Plasma behaviour and the scaling relations in a coaxial plasma opening switch(POS)using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydro-dynamic(MHD)equations in conjunction with the generalized Ohm's law.The vacuum region onthe right of POS is included in the model and the influence of downstream flow on the conductioncharacteristics is discussed.It is found that with the penetration of magnetic field,the pure hydro-gen plasma is pushed downstream significantly;and POS still conducts current after the magneticfield arrives at the load edge of POS,which is different from the previous experimental results in amultispecies POS.It is because that the noticeable downstream plasma in the pure hydrogen POSmay continue to conduct the current,while in the multispecies POS,the downstream plasma isunimportant so that the conduction phase ends soon after the magnetic field reaches the load edge.The scaling relation obtained from the simulations including the downstream region is consistentwith the experimental results.
