Glossary

The vocabulary of electrostatic, beam-target and hybrid systems, defined the way the family's repositories use it.

Inertial-electrostatic confinement (IEC)

Ions accelerated and recirculated by an electrostatic potential well toward a dense core; the gridded fusor and the polywell.

Cathode grid, bridge, aperture

The spherical wire cathode; the wire between apertures; the opening ions pass through. Bridge half-angle \(\arctan(t/D)\).

Globe grid, symmetric grid

Latitude–longitude rings, \(2n_{\mathrm{long}}(n_{\mathrm{lat}}+1)\) apertures; great-circle rings meeting at crossings of \(n\) rings with aperture angle \(360^\circ/2n\) — 3, 6, 9, 15 rings give 8, 24, 48, 120 apertures.

Geometric and circular transparency

Open aperture area over sphere area; the area of the largest circles the apertures admit over sphere area; their ratio is exactly one for circular apertures.

Pass-count bound

\(\eta/(1-\eta^2)\), the most passes a recirculating ion can make through a grid of transparency \(\eta\); geometry alone, never a predicted count.

Virtual cathode, polywell

A negative potential well made of electrons trapped in a magnetic cusp; a transparency of exactly one, which bounds no number of passes at all.

Beam target, colliding beam

A beam on a fixed or flowing target; two counter-propagating beams. Non-thermal: the reaction kinematics are set by the beams.

Duane fit

The five-coefficient total cross-section formula the NRL Plasma Formulary tabulates for six light-ion reactions, in the frame of an incident ion on a target at rest.

Equivalent stationary-target energy

The energy a beam-on-target machine would need to reach the same centre-of-mass energy; four times the beam energy for equal-mass colliding beams.

Gamow boundary

The energy below which the fit's exponential overflows and the cross section is taken as zero, 0.0043 keV.

Maxwellian reactivity \(\langle\sigma v\rangle\)

The cross section averaged over a thermal distribution; the formulary's printed D–T table is the beam-target core's transcription check.

Stopping power

The energy a beam ion loses to the target's electrons; the reason the family declares its energy balance honestly and claims no gain.

Fusion–fission hybrid

A fusion neutron source coupled to a subcritical fission blanket that multiplies energy and breeds fissile fuel.

Subcritical, \(k_{\mathrm{eff}}\)

A blanket whose effective neutron multiplication factor is strictly below one: no self-sustaining chain. Neutron multiplication \(1/(1-k_{\mathrm{eff}})\).

Engineering \(Q'\)

Fusion power over the power recirculated to drive the plasma; electrical self-sufficiency of the ORNL molten-salt hybrid needs about 1.4.

Energy multiplication \(M\), breeding rate \(F\)

Blanket energy per source neutron over the neutron's energy; fissile atoms bred per source neutron. Different from the neutron multiplication, and not derived from it.

Conversion ratio \(C\), capture-to-fission ratio \(\alpha\)

Of the reactors that burn what the blanket breeds: how much of their fissile they replace themselves, and how much they waste to capture; \(C \ge 1\) is refused.

Capacity ratio \(R_o\), reactors supported \(N\)

Fission thermal power supported per unit fusion power, off-line; \(R_o\) over the thermal power ratio.

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.