The capabilities of adiabatic, current-carrying plasma lenses for the
final focus problem in heavy-ion-beam-driven inertial confinement fusi
on are explored and compared with the performance of non-adiabatic pla
sma lenses, and with that of conventional quadrupole lenses. A final f
ocus system for a fusion reactor is proposed, consisting of a conventi
onal quadrupole lens to prefocus the driver beams to the entrance aper
ture of the adiabatic lens, the plasma lens itself, and a high current
discharge channel inside the chamber to transport the focused beam to
the fusion pellet. Two experiments are described that address the iss
ues of adiabatic focusing, and of transport channel generation and sta
bility for ion beam transport. The test of the adiabatic focusing prin
ciple shows a 26-fold current density increase of a 1.5 MeV potassium
ion beam during operation of the lens. The lens consist of a discharge
of length 300 mm, filled with helium gas at a pressure of 1 Torr and
is pulsed with a current between 5 and 15 kA. The investigations of di
scharge channels for ion beam transport show that preionization of the
discharge channels with a UV laser can be an efficient way to direct
and stabilize the discharge.