Double layer formation due to contact of different temperature plasmas

Potential difference formation between hot and cold plasmas are studied by means of a particle simulation. It is found that a double layer structure is formed on the hot plasma side of the contact surface between the cold and hot plasmas. The potential difference is approximately given by phi sub DL = (approx.) T sub eh/2e, where T sub eh and e are the hot electron temperature and the electronic charge, respectively. The double layer is accompanied by a negative potential dip on the low potential side (cold plasma) of the double layer, the depth of which is phi sub dip = (approx.) 2 T sub ec/e, where T sub ec is the cold electron temperature. Interestingly, however, the positive potential difference and the negative potential dip are created independently.