Glossary

The vocabulary of pinches, defined the way the family's repositories use it.

Pinch

A plasma confined by the magnetic field of the current flowing through it (Z-pinch) or induced in it (theta-pinch); the dense plasma focus is a pinch formed at the end of a coaxial rundown.

Bennett relation

\(\mu_0 I^2/8\pi = N k_B(T_e + T_i)\): the integrated balance of kinetic pressure against the azimuthal field of the column's own current (Bennett 1934).

Bennett profile

\(n(r) = n_0/(1 + r^2/a^2)^2\), the particular equilibrium the Z-pinch core evaluates, with scale radius \(a\) and line density \(N = \pi a^2 n_0\).

Line density \(N\)

Ions per unit length of the column.

Sausage (\(m = 0\)) and kink (\(m = 1\))

The axisymmetric necking and the helical bending instabilities of a pinched column; both grow at about \(k v_A\).

Kadomtsev criterion

\(-\mathrm{d}\ln p/\mathrm{d}\ln r < 4\gamma_{\mathrm{ad}}/(2 + \gamma_{\mathrm{ad}}\beta)\) for \(m = 0\) stability; the Bennett profile fails it at every radius for \(\gamma_{\mathrm{ad}} = 5/3\).

Sheared-flow stabilisation

An axial velocity shear above \(0.1\,k v_A\) stabilises the modes (Shumlak & Hartman 1995); the family's second Z-pinch configuration.

Pease–Braginskii current

The current above which bremsstrahlung exceeds ohmic heating and the column contracts radiatively; ≈ 1.4 MA for a hydrogenic plasma at \(\ln\Lambda = 10\).

Sharp-boundary model

A plasma of uniform pressure with a sharp edge in a vacuum field, the model of the Scyllac review; its relations carry \(1 - \beta\) denominators and need \(\beta < 1\).

Implosion heating, adiabatic compression

The two stages of theta-pinch heating: a shock driven by the fast-rising field, then slower compression as the field keeps rising; declared as configuration facets, not evaluated.

\(l = 1, 0\) fields

Helical and bumpy auxiliary fields that hold a toroidal theta-pinch in equilibrium against the toroidal drift (Scyllac).

Wall stabilisation

The conducting coil at radius \(b\) stabilises the \(l = 1\)-driven \(m = 1\) mode when \(a/b\) is large enough.

End loss

The escape of plasma through the open ends of a linear theta-pinch, \(\tau \propto L/T_i^{1/2}\) in the review's empirical fit.

Snowplow

The current sheath sweeping up the fill gas as it runs down the coaxial annulus; the terminal speed follows from the balance of magnetic drive and swept mass.

Rundown, roll-over, radial collapse, pinch

The phases of a plasma-focus shot; the core declares them as device truth and integrates none of them.

Mass and current factors \(f_m, f_c\)

The Lee model's fitted fractions of swept mass and effective current in the axial and radial phases.

Drive parameter

The Lee model's speed factor of a machine, reproduced for PF1000 and NX3 within 1 % from their printed inputs.

Beam-target yield

Neutrons from fast deuterons striking the fill gas; the dominant term the plasma-focus literature fits, a consistency instrument here.

Evidence maturity

One of six states per capability; all three cores are at computational_prototype, and none of the states means machine-ready, safety-certified or reactor-ready.