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1.
Comparative investigation of the resistance and ability to trigger high voltage discharge for single and multiple femtosecond filaments in air 下载免费PDF全文
A comparative investigation of the resistance and ability to trigger high voltage(HV) discharge for a single filament(SF) and multiple filaments(MFs) has been carried out.The experimental results show that the trend of the breakdown threshold of the SF exactly follows that of its resistance,but this is not the case for the MF.The MF’s resistance is much smaller than the SF’s.However,the MF shows a slightly higher HV breakdown threshold than the SF.The underlying physics is that the measured resistance of the MF is collectively contributed by every filament in the MF while the HV breakdown threshold is determined by only one single discharging path. 相似文献
2.
对飞秒激光等离子体单丝的导电性能进行空间分辨研究. 在消除测量时引入的接触电阻的影响后,得到单丝电阻在280-630 kΩ/cm范围. 为了进一步研究单丝的导电性能,对单丝诱导放电能力进行了空间分辨测量. 结果显示,最低放电阈值降低至自发放电的~50%. 从每段细丝的电阻和诱导放电阈值的空间分布看出:在成丝阶段,二者的变化趋势基本一致,细丝的电阻值和放电阈值均在焦点附近出现迅速下降. 将每段细丝的电阻和放电阈值相对应,建立了细丝诱导放电阈值-电阻的线性拟合关系,证实了细丝电阻对放电阈值的影响.
关键词:
飞秒激光
等离子体丝
电阻率
接触电阻 相似文献
3.
The abilities to trigger and guide high-voltage discharge by using single and multiple filaments (MFs) are experimentally studied. It is shown that the discharge voltage threshold can be reduced significantly in both regimes of single and MF; however, the MF does not gain a larger reduction than a single filament. This behavior of the MF is attributed to the single discharge path rather than simultaneous multiple ones as one might expect during the discharge process. 相似文献
4.
Triggering and guiding of high voltage discharge by using femtosecond laser filaments with different parameters 下载免费PDF全文
This paper demonstrates the triggering and guiding of the stationary
high voltage (HV) discharges at 5--40 kV by using plasma filaments
generated by femtosecond laser pulses in air. A significant
reduction of the breakdown voltage threshold due to the
pre-ionization of the air gap by laser filamentation is observed.
The discharge experiments are performed by using laser pulses with
different energy from 15--60 mJ. The electron density of filaments
is detected by sonography method. The influence of the electron
density of laser filaments on the triggering and guiding HV
discharge is experimentally investigated. The results have shown
that the behaviour of plasma filaments can strongly affect the
efficiency of triggering and guiding HV discharge. 相似文献
5.
Electrical breakdown in GaAs Schottky diodes creates a granular filamentary structure of submicron dimensions between the contacts. The filament exhibits very fast (<2 nsec) electrical switching between stable resistance states. Irrespective of the contact metal, the filament becomes superconducting when in the low-resistance state. Electron transport in all the resistance states is intergrain tunneling between metallic inclusions and is governed by an activation energy. Switching is not based on metal transport. 相似文献
6.
B. Corraze E. Janod L. Cario P. Moreau L. Lajaunie P. Stoliar V. Guiot V. Dubost J. Tranchant S. Salmon M.-P. Besland V. Ta Phuoc T. Cren D. Roditchev N. Stéphant D. Troadec M. Rozenberg 《The European physical journal. Special topics》2013,222(5):1046-1056
The Mott insulator compounds AM4Q8 exhibit a new type of volatile and non volatile resistive switchings that are of interest for RRAM application. We found that above a threshold electric field E TH of the order of a few kV/cm these compounds undergo a volatile resistive switching based on an avalanche process. For electric field much higher than the threshold avalanche breakdown field, the resistive switching turns non volatile. Our EDXS and STEM analyses show that the non volatile resistive switching originating from the avalanche breakdown can neither be ascribed to local chemical modifications nor to a local phase change with symmetry breaking at a resolution better than a few nanometer. This is in strong contrast with non volatile resistive switching reported so far that are all based on chemical or structural changes. Conversely, our results suggest that the avalanche breakdown induce the collapse of the Mott insulating state at the local scale and the formation of a granular conductive filament formed by compressed metallic domains and expanded “superinsulating” domains. 相似文献
7.
Multiple filamentation induced by input-beam ellipticity 总被引:1,自引:0,他引:1
We provide what is to our knowledge the first experimental evidence that multiple filamentation (MF) of ultra-short pulses can be induced by input beam ellipticity. Unlike noise-induced MF, which results in complete beam breakup, the MF pattern induced by small input beam ellipticity appears as a result of nucleation of annular rings surrounding the central filament. Moreover, our experiments show that input beam ellipticity can dominate the effect of noise (transverse modulational instability), giving rise to predictable and highly reproducible MF patterns. The results are explained with a theoretical model and simulations. 相似文献
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9.
本文通过对使用有效场强(或均方根场强)得到的微波大气击穿阈值表达式进行讨论, 指出其推导中所做的假设及这些假设应用到微波大气击穿过程中存在的问题. 然后分别使用解析理论和数值模拟对微波大气击穿过程中的有效电子温度变化过程和击穿阈值进行研究, 并将其与直流电场进行比较. 分析发现在高气压下, 电子能量转移频率高, 有效电子温度随电场大幅振荡, 由于电离频率随有效电子温度的增长率大于电子能量损失随有效电子温度的增长率, 因此在高气压时, 微波大气击穿阈值低于使用有效场强的击穿阈值. 通过大量分析, 给出了理论推导和数值模拟得到的微波大气击穿阈值拟合表达式. 相似文献
10.
Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor(VDMOS) devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films. 相似文献
11.
本文基于飞秒激光等离子体丝诱导击穿光谱对土壤重金属Cr元素含量进行了实验研究.利用荧光法对等离子体丝的长度进行测量,给出了在不同焦距聚焦透镜作用下土壤中Cr425.5 nm的谱线强度空间分布,实验给出了Cr元素的定标曲线.实验结果表明,土壤中Cr元素浓度分析测量的相对标准偏差小于5%,土壤中重金属Cr元素的检测极限为7.85 ppm.表明飞秒激光等离子体丝诱导击穿光谱技术在土壤重金属Cr元素含量的定量探测方面是完全可行的. 相似文献
12.
KrF laser-triggered spark gaps exploit the high dc-dielectric strength and low ultraviolet (UV) breakdown threshold of SF6 gas. Detailed measurements using a dc-charged pulser demonstrate subnanosecond jitter for switching a 0.5-cm gap operated at 80 kV with 7 mJ in 20 ns of 248-nm KrF radiation. A 200-kV pulse-charged 0.7-cm gap gives similar performance. 相似文献
13.
综合考虑高功率微波强电场作用下的热致快速电子效应、碰撞频率、电离频率等充分体现高功率微波特性的参量模型,基于高功率微波混合大气传输模型,提出了单脉冲高功率微波混合大气统一非线性击穿模型,定义了单脉冲高功率微波击穿阈值.理论研究结果表明:考虑中性气体分子极化作用以及电子的碰撞热效应后,大气击穿时对应的等离子体频率明显变大;大气击穿阈值随高度的增加先逐渐减小然后增大,在30-60 km区域存在一个极小值.开展了X波段窄带高功率微波单脉冲大气击穿实验研究,得到了典型条件下的高功率微波击穿现象、波形和阈值,且与理论结果一致性较好. 相似文献
14.
Structure and properties of laser quenched 4Cr13 steel 总被引:10,自引:0,他引:10
The structure and properties of laser quenched 4Cr13 steel were reported. The results show that: (1) Fine martensite is obtained after laser quenching. The highest content of retained austenite in the surface area 10 μm thick of laser hardened zone is 47. 13 percent, but only 3.6 percent of retained austenite is measured inside the laser hardened layer after the surface layer 10μm thick is worn off. (2) The hardness of laser quenched layer is much higher (HV_(0.1) 690) than that of the substrate (HV_(0.1) 237). (3) The wear resistance of laser quenched layer is 3.3 times higher than that of traditionally treated specimen and the corrosion resistance of 4Cr13 steel is also improved greatly by laser quenching. 相似文献
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16.
At a composition far above the percolation threshold, the resistance of a composite sample increases with time due to Joule heating as a constant current of a sufficiently large value is passed through the sample. If the current is less than a certain breakdown current (I(b)) the resistance eventually reaches a steady value with a characteristic relaxation time tau(h). The latter diverges with current I as tau(h) approximately (1-I(2)/I(2)(b))(-z). The value of the exponent z displays large fluctuations leading to unusual scaling of the relaxation time. It is shown that the results lead to important conclusions about the nature of breakdown phenomena. 相似文献
17.
The current study investigates buildup and breakdown of echo suppression for stimuli presented over headphones. The stimuli consisted of pairs of 120-micros clicks. The leading click (lead) and the lagging click (lag) in each pair were lateralized on opposite sides of the midline by means of interaural level differences (ILDs) of +/-10 dB or interaural time differences (ITDs) of +/-300 micros. Echo threshold was measured with an adaptive one-interval, two-alternative, forced-choice procedure with a subjective decision criterion, in which listeners had to report whether they heard a single, fused auditory event on one side of the midline, or two separate events on both sides. In the control conditions, referred to as the "single" conditions, echo threshold was measured for a single click pair, the test pair, presented in isolation. In addition to the control conditions, two kinds of test conditions were investigated, in which the test pair was preceded by 12 identical conditioning pairs: in the "same" conditions, the interaural configuration (ILDs or ITDs) of the conditioning pairs was identical to that of the test pair; in the "switch" conditions, the interaural configuration of lead and lag was reversed between the conditioning pairs and the test pair, in order to produce a switch in the lateralizations of the stimuli between the conditioning train and the test pair. No matter whether the lateralization of the clicks was produced by ILDs or by ITDs, most listeners experienced a buildup of echo suppression in the "same" conditions, manifested by a prolongation of echo threshold relative to the respective "single" conditions. However, the breakdown of echo suppression was much stronger in the ILD-switch than in the ITD-switch conditions. In five out of six listeners, the ITD switch had hardly any effect on echo threshold, although the ITDs (+/-300 micros) produced roughly the same degree of lateral displacement as the ILDs (+/-10 dB). These results suggest that the dynamic processes in echo suppression operate differentially in pathways responsible for the processing of interaural time and level differences. 相似文献
18.
富勒烯(C60和C70)薄膜可外延生长在新鲜解理的云母(001)平面.以这富勒烯层为衬底,将金属薄膜蒸镀在其上,便构成典型的二维渗流系统.蒸镀过程在超高真空系统中完成,并同时对样品的电阻特性进行原位测量.随着外加电压的增加,观测到样品电阻可逆的变化现象与不可逆的电击穿现象.在渗流阈值附近,击穿电流Ib与样品电阻R之间表现出幂指数关系:Ib~R-α.指数α比前人实验给出的数值和Nodes-Links-Blobs模型的预期值小得多,而且随着衬底材料的不同而不同.基于金属和富勒烯界面相互作用的理论,对这些现象作了解释
关键词: 相似文献
19.
The enhancement of breakdown threshold is of benefit to the high power microwave transmission. We propose a magnetic field in the transverse direction to the electric field to enhance the breakdown threshold. A theory of electric field threshold with crossed magnetic field for short pulse is developed, and verified by particle-in-cell/Monte Carlo collision (PIC/MCC) simulations. The result shows that the crossed magnetic field can enhance the breakdown threshold significantly. 相似文献