XeCl激光诱发SF_6气体击穿及高压开关触发特性的研究

TRIGGERING CHARACTERISTICS OF SF_6 GAS SWITCH TRIGGERED BY XeClLASER

给出了ＸｅＣｌ激光（３０８ｎｍ）诱发ＳＦ＿６气体击穿及高压开关触发特性的研究结果。ＳＦ＿６气体击穿所需要的ＸｅＣｌ激光的功率密度很强地随气体压强而变。在ＳＦ＿６气体压强为０．０２ＭＰａ时，击穿功率密度为４．６ＧＷ／ｃｍ￣２，当压强为０．０４８ＭＰａ时，击穿阈值达最小值为３．２ＧＷ／ｃｍ￣２，而在高气压情况（气压大于０．０２ＭＰａ），其所需功率密度趋于饱和为４ＧＷ／ｃｍ￣２。采用激光触发间隙开关系统（ＬＴＧＳ），获得良好ＳＦ＿６气体开关触发特性：对自击穿电压Ｖ＿（ａｂ）≈６０ｋＶ的小型开关，在充电电压为Ｖ＿（ｃｈ）＝０．９６Ｖ＿（ａｂ）时，得开关延迟时间ｔ＿ｄ≈２０ｎｓ，抖动时间σ≈２６０ｐｓ。

AbstractExperimental results are presented on the triggering characteristics of SF_6 gas switch triggered byXeCl laser 308nm. We have also clarified the breakdown threshold of SF_6 gas and energy absorption ofXeCl laser in SF_6 as a function of pressure. At pressure of 0.5MPa for SF_6, when the input energy ofXeCl is larger than 230mJ,the breakdown of SF_6 occurs. In this case,more than 15mJ of laser energy isabsorbed by SF_6. A time history of plasma luminescence was studied by using streak camera IMACON790.It was foud the light of plasma was emitted immediately within 5ns after the laser beam arrived atfocusing point. Hence,it is possible to produce plasma very quickly after the irradation of the laser. In order to study the breakdown threshold of SF_6 gas following relation was used to estimate thepower density of the laser. here E is the output energy of laser; T= 37%,the total transparency of beamspliter,focus lens andquartz window;t is the pulse duration of laser,S is the cross section of laser;l is the luminescencelength of visible plasma. The power density of XeCl laser required for SF_6 breakdown(P)strongly changes with the changeof pressure. When the pressure of SF_6 gas is 0.02MPa,the power density of XeCl laser for SF_6 break-down p≈4.6GW/cm￣2. For pressure around 0.48MPa,it approaches to the minimum(≈3.2GW/cm￣2).At high pressure the breakdown tl1reshold increases to saturate to 4GW/cm￣2. Excel-lent triggering behaviour for SF_6 gas switch has been obtained by LTGS system. For small switchwith self-breakdown voltage V_(ab)=60kV. at the charge voltage V_(ch≈0.96V_(ab), we find delay timet_d≈20ns and jitter time σ≈260ps.