The compact synchrotron X-ray source, HELIOS built by Oxford Instrumen
ts, was commissioned at IBM's Advanced Lithography Facility at Fishkil
l New York in 1991. Key features and specifications for HELIOS are des
cribed, emphasising the unique features of this storage ring X-ray sou
rce. The performance of the first machine is outlined, based on almost
two years' routine operation, identifying key factors such as output
flux, beam lifetime and reliability. A description of the second HELIO
S and enhancements to its performance is included.