Segmented anode structure is always used to the structure design of the laminar plasma torch to avoid the large scale shunting,which would result in a pulsation of the laminar plasma jet.However,when the length of the inter-electrode is longer than its limitation,a new anode attachment and a new cathode attachment always appear on the inter-electrode,which is named as double arc phenomenon.The double arc phenomenon leads to a serious heat load of the inter-electrode,resulting in a serious ablation of the inter-electrode and a fluctuation of the plasma jet.In order to prolong the service life of the inter-electrode and improve the stability of the plasma jet,the double arc phenomenon should be avoided.Firstly,based on the assumptions,the analysis models of the laminar plasma torch working with normal condition and double phenomenon were built to analyze the underlying mechanism of the double phenomenon.Besides,according to the principle of minimum voltage,the design requirements of the inter-electrode to avoid the generation of double arc were derived.Then,based on the above analysis,the measures of suppressing the double arc phenomenon were proposed,which included improving the cooling channels of the plasma torch to optimize the cooling effect of arc chamber wall,then decreasing the temperature of the cold layer;increasing the working gas flow rate to enhance the arc compression,which could increase the thickness of the cold layer;limiting the axial length of the inter-electrodes to decrease the corresponding arc voltage drop.
