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RSS2019 Vol. 31, No. 8
Recommend Articles
2019, 31: 083101.
doi: 10.11884/HPLPB201931.180312
2019, 31: 085102.
doi: 10.11884/HPLPB201931.190064
Display Method:
2019,
31: 081001.
doi: 10.11884/HPLPB201931.190048
Abstract:
The frequency spectrum of turbulence measured by common micro-temperature sensor is mostly below 20 Hz, which can not show the high frequency characteristics of atmospheric temperature fluctuation.This paper introduces the design of a broadband low noise micro-temperature sensor, the development of the corresponding instrument, and the real atmospheric temperature fluctuation measurement experiment.It is shown that the atmospheric temperature fluctuation has abundant high frequency information.The power spectrum of temperature fluctuation has power invariance in a wider frequency range.Some of the temperature spectrum has inflection points in the high frequency part, and decreases more steeply.The shape of the turbulence spectrum and the position of the inflection point are related to the turbulence intensity.This study broadens the research scope of temperature fluctuation power spectrum, provides high frequency turbulence spectrum information for theoretical research and technical application of light wave transmission, and provides measurements for non-Kolmogorov turbulence research.
The frequency spectrum of turbulence measured by common micro-temperature sensor is mostly below 20 Hz, which can not show the high frequency characteristics of atmospheric temperature fluctuation.This paper introduces the design of a broadband low noise micro-temperature sensor, the development of the corresponding instrument, and the real atmospheric temperature fluctuation measurement experiment.It is shown that the atmospheric temperature fluctuation has abundant high frequency information.The power spectrum of temperature fluctuation has power invariance in a wider frequency range.Some of the temperature spectrum has inflection points in the high frequency part, and decreases more steeply.The shape of the turbulence spectrum and the position of the inflection point are related to the turbulence intensity.This study broadens the research scope of temperature fluctuation power spectrum, provides high frequency turbulence spectrum information for theoretical research and technical application of light wave transmission, and provides measurements for non-Kolmogorov turbulence research.
2019,
31: 081002.
doi: 10.11884/HPLPB201931.190074
Abstract:
The sounding balloons released from Korla, Maoming, Guangdong and Lhasa, Tibet, have been used to measure the profiles of temperature, air pressure and wind velocity and the refractive index structure constants of the atmosphere.Based on the optical turbulence parameterization of Tatarski theory and the above-mentioned areas sounding data, the atmospheric optical turbulence profiles in three regions, Korla, Xinjiang the coast of Maoming, Guangdong and Lhasa, Tibet, are estimated by using Thorpe scale.Estimated results are compared with measured profiles in these three regions.The estimated values and the measured values are in good agreement with each other in the order of magnitude and the trend of change, and the correlation are69%, 60%, 68%, respectively.In addition, compared with other parameterized methods for estimating turbulence profiles, the Thorpe scale is simple and has less input parameters.
The sounding balloons released from Korla, Maoming, Guangdong and Lhasa, Tibet, have been used to measure the profiles of temperature, air pressure and wind velocity and the refractive index structure constants of the atmosphere.Based on the optical turbulence parameterization of Tatarski theory and the above-mentioned areas sounding data, the atmospheric optical turbulence profiles in three regions, Korla, Xinjiang the coast of Maoming, Guangdong and Lhasa, Tibet, are estimated by using Thorpe scale.Estimated results are compared with measured profiles in these three regions.The estimated values and the measured values are in good agreement with each other in the order of magnitude and the trend of change, and the correlation are69%, 60%, 68%, respectively.In addition, compared with other parameterized methods for estimating turbulence profiles, the Thorpe scale is simple and has less input parameters.
2019,
31: 082001.
doi: 10.11884/HPLPB201931.190211
Abstract:
The initial damage and damage growth of fused quartz optical elements irradiated by fundamental frequency, double frequency and triple frequency lasers alone and at the same time are studied comparatively.The effects of fundamental and double frequencies on the initial damage and damage growth induced by triple frequencies are emphatically studied.The conversion factors of fundamental frequency and double frequency relative to triple frequency are analyzed.Research results show that, when the energy density of fundamental frequency and double frequency is low, their influence on damage probability curve of triple frequency can be neglected.However, it will cause an increase in the degree of damage.In multi-wavelength simultaneous irradiation damage growth, the damage growth threshold mainly depends on the energy density of triple frequency, and the damage growth coefficient is related to the total energy density.The conversion factor can reflect both the wavelength effect of initial damage and damage growth and the energy coupling effect between wavelengths.
The initial damage and damage growth of fused quartz optical elements irradiated by fundamental frequency, double frequency and triple frequency lasers alone and at the same time are studied comparatively.The effects of fundamental and double frequencies on the initial damage and damage growth induced by triple frequencies are emphatically studied.The conversion factors of fundamental frequency and double frequency relative to triple frequency are analyzed.Research results show that, when the energy density of fundamental frequency and double frequency is low, their influence on damage probability curve of triple frequency can be neglected.However, it will cause an increase in the degree of damage.In multi-wavelength simultaneous irradiation damage growth, the damage growth threshold mainly depends on the energy density of triple frequency, and the damage growth coefficient is related to the total energy density.The conversion factor can reflect both the wavelength effect of initial damage and damage growth and the energy coupling effect between wavelengths.
2019,
31: 083001.
doi: 10.11884/HPLPB201931.180277
Abstract:
For the shortcomings of unknown mode purity and apparently ambiguous design idea in the literature (Danilov, 2007), an improved rotating high-order mode generator based on the helically-distributed perforation (HDP) technique is presented to realize high purity conversion of coaxial TE1, 1 mode to circular TE5, 3 mode.According to the inhomogeneous string equation, the optimal configurations of the coaxial cavity are obtained by the numerical calculation so that the required mode can effectively resonate.Based on the pinhole diffraction theory and the electric field boundary conditions on the surface of the perfect electric conductor (PEC), the arrangement of HDP and the working principle of the mode suppressor are studied in detail.Numerical calculations and simulation results indicate that the mode purity of TE5, 3 mode generator is as high as 97.4%, and the conversion efficiency is 96.1% near the center frequency of 30 GHz.Compared with its old version, the generator has the obvious advantages of high mode purity and compactness.
For the shortcomings of unknown mode purity and apparently ambiguous design idea in the literature (Danilov, 2007), an improved rotating high-order mode generator based on the helically-distributed perforation (HDP) technique is presented to realize high purity conversion of coaxial TE1, 1 mode to circular TE5, 3 mode.According to the inhomogeneous string equation, the optimal configurations of the coaxial cavity are obtained by the numerical calculation so that the required mode can effectively resonate.Based on the pinhole diffraction theory and the electric field boundary conditions on the surface of the perfect electric conductor (PEC), the arrangement of HDP and the working principle of the mode suppressor are studied in detail.Numerical calculations and simulation results indicate that the mode purity of TE5, 3 mode generator is as high as 97.4%, and the conversion efficiency is 96.1% near the center frequency of 30 GHz.Compared with its old version, the generator has the obvious advantages of high mode purity and compactness.
2019,
31: 083002.
doi: 10.11884/HPLPB201931.180275
Abstract:
Improving antenna performance at low frequency is the focus of TEM horn antenna research.A new TEM horn antenna was designed by analyzing the impedance gradient and time-domain radiation characteristics of the antenna, to solve the reflection problem at the end of the antenna and improve the low-frequency performance of the antenna.Compared with the typical TEM horn antenna, the new TEM horn antenna designed in this paper reduces the pattern back lobe in the full frequency band, improves the antenna radiation spindle gain at low frequency, and expands the low frequency bandwidth.The antenna size is 48.5 cm×38.1 cm×35 cm.The experimental results show that the return loss at 160 MHz, 2.5 GHz is less than-10 dB and the pattern back lobe is less than-2 dB.
Improving antenna performance at low frequency is the focus of TEM horn antenna research.A new TEM horn antenna was designed by analyzing the impedance gradient and time-domain radiation characteristics of the antenna, to solve the reflection problem at the end of the antenna and improve the low-frequency performance of the antenna.Compared with the typical TEM horn antenna, the new TEM horn antenna designed in this paper reduces the pattern back lobe in the full frequency band, improves the antenna radiation spindle gain at low frequency, and expands the low frequency bandwidth.The antenna size is 48.5 cm×38.1 cm×35 cm.The experimental results show that the return loss at 160 MHz, 2.5 GHz is less than-10 dB and the pattern back lobe is less than-2 dB.
2019,
31: 083101.
doi: 10.11884/HPLPB201931.180312
Abstract:
An extended interaction klystron (EIK), which is composed of an input cavity and an output cavity both based on 8 periods of staggered double rectangular waveguide structure (SDRWS) and an intermediate cavity based on 6 periods of SDRWS, is calculated in detail on computer.After calculating reflection coefficient S11 of the input cavity and output cavity and the eigenmodes of the intermediate cavity, the structural parameters of the input cavity and output cavity and the intermediate cavity are determined, then PIC simulation is done to predict the EIK's performance, the results show that the EIK has an 1 GHz 3 dB bandwidth (219.5-220.5 GHz), a 456 W maximum power and a 40.06 dB maximum gain.Furthermore, stagger tuning by adjusting the structural parameter aof the intermediate cavity is performed to analyse howaaffects the EIK's performances, and the results show that the 3 dB band of the EIK mainly depends on the passband of the input cavity and output cavity, it also depends on the resonant frequency of the intermediate cavity in some cases.When the resonant frequency of the intermediate cavity is located at the lower or higher ends of the passband of the input cavity and output cavity, the 3 dB band of the EIK may be extended to certain extent.Particularly, when the resonant frequency of the intermediate cavity is located at or beyond the higher ends of the passband of the input cavity and output cavity, it is verified that the EIK has steady output signal featuring with pure spectrum and flat gains over the 3 dB band.The final results of the stagger tuning show that, when the structural parameter aof the intermediate cavity is 0.747 mm, the EIK reaches almost the optimum performances, with an 1.2 GHz3 dB bandwidth (219.5-220.7 GHz), a 630 W maximum power companied with a 11.3%efficiency, and a 47 dB maximum gain.
An extended interaction klystron (EIK), which is composed of an input cavity and an output cavity both based on 8 periods of staggered double rectangular waveguide structure (SDRWS) and an intermediate cavity based on 6 periods of SDRWS, is calculated in detail on computer.After calculating reflection coefficient S11 of the input cavity and output cavity and the eigenmodes of the intermediate cavity, the structural parameters of the input cavity and output cavity and the intermediate cavity are determined, then PIC simulation is done to predict the EIK's performance, the results show that the EIK has an 1 GHz 3 dB bandwidth (219.5-220.5 GHz), a 456 W maximum power and a 40.06 dB maximum gain.Furthermore, stagger tuning by adjusting the structural parameter aof the intermediate cavity is performed to analyse howaaffects the EIK's performances, and the results show that the 3 dB band of the EIK mainly depends on the passband of the input cavity and output cavity, it also depends on the resonant frequency of the intermediate cavity in some cases.When the resonant frequency of the intermediate cavity is located at the lower or higher ends of the passband of the input cavity and output cavity, the 3 dB band of the EIK may be extended to certain extent.Particularly, when the resonant frequency of the intermediate cavity is located at or beyond the higher ends of the passband of the input cavity and output cavity, it is verified that the EIK has steady output signal featuring with pure spectrum and flat gains over the 3 dB band.The final results of the stagger tuning show that, when the structural parameter aof the intermediate cavity is 0.747 mm, the EIK reaches almost the optimum performances, with an 1.2 GHz3 dB bandwidth (219.5-220.7 GHz), a 630 W maximum power companied with a 11.3%efficiency, and a 47 dB maximum gain.
2019,
31: 083102.
doi: 10.11884/HPLPB201931.190067
Abstract:
Micro-electroforming is a key step of terahertz all-metal devices microfabrication, in which metal-ion deposit uniformity determines the grating's quality.Meanwhile, the deposit uniformity is influenced by the distribution of current density near the cathode.The current density distribution in copper micro-electroforming is investigated by method of FIT (finite integration technique) simulation analysis and experimental verification.By adding aglass baffle panel between anode and cathode, the current density uniformity can be improved.The effect of the distance between panel and cathode and the size of hole in baffle panel on current density uniformity is analyzed thoroughly.The nearer the panel is to the cathode, the more uniform the current density of the cathode, which can significantly improve the uniformity of deposit in microstructure.According to the simulation results, a baffle panel with a 2.5 cm×2.5 cm gap is fabricated and placed between the anode and the cathode with a 100 mm distance from the cathode.Then electroforming was carried out and a better quality metal layer with finer and more uniform grain was gained, which proved the simulation results.
Micro-electroforming is a key step of terahertz all-metal devices microfabrication, in which metal-ion deposit uniformity determines the grating's quality.Meanwhile, the deposit uniformity is influenced by the distribution of current density near the cathode.The current density distribution in copper micro-electroforming is investigated by method of FIT (finite integration technique) simulation analysis and experimental verification.By adding aglass baffle panel between anode and cathode, the current density uniformity can be improved.The effect of the distance between panel and cathode and the size of hole in baffle panel on current density uniformity is analyzed thoroughly.The nearer the panel is to the cathode, the more uniform the current density of the cathode, which can significantly improve the uniformity of deposit in microstructure.According to the simulation results, a baffle panel with a 2.5 cm×2.5 cm gap is fabricated and placed between the anode and the cathode with a 100 mm distance from the cathode.Then electroforming was carried out and a better quality metal layer with finer and more uniform grain was gained, which proved the simulation results.
2019,
31: 083201.
doi: 10.11884/HPLPB201931.190079
Abstract:
A machine learning based evaluation method for shielding effectiveness (SE) of loaded metallic enclosures with apertures under electromagnetic wave radiation is proposed.The SEs of a variety of metallic enclosures loaded with different printed circuit boards (PCBs) is calculated using full wave analysis simulation in the frequency range of 0-5 GHz, and 5250 samples are obtained.The random forest model which is one of the popular machine learning aggression algorithms is employed to train stochastically the selected 4200 samples.Consequently, the model capable to fast predict the SE for loaded shielding enclosures characterized by 16 parameters is implemented.The rest 1050 samples are used to verify the proposed random forest model.Resultsshow that the proposed model can quickly predict the electromagnetic shielding effectiveness of the enclosure loaded with PCBs.
A machine learning based evaluation method for shielding effectiveness (SE) of loaded metallic enclosures with apertures under electromagnetic wave radiation is proposed.The SEs of a variety of metallic enclosures loaded with different printed circuit boards (PCBs) is calculated using full wave analysis simulation in the frequency range of 0-5 GHz, and 5250 samples are obtained.The random forest model which is one of the popular machine learning aggression algorithms is employed to train stochastically the selected 4200 samples.Consequently, the model capable to fast predict the SE for loaded shielding enclosures characterized by 16 parameters is implemented.The rest 1050 samples are used to verify the proposed random forest model.Resultsshow that the proposed model can quickly predict the electromagnetic shielding effectiveness of the enclosure loaded with PCBs.
2019,
31: 083202.
doi: 10.11884/HPLPB201931.180378
Abstract:
An efficient field-to-line coupling method in the time-domain is developed based on the waveform relaxation (WR) techniques for evaluating the electromagnetic (EM) transient response of multiconductor transmission lines (MTLs) excited by an electromagnetic pulse (EMP).Firstly, the incident EMP electric fields on the lines are calculated as equivalent distributed sources introduced into the MTLs equations.Then, the telegraph's equations of lossless transmission lines are decoupled by applying the WR techniques and different types of equivalent current sources at the terminal of MTLs are calculated using the iterative convolution and analytical method separately.Finally, the equivalent circuit is established and the transient currents/voltages induced on the lines are obtained by using the circuit simulation software PSCAD.The proposed time-domain method has the advantages of accuracy and high efficiency compared with the method based on finite-difference time-domain (FDTD) via two numerical examples.
An efficient field-to-line coupling method in the time-domain is developed based on the waveform relaxation (WR) techniques for evaluating the electromagnetic (EM) transient response of multiconductor transmission lines (MTLs) excited by an electromagnetic pulse (EMP).Firstly, the incident EMP electric fields on the lines are calculated as equivalent distributed sources introduced into the MTLs equations.Then, the telegraph's equations of lossless transmission lines are decoupled by applying the WR techniques and different types of equivalent current sources at the terminal of MTLs are calculated using the iterative convolution and analytical method separately.Finally, the equivalent circuit is established and the transient currents/voltages induced on the lines are obtained by using the circuit simulation software PSCAD.The proposed time-domain method has the advantages of accuracy and high efficiency compared with the method based on finite-difference time-domain (FDTD) via two numerical examples.
2019,
31: 084101.
doi: 10.11884/HPLPB201931.180308
Abstract:
For diplexer with high isolation and wideband in wireless communication system, in this paper, the diplexer specification is divided into Tx and Rx filter specifications with a certain margin.Then the wideband Tx and Rx filter is designed by using the microstrip interdigital structure and the improved method based on coupling coefficient Kand external quality factor Qe.Finally, two kinds of T-junction and filter combination structures are used to further design the diplexer, and the microstrip diplexer with these two structures are simulated and analyzed respectively.The simulation results show that the structure of parallel connection diplexer is compact, but the passband isolation is not satisfactory.The minimum return loss in the passband of the series connection diplexer is 14.16 dB, the maximum insertion loss is 1.01 dB, the minimum passband isolation is 53.46 dB, and the size of the diplexer is 8.089 9 mm×2.059 1 mm×0.302 mm.It has the advantages of large relative bandwidth, high isolation and low insertion loss, which provides the feasibility for the design of high-performance diplexer.
For diplexer with high isolation and wideband in wireless communication system, in this paper, the diplexer specification is divided into Tx and Rx filter specifications with a certain margin.Then the wideband Tx and Rx filter is designed by using the microstrip interdigital structure and the improved method based on coupling coefficient Kand external quality factor Qe.Finally, two kinds of T-junction and filter combination structures are used to further design the diplexer, and the microstrip diplexer with these two structures are simulated and analyzed respectively.The simulation results show that the structure of parallel connection diplexer is compact, but the passband isolation is not satisfactory.The minimum return loss in the passband of the series connection diplexer is 14.16 dB, the maximum insertion loss is 1.01 dB, the minimum passband isolation is 53.46 dB, and the size of the diplexer is 8.089 9 mm×2.059 1 mm×0.302 mm.It has the advantages of large relative bandwidth, high isolation and low insertion loss, which provides the feasibility for the design of high-performance diplexer.
2019,
31: 084102.
doi: 10.11884/HPLPB201931.190059
Abstract:
In order to apply the complex physical model of millimeter-wave noise of nano-MOSFET to engineering design, the expression of its compact model is studied. The complex noise physical model is simplified by transforming and analyzing the two-port correlation noise matrix of the device. The compact model proposed here not only expresses the non-quasi-static effect of the device with high precision, but also can be directly embedded into the ADS simulation design tool by Verilog-A language in the form of four nodes, thus ensuring the accuracy and greatly reducing the design complexity. The experimental results show that the proposed model is more accurate in both strong and weak inversion regions than the existing three-node model.
In order to apply the complex physical model of millimeter-wave noise of nano-MOSFET to engineering design, the expression of its compact model is studied. The complex noise physical model is simplified by transforming and analyzing the two-port correlation noise matrix of the device. The compact model proposed here not only expresses the non-quasi-static effect of the device with high precision, but also can be directly embedded into the ADS simulation design tool by Verilog-A language in the form of four nodes, thus ensuring the accuracy and greatly reducing the design complexity. The experimental results show that the proposed model is more accurate in both strong and weak inversion regions than the existing three-node model.
2019,
31: 085001.
doi: 10.11884/HPLPB201931.190040
Abstract:
In this paper, a cascade high voltage microsecond pulse power supply with output voltage of 20 kV is developed. The voltage level of a single module is 500 V, which reduces the insulation withstand high voltage requirements of the device. The output voltage value range of this pulse power supply is 0-20 kV; the repetition frequency is adjustable between 0-10 kHz; the pulse width is adjustable between 0-30 μs; the output current value is between 0-15 A; the rising and falling edge of the power supply are all within 1μs. Modular design improves the redundancy fault tolerance of this power supply and reduces its failure rate. When this power source is used as an excitation source for plasma production, and the output high voltage pulse waveform is stable, the power supply can be conveniently adjusted according to different load. When the voltage and frequency change, the mode of the discharge is different.
In this paper, a cascade high voltage microsecond pulse power supply with output voltage of 20 kV is developed. The voltage level of a single module is 500 V, which reduces the insulation withstand high voltage requirements of the device. The output voltage value range of this pulse power supply is 0-20 kV; the repetition frequency is adjustable between 0-10 kHz; the pulse width is adjustable between 0-30 μs; the output current value is between 0-15 A; the rising and falling edge of the power supply are all within 1μs. Modular design improves the redundancy fault tolerance of this power supply and reduces its failure rate. When this power source is used as an excitation source for plasma production, and the output high voltage pulse waveform is stable, the power supply can be conveniently adjusted according to different load. When the voltage and frequency change, the mode of the discharge is different.
2019,
31: 085101.
doi: 10.11884/HPLPB201931.190033
Abstract:
In the simulation of the accelerator magnet support system, the parts connected to the ground by the magnet bracket are usually treated as “fixed”, but in some cases, this treatment will cause a large error between the simulation results and the measurement results. This paper proposes an indirect method to measure the contact stiffness of rough surface, accurately quantify the contact stiffness of rough surface, and make the simulation of the whole system well match with the test results. Based on the contact stiffness model, ANSYS finite element simulation method and modal test method, the accuracy of indirect measurement method was verified by taking the test piece of anchor bolt fixation method as an example, so that the contact stiffness was accurately quantified. This method can also provide a basis for improving the overall stiffness of the accelerator magnet support system.
In the simulation of the accelerator magnet support system, the parts connected to the ground by the magnet bracket are usually treated as “fixed”, but in some cases, this treatment will cause a large error between the simulation results and the measurement results. This paper proposes an indirect method to measure the contact stiffness of rough surface, accurately quantify the contact stiffness of rough surface, and make the simulation of the whole system well match with the test results. Based on the contact stiffness model, ANSYS finite element simulation method and modal test method, the accuracy of indirect measurement method was verified by taking the test piece of anchor bolt fixation method as an example, so that the contact stiffness was accurately quantified. This method can also provide a basis for improving the overall stiffness of the accelerator magnet support system.
2019,
31: 085102.
doi: 10.11884/HPLPB201931.190064
Abstract:
In the design phase of BEPCII, the impedance is limited in terms of beam instabilities and parasitic mode loss. However, the parasitic mode loss has been one of the unfavorable factors affecting high beam current operation of BEPCII. This paper describes a measurement of the parasitic mode loss in BEPCII e- ring, which is based on a small change of synchronous phase shift with beam current, the beam power measurement and the power of higher order mode absorber. The measurement results with two different methods of the total parasitic mode loss are repetitive and reliable. Moreover, the total parasitic mode loss of e- ring is 4-5 times as large as the parasitic mode loss of the superconducting cavity.
In the design phase of BEPCII, the impedance is limited in terms of beam instabilities and parasitic mode loss. However, the parasitic mode loss has been one of the unfavorable factors affecting high beam current operation of BEPCII. This paper describes a measurement of the parasitic mode loss in BEPCII e- ring, which is based on a small change of synchronous phase shift with beam current, the beam power measurement and the power of higher order mode absorber. The measurement results with two different methods of the total parasitic mode loss are repetitive and reliable. Moreover, the total parasitic mode loss of e- ring is 4-5 times as large as the parasitic mode loss of the superconducting cavity.
2019,
31: 085103.
doi: 10.11884/HPLPB201931.190041
Abstract:
A new beam loss monitor system based on embedded EPICS is developed for the top-off upgrade of HLS-Ⅱ, to monitor the position and value of beam loss of storage ring. The electron shower signals are obtained by the double PIN photodiode detectors around the storage ring, then acquired by the new BLM processors, where the beam loss signals are analysed and distributed to the accelerator control network, by embedded EPICS on embedded Linux system of the BLM processors, and the beam loss data could be obtained in the central control room. The new BLM system could actuate the self-checking function of the double PIN photodiode detectors, eliminate hidden malfunction of the detectors, and improve stability and reliability of the whole system. Preliminary operation shows that the new BLM system can meet the needs of the top-off upgrade of HLS-Ⅱ.
A new beam loss monitor system based on embedded EPICS is developed for the top-off upgrade of HLS-Ⅱ, to monitor the position and value of beam loss of storage ring. The electron shower signals are obtained by the double PIN photodiode detectors around the storage ring, then acquired by the new BLM processors, where the beam loss signals are analysed and distributed to the accelerator control network, by embedded EPICS on embedded Linux system of the BLM processors, and the beam loss data could be obtained in the central control room. The new BLM system could actuate the self-checking function of the double PIN photodiode detectors, eliminate hidden malfunction of the detectors, and improve stability and reliability of the whole system. Preliminary operation shows that the new BLM system can meet the needs of the top-off upgrade of HLS-Ⅱ.
2019,
31: 085104.
doi: 10.11884/HPLPB201931.190086
Abstract:
To improve the measurement accuracy of peak power meter of BEPCII linear accelerator, further reduce the response time of reflection protection alarm and provide real-time waveform detection means, the RF detector chip based on integrated circuit has been investigated, and a new type of peak power meter based on logarithmic detector, field programmable gate array (FPGA), and high speed analog-to-digital converter (ADC) has been developed. By the multi-point calibration at different operating frequencies, the segmented transfer function is established, and finally the calibration of power meter is realized. The prototype of power meter has been tested systematically. The results show that the error of power measurement in laboratory is ±0.2 dB and the response time of reflection protection in BEPCII online test is about 2 μs. It has been running steadily online for a period of time. In addition, the new peak power meter has the characteristics of wide linear dynamic range, reflection protection alarm, built-in dual-channel RF detectors, dual interface for users and engineers, real-time waveform display, waveform power measurement at any point, etc.
To improve the measurement accuracy of peak power meter of BEPCII linear accelerator, further reduce the response time of reflection protection alarm and provide real-time waveform detection means, the RF detector chip based on integrated circuit has been investigated, and a new type of peak power meter based on logarithmic detector, field programmable gate array (FPGA), and high speed analog-to-digital converter (ADC) has been developed. By the multi-point calibration at different operating frequencies, the segmented transfer function is established, and finally the calibration of power meter is realized. The prototype of power meter has been tested systematically. The results show that the error of power measurement in laboratory is ±0.2 dB and the response time of reflection protection in BEPCII online test is about 2 μs. It has been running steadily online for a period of time. In addition, the new peak power meter has the characteristics of wide linear dynamic range, reflection protection alarm, built-in dual-channel RF detectors, dual interface for users and engineers, real-time waveform display, waveform power measurement at any point, etc.
2019,
31: 085105.
doi: 10.11884/HPLPB201931.190078
Abstract:
Taking BEPCII superconducting RF (SRF) cavity as an example, this paper analyzes several common causes of the SRF cavity failure, including hardware failure of RF system, beam loss and mechanical failure of the tuner, by combining theoretical calculation and experimental observation of the main RF parameters such as the cavity voltage, the input power and the tuning angle, etc. It focuses on the SRF failure caused by the abnormal motion of the tuner. These analyses provide an important reference for reducing BEPCII RF system faults and increasing the operational reliability of BEPCII.
Taking BEPCII superconducting RF (SRF) cavity as an example, this paper analyzes several common causes of the SRF cavity failure, including hardware failure of RF system, beam loss and mechanical failure of the tuner, by combining theoretical calculation and experimental observation of the main RF parameters such as the cavity voltage, the input power and the tuning angle, etc. It focuses on the SRF failure caused by the abnormal motion of the tuner. These analyses provide an important reference for reducing BEPCII RF system faults and increasing the operational reliability of BEPCII.
2019,
31: 085106.
doi: 10.11884/HPLPB201931.190066
Abstract:
Aimed to prove the capture efficiency of ion source injected Interdigital H mode (IH) cavity, a short linac is under construction in Institute of Fluid Physics, CAEP. Protons could be accelerated from 0.04 MeV to 2.4 MeV with this linac. The cavity was manufactured, cold test and cavity tuning were performed. After frequency tuning and field tuning, both frequency error and voltage distribution error were successfully decreased. Simulation results shows that capture efficiency of this cavity was increased from 16% to 34% by cavity tuning. The cavity parameters have reached the tuning objective and beam test will be carried out.
Aimed to prove the capture efficiency of ion source injected Interdigital H mode (IH) cavity, a short linac is under construction in Institute of Fluid Physics, CAEP. Protons could be accelerated from 0.04 MeV to 2.4 MeV with this linac. The cavity was manufactured, cold test and cavity tuning were performed. After frequency tuning and field tuning, both frequency error and voltage distribution error were successfully decreased. Simulation results shows that capture efficiency of this cavity was increased from 16% to 34% by cavity tuning. The cavity parameters have reached the tuning objective and beam test will be carried out.
2019,
31: 086001.
doi: 10.11884/HPLPB201931.190050
Abstract:
China fusion engineering test reactor(CFETR) is a magnetic confinement fusion device designed, which used high current magnetic field in the superconducting coil to generate high intensity magnetic field, thus constraining the high-temperature plasma to conduct fusion experiments. Therefore, the reliability of quench protection system, especially DC protection switch, is very important for the protection of the superconducting coil. However, the reliability of the DC protection switch is affected by many factors, including the action time, the speed of arc extinguishing, the current drop rate of the switch and the voltage rise rate around zero-crossing point. In the literature on quench protection system design of Tokamak devices such as international thermonuclear experimental reactor (ITER), the influence of circuit stray parameters on switch reliability is rarely described, and the influence of discharge circuit to quench protection system is less. However, the larger stray parameters of discharge circuit will greatly reduce the operational reliability of the DC protection switch and even lead to failure and damage of the switch. In this paper, the influence of the parameters of the discharge branch on the reliability of the quench protection system in CFETR is analyzed. Firstly, the influence factors and the influence trend are analyzed by theoretical calculation, and the correctness of the theoretical analysis of the current and voltage of each branch is carried out in a set of simulations. The simulation results show that when the stray inductance of discharge branch is large, the turnoff parameters of each branch will be greatly impacted, which directly affects the reliability quench protection system in CFETR.
China fusion engineering test reactor(CFETR) is a magnetic confinement fusion device designed, which used high current magnetic field in the superconducting coil to generate high intensity magnetic field, thus constraining the high-temperature plasma to conduct fusion experiments. Therefore, the reliability of quench protection system, especially DC protection switch, is very important for the protection of the superconducting coil. However, the reliability of the DC protection switch is affected by many factors, including the action time, the speed of arc extinguishing, the current drop rate of the switch and the voltage rise rate around zero-crossing point. In the literature on quench protection system design of Tokamak devices such as international thermonuclear experimental reactor (ITER), the influence of circuit stray parameters on switch reliability is rarely described, and the influence of discharge circuit to quench protection system is less. However, the larger stray parameters of discharge circuit will greatly reduce the operational reliability of the DC protection switch and even lead to failure and damage of the switch. In this paper, the influence of the parameters of the discharge branch on the reliability of the quench protection system in CFETR is analyzed. Firstly, the influence factors and the influence trend are analyzed by theoretical calculation, and the correctness of the theoretical analysis of the current and voltage of each branch is carried out in a set of simulations. The simulation results show that when the stray inductance of discharge branch is large, the turnoff parameters of each branch will be greatly impacted, which directly affects the reliability quench protection system in CFETR.
2019,
31: 086002.
doi: 10.11884/HPLPB201931.180345
Abstract:
To investigate 4H-SiC detector’s resistance to gamma irradiation, the detector was irradiated by 60Co gamma-ray(about 4×105 Ci), and the maximum cumulative dose was 1 MGy. The detector’s I-V characteristics and its performance in detecting charged particles were tested after gamma irradiation. The forward current increased and the reverse current decreased as the cumulative dose was increased. The ideal factor and Schottky barrier height were extracted from forward I-V curves, and the result showed that ideal factor increased and Schottky barrier height decreased after irradiation. The detector was exposed to 241Am source, and it was found that the detector’s performance degraded slightly after gamma irradiation. However, the detector behaved well in detection after it received gamma exposures at a dose of 1 MGy: its charge collection efficiency was 93.55% and its energy resolution was 2.32% in detecting alpha particles of 5.486 MeV. Therefore it has been proved that 4H-SiC detector has good resistance to gamma irradiation.
To investigate 4H-SiC detector’s resistance to gamma irradiation, the detector was irradiated by 60Co gamma-ray(about 4×105 Ci), and the maximum cumulative dose was 1 MGy. The detector’s I-V characteristics and its performance in detecting charged particles were tested after gamma irradiation. The forward current increased and the reverse current decreased as the cumulative dose was increased. The ideal factor and Schottky barrier height were extracted from forward I-V curves, and the result showed that ideal factor increased and Schottky barrier height decreased after irradiation. The detector was exposed to 241Am source, and it was found that the detector’s performance degraded slightly after gamma irradiation. However, the detector behaved well in detection after it received gamma exposures at a dose of 1 MGy: its charge collection efficiency was 93.55% and its energy resolution was 2.32% in detecting alpha particles of 5.486 MeV. Therefore it has been proved that 4H-SiC detector has good resistance to gamma irradiation.
2019,
31: 1-3.
