Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.     

电磁波在大气层人造等离子体中的衰减特性

利用洛沦兹模型来研究大气层人造非均匀等离子体的电磁响应特性,讨论了电磁波频率、等离子体密度及电子碰撞频率对电磁波衰减特性的影响.结果表明,电磁波在长波长区域及等离子体密度大时,其能量衰减越快.当等离子体密度高时,电子温度越低,大气层高度越高,电磁波的能量衰减越快. 关键词： 电磁波 大气等离子体 能量衰减     

柱等离子体中广义磁流体方程组的简化形式与本征模解

本文从含有广义欧姆定律的磁流体力学方程组出发,仅作符合加热托卡马克等离子体具体实验条件的近似,把广义磁流体方程组简化成4元一阶微分方程组。对均匀密度等离子体柱情况求出解析色散关系(本征模解),并证明Appert理论是本文的极限情况。 关键词：     

气体放电击穿过程的物理和数值研究

本文对低气压（１０＾－２Ｐａ）热阴极气体放电的击穿过程给出了物理描述和相应的双流体数学型，并发展了一种选择和调整未知初始条件的有效算法，可以通过伴随试射法得到对初始条件十分敏感的非线性两点边值常微分方程组的数值解，从而给出这类气体放电中击穿过程的定量描述。     

纳米TiO_2薄膜的低温等离子体制备技术

以四氯化钛为源物质,氩气为载气,氧气为反应气体,利用低温等离子体增强化学气相沉积在硅基表面制备出了TiO2薄膜。使用场发射扫描电子显微镜、X射线衍射仪等检测分析表征TiO2薄膜的性能与性质,并探讨了工艺条件如基片材料、沉积时间和基片温度对薄膜性能的影响。结果表明:制备的薄膜表面光滑均匀,结构致密,最小晶粒尺寸约15 nm;薄膜的晶型主要依赖于沉积温度,低于300℃沉积的薄膜是无定形的,300℃之上沉积的薄膜是锐钛矿结构。     

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J-TEXT装置由许多相关子系统组成,其中央控制系统的主要功能和作用是统一调度和协调各个子系统,控制装置的运行状态。J-TEXT中央控制系统是基于Windows和QNX操作系统平台,并采用工业控制计算机结合PCI工业控制卡来实现的。该系统已经完成了相关测试并获得满意结果。在首轮的J-TEXT放电调试中,该系统运行稳定可靠,控制效果良好。     

负偏压离子鞘及气体压强影响表面波放电过程的粒子模拟

由于表面电磁波沿着介质-等离子体分界面传播,而很难通过对传统的表面波等离子体(SWP)源施加负偏压实现金属材料溅射,因此限制了SWP源的使用范围.近期,一种基于负偏压离子鞘导波的SWP源克服了这个问题,且其加热机理是表面等离激元(SPP)的局域增强电场激励气体放电产生.但是该SWP源放电过程的影响因素并未研究清晰,导致其最佳放电条件没有获得.本文采用粒子(PIC)和蒙特卡罗碰撞(MCC)相结合的模拟方法,探讨了负偏压离子鞘及气体压强影响SWP电离发展过程的放电机理.模拟结果表明,负偏压和气体压强的大小影响了离子鞘的厚度、SPP的激励和波模的时空转化,从而表现出不同的放电形貌.进一步分析确定,在负偏压200 V左右和气体压强40 Pa附近,该SWP源的放电效果最佳.     

Estimation of Plasma Density by Surface Plasmons for Surface-Wave Plasmas

An estimation method of plasma density based on surface plasmons theory for surface-wave plasmas is proposed. The number of standing-wave is obtained directly from the discharge image, and the propagation constant is calculated with the trim size of the apparatus in this method, then plasma density can be determined with the value of 9.1 × 10^17m^-3. Plasma density is measured using a Langmuir probe, the value is 8.1 × 10^17m^-3 which is very close to the predicted value of surface plasmons theory. Numerical simulation is used to check the number of standing-wave by the finite-difference time-domain （FDTD） method also. All results are compatible both of theoretical analysis and experimental measurement.     

Multi-band microwave metamaterial absorber based on coplanar Jerusalem crossesMulti-band microwave metamaterial absorber based on coplanar Jerusalem crosses

The influence of the gap on the absorption performance of the conventional split ring resonator （SRR） absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross （JC） resonator and its corresponding metamaterial absorber （MA） is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.