Glossary

The vocabulary of open-field confinement, defined the way the family's repositories use it.

Open field line

A field line that leaves the confinement region; particles on it are lost unless reflected or plugged.

Mirror ratio \(R_m\)

Field at the throat over field at the midplane, \(B_{\max}/B_{\min}\); diamagnetically deepened as \(R_{\mathrm{vac}}/\sqrt{1-\beta}\).

Loss cone

The pitch angles at the midplane, \(\sin^2\theta < (1 + q\Delta\phi/E)/R_m\), whose particles are not reflected and escape.

Ambipolar potential

The electrostatic potential that forms because electrons leave a mirror faster than ions; it widens the ion cone and narrows the electron cone.

Tandem mirror, end plug, thermal barrier

A central cell plugged at both ends by denser end cells whose potential reflects central ions; a thermal barrier isolates the plug electrons.

Gas-dynamic mirror

The high-collisionality regime in which outflow is governed by the mirror ratio and the sound speed, \(\tau \approx R_m L_p/c_s\).

Pastukhov function \(G\)

\(\sqrt{1+1/x}\ln\frac{\sqrt{1+1/x}+1}{\sqrt{1+1/x}-1}\), the mirror-ratio factor of the Pastukhov confinement time.

Finite-Larmor-radius stabilisation

Azimuthal modes above \(m_{\mathrm{crit}} = 2a^2/(L_p\rho_i)\) are stabilised by the ions' finite gyroradius; \(m = 1\) is not.

Adiabaticity \(\alpha\)

\(L_B/\rho_\parallel\): how many parallel gyro-lengths fit in the field-gradient scale; non-adiabatic effects matter at \(\alpha \le 10\).

Magnetic cusp, point cusp, line cusp

The field of opposed coil currents with a central null; the plasma leaks through sheath-scale apertures on the axis (point) and between coils (line).

Spindle cusp, picket fence

Two opposed coils; a row of alternating coils.

Levitated dipole

A superconducting ring floating in the field of a levitation coil, confining plasma on its own closed dipole field lines.

Ampere-turns \(NI\)

The magnet strength of a multi-turn winding; the source's floating coil has 716 turns.

Inductive charging

Discharging a charging coil from \(I_C\) to zero leaves \(I_F = (M_{CF}/L_F)I_C\) in the floating coil by flux conservation.

Levitation margin

Levitation force over weight; the anchor fixture derives the field gradient that gives exactly one.

Flux-tube volume \(U\)

The volume per unit flux of a field line tube; in a dipole it expands outward so strongly that \(p_0/p_{\mathrm{sol}} < (U_{\mathrm{sol}}/U_0)^\gamma\) admits very peaked profiles.

Printed versus declared

A printed value is one a filed source prints and the core reproduces; a declared value is one the configuration carries because the source does not print it, and the record says so.

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.