We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface...We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface(t-CNT film).The tridimensional surface includes wet etched silicon pyramids,and the Ni layer is electroless plated thereon.The intense pulsed emission characteristics of the t-CNT and planar-grown CNT(p-CNT) films were measured using a diode structure in single-pulse mode.The even turn-on field decreased from 5.5 V/μm for p-CNTs to 2.8 V/m for t-CNTs,and the peak emission current increased from 232 A for p-CNTs to 324 A for t-CNTs at a peak field intensity ～12.2 V/m.The peak current of the t-CNT film increased by ～39.7% over the p-CNT film.It is clear that the micro-pyramid array can effectively suppress the field screening effect to improve the electron-emission of CNT films.展开更多
Carbon nanotube(CNT)films were grown on silicon wafers with and without a nickel layer(Si-CNT and Ni-CNT)via the pyrolysis of iron phthalocyanine.The nickel layer was prepared using the electroless plating method.To s...Carbon nanotube(CNT)films were grown on silicon wafers with and without a nickel layer(Si-CNT and Ni-CNT)via the pyrolysis of iron phthalocyanine.The nickel layer was prepared using the electroless plating method.To study the emission stability of Si-CNT and Ni-CNT cathodes during intense pulsed emission,emission characteristics were measured repeatedly with a diode structure using a Marx generator as a voltage source.For the peak values of the pulsed voltage,which were in the range between 1.62-1.66 MV(corresponding to electric field intensities between 11.57-11.85 V/μm),the first cycle emission current was 109.4 A for Si-CNT and 180.5 A for Ni-CNT.By comparing the normalized emission currents of the Si-CNT and Ni-CNT cathodes,the improvement in the emission stability can be easily quantified.The number of emission cycles necessary for the peak current to decay from 100%to 50%increased from^3 for Si-CNT to^11 for a Ni-CNT film.展开更多
A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement fact...A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement factor at the cathode surface for the diode with a curved surface cathode is also discussed. It is shown that compared with the current given by the conventional Child-Langmuir law, which describes the one-dimensional space-charege-limiting current, the two-dimensional space-charge-limiting current in such a diode is enhanced due to the electric-field enhancement along the cathode surface. Among practical parameter ranges, enhancement factor ηb approximately satisfies ηb Aβn, where β is the electric field enhancement factor at the cathode surface, and n is a constant between 1 and 2, which is confirmed to be universal for the diodes with curved surface cathodes.展开更多
The Free Electron Laser(FEL), for its ideal optical medium that is the flee electron which in vacuum has no bound energy level, has demonstrated its potential in tunable frequency and ultra-high power application fiel...The Free Electron Laser(FEL), for its ideal optical medium that is the flee electron which in vacuum has no bound energy level, has demonstrated its potential in tunable frequency and ultra-high power application fields.After basic mechanisms of FEL are verified, in research enthusiasm has naturally been transferred from theory to experiment, from proving to how to consummate the present展开更多
基金supported by the National Natural Science Foundation of China (51072184,50972132,51002143 and 60801022)the Aeronautical Science Foundation of China (2009ZE55003 and 2010ZF55013)the Basic and Advanced Technology Program of Henan (092300410139)
文摘We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface(t-CNT film).The tridimensional surface includes wet etched silicon pyramids,and the Ni layer is electroless plated thereon.The intense pulsed emission characteristics of the t-CNT and planar-grown CNT(p-CNT) films were measured using a diode structure in single-pulse mode.The even turn-on field decreased from 5.5 V/μm for p-CNTs to 2.8 V/m for t-CNTs,and the peak emission current increased from 232 A for p-CNTs to 324 A for t-CNTs at a peak field intensity ～12.2 V/m.The peak current of the t-CNT film increased by ～39.7% over the p-CNT film.It is clear that the micro-pyramid array can effectively suppress the field screening effect to improve the electron-emission of CNT films.
基金supported by the National Natural Science Foundation of China(51072184,50972132,51002143 and 60801022)the Aeronautical Science Foundation of China(2009ZE55003 and 2010ZF55013)the Basic and Advanced Technology Program of Henan(092300410139)
文摘Carbon nanotube(CNT)films were grown on silicon wafers with and without a nickel layer(Si-CNT and Ni-CNT)via the pyrolysis of iron phthalocyanine.The nickel layer was prepared using the electroless plating method.To study the emission stability of Si-CNT and Ni-CNT cathodes during intense pulsed emission,emission characteristics were measured repeatedly with a diode structure using a Marx generator as a voltage source.For the peak values of the pulsed voltage,which were in the range between 1.62-1.66 MV(corresponding to electric field intensities between 11.57-11.85 V/μm),the first cycle emission current was 109.4 A for Si-CNT and 180.5 A for Ni-CNT.By comparing the normalized emission currents of the Si-CNT and Ni-CNT cathodes,the improvement in the emission stability can be easily quantified.The number of emission cycles necessary for the peak current to decay from 100%to 50%increased from^3 for Si-CNT to^11 for a Ni-CNT film.
文摘A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement factor at the cathode surface for the diode with a curved surface cathode is also discussed. It is shown that compared with the current given by the conventional Child-Langmuir law, which describes the one-dimensional space-charege-limiting current, the two-dimensional space-charge-limiting current in such a diode is enhanced due to the electric-field enhancement along the cathode surface. Among practical parameter ranges, enhancement factor ηb approximately satisfies ηb Aβn, where β is the electric field enhancement factor at the cathode surface, and n is a constant between 1 and 2, which is confirmed to be universal for the diodes with curved surface cathodes.
文摘The Free Electron Laser(FEL), for its ideal optical medium that is the flee electron which in vacuum has no bound energy level, has demonstrated its potential in tunable frequency and ultra-high power application fields.After basic mechanisms of FEL are verified, in research enthusiasm has naturally been transferred from theory to experiment, from proving to how to consummate the present
