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RSS2021 Vol. 33, No. 4
Recommend Articles
2021, 33: 045001.
doi: 10.11884/HPLPB202133.210069
2021, 33: 046002.
doi: 10.11884/HPLPB202133.200280
Display Method:
2021,
: 1-2.
2021,
33: 041001.
doi: 10.11884/HPLPB202133.200317
Abstract:
The single-layer SiO2 chemical films prepared by sol-gel technology were modified with different amounts of ammonia-hexamethyldisilazane (HMDS) atmosphere at room temperature, and then the anti-pollution porformance of the chemical films for dibutyl phthalate (DBP) contamination were tested under low vacuum condition. In addition, the ultraviolet-visible-near-infrared spectrophotometer UV-Vis-NIR), infrared spectrometer and atomic force microscope were used to analyze the evolution of chemical film characteristics before and after modification. The results show that after DBP contamination, the peak transmittance of the chemical film modified by 15−30 mL ammonia-HMDS is 99.8%, which is increased by 3.5% compared with that of the chemical film before modification. At this time, the chemical films have excellent anti-pollution properties. Although the ammonia-HMDS treatment can significantly enhance the anti-pollution performance of DBP contamination of the chemical film, excessive amount of ammonia-HMDS will lead to the laser damage threshold of the chemical film to decrease from 24.3 J/cm2 to 19.3 J/cm2. The research is helpful to optimize the process parameters to improve the anti-pollution performance of the chemical film, which has great significance for practical engineering applications.
The single-layer SiO2 chemical films prepared by sol-gel technology were modified with different amounts of ammonia-hexamethyldisilazane (HMDS) atmosphere at room temperature, and then the anti-pollution porformance of the chemical films for dibutyl phthalate (DBP) contamination were tested under low vacuum condition. In addition, the ultraviolet-visible-near-infrared spectrophotometer UV-Vis-NIR), infrared spectrometer and atomic force microscope were used to analyze the evolution of chemical film characteristics before and after modification. The results show that after DBP contamination, the peak transmittance of the chemical film modified by 15−30 mL ammonia-HMDS is 99.8%, which is increased by 3.5% compared with that of the chemical film before modification. At this time, the chemical films have excellent anti-pollution properties. Although the ammonia-HMDS treatment can significantly enhance the anti-pollution performance of DBP contamination of the chemical film, excessive amount of ammonia-HMDS will lead to the laser damage threshold of the chemical film to decrease from 24.3 J/cm2 to 19.3 J/cm2. The research is helpful to optimize the process parameters to improve the anti-pollution performance of the chemical film, which has great significance for practical engineering applications.
2021,
33: 042001.
doi: 10.11884/HPLPB202133.200243
Abstract:
Based on the flow theory applicable to the whole Knudsen number range, a theoretical model for removing air from the target shot in inertial confinement fusion was established, and the reliability of the model was verified by designed experiments. The physical experiment requires the air concentration in the target shot to be lower than 10×10−6, the process of removing air in the target shot was simulated numerically, and the relationship between the air concentration in the target shot, the pressure in the target shot and time was emphatically analyzed. The time cost of three methods for removing the air in the target shot, namely the single-pipe one-time gas evacuation method, the single-pipe circulation gas evacuation method and the double-pipe flow washing method, were calculated and compared. Numerical calculation results show that: in the single-pipe one-time gas evacuation method, the existence of the micro-channel on the target shot has a non-negligible effect on the time required to remove the air in the target shot, and it takes 1961.77 h to make the air concentration in the target shot reach the standard when the micro-channel on the target shot and the gas-filling pipe is considered. In the single-pipe cycle gas evacuation method, the number of evacuation times and the degree of single gas evacuation will affect the total time required to remove the air in the target shot. When the single gas evacuation degree is at the optimal value, the plan that filling three times and evacuation four times can reduce the total time to reach the standard to about 1 h, while the single gas filling and gas evacuation times under this plan are 6 min and 10 min, respectively. However, it only takes 11 minutes to make the air concentration in the target shot reach the standard by using the double-pipe flow washing method.
Based on the flow theory applicable to the whole Knudsen number range, a theoretical model for removing air from the target shot in inertial confinement fusion was established, and the reliability of the model was verified by designed experiments. The physical experiment requires the air concentration in the target shot to be lower than 10×10−6, the process of removing air in the target shot was simulated numerically, and the relationship between the air concentration in the target shot, the pressure in the target shot and time was emphatically analyzed. The time cost of three methods for removing the air in the target shot, namely the single-pipe one-time gas evacuation method, the single-pipe circulation gas evacuation method and the double-pipe flow washing method, were calculated and compared. Numerical calculation results show that: in the single-pipe one-time gas evacuation method, the existence of the micro-channel on the target shot has a non-negligible effect on the time required to remove the air in the target shot, and it takes 1961.77 h to make the air concentration in the target shot reach the standard when the micro-channel on the target shot and the gas-filling pipe is considered. In the single-pipe cycle gas evacuation method, the number of evacuation times and the degree of single gas evacuation will affect the total time required to remove the air in the target shot. When the single gas evacuation degree is at the optimal value, the plan that filling three times and evacuation four times can reduce the total time to reach the standard to about 1 h, while the single gas filling and gas evacuation times under this plan are 6 min and 10 min, respectively. However, it only takes 11 minutes to make the air concentration in the target shot reach the standard by using the double-pipe flow washing method.
2021,
33: 043001.
doi: 10.11884/HPLPB202133.200327
Abstract:
A highly selective tunable filter with switchable bandpass (BP)-to- bandstop (BS) frequency response is designed. The frequency of the filter can be adjusted by loading a varactor diode on the end of microstrip resonator and branch; a PIN diode can be used to switch BP and BS characteristics. The filter is analyzed using the even- and odd-mode method, and constant absolute bandwidth (CABW) is achieved. Then, a source and load coupling is introduced so that there is a transmission zero (TZ) on each side of band, which can be almost keep in the same relative position throughout the frequency tuning range (FTR). Therefore, in the FTR, the filter achieves high selectivity and good out-of-band suppression characteristics. The FTR of the proposed filter is 5.58～5.89 GHz, the measured attenuation within the stopband is greater than 14 dB with CABW of (80±5) MHz under BS state; the FTR is 5.42−5.79 GHz, CABW is (120±5) MHz, the measured return loss and insertion loss within the passband are about 13 dB and 1.69−2.25 dB under BP state, respectively. Moreover, the fabricated tunable filter has a compact size of 0.28λg×0.62λg (λg is the wavelength of the center frequency during the FTR). The experimental and simulated results are in good agreement.
A highly selective tunable filter with switchable bandpass (BP)-to- bandstop (BS) frequency response is designed. The frequency of the filter can be adjusted by loading a varactor diode on the end of microstrip resonator and branch; a PIN diode can be used to switch BP and BS characteristics. The filter is analyzed using the even- and odd-mode method, and constant absolute bandwidth (CABW) is achieved. Then, a source and load coupling is introduced so that there is a transmission zero (TZ) on each side of band, which can be almost keep in the same relative position throughout the frequency tuning range (FTR). Therefore, in the FTR, the filter achieves high selectivity and good out-of-band suppression characteristics. The FTR of the proposed filter is 5.58～5.89 GHz, the measured attenuation within the stopband is greater than 14 dB with CABW of (80±5) MHz under BS state; the FTR is 5.42−5.79 GHz, CABW is (120±5) MHz, the measured return loss and insertion loss within the passband are about 13 dB and 1.69−2.25 dB under BP state, respectively. Moreover, the fabricated tunable filter has a compact size of 0.28λg×0.62λg (λg is the wavelength of the center frequency during the FTR). The experimental and simulated results are in good agreement.
2021,
33: 043002.
doi: 10.11884/HPLPB202133.200331
Abstract:
The design concept of employing the dynamically reconfigurable scattering pattern to enhance radar cross-section is proposed and examined. In combination with varactor loading, a physical unit cell geometry with an embedded bias network for the varactors is utilized to build the metasurface. Biased by an applied direct-current source with voltage gradient, the proposed active metasurface can exhibit electrically tunable reflection phase distributions for either normal or oblique incidence plane wave, so as to achieve flexible redirection of the angle of reflection. As a result, the agile effect for monostatic or bistatic cross-section enhancement is then facilitated. Taking a conducting plate as an example, three different incidence and reflection scenarios are considered for calculation and full-wave simulation. Reconfigurable scattering patterns produced at the operating frequency of 10 GHz by the presented design are observed, which indicates its capability of real-time control of the angle of reflection. In conjunction with an experimental measurement, the effective enhancement of monostatic and bistatic cross-sections are validated.
The design concept of employing the dynamically reconfigurable scattering pattern to enhance radar cross-section is proposed and examined. In combination with varactor loading, a physical unit cell geometry with an embedded bias network for the varactors is utilized to build the metasurface. Biased by an applied direct-current source with voltage gradient, the proposed active metasurface can exhibit electrically tunable reflection phase distributions for either normal or oblique incidence plane wave, so as to achieve flexible redirection of the angle of reflection. As a result, the agile effect for monostatic or bistatic cross-section enhancement is then facilitated. Taking a conducting plate as an example, three different incidence and reflection scenarios are considered for calculation and full-wave simulation. Reconfigurable scattering patterns produced at the operating frequency of 10 GHz by the presented design are observed, which indicates its capability of real-time control of the angle of reflection. In conjunction with an experimental measurement, the effective enhancement of monostatic and bistatic cross-sections are validated.
2021,
33: 043003.
doi: 10.11884/HPLPB202133.200353
Abstract:
Linearizer is a key component in the millimeter-wave communication system, it plays an important role in improving the linearity performance of amplifier and communication quality. At present, the development of traveling-wave tube amplifier (TWTA) linearization technology cannot meet the application requirements of communication technology, therefore, the research of linearization technology is very important. In this paper we propose a kind of a new wide-band analog pre-distortion structure used to improve the nonlinear characteristics of Ka-band TWTA. The simulation results show that when the input power changes from −20 to 10 dBm in the frequency range of 26−30 GHz, the gain expansion of the linearizer is greater than 5.08 dB, and the phase expansion exceeds 64.81°. The linearizer and the TWTA are cascaeded for testing. The test results show that the gain compression and phase compression of center frequence is less than 3.12 dB and 2.31° respectively, and the third-order intermodulation (IMD3) improves significantly.
Linearizer is a key component in the millimeter-wave communication system, it plays an important role in improving the linearity performance of amplifier and communication quality. At present, the development of traveling-wave tube amplifier (TWTA) linearization technology cannot meet the application requirements of communication technology, therefore, the research of linearization technology is very important. In this paper we propose a kind of a new wide-band analog pre-distortion structure used to improve the nonlinear characteristics of Ka-band TWTA. The simulation results show that when the input power changes from −20 to 10 dBm in the frequency range of 26−30 GHz, the gain expansion of the linearizer is greater than 5.08 dB, and the phase expansion exceeds 64.81°. The linearizer and the TWTA are cascaeded for testing. The test results show that the gain compression and phase compression of center frequence is less than 3.12 dB and 2.31° respectively, and the third-order intermodulation (IMD3) improves significantly.
2021,
33: 043004.
doi: 10.11884/HPLPB202133.200336
Abstract:
High-intensity electromagnetic pulses like high-altitude electromagnetic pulse (HEMP), high power microwave (HPM) are very harmful to electronic devices, which will cause malfunction or even damage to electronics. Using metallic cavity to isolate electronic systems from high-intensity electromagnetic pulse is an important and effective way to lessen the effect. Herein, we performed a systematic study on coupling property of metallic cavity with a rectangular aperture under the excitation of three types of high-intensity electromagnetic pulses, i.e., HEMP, wide-band HPM, and narrow-band HPM. The width/length ratio of aperture and cavity size were varied to investigate their effect on electromagnetic coupling. The interaction mechanism of high-intensity electromagnetic pulses and the metallic cavity was also carefully analyzed. The results demonstrate that the shielding property of metallic cavity is highly dependent on resonance mode of cavity, resonant frequency of aperture as well as the spectral characteristics of high-intensity electromagnetic pulse. When the resonance mode of cavity, and/or resonant frequency of aperture are within the bandwidth of high-intensity electromagnetic pulse, an enlarged coupling electromagnetic field in the metallic is always produced. Specifically, the interaction between the cavity and aperture can give rise to spectral shift of resonant frequency. Therefore, to obtain excellent shielding effect, we need to take into consideration the suppression of resonance mode of cavity, resonant frequency of apertureas well as the spectral shift when performing electromagnetic protection of electronic devices.
High-intensity electromagnetic pulses like high-altitude electromagnetic pulse (HEMP), high power microwave (HPM) are very harmful to electronic devices, which will cause malfunction or even damage to electronics. Using metallic cavity to isolate electronic systems from high-intensity electromagnetic pulse is an important and effective way to lessen the effect. Herein, we performed a systematic study on coupling property of metallic cavity with a rectangular aperture under the excitation of three types of high-intensity electromagnetic pulses, i.e., HEMP, wide-band HPM, and narrow-band HPM. The width/length ratio of aperture and cavity size were varied to investigate their effect on electromagnetic coupling. The interaction mechanism of high-intensity electromagnetic pulses and the metallic cavity was also carefully analyzed. The results demonstrate that the shielding property of metallic cavity is highly dependent on resonance mode of cavity, resonant frequency of aperture as well as the spectral characteristics of high-intensity electromagnetic pulse. When the resonance mode of cavity, and/or resonant frequency of aperture are within the bandwidth of high-intensity electromagnetic pulse, an enlarged coupling electromagnetic field in the metallic is always produced. Specifically, the interaction between the cavity and aperture can give rise to spectral shift of resonant frequency. Therefore, to obtain excellent shielding effect, we need to take into consideration the suppression of resonance mode of cavity, resonant frequency of apertureas well as the spectral shift when performing electromagnetic protection of electronic devices.
2021,
33: 043005.
doi: 10.11884/HPLPB202133.200303
Abstract:
The electric field in a horizontally polarized bounded-wave electromagnetic pulse(EMP) simulator with 9.5 m in height are got by experimental measurement. The study of field distribution characteristics in the simulator based on the field, including the quantity analysis of the field uniformity in some domain and the method for defining the effective testing space in the simulator, is given. The domain of an effective space with the lowest horizontal plane 2 m away from the ground is estimated. The experimental results show that, the peak-value of the electric field of the testing point right under the bicone’s center with a distance of 5.5−7.5 m decreases inversely with the distance between the testing point and the bicone’s center. The effect of the discontinuous configuration of the bicone and the plane on the electric field in time domain of the testing points under the center is slower as the distance increases, but the influence of the ground on the field is quicker; The field along the leakage direction of the field in the simulator decreases more slowly than those along the bicone’s symmetric axis, as the testing-points located at a horizontal plane far away from the ground; The mean value of the normalized electric field in 12 m×12 m domain on the horizontal plane 1 m away from the ground in the simulator is 0.678, the corresponding standard deviation is 0.068 9, and the field uniformity is 2.039 dB.
The electric field in a horizontally polarized bounded-wave electromagnetic pulse(EMP) simulator with 9.5 m in height are got by experimental measurement. The study of field distribution characteristics in the simulator based on the field, including the quantity analysis of the field uniformity in some domain and the method for defining the effective testing space in the simulator, is given. The domain of an effective space with the lowest horizontal plane 2 m away from the ground is estimated. The experimental results show that, the peak-value of the electric field of the testing point right under the bicone’s center with a distance of 5.5−7.5 m decreases inversely with the distance between the testing point and the bicone’s center. The effect of the discontinuous configuration of the bicone and the plane on the electric field in time domain of the testing points under the center is slower as the distance increases, but the influence of the ground on the field is quicker; The field along the leakage direction of the field in the simulator decreases more slowly than those along the bicone’s symmetric axis, as the testing-points located at a horizontal plane far away from the ground; The mean value of the normalized electric field in 12 m×12 m domain on the horizontal plane 1 m away from the ground in the simulator is 0.678, the corresponding standard deviation is 0.068 9, and the field uniformity is 2.039 dB.
2021,
33: 044001.
doi: 10.11884/HPLPB202133.210011
Abstract:
HLS-II is a dedicated synchrotron radiation source mainly based on vacuum ultraviolet and soft X-rays. As a user facility, it has high requirements for operating performance. To improve the real-time performance and convenience of data query and meet the needs of staff to keep abreast of the operation status of the facility in time, the HLS-II mobile data query system is developed based on Web technology. The system is developed in the EPICS environment. IOC is used as the real-time data source, HBase database as the historical data source, Phoebus Alarms as the alarm data source, and MySQL database is used to store the user management information. The whole system adopts the design pattern of separation of front and back ends. The back end of the system is developed with Spring Boot framework and Node.js environment. The front end of the system is developed with the Vue.js framework, using lib-flexible layout scheme and postcss-pxtorem plug-in to adapt to different types of mobile devices. The test results show that the HLS-II mobile data query system can update information smoothly, operate intuitively and conveniently, and meet the design requirements.
HLS-II is a dedicated synchrotron radiation source mainly based on vacuum ultraviolet and soft X-rays. As a user facility, it has high requirements for operating performance. To improve the real-time performance and convenience of data query and meet the needs of staff to keep abreast of the operation status of the facility in time, the HLS-II mobile data query system is developed based on Web technology. The system is developed in the EPICS environment. IOC is used as the real-time data source, HBase database as the historical data source, Phoebus Alarms as the alarm data source, and MySQL database is used to store the user management information. The whole system adopts the design pattern of separation of front and back ends. The back end of the system is developed with Spring Boot framework and Node.js environment. The front end of the system is developed with the Vue.js framework, using lib-flexible layout scheme and postcss-pxtorem plug-in to adapt to different types of mobile devices. The test results show that the HLS-II mobile data query system can update information smoothly, operate intuitively and conveniently, and meet the design requirements.
2021,
33: 044002.
doi: 10.11884/HPLPB202133.200287
Abstract:
Taking advantage of the robustness of genetic algorithm and the advantage of FPGA in parallel computing, we developed the cavity failure compensation program based on the Injector II’s Cryogenic Module IV (CM4) of China Accelerator Driven Sub-critical System (C-ADS). The beam dynamics software TRACEWIN was used to verify the results got by the FPGA program, and the FPGA program was packed as an IP core to be used in a more general form in the embedded Linux system. In addition, considering the requirements of independence and low latency for the future superconducting cavity failure compensation system, Linux system and EPICS components are compiled for the MicroBlaze soft core processor, and the communication function of the superconducting cavity failure compensation system was verified in the built simulating communication environment.
Taking advantage of the robustness of genetic algorithm and the advantage of FPGA in parallel computing, we developed the cavity failure compensation program based on the Injector II’s Cryogenic Module IV (CM4) of China Accelerator Driven Sub-critical System (C-ADS). The beam dynamics software TRACEWIN was used to verify the results got by the FPGA program, and the FPGA program was packed as an IP core to be used in a more general form in the embedded Linux system. In addition, considering the requirements of independence and low latency for the future superconducting cavity failure compensation system, Linux system and EPICS components are compiled for the MicroBlaze soft core processor, and the communication function of the superconducting cavity failure compensation system was verified in the built simulating communication environment.
2021,
33: 044003.
doi: 10.11884/HPLPB202133.200212
Abstract:
For investigating and tracing the multi-bunch transverse coupled instability caused by beam impedance and evaluating the suppressive effect to the instability by the newly updated Transverse Feedback System during the upgrade process of Shanghai Synchrotron Radiation Facility (SSRF) PHASE II, transverse beam motion in different states were recorded by diagnostics tool of feedback processor in the system, by which the evolution of dominate instability modes were analyzed respectively in steady-state, injection transient and growing-damping process. Growth/Damp rate as well as dependence of growth rate and beam current were calculated. Also, performance of the feedback system was evaluated. These research results provide data support for machine operation optimization.
For investigating and tracing the multi-bunch transverse coupled instability caused by beam impedance and evaluating the suppressive effect to the instability by the newly updated Transverse Feedback System during the upgrade process of Shanghai Synchrotron Radiation Facility (SSRF) PHASE II, transverse beam motion in different states were recorded by diagnostics tool of feedback processor in the system, by which the evolution of dominate instability modes were analyzed respectively in steady-state, injection transient and growing-damping process. Growth/Damp rate as well as dependence of growth rate and beam current were calculated. Also, performance of the feedback system was evaluated. These research results provide data support for machine operation optimization.
2021,
33: 044004.
doi: 10.11884/HPLPB202133.200357
Abstract:
To overcome the limitation of the traditional beam stacking method and accumulate the heavy ion beam to higher intensity, Heavy Ion Research Facility in Lanzhou (HIRFL) will adopt Moving Barrier Bucket (BB) stacking scheme in Cooling Storage Experimental Ring (CSRe). The amplitude, phase and periodic adjustable BB voltage produced by the Radio Frequency (RF) control system is the core of this accumulation mode. However, due to the wide-band characteristics of BB voltage and the nonlinearity of RF system, there will be serious distortion of BB voltage in RF cavity. Based on the analysis of the characteristics of BB voltage and RF system, the predistortion feedforward control is introduced to eliminate the distortion. This paper describes the mathematical model, simulation, hardware and software design and test results of this method in detail. The results will be helpful to the BB stacking experiment of HIRFL-CSRe and BB stacking mode of High Intensity heavy-ion Accelerator Facility (HIAF).
To overcome the limitation of the traditional beam stacking method and accumulate the heavy ion beam to higher intensity, Heavy Ion Research Facility in Lanzhou (HIRFL) will adopt Moving Barrier Bucket (BB) stacking scheme in Cooling Storage Experimental Ring (CSRe). The amplitude, phase and periodic adjustable BB voltage produced by the Radio Frequency (RF) control system is the core of this accumulation mode. However, due to the wide-band characteristics of BB voltage and the nonlinearity of RF system, there will be serious distortion of BB voltage in RF cavity. Based on the analysis of the characteristics of BB voltage and RF system, the predistortion feedforward control is introduced to eliminate the distortion. This paper describes the mathematical model, simulation, hardware and software design and test results of this method in detail. The results will be helpful to the BB stacking experiment of HIRFL-CSRe and BB stacking mode of High Intensity heavy-ion Accelerator Facility (HIAF).
2021,
33: 044005.
doi: 10.11884/HPLPB202133.200268
Abstract:
High Energy Photon Source (HEPS) Booster is designed to ramp up the energy of the beam from linac and inject high quality electron beam to the storage ring. To measure the transverse beam size, emittance and energy spread of HEPS Booster, we designed two beam diagnostic beamlines at visible-UV spectrum region. The source points are at two bending magnets with different chromatic dispersion, one has no dispersion while the other has large dispersion. By measuring the transverse beam sizes with synchrotron imaging system, beam emittance and energy spread can also be calculated. This paper introduces the extraction of visible-UV light, and the optical imaging system, the spatial resolution. It also introduces the design of beam spot changes measurement during beam ramping process.
High Energy Photon Source (HEPS) Booster is designed to ramp up the energy of the beam from linac and inject high quality electron beam to the storage ring. To measure the transverse beam size, emittance and energy spread of HEPS Booster, we designed two beam diagnostic beamlines at visible-UV spectrum region. The source points are at two bending magnets with different chromatic dispersion, one has no dispersion while the other has large dispersion. By measuring the transverse beam sizes with synchrotron imaging system, beam emittance and energy spread can also be calculated. This paper introduces the extraction of visible-UV light, and the optical imaging system, the spatial resolution. It also introduces the design of beam spot changes measurement during beam ramping process.
2021,
33: 044006.
doi: 10.11884/HPLPB202133.200297
Abstract:
Based on thermal stability and vibration stability, an ultra stability structure of rigid support is designed and optimized. Through the finite element modal analysis of ANSYS, the thermal expansion variation and the characteristic frequency of the support is verified. The support is fixated to the ground by using the method of concrete grouting and then the characteristic frequency is tested. The test results show that the characteristic frequency of the support reaches up to 61.9 Hz and the vibration amplitude is less than 30 nm, both of which meet the design requirements. Finally, the method of dynamic stiffness testing is adopted to obtain the stiffness value of the concrete grouting, and the accuracy of the optimization results of the support is further verified.
Based on thermal stability and vibration stability, an ultra stability structure of rigid support is designed and optimized. Through the finite element modal analysis of ANSYS, the thermal expansion variation and the characteristic frequency of the support is verified. The support is fixated to the ground by using the method of concrete grouting and then the characteristic frequency is tested. The test results show that the characteristic frequency of the support reaches up to 61.9 Hz and the vibration amplitude is less than 30 nm, both of which meet the design requirements. Finally, the method of dynamic stiffness testing is adopted to obtain the stiffness value of the concrete grouting, and the accuracy of the optimization results of the support is further verified.
2021,
33: 044007.
doi: 10.11884/HPLPB202133.200132
Abstract:
The high intense pulse electron beam emitted and accelerated by linear induction accelerator (LIA) is focused to heavy metal target to produce X-ray pulses via bremsstrahlung mechanism. The X-ray is applied to high energy flash radiography. The X-ray spot size is a critical parameter for LIA and the main factor which degrades resolution of the flash radiography. This paper describes a pinhole imaging system measuring the X-ray spot size. The full width at half maximum (FWHM) of the X-ray spot size can be obtained from the pinhole image data. The modulation transfer function (MTF) which is derived from the X-ray spot image by Fourier transform is applied to calculate the 50%MTF spot size. In the continuous experiments of multi-pulse electron linear induction accelerator (MPELIA), the X-ray spot size is measured and the results demonstrate reliable performance of MPELIA. The concept of form factor is introduced, and the measured results show that the MPLIA X-ray spot distribution changes between Gaussian and Bennett distribution.
The high intense pulse electron beam emitted and accelerated by linear induction accelerator (LIA) is focused to heavy metal target to produce X-ray pulses via bremsstrahlung mechanism. The X-ray is applied to high energy flash radiography. The X-ray spot size is a critical parameter for LIA and the main factor which degrades resolution of the flash radiography. This paper describes a pinhole imaging system measuring the X-ray spot size. The full width at half maximum (FWHM) of the X-ray spot size can be obtained from the pinhole image data. The modulation transfer function (MTF) which is derived from the X-ray spot image by Fourier transform is applied to calculate the 50%MTF spot size. In the continuous experiments of multi-pulse electron linear induction accelerator (MPELIA), the X-ray spot size is measured and the results demonstrate reliable performance of MPELIA. The concept of form factor is introduced, and the measured results show that the MPLIA X-ray spot distribution changes between Gaussian and Bennett distribution.
2021,
33: 044008.
doi: 10.11884/HPLPB202133.200340
Abstract:
To send out early warnings before some failures of the China Spallation Neutron Source (CSNS) accelerator, the feature models of the CSNS accelerator vacuums and drift tube linac (DTL) temperatures have been established based on deep learning, and a prototype of an early warning system has been developed. This prototype of an early warning system was built based on the experimental physics and industrial control system (EPICS) architecture, and it is mainly composed of three parts: training, recognition and information release. Python was adopted for program design and development, and functions such as training samples acquisition, deep learning networks design and training, online recognition and information release have been realized. The test results show that the accuracy of this prototype can reach 98.4% for the test set generated based on the historical data of the CSNS accelerator vacuums and DTL temperatures, and the anomalies of the CSNS accelerator vacuums and DTL temperatures can be recognized based on the real-time data, and the early warnings can be sent out, which proves its feasibility and effectiveness.
To send out early warnings before some failures of the China Spallation Neutron Source (CSNS) accelerator, the feature models of the CSNS accelerator vacuums and drift tube linac (DTL) temperatures have been established based on deep learning, and a prototype of an early warning system has been developed. This prototype of an early warning system was built based on the experimental physics and industrial control system (EPICS) architecture, and it is mainly composed of three parts: training, recognition and information release. Python was adopted for program design and development, and functions such as training samples acquisition, deep learning networks design and training, online recognition and information release have been realized. The test results show that the accuracy of this prototype can reach 98.4% for the test set generated based on the historical data of the CSNS accelerator vacuums and DTL temperatures, and the anomalies of the CSNS accelerator vacuums and DTL temperatures can be recognized based on the real-time data, and the early warnings can be sent out, which proves its feasibility and effectiveness.
2021,
33: 044009.
doi: 10.11884/HPLPB202133.200310
Abstract:
The electron gun with high repetition rate and high average current has a very wide range of applications. This paper presents the design of a microwave grid-controlled high-voltage thermionic electron gun working in CW mode with a bunch repetition rate of 325 MHz and elaborates the experimental principles of this kind of electron guns. Firstly, simulation software EGUN, POISSON (Poisson Superfish) and GPT (General Particle Tracer) are used to accomplish the structure design of a300kV high-voltage DC electron gun and beam dynamics verification.Secondly, to feed the microwave into the gap between the cathode and the grid of the electron gunefficiently, design of a power supply with a scheme of impedance matching from the radio frequency power source to the cathode is completed.Accordingly, a 325 MHz dual-mode coaxial power supply device is designed, and its feasibility is verified and analyzed..
The electron gun with high repetition rate and high average current has a very wide range of applications. This paper presents the design of a microwave grid-controlled high-voltage thermionic electron gun working in CW mode with a bunch repetition rate of 325 MHz and elaborates the experimental principles of this kind of electron guns. Firstly, simulation software EGUN, POISSON (Poisson Superfish) and GPT (General Particle Tracer) are used to accomplish the structure design of a300kV high-voltage DC electron gun and beam dynamics verification.Secondly, to feed the microwave into the gap between the cathode and the grid of the electron gunefficiently, design of a power supply with a scheme of impedance matching from the radio frequency power source to the cathode is completed.Accordingly, a 325 MHz dual-mode coaxial power supply device is designed, and its feasibility is verified and analyzed..
2021,
33: 045001.
doi: 10.11884/HPLPB202133.210069
Abstract:
Metal strength research under extreme conditions is of vital importancefor weapons physics and aeromechanics applications. Material’s response has an affinity with microstructure, stress history, pressure and temperature, etc. Magnetically driven isentropic compression as a new experimental technique between quasi-static and impact, has low increased entropy and temperature. Magnetic pressure produced from the current flow in the load electrode compress the sample, which is decided by the load current shape and load configuration. This experimental workwascarried out on a 10 MA facility in CAEP. The 10 MA facility includes 24 modules, which help to control the load current shape in a relative wide range, thereby provides a different ideal isentropic compression experimental platform for millimeter thick and centimeter diameter samplesto be driven with different strain rates. In this paper, based on the characteristics of 10 MA device, the sample loading path was controlled by adjusting the load current waveform. In a certain pressure-strain rate range, the strength of tantalum was experimented. The loading and unloading wave profile velocity history of tantalum samples with different thicknesses was successfully obtained, and the strength data of tantalum under a series of peak pressures were obtained. Compareing the strength results of the multiple material loading platform under different loading paths, the results in this work significantly higher than the strength under shock loading, but lower than the strength under quasi static loading based on the multi-branch confluence strength test technology, more abundant experimental studies on material dynamic characteristics will be carried out in the future.
2021,
33: 045002.
doi: 10.11884/HPLPB202133.200239
Abstract:
Thyristor has the advantages of good control characteristics, long life time, small size, low noise, etc., and it is an important device for high-power pulsed power supplies. However, when a thyristor is used under high voltage, high current, and repetitive frequency working conditions, the thyristor may not be turned off within a certain time, causing the pulse power supply to fail. To improve the working ability of the thyristor under repetitive frequency, this paper studies the turn-off process of the pulse power thyristor component. Based on the turn-off principle and experimental analysis of the thyristor, it is found that under the same conditions, increasing the current peak value has little effect on the reverse recovery characteristics of the thyristor, and the relationship is got between reverse recovery time, reverse recovery charge and di/dt of the thyristor. The reverse recovery current waveform of the thyristor is fitted according to the experimental data, and the current exponential function model is modified to better fit the reverse recovery current.
Thyristor has the advantages of good control characteristics, long life time, small size, low noise, etc., and it is an important device for high-power pulsed power supplies. However, when a thyristor is used under high voltage, high current, and repetitive frequency working conditions, the thyristor may not be turned off within a certain time, causing the pulse power supply to fail. To improve the working ability of the thyristor under repetitive frequency, this paper studies the turn-off process of the pulse power thyristor component. Based on the turn-off principle and experimental analysis of the thyristor, it is found that under the same conditions, increasing the current peak value has little effect on the reverse recovery characteristics of the thyristor, and the relationship is got between reverse recovery time, reverse recovery charge and di/dt of the thyristor. The reverse recovery current waveform of the thyristor is fitted according to the experimental data, and the current exponential function model is modified to better fit the reverse recovery current.
2021,
33: 045003.
doi: 10.11884/HPLPB202133.200328
Abstract:
To further promote the application of solid-state Marx generators, enable them with the visual display of output pulse waveforms, more accurate regulation of voltage, and shorter charging regulation time, it is necessary to study the automatic control of solid-state Marx generator. In this paper, with a field programmable gate array (FPGA) as the controller, the output voltage, frequency, pulse width, overcurrent threshold value, and other parameters, as well as fault detection and indication, are all directly displayed on the LCD screen to realize visible settings and adjustment. In solid-state Marx generators, a voltage dividing circuit in parallel with the output and a high-speed analog-digital conversion circuit is used to realize high-voltage pulse sampling of the output. With these sampled voltage values, on the one hand, the closed-loop segmented PID control can be realized to achieve fast charging and precise adjustment of the output voltage. On the other hand, the basic waveform of the real-time pulses can be displayed in the virtual oscilloscope. Besides, fault detection and protection mechanisms have been added to the circuit to quickly detect over-temperature, overcurrent, and other faults in the circuit and respond to their timely shutdown to protect the pulse generators and the operators. The voltage waveforms of repetitive square pulses generated by the topology of a 20-stage solid-state square Marx generator indicate that the basic automatical control of this solid-state Marx generator has been realized and it can operate reliably.
To further promote the application of solid-state Marx generators, enable them with the visual display of output pulse waveforms, more accurate regulation of voltage, and shorter charging regulation time, it is necessary to study the automatic control of solid-state Marx generator. In this paper, with a field programmable gate array (FPGA) as the controller, the output voltage, frequency, pulse width, overcurrent threshold value, and other parameters, as well as fault detection and indication, are all directly displayed on the LCD screen to realize visible settings and adjustment. In solid-state Marx generators, a voltage dividing circuit in parallel with the output and a high-speed analog-digital conversion circuit is used to realize high-voltage pulse sampling of the output. With these sampled voltage values, on the one hand, the closed-loop segmented PID control can be realized to achieve fast charging and precise adjustment of the output voltage. On the other hand, the basic waveform of the real-time pulses can be displayed in the virtual oscilloscope. Besides, fault detection and protection mechanisms have been added to the circuit to quickly detect over-temperature, overcurrent, and other faults in the circuit and respond to their timely shutdown to protect the pulse generators and the operators. The voltage waveforms of repetitive square pulses generated by the topology of a 20-stage solid-state square Marx generator indicate that the basic automatical control of this solid-state Marx generator has been realized and it can operate reliably.
2021,
33: 046001.
doi: 10.11884/HPLPB202133.200220
Abstract:
The first gamma-ray total absorption facility composed of 40 BaF2 detector units has been constructed in China. Utilizing the property of high detection efficiency and good time resolution for gamma rays of BaF2 crystal, the facility will be used to measure on-line the cross section of neutron capture reaction. Neutron source of 250 keV～850 keV was set up on the HI-13 tandem accelerator, its source intensity at 0° was about 5.09 × 106 n/(Sr·s). The experimental data of 93Nb, 197Au, natC and empty samples were measured by the prompt gamma ray method with gamma-ray total absorption facility. According to the characteristics of BaF2 detector signal, a variety of digital waveform analysis methods were adopted to eliminate noise signal as much as possible to improve the effect background ratio, such as baseline compensation, software threshold setting, time window limitation, pulse amplitude integral growth rate setting and fast slow component ratio setting. The experimental data of 93Nb neutron capture reaction cross section was obtained by relative measurement method. The data of 197Au sample was the standard, the data of natC sample was the sample correlation background, and the data of empty sample was the sample independence background. The feasibility of the measurement facility and technical method was verified by comparing with the data of ENDF evaluation library.
The first gamma-ray total absorption facility composed of 40 BaF2 detector units has been constructed in China. Utilizing the property of high detection efficiency and good time resolution for gamma rays of BaF2 crystal, the facility will be used to measure on-line the cross section of neutron capture reaction. Neutron source of 250 keV～850 keV was set up on the HI-13 tandem accelerator, its source intensity at 0° was about 5.09 × 106 n/(Sr·s). The experimental data of 93Nb, 197Au, natC and empty samples were measured by the prompt gamma ray method with gamma-ray total absorption facility. According to the characteristics of BaF2 detector signal, a variety of digital waveform analysis methods were adopted to eliminate noise signal as much as possible to improve the effect background ratio, such as baseline compensation, software threshold setting, time window limitation, pulse amplitude integral growth rate setting and fast slow component ratio setting. The experimental data of 93Nb neutron capture reaction cross section was obtained by relative measurement method. The data of 197Au sample was the standard, the data of natC sample was the sample correlation background, and the data of empty sample was the sample independence background. The feasibility of the measurement facility and technical method was verified by comparing with the data of ENDF evaluation library.
2021,
33: 046002.
doi: 10.11884/HPLPB202133.200280
Abstract:
Gamma-ray personal dosimeters are important tools for the radiation protection for workers. However, the current calibration method based on standard reference radiation has low verification efficiency, large calibration workload, and requires remote inspection. To solve the above problems, this paper attempts to apply the minitype reference radiation to the calibration of gamma-ray personal dosimeters. The Monte Carlo method is used to simulate the dose distribution in the minitype reference radiation field, the influence of scattering rays which are caused by the device structure and dosimeters in the dose field. The results show that 1 Ci 137Cs can provide a dose rate of 1.5 mSv/h for the point of test, and the relative standard deviation of the dose rate at the point of test is about 0.48%. When the thickness of the stage is 20 mm, the influence rate of scattered rays on the dose rate value at the minitype reference radiation inspection point is 3.27%, which is higher than the influence of the size of the dosimeter (1.62%) and the number of dosimeters (0.56%). This paper provides a theoretical basis for in situ calibration to calibrate gamma-ray personal dosimeters.
Gamma-ray personal dosimeters are important tools for the radiation protection for workers. However, the current calibration method based on standard reference radiation has low verification efficiency, large calibration workload, and requires remote inspection. To solve the above problems, this paper attempts to apply the minitype reference radiation to the calibration of gamma-ray personal dosimeters. The Monte Carlo method is used to simulate the dose distribution in the minitype reference radiation field, the influence of scattering rays which are caused by the device structure and dosimeters in the dose field. The results show that 1 Ci 137Cs can provide a dose rate of 1.5 mSv/h for the point of test, and the relative standard deviation of the dose rate at the point of test is about 0.48%. When the thickness of the stage is 20 mm, the influence rate of scattered rays on the dose rate value at the minitype reference radiation inspection point is 3.27%, which is higher than the influence of the size of the dosimeter (1.62%) and the number of dosimeters (0.56%). This paper provides a theoretical basis for in situ calibration to calibrate gamma-ray personal dosimeters.
