Experimental deduction of isentropic exponent for ion and electron in high density argon plasma

The isentropic exponent for plasma was deduced from measurements of electron temperature, Te, and ion temperature, Ti, in terms of plasma density, np, with the assumptions of linear characteristics of plasma parameters on discharge parameter in LaB6 dc plasma. The isentropic exponent for electron, γ e , is estimated by 1.06 with isentropic relation (P=Cn γ ), and it agrees well the classical treatment of electron as isothermal, γ e ∼1. In order to determine isentropic exponent for ion, γ i , the isentropic relation was modified with including ion heating due to electron-ion collisions, P i =C i0 n p γ +C i1 n p 2 and P i =C i0 n p γ (1+C i1 n p ) where C i0, i1 is the fitting parameter as constant. The isentropic exponent for ion is deduced as 1.16 – 1.18 with modified isentropic relation. Although this is smaller than the case of mono-atomic gases (γ=1.67), it agrees very well to the theoretical result of Burm et al.[1]