  We report on the preparation of carbon nanotube quantum dots using
superconducting electrodes made of niobium. Gate-controllable supercurrents
with values of up to 30 nA are induced by the proximity effect. The IV-curves
are hysteretic at low temperature and the corresponding switching histograms
have a width of ~0.5-2. An on-chip resistive environment integrated in the
sample layout is used in order to increase the switching current.
