In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds micro-Newtons.The thrust measurement system uses an el...In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds micro-Newtons.The thrust measurement system uses an elastic torsional pendulum structure with a capacitance sensor to measure the displacement,which can reflect the position change caused by the applied force perpendicular to the pendulum axis.In the open-loop mode,the steady-state thrust or the impulse of the plasma micro-thruster can be obtained from the swing of the pendulum,and in the closed-loop mode the steady-state thrust can be obtained from the feedback force that keeps the pendulum at a specific position.The thrust respond of the system was calibrated using an electrostatic weak force generation device.Experimental results show that the system can measure a thrust range from 0 to 200μN in both open-loop mode and closed-loop mode with a thrust resolution of 0.1μN,and the system can response to a pulse bit at the magnitude of 0.1 m N s generated by a micro cathode arc thruster.The background noise of the closed-loop mode is lower than that of the open-loop mode,both less than 0.1 m N/Hz in the range of 10 mHz to 5 Hz.展开更多
We present the axial profiles of argon helicon plasma measured by a local optical emission spectroscope(OES) and Langmuir RF-compensated probe. The results show that the emission intensity of the argon atom lines(750 ...We present the axial profiles of argon helicon plasma measured by a local optical emission spectroscope(OES) and Langmuir RF-compensated probe. The results show that the emission intensity of the argon atom lines(750 nm, 811 nm) is proportional to the plasma density determined by the Langmuir probe. The axial profile of helicon plasma depends on the discharge mode which changes with the RF power. Excited by helical antenna, the axial distribution of plasma density is similar to that of the external magnetic field in the capacitive coupled mode(E-mode). As the discharge mode changes into the inductively coupled mode(H-mode), the axial distribution of plasma density in the downstream can still be similar to that of the external magnetic field, but becomes more uniform in the upstream. When the discharge entered wave coupled mode(W-mode), the plasma becomes nearly uniform along the axis, showing a completely different profile from the magnetic field. The W-mode is expected to be a mixed pattern of helicon(H) and Trivelpiece-Gould(TG) waves.展开更多
In this work, a zero-dimensional plasma model for self-field magnetoplasmadynamic thrusters(SF-MPDTs) is proposed, which is based on the ion-number balance equation and energy balance equation, and can calculate the a...In this work, a zero-dimensional plasma model for self-field magnetoplasmadynamic thrusters(SF-MPDTs) is proposed, which is based on the ion-number balance equation and energy balance equation, and can calculate the average electron temperature and the average ion temperature inside the discharge chamber conveniently. At the same time, the model can also predict the thruster performance, and the thruster performance predicted by the model is compared with experimental results, which proved the reliability of the model.展开更多
The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas.Compared with electrostatic diagnostics,the optical method is independent of the radio frequenc...The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas.Compared with electrostatic diagnostics,the optical method is independent of the radio frequency(RF)noise,magnetic field,and electric field.In this paper,an optical emission spectroscope was used to determine the plasma emission spectra,electron excitation energy population distributions(EEEPDs),growth rates of low-energy and highenergy electrons,and their intensity jumps with input powers.The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD.One discrete EEEPD has two clear different regions,namely the low-energy electron excitation region(neutral lines with threshold energy of13–15 eV)and the high-energy electron excitation region(ionic lines with threshold energy?19 e V).The EEEPD variations with different diameters of discharge tubes(20 mm,40 mm,and 60 mm)and different input RF powers(200–1800 W)were investigated.By normalized intensity comparison of the ionic and neutral lines,the growth rate of the ionic population was higher than the neutral one,especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W.Moreover,we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled(H)mode to helicon(W)mode;therefore,the determination of W mode needs to be carefully considered.展开更多
Objective:To study the effect of nerve fragments and small gap suture of epineurium in peripheral nerve repair.Methods:(1)The experimental animals were randomly divided into control group,simple small gap suture group...Objective:To study the effect of nerve fragments and small gap suture of epineurium in peripheral nerve repair.Methods:(1)The experimental animals were randomly divided into control group,simple small gap suture group,small gap suture combined neural debris group;(2)observing the nerve anastomosis after two weeks;(3)testing nerve fiber regeneration after eight weeks;(4)testing gastrocnemius wet weight ratio after eight weeks;(5)pathological image analysis:the number of regenerated nerve fibers,the diameter and myelin thickness of regenerated nerve fiber were measured.Results:(1)Scar tissue was formed in traditional suture anastomotic adhesions;in simple small gap suture group,obvious adhesions was not found surrounding the tissue;for combination group of small gap suture with nerve debris,there was no obvious adhesions,and the outer membrane of small gap turned thinner than before.(2)Compared with the normal control group,the wet weight was increased significantly in the small gap suture group;relative to the small gap group,the wet weight was increased significantly in the small gap plus nerve fragments group.(3)Compared with the control group,the total number of myelinated nerve fibers was increased significantly in the small-gap suture group and small gap plusnerve fragments group;the diameter of nerve fibers and myelin thickness were increased significantly in simple small gap group and the small gap plus nerve debris group.(4)Histology showed:Compared with simple small gap suture group,nerve fiber density was increased,arrangement is neat in the small gap plus nerve fragments group.Conclusions:The nerve fragments plus epineurium small gap suture has a significant role in the repair of peripheral nerve injury.展开更多
Ion optics are crucial components of ion thrusters and the study of the different ion extraction solutions used since the beginning of the electric propulsion era is essential to understand the evolution of ion engine...Ion optics are crucial components of ion thrusters and the study of the different ion extraction solutions used since the beginning of the electric propulsion era is essential to understand the evolution of ion engines. This work describes ion engine grids＇ main functions, parameters and issues related to thermal expansion and sputter erosion, and then introduces a review of ion optics used for significant launched and tested ion thrusters since 1970. Configurations, geometries, materials and fabrication methods are analyzed to understand when typical ion thrusters use two or three grids, what are the thicknesses and aperture sizes of the screen, accelerator and decelerator grids, why molybdenum and carbon-based materials such as pyrolytic graphite and carbon–carbon are the best available options for ion optics and what is the manufacturing method for each material.展开更多
基金supported by the Shanghai Engineering Research Center of Space Engine(No.17DZ2280800)。
文摘In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds micro-Newtons.The thrust measurement system uses an elastic torsional pendulum structure with a capacitance sensor to measure the displacement,which can reflect the position change caused by the applied force perpendicular to the pendulum axis.In the open-loop mode,the steady-state thrust or the impulse of the plasma micro-thruster can be obtained from the swing of the pendulum,and in the closed-loop mode the steady-state thrust can be obtained from the feedback force that keeps the pendulum at a specific position.The thrust respond of the system was calibrated using an electrostatic weak force generation device.Experimental results show that the system can measure a thrust range from 0 to 200μN in both open-loop mode and closed-loop mode with a thrust resolution of 0.1μN,and the system can response to a pulse bit at the magnitude of 0.1 m N s generated by a micro cathode arc thruster.The background noise of the closed-loop mode is lower than that of the open-loop mode,both less than 0.1 m N/Hz in the range of 10 mHz to 5 Hz.
基金supported by National Natural Science Foundation of China (Nos. 11475131, 11805011)
文摘We present the axial profiles of argon helicon plasma measured by a local optical emission spectroscope(OES) and Langmuir RF-compensated probe. The results show that the emission intensity of the argon atom lines(750 nm, 811 nm) is proportional to the plasma density determined by the Langmuir probe. The axial profile of helicon plasma depends on the discharge mode which changes with the RF power. Excited by helical antenna, the axial distribution of plasma density is similar to that of the external magnetic field in the capacitive coupled mode(E-mode). As the discharge mode changes into the inductively coupled mode(H-mode), the axial distribution of plasma density in the downstream can still be similar to that of the external magnetic field, but becomes more uniform in the upstream. When the discharge entered wave coupled mode(W-mode), the plasma becomes nearly uniform along the axis, showing a completely different profile from the magnetic field. The W-mode is expected to be a mixed pattern of helicon(H) and Trivelpiece-Gould(TG) waves.
基金supported by National Natural Science Foundation of China (No. 11872093)。
文摘In this work, a zero-dimensional plasma model for self-field magnetoplasmadynamic thrusters(SF-MPDTs) is proposed, which is based on the ion-number balance equation and energy balance equation, and can calculate the average electron temperature and the average ion temperature inside the discharge chamber conveniently. At the same time, the model can also predict the thruster performance, and the thruster performance predicted by the model is compared with experimental results, which proved the reliability of the model.
基金supported by National Natural Science Foundation of China(Nos.11805011 and 11872093)supported by the Shanghai Engineering Research Center of Space Engine(No.17DZ2280800)
文摘The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas.Compared with electrostatic diagnostics,the optical method is independent of the radio frequency(RF)noise,magnetic field,and electric field.In this paper,an optical emission spectroscope was used to determine the plasma emission spectra,electron excitation energy population distributions(EEEPDs),growth rates of low-energy and highenergy electrons,and their intensity jumps with input powers.The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD.One discrete EEEPD has two clear different regions,namely the low-energy electron excitation region(neutral lines with threshold energy of13–15 eV)and the high-energy electron excitation region(ionic lines with threshold energy?19 e V).The EEEPD variations with different diameters of discharge tubes(20 mm,40 mm,and 60 mm)and different input RF powers(200–1800 W)were investigated.By normalized intensity comparison of the ionic and neutral lines,the growth rate of the ionic population was higher than the neutral one,especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W.Moreover,we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled(H)mode to helicon(W)mode;therefore,the determination of W mode needs to be carefully considered.
文摘Objective:To study the effect of nerve fragments and small gap suture of epineurium in peripheral nerve repair.Methods:(1)The experimental animals were randomly divided into control group,simple small gap suture group,small gap suture combined neural debris group;(2)observing the nerve anastomosis after two weeks;(3)testing nerve fiber regeneration after eight weeks;(4)testing gastrocnemius wet weight ratio after eight weeks;(5)pathological image analysis:the number of regenerated nerve fibers,the diameter and myelin thickness of regenerated nerve fiber were measured.Results:(1)Scar tissue was formed in traditional suture anastomotic adhesions;in simple small gap suture group,obvious adhesions was not found surrounding the tissue;for combination group of small gap suture with nerve debris,there was no obvious adhesions,and the outer membrane of small gap turned thinner than before.(2)Compared with the normal control group,the wet weight was increased significantly in the small gap suture group;relative to the small gap group,the wet weight was increased significantly in the small gap plus nerve fragments group.(3)Compared with the control group,the total number of myelinated nerve fibers was increased significantly in the small-gap suture group and small gap plusnerve fragments group;the diameter of nerve fibers and myelin thickness were increased significantly in simple small gap group and the small gap plus nerve debris group.(4)Histology showed:Compared with simple small gap suture group,nerve fiber density was increased,arrangement is neat in the small gap plus nerve fragments group.Conclusions:The nerve fragments plus epineurium small gap suture has a significant role in the repair of peripheral nerve injury.
文摘Ion optics are crucial components of ion thrusters and the study of the different ion extraction solutions used since the beginning of the electric propulsion era is essential to understand the evolution of ion engines. This work describes ion engine grids＇ main functions, parameters and issues related to thermal expansion and sputter erosion, and then introduces a review of ion optics used for significant launched and tested ion thrusters since 1970. Configurations, geometries, materials and fabrication methods are analyzed to understand when typical ion thrusters use two or three grids, what are the thicknesses and aperture sizes of the screen, accelerator and decelerator grids, why molybdenum and carbon-based materials such as pyrolytic graphite and carbon–carbon are the best available options for ion optics and what is the manufacturing method for each material.
