Study On The Closing Switch Techniques Of "Z-pinch" Accelerator

The mechanism of laser triggered multi-stage multi-channel switch, the switching properties of SF₆-N2 and SF₆-Ar mixtures and the design techniques of multi-channel field distortion switch was studied. The experimental and calculated results were reported in this paper. The works in modeling the UV laser triggered spark gap and the laser triggered multi-stage multi-channel switch were reported too. A 200kV laser triggered multi-stage multi-channel switch, a 200kV/100kA multi-channel ring rail electrode field distortion switch and a 5MV laser triggered multi-stage multi-channel switch were designed and tested. The main results and conclusions of this dissertation are as follows:(1) The switching property of SF₆-N₂, SF₆-Ar mixtures and the design techniques of multi-channel field distortion switch were studied. A 0-demension "2-2" model was developed to study the interaction of the UV laser with SFe gas and SF₆-N₂ mixtures. The results of calculations and experiments show that the delay and jitter increased as the percentage of SF₆ in SF₆-N2 mixtures increased. The results of experiments show that the delay of SF₆-Ar follows the same rule. The U_thU_sb increased as the percentage of SF₆ in SF₆-N₂ mixtures increased. The delay decreased abruptly as the wavelength of laser decreased. The delay, jitter and threshold voltage decreased exponentially as the energy of laser pulse increased. The delay of gaps filled with SF₆-Ar, SF₆-N₂ mixtures increased as the percentage of SF₆ increased when the gaps were triggered by high voltage pulse and this rule didn't changed with the field utilization. The self-breakdown voltage filled SF₆ mixtures could be fit and estimated by the following fomulus:In which U_mix is self-breakdown voltage in kV, ξ is the volume percentage of SF₆ in mixtures, u is the field utilization factor (u =E_av/E_max), d is distance of gap in cm, P is the pressure in 100kPa.(2) The mechanism of laser triggered multi-stage multi-channel switch was studied. The results of experiments and calculations show that the delay and jitter decreasedexponentially as the working voltage increased. The delay and jitter decreased as the gaspressure increased (t_d ∝ P^-1 if E/P >0.8(E/P)_lim. The falling rate of t_d-P curve closelyrelated with E/P or the energy of laser pulse (E_laser tested. The threshold voltage didn'tdepend on the pressure apparently. The delay and jitter decreased exponentially as theE_laser increased. The falling rate of t_d-E_laser curve decreased as the E/P being testedincreased. The ratio between threshold and self-breakdown voltage (U_th/U_sb) decreasedexponentially as the E_laser increased. The t_d, t_j, U_th/U_sb would be saturated when E_laser wasmore than 10 mJ. The delay decreased as the volume percentage of SF₆ in mixturesincreased when E/P was constants. U_th rise linearly as the ξ (the volume percentage ofSF₆ in mixtures) increased. When the focal length of focus lens increased the delay andjitter were increased if N₂ was used as dielectric. However, if SF6-N2 mixtures were usedas dielectric the delay almost not varied as the focal length of focus lens increased. Theresults of calculation and experiments shows that adopting the SF₆-N₂ mixtures asdielectric, smoothing the field distribution in gaps and decreasing the capacity ofself-breakdown gaps would be effective methods to decrease the delay and jitter.(3) The design techniques of multi-channel field distortion switch were studied and a200kV/100kA ring rail electrode switch was designed and tested. The experimentalresults show that the field utilization factors higher the self-breakdown voltage and itsstability higher for the ring electrode gaps. The self-breakdown voltage of the gapsformed by sphere electrode in which u was largest didn't show the best stability becausethe bad smoothness of the surface after discharges caused by its hig...