system, and the method and the system are explained in detail through specific embodiments.

A method of particle beam pulsing comprising:

Step1, transmitting a beam cutting signal which is 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, forming two paths of independent pulses by using square wave pulse signals, namely pulse on signals and pulse off signals, wherein the time interval between the two paths of pulse signals is pulse width, the pulse width is continuously adjustable, and the two paths of signals are respectively sent to two pulse delay circuits to be used as delay starting pulses;

Step 3, generating a 70V@20ns narrow pulse based on a pulse sequence generated by a pulse delay circuit, and pushing a pulse transformer in a pulse power amplifier;

And 4, generating high-frequency high-voltage pulses of +/-450V by a pulse transformer, and sending the high-frequency high-voltage pulses to a deflection polar plate, wherein a direct-current power supply of +/-450V is output to a pulse amplifier, so that a required waveform is obtained on a load and is provided to the deflection polar plate, and at the moment, the beam current generated by an ion source is deflected, and the continuous beam is cut into pulse beams.

The pulse delay circuit comprises a coarse delay unit and a fine delay unit;

when the delay parameter is greater than 5ns, a coarse delay unit is adopted;

And when the delay parameter is smaller than 5ns, adopting a fine delay unit.

The coarse delay unit is a counting module, and after the counter is full, the counting is stopped by hardware to wait for the next starting pulse;

The fine delay unit is realized by adopting a programmable absolute delay unit cascade in an 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 precision is calibrated by a corresponding control unit, and the calibration delay precision of a 200MHz system clock is 78ps, namely the single delay line is 78ps delay;

and the dynamic range is 0-2.5 ns, and the programmable absolute delay units are cascaded to achieve 0-5 ns delay, so that delay pulse output with the adjustment precision of 78ps is realized.

The pulse amplifiers are designed in a pair, wherein one of the pulse amplifiers is used for a +450V high-frequency pulse amplifier and is loaded on a corresponding positive plate;

The other block is used for a-450V high-frequency pulse amplifier and is loaded on a corresponding negative plate;

The load of the pulse power amplifier is a symmetrical polar plate;

A narrow pulse corresponding to the pulse front edge enables the switch tube A to be rapidly conducted, and charges a load capacitor to reach 450V voltage;

the other narrow pulse corresponding to the trailing edge of the pulse causes the switching tube B to be rapidly conducted, and the load capacitor to be discharged, so that a required waveform is obtained on the load.

A particle beam pulsing system comprising:

The cutter power supply consists of a frequency division circuit, a pulse forming circuit, a pulse width adjusting circuit, a pulse delay circuit, a trigger pulse forming circuit, a transmission circuit, a pulse amplifying circuit, a corresponding control interface circuit and a controller;

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), the characteristics that an ECL basic gate circuit works in a non-saturated state and the working speed is extremely high are utilized, the average delay time of a pulse processing circuit is several ns, the output of an emitter follower is adopted, the driving capability is strong, the actual use of the pulse processing circuit is about-0.88V, and the low level is about-1.72V.

The cutter is communicated with the cutter power supply and consists of two identical deflection polar plates, namely a positive plate and a negative plate, which are axially symmetrically arranged at a preset position of the beam pipeline to form a vacuum deflection chamber,

The cutter power supply provides pulse voltage signals for the cutter, and a pulse electric field is formed between the electrode plates, so that the electric field excitation deflection of beam current is realized.

Embodiment one:

The cutter power supply provides pulse voltage signals for the cutter, a pulse electric field is formed between the deflection polar plates, and the deflection excited by the electric field of the beam current is realized.

The cutter is composed of two identical electrode plates, and is axially symmetrically arranged at a proper position of the beam pipeline to form a vacuum deflection chamber, and the equivalent circuit of the vacuum deflection chamber is shown in figure 2.

Wherein C is the capacitance between the plates of the cutter, and C1 and C2 are the capacitances to ground of the two cut plates, respectively. In the example, the inter-plate capacitance C is about 2.5pF, and the plate-to-ground capacitances are about 26pF;

The cutter power supply provides a fast pulsed high voltage to the cutter, and when a suitable operating voltage is applied, the beam current generated by the ion source is deflected and the continuous beam is cut into pulsed beams.

In the stage of the rising edge or the falling edge of the output pulse of the cutter power supply, the beam current has larger instability and possibly is accelerated and lost in other places, so the output high-voltage pulse of the cutter power supply has the characteristics of rapid rising edge and falling edge, higher voltage and smaller flat-topped ripple wave of the pulse.

As shown in fig. 1, the cutter power supply consists of frequency division, pulse formation, pulse width adjustment, pulse delay, trigger pulse formation, transmission, pulse amplification circuits, corresponding control interface circuits and controllers.

The cutter power supply has high requirements on pulse precision and pulse frequency, and pulse processing circuits such as frequency division, pulse formation, pulse width adjustment, pulse delay, trigger pulse formation and the like adopt ECL circuits (emitter coupled logic integrated circuits). The ECL basic gate circuit works in an unsaturated state and has extremely high working speed, the average delay time of the pulse processing circuit is several ns, the emitter follower is adopted for output, the driving capability is strong, and the high level is about-0.88V and the low level is about-1.72V in practical use.

The 1-12MHz RF cut beam signal sent from the system through the high frequency cable is received, amplified, shaped into a pulse signal, and sent to the frequency divider.

The square wave pulse signals with different frequencies can be formed in the frequency divider by software control, each signal forms 2 paths of independent pulses, one path is a pulse on signal, the other path is a pulse off signal, the time interval between the 2 paths of pulses is pulse width, the pulse width is set by software, the pulse width is continuously adjustable, and the 2 paths of signals are respectively sent to 2 blocks of pulse delay circuits to serve as delay starting pulses.

As shown in figure 3, the pulse delay circuit mainly transmits an external reference signal to the FPGA, and a corresponding pulse delay unit is designed in the FPGA.

Meanwhile, the FPGA receives an external trigger signal to generate a synchronization timer of the accelerator system, so that the system synchronization function and the interlocking function are achieved.

The interlock signal is the input of the safety interlock system, and the system interlock can be achieved by blocking pulse output.

The pulse delay unit is divided into a coarse delay unit and a fine delay unit, and for the part with delay parameters larger than 5ns, the part with delay parameters smaller than 5ns is realized by adopting a coarse delay module.

The coarse delay module is actually a counting module, the counting length is set by software, and after the counter is full, the counting is stopped by hardware to wait for the next starting pulse.

As shown in figure 4, the fine delay unit is realized by adopting a programmable absolute delay unit cascade in an 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 precision is calibrated by a corresponding control unit, and the calibration delay precision of a 200MHz system clock is 78ps, namely, the single delay line is 78ps delay. The dynamic range is 0-2.5 ns, and the programmable absolute delay units are cascaded to achieve the purpose of 0-5 ns delay, so that the delay pulse output with the adjustment precision of 78ps is realized.

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

the pulse transformer drives the MOS tube to generate high-frequency high-voltage pulse with the voltage of +/-450V and send the pulse to the deflection electrode, wherein the +/-450V direct current power supply outputs the +/-450V direct current power supply to the pulse amplifier under the control of the control unit.

As shown in figures 5-6, pulse on and pulse off signals are uniformly adjusted to 20ns in pulse width by a shaping circuit, and high-voltage pulse signals are output by a driving and amplifying circuit.

The high-speed RF MOSFET amplifying tubes are adopted in the amplifying tubes of the driving stage amplifier and the final stage amplifier, the switching speed can reach 3-4ns, the maximum working voltage is 1000V, and the pulse peak current is 90A.

The pulse driving circuit outputs 2 pairs of 70V pulses through a 50Ω coaxial cable, and drives +450V and-450V pulse amplifiers respectively.

The pulse amplifiers are 1 pair in total, and the circuits are identical. Of these, 1 block was used for +450V high frequency pulse modulator (pulse amplifier) and was loaded on the corresponding positive plate, and 1 block was used for-450V high frequency pulse modulator (pulse amplifier) and was loaded on the corresponding negative plate.

For a-450V high frequency pulse modulator, the circuit is identical to a +450V high frequency pulse modulator.

As shown in fig. 7, the load of the pulse power amplifier is a symmetrical polar plate, which can be equivalent to a capacitor of about 30pF, a narrow pulse corresponding to the pulse front edge makes the switching tube a rapidly turned on to charge the load capacitor to 450V voltage, and a narrow pulse corresponding to the pulse rear edge makes the switching tube B rapidly turned on to discharge the load capacitor, so that a required waveform is obtained on the load.

The repetition frequency of the output pulse is up to 12MHz, the front and back edges are better than 15ns, and the pulse voltage amplitude is required to reach 450V.

And the grid electrodes of all the switching tubes are driven in an isolated manner by adopting a magnetic ring (NXO-100) pulse transformer.

Since the gate input capacitance of the RF MOSFET is about 2000pF, the pulse transformer adopts a 6:1 transformer, as shown in figure 8, the primary is 6 circles and the secondary is 1 circle, the driving pulse of 70V is reduced to 12V, and the secondary adopts 4 groups of wide copper strips which are wound in parallel, so that the inductance and resistance of the secondary are reduced, and the high-current pulse driving is provided.

Meanwhile, because of the comprehensive consideration of the self output capacitance of the RF MOSFET, the distributed parameter capacitance and the polar plate equivalent capacitance, the output equivalent capacitance of the RF MOSFET is about 400 pF.

The pulse amplifier is designed in a copper plate liquid cooling mode.

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

For example, for a 4mhz 450v pulse signal, the charge-discharge power of the capacitor is about 170W (w=1/2 CV2·freq), and the power is basically consumed in the R1 resistor.

The cutter power supply needs to output two groups of signals, as shown in figure 9, one group is +V0- +HV waveform, the other group is-V0- +HV waveform, and the two groups of signals are synchronous.

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

Description of working principle:

The beam cutting signals which are received, amplified and shaped into pulse signals are sent to a frequency divider, and square wave pulse signals with different frequencies are formed in the frequency divider;

The square wave pulse signals form two paths of independent pulses which are pulse on signals and pulse off signals respectively, the time interval between the two paths of pulse signals is pulse width, the pulse width is continuously adjustable, and the two paths of signals are respectively sent to two pulse delay circuits to be used as delay starting pulses;

Based on a pulse sequence generated by the pulse delay circuit, generating a narrow pulse of 70V@20ns and pushing a pulse transformer in the pulse power amplifier;

The pulse transformer generates a high frequency high voltage pulse of + -450V and sends it to the deflection plate, wherein a + -450V DC power supply outputs to the pulse amplifier to obtain the desired waveform on the load and provide it to the deflection plate, at which time the beam current generated by the ion source is deflected and the continuous beam is cut into pulsed beams.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the embodiments, and various equivalent changes can be made to the technical solutions of the present invention within the scope of the technical concept of the present invention, and all such equivalent changes belong to the protection scope of the present invention.

Claims (6)

1. A method of pulsing a particle beam, comprising:

Step1, transmitting a beam cutting signal which is 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, forming two paths of independent pulses by using square wave pulse signals, namely pulse on signals and pulse off signals, wherein the time interval between the two paths of pulse signals is pulse width, the pulse width is continuously adjustable, and the two paths of signals are respectively sent to two pulse delay circuits to be used as delay starting pulses;

Step 3, generating a 70V@20ns narrow pulse based on a pulse sequence generated by a pulse delay circuit, and pushing a pulse transformer in a pulse power amplifier;

And 4, generating high-frequency high-voltage pulses of +/-450V by a pulse transformer, and sending the high-frequency high-voltage pulses to a deflection polar plate, wherein a direct-current power supply of +/-450V is output to a pulse amplifier, so that a required waveform is obtained on a load and is provided to the deflection polar plate, and at the moment, the beam current generated by an ion source is deflected, and the continuous beam is cut into pulse beams.

2. A particle beam pulsing method according to claim 1 wherein: the pulse delay circuit comprises a coarse delay unit and a fine delay unit;

when the delay parameter is greater than 5ns, a coarse delay unit is adopted;

And when the delay parameter is smaller than 5ns, adopting a fine delay unit.

3. A particle beam pulsing method according to claim 2 wherein: the coarse delay unit is a counting module, and after the counter is full, the counting is stopped by hardware to wait for the next starting pulse;

The fine delay unit is realized by adopting a programmable absolute delay unit cascade in an 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 precision is calibrated by a corresponding control unit, and the calibration delay precision of a 200MHz system clock is 78ps, namely the single delay line is 78ps delay;

and the dynamic range is 0-2.5 ns, and the programmable absolute delay units are cascaded to achieve 0-5 ns delay, so that delay pulse output with the adjustment precision of 78ps is realized.

4. A particle beam pulsing method according to claim 1 wherein: the pulse amplifiers are designed in a pair, wherein one of the pulse amplifiers is used for a +450V high-frequency pulse amplifier and is loaded on a corresponding positive plate;

the other block is used for a-450V high-frequency pulse amplifier and is loaded on a corresponding negative plate.

5. The method of claim 4, wherein the step of pulsing the particle beam is: the load of the pulse power amplifier is a symmetrical polar plate;

A narrow pulse corresponding to the pulse front edge enables the switch tube A to be rapidly conducted, and charges a load capacitor to reach 450V voltage;

the other narrow pulse corresponding to the trailing edge of the pulse causes the switching tube B to be rapidly conducted, and the load capacitor to be discharged, so that a required waveform is obtained on the load.

6. A particle beam pulsing system comprising:

A cutter power supply;

The cutter is communicated with a power supply of the cutter and consists of two identical deflection polar plates, namely a positive plate and a negative plate, which are axially symmetrically arranged at a preset position of the beam pipeline to form a vacuum deflection chamber;

The cutter power supply provides pulse voltage signals for the cutter, and a pulse electric field is formed between the electrode plates, so that the electric field excitation deflection of beam current is realized.