  The Liquid Argon Time Projection Chamber (LArTPC) is a prime type of detector
for future large-mass neutrino observatories and proton decay searches. In this
paper we present the design and operation, as well as experimental results from
ARGONTUBE, a LArTPC being operated at the AEC-LHEP, University of Bern. The
main goal of this detector is to prove the feasibility of charge drift over
very long distances in liquid argon. Many other aspects of the LArTPC
technology are also investigated, such as a voltage multiplier to generate high
voltage in liquid argon (Greinacher circuit), a cryogenic purification system
and the application of multi-photon ionization of liquid argon by a UV laser.
For the first time, tracks induced by cosmic muons and UV laser beam pulses
have been observed and studied at drift distances of up to 5m, the longest
reached to date.
