A detailed design for a synchrotron light source optimised for the nec
essities of the Spanish scientific community is in progress. An overvi
ew of the general features, requirements and problems associated with
the vacuum system for this future light source is presented here. For
a good performance of the storage ring, a beam-on operating pressure o
f ca 10(-9) mbar or better is needed. An analysis of the effects of ga
s desorption due to the emission of synchrotron radiation on the vacuu
m system as well as its effect on the lifetime of the machine will be
described. (C) 1997 Elsevier Science Ltd.