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RSS2022 Vol. 34, No. 6
Recommend Articles
2022, 34: 062001.
doi: 10.11884/HPLPB202234.220167
2022, 34: 069001.
doi: 10.11884/HPLPB202234.210404
Display Method:
2022,
34: 1-2.
2022,
34: 061001.
doi: 10.11884/HPLPB202234.210562
Abstract:
In this study, we design a high-magnification solid-state picosecond pulse laser amplifier in which the gain medium is Nd:YAG slab. We achieve the five-pass amplification of the picosecond pulse laser through the slab multi-angle magnification technology. The seed source works in pulse mode, and the amplifier pump works in continuous mode. Picosecond fiber laser can work at different repetition rates with 13.4 ps pulse duration. After the seed laser passes through the isolation and coupling system, the single-pulse energy injected into the slab is 25 nJ. When repetition frequency of the seed source is 24.46 MHz, the output power is 377 W, the single-pulse energy is 15.5 μJ. When repetition frequency of the seed source is 49.8 kHz, a laser output power of 89 W is obtained with single-pulse energy 1.8 mJ and peak power 134 MW. The magnification is up to 7.2×104.
In this study, we design a high-magnification solid-state picosecond pulse laser amplifier in which the gain medium is Nd:YAG slab. We achieve the five-pass amplification of the picosecond pulse laser through the slab multi-angle magnification technology. The seed source works in pulse mode, and the amplifier pump works in continuous mode. Picosecond fiber laser can work at different repetition rates with 13.4 ps pulse duration. After the seed laser passes through the isolation and coupling system, the single-pulse energy injected into the slab is 25 nJ. When repetition frequency of the seed source is 24.46 MHz, the output power is 377 W, the single-pulse energy is 15.5 μJ. When repetition frequency of the seed source is 49.8 kHz, a laser output power of 89 W is obtained with single-pulse energy 1.8 mJ and peak power 134 MW. The magnification is up to 7.2×104.
2022,
34: 061002.
doi: 10.11884/HPLPB202234.210558
Abstract:
As pump station, fiber-coupled diode laser source is one of the key elements of fiber laser, its performance restricts the output level of the fiber laser directly. Aimed at a multi-mode fiber of 105 μm core diameter and 0.22 numerical aperture, a 260 W-level high-brightness fiber-coupled diode laser model based on single-emitter-COS (chip on submount) is developed. In the design, volume Bragg grating (VBG) is used to control the spectrum of the corresponding emitter at a narrow bandwidth (about 0.5 nm), and the beam shaping technologies, polarization multiplexing and aspherical lens are taken to couple the 18 LD beams into the multi-mode fiber. The experiment indicates that, the beam shaping system can couple the 18 LD beams into the fiber, and the output power can achieve 264 W, with the E-O efficiency of 52% at operation current 18 A. Simultaneously, the central wavelength of the model is locked at 975.92 nm with an FWHM of 0.51 nm. This design offers a feasible approach to the spectral-controlled fiber-coupled diode laser. The engineered fiber-coupled diode laser system can be widely used in fiber pumping and many other areas.
As pump station, fiber-coupled diode laser source is one of the key elements of fiber laser, its performance restricts the output level of the fiber laser directly. Aimed at a multi-mode fiber of 105 μm core diameter and 0.22 numerical aperture, a 260 W-level high-brightness fiber-coupled diode laser model based on single-emitter-COS (chip on submount) is developed. In the design, volume Bragg grating (VBG) is used to control the spectrum of the corresponding emitter at a narrow bandwidth (about 0.5 nm), and the beam shaping technologies, polarization multiplexing and aspherical lens are taken to couple the 18 LD beams into the multi-mode fiber. The experiment indicates that, the beam shaping system can couple the 18 LD beams into the fiber, and the output power can achieve 264 W, with the E-O efficiency of 52% at operation current 18 A. Simultaneously, the central wavelength of the model is locked at 975.92 nm with an FWHM of 0.51 nm. This design offers a feasible approach to the spectral-controlled fiber-coupled diode laser. The engineered fiber-coupled diode laser system can be widely used in fiber pumping and many other areas.
2022,
34: 061003.
doi: 10.11884/HPLPB202234.220060
Abstract:
To study the 3ω damage characteristics of DKDP crystals after 3ω conditioning, 3ω and 1ω conditioning at the same time, a dual-wavelength conditioning and damage test experimental system was established. The conditioning effects of 1ω energy density under dual wavelength irradiation were studied emphatically. The energy coupling mechanism in the conditioning process of dual-wavelength irradiation was analyzed. Research results show that the effect of dual-wavelength conditioning is significantly better than that of single wavelength. In the case of dual-wavelength simultaneous irradiation conditioning, the 1ω which is far below the threshold value of its own conditioning participates in the conditioning. Under the same conditioning strategy of 3ω energy density and energy gradient, there is an optimal value of 1ω energy density.
To study the 3ω damage characteristics of DKDP crystals after 3ω conditioning, 3ω and 1ω conditioning at the same time, a dual-wavelength conditioning and damage test experimental system was established. The conditioning effects of 1ω energy density under dual wavelength irradiation were studied emphatically. The energy coupling mechanism in the conditioning process of dual-wavelength irradiation was analyzed. Research results show that the effect of dual-wavelength conditioning is significantly better than that of single wavelength. In the case of dual-wavelength simultaneous irradiation conditioning, the 1ω which is far below the threshold value of its own conditioning participates in the conditioning. Under the same conditioning strategy of 3ω energy density and energy gradient, there is an optimal value of 1ω energy density.
2022,
34: 062001.
doi: 10.11884/HPLPB202234.220167
Abstract:
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On Shenguang-III prototype facility, eight
(351.0 nm) laser beams are used to produce laser-scale high-temperature plasmas as well as to excite strong stimulated Brillouin scattering (SBS). An additional
(263.3 nm) laser beam, together with a large-aperture Thomson scattering diagnostic system, is applied to obtain the super-thermal collective Thomson scattering (STS) spectra of the ion acoustic waves driven by the SBS process of a
laser beam. By comparing and analyzing the STS spectra and the backward SBS spectra, the temporal and spatial evolution of SBS is revealed.
2022,
34: 063001.
doi: 10.11884/HPLPB202234.210576
Abstract:
To solve the problem of efficient heat dissipation of high-power miniaturized klystron collector under forced air cooling condition, this paper takes a high-power klystron as the research object, and introduces a design method of high-power and efficient air cooling collector system. ANSYS finite element software is used to simulate and calculate the forced air cooling heat dissipation characteristics of the collector. The effects of different cooling fin structures on the wind resistance and maximum temperature of the collector under non-uniform heat flux loading are analyzed and compared. The size and number of cooling fins are determined. To further improve the convective heat transfer effect of the air cooling collector system, the structure of the inlet of the collector is improved and the maximum temperature of the inner surface of the collector is reduced by 22 ℃. The calculation model of the wind resistance of the air cooling collector is used to verify the wind resistance. The difference between the simulation results and the theoretical value is 2.2%. Finally, the high-power klystron with the air cooling collector system is tested. The maximum temperature difference between the experimental and simulation results is 1.8%, which verifies the rationality and effectiveness of the design of the air cooling collector system.
To solve the problem of efficient heat dissipation of high-power miniaturized klystron collector under forced air cooling condition, this paper takes a high-power klystron as the research object, and introduces a design method of high-power and efficient air cooling collector system. ANSYS finite element software is used to simulate and calculate the forced air cooling heat dissipation characteristics of the collector. The effects of different cooling fin structures on the wind resistance and maximum temperature of the collector under non-uniform heat flux loading are analyzed and compared. The size and number of cooling fins are determined. To further improve the convective heat transfer effect of the air cooling collector system, the structure of the inlet of the collector is improved and the maximum temperature of the inner surface of the collector is reduced by 22 ℃. The calculation model of the wind resistance of the air cooling collector is used to verify the wind resistance. The difference between the simulation results and the theoretical value is 2.2%. Finally, the high-power klystron with the air cooling collector system is tested. The maximum temperature difference between the experimental and simulation results is 1.8%, which verifies the rationality and effectiveness of the design of the air cooling collector system.
2022,
34: 063002.
doi: 10.11884/HPLPB202234.210479
Abstract:
Ferrite circulators are key components in the high-power microwave systems for the satellite payload application. Multipactor, which is prone to occur in the high-power vacuum system, is still a bottleneck problem for the on-orbit reliable system operation. The physical evolution model of multipactor in ferromagnetic components is proposed based on the secondary electron emission (SEE) properties. Using the model, the evolution laws of the initial electrons and multipacting electrons in practical components with micro-pore arrays are revealed. Furthermore, a novel anti-multipactor design method is proposed through controlling the surface SEE of the ferromagnetic material. A group of S-band circulators were designed and fabricated for the validation of the theory and design method. Calculation results and measurement data demonstrate that multipactor discharge has been suppressed successfully through lowering the surface SEE on the ferrite plates. Multipactor threshold power of the traditional circulator has been improved from 380 W to more than 3400 W using the optimized micro-pore structures, and the suppression efficiency is increased by more than 900%.
Ferrite circulators are key components in the high-power microwave systems for the satellite payload application. Multipactor, which is prone to occur in the high-power vacuum system, is still a bottleneck problem for the on-orbit reliable system operation. The physical evolution model of multipactor in ferromagnetic components is proposed based on the secondary electron emission (SEE) properties. Using the model, the evolution laws of the initial electrons and multipacting electrons in practical components with micro-pore arrays are revealed. Furthermore, a novel anti-multipactor design method is proposed through controlling the surface SEE of the ferromagnetic material. A group of S-band circulators were designed and fabricated for the validation of the theory and design method. Calculation results and measurement data demonstrate that multipactor discharge has been suppressed successfully through lowering the surface SEE on the ferrite plates. Multipactor threshold power of the traditional circulator has been improved from 380 W to more than 3400 W using the optimized micro-pore structures, and the suppression efficiency is increased by more than 900%.
2022,
34: 063003.
doi: 10.11884/HPLPB202234.210499
Abstract:
To design the test setup and predict the effect of GJB151B CS115 “impulse excitation bulk cable injection conducted susceptibility”, we introduced the circuit model of inductive pulse current injection for different type of cables. The influences on the injected voltage/current caused by the factors of the test setup are simulated and analyzed. Some regularity characteristics of CS115 test setting are summarized, and the method of CS115 test design and optimization by circuit simulation is proposed.
To design the test setup and predict the effect of GJB151B CS115 “impulse excitation bulk cable injection conducted susceptibility”, we introduced the circuit model of inductive pulse current injection for different type of cables. The influences on the injected voltage/current caused by the factors of the test setup are simulated and analyzed. Some regularity characteristics of CS115 test setting are summarized, and the method of CS115 test design and optimization by circuit simulation is proposed.
2022,
34: 063004.
doi: 10.11884/HPLPB202234.210360
Abstract:
Photoconductive switch can be used in high power microwave system. The breakdown resistance field strength of SiC photoconductive switches is mainly limited by packaging. The packaging method cannot effectively solve the problem of electric field accumulation when the copper electrode leaves the SiC substrate, which leads to the application field strength of SiC far lower than the breakdown resistance strength of SiC crystal. The effects of the structure of the electrode and the connection structure of SiC to the electrode on the interfacial field intensity are studied. The electric field enhancement at the interface is reduced by optimizing the edge of the electrode and the SiC crystal structure. The breakdown voltage of optimized electrode structure is tested. The results show that the electric field enhancement can be effectively reduced by optimizing the electrode chamfering and burying under the interface between SiC crystal and electrode. Under the structure of circular chamfering and interface connecting with solder, the SiC photoconductive switch breaks down at the voltage of 22 kV.
Photoconductive switch can be used in high power microwave system. The breakdown resistance field strength of SiC photoconductive switches is mainly limited by packaging. The packaging method cannot effectively solve the problem of electric field accumulation when the copper electrode leaves the SiC substrate, which leads to the application field strength of SiC far lower than the breakdown resistance strength of SiC crystal. The effects of the structure of the electrode and the connection structure of SiC to the electrode on the interfacial field intensity are studied. The electric field enhancement at the interface is reduced by optimizing the edge of the electrode and the SiC crystal structure. The breakdown voltage of optimized electrode structure is tested. The results show that the electric field enhancement can be effectively reduced by optimizing the electrode chamfering and burying under the interface between SiC crystal and electrode. Under the structure of circular chamfering and interface connecting with solder, the SiC photoconductive switch breaks down at the voltage of 22 kV.
Cold cavity characteristics of a new type of low-inductance magnetically insulated transmission line
2022,
34: 063005.
doi: 10.11884/HPLPB202234.210494
Abstract:
The vacuum part of the transverse section of this configuration is composed of 12 petal-like periods, and each period is composed of two basic transmission line configurations: parallel plates and coaxial arcs. The overall outline of this configuration effectively increases the electrode area, which greatly reduces the inductance of the transmission line, so that a lower impedance can be obtained by using a single-layer magnetically insulated transmission line,which avoids the complex PHC structure and the loss of the magnetic null region caused by the multi-layer bus structure. The electromagnetic field distribution, inductance, capacitance, and impedance of the two basic configuration units are calculated separately, and then the electromagnetic characteristic parameters of the petal-shaped magnetic insulated transmission line are calculated and analyzed as a whole. At the same time, the cold cavity characteristics of the transmission line are analyzed through numerical simulation, the impedance value and electromagnetic field distribution of the transmission line are obtained, and the numerical simulation results are compared with the theoretical calculation values for verification and analysis.
The vacuum part of the transverse section of this configuration is composed of 12 petal-like periods, and each period is composed of two basic transmission line configurations: parallel plates and coaxial arcs. The overall outline of this configuration effectively increases the electrode area, which greatly reduces the inductance of the transmission line, so that a lower impedance can be obtained by using a single-layer magnetically insulated transmission line,which avoids the complex PHC structure and the loss of the magnetic null region caused by the multi-layer bus structure. The electromagnetic field distribution, inductance, capacitance, and impedance of the two basic configuration units are calculated separately, and then the electromagnetic characteristic parameters of the petal-shaped magnetic insulated transmission line are calculated and analyzed as a whole. At the same time, the cold cavity characteristics of the transmission line are analyzed through numerical simulation, the impedance value and electromagnetic field distribution of the transmission line are obtained, and the numerical simulation results are compared with the theoretical calculation values for verification and analysis.
2022,
34: 064001.
doi: 10.11884/HPLPB202234.210522
Abstract:
The signal-to-noise ratio (SNR) of DBPM signal is one of the important parameters to measure the performance of BPM, and it plays a decisive role in the resolution of beam position measurement. Based on the position measurement resolution requirements of high energy photon source (HEPS) for BPM, this paper firstly introduces the overall architecture of BPM system and deduces the signal-to-noise ratio of signals at all levels in the signal link of BPM system. Then the calculation method of ADC sampling clock jitter and BPM electronics test platform are introduced. The conclusions in this paper can be used as a standard to judge whether each part of BPM system can meet the requirements of HEPS, which is of great significance to promote the batch application of self-developed BPM electronics in HEPS engineering.
The signal-to-noise ratio (SNR) of DBPM signal is one of the important parameters to measure the performance of BPM, and it plays a decisive role in the resolution of beam position measurement. Based on the position measurement resolution requirements of high energy photon source (HEPS) for BPM, this paper firstly introduces the overall architecture of BPM system and deduces the signal-to-noise ratio of signals at all levels in the signal link of BPM system. Then the calculation method of ADC sampling clock jitter and BPM electronics test platform are introduced. The conclusions in this paper can be used as a standard to judge whether each part of BPM system can meet the requirements of HEPS, which is of great significance to promote the batch application of self-developed BPM electronics in HEPS engineering.
2022,
34: 064002.
doi: 10.11884/HPLPB202234.210345
Abstract:
To obtain the spatial distribution image of low intensity radiation source better, a method is proposed to restore large aperture thick pinhole degraded image using neural network algorithm. The thick pinhole model of 5 mm, 10 mm and 15 mm apertures is established, and the degenerate image sets of thick pinhole for the shape radiation source of 3600 Chinese characters are obtained. Based on the DnCNN neural network model, the neural network for image restoration with large aperture and thick pinhole is obtained, and compared with traditional algorithms such as Wiener filter and Lucy Richardson. After considering the influence of noise, the original neural network model is trained by means of transfer learning theory, and then the degraded image of large aperture pinhole with noise is restored. The RMSE of neural network algorithm is significantly lower than that of the traditional one, and the effect of noise is greatly improved by transfer learning. This paper proves the superiority of neural network algorithm in the field of image restoration with large aperture and thick pinhole, and verifies the feasibility of neural network method to restore the large aperture thick pinhole degraded image with noise.
To obtain the spatial distribution image of low intensity radiation source better, a method is proposed to restore large aperture thick pinhole degraded image using neural network algorithm. The thick pinhole model of 5 mm, 10 mm and 15 mm apertures is established, and the degenerate image sets of thick pinhole for the shape radiation source of 3600 Chinese characters are obtained. Based on the DnCNN neural network model, the neural network for image restoration with large aperture and thick pinhole is obtained, and compared with traditional algorithms such as Wiener filter and Lucy Richardson. After considering the influence of noise, the original neural network model is trained by means of transfer learning theory, and then the degraded image of large aperture pinhole with noise is restored. The RMSE of neural network algorithm is significantly lower than that of the traditional one, and the effect of noise is greatly improved by transfer learning. This paper proves the superiority of neural network algorithm in the field of image restoration with large aperture and thick pinhole, and verifies the feasibility of neural network method to restore the large aperture thick pinhole degraded image with noise.
2022,
34: 064003.
doi: 10.11884/HPLPB202234.210454
Abstract:
To meet the needs of the magnetic field accuracy of the Separated Sector Cyclotron (SSC), the main field power supply must be modified. We proposed a combination of switching power supply and linear power supply as the transformation solution of new power supply. There are two parts of the power supply, modular switching power supply is used as the front-end voltage source, and the triode linear adjustment circuit is used as the main circuit of the back-end module. Making full use of the advantages of these two kinds of power supplies, a power supply with high-stability and low-ripple current output was achieved, while the power density and reliability was greatly improved. The article introduces the principle and the reformation process of the power supply, elaborates the linear amplification principle of the triode, the design of the tube voltage drop control circuit and the output current control circuit. The power supply was verified through the simulation, and tested experimentally on the power supply prototype. The test results show that the stability of the output current after the reformation has reached ±3.99×10−6, the current ripple has reached 2.7×10−9, the performances are better than that before reformation.
To meet the needs of the magnetic field accuracy of the Separated Sector Cyclotron (SSC), the main field power supply must be modified. We proposed a combination of switching power supply and linear power supply as the transformation solution of new power supply. There are two parts of the power supply, modular switching power supply is used as the front-end voltage source, and the triode linear adjustment circuit is used as the main circuit of the back-end module. Making full use of the advantages of these two kinds of power supplies, a power supply with high-stability and low-ripple current output was achieved, while the power density and reliability was greatly improved. The article introduces the principle and the reformation process of the power supply, elaborates the linear amplification principle of the triode, the design of the tube voltage drop control circuit and the output current control circuit. The power supply was verified through the simulation, and tested experimentally on the power supply prototype. The test results show that the stability of the output current after the reformation has reached ±3.99×10−6, the current ripple has reached 2.7×10−9, the performances are better than that before reformation.
2022,
34: 064004.
doi: 10.11884/HPLPB202234.210481
Abstract:
When the hydrogen atom beam is transmitted in the atmosphere, the atmospheric stripping effect formed by the collision ionization between the beam particles and the atmospheric particles and the self-stripping effect formed by the collision ionization with the atmospheric particles are the important mechanisms causing the energy loss of the hydrogen atom beam. Due to the complex causes of self-stripping effect, although there are some theoretical research results, there is no experimental or numerical simulation work on its occurrence mechanism and beam loss effect. Therefore, this paper further improves the theory of self-stripping effect by analyzing the occurrence mechanism of self-stripping effect and its influence on beam loss. On the basis of verifying the applicability of particle cloud grid Monte-Carlo method to the atmospheric transport simulation of hydrogen atom beam through the beam transport equation, the simulation results are compared with the self-stripping theory, which basically verifies the applicability of the self-stripping effect theory. The simulation results show that the self-stripping effect is caused by the charged secondary particle clusters produced by the beam ionization by the atmosphere constantly passing through the beam under the influence of the geomagnetic field, and the strength of the self-stripping effect is related to the density of the atomic beam. The greater the beam density, the stronger the self-stripping effect, and the greater the influence on the beam.
When the hydrogen atom beam is transmitted in the atmosphere, the atmospheric stripping effect formed by the collision ionization between the beam particles and the atmospheric particles and the self-stripping effect formed by the collision ionization with the atmospheric particles are the important mechanisms causing the energy loss of the hydrogen atom beam. Due to the complex causes of self-stripping effect, although there are some theoretical research results, there is no experimental or numerical simulation work on its occurrence mechanism and beam loss effect. Therefore, this paper further improves the theory of self-stripping effect by analyzing the occurrence mechanism of self-stripping effect and its influence on beam loss. On the basis of verifying the applicability of particle cloud grid Monte-Carlo method to the atmospheric transport simulation of hydrogen atom beam through the beam transport equation, the simulation results are compared with the self-stripping theory, which basically verifies the applicability of the self-stripping effect theory. The simulation results show that the self-stripping effect is caused by the charged secondary particle clusters produced by the beam ionization by the atmosphere constantly passing through the beam under the influence of the geomagnetic field, and the strength of the self-stripping effect is related to the density of the atomic beam. The greater the beam density, the stronger the self-stripping effect, and the greater the influence on the beam.
2022,
34: 064005.
doi: 10.11884/HPLPB202234.210478
Abstract:
Non-evaporable getter films are widely used in particle accelerators. It has become an integral part of many particle accelerators. Ti-Zr-V films were deposited on Si substrates and straight and bent Ag-Cu tubes with an inner diameter of 22 mm by DC magnetron sputtering. After baked at 180 ℃ for 24 h, the ultimate vacuum of the coated tubes reached 9.2×10−10 Pa. The tubes with activated getter films maintained at 9×10−9 Pa after closing tubes and ion pump valve. The pumping speed and capacity of Ti-Zr-V films were measured by Test Particle Monte Carlo method. The results show that the best CO sticking probability reaches 0.3, with a pumping capacity of 1.2 monolayer.
Non-evaporable getter films are widely used in particle accelerators. It has become an integral part of many particle accelerators. Ti-Zr-V films were deposited on Si substrates and straight and bent Ag-Cu tubes with an inner diameter of 22 mm by DC magnetron sputtering. After baked at 180 ℃ for 24 h, the ultimate vacuum of the coated tubes reached 9.2×10−10 Pa. The tubes with activated getter films maintained at 9×10−9 Pa after closing tubes and ion pump valve. The pumping speed and capacity of Ti-Zr-V films were measured by Test Particle Monte Carlo method. The results show that the best CO sticking probability reaches 0.3, with a pumping capacity of 1.2 monolayer.
2022,
34: 064006.
doi: 10.11884/HPLPB202234.210133
Abstract:
The high current linear induction accelerators (LIA) is mainly made for advanced radiography which is the most important test method in hydrokinetics study. The required reliability of the whole test system is very high. The pulsed power system of LIA is very huge and complex. It includes several different kinds of high voltage equipment. There are some possibilities of self-excitaion for the equipment when they are charging or waiting after charged. If self-excitaion happens and no measure is taken, radiographic test would be unsuccessful, and heavy economic loss and bad effect are ineluctable. A method of improving the reliability of advanced radiography is developed based on monitoring the self-excitation of pulsed power system. Passive detector with high reliability for high voltage pulse discharging is first developed based on a certain extent linear principle and several type of detectors are also developed for different discharging equipment. Programmable large scale integrated circuits (LSIs) are adopted to make up of the logic processor in the system to improve the system integration degree, to simplify the circuit and to reduce the debugging difficulty. The monitor and controller system can be easily extended to meet more lines monitor demand. The fast response of the system is about hundred nanoseconds. Its anti-jamming ability can fully meet the demand of the radiographic test environment condition and achieve the goal of improving the the reliability of advanced radiography.
The high current linear induction accelerators (LIA) is mainly made for advanced radiography which is the most important test method in hydrokinetics study. The required reliability of the whole test system is very high. The pulsed power system of LIA is very huge and complex. It includes several different kinds of high voltage equipment. There are some possibilities of self-excitaion for the equipment when they are charging or waiting after charged. If self-excitaion happens and no measure is taken, radiographic test would be unsuccessful, and heavy economic loss and bad effect are ineluctable. A method of improving the reliability of advanced radiography is developed based on monitoring the self-excitation of pulsed power system. Passive detector with high reliability for high voltage pulse discharging is first developed based on a certain extent linear principle and several type of detectors are also developed for different discharging equipment. Programmable large scale integrated circuits (LSIs) are adopted to make up of the logic processor in the system to improve the system integration degree, to simplify the circuit and to reduce the debugging difficulty. The monitor and controller system can be easily extended to meet more lines monitor demand. The fast response of the system is about hundred nanoseconds. Its anti-jamming ability can fully meet the demand of the radiographic test environment condition and achieve the goal of improving the the reliability of advanced radiography.
2022,
34: 064007.
doi: 10.11884/HPLPB202234.210491
Abstract:
X-ray free-electron laser (XFEL), due to its ultra-high brightness, ultra-short pulse and other characteristics, has been built worldwide. Based on the theory of wakefield, we calculate the resistive wall wakefield from the linear accelerator (linac) exit to the end of the undulator in Shanghai X-ray free electron laser (SXFEL) with bunch traveling through the 245 m stainless steel transfer line and copper beamline in undulator. Then we analyze the resistive wall wakefields which eventually lead to the distortion of the longitudinal phase space within the bunch. Finally, the theoretical predictions of influence of resistive wall wakefield are compared with experiment results on SXFEL, which shows great agreement. The detailed research provides a direction for subsequent FEL optimization.
2022,
34: 064008.
doi: 10.11884/HPLPB202234.210518
Abstract:
According to the requirements of relevant construction safety assessment, environmental assessment, stability assessment and occupational health assessment, the radiation situation of electron accelerator should be analyzed in the design process. The radiation source of photocathode RF electron gun linac with adjustable electron energy from 40 MeV to 95 MeV was analyzed, and the effect of possible radiation protection was discussed. Monte Carlo software FLUKA was used to model the electron beam and accelerator. Through simulation calculation, it is found that the dose equivalent distribution generated by the accelerator is mainly located in the beam dump, and the radiation dose outside the beam dump decreases rapidly. When the concrete shielding wall is set around the electron accelerator experimental hall, the radiation dose equivalent will decrease rapidly with the wall thickness. If the thickness of the concrete shielding wall was set to 1 m, the radiation dose equivalent in the area where the staff outside the shielding wall were located should not be higher than 1 μSv/h. So, the wall can effectively shield the ionizing radiation generated by the accelerator and provide effective protection for the staff.
According to the requirements of relevant construction safety assessment, environmental assessment, stability assessment and occupational health assessment, the radiation situation of electron accelerator should be analyzed in the design process. The radiation source of photocathode RF electron gun linac with adjustable electron energy from 40 MeV to 95 MeV was analyzed, and the effect of possible radiation protection was discussed. Monte Carlo software FLUKA was used to model the electron beam and accelerator. Through simulation calculation, it is found that the dose equivalent distribution generated by the accelerator is mainly located in the beam dump, and the radiation dose outside the beam dump decreases rapidly. When the concrete shielding wall is set around the electron accelerator experimental hall, the radiation dose equivalent will decrease rapidly with the wall thickness. If the thickness of the concrete shielding wall was set to 1 m, the radiation dose equivalent in the area where the staff outside the shielding wall were located should not be higher than 1 μSv/h. So, the wall can effectively shield the ionizing radiation generated by the accelerator and provide effective protection for the staff.
2022,
34: 064009.
doi: 10.11884/HPLPB202234.210537
Abstract:
In linear accelerator free-electron laser facilities, energy spread is an important parameter reflecting the quality of the beam. The traditional measurement method, which uses a bending magnet, fluorescent screens and cameras, is an interceptive measurement method. The beam hitting the screen cannot be utilized during the measurement, and the measured data is the average of multiple macro pulses. Moreover, when using the measurement results of this method for beam tuning, the commissioning may take a long time since the fluorescent screens need to be repeatedly inserted and raised from the beam trajectory, thus new non-interceptive measurement methods need to be developed. This paper implements such a method using a single 4-stripline beam position monitor in conjunction with the emittance measurement method. This method is able to measure the energy spread of each macro beam pulse without inserting extra equipment. The measurement results are in agreement with those of the conventional interceptive measurement method. It is indicated by the error analysis that in order to reduce the measurement systematic error, it is necessary to make the beam pass through the center of the beam position monitor.
In linear accelerator free-electron laser facilities, energy spread is an important parameter reflecting the quality of the beam. The traditional measurement method, which uses a bending magnet, fluorescent screens and cameras, is an interceptive measurement method. The beam hitting the screen cannot be utilized during the measurement, and the measured data is the average of multiple macro pulses. Moreover, when using the measurement results of this method for beam tuning, the commissioning may take a long time since the fluorescent screens need to be repeatedly inserted and raised from the beam trajectory, thus new non-interceptive measurement methods need to be developed. This paper implements such a method using a single 4-stripline beam position monitor in conjunction with the emittance measurement method. This method is able to measure the energy spread of each macro beam pulse without inserting extra equipment. The measurement results are in agreement with those of the conventional interceptive measurement method. It is indicated by the error analysis that in order to reduce the measurement systematic error, it is necessary to make the beam pass through the center of the beam position monitor.
2022,
34: 064010.
doi: 10.11884/HPLPB202234.210548
Abstract:
The evolution of electromagnetic field and fluid is important in the research of high energy density physics, controlled nuclear fusion, and laboratory astrophysics. But in experiment, it is difficult to get the density and electromagnetic field distribution simultaneously. Based on high energy electron lens radiography, this paper proposes dual degrees of freedom diagnosis (DDFD) by constructing areal density difference. Combining the Monte-Carlo simulation and beam optics analysis, the feasibility of this method when the diagnosed system includes relatively strong electromagnetic field has been validated. Besides, changing the aperture as a ring can effectively improve the resolution in low E/B field and low areal density situation. The simulation results indicate that this method works well. Considering the characters of electron beams, this method is quite suitable for the electromagnetic fluid diagnosis.
2022,
34: 065001.
doi: 10.11884/HPLPB202234.210449
Abstract:
For the attack, interference and detection of the target, the amplitude of the UWB time-domain pulse source directly affects the intensity and effect. The Marx circuit based on avalanche transistors is widely used to generate such signal sources. The traditional Marx circuit can increase the amplitude of the output voltage to a certain extent. However, due to the low power capacity of the avalanche transistor, the output voltage of the Marx circuit of the avalanche transistor is low. The amplitude will reach saturation with the increase of the number of stages. To generate a higher amplitude pulse signal, this study comprehensively adopts the means of increasing the trigger signal and using a broadband power combiner. Finally it uses a 26-level Marx circuit as the trigger signal, by the method of 4-channel 40-level Marx circuit for power synthesis, the output voltage amplitude is 8.7 kV, the rising edge is about 180 ps, and the impact of high trigger signal on the avalanche transistor Marx circuit is analyzed through mechanism. The experiment was confirmed.
For the attack, interference and detection of the target, the amplitude of the UWB time-domain pulse source directly affects the intensity and effect. The Marx circuit based on avalanche transistors is widely used to generate such signal sources. The traditional Marx circuit can increase the amplitude of the output voltage to a certain extent. However, due to the low power capacity of the avalanche transistor, the output voltage of the Marx circuit of the avalanche transistor is low. The amplitude will reach saturation with the increase of the number of stages. To generate a higher amplitude pulse signal, this study comprehensively adopts the means of increasing the trigger signal and using a broadband power combiner. Finally it uses a 26-level Marx circuit as the trigger signal, by the method of 4-channel 40-level Marx circuit for power synthesis, the output voltage amplitude is 8.7 kV, the rising edge is about 180 ps, and the impact of high trigger signal on the avalanche transistor Marx circuit is analyzed through mechanism. The experiment was confirmed.
2022,
34: 065002.
doi: 10.11884/HPLPB202234.210477
Abstract:
To control the toroidal field current efficiently and accurately, and to improve the experimental efficiency of the HL-2M tokamak, a simulation study on 300 MV·A six-phase motor generator (MG) feeding the toroidal field power supply (TFPS) is carried out. The topology of 300 MV·A six-phase MG feeding the TFPS is introduced, and its simulation model is established based on the equivalent processing analysis and the dynamic process of pulse discharge is simulated. The reliability and rationality of the simulation model are verified by comparing the simulation waveforms with the actual waveforms of the 300 MV·A six-phase MG feeding the TFPS of the HL-2A Tokamak. On this basis, the simulation of 300 MVA six-phase MG feeding the TFPS of HL-2M is carried out, and the corresponding excitation voltage control waveforms of the MG are obtained according to the different flat top values of the TF current, providing an important reference for the next stage high-parameter experimental control and research platform of advanced control strategy.
To control the toroidal field current efficiently and accurately, and to improve the experimental efficiency of the HL-2M tokamak, a simulation study on 300 MV·A six-phase motor generator (MG) feeding the toroidal field power supply (TFPS) is carried out. The topology of 300 MV·A six-phase MG feeding the TFPS is introduced, and its simulation model is established based on the equivalent processing analysis and the dynamic process of pulse discharge is simulated. The reliability and rationality of the simulation model are verified by comparing the simulation waveforms with the actual waveforms of the 300 MV·A six-phase MG feeding the TFPS of the HL-2A Tokamak. On this basis, the simulation of 300 MVA six-phase MG feeding the TFPS of HL-2M is carried out, and the corresponding excitation voltage control waveforms of the MG are obtained according to the different flat top values of the TF current, providing an important reference for the next stage high-parameter experimental control and research platform of advanced control strategy.
2022,
34: 065003.
doi: 10.11884/HPLPB202234.210527
Abstract:
An arc jet plasma actuator was designed for drag reduction of hypersonic vehicle to achieve better drag reduction effect. The characteristics of the arc jet plasma actuator were simulated numerically by using the finite element method to solve the nonlinear multiple physical equations, and the distributions of potential, pressure, temperature and velocity inside the actuator were obtained, and the influencing effects of velocity at the inlet, current, radius of the pipe on the distributions of potential, pressure, temperature and velocity were analyzed comprehensively. The comprehensive influence laws are obtained, and the simulation shows that the arc jet plasma actuator can produce a plasma jet with a maximum temperature of 8638 K and a maximum velocity of 655 m/s. The minimum power is required when the inlet gas velocity is the least, the maximum average temperature at the exit is obtained when the plasma current is the largest and the inlet gas velocity is medium. The maximum average speed at the exit is obtained at the largest current and the largest inlet gas velocity. Validation by experiment is also carried out. Comparison between the experimental and simulation results also show good agreement under similar plasma parameters.
An arc jet plasma actuator was designed for drag reduction of hypersonic vehicle to achieve better drag reduction effect. The characteristics of the arc jet plasma actuator were simulated numerically by using the finite element method to solve the nonlinear multiple physical equations, and the distributions of potential, pressure, temperature and velocity inside the actuator were obtained, and the influencing effects of velocity at the inlet, current, radius of the pipe on the distributions of potential, pressure, temperature and velocity were analyzed comprehensively. The comprehensive influence laws are obtained, and the simulation shows that the arc jet plasma actuator can produce a plasma jet with a maximum temperature of 8638 K and a maximum velocity of 655 m/s. The minimum power is required when the inlet gas velocity is the least, the maximum average temperature at the exit is obtained when the plasma current is the largest and the inlet gas velocity is medium. The maximum average speed at the exit is obtained at the largest current and the largest inlet gas velocity. Validation by experiment is also carried out. Comparison between the experimental and simulation results also show good agreement under similar plasma parameters.
2022,
34: 066001.
doi: 10.11884/HPLPB202234.210363
Abstract:
Accurately estimating the spatial position of the interaction between the ray and the detector in radiation imaging is a key step to ensure the imaging quality. To further improve the position effect of radiation events and effectively suppress the position shift caused by the center of gravity method when radiation events are close to the edge of the detector, a response function-based position algorithm is established for the position -sensitive detection system composed of Si-PM arrays. A position-sensitive detector based on CsI array and Si-PM array and an ASIC-based electronic readout system were built, and the equivalent resistance network was used to simplify the number of output signals of Si-PM array, then the response functions of radiation events on Si-PM arrays were obtained experimentally. The experimental results show that under the same conditions, the FWHM of the scatter points of the most edge pixels using the response function method is only 46.2% of the FWHM obtained by using the center of gravity method, which is comparable to the FWHM of the scatter points of the central pixels, the localization effect of the radiation event method based on the response function is obviously better than that of the traditional center of gravity method, which can effectively overcome the edge effect of the center of gravity method.
Accurately estimating the spatial position of the interaction between the ray and the detector in radiation imaging is a key step to ensure the imaging quality. To further improve the position effect of radiation events and effectively suppress the position shift caused by the center of gravity method when radiation events are close to the edge of the detector, a response function-based position algorithm is established for the position -sensitive detection system composed of Si-PM arrays. A position-sensitive detector based on CsI array and Si-PM array and an ASIC-based electronic readout system were built, and the equivalent resistance network was used to simplify the number of output signals of Si-PM array, then the response functions of radiation events on Si-PM arrays were obtained experimentally. The experimental results show that under the same conditions, the FWHM of the scatter points of the most edge pixels using the response function method is only 46.2% of the FWHM obtained by using the center of gravity method, which is comparable to the FWHM of the scatter points of the central pixels, the localization effect of the radiation event method based on the response function is obviously better than that of the traditional center of gravity method, which can effectively overcome the edge effect of the center of gravity method.
2022,
34: 066002.
doi: 10.11884/HPLPB202234.210375
Abstract:
Aiming at the difficulty to identify far-region nuclear and lightning electromagnetic pulse correctly, a recognition method based on wavelet fractal technique was proposed. First, the signals of nuclear electromagnetic pulse (NEMP) and lightning electromagnetic pulse (LEMP), preprocessed by interpolation and normalization, were decomposed by wavelet packet at level two. Then, fractal dimensions of reconstructed signal from wavelet packet coefficients were calculated to form eigenvectors of NEMP and LEMP. Least squares support vector machine was chosen as the classifier and the model parameters were obtained by the five-fold cross validation. Finally, the eigenvectors were input into least squares support vector machine (LSSVM) for training and testing. The experimental results show that the combination of wavelet fractal technique and LSSVM performs well in recognition of NEMP and LEMP; the average recognition rate is more than 99%.
Aiming at the difficulty to identify far-region nuclear and lightning electromagnetic pulse correctly, a recognition method based on wavelet fractal technique was proposed. First, the signals of nuclear electromagnetic pulse (NEMP) and lightning electromagnetic pulse (LEMP), preprocessed by interpolation and normalization, were decomposed by wavelet packet at level two. Then, fractal dimensions of reconstructed signal from wavelet packet coefficients were calculated to form eigenvectors of NEMP and LEMP. Least squares support vector machine was chosen as the classifier and the model parameters were obtained by the five-fold cross validation. Finally, the eigenvectors were input into least squares support vector machine (LSSVM) for training and testing. The experimental results show that the combination of wavelet fractal technique and LSSVM performs well in recognition of NEMP and LEMP; the average recognition rate is more than 99%.
2022,
34: 069001.
doi: 10.11884/HPLPB202234.210404
Abstract:
As a new branch in non-thermal plasmas, plasma-liquid technology is characterized by low temperature, mass and heat transfer effectiveness, atmospheric-pressure operation and high reactivity. Process intensification techniques based on liquid plasmas have wide applications in nanofabrication, volatile organic compounds decomposition, sterilization and disinfection, chemical synthesis, etc. Taking the synthesis of nanomaterials by the liquid plasma as the research object, firstly, the reactive radicals that may exist in the system are introduced, together with the relevant characterization methods and possible reaction mechanisms; afterwards, the most widely adopted plasma-liquid systems are illustrated, which can be divided into non-immersed systems and immersed systems according to whether plasma is formed within the bulk of electrolytes; furthermore, several typical examples of nanomaterials synthesized by the plasma-liquid method are presented, with a summary of the state-of-art research in this field, finally, the challenges and development trends are discussed.
