  The H- Accelerator consists of a 750 keV Cockcroft Walton preaccelerator and
an Alvarez type 50 MeV linac. The accelerator has been in operation since 1961.
Since 1981, it has been used as the injector for the Intense Pulsed Neutron
Source (IPNS), a national user facility for neutron scattering. The linac
delivers about 3.5x1012 H- ions per pulse, 30 times per second (30 Hz), for
multi-turn injection to a 450 MeV Rapid Cycling Synchrotron (RCS). IPNS
presently operates about 4,000 hours per year, and operating when scheduled is
critical to meeting the needs of the user community. For many years the IPNS
injector/RCS has achieved an average reliability of 95%, helped in large part
by the preaccelerator/linac which has averaged nearly 99%. To maintain and
improve system reliability, records need to show what each subsystem
contributes to the total down time. The history of source and linac subsystem
reliability, and improvements that have been made to improve reliability, will
be described. Plans to maintain or enhance this reliability for at least
another ten years of operation, will also be discussed.
