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RSS2022 Vol. 34, No. 8
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2022,
34: 1-2.
2022,
34: 081001.
doi: 10.11884/HPLPB202234.220220
Abstract:
High power fiber lasers with high beam quality have been widely employed in applications of industrial manufacture. However, the power scaling of the fiber lasers with high beam quality are limited by the fiber nonlinear effects and the transverse mode instability. It is promising to simultaneously mitigate the fiber nonlinear effects and transverse mode instability by employing large mode area gain fiber with novel structure. In this letter, we report a 6 kW fiber laser with high beam quality, which is realized based on home-made ytterbium-doped fiber with gradually varying spindle-shape structure. The fiber laser employs the master oscillation power amplification structure. In the stage of laser amplifier, spindle-shape ytterbium-doped fiber is bidirectionally pumped by laser diodes with 981 nm wavelength. At the total pump power of 7.68 kW, the maximum output power reaches 6.02 kW with a beam quality M2 factor of 1.9. By optimizing the manufacture techniques and structure parameters of the spindle-shape ytterbium-doped fiber, it is promising to achieve fiber lasers with higher power and nearly single mode beam quality.
2022,
34: 081002.
doi: 10.11884/HPLPB202234.210413
Abstract:
The damage of pulse compression gratings is the key factor offecting the stable operation and power improvement of chirped pulse amplification system. In this paper, the laser-induced damage mechanism of pulse compression grating under laser radiation is summarized, the effects of surface morphology, processing mode, structural defects and surface pollution on grating damage are explored, and the internal causes of damage are explained from the perspective of micro damage mechanism. In the aspects of laser pretreatment, processing technology and surface pollutant removal of pulse compression grating, the internal factors to improve the grating damage threshold are analyzed, and the technical measures to improve the grating damage threshold are given. A combination of various measures is proposed to improve the laser-induced damage threshold of the grating. The research on laser damage mechanism and threshold of pulse compression grating has practical significance for the stable operation of pulse compression grating system and lays a foundation for the output of high energy density of laser device. Finally, this paper puts forward the scientific and technical problems of grating’s laser-induced damage research, which provides new ideas for improving the laser-induced damage threshold of pulse compression grating, and help the development of major scientific devices and important technical fields.
2022,
34: 081003.
doi: 10.11884/HPLPB202234.220107
Abstract:
Flowing unsupported liquid thin films are widely used in various fields. Energetic ions and high brightness secondary radiation covering THz to gamma rays will be generated when super intense laser acting on such a film, with the significant advantages of high repetition-rate, low cost and continuous operation. Methods for preparing liquid films include impinging jets, converging nozzle, gas-dynamic nozzle and wire-guided jet, each with its own characteristics, which can be measured by optical diagnosis. White light interference and monochromatic light interferometry are introduced, and an example is given to illustrate these two methods. This paper provides an overview of the preparation and characterization of liquid thin film target, and summarizes its applications and prospect in laser-driven radiation sources as well as laser ion acceleration.
Flowing unsupported liquid thin films are widely used in various fields. Energetic ions and high brightness secondary radiation covering THz to gamma rays will be generated when super intense laser acting on such a film, with the significant advantages of high repetition-rate, low cost and continuous operation. Methods for preparing liquid films include impinging jets, converging nozzle, gas-dynamic nozzle and wire-guided jet, each with its own characteristics, which can be measured by optical diagnosis. White light interference and monochromatic light interferometry are introduced, and an example is given to illustrate these two methods. This paper provides an overview of the preparation and characterization of liquid thin film target, and summarizes its applications and prospect in laser-driven radiation sources as well as laser ion acceleration.
2022,
34: 081004.
doi: 10.11884/HPLPB202234.220078
Abstract:
A high power high beam quality vertical-cavity surface-emitting laser (VCSEL) side-pumped rod Nd:YAG laser oscillator is demonstrated. Based on the macro-channel optimization of the active heat sink for the VCSEL pump source, five 227 W VCSEL linear arrays are manufactured. By optimizing the structure of the side-pumped diffuse chamber, a rod laser module with an output capacity of 480 W and 49.7% optical-to-optical efficiency is developed. Accordingly, a telescopic module is introduced in the laser oscillator to realize a large fundamental mode volume, and thermal-near-unstable parameters is further optimized to suppress higher transversal modes. Finally, an output power of 114 W is obtained with an average beam quality factor M2 of 1.42, and the power variations are ± 0.9% over 200 s and ± 4.2% over the temperature range from 18 ℃ to 26 ℃. To the best of our knowledge, this is the first time that a hundred-watt level and near diffraction limit beam quality laser is generated by VCSEL pumped scheme. Due to the excellent temperature stability of the VCSEL, this high-power and high beam quality solid-state laser has a promising competence in industry, space and other complicated environments.
A high power high beam quality vertical-cavity surface-emitting laser (VCSEL) side-pumped rod Nd:YAG laser oscillator is demonstrated. Based on the macro-channel optimization of the active heat sink for the VCSEL pump source, five 227 W VCSEL linear arrays are manufactured. By optimizing the structure of the side-pumped diffuse chamber, a rod laser module with an output capacity of 480 W and 49.7% optical-to-optical efficiency is developed. Accordingly, a telescopic module is introduced in the laser oscillator to realize a large fundamental mode volume, and thermal-near-unstable parameters is further optimized to suppress higher transversal modes. Finally, an output power of 114 W is obtained with an average beam quality factor M2 of 1.42, and the power variations are ± 0.9% over 200 s and ± 4.2% over the temperature range from 18 ℃ to 26 ℃. To the best of our knowledge, this is the first time that a hundred-watt level and near diffraction limit beam quality laser is generated by VCSEL pumped scheme. Due to the excellent temperature stability of the VCSEL, this high-power and high beam quality solid-state laser has a promising competence in industry, space and other complicated environments.
2022,
34: 081005.
doi: 10.11884/HPLPB202234.220052
Abstract:
Gas-liquid separation is the key to the success of an aerosol-type singlet oxygen generator. To solve the problem of gas-liquid separation, the idea of droplet size-controlled centrifugal separation was proposed that size-controlled droplets are produced by using an atomization technique and then during the reaction of the droplets with gas flow the gas-liquid separation is simultaneously done by a centrifugal force which is determined by the sizes of the droplets and generated by a set of high-speed rotating blades. To verify this idea, a twisted flow aerosol singlet oxygen generator (TFA-SOG) based on this idea was built and investigated through simulation and experiment. The investigation shows that the simulated gas-liquid separation efficiencies are consistent with the experimental ones and the idea is feasible; the emphasis on further development of TFA-SOGs should be put on the droplet size-controlled atomization technique.
Gas-liquid separation is the key to the success of an aerosol-type singlet oxygen generator. To solve the problem of gas-liquid separation, the idea of droplet size-controlled centrifugal separation was proposed that size-controlled droplets are produced by using an atomization technique and then during the reaction of the droplets with gas flow the gas-liquid separation is simultaneously done by a centrifugal force which is determined by the sizes of the droplets and generated by a set of high-speed rotating blades. To verify this idea, a twisted flow aerosol singlet oxygen generator (TFA-SOG) based on this idea was built and investigated through simulation and experiment. The investigation shows that the simulated gas-liquid separation efficiencies are consistent with the experimental ones and the idea is feasible; the emphasis on further development of TFA-SOGs should be put on the droplet size-controlled atomization technique.
2022,
34: 081006.
doi: 10.11884/HPLPB202234.220031
Abstract:
Optical component damage is one of the important factors that limit the improvement of laser flux level. To quickly and accurately detect whether optical component damage occurs and support the use of optical component cycle repair strategy, we proposed an optical component damage detection method based on acoustic emission technology. Whether the optical component is damaged was judged by studying the characteristics of acoustic emission signals generated by optical component damage. A time delay estimation algorithm based on quadratic correlation and fine interpolation of correlation peak (FICP) was developed. The feasibility of the algorithm was verified by simulation. Combined with the principle of time difference location, a method for solving the damage location was established and verified by experiments. The results show that the method can quickly obtain the damage location estimation from the monitoring signal. The average positioning error is 8.61 mm, and the average calculation time for positioning is 0.143 s. The method has the potential to be applied to on-line damage monitoring of large-aperture optical components.
Optical component damage is one of the important factors that limit the improvement of laser flux level. To quickly and accurately detect whether optical component damage occurs and support the use of optical component cycle repair strategy, we proposed an optical component damage detection method based on acoustic emission technology. Whether the optical component is damaged was judged by studying the characteristics of acoustic emission signals generated by optical component damage. A time delay estimation algorithm based on quadratic correlation and fine interpolation of correlation peak (FICP) was developed. The feasibility of the algorithm was verified by simulation. Combined with the principle of time difference location, a method for solving the damage location was established and verified by experiments. The results show that the method can quickly obtain the damage location estimation from the monitoring signal. The average positioning error is 8.61 mm, and the average calculation time for positioning is 0.143 s. The method has the potential to be applied to on-line damage monitoring of large-aperture optical components.
2022,
34: 081007.
doi: 10.11884/HPLPB202234.220065
Abstract:
The closed-loop accuracy of the optical-electric tracking system is one of the important technical index in the fields of reconnaissance and detection, laser communication, etc. Researchers usually use image stabilization techniques, inertial stabilization techniques, or overall self-stabilization techniques to improve the closed-loop accuracy. Inertial stabilization techniques has been widely used in photoelectric tracking system for its good stabilization effect. This paper adopts the method of comparative analysis to analyze the principle, compare the advantages and forecast the development prospect of the frame inertial stabilization, mirror inertial stabilization and inertial reference light stabilization techniques in the photoelectric tracking system. It is proposed that the composite axis inertial stabilization using multiple inertial stabilization techniques is still a development tendency in the near future.
The closed-loop accuracy of the optical-electric tracking system is one of the important technical index in the fields of reconnaissance and detection, laser communication, etc. Researchers usually use image stabilization techniques, inertial stabilization techniques, or overall self-stabilization techniques to improve the closed-loop accuracy. Inertial stabilization techniques has been widely used in photoelectric tracking system for its good stabilization effect. This paper adopts the method of comparative analysis to analyze the principle, compare the advantages and forecast the development prospect of the frame inertial stabilization, mirror inertial stabilization and inertial reference light stabilization techniques in the photoelectric tracking system. It is proposed that the composite axis inertial stabilization using multiple inertial stabilization techniques is still a development tendency in the near future.
2022,
34: 082001.
doi: 10.11884/HPLPB202234.220038
Abstract:
To meet the diagnostic requirements of physical experiments in the implosion compression and arrest stage, an optical design of Wolter-Ⅲ X-ray microscope with short focal length and high magnification satisfying the Abbe sine condition was proposed. This paper introduces, the structural characteristics and design method of Wolter type Ⅲ microscope in detail. Compared with Wolter typeⅠmicroscope, the focal length of the system can be reduced by moving the main plane to the direction of the object point, so as to obtain a larger magnification. The image quality matching between microscope and detector is realized to improve the spatial resolution of diagnostic system. It can be obtained by ray tracing that the spatial resolution is better than 3 μm in the field of view of ± 190 μm. The resolution is better than 5 μm in the field of view of ±240 μm. In the field of view of ±300 μm, the resolution is better than 8 μm. The geometric solid light angle is about 5×10−6 sr.
To meet the diagnostic requirements of physical experiments in the implosion compression and arrest stage, an optical design of Wolter-Ⅲ X-ray microscope with short focal length and high magnification satisfying the Abbe sine condition was proposed. This paper introduces, the structural characteristics and design method of Wolter type Ⅲ microscope in detail. Compared with Wolter typeⅠmicroscope, the focal length of the system can be reduced by moving the main plane to the direction of the object point, so as to obtain a larger magnification. The image quality matching between microscope and detector is realized to improve the spatial resolution of diagnostic system. It can be obtained by ray tracing that the spatial resolution is better than 3 μm in the field of view of ± 190 μm. The resolution is better than 5 μm in the field of view of ±240 μm. In the field of view of ±300 μm, the resolution is better than 8 μm. The geometric solid light angle is about 5×10−6 sr.
2022,
34: 082002.
doi: 10.11884/HPLPB202234.210353
Abstract:
The sedimentation characteristics of the magnetic polishing liquid in the magnetorheological polishing area is an important part of the material removal mechanism in the polishing process. Aiming at the ultra-large-scale nonlinear problem of numerical calculation of polishing powder sedimentation characteristics, this paper solves the ultra-large-scale fluid-structure interaction calculation problem based on Kahan linearization. The sedimentation characteristics of the multiphase flow of polishing powder composed of hydroxy iron powder and silicone oil in the polishing area under gradient magnetic field were studied. Taking the polishing powder composed of hydroxyl iron powder with mass fraction of 70% and particle size of 5um and silicone oil with viscosity of 0.973 Pa·s as the research object, sedimentation analysis of different polishing wheel rotation speeds, different embedding depths and different mass fractions of carbonyl iron powder were realized. It is found that the polishing powder in the magnetorheological polishing area will increase with the increase of the rotating speed of the polishing wheel; when it reaches the outlet, the distribution of the polishing powder tends to be stable; the polishing powder will increase with the increase of the embedded depth and there is a saturation zone; the mass fraction of hydroxy iron powder affects the sedimentation ability in a non-linear manner.
The sedimentation characteristics of the magnetic polishing liquid in the magnetorheological polishing area is an important part of the material removal mechanism in the polishing process. Aiming at the ultra-large-scale nonlinear problem of numerical calculation of polishing powder sedimentation characteristics, this paper solves the ultra-large-scale fluid-structure interaction calculation problem based on Kahan linearization. The sedimentation characteristics of the multiphase flow of polishing powder composed of hydroxy iron powder and silicone oil in the polishing area under gradient magnetic field were studied. Taking the polishing powder composed of hydroxyl iron powder with mass fraction of 70% and particle size of 5um and silicone oil with viscosity of 0.973 Pa·s as the research object, sedimentation analysis of different polishing wheel rotation speeds, different embedding depths and different mass fractions of carbonyl iron powder were realized. It is found that the polishing powder in the magnetorheological polishing area will increase with the increase of the rotating speed of the polishing wheel; when it reaches the outlet, the distribution of the polishing powder tends to be stable; the polishing powder will increase with the increase of the embedded depth and there is a saturation zone; the mass fraction of hydroxy iron powder affects the sedimentation ability in a non-linear manner.
2022,
34: 082203.
doi: 10.11884/HPLPB202234.220133
Abstract:
Aiming at the growth of ablative Rayleigh-Taylor instability with two perturbations, the evolutions of the amplitudes of high-order harmonics excited by two-mode coupling under different preheating conditions are studied by using a high-precision numerical simulation method. When the fundamental modes are a long-wavelength and a short-wavelength mode, the long-wavelength modes of the excited harmonics are dominant, while the development of short-wavelength modes are obviously suppressed; when the fundamental modes are two short-wavelength modes, many fast-growing and long-wavelength modes are excited, and the growth of short-wavelength modes are in the form of small oscillation. By comparing the two different two-mode coupling cases, it is found that the long-wavelength structures are dominant in the weakly nonlinear stage. Especially, in the two short-wavelength modes coupling case, the bubbles and spikes show long-wavelength structures which are different from the two fundamental modes. By further comparing the three preheating ablative effects, it is found that the higher the preheat degree is, the more the coupled harmonics growth will be weakened. It is of great significance to control the development of ablative Rayleigh-Taylor instability in inertial confinement fusion engineering.
Aiming at the growth of ablative Rayleigh-Taylor instability with two perturbations, the evolutions of the amplitudes of high-order harmonics excited by two-mode coupling under different preheating conditions are studied by using a high-precision numerical simulation method. When the fundamental modes are a long-wavelength and a short-wavelength mode, the long-wavelength modes of the excited harmonics are dominant, while the development of short-wavelength modes are obviously suppressed; when the fundamental modes are two short-wavelength modes, many fast-growing and long-wavelength modes are excited, and the growth of short-wavelength modes are in the form of small oscillation. By comparing the two different two-mode coupling cases, it is found that the long-wavelength structures are dominant in the weakly nonlinear stage. Especially, in the two short-wavelength modes coupling case, the bubbles and spikes show long-wavelength structures which are different from the two fundamental modes. By further comparing the three preheating ablative effects, it is found that the higher the preheat degree is, the more the coupled harmonics growth will be weakened. It is of great significance to control the development of ablative Rayleigh-Taylor instability in inertial confinement fusion engineering.
2022,
34: 083001.
doi: 10.11884/HPLPB202234.220037
Abstract:
The development of reflectarray antenna is limited by bandwidth and power capacity. In this paper, a novel reflectarray element based on multi-resonant technique is proposed firstly. Compared with the traditional element, the proposed element structure has the characteristics of high-power capacity, low profile, and good linearity of phase shift curve. Secondly, a reflectarray antenna with 20 × 20 elements is designed in Ka band by using the proposed element and optimizing the array characteristics. Finally, the electromagnetic simulation software is used to simulate the antenna, The results show that at the center frequency of 35 GHz, the peak gain of the antenna is 27.58 dB, the aperture efficiency is 52.33%, the sidelobe is less than −16.08 dB, and the antenna gain drop is less than 3 dB in the frequency range of 30.41−39.64 GHz (the relative bandwidth is 26.37%). Moreover, the power capacity of the designed reflectarray reaches 13.99 MW and the power density is 218.54 W/mm2.
The development of reflectarray antenna is limited by bandwidth and power capacity. In this paper, a novel reflectarray element based on multi-resonant technique is proposed firstly. Compared with the traditional element, the proposed element structure has the characteristics of high-power capacity, low profile, and good linearity of phase shift curve. Secondly, a reflectarray antenna with 20 × 20 elements is designed in Ka band by using the proposed element and optimizing the array characteristics. Finally, the electromagnetic simulation software is used to simulate the antenna, The results show that at the center frequency of 35 GHz, the peak gain of the antenna is 27.58 dB, the aperture efficiency is 52.33%, the sidelobe is less than −16.08 dB, and the antenna gain drop is less than 3 dB in the frequency range of 30.41−39.64 GHz (the relative bandwidth is 26.37%). Moreover, the power capacity of the designed reflectarray reaches 13.99 MW and the power density is 218.54 W/mm2.
2022,
34: 083002.
doi: 10.11884/HPLPB202234.220019
Abstract:
Ensuring the reliability of integrated circuits (ICs) has been a great challenge with the increasing complexity of the electromagnetic environment. On this basis, the fast-rising-edge electromagnetic pulse (EMP)-induced trap-assisted tunneling (TAT) effect is investigated by simulation and experiments of CMOS digital inverters. A detailed mechanism analysis is performed to explain the physical damage process. The EMP-induced field derives traps and leakage current in the oxide, which induces output degradation and thermal failure in the device. A theoretical model of degradation and failure is established to describe the dependency of the output deterioration and the heat accumulation on the EMP resulting signal features. The temperature distribution function is derived from the heat conduction equation in the semiconductor. Corresponding experiments performed based on the TLP test system substantiate the emerging performance deterioration, which is in agreement with the mechanism analysis. Simulated results from the Sentaurus TCAD indicate that EMP resulting voltage-induced damage is caused by the TAT current path occurring in the gate oxide, revealing the location susceptible to burnout. In addition, the dependency of the device failure on the pulse rising time is discussed. The mechanism analysis in this paper facilitates reinforcing the design and promotes EMP reliability research on other semiconductor devices, and the study contributes to the enhancement of EMP robustness in CMOS digital ICs.
2022,
34: 084001.
doi: 10.11884/HPLPB202234.210561
Abstract:
Laser tracker is the primary instrument used for carrying out three-dimensional position measurement in accelerator alignment. Theoretically, three-dimensional measuring data processed by three-dimensional adjustment is more rigorous, however, error accumulation is found in practice, especially in elevation direction, the error accumulation is very obvious. To control the elevation error accumulation of three-dimensional adjustment, a method using the geoid as a datum in the measurement and data processing is researched. The principle is to get the elevation measuring data based on the geoid and use the elevation data to construct the constraints equation then carry out the three-dimensional adjustment with elevation constraints. Take the laser tracker as an example, a three-dimensional adjustment function model is given, the construction method of the constraints equation is researched and the calculation formulas of the three-dimensional adjustment is derived. Two application methods of the three-dimensional adjustment function model with elevation constraints are studied and the effects in controlling the elevation error accumulation are showed by simulations. Finally, a group of measuring data are calculated and compared with various adjustment methods, the results show that the three-dimensional adjustment with elevation constraints can control the elevation error accumulation more effectively than the one without elevation constraints.
Laser tracker is the primary instrument used for carrying out three-dimensional position measurement in accelerator alignment. Theoretically, three-dimensional measuring data processed by three-dimensional adjustment is more rigorous, however, error accumulation is found in practice, especially in elevation direction, the error accumulation is very obvious. To control the elevation error accumulation of three-dimensional adjustment, a method using the geoid as a datum in the measurement and data processing is researched. The principle is to get the elevation measuring data based on the geoid and use the elevation data to construct the constraints equation then carry out the three-dimensional adjustment with elevation constraints. Take the laser tracker as an example, a three-dimensional adjustment function model is given, the construction method of the constraints equation is researched and the calculation formulas of the three-dimensional adjustment is derived. Two application methods of the three-dimensional adjustment function model with elevation constraints are studied and the effects in controlling the elevation error accumulation are showed by simulations. Finally, a group of measuring data are calculated and compared with various adjustment methods, the results show that the three-dimensional adjustment with elevation constraints can control the elevation error accumulation more effectively than the one without elevation constraints.
2022,
34: 084002.
doi: 10.11884/HPLPB202234.210512
Abstract:
This paper focuses on the calibration of the quadrupole of CSNS about determination of the center of the devices, analyzes the standard deviation values of magnetic center and rotation center obtained by the magnetic measuring platform, and the one of rotation center and mechanical center after the calibration of each magnet twice. The results show that the standard deviation of magnetic center and rotation center of the quadrupole obtained by the magnetic measuring platform is 0.1 mm, the repeatability accuracy after the calibration of the rotation center and the mechanical center of the CSNS quadrupole twice is within 0.03 mm, and the standard value of the deviation between the rotation and the mechanical center is 0.1 mm. Therefore, if the magnet center calibration cannot be carried out for similar devices of the same accuracy, the calibration based on rotation center instead of mechanical center, with deviation correction of rotation center and magnetic center, can meet the accuracy requirements of the current equipment alignment. This study provides important reference and guidance for the calibration of similar devices in the future.
This paper focuses on the calibration of the quadrupole of CSNS about determination of the center of the devices, analyzes the standard deviation values of magnetic center and rotation center obtained by the magnetic measuring platform, and the one of rotation center and mechanical center after the calibration of each magnet twice. The results show that the standard deviation of magnetic center and rotation center of the quadrupole obtained by the magnetic measuring platform is 0.1 mm, the repeatability accuracy after the calibration of the rotation center and the mechanical center of the CSNS quadrupole twice is within 0.03 mm, and the standard value of the deviation between the rotation and the mechanical center is 0.1 mm. Therefore, if the magnet center calibration cannot be carried out for similar devices of the same accuracy, the calibration based on rotation center instead of mechanical center, with deviation correction of rotation center and magnetic center, can meet the accuracy requirements of the current equipment alignment. This study provides important reference and guidance for the calibration of similar devices in the future.
2022,
34: 084003.
doi: 10.11884/HPLPB202234.210514
Abstract:
In response to the demand for PET medical radionuclides in nuclear medicine diagnosis and treatment, China Institute of Atomic Energy is conducting research on the industrialization of PET medical small cyclotrons. Magnetic field measurement and shimming is the key point in the production of cyclotrons. The compact structure of small cyclotron is a difficulty to realize the full automatic control of magnetic field measuring instrument and solving the problems of high processing cost and long cycle of conventional shimming method is the key to industrialized production. This article will introduce in detail the development of a fully automated magnetic field measurement and precision shimming platform for small cyclotrons. Through the magnetic field measurement and shimming practice of multiple small cyclotrons, a set of rapid magnetic field measurement and shimming procedures will be developed to realize fully automatic measurement method to shorten the magnetic field measurement cycle and reduce the time of shimming by precision shimming algorithm. Under the condition of ensuring high efficiency and high quality of magnetic field measurement and shimming, the time and the processing cost are greatly reduced, which lays a foundation for the industrialized production of small cyclotrons. At present, the China Institute of Atomic Energy has completed the commercialization of several small cyclotrons.
In response to the demand for PET medical radionuclides in nuclear medicine diagnosis and treatment, China Institute of Atomic Energy is conducting research on the industrialization of PET medical small cyclotrons. Magnetic field measurement and shimming is the key point in the production of cyclotrons. The compact structure of small cyclotron is a difficulty to realize the full automatic control of magnetic field measuring instrument and solving the problems of high processing cost and long cycle of conventional shimming method is the key to industrialized production. This article will introduce in detail the development of a fully automated magnetic field measurement and precision shimming platform for small cyclotrons. Through the magnetic field measurement and shimming practice of multiple small cyclotrons, a set of rapid magnetic field measurement and shimming procedures will be developed to realize fully automatic measurement method to shorten the magnetic field measurement cycle and reduce the time of shimming by precision shimming algorithm. Under the condition of ensuring high efficiency and high quality of magnetic field measurement and shimming, the time and the processing cost are greatly reduced, which lays a foundation for the industrialized production of small cyclotrons. At present, the China Institute of Atomic Energy has completed the commercialization of several small cyclotrons.
2022,
34: 084004.
doi: 10.11884/HPLPB202234.210553
Abstract:
The fluctuation of power grid has a great influence on the normal operation of Shanghai Synchrotron Radiation Facility (SSRF) accelerator. The study first introduces the causes of power grid fluctuation and its impact on SSRF in order to solve this problem. Through the analysis of former cases, the basic recovery process of SSRF accelerator affected by power grid fluctuation is sorted out and optimized. This paper also analyzes the different performance of each hardware system in the face of the power grid fluctuation. In addition, it discusses how to optimize the processing flow and establish a perfect machine recovery program. Several suggestions and measures are put forward in response to the fluctuation of the external power grid, so as to minimize the impact of the power grid fluctuation on key equipment such as cryogenic compressor and superconducting radio-frequency cavity, shorten the actual failure time, speed up the machine recovery, and ensure the stable operation of SSRF. Based on the operation data in the past ten years, it is found that there are several important thresholds for the impact of power grid fluctuations on SSRF, and these thresholds have an indicator effect on machine recovery. The secondary faults that are caused by voltage sags are analyzed and discussed in this paper, and some guidance and suggestions are put forward.
The fluctuation of power grid has a great influence on the normal operation of Shanghai Synchrotron Radiation Facility (SSRF) accelerator. The study first introduces the causes of power grid fluctuation and its impact on SSRF in order to solve this problem. Through the analysis of former cases, the basic recovery process of SSRF accelerator affected by power grid fluctuation is sorted out and optimized. This paper also analyzes the different performance of each hardware system in the face of the power grid fluctuation. In addition, it discusses how to optimize the processing flow and establish a perfect machine recovery program. Several suggestions and measures are put forward in response to the fluctuation of the external power grid, so as to minimize the impact of the power grid fluctuation on key equipment such as cryogenic compressor and superconducting radio-frequency cavity, shorten the actual failure time, speed up the machine recovery, and ensure the stable operation of SSRF. Based on the operation data in the past ten years, it is found that there are several important thresholds for the impact of power grid fluctuations on SSRF, and these thresholds have an indicator effect on machine recovery. The secondary faults that are caused by voltage sags are analyzed and discussed in this paper, and some guidance and suggestions are put forward.
2022,
34: 084005.
doi: 10.11884/HPLPB202234.220030
Abstract:
The Hefei Advanced Light Facility (HALF), which includes an injector and a Diffraction Limited Storage Ring (DLSR), needs ultrahigh vacuum environment to satisfy the lifetime of beam. The small-diameter vacuum chamber coated with NEG (Non-Evaporable Getter) not only saves space, but also has a high pumping speed, which can well meet the demand of obtaining ultra-high vacuum in diffraction-limited devices. The NEG films need to be activated at a certain temperature to get the pumping speed. Therefore, the NEG film activation method and process is important to ensure the safety of the other system components, such as the magnets. Based on the appropriate activation temperature of the coated NEG films, a temperature analysis model was applied to simulate the temperature distribution of the NEG coated vacuum chamber and the magnet during in-situ activation at the temperatures of 180 ℃ and 200 ℃, respectively. The oxygen-free silver bearing copper (OFS) vacuum tubes were baked out by polyimide (PI) heaters and the temperature of the tube and the magnet pole was measured. The maximum temperature measured at the magnet pole was about 40 ℃, which confirmed the safety of the quadrupole magnet. This work will be a solution and basis of in-situ activation of the NEG-coated vacuum chamber in the Hefei Advanced Light Facility.
The Hefei Advanced Light Facility (HALF), which includes an injector and a Diffraction Limited Storage Ring (DLSR), needs ultrahigh vacuum environment to satisfy the lifetime of beam. The small-diameter vacuum chamber coated with NEG (Non-Evaporable Getter) not only saves space, but also has a high pumping speed, which can well meet the demand of obtaining ultra-high vacuum in diffraction-limited devices. The NEG films need to be activated at a certain temperature to get the pumping speed. Therefore, the NEG film activation method and process is important to ensure the safety of the other system components, such as the magnets. Based on the appropriate activation temperature of the coated NEG films, a temperature analysis model was applied to simulate the temperature distribution of the NEG coated vacuum chamber and the magnet during in-situ activation at the temperatures of 180 ℃ and 200 ℃, respectively. The oxygen-free silver bearing copper (OFS) vacuum tubes were baked out by polyimide (PI) heaters and the temperature of the tube and the magnet pole was measured. The maximum temperature measured at the magnet pole was about 40 ℃, which confirmed the safety of the quadrupole magnet. This work will be a solution and basis of in-situ activation of the NEG-coated vacuum chamber in the Hefei Advanced Light Facility.
2022,
34: 084006.
doi: 10.11884/HPLPB202234.220044
Abstract:
A new DBPM electronics system based on pilot tone is introduced in this paper to improve the traditional DBPM electronics system which is affected by the non-linearity of electronic channel, temperature drift and system noise.The hardware of the electronics consists of analog signal acquisition electronics, digital signal processing electronics and pilot tone combiner electronics. The software consists of application software and firmware.The beam signal and pilot tone signal are coupled in the pilot tone combiner, and then the combined signal processed by electronic hardware board, and finally calculated by FPGA(Field Programmable Gate Array) to obtain the normalized beam position information. The electronics was tested in the laboratory and it is shown that the normalized pilot tone can effectively educe the measurement variation with temperature of each channel. After normalization, the accuracy the channel changing with temperature is effectively improved. The beam position drift is improved from 4.5 μm to 0.5 μm, and the resolution is improved from 57.25 nm to 13.37 nm. And the pilot tone switching experiment can show intuitively the effect of the pilot signal on the beam position measurement of online correction. The design of DBPM electronics based on pilot tone can realize online correction of beam position measurement efficiently and in real time, and improve the real-time resolution performance of the electronics system.
A new DBPM electronics system based on pilot tone is introduced in this paper to improve the traditional DBPM electronics system which is affected by the non-linearity of electronic channel, temperature drift and system noise.The hardware of the electronics consists of analog signal acquisition electronics, digital signal processing electronics and pilot tone combiner electronics. The software consists of application software and firmware.The beam signal and pilot tone signal are coupled in the pilot tone combiner, and then the combined signal processed by electronic hardware board, and finally calculated by FPGA(Field Programmable Gate Array) to obtain the normalized beam position information. The electronics was tested in the laboratory and it is shown that the normalized pilot tone can effectively educe the measurement variation with temperature of each channel. After normalization, the accuracy the channel changing with temperature is effectively improved. The beam position drift is improved from 4.5 μm to 0.5 μm, and the resolution is improved from 57.25 nm to 13.37 nm. And the pilot tone switching experiment can show intuitively the effect of the pilot signal on the beam position measurement of online correction. The design of DBPM electronics based on pilot tone can realize online correction of beam position measurement efficiently and in real time, and improve the real-time resolution performance of the electronics system.
2022,
34: 084007.
doi: 10.11884/HPLPB202234.220014
Abstract:
Linac injector is a major sub-system of the proton therapy facility. Due to schedule consideration, the Shanghai advance proton therapy facility APTRON uses a linac injector made by ACCSYS in California, USA. Now, we have developed a linac injector made up of Electron Cyclotron Resonance (ECR) ion source and 4-vane Radio Frequency Quadrupole (RFQ), as well as alternating-phase-focused (APF) Drift Tube Linac (DTL), which is a significant technological innovation. During the last 5 years, we have finished a series of R&D stage including physical design, electromagnetic design, mechanical design, assembly and alignment, cavity cold test, RF conditioning and beam commissioning. Finally, we get 7 mA, 7 MeV proton beam from the down stream Faraday cup. According to the measurement of our beam diagnostic and analysis system, the center energy of the beam is 6.975 MeV, the beam intensity within ±0.35% momentum spread is 6.07 mA.
Linac injector is a major sub-system of the proton therapy facility. Due to schedule consideration, the Shanghai advance proton therapy facility APTRON uses a linac injector made by ACCSYS in California, USA. Now, we have developed a linac injector made up of Electron Cyclotron Resonance (ECR) ion source and 4-vane Radio Frequency Quadrupole (RFQ), as well as alternating-phase-focused (APF) Drift Tube Linac (DTL), which is a significant technological innovation. During the last 5 years, we have finished a series of R&D stage including physical design, electromagnetic design, mechanical design, assembly and alignment, cavity cold test, RF conditioning and beam commissioning. Finally, we get 7 mA, 7 MeV proton beam from the down stream Faraday cup. According to the measurement of our beam diagnostic and analysis system, the center energy of the beam is 6.975 MeV, the beam intensity within ±0.35% momentum spread is 6.07 mA.
2022,
34: 085001.
doi: 10.11884/HPLPB202234.220103
Abstract:
Pressure and temperature are two of the most critical factors in the study of material properties. The magnetically driving device has the ability of pressure regulation, but does not have the sample cooling control technology temporarily in our country. Therefore, a set of cooling system matching with the loading area of the magnetically driving device is designed. Combined with the designed electrode plate structure and the test probe, the electrode plate and the probe in the load area are fixed in the right position. The purpose of cooling the sample is achieved by injecting compressed low-temperature liquid nitrogen into the closed gas chamber formed by the electrode plate and the probe tooling. Through the vacuum pump, the air in the closed air chamber formed by the electrode plate and the probe tooling is extracted to avoid failure of the velocity measuring probe due to the water vapor in the low-temperature condensed air. Based on the system, the ramp wave compression experiment of bismuth at low temperature is carried out, and the dynamic response data of bismuth at the initial temperature of − 80 ℃ are obtained, which verifies the reliability of the cooling system.
Pressure and temperature are two of the most critical factors in the study of material properties. The magnetically driving device has the ability of pressure regulation, but does not have the sample cooling control technology temporarily in our country. Therefore, a set of cooling system matching with the loading area of the magnetically driving device is designed. Combined with the designed electrode plate structure and the test probe, the electrode plate and the probe in the load area are fixed in the right position. The purpose of cooling the sample is achieved by injecting compressed low-temperature liquid nitrogen into the closed gas chamber formed by the electrode plate and the probe tooling. Through the vacuum pump, the air in the closed air chamber formed by the electrode plate and the probe tooling is extracted to avoid failure of the velocity measuring probe due to the water vapor in the low-temperature condensed air. Based on the system, the ramp wave compression experiment of bismuth at low temperature is carried out, and the dynamic response data of bismuth at the initial temperature of − 80 ℃ are obtained, which verifies the reliability of the cooling system.
2022,
34: 085002.
doi: 10.11884/HPLPB202234.210573
Abstract:
The 200 keV X-ray pulser has a good surface density resolution when being used in the imaging diagnosis of high speed and low density regions in ejecta. Heuce it has become one of the important technical diagnostics methods of ejecta. This papper develops a 200 keV pulse driver based on the PFN-Marx technology. Using a pre-trigger method, the 200 kV pulse of a 62 ns width and a 25 ns rise time is produced on the 40 Ω water resistance, A “Washer-Needle” type diode which can work under 200 kV voltage is also designed. When the diode operating voltage is 210 kV, the pulser outputs the X-ray pulse of a 40 ns width, a 1.2 mm spot size and a 15 mR dose at 1 m distance .
The 200 keV X-ray pulser has a good surface density resolution when being used in the imaging diagnosis of high speed and low density regions in ejecta. Heuce it has become one of the important technical diagnostics methods of ejecta. This papper develops a 200 keV pulse driver based on the PFN-Marx technology. Using a pre-trigger method, the 200 kV pulse of a 62 ns width and a 25 ns rise time is produced on the 40 Ω water resistance, A “Washer-Needle” type diode which can work under 200 kV voltage is also designed. When the diode operating voltage is 210 kV, the pulser outputs the X-ray pulse of a 40 ns width, a 1.2 mm spot size and a 15 mR dose at 1 m distance .
2022,
34: 085003.
doi: 10.11884/HPLPB202234.210533
Abstract:
An atmospheric pressure helium plasma jet with a coaxial dual-channel inlet under single electrode structure (stainless steel needle tube) and double electrode structure (stainless steel needle tube—high voltage ring electrode) is comparatively studied using a two-dimensional axisymmetric fluid model. The study shows that compared with the single electrode structure, the propagation velocity of the jet decreases significantly under the double electrode structure, and decreases more in the dielectric tube. Meanwhile, the spatial structure of the jet changes significantly under the double electrode structure. Under the single electrode structure, the jet structure changes from a donut-shaped hollow structure to a solid disk-shaped structure with its development; while under the double electrode structure, a transformation process from a solid disk-shaped structure to a donut-shaped hollow structure and then to a solid disk-shaped structure is shown, which improves the uniformity of the jet spatial distribution. The effect of high-voltage ring electrode thickness on jet under the double electrode structure is also investigated. It is shown that as the ring electrode thickness increases, the jet propagation velocity decreases further and the jet channel shrinks radially, and the inner diameter of the jet with the donut-shaped hollow structure decreases, which improves the uniformity of the radial distribution of the jet.
An atmospheric pressure helium plasma jet with a coaxial dual-channel inlet under single electrode structure (stainless steel needle tube) and double electrode structure (stainless steel needle tube—high voltage ring electrode) is comparatively studied using a two-dimensional axisymmetric fluid model. The study shows that compared with the single electrode structure, the propagation velocity of the jet decreases significantly under the double electrode structure, and decreases more in the dielectric tube. Meanwhile, the spatial structure of the jet changes significantly under the double electrode structure. Under the single electrode structure, the jet structure changes from a donut-shaped hollow structure to a solid disk-shaped structure with its development; while under the double electrode structure, a transformation process from a solid disk-shaped structure to a donut-shaped hollow structure and then to a solid disk-shaped structure is shown, which improves the uniformity of the jet spatial distribution. The effect of high-voltage ring electrode thickness on jet under the double electrode structure is also investigated. It is shown that as the ring electrode thickness increases, the jet propagation velocity decreases further and the jet channel shrinks radially, and the inner diameter of the jet with the donut-shaped hollow structure decreases, which improves the uniformity of the radial distribution of the jet.
2022,
34: 086001.
doi: 10.11884/HPLPB202234.220084
Abstract:
For small modular reactors, containment suppression devices can be used to limit the rapid increasement of temperature and pressure in the containment caused by loss of coolant accidents (LOCAs). However, temperature stratification may occur in the suppression pool with the change of the mass flow flux and water temperature during the process of discharge, which reduces the heat and mass transfer. In this paper, an experimental facility for temperature stratification of suppression pool is established. The effects of steam mass flow flux, submerged depth of sparger and gas-water volume ratio on the temperature stratification characteristics in the pool are studied. Results show that there is temperature stratification in the pool at a wide range of steam mass flow flux. With the increase of mass flow flux, the influence on stratification is weakened, and the thermal interface moves down, leading to more water participating in heat exchange. With the increase of the submerged depth of sparger, the position of thermal interface moves down and the stirring effect of water is enhanced. As the gas-water volume ratio increases, the thermal interface moves down and the disturbed area enlarges.
For small modular reactors, containment suppression devices can be used to limit the rapid increasement of temperature and pressure in the containment caused by loss of coolant accidents (LOCAs). However, temperature stratification may occur in the suppression pool with the change of the mass flow flux and water temperature during the process of discharge, which reduces the heat and mass transfer. In this paper, an experimental facility for temperature stratification of suppression pool is established. The effects of steam mass flow flux, submerged depth of sparger and gas-water volume ratio on the temperature stratification characteristics in the pool are studied. Results show that there is temperature stratification in the pool at a wide range of steam mass flow flux. With the increase of mass flow flux, the influence on stratification is weakened, and the thermal interface moves down, leading to more water participating in heat exchange. With the increase of the submerged depth of sparger, the position of thermal interface moves down and the stirring effect of water is enhanced. As the gas-water volume ratio increases, the thermal interface moves down and the disturbed area enlarges.
2022,
34: 086002.
doi: 10.11884/HPLPB202234.220055
Abstract:
Neutron capture γ-rays from nitrogen is an important part of initial nuclear radiation. To accurately calculate the early nuclear radiation, the Monte Carlo computing model for the neutron and secondary γ-rays transport in the atmosphere is established. Some variance reduction techniques, such as geometric splitting algorithm and time splitting algorithm are used in the Monte Carlo method to improve computing efficiency. The neutron and secondary γ-rays information on the spherical surface at different distances are calculated. The energy release rates of capture γ-rays from nitrogen at different positions and at different times are given. The regularity of the energy release rate of capture γ-rays from nitrogen is studied, and the influence of neutron energy on capture γ-rays from nitrogen is analyzed. The results show that the energy release rate of capture γ from nitrogen increases with the increase of distance from the source at first, reaches the peak at about 500 m from the source, and then decreases exponentially with the increase of distance. The energy release rate of capture γ-rays from nitrogen obeys exponential decay law in time, and the decay time is about 0.1 s. By introducing the parameter of a representing the radiation intensity and the characteristic attenuation time parameter of τ, a fast calculation formula for the energy release rate of capture γ-rays from nitrogen at different distances and times is obtained by fitting formulas. Results show that the intensity radiation, the decay time scale of capture γ-rays from nitrogen and their spatial distribution are closely related to neutron energy.
Neutron capture γ-rays from nitrogen is an important part of initial nuclear radiation. To accurately calculate the early nuclear radiation, the Monte Carlo computing model for the neutron and secondary γ-rays transport in the atmosphere is established. Some variance reduction techniques, such as geometric splitting algorithm and time splitting algorithm are used in the Monte Carlo method to improve computing efficiency. The neutron and secondary γ-rays information on the spherical surface at different distances are calculated. The energy release rates of capture γ-rays from nitrogen at different positions and at different times are given. The regularity of the energy release rate of capture γ-rays from nitrogen is studied, and the influence of neutron energy on capture γ-rays from nitrogen is analyzed. The results show that the energy release rate of capture γ from nitrogen increases with the increase of distance from the source at first, reaches the peak at about 500 m from the source, and then decreases exponentially with the increase of distance. The energy release rate of capture γ-rays from nitrogen obeys exponential decay law in time, and the decay time is about 0.1 s. By introducing the parameter of a representing the radiation intensity and the characteristic attenuation time parameter of τ, a fast calculation formula for the energy release rate of capture γ-rays from nitrogen at different distances and times is obtained by fitting formulas. Results show that the intensity radiation, the decay time scale of capture γ-rays from nitrogen and their spatial distribution are closely related to neutron energy.
