Studies Of Thermodynamical Properties Of Two-dimensional Yukawa Liquids

Dust plasma refers to a plasma system containing solid dust particles.These dust particles in the plasma environment would be charged,and the final charge depends on various factors,like the dust particle size and the plasma conditions.Under typical laboratory plasma conditions,micron-sized dust particles are negatively charged,to thousands of elementary charges,due to the much higher mobility of free electrons than that of ions.Due to the shielding effects of free electrons and ions,the interaction between dust particles in two-dimensional(2D)dusty plasmas can be modeled as the Yukawa repulsion.The charge-to-mass ratio of these dust particles is much lower than that of free electrons and ions,as a result,the typical potential energy between neighboring dust particles is much larger than the averaged kinetic energy,i.e.,these dust particles would form a strongly-coupled system,similar to atoms or molecules in solids or liquids.In typical dusty plasma experiments,dust particles can be directly imaged and recorded using high-speed cameras.As a result,dust plasma is an excellent experimental model system with the diagnostic at the single particle kientic level,which has been successfully used in the investigations of many physics topics of solids and liquids.Besides experiments,computer simulations of 2D Yukawa liquids and solids have been used to study many properties of 2D dusty plasmas.The mechanical properties,thermal energy absorption and anharmonic properties of 2D liquid dusty plasmas have not been studied much.In the second chapter of this thesis,combined with their equation of state,the concept of cold energy and thermal energy in other fields is used to obtain the analytical expressions of the isochoric specific heat and Gruneisen parameter of 2D Yukawa lqiuids.Firstly,using the molecular dynamics simulation data,combined with the traditional definitions of cold/thermal pressure,the expressions of cold/thermal pressure of 2D Yukawa lqiuids are obtained using data fitting.Then,to decompose the total internal energy,the molecular dynamics simulation data are used to achieve the analytical expressions of temperature-independent cold energy and temperature-related thermal energy using data fitting.It is found that the cold pressure and cold energy data from the two data fittings well satisfy the thermodynamic relationship,demonstrating that these results of the cold/thermal pressure and cold/thermal energy are self-consistent.As a result,the analytical expression of the isochoric specific heat of the 2D Yukawa liquids ean be obtained from the derivative of the thermal energy with respect to the temperature.The isochoric specific heat varies with the shielding parameters and temperature,and the underlying physics is further clarified.In addition,using the obtained expressions of the thermal pressure/energy,the expression of the Gruneisen parameter of 2D Yukawa liquids is also obtained.The study of quick or intense processes of 2D liquid dusty plasmas was mainly focused on the kinetic level,however,their thermodynamics are not studied much.In the third chapter of this thesis,the adiabatic process of 2D Yukawa liquids is studied using the equation of state and the isochoric specific heat.Firstly,the volumetric thermal expansion coefficient and the relative pressure coefficient of 2D Yukawa liquids are derived from their equation of state.Then,the analytical expression of the heat capacity under constant-pressure conditions is obtained from the thermodynamic Maxwell relationship.Finally,from the obtained heat capacity under constant-pressure conditions and the isochoric specific heat,as the most important parameter to describe the adiabatic process,the heat capacity ratio of the 2D Yukawa liquids is obtained analytically.In additioin,the analytical expressions of the adiabatic elastic modulus and adiabatic sound speed are derived.Dust injection has recently been proposed as a diagnostic tool in magnetically confined fusion plasmas,attracting attentions in the field of tokamak physics.When it is injected into the tokamak plasma,the dust will ablate into the plasma state of the dust material.As a result,the in-situ diagnostics of the dust ablatation should reflect the local physics information of the tokamak plasma.However,the dust ablation procedure is very complicated,and it is still a possible technical problem whether these high-speed dusts can penetrate into the core region of tokamak before these dusts completely vanish.In the fourth chapter of this thesis,the development of the theoretical model of fusion dust ablation is reviewed to support the project of the Ministry of Science and Technology of China undertaken by our group.Furthermore,based on this ablation model,a preliminary estimate of the moving distance of injected dusts inside the HL-2A tokamak during the ablation of dusts with different materials is performed.While calculating the ablation time and the moving distance of dust particles in the plasma region of tokamak using this model,the shielding effect of neutral gas is considered,combined with the data of sublimation energy of dusts of different materials.