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RSS2020 Vol. 32, No. 6
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2020,
32: 1-2.
2020,
32: 061001.
doi: 10.11884/HPLPB202032.190348
Abstract:
The influence of tracking jitter on the far-field spot of turbulent atmospheric transmission is analyzed. Based on Maxwell's electromagnetic field theory, the Fried coherence diameter is used to describe the atmospheric turbulence, and the far-field expression of the transmitted beam due to optical axis deviation caused by tracking jitter is derived. The method of phase screen is used to simulate the tilt phase caused by tracking jitter and phase modulation caused by atmospheric refractive index fluctuation. Fast Fourier Transform Subharmonic Method is used to simulate the transmission process. The changes of miss distance of far-field spot under different tracking jitter and turbulence intensity and the echo probability of the simulated targets in different sizes are analyzed. The analysis results show that when the transmission distance is 10 km, the miss distance of far-field spot caused by strong turbulence can reach dozens of microradians. When the tracking jitter is large, the influence of turbulence on the miss distance is very small. Finally, for the simulation target of specific size, the control range of the transmission system tracking jitter is given.
The influence of tracking jitter on the far-field spot of turbulent atmospheric transmission is analyzed. Based on Maxwell's electromagnetic field theory, the Fried coherence diameter is used to describe the atmospheric turbulence, and the far-field expression of the transmitted beam due to optical axis deviation caused by tracking jitter is derived. The method of phase screen is used to simulate the tilt phase caused by tracking jitter and phase modulation caused by atmospheric refractive index fluctuation. Fast Fourier Transform Subharmonic Method is used to simulate the transmission process. The changes of miss distance of far-field spot under different tracking jitter and turbulence intensity and the echo probability of the simulated targets in different sizes are analyzed. The analysis results show that when the transmission distance is 10 km, the miss distance of far-field spot caused by strong turbulence can reach dozens of microradians. When the tracking jitter is large, the influence of turbulence on the miss distance is very small. Finally, for the simulation target of specific size, the control range of the transmission system tracking jitter is given.
2020,
32: 061002.
doi: 10.11884/HPLPB202032.200046
Abstract:
In the field of inertial confinement fusion (ICF), UV laser can effectively improve the beam-target coupling efficiency and suppress the hydrodynamic instability of laser plasma interaction. Using large aperture KDP crystal or KD*P crystal to triple the frequency of laser created by high power solid-state laser facility (wavelength is 1 μm) is an effective way to obtain high power UV laser output. At present, most high power laser facilities take method of I/II type third harmonic generation. The phase matching condition is required in the third harmonic generation, and the conversion efficiency is easily influenced by the detuned angle of crystals. The quality of the return light spot of crystals’ surface can reflect the state of wavefront distortion, and then evaluate the degree of angle-detuning at the crystal. The factors which create detuned angle are analyzed and judged, within which the surface shape distortion of crystals (PV is more than 30 μm) caused by clamping and gravity is the main part. According to improving the surface shape of crystals (PV is less than 10 μm) in the experiment, the quality of the return light spot of crystals has been significantly improved, and then the conversion efficiency of third harmonic generation has an obvious increase.
In the field of inertial confinement fusion (ICF), UV laser can effectively improve the beam-target coupling efficiency and suppress the hydrodynamic instability of laser plasma interaction. Using large aperture KDP crystal or KD*P crystal to triple the frequency of laser created by high power solid-state laser facility (wavelength is 1 μm) is an effective way to obtain high power UV laser output. At present, most high power laser facilities take method of I/II type third harmonic generation. The phase matching condition is required in the third harmonic generation, and the conversion efficiency is easily influenced by the detuned angle of crystals. The quality of the return light spot of crystals’ surface can reflect the state of wavefront distortion, and then evaluate the degree of angle-detuning at the crystal. The factors which create detuned angle are analyzed and judged, within which the surface shape distortion of crystals (PV is more than 30 μm) caused by clamping and gravity is the main part. According to improving the surface shape of crystals (PV is less than 10 μm) in the experiment, the quality of the return light spot of crystals has been significantly improved, and then the conversion efficiency of third harmonic generation has an obvious increase.
2020,
32: 061003.
doi: 10.11884/HPLPB202032.190455
Abstract:
Under normal pressure and temperature, aluminum alloy in air can be excited by Nd:YAG nanosecond laser with wavelength 532 nm, the collection and photoelectric conversion of the plasma emission spectrum are executed by a high-resolution spectrometer and an ICCD. This paper studies the influences of laser energy, ICCD gate delay and lens-to-sample distance (LTSD) on the spectral intensity and plasma electron temperature as well as the physical mechanism. It is demonstrated that the spectral intensity and electron temperature increase with the increase of laser energy at the fixed ICCD gate delay and LTSD. The calculated results show that when the laser energy increases from 20 mJ to 160 mJ, the line intensities of the atomic spectral lines Al I 396.15 nm, Mg I 518.36 nm, and the Mg II 279.54 nm ion spectral line are 12.83, 6.45 and 10.56 times higher than that of 20 mJ, respectively. At the fixed laser energy and LTSD, when the ICCD gate delay changes within 100−4 000 ns, the spectral intensity and plasma electron temperature decay exponential with the increase of ICCD gate delay. With the same ICCD gate delay and laser energy, the influence mechanism of LTSD on plasma parameters was studied by using a focusing lens with focal length of 75 mm. It is demonstrated that the lens-to-sample distance has a considerable impact on the spectral intensity and plasma electron temperature. The results indicate that the change of the spectral intensity is consistent with that of the plasma electron temperature. The curves have two peaks at the distances of 73 mm and 79 mm from sample surface, and the values reach their maximum at 73 mm.
Under normal pressure and temperature, aluminum alloy in air can be excited by Nd:YAG nanosecond laser with wavelength 532 nm, the collection and photoelectric conversion of the plasma emission spectrum are executed by a high-resolution spectrometer and an ICCD. This paper studies the influences of laser energy, ICCD gate delay and lens-to-sample distance (LTSD) on the spectral intensity and plasma electron temperature as well as the physical mechanism. It is demonstrated that the spectral intensity and electron temperature increase with the increase of laser energy at the fixed ICCD gate delay and LTSD. The calculated results show that when the laser energy increases from 20 mJ to 160 mJ, the line intensities of the atomic spectral lines Al I 396.15 nm, Mg I 518.36 nm, and the Mg II 279.54 nm ion spectral line are 12.83, 6.45 and 10.56 times higher than that of 20 mJ, respectively. At the fixed laser energy and LTSD, when the ICCD gate delay changes within 100−4 000 ns, the spectral intensity and plasma electron temperature decay exponential with the increase of ICCD gate delay. With the same ICCD gate delay and laser energy, the influence mechanism of LTSD on plasma parameters was studied by using a focusing lens with focal length of 75 mm. It is demonstrated that the lens-to-sample distance has a considerable impact on the spectral intensity and plasma electron temperature. The results indicate that the change of the spectral intensity is consistent with that of the plasma electron temperature. The curves have two peaks at the distances of 73 mm and 79 mm from sample surface, and the values reach their maximum at 73 mm.
2020,
32: 062001.
doi: 10.11884/HPLPB202032.190486
Abstract:
Based on the diagnostic requirements of high spatial resolution and high energy spectral resolution in the implosion compression stage of laser inertial confinement fusion (ICF), this paper proposes a large field of view and monochromatic imaging system, which combines KB microscope and diffractive crystal. Under the laboratory condition, the grid is backlight imaged by using the Fe target X-ray tube, with KB microscope and high oriented pyrolytic graphite (HOPG). The imaging results after the crystal energy selection show that the field of view of the system can reach 800 μm, and the resolution of high-resolution area imaging is 37 μm. The detecting results show that the energy resolution of the system is 28, which verifies the monochromatic performance of the system. The system takes into account large field of view, spatial resolution and energy resolution, and has an important application in the research of hot spot structure and mixing effect in the experiment of implosion compression stage.
Based on the diagnostic requirements of high spatial resolution and high energy spectral resolution in the implosion compression stage of laser inertial confinement fusion (ICF), this paper proposes a large field of view and monochromatic imaging system, which combines KB microscope and diffractive crystal. Under the laboratory condition, the grid is backlight imaged by using the Fe target X-ray tube, with KB microscope and high oriented pyrolytic graphite (HOPG). The imaging results after the crystal energy selection show that the field of view of the system can reach 800 μm, and the resolution of high-resolution area imaging is 37 μm. The detecting results show that the energy resolution of the system is 28, which verifies the monochromatic performance of the system. The system takes into account large field of view, spatial resolution and energy resolution, and has an important application in the research of hot spot structure and mixing effect in the experiment of implosion compression stage.
2020,
32: 062002.
doi: 10.11884/HPLPB202032.190352
Abstract:
Magnetized Liner Inertial Fusion (MagLIF) concept has promising potentials for future energy source (Phys.Plasmas, 2014, 21:072711), it is widely applicable to large-scale pulsed power generators such as the Primary Test Stand (PTS) facility (10 MA, 100 ns). In this context, we’ve developed a zero-dimensional (0D) MagLIF simulation code basing on magneto-hydrodynamic (MHD) equations and Deuterium-Tritium (DT) fusion models. Relationships between fusion products and initial setups (magnetic field Bz0, preheat temperature T0 and so on) are explored using this code, results show optimal parameters existing under given inputs, which are very helpful for future experimental designs. Specifically, according to our simulations, critical driving current (＞21.2 MA) is essential for fuel (50∶50 DT) energy to reach breakeven, which infers that PTS facility may not be suitable for integrated MagLIF experiments. Series of calculations are performed to confirm this inference, and more practical aluminum liner experiments are proposed and designed.
Magnetized Liner Inertial Fusion (MagLIF) concept has promising potentials for future energy source (Phys.Plasmas, 2014, 21:072711), it is widely applicable to large-scale pulsed power generators such as the Primary Test Stand (PTS) facility (10 MA, 100 ns). In this context, we’ve developed a zero-dimensional (0D) MagLIF simulation code basing on magneto-hydrodynamic (MHD) equations and Deuterium-Tritium (DT) fusion models. Relationships between fusion products and initial setups (magnetic field Bz0, preheat temperature T0 and so on) are explored using this code, results show optimal parameters existing under given inputs, which are very helpful for future experimental designs. Specifically, according to our simulations, critical driving current (＞21.2 MA) is essential for fuel (50∶50 DT) energy to reach breakeven, which infers that PTS facility may not be suitable for integrated MagLIF experiments. Series of calculations are performed to confirm this inference, and more practical aluminum liner experiments are proposed and designed.
2020,
32: 063001.
doi: 10.11884/HPLPB202032.200079
Abstract:
This paper presents a review summary of the current state-of-the-art stirring in reverberation chamber (RC). An RC is an important device for conducting electromagnetic compatibility, electromagnetic effect testing and wireless channel simulation in a limited space. The stirring technique is the soul of a RC. The focus is introducing the research history and current situation of the stirring techniques at home and abroad from two perspectives, i.e. changing the boundary conditions and the configuration of the excitation source in an RC. In particular, some representative implementation schemes are discussed, and the characteristics of various methods are summarized. Finally, the research progress of mixed stirring techniques is also introduced.
2020,
32: 063002.
doi: 10.11884/HPLPB202032.190364
Abstract:
This paper proposes a new-type periodical permanent magnet (PPM) focus system, each half period of which is composed of 1 magnetic pole and 5 permanent magnets, and the first, the third and the fifth magnets have reverse magnetization with the second and the fourth magnets. Besides, any two magnets spaced half period have inverse magnetization with each other. The new-type PPM focus system is modeled and calculated by MTSS2018, the results show that the axial component Bz of the magnetic induction intensity on the axis has conspicuous amplitude of the third and the fifth space harmonics, and Bz rises steeply after it reaches zero, so Bz has a profile very approximate to the periodical rectangular shape. An electron gun under the condition of the above calculated Bz is calculated by MTSS2018 too, a beam with 22 kV of voltage, 215 mA current and 0.08 mm of maximum beam radius is obtained, which meets the demand of G band extended interaction klystron (EIK). In the calculations the peak value of Bz is only 1.2\begin{document}$ \sqrt 2 $\end{document} ![]()
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This paper proposes a new-type periodical permanent magnet (PPM) focus system, each half period of which is composed of 1 magnetic pole and 5 permanent magnets, and the first, the third and the fifth magnets have reverse magnetization with the second and the fourth magnets. Besides, any two magnets spaced half period have inverse magnetization with each other. The new-type PPM focus system is modeled and calculated by MTSS2018, the results show that the axial component Bz of the magnetic induction intensity on the axis has conspicuous amplitude of the third and the fifth space harmonics, and Bz rises steeply after it reaches zero, so Bz has a profile very approximate to the periodical rectangular shape. An electron gun under the condition of the above calculated Bz is calculated by MTSS2018 too, a beam with 22 kV of voltage, 215 mA current and 0.08 mm of maximum beam radius is obtained, which meets the demand of G band extended interaction klystron (EIK). In the calculations the peak value of Bz is only 1.2
2020,
32: 063003.
doi: 10.11884/HPLPB202032.190174
Abstract:
On the basis of equivalent circuit of PIN limiter, we constructed an equivalent circuit model for the simulation of high power microwave effect of PIN limiter. The response property of PIN limiter under the excitation of single high power microwave pulse is studied by using the equivalent circuit model and injection experiment. The evolution of the limiting duration with the injected pulse power and pulse width of the HPM is obtained. In addition, the limiting duration process is theoretically analyzed. Both the simulation and experiment show that: the limiting duration of the PIN limiter increases with the increase of the input power and pulse width of a single high microwave pulse. The experiment matches simulation very well. The ADS equivalent circuit model used in this study can be extended to investigate the transient effect of high power microwave.
On the basis of equivalent circuit of PIN limiter, we constructed an equivalent circuit model for the simulation of high power microwave effect of PIN limiter. The response property of PIN limiter under the excitation of single high power microwave pulse is studied by using the equivalent circuit model and injection experiment. The evolution of the limiting duration with the injected pulse power and pulse width of the HPM is obtained. In addition, the limiting duration process is theoretically analyzed. Both the simulation and experiment show that: the limiting duration of the PIN limiter increases with the increase of the input power and pulse width of a single high microwave pulse. The experiment matches simulation very well. The ADS equivalent circuit model used in this study can be extended to investigate the transient effect of high power microwave.
2020,
32: 063005.
doi: 10.11884/HPLPB202032.200014
Abstract:
In this paper, an improved iterative fast Fourier transform (IFFT) based on the mutual coupling compensation matrix (MCCM) is introduced and applied to the low-sidelobe synthesis of wide-angle scanning phased arrays. Firstly, the MCCM is integrated into the IFFT to take into account the mutual coupling effects between the array elements. In this situation, the far field of an array which takes the mutual coupling into calculation can satisfy the principle of pattern multiplication. Secondly, a wide-beam element antenna backed by a substrate integrated waveguide (SIW) cavity is proposed. The proposed wide-beam antenna can simultaneously excite the TE110 and TE210 modes to expand its operation bandwidth. Based on this element, three wide-angle scanning phased array antennas with 35, 75 and 100 elements are formed and calculated. Finally, the proposed IFFT algorithm is used in the low-sidelobe synthesis of the three phased arrays. Compared with the results of the genetic algorithm based on the active element patterns, this algorithm can realize low-sidelobe performance within the scanning range from −60° to 60° at faster speed.
In this paper, an improved iterative fast Fourier transform (IFFT) based on the mutual coupling compensation matrix (MCCM) is introduced and applied to the low-sidelobe synthesis of wide-angle scanning phased arrays. Firstly, the MCCM is integrated into the IFFT to take into account the mutual coupling effects between the array elements. In this situation, the far field of an array which takes the mutual coupling into calculation can satisfy the principle of pattern multiplication. Secondly, a wide-beam element antenna backed by a substrate integrated waveguide (SIW) cavity is proposed. The proposed wide-beam antenna can simultaneously excite the TE110 and TE210 modes to expand its operation bandwidth. Based on this element, three wide-angle scanning phased array antennas with 35, 75 and 100 elements are formed and calculated. Finally, the proposed IFFT algorithm is used in the low-sidelobe synthesis of the three phased arrays. Compared with the results of the genetic algorithm based on the active element patterns, this algorithm can realize low-sidelobe performance within the scanning range from −60° to 60° at faster speed.
2020,
32: 063006.
doi: 10.11884/HPLPB202032.190421
Abstract:
A fully-differential master-slave track-and-hold amplifier (MS-THA), with 20 GHz bandwidth is designed and fabricated using 0.13 μm SiGe BiCMOS technology. The MS-THA employs conventional switched-emitter-follower (SEF) as track-and-hold core circuit, Cherryhooper circuits as band-boosting of input buffer and output buffer. To verify the validity of the above circuits, a single-stage THA is designed together with the MS-THA. Operating with a single +3.3 V supply, 0 V input direct-voltage, 2 G/s sampling and −3 dBm input power, the MS-THA achieves a single-ended spurious free dynamic range (SFDR) of less than −23.5 dB at frequency of up to 20 GHz, and total power consumption of about 300 mW.
A fully-differential master-slave track-and-hold amplifier (MS-THA), with 20 GHz bandwidth is designed and fabricated using 0.13 μm SiGe BiCMOS technology. The MS-THA employs conventional switched-emitter-follower (SEF) as track-and-hold core circuit, Cherryhooper circuits as band-boosting of input buffer and output buffer. To verify the validity of the above circuits, a single-stage THA is designed together with the MS-THA. Operating with a single +3.3 V supply, 0 V input direct-voltage, 2 G/s sampling and −3 dBm input power, the MS-THA achieves a single-ended spurious free dynamic range (SFDR) of less than −23.5 dB at frequency of up to 20 GHz, and total power consumption of about 300 mW.
2020,
32: 063007.
doi: 10.11884/HPLPB202032.190443
Abstract:
This paper presents an ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna, which has high isolation and double band-notch in the UWB band. The MIMO antenna consists of two half-cutting UWB antenna units which have high isolation (S21＞25 dB) because of the use of a novel fence-type decoupling structure on the bottom plate of the antenna. In addition, two “L”shaped slots are etched on the antenna radiation patch, and the characteristic of the double band-notch are realized. The interference of the 802.16 WiMAX (3.2−3.7 GHz) and the WLAN (5.15−5.85 GHz) signal to the antenna system is suppressed, respectively. The experimental results show that the antenna has high isolation and a low envelope correlation coefficient (ECC＜0.004) in the UWB band. The first notch band is 3.0−3.7 GHz and the second notch band is 5.1−5.8 GHz, which effectively suppresses the interference of WiMAX and WLAN signals.
This paper presents an ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna, which has high isolation and double band-notch in the UWB band. The MIMO antenna consists of two half-cutting UWB antenna units which have high isolation (S21＞25 dB) because of the use of a novel fence-type decoupling structure on the bottom plate of the antenna. In addition, two “L”shaped slots are etched on the antenna radiation patch, and the characteristic of the double band-notch are realized. The interference of the 802.16 WiMAX (3.2−3.7 GHz) and the WLAN (5.15−5.85 GHz) signal to the antenna system is suppressed, respectively. The experimental results show that the antenna has high isolation and a low envelope correlation coefficient (ECC＜0.004) in the UWB band. The first notch band is 3.0−3.7 GHz and the second notch band is 5.1−5.8 GHz, which effectively suppresses the interference of WiMAX and WLAN signals.
2020,
32: 064001.
doi: 10.11884/HPLPB202032.190415
Abstract:
The ultrafast electron diffraction (UED) facility located in Shanghai Jiao Tong University, driven by a linear electron accelerator, has a photocathode RF gun. Sometimes an RF gun arc might happen during the accelerator running, causing a cavity detuning and beam loss, then resulting in a beam energy change. It will take a long time for the beam to restore its previous energy, which will influence utilization of the facility. An energy feedback is applied to low level RF (LLRF) system after improvement of amplitude-phase loop, using a real-time feedback of the beam center position to regulate the output amplitude of LLRF, to ensure the stability of beam energy and RF gun accelerating field. A long period of stability testing indicates, that beam energy can return to its original value quickly after arc occurence, energy jitter is improved from 4.293 3×10−4 (RMS) to 2.855 7×10−4 (RMS), realizing a long term stability of beam energy.
The ultrafast electron diffraction (UED) facility located in Shanghai Jiao Tong University, driven by a linear electron accelerator, has a photocathode RF gun. Sometimes an RF gun arc might happen during the accelerator running, causing a cavity detuning and beam loss, then resulting in a beam energy change. It will take a long time for the beam to restore its previous energy, which will influence utilization of the facility. An energy feedback is applied to low level RF (LLRF) system after improvement of amplitude-phase loop, using a real-time feedback of the beam center position to regulate the output amplitude of LLRF, to ensure the stability of beam energy and RF gun accelerating field. A long period of stability testing indicates, that beam energy can return to its original value quickly after arc occurence, energy jitter is improved from 4.293 3×10−4 (RMS) to 2.855 7×10−4 (RMS), realizing a long term stability of beam energy.
2020,
32: 064002.
doi: 10.11884/HPLPB202032.190425
Abstract:
This paper introduces the approach to design a stripline beam position monitor(BPM) for the project of “THz High-flux Material Physical Property Testing System”, which is hosted by National Synchrotron Radiation Laboratory. Due to the non-orthogonal symmetric vacuum chamber at the exit of the undulator, two kinds of stripline BPMs with rectangular and racetrack vacuum chamber respectively are considered as an option, and compared with the traditional BPM with circular vacuum chamber. The modeling and simulation are based on the boundary element method via Matlab. The simulation results show that the sensitivities of BPMs with rectangular and racetrack vacuum chamber are improved by 30%, the impedance matching errors are reduced by 20%, and the beam position fitting errors are reduced by 80%, compared with the traditional BPM with circular vacuum chamber. Considering the accuracy of processing, the stripline BPM with rectangular vacuum chamber is more suitable for the project.
This paper introduces the approach to design a stripline beam position monitor(BPM) for the project of “THz High-flux Material Physical Property Testing System”, which is hosted by National Synchrotron Radiation Laboratory. Due to the non-orthogonal symmetric vacuum chamber at the exit of the undulator, two kinds of stripline BPMs with rectangular and racetrack vacuum chamber respectively are considered as an option, and compared with the traditional BPM with circular vacuum chamber. The modeling and simulation are based on the boundary element method via Matlab. The simulation results show that the sensitivities of BPMs with rectangular and racetrack vacuum chamber are improved by 30%, the impedance matching errors are reduced by 20%, and the beam position fitting errors are reduced by 80%, compared with the traditional BPM with circular vacuum chamber. Considering the accuracy of processing, the stripline BPM with rectangular vacuum chamber is more suitable for the project.
2020,
32: 064003.
doi: 10.11884/HPLPB202032.190398
Abstract:
The research of magnetic flux expulsion of 1.3 GHz single-cell superconducting cavity has been carried out with a new set of high precision magnetic measuring and compensating system, combining with 2 K vertical test system of IHEP. The magnetic field at the equator of cavity can be measured with the system and compensated to less than 5.0×10−8 T. The magnetic flux expulsion effect of superconducting cavity under different surface temperature gradient is measured and analyzed. The rf performance of the cavity pinned with magnetic flux is tested, and the sensitivity of superconducting cavity resistance to magnetic flux pinning and the surface resistance of superconducting cavity under different electric field gradients are studied accordingly. The results show that the developed high precision magnetic field measuring and compensating system can meet the research needs of magnetic flux expulsion of superconducting cavity. Higher surface temperature gradient of superconducting cavity is beneficial to the magnetic flux expulsion. The sensitivity of flux pinning resistance increases with the increase of electric field. The research has also laid a foundation for the development of superconducting cavity.
The research of magnetic flux expulsion of 1.3 GHz single-cell superconducting cavity has been carried out with a new set of high precision magnetic measuring and compensating system, combining with 2 K vertical test system of IHEP. The magnetic field at the equator of cavity can be measured with the system and compensated to less than 5.0×10−8 T. The magnetic flux expulsion effect of superconducting cavity under different surface temperature gradient is measured and analyzed. The rf performance of the cavity pinned with magnetic flux is tested, and the sensitivity of superconducting cavity resistance to magnetic flux pinning and the surface resistance of superconducting cavity under different electric field gradients are studied accordingly. The results show that the developed high precision magnetic field measuring and compensating system can meet the research needs of magnetic flux expulsion of superconducting cavity. Higher surface temperature gradient of superconducting cavity is beneficial to the magnetic flux expulsion. The sensitivity of flux pinning resistance increases with the increase of electric field. The research has also laid a foundation for the development of superconducting cavity.
2020,
32: 064004.
doi: 10.11884/HPLPB202032.200036
Abstract:
The Shanghai Advanced Proton Therapy Facility (APTR) project, proposed by the Shanghai Institute of Applied Physics (SINAP) of Chinese Academy of Sciences, has finished in the commissioning stage. As the key component of APTR complex, the injector system is upgraded to accelerate proton beam to 7.0 MeV in the context of comprehensive localization and miniaturization. To pre-accelerate, longitudinally bunch and transversely focus the low-energy proton beam from ion source, a pre-injecting system Radio-Frequency Quadruple (RFQ) was designed. Based on fast bunching strategy, this RFQ, operated at 325 MHz, accelerates proton particles to 3.0 MeV. The phase advance has been taken into consideration, and parametric resonance has been carefully avoided by adjusting the vane parameters. The whole transmission efficiency has been optimized to 98.0% to meet the machining requirements and the emittance growth in horizontal and vertical directions are about 1.2%, 3.3% along the entire cavity. This paper mainly introduces the beam dynamics design schemes, main parameter selections, simulation results and tolerance analysis. It can provide important theoretical base for linear injection system of proton synchrotron-based therapy facility.
The Shanghai Advanced Proton Therapy Facility (APTR) project, proposed by the Shanghai Institute of Applied Physics (SINAP) of Chinese Academy of Sciences, has finished in the commissioning stage. As the key component of APTR complex, the injector system is upgraded to accelerate proton beam to 7.0 MeV in the context of comprehensive localization and miniaturization. To pre-accelerate, longitudinally bunch and transversely focus the low-energy proton beam from ion source, a pre-injecting system Radio-Frequency Quadruple (RFQ) was designed. Based on fast bunching strategy, this RFQ, operated at 325 MHz, accelerates proton particles to 3.0 MeV. The phase advance has been taken into consideration, and parametric resonance has been carefully avoided by adjusting the vane parameters. The whole transmission efficiency has been optimized to 98.0% to meet the machining requirements and the emittance growth in horizontal and vertical directions are about 1.2%, 3.3% along the entire cavity. This paper mainly introduces the beam dynamics design schemes, main parameter selections, simulation results and tolerance analysis. It can provide important theoretical base for linear injection system of proton synchrotron-based therapy facility.
2020,
32: 065001.
doi: 10.11884/HPLPB202032.190374
Abstract:
Pulse forming network (PFN) is often used in high-power solid-state modulator, microwave driver and laser exciter to obtain high voltage and long pulse output with wide flat-top. Aiming at the common used Rayleigh PFN with equal inductor and capacitor, according to the application requirement of wide flat-top and low ripple, the optimal design technology of PFN is studied, and the optimization algorithm based on simplex optimization method is proposed. The work is mainly carried out in two cases: first, the capacitance is uniform, and the optimal output performance is obtained by optimizing the inductance value; second, the capacitors are constrained, and through optimizing the inductance values under different capacitance arrangement, the optimal capacitance arrangement and the corresponding inductance value are worked out. The optimization results show that the quasi-square-wave pulse output can be obtained in both cases. A new method for design and engineering implementation of quasi-square-wave PFN can be provided. The theoretical calculation and circuit simulation results indicate that the proposed method is reasonable and practicable.
Pulse forming network (PFN) is often used in high-power solid-state modulator, microwave driver and laser exciter to obtain high voltage and long pulse output with wide flat-top. Aiming at the common used Rayleigh PFN with equal inductor and capacitor, according to the application requirement of wide flat-top and low ripple, the optimal design technology of PFN is studied, and the optimization algorithm based on simplex optimization method is proposed. The work is mainly carried out in two cases: first, the capacitance is uniform, and the optimal output performance is obtained by optimizing the inductance value; second, the capacitors are constrained, and through optimizing the inductance values under different capacitance arrangement, the optimal capacitance arrangement and the corresponding inductance value are worked out. The optimization results show that the quasi-square-wave pulse output can be obtained in both cases. A new method for design and engineering implementation of quasi-square-wave PFN can be provided. The theoretical calculation and circuit simulation results indicate that the proposed method is reasonable and practicable.
2020,
32: 065002.
doi: 10.11884/HPLPB202032.190464
Abstract:
Surface roughening treatment on insulators is an important way to improve their vacuum surface flashover characteristics. However, flashover voltages of the insulators with the same roughness show big deviation because of the poor uniformity of the surface rough structure and bad repeatability of the surface roughening method. To improve the uniformity of the surface roughening and the stability of the voltage-withstanding of the vacuum insulators, sand blasting roughening treatment on the surface of the cylindrical PMMA insulators was studied. First of all, the cylindrical insulators were sprayed on the rotating platform. With the collisions of the spherical micro SiO2 particles carried by the high-speed airflow, rough structure was fabricated on the surface. After the corrosion of the HF acid, residual SiO2 particles were removed, leaving homogeneous rough structure on the surface. The changes of the surface morphology were studied by Scanning Electron Microscope and the surface roughness of the treated insulators was tested on the surface roughness meter. Surface flashover characteristics of the sand-sprayed PMMA specimens were tested on the short-pulsed high-voltage platform. The test results indicated that homogeneously rough surface was prepared by the sand blasting treatment and the surface flashover voltages of the treated insulators were improved steadily. Compared with the untreated PMMA specimens, flashover voltages of the sand blasted insulators were improved approximately 80%.
Surface roughening treatment on insulators is an important way to improve their vacuum surface flashover characteristics. However, flashover voltages of the insulators with the same roughness show big deviation because of the poor uniformity of the surface rough structure and bad repeatability of the surface roughening method. To improve the uniformity of the surface roughening and the stability of the voltage-withstanding of the vacuum insulators, sand blasting roughening treatment on the surface of the cylindrical PMMA insulators was studied. First of all, the cylindrical insulators were sprayed on the rotating platform. With the collisions of the spherical micro SiO2 particles carried by the high-speed airflow, rough structure was fabricated on the surface. After the corrosion of the HF acid, residual SiO2 particles were removed, leaving homogeneous rough structure on the surface. The changes of the surface morphology were studied by Scanning Electron Microscope and the surface roughness of the treated insulators was tested on the surface roughness meter. Surface flashover characteristics of the sand-sprayed PMMA specimens were tested on the short-pulsed high-voltage platform. The test results indicated that homogeneously rough surface was prepared by the sand blasting treatment and the surface flashover voltages of the treated insulators were improved steadily. Compared with the untreated PMMA specimens, flashover voltages of the sand blasted insulators were improved approximately 80%.
2020,
32: 066001.
doi: 10.11884/HPLPB202032.190404
Abstract:
Aiming at the problems that may arise in the work of the AC-DC-AC converter of the new fast-control power system of the Experimental Advanced Superconducting Tokamak (EAST), a control and protection method for each link is proposed. Based on in-depth research on the protection mechanism of fast control power in the field of nuclear fusion, and combination with the needs of nuclear fusion devices, a surge current suppression circuit, a voltage protection circuit, an overcurrent protection circuit, an overt-emperature protection circuit, an energy leakage protection circuit, and a crowbar were designed. Compared with the traditional protection method, the scheme has a wide protection range, strong reliability and high security. The experimental results show that the power protection system can ensure safe and reliable exit of the power supply in the event of a sudden failure, and effectively protect the superconducting magnets and power components of the superconducting Tokamak experimental device from damage, verifying the correctness and effectiveness of the designed scheme.
Aiming at the problems that may arise in the work of the AC-DC-AC converter of the new fast-control power system of the Experimental Advanced Superconducting Tokamak (EAST), a control and protection method for each link is proposed. Based on in-depth research on the protection mechanism of fast control power in the field of nuclear fusion, and combination with the needs of nuclear fusion devices, a surge current suppression circuit, a voltage protection circuit, an overcurrent protection circuit, an overt-emperature protection circuit, an energy leakage protection circuit, and a crowbar were designed. Compared with the traditional protection method, the scheme has a wide protection range, strong reliability and high security. The experimental results show that the power protection system can ensure safe and reliable exit of the power supply in the event of a sudden failure, and effectively protect the superconducting magnets and power components of the superconducting Tokamak experimental device from damage, verifying the correctness and effectiveness of the designed scheme.
2020,
32: 069001.
doi: 10.11884/HPLPB202032.200145
Abstract:
The development of rapid detection technique with high sensitivity and high veracity for SARS-CoV-2 is of great importance for the prevention and control of epidemic. In this work, the trace spike protein (S protein) of SARS-CoV-2 in human saliva was detected by surface enhanced Raman spectroscopy (SERS) technique. Significant differences can be found between the Raman spectra of the S protein stained saliva sample and the primitive saliva sample. These results will lay the foundation for the future rapid detection of SARS-CoV-2 by SERS technique.
2020,
32: 063004.
doi: 10.11884/HPLPB202032.190373
Abstract:
This paper introduces a high-precision and continuously tunable medium bounded-wave electromagnetic pulse simulator, which adopts a widely tunable, automated novel high voltage pulse source of compact size with fast rise time. Based on fiber transmission automation control is realized, anti-jamming problem is solved and HEMP simulation ability is promoted. Parameters of the simulator are: the rise time about 2.5 ns, FWHM about 23 ns, working volume 4 m×4 m×5.8 m, output continuously tunable electric field from 0.2 kV/m to 60 kV/m.
