Plasma Physics — 60 Terms Defined

Alfvén Wave Plasma Physics m/s (Alfvén Velocity) A fundamental magnetohydrodynamic (MHD) wave in which ions in a magnetized plasma oscillate in response to magnetic field line tension. v_A = B / √(μ₀ ρ_plasma)

Bohm Sheath Criterion Plasma Physics m/s (Ion Acoustic Sound Speed c_s) A fundamental boundary condition stating that positive ions entering a non-neutral plasma sheath must enter with a velocity at or exceeding the ion acoustic sound speed c_s. v_ion ≥ c_s = √(k_B T_e / m_i) (at Sheath Entrance)

Bootstrap Current Plasma Physics MA (Plasma Current Fraction) A self-generated toroidal electric current in a tokamak plasma driven by trapped particle banana orbits in steep pressure gradients. I_bootstrap ∝ √ε (k_B / B_poloidal) (dn / dr)

Bremsstrahlung Radiation in Plasma Plasma Physics W/m³ (Radiated Power Density) Continuous electromagnetic radiation emitted when free plasma electrons undergo deceleration scattering off positive ions. P_brems ∝ Z_eff n_e² √T_e

Burning Plasma & Alpha Heating Plasma Physics MW (Alpha Particle Heating Power) The state of a fusion plasma where thermal heating from 3.5 MeV alpha particles produced in Deuterium-Tritium fusion reactions becomes the dominant heat source sustaining the plasma. P_alpha / P_heating ≥ 50% (Burning Plasma Condition Q ≥ 10)

Cold Atmospheric Pressure Plasma Jet Plasma Physics K (Gas Temperature ~300 K) A non-thermal plasma discharge generated at ambient atmospheric pressure where heavy ions remain near room temperature while free electrons reach high temperatures. T_gas ≈ 300 K (Room Temp), T_electron ~ 10,000–50,000 K

Coulomb Logarithm Plasma Physics Dimensionless Parameter (ln Λ) The natural logarithm of the ratio of maximum to minimum impact parameters in small-angle Coulomb collision integrals. ln Λ = ln(r_max / r_min) = ln(λ_D / b_min) ≈ 10–20

Cyclotron & Synchrotron Emission Plasma Physics W (Radiated Power) Electromagnetic radiation emitted by charged particles undergoing gyromotion acceleration around magnetic field lines in a plasma. P_rad = (2 e⁴ B² v_⊥²) / (3 m_e² c³) (Non-relativistic Cyclotron)

Debye Length Plasma Physics m (Meters) The characteristic spatial scale over which mobile charge carriers in a plasma screen out localized electrostatic potentials. λ_D = √(ε₀ k_B T_e / (n_e e²))

Dense Plasma Focus Plasma Physics kJ (Capacitor Energy) & Short Pulses (ns) A pulsed plasma device that uses electromagnetic forces to accelerate and pinch a plasma column into a short-lived, high-density hot spot. E_k ~ 10–100 kJ (Electromagnetic Acceleration and Pinch)

Divertor Plasma Physics MW/m² (Heat Flux Capacity) A component in a fusion tokamak that uses magnetic null points (X-points) to extract helium ash and heat exhaust from the plasma edge. Magnetic X-point Separatrix Boundary Geometry

Dusty Plasma Plasma Physics μm (Dust Size) & Charged State A complex plasma containing solid nanometer-to-micrometer scale dust grains that collect high negative charges from surrounding plasma electrons. Q_dust ~ - 10³ e to - 10⁵ e (Charged Micron Dust Grains)

Edge Localized Modes (ELMs) Plasma Physics MJ (Energy Loss Pulse per ELM) Periodic magnetohydrodynamic bursts occurring at the boundary edge pedestal of H-mode tokamak plasmas, expelling heat and particles toward reactor walls. Magnetohydrodynamic Peeling-Ballooning Boundary Instability

Field-Reversed Configuration (FRC) Plasma Physics Dimensionless High Beta ⟨β⟩ ~ 0.9 A high-beta compact toroid magnetic confinement concept where a closed-poloidal-field plasma torus is sustained inside a simple linear solenoid magnet. Average Beta ⟨β⟩ ≈ 1 (High-Beta Compact Toroid)

Fokker-Planck Equation for Plasmas Plasma Physics Kinetic Collision Operator The kinetic equation describing the time evolution of a plasma velocity distribution function subject to small-angle Coulomb collisions. (∂f / ∂t)_coll = -∇_v · (A f) + ½ ∇_v ∇_v : (B f)

Gyroradius & Cyclotron Frequency Plasma Physics m (Larmor Radius) & rad/s (Cyclotron Frequency) The helical orbital radius (Larmor radius r_L) and angular frequency (cyclotron frequency ω_c) of a charged particle orbiting a magnetic field line. r_L = (m v_⊥) / (|q| B), ω_c = (|q| B) / m

H-mode Confinement Plasma Physics s (Energy Confinement Time τ_E) High-confinement operating regime in tokamaks characterized by a steep edge pressure barrier (pedestal) and doubled energy confinement time. Energy Confinement Time τ_E(H-mode) ≈ 2 × τ_E(L-mode)

Hall Effect Thruster Plasma Physics N or mN (Thrust) & s (Specific Impulse ~1500–3000 s) A electric space propulsion plasma engine that accelerates ions across an electrostatic potential drop using trapped electrons in an annular magnetic field. F_thrust = ṁ v_exhaust, v_ex = √(2 e V_acc / m_ion)

Inertial Confinement Fusion Plasma Physics g/cm² (Areal Density) & Mbar (Implosion Pressure) A fusion energy approach that uses intense laser or ion beam pulses to rapidly compress and heat a millimeter-scale fuel capsule to fusion ignition conditions. ρ R ≥ 1 g/cm² (Compressed Areal Density)

Interchange & Flute Instabilities Plasma Physics MHD Flute Mode Instability A magnetohydrodynamic (MHD) instability where high-pressure plasma and low-density magnetic fields interchange spatial positions in regions of unfavorable magnetic curvature. Bad Curvature Condition: (∇P) · (∇B) > 0

Ionization Energy Plasma Physics eV (Electron-Volts) The minimum energy required to detach an electron from a neutral atom or ion, initiating gas-to-plasma phase transformation. E_ion = h ν - K_e (Saha Ionization Equation)

Kink & Sausage Instabilities Plasma Physics MHD Instability Modes Ideal magnetohydrodynamic (MHD) macro-instabilities occurring in current-carrying pinched plasma columns. m = 0 (Sausage Mode), m = 1 (Kink Mode)

Landau Damping Plasma Physics s⁻¹ (Damping Rate γ) The collisionless damping of electrostatic plasma waves caused by energy exchange between wave electric fields and particles moving near wave phase velocity. γ_L = (π ω_pe³ / (2 k²)) (df₀ / dv)|_(v = ω/k)

Langmuir Probe Plasma Physics A (Measured Current) & V (Bias Voltage) A diagnostic electrode inserted directly into a plasma to measure local electron temperature, plasma density, and floating potential from its current-voltage (I-V) curve. I(V) = I_i,sat - I_e,sat exp(e (V - V_plasma) / (k_B T_e))