The beam tail effect of multi-bunches will influence the electron beam performance in a high intensity thermionic RF gun. Beam dynamic calculations that illustrate the working states of single beam tail and multi-puls...The beam tail effect of multi-bunches will influence the electron beam performance in a high intensity thermionic RF gun. Beam dynamic calculations that illustrate the working states of single beam tail and multi-pulse feed-in of a performance-enhanced EC-ITC （external cathode independent tunable cavity） RF gun for an FEL （free electron laser） injector are performed to estimate the extracted bunch properties. By using both Parmela and homemade MATLAB codes, the effects of a single beam tail as well as interactions of multi-pulses are analyzed, where a ring-based electron algorithm is adopted to calculated RF fields and the space-charge field. Furthermore, the procedure of unexpected deviated-energy particles mixed with an effective bunch head is described by the MATLAB code as well. As a result, the performance-enhanced EC-ITC RF gun is proved to have the capability to extract continual stable bunches suitable for a high requirement THz-FEL.展开更多
In this paper, a one-dimensional discharge model is employed to study multi-pulse phenomena in Ar dielectric barrier discharge （DBD） under atmospheric pressure. The finiteelement method is employed to solve the mode...In this paper, a one-dimensional discharge model is employed to study multi-pulse phenomena in Ar dielectric barrier discharge （DBD） under atmospheric pressure. The finiteelement method is employed to solve the model. The influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of multi discharge pulses are investigated and discussed. The simulation results show that, both the intensity of discharge current and the number of discharge pulses increase with the amplitude of applied voltage, and narrower gas gap is more favorable for the formation of multi pulses. It is revealed that Ar DBDs behave in glow discharge mode when the applied voltage and gas gap distance vary from 2 kV to 6 kV and from 1 mm to 3 mm, respectively. With the frequency decreasing from 250 Hz to 125 Hz, the intensity of discharge current weakens and the number of discharge pulses increases, and the discharges behave in the typical Townsend discharge mode.展开更多
In order to investigate the thermal shock and the heat conduction property of a target under multi-pulsed laser radiation, analytic expressions of both temperature and thermal stress fields in the target are deduced o...In order to investigate the thermal shock and the heat conduction property of a target under multi-pulsed laser radiation, analytic expressions of both temperature and thermal stress fields in the target are deduced on the basis of the non-Fourier conduction law and the thermo-elastic theory. Taking a stainless steel target as an example, we can solve the analytic expressions under appropriate boundary conditions by using the finite difference method and MATLAB software, and then reveal the evolution law of both surplus temperaturt, and thermal stress in the target. The results indicate that the temperature curves in the target irradiated by a multi-pulsed laser take on a delayed character in different sections away from the boundary, which is only affected by its relaxation time. The front of the stress wave is very steep in the non-Fourier numerical solutions, which presents an obvious thermal shock, so it is necessary to consider the non-Fourier effect of semi-infinite body under the high energy laser radiation.展开更多
The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The t...The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The tested cathodes include velvet,carbon fibers,carbon nano-tubes （CNTs） and dispenser cathodes.The results indicate that all four are able to emit multi-pulsed beams.For velvet,carbon fiber and CNTs,the electron induced cathode plasma emission may be the main process and this means that there are differences in beam parameters from pulse to pulse.For dispenser cathodes tested in the experiment,although there is a little difference from pulse to pulse for some reason,thermal-electric field emission may be the main process.展开更多
文摘The beam tail effect of multi-bunches will influence the electron beam performance in a high intensity thermionic RF gun. Beam dynamic calculations that illustrate the working states of single beam tail and multi-pulse feed-in of a performance-enhanced EC-ITC （external cathode independent tunable cavity） RF gun for an FEL （free electron laser） injector are performed to estimate the extracted bunch properties. By using both Parmela and homemade MATLAB codes, the effects of a single beam tail as well as interactions of multi-pulses are analyzed, where a ring-based electron algorithm is adopted to calculated RF fields and the space-charge field. Furthermore, the procedure of unexpected deviated-energy particles mixed with an effective bunch head is described by the MATLAB code as well. As a result, the performance-enhanced EC-ITC RF gun is proved to have the capability to extract continual stable bunches suitable for a high requirement THz-FEL.
基金supported in part by China Foundation for the Author of National Excellent Doctoral Dissertation(No.200338)Fundamental Research Funds for the Central Universities of China(No.xjj20100160)
文摘In this paper, a one-dimensional discharge model is employed to study multi-pulse phenomena in Ar dielectric barrier discharge （DBD） under atmospheric pressure. The finiteelement method is employed to solve the model. The influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of multi discharge pulses are investigated and discussed. The simulation results show that, both the intensity of discharge current and the number of discharge pulses increase with the amplitude of applied voltage, and narrower gas gap is more favorable for the formation of multi pulses. It is revealed that Ar DBDs behave in glow discharge mode when the applied voltage and gas gap distance vary from 2 kV to 6 kV and from 1 mm to 3 mm, respectively. With the frequency decreasing from 250 Hz to 125 Hz, the intensity of discharge current weakens and the number of discharge pulses increases, and the discharges behave in the typical Townsend discharge mode.
基金supported by the Chinese Natural Science Fund (No.10572020)
文摘In order to investigate the thermal shock and the heat conduction property of a target under multi-pulsed laser radiation, analytic expressions of both temperature and thermal stress fields in the target are deduced on the basis of the non-Fourier conduction law and the thermo-elastic theory. Taking a stainless steel target as an example, we can solve the analytic expressions under appropriate boundary conditions by using the finite difference method and MATLAB software, and then reveal the evolution law of both surplus temperaturt, and thermal stress in the target. The results indicate that the temperature curves in the target irradiated by a multi-pulsed laser take on a delayed character in different sections away from the boundary, which is only affected by its relaxation time. The front of the stress wave is very steep in the non-Fourier numerical solutions, which presents an obvious thermal shock, so it is necessary to consider the non-Fourier effect of semi-infinite body under the high energy laser radiation.
基金Supported by National Nature Science Foundation of China(10575090)State Key Laboratory of Advanced Materials (Beijing University of Science and Technology, 20082D-10)
文摘The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The tested cathodes include velvet,carbon fibers,carbon nano-tubes （CNTs） and dispenser cathodes.The results indicate that all four are able to emit multi-pulsed beams.For velvet,carbon fiber and CNTs,the electron induced cathode plasma emission may be the main process and this means that there are differences in beam parameters from pulse to pulse.For dispenser cathodes tested in the experiment,although there is a little difference from pulse to pulse for some reason,thermal-electric field emission may be the main process.
