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Niveau: Supérieur, Doctorat, Bac+8

Chapter 3 GASEOUS ELECTRONICS In this chapter we study the properties of a plasma in an electric ﬁeld. Our treatment of magnetized plasmas will await consideration of individual charged particle orbits in spatially and time varying electric and magnetic ﬁelds presented in Chapter 4. Thus in this chapter, the Lorentz force is simple F = qE. We look at basic phenomena such as plasma breakdown, equilibrium, di?usion and plasma-wall interactions, including sheath physics and Langmuir probes. To commence, let us look at plasma equilibrium in the presence of an E-ﬁeld. 3.1 Plasma in an Electric Field Force balance – no collisions In this section we look at the force balance between plasma pressure and electric ﬁeld, ignoring the e?ects of collisions. Under these conditions, we retrieve the Boltzmann relation for a plasma immersed in a spatially varying electric potential (electric ﬁeld). To show this, we take E = Ek. The z-component of the plasma equation of motion Eq. (2.89) then reduces to mn [ ∂u ∂t + (u.?)u ] z = qnE ? ∂p ∂z where we have ignored collisions (i.e. we ignore di?usion processes). We simplify by further assuming that the system is in steady state (∂/∂t = 0) and that velocity gradients can be ignored, in which case the left side of the equation vanishes.

Chapter 3 GASEOUS ELECTRONICS In this chapter we study the properties of a plasma in an electric ﬁeld. Our treatment of magnetized plasmas will await consideration of individual charged particle orbits in spatially and time varying electric and magnetic ﬁelds presented in Chapter 4. Thus in this chapter, the Lorentz force is simple F = qE. We look at basic phenomena such as plasma breakdown, equilibrium, di?usion and plasma-wall interactions, including sheath physics and Langmuir probes. To commence, let us look at plasma equilibrium in the presence of an E-ﬁeld. 3.1 Plasma in an Electric Field Force balance – no collisions In this section we look at the force balance between plasma pressure and electric ﬁeld, ignoring the e?ects of collisions. Under these conditions, we retrieve the Boltzmann relation for a plasma immersed in a spatially varying electric potential (electric ﬁeld). To show this, we take E = Ek. The z-component of the plasma equation of motion Eq. (2.89) then reduces to mn [ ∂u ∂t + (u.?)u ] z = qnE ? ∂p ∂z where we have ignored collisions (i.e. we ignore di?usion processes). We simplify by further assuming that the system is in steady state (∂/∂t = 0) and that velocity gradients can be ignored, in which case the left side of the equation vanishes.

- ionized magnetized
- gradient can
- collision
- plasma
- di?usion coe?cient
- therefore very
- time between
- ions behind
- temperature plasma
- electron temperature

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Publié par | profil-zyak-2012 |

Nombre de lectures | 7 |

Langue | English |

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