Method for reducing electron load of high-frequency pulse negative hydrogen ion source absorption electrode

Abstract

The invention discloses a method for reducing the electron load of a high-frequency pulse negative hydrogen ion source absorption electrode, which comprises the following steps of: igniting plasma by using high-frequency medium-power pulse of a continuously output high-frequency driving signal, and delaying the high-frequency low-power pulse by using a double-frequency driving device, the delayed time enables the amplitude of the pulse maintaining the plasma state to be the lowest, and the pulse width only accounts for several percent of the repetition period of the high-yield pulse; maintaining a plasma state: maintaining the continuous state of the plasma by using a high-frequency low-power pulse of a high-frequency driving signal of pulse output, and limiting the high-frequency low-power pulse to be a pulse with medium pulse width and lowest amplitude; a large amount of plasmas are generated through low frequency and high power of low-frequency driving signals output by pulses, the pulses are limited to be the pulses with the narrowest pulse width and the very high amplitude, and the negative hydrogen ion source absorption electrode electronic load is reduced by selecting a proper duty ratio for a high-power pulse gap.

Description

Technical Field

[0001] The invention belongs to the technical field of negative hydrogen ion sources, and in particular relates to a method for reducing the electron load of a high-frequency pulse negative hydrogen ion source. Background Art

[0002] High-intensity pulsed negative hydrogen ion sources are widely used in particle accelerators, semiconductor processes and controlled nuclear fusion research. Among them, pulsed negative hydrogen ion sources that use high-frequency power to drive ionization have longer maintenance intervals and more direct and convenient pulse modulation, so they are favored by related fields.

[0003] However, the ionization and extraction process in the high-frequency pulsed negative hydrogen ion source is accompanied by a large number of electrons, which will be extracted together with the negative hydrogen ion beam and form an electronic load at the anode that may reach or exceed the negative hydrogen ion beam by dozens of times or even hundreds of times, which puts extremely high demands on the pulse load capacity of the anode power supply and the heat dissipation of the anode itself; in addition, the instantaneous temperature rise effect of the anode electronic load may also demagnetize its embedded permanent magnet, making it impossible for the negative hydrogen ion source to normally distinguish between the extracted ion beam and the symbiotic electrons.

[0004] A common method of reducing the negative hydrogen ion source suction load in the prior art is to add alkali metal vapor (such as cesium vapor) into the store environment. The problem with this method is that it is effective for both pulse and DC negative hydrogen ion sources, but it will pollute the discharge environment and is destined to pollute the subsequent process environment; at the same time, the structure of the cesium furnace system itself is also relatively complex, which increases the cost and difficulty of maintenance. When used on a high-frequency driven pulse negative hydrogen ion source, it is likely to make its advantage of longer maintenance intervals impossible to play; in addition, for a high-frequency pulse negative hydrogen ion source that uses a built-in antenna to drive ionization, the attachment of cesium vapor or other alkali metal vapor to the built-in antenna will gradually reduce the efficiency of high-frequency power feed-in, and eventually make the antenna ineffective; in addition, alkali metal vapor also increases the probability of high-voltage ignition of the equipment, which is also detrimental to the overall stability and safety of the system. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention proposes a method for reducing the electron load of a high-frequency pulsed negative hydrogen ion source. The purpose is to solve the problem that a large number of electrons are associated with the ionization and extraction processes in the existing high-frequency pulsed negative hydrogen ion source. A large number of electrons will be extracted together with the negative hydrogen ion beam and form an electron load at the electrode that may reach or exceed the negative hydrogen ion beam by dozens of times or even dozens of times, which puts forward extremely high requirements on the pulse load capacity of the electrode power supply and the heat dissipation of the electrode itself; the instantaneous temperature rise effect of the electron load of the electrode will demagnetize the embedded permanent magnet, thereby making it impossible for the negative hydrogen ion source to normally distinguish between the extracted ion beam and the symbiotic electrons.

[0006] The present invention adopts the following technical solutions to solve the technical problems:

[0007] A method for reducing the electron load of a high-frequency pulsed negative hydrogen ion source. The method is based on a dual-frequency driving device. The dual-frequency driving device provides a dual-frequency driving signal to be amplified for a third-party power amplifier. After passing through the third-party power amplifier, the dual-frequency driving device generates a high-frequency medium power for a cold start state, a high-frequency low power for maintaining a plasma existence state, and a low-frequency high power for generating a large amount of plasma; the dual-frequency driving signal includes a continuously output high-frequency driving signal, and the continuously output high-frequency driving signal contains the frequency and amplitude characteristics for the cold start state; the dual-frequency driving signal includes a pulsed high-frequency driving signal, and the pulsed high-frequency driving signal contains the frequency, amplitude, and time delay characteristics for maintaining a plasma existence state; the dual-frequency driving signal includes a pulsed low-frequency driving signal, and the pulsed low-frequency driving signal contains the frequency, amplitude, and time delay characteristics for generating high-yield plasma pulses; the method is characterized in that the method includes the following steps:

[0008] Step 1, cold start state: ignite the plasma with the high frequency medium power of the continuously output high frequency driving signal, then use the dual frequency driving device to add a delay to the high frequency low power pulse outputted by the subsequent pulse, the delay time makes the amplitude of the subsequent high frequency low power pulse for maintaining the plasma state to be the lowest, and the pulse width only accounts for a few percent of the repetition period of the low frequency high power pulse for producing plasma with large output, at this time, the anode power supply is not powered; the high frequency medium power pulse is also called a cold start pulse;

[0009] Step 2, maintaining the plasma state: using the high frequency and low power of the high frequency driving signal output by the pulse to maintain the plasma state, and limiting the high frequency and low power pulse to a pulse with a pulse width that is only a few percent of the repetition period of the low frequency and high power pulse and with the lowest amplitude; while starting the high frequency and low power pulse, using a dual frequency driving device to add a delay to the low frequency and high power pulse, the delay time is the repetition period of the low frequency and high power pulse minus the sum of the pulse widths of the low frequency and high power pulse and the high frequency and low power pulse; at this time, the anode power supply of the high frequency pulse negative hydrogen ion source is powered on when a DC high voltage power supply is used, and is not powered on when a pulse high voltage power supply is used; the high frequency and low power pulse is also called a maintaining pulse;

[0010] Step 3, mass production of plasma state: use the low-frequency and high-power of the low-frequency driving signal of the pulse output to generate a large amount of plasma, and limit the pulse to a pulse with the narrowest pulse width and the highest amplitude, and then use the dual-frequency driving device to continue to delay the high-frequency and low-power pulse output for maintaining the plasma state; the delay time makes the subsequent high-frequency and low-power pulses that continue to maintain the plasma state have the lowest amplitude, and the pulse width only accounts for a few percent of the repetition period of the low-frequency and high-power pulses for mass production of plasma; and make the anode power supply output at the set high voltage at full power; the low-frequency and high-power pulses are also called high-yield pulses;

[0011] Step 4: Check whether the current high-frequency pulse negative hydrogen ion source has finished working. If yes, then end. If not, return to step 2.

[0012] Furthermore, the high-frequency low-power pulse width used to maintain the plasma in the step 2 is less than 5% of the repetition period of the low-frequency high-power pulse.

[0013] Furthermore, when the low-frequency high-power pulse width accounts for 1% of the low-frequency high-power pulse repetition period and the high-frequency low-power pulse width accounts for less than 5% of the low-frequency high-power pulse repetition period, the delay duration accounts for 94% of the low-frequency high-power pulse repetition period.

[0014] Furthermore, the pulse width of the low-frequency, high-power pulses used for mass production of plasma in step three is determined according to user needs.

[0015] Furthermore, the duration of delaying the low-frequency high-power pulse in step 2 is the pulse width of the high-frequency low-power pulse, that is, the falling edge of the high-frequency low-power pulse is the rising edge of the low-frequency high-power pulse.

[0016] Furthermore, the high frequency medium power in step one is 13 MHz and 300 W.

[0017] Furthermore, the high frequency and low power of step 2 is 13 MHz and 100 W.

[0018] Furthermore, the low frequency and high power of step three is 2 MHz and 80 kW.

[0019] Furthermore, the cold start pulse width of step one is greater than the sum of the sustaining pulse width and the high-yield pulse width: this width is required to ensure that the plasma is ignited, obtain the optimal electron and plasma density in the discharge chamber, and enable the system to reach thermal stability conditions under working conditions.

[0020] Advantages and effects of the present invention

[0021] 1. The present invention cleverly utilizes the characteristic that high-power pulses will still have residual electrons when not powered. By selecting a suitable duty cycle (94% duty cycle) for the high-power pulse gap, the pulse that maintains the plasma state not only has a pulse width of only 5% of the high-power pulse gap, but also has the lowest pulse amplitude, thereby reducing the negative hydrogen ion source anode electron load.

[0022] 2. The present invention reduces the time of the 13.56MHz power maintaining the plasma existence state from the original 99% to less than 5%, so the electronic load is reduced by more than ten times; if the power maintaining the plasma is replaced by the power of repeated ignition, since the power amplitude of maintaining the plasma is lower than the amplitude of the ignition power, the time of the 13.56MHz ignition power is reduced, and the electronic load is further reduced on the basis of the more than ten times reduction of the electronic load. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of pulse width and time interval of three pulses of negative hydrogen ion source of the present invention;

[0024] Figure 2 A schematic diagram of the frequencies and time intervals of three pulses of the negative hydrogen ion source of the present invention;

[0025] Figure 3 This is a diagram showing the effect of reducing the negative hydrogen ion source absorption and electron extraction of the present invention;

[0026] Figure 4 This is a flow chart of the method for reducing the electron load of the high-frequency pulse negative hydrogen ion source in the present invention;

[0027] Figure 5 This is an application effect diagram of the dual-frequency driving device of the present invention;

[0028] Figure 6 This is a structural diagram of a dual-frequency driving device for a pulse high-frequency ionization device according to the present invention;

[0029] Figure 7 Schematic diagram of the negative hydrogen ion source anode electron load. Specific implementation methods

[0031] Design principle of the present invention

[0032] 1. The innovation of the present invention is that a suitable time interval (delay time) is selected for the high-frequency low-power pulse, which can reduce the electron load of the anode to the maximum extent, and at the same time, can make the plasma state more stable when the next low-frequency high-power pulse arrives. The time interval accounts for 94% of the repetition period of the entire high-yield pulse (low-frequency high-power pulse). If it is greater than this 94% time interval, the residual electron density generated by the high-yield pulse cannot reach the plasma survival state, which is equivalent to the electrons in the cavity being "cooled down", and then it is necessary to re-ignite, which is bound to increase the electron load of the anode; if it is less than this 94% time interval, the 13MHz high-frequency low-power pulse time given to maintain the plasma survival state is lengthened, and the electron load of 13MHz under the same power is larger than that of 2MHz, which is not conducive to reducing the electron load of the anode. Therefore, the 13MHz high-frequency low-power pulse time given by the dual-frequency driving device should be as short as possible. The reason for choosing the 94% time interval is to utilize the characteristics of low-frequency high-power pulses (high-yield pulses) that there will be residual electrons. When the low-frequency high-power pulse changes from high to low, although the power is not applied, the electron density still exists, that is, the residual electrons generated by the low-frequency high-power pulse still exist. This residual electron can also play the role of maintaining the plasma state. By fully utilizing the role of the residual electrons, the pulse width of the maintenance pulse is minimized to the maximum extent, and the amplitude of the maintenance pulse is minimized. Since the amplitude of the maintenance pulse is the lowest and the pulse width only accounts for 5% of the high-yield pulse repetition period, the electron load of the anode is greatly reduced.

[0033] 2. The difference between the present invention and the prior art: There are two conventional methods. The first is constant output power rather than pulse output power. Since constant output takes longer than pulse output, electrons will be generated when there is power, and there will be an electron load at the pole. Therefore, the method with constant output power generates the most electron load at the pole. The second is pulse output power. Even if it is not constant output power but pulse power, it is 1% low-frequency high-power pulses and 99% high-frequency low-power pulses. 99% of the high-frequency low-power pulses cover the entire time axis. Since the high-frequency low-power pulses are high-frequency pulses (13MHz), the electron load generated is larger than that of the low-frequency 2MHz pulses with low frequency and high power. Therefore, both conventional methods will generate more electrons at the pole. The difference between the present invention and the conventional method is that 99% of the high-frequency low-power pulse area on the time axis is discretized, and the high-frequency low-power pulses only cover a part of the time axis, and there are no pulses on 94% of the time axis.

[0034] 3. Difficulties in design of the present invention:

[0035] One of the difficulties is how to choose a suitable delay time or a suitable time interval for the high-frequency, low-power pulse. If this time interval is selected to be too short, it will not only cause power waste but also affect the reduction of the electron load of the cathode. If this time interval is selected to be too long, the residual electrons are not enough, or the electron density is not enough to meet the electron density requirements for maintaining the plasma state, then it is necessary to cold-start ignition again, and the power of the cold-start ignition again is bound to increase the electron load of the cathode.

[0036] The second difficulty is how to ensure the consistency of high-frequency low-power pulses and low-frequency high-power pulses. The consistency of the steps is that there is no pulse in the 94% high-power pulse repetition period before the arrival of the sustaining pulse, the rising edge of the sustaining pulse is started after the 94% high-power pulse repetition period, and the rising edge of the high-yield pulse is started at the same time as the falling edge of the sustaining pulse arrives.

[0037] 4. The solution of the present invention:

[0038] Solution to one of the difficulties: The present invention selects a 94% time interval or delay time. The electron density of the residual electrons in this time interval can just meet the electron density requirement for maintaining the plasma state, so that there is no need to re-ignite the next time a low-frequency high-power pulse is emitted. Only one ignition is required during the entire working period, and the pulse that maintains the plasma state also has the lowest amplitude and the pulse width only accounts for 5% of the high-yield pulse repetition period. This proves that the selection of this 94% time interval brings unexpected outstanding effects.

[0039] Solution to the second difficulty: A method for reducing the electron load of the high-frequency pulse negative hydrogen ion source is based on the dual-frequency driving device of the present invention. Figure 6 As shown, the dual-frequency driving device of the present invention sets the dual-frequency frequency, amplitude and delay characteristics in the dual-frequency signal to be amplified (RFOUT40 and RFOUT41), wherein the role of the delay characteristic is to adjust the early and late arrival of the pulse, the early means the delay time is short or 0, and the late means the delay time is long, thereby ensuring that the high-frequency low-power pulse and the low-frequency high-power pulse are in step with each other.

[0040] 5. 94% of the delay time is exchanged for a reduction of tens to dozens of times of the electronic load of the anode

[0041] Electrons and negative hydrogen ions are associated with each other. Under the same power, the higher the frequency, the higher the ratio of electrons to negative hydrogen ions. In ionic substances, electrons are usually ten to dozens of times more than negative hydrogen ions. The present invention reduces the time of 13.56MHz power to maintain the plasma state from 99% to less than 5%, so the electronic load is reduced by more than ten times. If the power to maintain the plasma is replaced by the power for repeated ignition, since the power amplitude to maintain the plasma is lower than the amplitude of the ignition power, the electronic load will be further reduced on the basis of the reduction of the electronic load by more than ten times because the time of 13.56MHz ignition power is reduced.

[0042] 6. Design principle of the dual-frequency driving device of the present invention: A dual-frequency driving device for a pulse high-frequency ionization device such as Figure 5-6 As shown, the dual-frequency driving device is used to provide a dual-frequency signal to be amplified for the low-power high-frequency power source and the high-power high-frequency power source of the third party. The low-power high-frequency power source of the third party generates high-frequency low power for load cold start ignition and load maintenance of plasma state, and feeds the high-frequency low-power pulse to the load (the high-frequency antenna in the negative hydrogen ion source and the plasma material generated by the antenna drive, the plasma material includes electrons and negative hydrogen ions, etc.) through the third-party impedance matching device (adjustable dual-frequency vector impedance matching device), ionizes and generates plasma material in the cold start ignition state, and ionizes and generates plasma material to maintain the plasma state; the high-power high-frequency power source of the third party generates low-frequency high power for high-yield plasma, and feeds the low-frequency high-power pulse to the load through the third-party impedance matching device, ionizes and generates a large amount of plasma material that can be drawn out;

[0043] The dual-frequency signal to be amplified has inherent dual-frequency frequency, amplitude and delay characteristics; the dual-frequency driving device is provided with: Figure 6 As shown, a dual-frequency signal controller (10), a dual-frequency sine / cosine digital waveform generator (20), a high-frequency high-frequency digital carrier modulation path (30) and a low-frequency high-frequency digital carrier modulation path (31), and a dual high-frequency digital-to-analog conversion output drive module (40);

[0044] The dual-frequency signal controller (10) is used to generate a dual-frequency frequency control signal and a dual-frequency amplitude control signal with an intrinsic dual-frequency delay control characteristic, and send the dual-frequency frequency control signal to a dual-frequency sine / cosine digital waveform generator (20), and send the dual-frequency amplitude control signal with an intrinsic delay characteristic to a high-frequency high-frequency digital carrier modulation path (30) and a low-frequency high-frequency digital carrier modulation path (31).

[0045] The dual-frequency sine / cosine digital waveform generator (20) is used to convert the received dual-frequency frequency control signal into a sine / cosine signal and send it to a high-frequency high-frequency digital carrier modulation path (30) and a low-frequency high-frequency digital carrier modulation path (31) respectively;

[0046] The high-frequency and high-frequency digital carrier modulation path (30) is used to multiply the received sine / cosine signal by the received dual-frequency amplitude control signal with an intrinsic dual-frequency delay control characteristic, thereby realizing modulation of the high-frequency and high-frequency digital carrier signal;

[0047] The low-frequency and high-frequency digital carrier modulation path (31) is used to multiply the received sine / cosine signal by the received dual-frequency amplitude control signal with an intrinsic dual-frequency delay control characteristic, thereby realizing modulation of the low-frequency and high-frequency digital carrier signal;

[0048] The dual high-frequency digital-analog conversion output drive module (40) is used to perform digital-analog conversion on a modulated high-frequency high-frequency digital carrier signal and a modulated low-frequency high-frequency digital carrier signal, and send the continuously output high-frequency drive signal after digital-analog conversion to a third-party low-power high-frequency power source; send the pulse output high-frequency drive signal after digital-analog conversion to a third-party low-power high-frequency power source; send the pulse output low-frequency drive signal after digital-analog conversion to a third-party high-power high-frequency power source;

[0049] The frequency signal sent by the dual-frequency signal controller (10) to the dual-frequency sine / cosine digital waveform generator (20) and the dual-frequency amplitude control signal with an intrinsic dual-frequency delay control feature sent to the high-frequency and high-frequency digital carrier modulation path (30) and the low-frequency and high-frequency digital carrier modulation path (31) are both digital signals with a certain bit width;

[0050] The sine / cosine signals sent by the dual-frequency sine / cosine digital waveform generator (20) to the high-frequency and high-frequency digital carrier modulation path (30) and to the low-frequency and high-frequency digital carrier modulation path (31) are both digital signals with a certain bit width;

[0051] The modulated signal sent by the high-frequency high-frequency digital carrier modulation path (30) to the dual high-frequency digital-analog conversion output drive module (40) and the modulated signal sent by the low-frequency high-frequency digital carrier modulation path (31) to the dual high-frequency digital-analog conversion output drive module (40) are both digital signals with a certain bit width;

[0052] The digital signal with a certain bit width means that the bit width cannot be too wide or too narrow. The bit width cannot be too wide means that the memory resources and register resources are occupied as little as possible under the premise of meeting the design requirements. The bit width cannot be too narrow means that the signal strength cannot be reduced in order to save memory resources and register resources. This is a basic design requirement.

[0053] The continuously output high-frequency driving signal contains frequency and amplitude characteristics for a cold start state;

[0054] The high-frequency driving signal output by the pulse contains frequency, amplitude and time delay characteristics for maintaining the plasma state;

[0055] The low-frequency driving signal of the pulse output contains frequency, amplitude and time delay characteristics for generating high-yield plasma pulses.

[0056] The frequency signal sent by the dual-frequency signal controller (10) to the dual-frequency sine / cosine digital waveform generator (20) is a digital signal with a certain bit width, and the frequency signal is: a high-frequency high-frequency control signal (FREQ10) and a low-frequency high-frequency control signal (FREQ11); the digital signal with a certain bit width means that: their bit width distribution should be higher than:

[0057] FREQ10 bit width lower limit = [log2 (DWAV20 frequency ÷ DWAV20 frequency tolerance)] (1);

[0058] FREQ11 bit width lower limit = [log2 (DWAV21 frequency ÷ DWAV21 frequency tolerance)] (2).

[0059] For the digital high-frequency and high-frequency sine / cosine waveform signal (DWAV20) frequency fDWAV20 to be set and the digital clock frequency fclk required for the operation of the dual-frequency sine / cosine digital waveform generator (20), the high-frequency and high-frequency frequency control signal (FREQ10) should satisfy:

[0060] FREQ10 = [fDWAV20 ÷ fclk × 2^FREQ10 bit width] (3);

[0061] Similarly, for the digital low-frequency high-frequency sine / cosine waveform signal (DWAV21) frequency fDWAV21 to be set, the low-frequency high-frequency frequency control signal (FREQ11) should satisfy:

[0062] FREQ11=[fDWAV21÷fclk×2^FREQ11 bit width] (4);

[0063] The FREQ10 bit width of the above formula (3) and the FREQ11 bit width of the above formula (4) are bit widths determined according to the FREQ10 bit width lower limit of the above formula (1) and the FREQ11 bit width lower limit of the above formula (2).

[0064] The amplitude signals sent by the dual-frequency signal controller (10) to the high-frequency and high-frequency digital carrier modulation path (30) and the low-frequency and high-frequency digital carrier modulation path (31) are both digital signals with a certain bit width. The amplitude signals are: a high-frequency and high-frequency path modulation signal (AMPL12) and a low-frequency and high-frequency path modulation signal (AMPL13). The digital signals with a certain bit width refer to that their bit widths should be higher than:

[0065] AMPL12 bit width lower limit = [log2(AMPL12 amplitude ÷AMPL12 amplitude tolerance)] (5);

[0066] AMPL13 bit width lower limit = [log2 (AMPL13 amplitude ÷ AMPL13 amplitude tolerance)] (6).

[0067] The modulated signal sent by the high-frequency and high-frequency digital carrier modulation path (30) to the dual-high-frequency digital-to-analog conversion output driving module (40) and the modulated signal sent by the low-frequency and high-frequency digital carrier modulation path (31) to the dual-high-frequency digital-to-analog conversion output driving module (40) are both digital signals with a certain bit width; the modulated signals are digital high-frequency and high-frequency modulated signals (DMOD30) and digital low-frequency and high-frequency modulated signals (DMOD31), and the digital signals with a certain bit width refer to digital signals whose bit widths satisfy:

[0068] DMOD30 bit width = DWAV20 bit width + AMPL12 bit width (7);

[0069] DMOD31 bit width = DWAV21 bit width + AMPL13 bit width (8);

[0070] The AMPL12 bit width of the above formula (7) and the AMPL13 bit width of the above formula (8) are bit widths determined according to the lower limit of the AMPL12 bit width of the above formula (5) and the lower limit of the AMPL13 bit width of the above formula (6).

[0071] Based on the above principle, the present invention designs a method for reducing the electron load of the high-frequency pulse negative hydrogen ion source. Figure 1-4 , Figure 7As shown, the method is based on a dual-frequency driving device, which provides a dual-frequency driving signal to be amplified for a third-party power amplifier, and after passing through the third-party power amplifier, generates a high-frequency medium power for a cold start state, a high-frequency low power for maintaining a plasma existence state, and a low-frequency high power for generating a large amount of plasma; the dual-frequency driving signal includes a continuously output high-frequency driving signal, and the continuously output high-frequency driving signal contains the frequency and amplitude characteristics for the cold start state; the dual-frequency driving signal includes a pulse output high-frequency driving signal, and the pulse output high-frequency driving signal contains the frequency, amplitude, and delay characteristics for maintaining a plasma existence state; the dual-frequency driving signal includes a pulse output low-frequency driving signal, and the pulse output low-frequency driving signal contains the frequency, amplitude, and delay characteristics for generating high-yield plasma pulses; its characteristic is that the method includes the following steps:

[0072] Step 1, cold start state: ignite the plasma with the high frequency medium power of the continuously output high frequency driving signal, then use the dual frequency driving device to add a delay to the high frequency low power pulse outputted by the subsequent pulse, the delay time makes the amplitude of the subsequent high frequency low power pulse for maintaining the plasma state to be the lowest, and the pulse width only accounts for a few percent of the repetition period of the low frequency high power pulse for producing plasma with large output, at this time, the anode power supply is not powered; the high frequency medium power pulse is also called a cold start pulse;

[0073] Step 2, maintaining the plasma state: using the high frequency and low power of the high frequency driving signal output by the pulse to maintain the plasma state, and limiting the high frequency and low power pulse to a pulse with a pulse width that is only a few percent of the repetition period of the low frequency and high power pulse and with the lowest amplitude; while starting the high frequency and low power pulse, using a dual frequency driving device to add a delay to the low frequency and high power pulse, the delay time is the repetition period of the low frequency and high power pulse minus the sum of the pulse widths of the low frequency and high power pulse and the high frequency and low power pulse; at this time, the anode power supply of the high frequency pulse negative hydrogen ion source is powered on when a DC high voltage power supply is used, and is not powered on when a pulse high voltage power supply is used; the high frequency and low power pulse is also called a maintaining pulse;

[0074] Step 3, mass production of plasma state: use the low-frequency and high-power of the low-frequency driving signal of the pulse output to generate a large amount of plasma, and limit the pulse to a pulse with the narrowest pulse width and the highest amplitude, and then use the dual-frequency driving device to continue to delay the high-frequency and low-power pulse output for maintaining the plasma state; the delay time makes the subsequent high-frequency and low-power pulses that continue to maintain the plasma state have the lowest amplitude, and the pulse width only accounts for a few percent of the repetition period of the low-frequency and high-power pulses for mass production of plasma; and make the anode power supply output at the set high voltage at full power; the low-frequency and high-power pulses are also called high-yield pulses;

[0075] Step 4: Check whether the current high-frequency pulse negative hydrogen ion source has finished working. If yes, then end. If not, return to step 2.

[0076] Furthermore, the high-frequency low-power pulse width used to maintain the plasma in the step 2 is less than 5% of the repetition period of the low-frequency high-power pulse.

[0077] Furthermore, when the low-frequency high-power pulse width accounts for 1% of the low-frequency high-power pulse repetition period and the high-frequency low-power pulse width accounts for less than 5% of the low-frequency high-power pulse repetition period, the delay duration accounts for 94% of the low-frequency high-power pulse repetition period.

[0078] Furthermore, the pulse width of the low-frequency, high-power pulses used for mass production of plasma in step three is determined according to user needs.

[0079] Furthermore, the duration of delaying the low-frequency high-power pulse in step 2 is the pulse width of the high-frequency low-power pulse, that is, the falling edge of the high-frequency low-power pulse is the rising edge of the low-frequency high-power pulse.

[0080] Furthermore, the high frequency medium power in step one is 13 MHz and 300 W.

[0081] Furthermore, the high frequency and low power of step 2 is 13 MHz and 100 W.

[0082] Furthermore, the low frequency and high power of step three is 2 MHz and 80 kW.

[0083] Furthermore, the cold start pulse width of step one is greater than the sum of the sustaining pulse width and the high-yield pulse width: this width is required to ensure that the plasma is ignited, obtain the optimal electron and plasma density in the discharge chamber, and enable the system to reach thermal stability conditions under working conditions.

[0084] It should be emphasized that the above specific embodiments are merely explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without any creative contribution as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for reducing the electron load of a high-frequency pulsed negative hydrogen ion source, the method is based on a dual-frequency driving device, the dual-frequency driving device provides a dual-frequency driving signal to be amplified for a third-party power amplifier, and after passing through the third-party power amplifier, generates a high-frequency medium power for a cold start state, a high-frequency low power for maintaining a plasma state, and a low-frequency high power for generating a large amount of plasma; the dual-frequency driving signal includes a continuously output high-frequency driving signal, and the continuously output high-frequency driving signal contains the frequency and amplitude characteristics for the cold start state; the dual-frequency driving signal includes a pulsed high-frequency driving signal, and the pulsed high-frequency driving signal contains the frequency, amplitude, and time delay characteristics for maintaining a plasma state; the dual-frequency driving signal includes a pulsed low-frequency driving signal, and the pulsed low-frequency driving signal contains the frequency, amplitude, and time delay characteristics for generating high-yield plasma pulses; characterized in that The method comprises the following steps: Step 1, cold start state: ignite the plasma with the high frequency medium power of the continuously output high frequency driving signal, then use the dual frequency driving device to add a delay to the high frequency low power pulse outputted by the subsequent pulse, the delay time makes the amplitude of the subsequent high frequency low power pulse for maintaining the plasma state to be the lowest, and the pulse width only accounts for a few percent of the repetition period of the low frequency high power pulse for producing plasma with large output, at this time, the anode power supply is not powered; the high frequency medium power pulse is also called a cold start pulse; Step 2, maintaining the plasma state: using the high frequency and low power of the high frequency driving signal output by the pulse to maintain the plasma state, and limiting the high frequency and low power pulse to a pulse with a pulse width that is only a few percent of the repetition period of the low frequency and high power pulse and with the lowest amplitude; while starting the high frequency and low power pulse, using a dual frequency driving device to add a delay to the low frequency and high power pulse, the delay time is the repetition period of the low frequency and high power pulse minus the sum of the pulse widths of the low frequency and high power pulse and the high frequency and low power pulse; at this time, the anode power supply of the high frequency pulse negative hydrogen ion source is powered on when a DC high voltage power supply is used, and is not powered on when a pulse high voltage power supply is used; the high frequency and low power pulse is also called a maintaining pulse; Step 3, mass production of plasma state: use the low-frequency and high-power of the low-frequency driving signal of the pulse output to generate a large amount of plasma, and limit the pulse to a pulse with the narrowest pulse width and the highest amplitude, and then use the dual-frequency driving device to continue to delay the high-frequency and low-power pulse output for maintaining the plasma state; the delay time makes the subsequent high-frequency and low-power pulses that continue to maintain the plasma state have the lowest amplitude, and the pulse width only accounts for a few percent of the repetition period of the low-frequency and high-power pulses for mass production of plasma; and make the anode power supply output at the set high voltage at full power; the low-frequency and high-power pulses are also called high-yield pulses; Step 4: Check whether the current high-frequency pulse negative hydrogen ion source has finished working. If yes, then end. If not, return to step 2.

2. The method for reducing the electron load of the high-frequency pulse negative hydrogen ion source according to claim 1, characterized in that: The high-frequency low-power pulse width used to maintain the plasma in the step 2 is less than 5% of the repetition period of the low-frequency high-power pulse.

3. A method for reducing the electron load of a high-frequency pulsed negative hydrogen ion source according to claim 2, characterized in that: When the low frequency high power pulse width accounts for 1% of the low frequency high power pulse repetition period and the high frequency low power pulse width accounts for less than 5% of the low frequency high power pulse repetition period, the delay duration accounts for 94% of the low frequency high power pulse repetition period.

4. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The pulse width of the low-frequency, high-power pulse used for mass production of plasma in step three is determined according to user requirements.

5. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The duration of delaying the low-frequency high-power pulse in step 2 is the pulse width of the high-frequency low-power pulse, that is, the falling edge of the high-frequency low-power pulse is the rising edge of the low-frequency high-power pulse.

6. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The high frequency medium power in step 1 is 13 MHz and 300 W.

7. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The high frequency and low power of step 2 is 13 MHz and 100 W.

8. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The low frequency and high power of step three is 2 MHz and 80 kW.

9. The method for reducing the electron load of the high-frequency pulsed negative hydrogen ion source according to claim 1, characterized in that: The cold start pulse width of step one is greater than the sum of the sustain pulse width and the high-yield pulse width: this width is required to ensure that the plasma is ignited, obtain the optimal electron and plasma density in the discharge chamber, and enable the system to reach thermal stability conditions under the working state.

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