Method for reducing anode electron load of high frequency pulsed negative hydrogen ion source

Abstract

The application discloses a method for reducing the electron load of a high-frequency pulsed negative hydrogen ion source anode, which comprises the following steps: igniting plasma by using a high-frequency medium-power pulse of a continuously output high-frequency driving signal, adding a time delay to a high-frequency low-power pulse by using a double-frequency driving device, and the time delay is such that the amplitude of the pulse for maintaining the plasma state is the lowest and the pulse width only accounts for a few percent of the high-output pulse repetition period; maintaining the plasma state: maintaining the plasma survival state by using a high-frequency low-power pulse of a pulsed output high-frequency driving signal, and limiting the high-frequency low-power pulse to a pulse with a medium pulse width and the lowest amplitude; and generating a large amount of plasma by using a low-frequency high-power pulse of a pulsed output low-frequency driving signal, and limiting the pulse to a pulse with the narrowest pulse width and the highest amplitude. The application reduces the electron load of the negative hydrogen ion source anode by selecting a proper duty cycle for the high-power pulse gap.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of negative hydrogen ion source, and particularly relates to a method for reducing the electron load of an anode of a high-frequency pulsed negative hydrogen ion source. BACKGROUND

[0002] High-current pulsed negative hydrogen ion sources are widely used in particle accelerators, semiconductor processes and controlled nuclear fusion research. Among them, the pulsed negative hydrogen ion source driven by high-frequency power has longer maintenance intervals, and the pulse modulation is more direct and convenient, so it is favored by the relevant field.

[0003] However, the ionization and extraction process in the high-frequency pulsed negative hydrogen ion source is accompanied by a large amount of electrons, which will be extracted together with the negative hydrogen ion beam and form an electron load on the anode that may reach or exceed tens of times or even hundreds of times of the negative hydrogen ion beam, which puts extremely high requirements on the pulse load capacity of the anode power supply and the heat dissipation of the anode itself; in addition, the transient temperature rise effect of the anode electron load may demagnetize the embedded permanent magnet, so that the negative hydrogen ion source cannot normally distinguish the extracted ion beam and the symbiotic electrons.

[0004] A common method for reducing the load of the anode of the negative hydrogen ion source in the prior art is to add alkali metal vapor (such as cesium vapor) in the shop environment. The problems of this method are: it works for both pulsed and direct current negative hydrogen ion sources, but it pollutes the discharge environment and also inevitably pollutes the subsequent process environment; at the same time, the structure of the cesium furnace system itself is relatively complex, increasing the cost and difficulty of maintenance, and when used in a high-frequency driven pulsed negative hydrogen ion source, it may not be able to take advantage of the longer maintenance interval; in addition, for a high-frequency pulsed negative hydrogen ion source driven by an internal antenna, the attachment of cesium vapor or other alkali metal vapor on the internal antenna will gradually reduce the efficiency of high-frequency power feeding, and eventually make the antenna ineffective; in addition, the alkali metal vapor also increases the probability of high-voltage sparking of the equipment, which is not conducive to the stability and safety of the system as a whole. SUMMARY

[0005] The present application is directed to the deficiencies of the prior art, and proposes a method for reducing the electron load of the anode of a high-frequency pulsed negative hydrogen ion source, which aims to solve the problem that the ionization and extraction process in the existing high-frequency pulsed negative hydrogen ion source is accompanied by a large amount of electrons, which will be extracted together with the negative hydrogen ion beam and form an electron load on the anode that may reach or exceed tens of times or even hundreds of times of the negative hydrogen ion beam, which puts extremely high requirements on the pulse load capacity of the anode power supply and the heat dissipation of the anode itself; the transient temperature rise effect of the anode electron load may demagnetize the embedded permanent magnet, so that the negative hydrogen ion source cannot normally distinguish the extracted ion beam and the symbiotic electrons.

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

[0007] A method for reducing the anode electron load of a high-frequency pulsed negative hydrogen ion source, which is based on a dual-frequency driving device that provides a dual-frequency driving signal to be amplified to 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 survival 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 containing frequency and amplitude characteristics for the cold start state; the dual-frequency driving signal includes a pulsed output high-frequency driving signal containing frequency, amplitude, and time delay characteristics for maintaining the plasma survival state; and the dual-frequency driving signal includes a pulsed output low-frequency driving signal containing frequency, amplitude, and time delay characteristics for generating a high-yield plasma pulse; the method comprises the following steps:

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

[0009] Step two, maintaining the plasma state: maintain the plasma survival state with a pulsed output high-frequency driving signal at a high-frequency low power, and limit the high-frequency low power pulse to a pulse width that only accounts for a few percent of the low-frequency high power pulse repetition period and a minimum amplitude; at the same time as starting the high-frequency low power pulse, add a time delay to the low-frequency high power pulse with the dual-frequency driving device, the time delay duration is the repetition period of the low-frequency high power pulse minus the sum of the pulse widths of the low-frequency high power pulse and the high-frequency low power pulse; at this time, the anode power supply of the high-frequency pulsed negative hydrogen ion source is powered on when using a direct-current high-voltage power supply, and is not powered on when using a pulsed high-voltage power supply; the high-frequency low power pulse is also called a maintenance pulse;

[0010] Step three, mass production of plasma state: a low-frequency high-power mass production of plasma is produced by a low-frequency driving signal of pulse output, and the pulse is limited to a pulse with the narrowest pulse width and the highest amplitude, then, a high-frequency low-power pulse output of the double-frequency driving device for maintaining the survival state of the plasma is added with a delay; the delay time makes the amplitude of the subsequent high-frequency low-power pulse for maintaining the plasma state the lowest, and the pulse width only accounts for a few percent of the low-frequency high-power pulse repetition period of the mass production of plasma; and the anode power supply outputs at full power according to the set high voltage; the low-frequency high-power pulse is also called a high-yield pulse;

[0011] Step four, whether the current high-frequency pulse negative hydrogen ion source is completed, if yes, end, if not, return to step two.

[0012] Further, the high-frequency low-power pulse width for maintaining the survival state of the plasma in step two accounts for less than 5% of the low-frequency high-power pulse repetition period.

[0013] Further, 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 time accounts for 94% of the low-frequency high-power pulse repetition period.

[0014] Further, the pulse width of the low-frequency high-power pulse for mass production of plasma in step three is determined according to the user's demand.

[0015] Further, the delay time of the low-frequency high-power pulse in step two is the pulse width of the high-frequency low-power, that is, the falling edge of the high-frequency low-power pulse is the rising edge of the low-frequency high-power pulse.

[0016] Further, the high-frequency medium power in step one is a power of 13MHz, 300W.

[0017] Further, the high-frequency low power in step two is a power of 13MHz, 100W.

[0018] Further, the low-frequency high power in step three is a power of 2MHz, 80kW.

[0019] Further, the cold start pulse width in step one is greater than the sum of the widths of the maintenance pulse and the high-yield pulse: the width not only ensures that the plasma is ignited, but also obtains the preferred electron and plasma density in the discharge cavity, and enables the system to reach the thermal stability condition in the working state.

[0020] Advantages and effects of the present application

[0021] 1. The application ingeniously utilizes the characteristic that high-power pulses still have residual electrons without power supply, and by selecting a suitable duty cycle (94% duty cycle) for the high-power pulse gap, the pulse that maintains the plasma survival state not only has a pulse width of only 5% of the high-power pulse gap, but also has a minimum pulse amplitude, thereby reducing the electron load of the negative hydrogen ion source anode.

[0022] 2. The application reduces the time of the 13.56MHz power that maintains the plasma survival state from the original 99% to below 5%, thus reducing the electron load by more than ten times; if the power that maintains the plasma is replaced by the power that repeatedly ignites, since the amplitude of the power that maintains the plasma is lower than the amplitude of the ignition power, the time of the 13.56MHz ignition power is also reduced, further reducing the electron load on the basis of reducing the electron load by more than ten times. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A schematic diagram of the pulse width and time interval of the three pulses of the negative hydrogen ion source of the application;

[0024] Figure 2 A schematic diagram of the frequency and time interval of the three pulses of the negative hydrogen ion source of the application;

[0025] Figure 3 An effect diagram of reducing the electron load of the anode of the negative hydrogen ion source of the application;

[0026] Figure 4 A flowchart of the method for reducing the electron load of the anode of the high-frequency pulse negative hydrogen ion source of the application;

[0027] Figure 5 An application effect diagram of the dual-frequency driving device of the application;

[0028] Figure 6 A structure diagram of the dual-frequency driving device for the pulse high-frequency ionization device of the application;

[0029] Figure 7 A schematic diagram of the electron load of the negative hydrogen ion source anode. DETAILED DESCRIPTION

[0030] Design principle of the application

[0031] 1. The innovation of the present application: The innovation is that a suitable time interval (delay duration) is selected for the high-frequency low-power pulse, which can maximize the reduction of anode electron load, and at the same time, when the next low-frequency high-power pulse arrives, the plasma state is more stable. The time interval accounts for 94% of the entire high-yield pulse (low-frequency high-power pulse) repetition period. If the time interval is greater than 94%, the residual electron density generated by the high-yield pulse cannot reach the plasma survival state, which means that the electrons in the cavity are "cooled", and re-ignition is required, which inevitably increases the anode electron load. If the time interval is less than 94%, the time of the 13MHz high-frequency low-power pulse for maintaining the plasma survival state is lengthened, and the 13MHz electron load is larger than the 2MHz electron load under the same power, which is not conducive to reducing the anode electron load. Therefore, the time of the 13MHz high-frequency low-power pulse given by the dual-frequency driving device should be as short as possible. The reason for selecting a time interval of 94% is to take advantage of the characteristic that the low-frequency high-power pulse (high-yield pulse) has residual electrons. When the low-frequency high-power pulse decreases from high to low, although the power is not added, the electron density still exists, that is, the residual electrons generated by the low-frequency high-power pulse still exist, and this residual electron can also play a role in maintaining the plasma survival state. Due to the full use of the role of residual electrons, the pulse width of the maintenance pulse is minimized, and the amplitude of the maintenance pulse is also minimized. Due to the minimum amplitude and the pulse width accounting for only 5% of the high-yield pulse repetition period, the anode electron load is greatly reduced.

[0032] 2. The difference between the present application and the prior art: There are two conventional methods, the first one is constant output power instead of pulse output power. Since the constant output time is longer than the pulse output time, there will be electron generation with power, and there will be anode electron load with electron generation. Therefore, the method of constant output power has the most anode electron load. The second one is pulse output power. Even if it is not constant output power but pulse power, it is still 1% low-frequency high-power pulse and 99% high-frequency low-power pulse. The 99% high-frequency low-power pulse covers the entire time axis. Since the high-frequency low-power pulse is a high-frequency pulse (13MHz), the anode electron load generated by the low-frequency high-power pulse is larger. Therefore, both conventional methods will generate more anode electrons. The difference between the present application and the conventional method is that the 99% high-frequency low-power pulse area on the time axis is discretized, and the high-frequency low-power pulse only covers a part of the time axis, and there is no pulse on 94% of the time axis.

[0033] 3. Design difficulty of the present application:

[0034] One of the difficulties is how to select a suitable delay time or suitable time interval for the high-frequency low-power pulse, if the time interval is too small, not only the power is wasted, but also the anode electron load is reduced; if the time interval is too large, the residual electrons are not enough, or the electron density is not enough, which cannot meet the requirement of electron density for maintaining the plasma survival state, and the power of cold start ignition is increased again, which increases the anode electron load.

[0035] The second difficulty is how to ensure the consistency of the high-frequency low-power pulse and the low-frequency high-power pulse. The consistency of the pace is that there is no pulse in the 94% high-power pulse repetition period before the maintenance pulse arrives, the rising edge of the maintenance pulse is started after the 94% high-power pulse repetition period, and the rising edge of the large yield pulse is started at the same time as the falling edge of the maintenance pulse arrives.

[0036] 4. The solution of the present application:

[0037] The solution to the first difficulty is that the present application selects a 94% time interval or delay time, and the electron density of the residual electrons in the time interval can meet the requirement of electron density for maintaining the plasma survival state, so that the next low-frequency high-power pulse does not need to be ignited again, and only needs to be ignited once during the whole working period, and the maintenance pulse for maintaining the plasma survival state has the lowest amplitude and the pulse width only accounts for 5% of the high yield pulse repetition period. Therefore, the selection of the 94% time interval brings unexpected outstanding effects.

[0038] The solution to the second difficulty is that the present application is a method for reducing the anode electron load of a high-frequency pulse negative hydrogen ion source, which is based on the double-frequency driving device of the present application as shown in Figure 6 The double-frequency driving device of the present application is provided with double-frequency frequency, amplitude and time delay characteristics in the double-frequency signal (RFOUT40 and RFOUT41) to be amplified, wherein the time delay characteristics adjust the early and late arrival of the pulse, the early is short time delay or 0, and the late is long time delay, so as to ensure the consistency of the high-frequency low-power pulse and the low-frequency high-power pulse.

[0039] 5. The 94% delay time length reduces the anode electron load by dozens of times to dozens of times

[0040] Electrons and negative hydrogen ions are co-occurring. At the same power, the higher the frequency, the higher the ratio of electrons to negative hydrogen ions. In plasma materials, electrons are usually ten to several tens of times more numerous than negative hydrogen ions. This invention reduces the time of the 13.56MHz power required to maintain the plasma state from 99% to less than 5%, thus reducing the electron load by more than ten times. If the power required to maintain the plasma is replaced by the power required for repeated ignition, since the amplitude of the power required to maintain the plasma is lower than that of the ignition power, the reduction in the time of the 13.56MHz ignition power will further reduce the electron load on top of the reduction of more than ten times.

[0041] 6. Design principle of the dual-frequency drive device of the present invention: A dual-frequency drive device for a pulse high-frequency ionization device, such as... Figures 5-6 As shown, the dual-frequency drive device is used to provide amplified dual-frequency signals to a third-party low-power high-frequency power source and a high-power high-frequency power source. The third-party low-power high-frequency power source generates high-frequency low-power signals for cold start ignition of the load and for maintaining the plasma state of the load. The high-frequency low-power pulse is fed into the load (high-frequency antenna in the negative hydrogen ion source and plasma material generated by the antenna, including electrons and negative hydrogen ions, etc.) through a third-party impedance matching device (adjustable dual-frequency vector impedance matching device). This ionizes the plasma material in the cold start ignition state and the plasma material for maintaining the plasma state. The third-party high-power high-frequency power source generates low-frequency high-power signals for high-yield plasma. The high-frequency high-power pulse is fed into the load through the third-party impedance matching device. This ionizes the plasma material that can be extracted.

[0042] The dual-frequency signal to be amplified inherently possesses dual-frequency, amplitude, and time-delay characteristics; the dual-frequency drive device is provided sequentially from one side to the other as follows: Figure 6 As shown, the dual-frequency signal controller (10), dual-frequency sine / cosine digital waveform generator (20), high-frequency high-frequency digital carrier modulation path (30) and low-frequency high-frequency digital carrier modulation path (31), and dual high-frequency digital-to-analog converter output drive module (40) are included.

[0043] The dual-frequency signal controller (10) is used to generate dual-frequency frequency control signals and dual-frequency amplitude control signals with intrinsic dual-frequency time delay control characteristics, and sends the dual-frequency frequency control signals to the dual-frequency sine / cosine digital waveform generator (20), and sends the dual-frequency amplitude control signals with intrinsic time delay characteristics to the high-frequency high-frequency digital carrier modulation path (30) and the low-frequency high-frequency digital carrier modulation path (31), respectively.

[0044] The dual-frequency cosine digital waveform generator (20) is used to convert the received dual-frequency frequency control signal into a cosine signal and send it to the high-frequency high-frequency digital carrier modulation path (30) and the low-frequency high-frequency digital carrier modulation path (31) respectively;

[0045] The high-frequency high-frequency digital carrier modulation path (30) is used to multiply the received cosine signal by the received dual-frequency amplitude control signal of the intrinsic dual-frequency time delay control feature, thereby realizing modulation of the high-frequency high-frequency digital carrier signal;

[0046] The low-frequency high-frequency digital carrier modulation path (31) is used to multiply the received cosine signal by the received dual-frequency amplitude control signal of the intrinsic dual-frequency time delay control feature, thereby realizing modulation of the low-frequency high-frequency digital carrier signal;

[0047] The dual high-frequency digital-analog conversion output drive module (40) is used to perform digital-analog conversion on the modulated high-frequency high-frequency digital carrier signal and the modulated low-frequency high-frequency digital carrier signal, and send the continuous output high-frequency drive signal after digital-analog conversion to a third-party low-power high-frequency power source; send the pulsed output high-frequency drive signal after digital-analog conversion to a third-party low-power high-frequency power source; and send the pulsed output low-frequency drive signal after digital-analog conversion to a third-party high-power high-frequency power source;

[0048] The frequency signal sent by the dual-frequency signal controller (10) to the dual-frequency cosine digital waveform generator (20), and the dual-frequency amplitude control signal of the intrinsic dual-frequency time delay control feature sent to the high-frequency high-frequency digital carrier modulation path (30) and the low-frequency high-frequency digital carrier modulation path (31) are all digital signals with a certain bit width;

[0049] The cosine signal sent by the dual-frequency cosine digital waveform generator (20) to the high-frequency high-frequency digital carrier modulation path (30) and the low-frequency high-frequency digital carrier modulation path (31) are all digital signals with a certain bit width;

[0050] 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 all digital signals with a certain bit width;

[0051] 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 basic design requirement of not reducing the signal strength in order to save memory resources and register resources;

[0052] The continuous output high frequency drive signal contains frequency, amplitude characteristics for cold start state;

[0053] The pulse output high frequency drive signal contains frequency, amplitude, time delay characteristics for maintaining plasma sustain state.

[0054] The pulse output low frequency drive signal contains frequency, amplitude, time delay characteristics for high power plasma pulse generation.

[0055] The frequency signal sent by the dual frequency signal controller (10) to the dual frequency cosine digital waveform generator (20) is a digital signal with certain bit width, which is high frequency high frequency control signal (FREQ10) and low frequency high frequency control signal (FREQ11). The digital signal with certain bit width means that the bit width distribution should be higher than:

[0056] FREQ10 bit width lower limit = [log2 (DWAV20 frequency ÷ DWAV20 frequency tolerance)] (1);

[0057] FREQ11 bit width lower limit = [log2 (DWAV21 frequency ÷ DWAV21 frequency tolerance)] (2).

[0058] For the digital high frequency high frequency cosine waveform signal (DWAV20) frequency fDWAV20 to be set and the digital clock frequency fclk required for the operation of the dual frequency cosine digital waveform generator (20), the high frequency high frequency control signal (FREQ10) should satisfy:

[0059] FREQ10 = [fDWAV20 ÷ fclk × 2^FREQ10 bit width] (3);

[0060] Similarly, for the digital low frequency high frequency cosine waveform signal (DWAV21) frequency fDWAV21 to be set, the low frequency high frequency control signal (FREQ11) should satisfy:

[0061] FREQ11 = [fDWAV21 ÷ fclk × 2^FREQ11 bit width] (4);

[0062] The FREQ10 bit width of formula (3) and the FREQ11 bit width of formula (4) are the bit widths determined according to the FREQ10 bit width lower limit of formula (1) and the FREQ11 bit width lower limit of formula (2).

[0063] The amplitude signals sent by the dual-frequency signal controller (10) to the high-frequency high-frequency digital carrier modulation path (30) and the low-frequency high-frequency digital carrier modulation path (31) are digital signals with a certain bit width, and the amplitude signals are high-frequency high-frequency path modulation signals (AMPL12) and low-frequency high-frequency path modulation signals (AMPL13). The digital signals with a certain bit width refer to that their bit widths should be higher than:

[0064] AMPL12 bit width lower limit = [log2(AMPL12 amplitude ÷ AMPL12 amplitude tolerance)] (5);

[0065] AMPL13 bit width lower limit = [log2(AMPL13 amplitude ÷ AMPL13 amplitude tolerance)] (6).

[0066] The modulated signals 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 signals 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 digital signals with a certain bit width; the modulated signals are digital high-frequency high-frequency modulated signals (DMOD30) and digital low-frequency high-frequency modulated signals (DMOD31), and the digital signals with a certain bit width refer to that their bit widths satisfy:

[0067] DMOD30 bit width = DWAV20 bit width + AMPL12 bit width (7);

[0068] DMOD31 bit width = DWAV21 bit width + AMPL13 bit width (8);

[0069] 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 AMPL12 bit width lower limit of the above formula (5) and the AMPL13 bit width lower limit of the above formula (6).

[0070] Based on the above principle, the application designs a method for reducing the anode electron load of a high-frequency pulsed negative hydrogen ion source, as shown in Figures 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 the third-party power amplifier, a high-frequency medium power for a cold start state, a high-frequency low power for maintaining a plasma survival state, and a low-frequency high power for generating a large amount of plasma are generated; the dual-frequency driving signal includes a continuously output high-frequency driving signal, and the continuously output high-frequency driving signal contains 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 frequency, amplitude, and time delay characteristics for maintaining the plasma survival state; the dual-frequency driving signal includes a pulse output low-frequency driving signal, and the pulse output low-frequency driving signal contains frequency, amplitude, and time delay characteristics for generating a high-yield plasma pulse; the method includes the following steps:

[0071] Step one, cold start state: ignite the plasma with a high-frequency medium power of the continuously output high-frequency driving signal, and then add a time delay to the subsequent pulse output high-frequency low power pulse by using the dual-frequency driving device; the time 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 low-frequency high power pulse repetition period; at this time, the anode power supply is not powered on; the high-frequency medium power pulse is also called a cold start pulse;

[0072] Step two, maintaining the plasma state: maintain the plasma survival state with the high-frequency low power of the pulse output high-frequency driving signal, and limit the high-frequency low power pulse to a pulse with a pulse width accounting for a few percent of the low-frequency high power pulse repetition period and a lowest amplitude; start the high-frequency low power pulse, and at the same time, add a time delay to the low-frequency high power pulse by using the dual-frequency driving device; the time delay time is the repetition period of the low-frequency high power pulse minus the sum of the pulse widths of the low-frequency high power pulse and the high-frequency low power pulse; at this time, the anode power supply of the high-frequency pulse negative hydrogen ion source is powered on when a direct current high-voltage power supply is used, and is not powered on when a pulse high-voltage power supply is used; the high-frequency low power pulse is also called a maintenance pulse;

[0073] Step three, large amount of plasma generation state: generate a large amount of plasma with the low-frequency high power of the pulse output low-frequency driving signal, and limit the pulse to a pulse with a narrowest pulse width and a very high amplitude, and then continue to add a time delay to the pulse output high-frequency low power pulse for maintaining the plasma survival state by using the dual-frequency driving device; the time 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 low-frequency high power pulse repetition period; and the anode power supply is fully powered according to the set high-voltage output; the low-frequency high power pulse is also called a high-yield pulse;

[0074] Step four, whether the current high frequency pulse negative hydrogen ion source is finished, if yes, end, if not, return to step two.

[0075] Further, the high frequency low power pulse width of step two is less than 5% of the low frequency high power pulse repetition period.

[0076] Further, when the low frequency high power pulse width is 1% of the low frequency high power pulse repetition period, and the high frequency low power pulse width is less than 5% of the low frequency high power pulse repetition period, the delay time length is 94% of the low frequency high power pulse repetition period.

[0077] Further, the low frequency high power pulse width of step three for large production of plasma is determined according to the user's needs.

[0078] Further, the delay time length of step two for low frequency high power pulse is the pulse width of high frequency low power, that is, the falling edge of the high frequency low power pulse is the rising edge of the low frequency high power pulse.

[0079] Further, the high frequency medium power of step one is a power of 13MHz, 300W.

[0080] Further, the high frequency low power of step two is a power of 13MHz, 100W.

[0081] Further, the low frequency high power of step three is a power of 2MHz, 80kW.

[0082] Further, the cold start pulse width of step one is greater than the sum of the maintenance pulse and the high yield pulse width: the width not only ensures that the plasma is ignited, but also obtains the preferred electron and plasma density in the discharge cavity, and can make the system reach the thermal stability condition in the working state.

[0083] It should be emphasized that the above specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the above embodiments without creative contribution after reading the present specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for reducing the anode electron load of a high frequency pulsed negative hydrogen ion source, based on a dual frequency driving device, which provides a third party power amplifier with a dual frequency driving signal to be amplified, after which a high frequency medium power for a cold start state, a high frequency low power for a plasma sustaining state, and a low frequency high power for a high yield plasma generation are generated; the dual frequency driving signal comprises a continuously output high frequency driving signal, which contains frequency and amplitude characteristics for the cold start state; the dual frequency driving signal comprises a pulsed output high frequency driving signal, which contains frequency, amplitude and time delay characteristics for the plasma sustaining state; the dual frequency driving signal comprises a pulsed output low frequency driving signal, which contains frequency, amplitude and time delay characteristics for the high yield plasma pulse generation; characterized in that, The method comprises the following steps: Step one, cold start state: ignite plasma with high-frequency medium power of continuous output high-frequency driving signal, then add delay to high-frequency low power pulse of subsequent pulse output with double-frequency driving device, the delay time makes the amplitude of subsequent high-frequency low power pulse for maintaining plasma state lowest, and the pulse width only accounts for a few percent of low-frequency high power pulse repetition period for large production of plasma, at this time, the anode power supply is not powered on; the high-frequency medium power pulse is also called cold start pulse; Step two, maintain plasma state: maintain plasma survival state with high-frequency low power of pulse output high-frequency driving signal, and limit the high-frequency low power pulse to a pulse with a pulse width accounting for a few percent of low-frequency high power pulse repetition period and a lowest amplitude; start the high-frequency low power pulse, and add delay to low-frequency high power pulse with double-frequency driving device at the same time, the delay time is the repetition period of low-frequency high power pulse minus the sum of the pulse width of low-frequency high power pulse and high-frequency low power pulse; at this time, the anode power supply of high-frequency pulse negative hydrogen ion source is powered on when using direct current high voltage power supply, and is not powered on when using pulse high voltage power supply; the high-frequency low power pulse is also called maintenance pulse; Step three, large production of plasma state: generate large amount of plasma with low-frequency high power of pulse output low-frequency driving signal, and limit the pulse to a pulse with a narrowest pulse width and a very high amplitude, then continue to add delay to the pulse output high-frequency low power pulse for maintaining plasma survival state with double-frequency driving device; the delay time makes the amplitude of subsequent high-frequency low power pulse for maintaining plasma state lowest, and the pulse width only accounts for a few percent of low-frequency high power pulse repetition period for large production of plasma; and the anode power supply is fully powered on according to the set high voltage output; the low-frequency high power pulse is also called high yield pulse; Step four, whether the current high-frequency pulse negative hydrogen ion source is completed, if yes, end, if not, return to step two.

2. The method of claim 1, wherein the method further comprises: The high-frequency low power pulse width for maintaining plasma survival state in step two accounts for less than 5% of the low-frequency high power pulse repetition period. ​ 3. The method of claim 2, wherein the method further comprises: 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 time accounts for 94% of the low-frequency high power pulse repetition period.

4. The method of claim 1, wherein the method further comprises: providing a high frequency pulse negative hydrogen ion source; and providing a cathode electron load. The pulse width of low-frequency high power pulse for large production of plasma in step three is determined according to user's demand.

5. The method of claim 1, wherein the method further comprises: providing a high frequency pulse negative hydrogen ion source; and providing a cathode electron load. The delay time of low-frequency high power pulse in step two is the pulse width of high-frequency low power, 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 of claim 1, wherein the method further comprises: The high-frequency medium power in step one is 13 MHz, 300 W power.

7. The method of claim 1, wherein the method further comprises: providing a high frequency pulse negative hydrogen ion source; and providing a cathode electron load. The high-frequency low power in step two is 13 MHz, 100 W power.

8. The method of claim 1, wherein the method further comprises: providing a high frequency pulse negative hydrogen ion source; and providing a cathode electron load. The low-frequency high power in step three is 2 MHz, 80 kW power.

9. The method of claim 1, wherein the method further comprises: providing a high frequency pulse negative hydrogen ion source; and providing a cathode electron load. The width of the cold start pulse of step one is greater than the sum of the widths of the sustain pulses and the high yield pulses: the width is such as to ensure that the plasma is certainly ignited, to obtain the preferred electron and plasma density in the discharge chamber, and to allow the system to reach the thermal stability conditions in the working conditions.

Images