Networks based on backscatter communication provide wireless data transmission in the absence of a power source.A backscatter device receives a radio frequency(RF)source and creates a backscattered signal that deliver...Networks based on backscatter communication provide wireless data transmission in the absence of a power source.A backscatter device receives a radio frequency(RF)source and creates a backscattered signal that delivers data;this enables new services in battery-less domains with massive Internet-of-Things(IoT)devices.Connectivity is highly energy-efficient in the context of massive IoT applications.Outdoors,long-range(LoRa)backscattering facilitates large IoT services.A backscatter network guarantees timeslot-and contention-based transmission.Timeslot-based transmission ensures data transmission,but is not scalable to different numbers of transmission devices.If contention-based transmission is used,collisions are unavoidable.To reduce collisions and increase transmission efficiency,the number of devices transmitting data must be controlled.To control device activation,the RF source range can be modulated by adjusting the RF source power during LoRa backscatter.This reduces the number of transmitting devices,and thus collisions and retransmission,thereby improving transmission efficiency.We performed extensive simulations to evaluate the performance of our method.展开更多
Combined with two-dimensional(2D)and three-dimensional(3D)finite element analysis and preliminary experimental tests,the effects of size and placement of the electromagnetic shield of the radio-frequency(RF)ion source...Combined with two-dimensional(2D)and three-dimensional(3D)finite element analysis and preliminary experimental tests,the effects of size and placement of the electromagnetic shield of the radio-frequency(RF)ion source with two drivers on plasma parameters and RF power transfer efficiency are analyzed.It is found that the same input direction of the current is better for the RF ion source with multiple drivers.The electromagnetic shield(EMS)should be placed symmetrically around the drivers,which is beneficial for the plasma to distribute uniformly and symmetrically in both drivers.Furthermore,the bigger the EMS shield radius is the better generating a higher electron density.These results will be of guiding significance to the design of electromagnetic shielding for RF ion sources with a multi-driver.展开更多
As the key ion source component of nuclear fusion auxiliary heating devices, the radio frequency (RF) ion source is developed and applied gradually to offer a source plasma with the advantages of ease of control and...As the key ion source component of nuclear fusion auxiliary heating devices, the radio frequency (RF) ion source is developed and applied gradually to offer a source plasma with the advantages of ease of control and high reliability. In addition, it easily achieves long-pulse steady-state operation. During the process of the development and testing of the RF ion source, a lot of original experimental data will be generated. Therefore, it is necessary to develop a stable and reliable computer data acquisition and processing application system for realizing the functions of data acquisition, storage, access, and real-time monitoring. In this paper, the development of a data acquisition and processing application system for the RF ion source is presented. The hardware platform is based on the PXI system and the software is programmed on the LabVIEW development environment. The key technologies that are used for the implementation of this software programming mainly include the long-pulse data acquisition technology, multi- threading processing technology, transmission control communication protocol, and the Lempel-Ziv-Oberhumer data compression algorithm. Now, this design has been tested and applied on the RF ion source. The test results show that it can work reliably and steadily. With the help of this design, the stable plasma discharge data of the RF ion source are collected, stored, accessed, and monitored in real-time. It is shown that it has a very practical application significance for the RF experiments.展开更多
This paper deals with the topic of RF plasma sources and their application inhigh-power neutral beam heating systems for nuclear fusion devices. RF sources represent aninteresting alternative to the conventional arc d...This paper deals with the topic of RF plasma sources and their application inhigh-power neutral beam heating systems for nuclear fusion devices. RF sources represent aninteresting alternative to the conventional arc discharge sources. Due to the absence of hotfilaments they exhibit an inherent simplicity both in mechanical and electrical aspects andconsequently offer advantages in terms of cost savings, gain in availability and reliability andreduced maintenance. This renders the RF plasma source attractive for any long pulse (> 10 sec) NBIsystem and in particular for the ITER NBI system. The latter, however, requires that the RF plasmasource is also capable of delivering negative rather than positive hydrogen ions. In the first partof the paper the types, characteristics and operation experience of RF plasma sources for positiveions in operation are described. The second part is devoted to the development for ITER NBI: thebasic requirements, physics and technology issues and the present status are discussed.展开更多
A 16 kV/20 A power supply was developed for the extraction grid of prototype radio frequency(RF) ion source of neutral beam injector. To acquire the state signals of extraction grid power supply(EGPS) and control ...A 16 kV/20 A power supply was developed for the extraction grid of prototype radio frequency(RF) ion source of neutral beam injector. To acquire the state signals of extraction grid power supply(EGPS) and control the operation of the EGPS, a data acquisition and control system has been developed. This system mainly consists of interlock protection circuit board, photoelectric conversion circuit, optical fibers, industrial compact peripheral component interconnect(CPCI) computer and host computer. The human machine interface of host computer delivers commands and data to program of the CPCI computer, as well as offers a convenient client for setting parameters and displaying EGPS status. The CPCI computer acquires the status of the power supply. The system can turn-off the EGPS quickly when the faults of EGPS occur. The system has been applied to the EGPS of prototype RF ion source. Test results show that the data acquisition and control system for the EGPS can meet the requirements of the operation of prototype RF ion source.展开更多
A radio frequency(RF)driven ion source is a very important component of a neutral beam injector for large magnetic confinement fusion devices.In order to study the key technology and physics of an RF driven ion source...A radio frequency(RF)driven ion source is a very important component of a neutral beam injector for large magnetic confinement fusion devices.In order to study the key technology and physics of an RF driven ion source for a neutral beam injector in China,an RF ion source test facility was developed at the Institute of Plasma Physics,Chinese Academy of Sciences.In this paper,a two-dimensional fluid model is used to simulate the fundamental physical characteristics of RF plasma discharge.Simulation results show the relationship of the characteristics of plasma(such as electron density and electron temperature)and RF power and gas pressure.In order to verify the effectiveness of the model,the characteristics of the plasma are investigated using a Langmuir probe.In this paper,experimental and simulation results are presented,and the possible reasons for the discrepancies between them are given.This paper can help us understand the characteristics of RF plasma discharge,and give a basis for further R&D for an RF ion source.展开更多
A new modified Angelov current–voltage characteristic model equation is proposed to improve the drain–source current(Ids) simulation of an Al Ga N/Ga N-based(gallium nitride) high electron mobility transistor(A...A new modified Angelov current–voltage characteristic model equation is proposed to improve the drain–source current(Ids) simulation of an Al Ga N/Ga N-based(gallium nitride) high electron mobility transistor(Al Ga N/Ga N-based HEMT) at high power operation. Since an accurate radio frequency(RF) current simulation is critical for a correct power simulation of the device, in this paper we propose a method of Al Ga N/Ga N high electron mobility transistor(HEMT)nonlinear large-signal model extraction with a supplemental modeling of RF drain–source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency(PAE) at class-AB quiescent bias of Vgs =-3.5 V, Vds= 30 V with a frequency of 9.6 GHz are presented.展开更多
A large-area high-power radio-frequency(RF) driven ion source was developed for positive and negative neutral beam injectors at the Korea Atomic Energy Research Institute(KAERI). The RF ion source consists of a dr...A large-area high-power radio-frequency(RF) driven ion source was developed for positive and negative neutral beam injectors at the Korea Atomic Energy Research Institute(KAERI). The RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of high-power RF discharge. Plasma ignition of the ion source is initiated by the injection of argongas without a starter-filament heating, and the argon-gas is then slowly exchanged by the injection of hydrogen-gas to produce pure hydrogen plasmas. The uniformities of the plasma parameter,such as a plasma density and an electron temperature, are measured at the lowest area of the driver region using two RF-compensated electrostatic probes along the direction of the shortand long-dimensions of the driver region. The plasma parameters will be compared with those obtained at the lowest area of the expansion bucket to analyze the plasma expansion properties from the driver region to the expansion region.展开更多
The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF) discharges is investigated by a two-dimensional(2D) particle-in-cell/Monte-Carlo collision(PIC/MCC) model. Results s...The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF) discharges is investigated by a two-dimensional(2D) particle-in-cell/Monte-Carlo collision(PIC/MCC) model. Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed, which is an essential condition for the plasma density enhancement outside hollow electrodes. In addition, the existence of the electron density peak at the orifice is generated via the hollow cathode effect(HCE), which plays an important role in the density enhancement. It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement, and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes.Higher electron density at the orifice, combined with larger radial plasma bulk width at the orifice,causes higher electron density outside hollow electrodes. The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes.展开更多
In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the be...In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.展开更多
Hα(Balmer-alpha), Hβ (Balmer-beta) and Hγ (Balmer-gamma) spectral line inten- sities in atomic hydrogen plasma are investigated by using a high-power RF source. The intensities of the Hα, Hβ and Hγ spectra...Hα(Balmer-alpha), Hβ (Balmer-beta) and Hγ (Balmer-gamma) spectral line inten- sities in atomic hydrogen plasma are investigated by using a high-power RF source. The intensities of the Hα, Hβ and Hγ spectral lines are detected by increasing the input power (0-6 kW) of ICPs (inductively coupled plasmas). With the increase of net input power, the intensity of Hα im- proves rapidly (0-2 kW), and then reaches its dynamic equilibrium; the intensities of Hβ can be divided into three processes: obvious increase (0-2 kW), rapid increase (2-4 kW), almost constant (4-6 kW); while the intensities of Hγ increase very slowly. The energy levels of the excited hydro- gen atoms and the splitting energy levels produced by an obvious Stark effect play an important role in the results.展开更多
3 sets of 500 MHz 300kW RF amplifiers to be used at the main ring of the Shanghai Synchrotron Radiation Facility (SSRF) have been installed on site.The Site Acceptance Test (SAT) of the first RF power source was compl...3 sets of 500 MHz 300kW RF amplifiers to be used at the main ring of the Shanghai Synchrotron Radiation Facility (SSRF) have been installed on site.The Site Acceptance Test (SAT) of the first RF power source was completed in last March.The second and third RF power sources are going well and will be finished in October.The type choice, the layout of the RF power sources and the comparison between the SAT conclusion and the design goals are presented.展开更多
Inductively coupled radio-frequency(RF) plasma neutralizer(RPN) is an insert-free device that can be employed as an electron source in electric propulsion applications.Electron-extraction characteristics of the RP...Inductively coupled radio-frequency(RF) plasma neutralizer(RPN) is an insert-free device that can be employed as an electron source in electric propulsion applications.Electron-extraction characteristics of the RPN are related to the bulk plasma parameters and the device's geometry.Therefore,the effects of different electron-extraction apertures and operational parameters upon the electron-extraction characteristics are investigated according to the global nonambipolar flow and sheath model.Moreover,these models can also be used to explain why the electron-extraction characteristics of the RPN strongly depend upon the formation of the anode spot.During the experimental study,two types of anode spots are observed.Each of them has unique characteristics of electron extraction.Moreover,the hysteresis of an anode spot is observed by changing the xenon volume-flow rates or the bias voltages.In addition,the rapid ignited method,gas-utilization factor,electron-extraction cost and other factors that need to be considered in the design of the RPN are also discussed.展开更多
Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,fo...Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission line.Correspondingly,eight online RF power sources are used to power these accelerators.In order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control system.Methods The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so on.The DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so on.Result During beam commissioning,all of eight online units of LLRF control system were operating stably and reliably.The amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in phase.Conclusion With the help of this system,we achieved stable operation under different beam loads.Also,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability performance.This article describes the design and implementation of the LLRF for CSNS linac.展开更多
基金the National Research Foundation of Korea(NRF)grant funded by theKoreaGovernment(MSIT)(No.2021R1C1C1013133)Basic ScienceResearch Programthrough the NationalResearch Foundation ofKorea(NRF)funded by the Ministry of Education(NRF-2020R1I1A3066543)the Soonchunhyang University Research Fund.
文摘Networks based on backscatter communication provide wireless data transmission in the absence of a power source.A backscatter device receives a radio frequency(RF)source and creates a backscattered signal that delivers data;this enables new services in battery-less domains with massive Internet-of-Things(IoT)devices.Connectivity is highly energy-efficient in the context of massive IoT applications.Outdoors,long-range(LoRa)backscattering facilitates large IoT services.A backscatter network guarantees timeslot-and contention-based transmission.Timeslot-based transmission ensures data transmission,but is not scalable to different numbers of transmission devices.If contention-based transmission is used,collisions are unavoidable.To reduce collisions and increase transmission efficiency,the number of devices transmitting data must be controlled.To control device activation,the RF source range can be modulated by adjusting the RF source power during LoRa backscatter.This reduces the number of transmitting devices,and thus collisions and retransmission,thereby improving transmission efficiency.We performed extensive simulations to evaluate the performance of our method.
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)National Natural Science Foundation of China(No.11975263)the National Key R&D Program of China(No.2017YFE0300101)。
文摘Combined with two-dimensional(2D)and three-dimensional(3D)finite element analysis and preliminary experimental tests,the effects of size and placement of the electromagnetic shield of the radio-frequency(RF)ion source with two drivers on plasma parameters and RF power transfer efficiency are analyzed.It is found that the same input direction of the current is better for the RF ion source with multiple drivers.The electromagnetic shield(EMS)should be placed symmetrically around the drivers,which is beneficial for the plasma to distribute uniformly and symmetrically in both drivers.Furthermore,the bigger the EMS shield radius is the better generating a higher electron density.These results will be of guiding significance to the design of electromagnetic shielding for RF ion sources with a multi-driver.
基金the NBI team and the partial support of National Natural Science Foundation of China (No. 61363019)National Natural Science Foundation of Qinghai Province (No. 2014-ZJ-718)
文摘As the key ion source component of nuclear fusion auxiliary heating devices, the radio frequency (RF) ion source is developed and applied gradually to offer a source plasma with the advantages of ease of control and high reliability. In addition, it easily achieves long-pulse steady-state operation. During the process of the development and testing of the RF ion source, a lot of original experimental data will be generated. Therefore, it is necessary to develop a stable and reliable computer data acquisition and processing application system for realizing the functions of data acquisition, storage, access, and real-time monitoring. In this paper, the development of a data acquisition and processing application system for the RF ion source is presented. The hardware platform is based on the PXI system and the software is programmed on the LabVIEW development environment. The key technologies that are used for the implementation of this software programming mainly include the long-pulse data acquisition technology, multi- threading processing technology, transmission control communication protocol, and the Lempel-Ziv-Oberhumer data compression algorithm. Now, this design has been tested and applied on the RF ion source. The test results show that it can work reliably and steadily. With the help of this design, the stable plasma discharge data of the RF ion source are collected, stored, accessed, and monitored in real-time. It is shown that it has a very practical application significance for the RF experiments.
文摘This paper deals with the topic of RF plasma sources and their application inhigh-power neutral beam heating systems for nuclear fusion devices. RF sources represent aninteresting alternative to the conventional arc discharge sources. Due to the absence of hotfilaments they exhibit an inherent simplicity both in mechanical and electrical aspects andconsequently offer advantages in terms of cost savings, gain in availability and reliability andreduced maintenance. This renders the RF plasma source attractive for any long pulse (> 10 sec) NBIsystem and in particular for the ITER NBI system. The latter, however, requires that the RF plasmasource is also capable of delivering negative rather than positive hydrogen ions. In the first partof the paper the types, characteristics and operation experience of RF plasma sources for positiveions in operation are described. The second part is devoted to the development for ITER NBI: thebasic requirements, physics and technology issues and the present status are discussed.
基金supported by National Natural Science Foundation of China(Contract Nos.11505225&11675216)Foundation of ASIPP(Contract No.DSJJ-15-GC03)the Key Program of Research and Development of Hefei Science Center,CAS(2016HSC-KPRD002)
文摘A 16 kV/20 A power supply was developed for the extraction grid of prototype radio frequency(RF) ion source of neutral beam injector. To acquire the state signals of extraction grid power supply(EGPS) and control the operation of the EGPS, a data acquisition and control system has been developed. This system mainly consists of interlock protection circuit board, photoelectric conversion circuit, optical fibers, industrial compact peripheral component interconnect(CPCI) computer and host computer. The human machine interface of host computer delivers commands and data to program of the CPCI computer, as well as offers a convenient client for setting parameters and displaying EGPS status. The CPCI computer acquires the status of the power supply. The system can turn-off the EGPS quickly when the faults of EGPS occur. The system has been applied to the EGPS of prototype RF ion source. Test results show that the data acquisition and control system for the EGPS can meet the requirements of the operation of prototype RF ion source.
基金National Natural Science Foundation of China(Nos.11675216,11905248,11975261,11975262,11975263,and 11975264)the Key Program of Research and Development of Hefei Science Center,CAS(Contract No.2016HSC-KPRD002)the National Key R&D Program of China(Nos.2017YFE0300101,2017YFE0300103,and 2017YFE0300503).
文摘A radio frequency(RF)driven ion source is a very important component of a neutral beam injector for large magnetic confinement fusion devices.In order to study the key technology and physics of an RF driven ion source for a neutral beam injector in China,an RF ion source test facility was developed at the Institute of Plasma Physics,Chinese Academy of Sciences.In this paper,a two-dimensional fluid model is used to simulate the fundamental physical characteristics of RF plasma discharge.Simulation results show the relationship of the characteristics of plasma(such as electron density and electron temperature)and RF power and gas pressure.In order to verify the effectiveness of the model,the characteristics of the plasma are investigated using a Langmuir probe.In this paper,experimental and simulation results are presented,and the possible reasons for the discrepancies between them are given.This paper can help us understand the characteristics of RF plasma discharge,and give a basis for further R&D for an RF ion source.
基金Project supported by the National Natural Science Foundation of China(Grant No.61204086)
文摘A new modified Angelov current–voltage characteristic model equation is proposed to improve the drain–source current(Ids) simulation of an Al Ga N/Ga N-based(gallium nitride) high electron mobility transistor(Al Ga N/Ga N-based HEMT) at high power operation. Since an accurate radio frequency(RF) current simulation is critical for a correct power simulation of the device, in this paper we propose a method of Al Ga N/Ga N high electron mobility transistor(HEMT)nonlinear large-signal model extraction with a supplemental modeling of RF drain–source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency(PAE) at class-AB quiescent bias of Vgs =-3.5 V, Vds= 30 V with a frequency of 9.6 GHz are presented.
基金supported by the Ministry of Science,ICT and Future Planning of the Republic of Korea under the ITER Technology R&D ProgramNational R&D Program Through the National Research Foundation of Korea(NRF)Funded by the Ministry of Science,ICT&Future Planning(NRF-2014M1A7A1A03045372)
文摘A large-area high-power radio-frequency(RF) driven ion source was developed for positive and negative neutral beam injectors at the Korea Atomic Energy Research Institute(KAERI). The RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of high-power RF discharge. Plasma ignition of the ion source is initiated by the injection of argongas without a starter-filament heating, and the argon-gas is then slowly exchanged by the injection of hydrogen-gas to produce pure hydrogen plasmas. The uniformities of the plasma parameter,such as a plasma density and an electron temperature, are measured at the lowest area of the driver region using two RF-compensated electrostatic probes along the direction of the shortand long-dimensions of the driver region. The plasma parameters will be compared with those obtained at the lowest area of the expansion bucket to analyze the plasma expansion properties from the driver region to the expansion region.
文摘The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF) discharges is investigated by a two-dimensional(2D) particle-in-cell/Monte-Carlo collision(PIC/MCC) model. Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed, which is an essential condition for the plasma density enhancement outside hollow electrodes. In addition, the existence of the electron density peak at the orifice is generated via the hollow cathode effect(HCE), which plays an important role in the density enhancement. It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement, and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes.Higher electron density at the orifice, combined with larger radial plasma bulk width at the orifice,causes higher electron density outside hollow electrodes. The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes.
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)
文摘In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2011GB108011 and 2010GB103001)the Major International(Regional) Project Cooperation and Exchanges(No.11320101005)
文摘Hα(Balmer-alpha), Hβ (Balmer-beta) and Hγ (Balmer-gamma) spectral line inten- sities in atomic hydrogen plasma are investigated by using a high-power RF source. The intensities of the Hα, Hβ and Hγ spectral lines are detected by increasing the input power (0-6 kW) of ICPs (inductively coupled plasmas). With the increase of net input power, the intensity of Hα im- proves rapidly (0-2 kW), and then reaches its dynamic equilibrium; the intensities of Hβ can be divided into three processes: obvious increase (0-2 kW), rapid increase (2-4 kW), almost constant (4-6 kW); while the intensities of Hγ increase very slowly. The energy levels of the excited hydro- gen atoms and the splitting energy levels produced by an obvious Stark effect play an important role in the results.
文摘3 sets of 500 MHz 300kW RF amplifiers to be used at the main ring of the Shanghai Synchrotron Radiation Facility (SSRF) have been installed on site.The Site Acceptance Test (SAT) of the first RF power source was completed in last March.The second and third RF power sources are going well and will be finished in October.The type choice, the layout of the RF power sources and the comparison between the SAT conclusion and the design goals are presented.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23030100)
文摘Inductively coupled radio-frequency(RF) plasma neutralizer(RPN) is an insert-free device that can be employed as an electron source in electric propulsion applications.Electron-extraction characteristics of the RPN are related to the bulk plasma parameters and the device's geometry.Therefore,the effects of different electron-extraction apertures and operational parameters upon the electron-extraction characteristics are investigated according to the global nonambipolar flow and sheath model.Moreover,these models can also be used to explain why the electron-extraction characteristics of the RPN strongly depend upon the formation of the anode spot.During the experimental study,two types of anode spots are observed.Each of them has unique characteristics of electron extraction.Moreover,the hysteresis of an anode spot is observed by changing the xenon volume-flow rates or the bias voltages.In addition,the rapid ignited method,gas-utilization factor,electron-extraction cost and other factors that need to be considered in the design of the RPN are also discussed.
基金The authors would like to sincerely thank the CSNS linac RF team for their hard work and dedication.This work was supported by the China Spallation Neutron Source project.
文摘Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission line.Correspondingly,eight online RF power sources are used to power these accelerators.In order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control system.Methods The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so on.The DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so on.Result During beam commissioning,all of eight online units of LLRF control system were operating stably and reliably.The amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in phase.Conclusion With the help of this system,we achieved stable operation under different beam loads.Also,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability performance.This article describes the design and implementation of the LLRF for CSNS linac.