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By Dr Mahdya A. Yeser Lectures in Plasma Physics Slide 2 1.1 Nature of Plasma As the temperature of a material is raised, its state changes from solid to liquid and then to gas. If the temperature is elevated further, an appreciable number of the gas atoms are ionized and a high temperature gaseous state is achieved, in which the charge numbers of ions and electrons are almost the same and charge neutrality is satisfied on a macroscopic scale. When the temperature of a gas is T(K), the average velocity of the thermal motion of a particle with mass m, that is, thermal velocity vT is given by Slide 3 where is the Boltzmann constant = 1.380 658(12) 1023 J/K and T denotes the thermal energy. Therefore the unit of T is the joule (J) in MKSA units. In many fields of physics, the electron volt (eV) is frequently used as the unit of energy. This is the energy required to move an e lectron, charge e = 1.602 177 33(49)10^19 coulomb, against a potential difference of 1 volt: 1 eV = 1.602 177 33(49) 10^19 J. Slide 4 The temperature corresponding to a thermal energy of 1 eV is 1.16 10^4 K (= e/ ). The ionization energy of the hydrogen atom is 13.6 eV. Even if the thermal energy (average energy) of hydrogen gas is 1 eV, that is T 104 K, there exists a small number of electrons with energy higher than 13.6 eV, which ionize the gas to a hydrogen plasma. We can defined the plasma as: Plasmas are found in nature in various forms (see Fig. 1.1). Slide 5 Fig. 1.1. Various plasma domains in the n T diagram Slide 6 One example is the Earths ionosphere at altitudes of 70 500 km, with density n 10^12 m^3 and T 0.2 eV. Another is the solar wind, a plasma flow originating from the sun, with n 10^610^7 m^3 and T 10 eV. The suns corona extending around our star has density 10^14 m^3 and electron temperature 100 eV, although these values are position-dependent. The white dwarf, the final state of stellar evolution, has an electron density of 10^35 10^36 m3. Various plasma domains in the diagram of electron density n(m3) and electron temperature T (eV) are shown in Fig. 1.1. Slide 7 Active research in plasma physics has been motivated by the aim to create and confine hot plasmas in fusion research. In space physics and astrophysics, plasmas play important roles in studies of pulsars radiating microwaves or solar X-ray sources. Another plasma physics is the study of the Earths environment in space Practical applications of plasma physics are MHD (magneto hydrodynamic) energy conversion for electric power generation and ion rocket engines for spacecraft. Plasma processes for the manufacture of integrated circuits have attracted much attention recently Slide 8 Slide 9 One fundamental property of plasmas is charge neutrality. Plasmas shield electric potentials applied to the plasma. When a probe is inserted into a plasma and a positive (negative) potential is applied, the probe attracts (repels) electrons and the plasma tends to shield the electric disturbance. Let us estimate the shielding length. Assume that heavy ions have uniform density (n i = n 0 ) and that there is a small perturbation in the electron density n e and potential . Since the electrons are in the Boltzmann distribution with electron temperature Te, the electron density n e becomes .(1.3) 1.3Charge Neutrality and Landau Damping Slide 10 where is the electrostatic potential and is assumed. The equation for the electrostatic potential comes from Maxwells equations : E = then we can take the last eq. at where Slide 11 Slide 12 Slide 13 Definition of plasma: The forth state of matter,a quasineutral gas of charged and neutral particles which exhibits collective behavior. The plasma conditions : 1- 2- 3- Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Slide 22 Slide 23 Slide 24 Slide 25 Ch (2) Plasma Characteristics 2.1 Velocity Space Distribution Function Slide 26 Slide 27 Slide 28 How Slide 29 Slide 30 Slide 31 Slide 32 Slide 33 Slide 34 Slide 35 Slide 36 Slide 37 Slide 38 Slide 39 Slide 40 Slide 41 Slide 42 Slide 43 3.3 Equation of Motion of a Charged Particle Slide 44 Slide 45 Slide 46 Slide 47 Slide 48 4 Velocity Space Distribution Function and Boltzmanns Equation Slide 49 4.1 Phase Space and Distribution Function Slide 50 Slide 51 Slide 52 4.2 Boltzmanns Equation and Vlasovs Equation Slide 53 Slide 54 Slide 55 Slide 56 Slide 57