A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in fr...A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However, the magnetic field diffused into the driver has some influence on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver, a circular ring(absorber) of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around it and improve plasma outflowing. With the application of the absorber, the electron density is increased by about 35%, and the extraction current measured from the extraction grid is increased from 1.02 A to 1.29 A. The results of the extraction experiment with cesium injection show that both the extraction grid(EG) current and H-current are increased when the absorber is introduced.展开更多
This paper deals with wave propagation and power coupling in blue-core helicon plasma driven by various antennas and frequencies.It is found that compared to non-blue-core mode,for blue-core mode,the wave can propagat...This paper deals with wave propagation and power coupling in blue-core helicon plasma driven by various antennas and frequencies.It is found that compared to non-blue-core mode,for blue-core mode,the wave can propagate in the core region,and it decays sharply outside the core.The power absorption is lower and steeper in radius for blue-core mode.Regarding the effects of antenna geometry for blue-core mode,it shows that half helix antenna yields the strongest wave field and power absorption,while loop antenna yields the lowest.Moreover,near axis,for antennas with m=+1,the wave field increases with axial distance.In the core region,the wave number approaches to a saturation value at much lower frequency for non-blue-core mode compared to blue-core mode.The total loading resistance is much lower for blue-core mode.These findings are valuable to understanding the physics of blue-core helicon discharge and optimizing the experimental performance of blue-core helicon plasma sources for applications such as space propulsion and material treatment.展开更多
To ensure project safety and secure public support, an integrated and comprehensive monitoring program is needed within a carbon capture and storage(CCS) project. Monitoring can be done using many well-established tec...To ensure project safety and secure public support, an integrated and comprehensive monitoring program is needed within a carbon capture and storage(CCS) project. Monitoring can be done using many well-established techniques from various fields, and the seismic method proves to be the crucial one. This method is widely used to determine the CO_(2) distribution, image the plume development, and quantitatively estimate the concentration. Because both the CO_(2) distribution and the potential migration pathway can be spatially small scale, high resolution for seismic imaging is demanded. However, obtaining a high-resolution image of a subsurface structure in marine settings is difficult. Herein, we introduce the novel Hcable(Harrow-like cable system) technique, which may be applied to offshore CCS monitoring. This technique uses a highfrequency source(the dominant frequency>100 Hz) to generate seismic waves and a combination of a long cable and several short streamers to receive seismic waves. Ultrahigh-frequency seismic images are achieved through the processing of Hcable seismic data. Hcable is then applied in a case study to demonstrate its detailed characterization for small-scale structures. This work reveals that Hcable is a promising tool for timelapse seismic monitoring of oceanic CCS.展开更多
Integrated geophysical technology is a necessary and effective means for geothermal exploration.However,integration of geophysical technology for large‐scale surveys with those for geothermal reservoir localization i...Integrated geophysical technology is a necessary and effective means for geothermal exploration.However,integration of geophysical technology for large‐scale surveys with those for geothermal reservoir localization is still in development.This study used the controlled source audio‐frequency magnetotelluric method technology for large‐scale exploration to obtain underground electrical structure information and micromotion detection technology to obtain underground wave velocity structure information.The combination of two detection technologies was used for local identification of geothermal reservoirs.Further,auxiliary correction and inversion constraint were implemented through the audio magnetotelluric sounding technology for maximum authenticity restoration of the near‐and transition‐field data.Through these technology improvements,a geothermal geological model was established for the Binhai County of Jiangsu Province in China and potential geothermal well locations were identified.On this basis,a geothermal well was drilled nearly 3000m deep,with a daily water volume of over 2000m3/day and a geothermal water temperature of 51°C at the well head.It is found that predictions using the above integrated geophysical exploration technology are in good agreement with the well geological formation data.This integrated geophysical technology can be effectively applied for geothermal exploration with high precision and reliability.展开更多
Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbo...Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbon(Si-DLC)produced by a magnetic field enhanced radio frequency ion source,which is established to get high density plasma with the help of magnetic field.Under proper deposition process,a contact angle of 111°hydrophobic surface was achieved without any surface patterning,where nanostructure SiC grains appeared within the amorphous microstructure.The surface property was influenced by ion flow parameters as well as the resultant surface microstructure.The magnetic field enhanced radio frequency ion source developed in this paper was useful for protective film applications.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
Using very recently published X-ray and low frequency radio data we have calculated thelower limit of the magnetic field and several other related quantities for 25 clusters of galaxies（which are classified into '...Using very recently published X-ray and low frequency radio data we have calculated thelower limit of the magnetic field and several other related quantities for 25 clusters of galaxies（which are classified into 'normal', distant and steep spectrum clusters） and 12 radiogalaxies. Our main results are as follows: （1）The magnetic field in the extended lobes of radio galaxies is larger than 10-6 G.Thus radio galaxies, whether they belong to clusters or not, emit few X-rays through theinverse Compton effect. （2）The low frequency radio emission from clusters can be divided into two components:one or several radio galaxies, and an extended halo where the magnetic field is about 10-8G, and where inverse Compton X-rays are most probably emitted. （3）Our sample of distant clusters is biased towards high radio luminosity and givesresults comparable to those obtained for radio galaxies. This can naturally be explained bythe fact that the radio galaxy component daminates the radio emission. （4）In steep spectrum clusters, the equipartition magnetic field is the same as that in'normal' clusters, but the lower limit of the magnetic field has a rather high value andseems to increase with the spectral indcx. We explain this as follows: a high frequencyturnover can occur hi the weak intraculuster magnetic field; the extrapolation of the power lawelectron spectrum is then incorrect, and the magnetic field; the extrapolation of the power lawvalue.展开更多
We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppre...We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.展开更多
Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reas...Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reason for output spectrum instability when no polarization controller （PC） is present in the loop is analyzed theoretically. Numerical simulations for the output spectra of the multi-carrier source with and without PC are conducted, and the trajectories of the several frequency components polarization states on the Poincare sphere with and without PC are compared. The results show that the performance of multi-carrier source based on a RFS can be improved effectively by adjusting the PC in the configuration properly.展开更多
A closed-form approximate maximum likelihood（AML） algorithm for estimating the position and velocity of a moving source is proposed by utilizing the time difference of arrival（TDOA） and frequency difference of arr...A closed-form approximate maximum likelihood（AML） algorithm for estimating the position and velocity of a moving source is proposed by utilizing the time difference of arrival（TDOA） and frequency difference of arrival（FDOA） measurements of a signal received at a number of receivers.The maximum likelihood（ML） technique is a powerful tool to solve this problem.But a direct approach that uses the ML estimator to solve the localization problem is exhaustive search in the solution space,and it is very computationally expensive,and prohibits real-time processing.On the basis of ML function,a closed-form approximate solution to the ML equations can be obtained,which can allow real-time implementation as well as global convergence.Simulation results show that the proposed estimator achieves better performance than the two-step weighted least squares（WLS） approach,which makes it possible to attain the Cramér-Rao lower bound（CRLB） at a sufficiently high noise level before the threshold effect occurs.展开更多
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.11975264)。
文摘A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However, the magnetic field diffused into the driver has some influence on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver, a circular ring(absorber) of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around it and improve plasma outflowing. With the application of the absorber, the electron density is increased by about 35%, and the extraction current measured from the extraction grid is increased from 1.02 A to 1.29 A. The results of the extraction experiment with cesium injection show that both the extraction grid(EG) current and H-current are increased when the absorber is introduced.
基金Project supported by the National Natural Science Foundation of China(Grant No.92271113)the Fundamental Research Funds for the Central Universities(Grant No.2022CDJQY-003)+1 种基金Chongqing Entrepreneurship and Innovation Support Program for Overseas Returnees(Grant No.CX2022004)the Fund from Shanghai Engineering Research Center of Space Engine(Grant No.17DZ2280800).
文摘This paper deals with wave propagation and power coupling in blue-core helicon plasma driven by various antennas and frequencies.It is found that compared to non-blue-core mode,for blue-core mode,the wave can propagate in the core region,and it decays sharply outside the core.The power absorption is lower and steeper in radius for blue-core mode.Regarding the effects of antenna geometry for blue-core mode,it shows that half helix antenna yields the strongest wave field and power absorption,while loop antenna yields the lowest.Moreover,near axis,for antennas with m=+1,the wave field increases with axial distance.In the core region,the wave number approaches to a saturation value at much lower frequency for non-blue-core mode compared to blue-core mode.The total loading resistance is much lower for blue-core mode.These findings are valuable to understanding the physics of blue-core helicon discharge and optimizing the experimental performance of blue-core helicon plasma sources for applications such as space propulsion and material treatment.
基金Supported by the project of Sanya Yazhou Bay Science and Technology City (Grant No:SCKJ-JYRC-2022-14)。
文摘To ensure project safety and secure public support, an integrated and comprehensive monitoring program is needed within a carbon capture and storage(CCS) project. Monitoring can be done using many well-established techniques from various fields, and the seismic method proves to be the crucial one. This method is widely used to determine the CO_(2) distribution, image the plume development, and quantitatively estimate the concentration. Because both the CO_(2) distribution and the potential migration pathway can be spatially small scale, high resolution for seismic imaging is demanded. However, obtaining a high-resolution image of a subsurface structure in marine settings is difficult. Herein, we introduce the novel Hcable(Harrow-like cable system) technique, which may be applied to offshore CCS monitoring. This technique uses a highfrequency source(the dominant frequency>100 Hz) to generate seismic waves and a combination of a long cable and several short streamers to receive seismic waves. Ultrahigh-frequency seismic images are achieved through the processing of Hcable seismic data. Hcable is then applied in a case study to demonstrate its detailed characterization for small-scale structures. This work reveals that Hcable is a promising tool for timelapse seismic monitoring of oceanic CCS.
基金Geological and Mineral Resources Survey of Metallogenic Belt in the Middle and Lower Reaches of Yangtze River,Grant/Award Number:1212011220540Jiangsu 1:50000 Dingsanwei,Kaishan Island,Yangqiao,Chenjiagang,New Huaihe Estuary,Xiangshui Estuary,Dayou,Xiaojie,DayuJian District,Grant/Award Numbers:Base[2012]02‐014‐009,Base[2013]01‐019‐002,Base[2014]01‐021‐003。
文摘Integrated geophysical technology is a necessary and effective means for geothermal exploration.However,integration of geophysical technology for large‐scale surveys with those for geothermal reservoir localization is still in development.This study used the controlled source audio‐frequency magnetotelluric method technology for large‐scale exploration to obtain underground electrical structure information and micromotion detection technology to obtain underground wave velocity structure information.The combination of two detection technologies was used for local identification of geothermal reservoirs.Further,auxiliary correction and inversion constraint were implemented through the audio magnetotelluric sounding technology for maximum authenticity restoration of the near‐and transition‐field data.Through these technology improvements,a geothermal geological model was established for the Binhai County of Jiangsu Province in China and potential geothermal well locations were identified.On this basis,a geothermal well was drilled nearly 3000m deep,with a daily water volume of over 2000m3/day and a geothermal water temperature of 51°C at the well head.It is found that predictions using the above integrated geophysical exploration technology are in good agreement with the well geological formation data.This integrated geophysical technology can be effectively applied for geothermal exploration with high precision and reliability.
文摘Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbon(Si-DLC)produced by a magnetic field enhanced radio frequency ion source,which is established to get high density plasma with the help of magnetic field.Under proper deposition process,a contact angle of 111°hydrophobic surface was achieved without any surface patterning,where nanostructure SiC grains appeared within the amorphous microstructure.The surface property was influenced by ion flow parameters as well as the resultant surface microstructure.The magnetic field enhanced radio frequency ion source developed in this paper was useful for protective film applications.
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Using very recently published X-ray and low frequency radio data we have calculated thelower limit of the magnetic field and several other related quantities for 25 clusters of galaxies（which are classified into 'normal', distant and steep spectrum clusters） and 12 radiogalaxies. Our main results are as follows: （1）The magnetic field in the extended lobes of radio galaxies is larger than 10-6 G.Thus radio galaxies, whether they belong to clusters or not, emit few X-rays through theinverse Compton effect. （2）The low frequency radio emission from clusters can be divided into two components:one or several radio galaxies, and an extended halo where the magnetic field is about 10-8G, and where inverse Compton X-rays are most probably emitted. （3）Our sample of distant clusters is biased towards high radio luminosity and givesresults comparable to those obtained for radio galaxies. This can naturally be explained bythe fact that the radio galaxy component daminates the radio emission. （4）In steep spectrum clusters, the equipartition magnetic field is the same as that in'normal' clusters, but the lower limit of the magnetic field has a rather high value andseems to increase with the spectral indcx. We explain this as follows: a high frequencyturnover can occur hi the weak intraculuster magnetic field; the extrapolation of the power lawelectron spectrum is then incorrect, and the magnetic field; the extrapolation of the power lawvalue.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61627817 and 61535006)
文摘We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.
基金supported by the Chinese Universities Scientific Fund (No. BUPT 2011RC009)the BUPT Excellent Ph.D. Students Foundation (No. CX201121)the Research Fund for the Doctoral Program of Higher Education (No. 20110005110014)
文摘Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reason for output spectrum instability when no polarization controller （PC） is present in the loop is analyzed theoretically. Numerical simulations for the output spectra of the multi-carrier source with and without PC are conducted, and the trajectories of the several frequency components polarization states on the Poincare sphere with and without PC are compared. The results show that the performance of multi-carrier source based on a RFS can be improved effectively by adjusting the PC in the configuration properly.
基金National High-tech Research and Development Program of China (2010AA7010422,2011AA7014061)
文摘A closed-form approximate maximum likelihood（AML） algorithm for estimating the position and velocity of a moving source is proposed by utilizing the time difference of arrival（TDOA） and frequency difference of arrival（FDOA） measurements of a signal received at a number of receivers.The maximum likelihood（ML） technique is a powerful tool to solve this problem.But a direct approach that uses the ML estimator to solve the localization problem is exhaustive search in the solution space,and it is very computationally expensive,and prohibits real-time processing.On the basis of ML function,a closed-form approximate solution to the ML equations can be obtained,which can allow real-time implementation as well as global convergence.Simulation results show that the proposed estimator achieves better performance than the two-step weighted least squares（WLS） approach,which makes it possible to attain the Cramér-Rao lower bound（CRLB） at a sufficiently high noise level before the threshold effect occurs.
