an extremely high vacuum (xhv) chamber was fabricated and tested. the vacuum chamber of special surface finished (ex-process) aluminium alloy in oxygen and argon atmosphere. the chamber was assembled using tig welding in an argon atmosphere and by electron beam welding. the system was evacuated with a turbo-backed 300 1/s turbomolecular pump separated from the main chamber using a right angle valve. the liquid nitrogen shroud is installed inside the main vacuum chamber. the xhv is maintained by two 300 l/s sputter ion pumps and a titanium sublimation pump with a liquid nitrogen shroud these pumps are also made of aluminium alloy. an ultimate pressure of 3*10/sup -13/ torr was measured with a point collector gauge with a spherical anode mounted on an al-flange. residual gas analysis in the order 10/sup -13/ torr was performed by a newly developed q-mass filter. to suppress outgassing from the quadrupole electrode, the ion source is mounted on an al-flange separated from the quadrupole electrode