The cylindrical virtual cathode reflex triode is a new type of pulsed hard X-ray load,which has the advantages of simple structure,high radiation conversion efficiency,and simplicity in seriesparallel operation.This p...The cylindrical virtual cathode reflex triode is a new type of pulsed hard X-ray load,which has the advantages of simple structure,high radiation conversion efficiency,and simplicity in seriesparallel operation.This paper presents a method to reduce the impedance of the triode using a multiring cathode.The average electric field on the ring-cathode emission surface is enhanced due to edge effect,and the beam intensity is greatly increased in proportion to the square of the electric field strength.Multi-ring cathode is used to enlarge the emission area.Therefore,the reflex triode can work at lower impedance and generate a stronger beam under the same anode-cathode gap.In addition,the electric field enhancement of the cathode reduces the cathode emission stabilization time and enhances the operation stability of the triode.The effects of parameters such as ring width and ring gap on the triode impedance are simulated and studied.The cathode emission stabilization time and the X-ray conversion efficiency are compared.The design basis of cathode structure parameters and the impedance control method of the cylindrical virtual cathode reflex triode are given according to the simulations.展开更多
In this paper is determined the volume conductivity of thin polymeric films using the corona triode method, when the current through the sample exhibits a quadratic dependence on the grid potential. Based on the exper...In this paper is determined the volume conductivity of thin polymeric films using the corona triode method, when the current through the sample exhibits a quadratic dependence on the grid potential. Based on the experimental data, for the first time, an effective methodology for the determination of volume conductivity, graphically and analytically, is composed. The results obtained by the proposed analytical formula, for polypropylene and Trespaphan, with two different configurations of structures, are closely similar to the graphical method results. In addition, the satisfying accordance of our results, with the results, found out with the consulted literature, obtained by the “static” methods, confirms the accuracy of the proposed methodology, for the determination of volume conductivity of thin polymeric films, using the corona triode.展开更多
Field emission properties of carbon nanotube cold cathode （CNT-CC） of triode- and diode-structure have been investigated by using the finite element method of numerical simulation. Specially, the effects of gate vol...Field emission properties of carbon nanotube cold cathode （CNT-CC） of triode- and diode-structure have been investigated by using the finite element method of numerical simulation. Specially, the effects of gate voltage and hole radius R on the emission properties have been analyzed based on the finite element method. Results indicate that the gate can make the excitation electric field E increase, turn-on voltage decrease, and the emission current density J rise. The result shows that the E reaches its maximum value at the top of carbon nanotube （CNT）, and the optimum field emission performance can be obtained when R is equal to 10 times the diameter of the carbon nanotube.展开更多
基金supported by National Natural Science Foundation of China(Nos.12027811 and 12275222)。
文摘The cylindrical virtual cathode reflex triode is a new type of pulsed hard X-ray load,which has the advantages of simple structure,high radiation conversion efficiency,and simplicity in seriesparallel operation.This paper presents a method to reduce the impedance of the triode using a multiring cathode.The average electric field on the ring-cathode emission surface is enhanced due to edge effect,and the beam intensity is greatly increased in proportion to the square of the electric field strength.Multi-ring cathode is used to enlarge the emission area.Therefore,the reflex triode can work at lower impedance and generate a stronger beam under the same anode-cathode gap.In addition,the electric field enhancement of the cathode reduces the cathode emission stabilization time and enhances the operation stability of the triode.The effects of parameters such as ring width and ring gap on the triode impedance are simulated and studied.The cathode emission stabilization time and the X-ray conversion efficiency are compared.The design basis of cathode structure parameters and the impedance control method of the cylindrical virtual cathode reflex triode are given according to the simulations.
文摘In this paper is determined the volume conductivity of thin polymeric films using the corona triode method, when the current through the sample exhibits a quadratic dependence on the grid potential. Based on the experimental data, for the first time, an effective methodology for the determination of volume conductivity, graphically and analytically, is composed. The results obtained by the proposed analytical formula, for polypropylene and Trespaphan, with two different configurations of structures, are closely similar to the graphical method results. In addition, the satisfying accordance of our results, with the results, found out with the consulted literature, obtained by the “static” methods, confirms the accuracy of the proposed methodology, for the determination of volume conductivity of thin polymeric films, using the corona triode.
文摘Field emission properties of carbon nanotube cold cathode （CNT-CC） of triode- and diode-structure have been investigated by using the finite element method of numerical simulation. Specially, the effects of gate voltage and hole radius R on the emission properties have been analyzed based on the finite element method. Results indicate that the gate can make the excitation electric field E increase, turn-on voltage decrease, and the emission current density J rise. The result shows that the E reaches its maximum value at the top of carbon nanotube （CNT）, and the optimum field emission performance can be obtained when R is equal to 10 times the diameter of the carbon nanotube.
