  The quasilinear particle flux arising from gyrokinetic instabilities is
calculated in the electrostatic and collisionless approximation, keeping the
geometry of the magnetic field arbitrary. In particular, the flux of electrons
and heavy impurity ions is studied in the limit where the former move quickly,
and the latter slowly, along the field compared with the mode frequency.
Conclusions are drawn about how the particle fluxes of these species depend on
the magnetic-field geometry, mode structure and frequency of the instability.
Under some conditions, such as everywhere favourable or unfavourable magnetic
curvature and modest temperature gradients, it is possible to make general
statements about the fluxes independently of the details of the instability. In
quasi-isodynamic stellarators with favourable bounce-averaged curvature for
most particles, the particle flux is always outward if the temperature gradient
is not too large, suggesting that it might be difficult to fuel such devices
with gas puffing from the wall. In devices with predominantly unfavourable
magnetic curvature, the particle flux can be inward, resulting in spontaneous
density peaking in the centre of the plasma. In the limit of highly charged
impurities, ordinary diffusion (proportional to the density gradient) dominates
over other transport channels and the diffusion coefficient becomes independent
of mass and charge. An estimate for the level of transport caused by
magnetic-field fluctuations arising from ion-temperature-gradient instabilities
is also given and is shown to be small compared with the electrostatic
component.
