SpaceChargeComp¶

A zero-length, passive marker that sets the space-charge compensation (neutralisation) factor from that point on in the lattice. The canonical use is LEBT neutralisation: residual-gas ionisation partially cancels the beam's self-field, and this element tells the tracker how much.

TL;DR¶

SPACE_CHARGE_COMP 0.95

from linac_gen.elements.space_charge_comp import SpaceChargeComp

scc = SpaceChargeComp(name="SCC1", factor=0.95)   # 95 % neutralised

factor is the neutralisation fraction: 0 = no compensation (full space charge), 1 = full compensation (no space-charge kick).

Tutorial¶

The element itself does nothing to the beam — apply(beam) is a no-op. When the tracker encounters it, it updates its internal space-charge scale to 1 − factor; every subsequent SC kick (2-D DC or 3-D PIC) is multiplied by that scale until the next SpaceChargeComp is encountered. Place one at the start of the LEBT and another (factor=0) where neutralisation ends (e.g. at the RFQ entrance chicane).

Two interactions to know about:

A FieldMap with Ki > 0 and a .scc profile overrides the global factor locally inside that map (see FieldMap).
Without an active SC path (zero current or no solver configured), the factor is stored but has nothing to scale.

Transfer matrix¶

Like any passive element, the transfer matrix is the 6×6 identity — its entire effect is on the tracker's space-charge state.

API reference¶

linac_gen.elements.space_charge_comp.SpaceChargeComp(
    name: str,
    factor: float = 0.0,
)

Parameter	Default	Notes
`name`	(required)	identifier
`factor`	0.0	neutralisation fraction, 0 (no compensation) to 1 (full compensation)

Source¶

linac_gen/elements/space_charge_comp.py:18 (element), linac_gen/tracking/tracker.py:233-235 (the tracker applying _sc_factor = 1 - factor).