Antiprotons in the ISR

A brief account is given of the events leading up to antiprotons in the Intersecting Storage Rings (ISR) followed by a synopsis of the characteristics and parameters of the physics runs made to date. Experience gained with critical operations, such as transfer line steering, injection optimization, stacking and phase displacement acceleration is reviewed bearing in mind the extremely low beam intensities. Special reference is made to the various machine improvements, namely the vertical transverse stochastic cooling for proton beams of up to 12 A, the transverse and longitudinal stochastic cooling for the antiprotons, the new antiproton beam position monitoring system in the transfer lines and ring and the use of two high-luminosity insertions. At the end of June 1982, a scheme for reaching higher luminosities by making multiple transfers from the Antiproton Accumulator (AA) and using longitudinal stochastic cooling in the ISR was demonstrated. The absence of any measurable loss rate during long periods of stable beam conditions has been used to set a new lower limit of 1000 h on the antiproton lifetime at rest. Finally, preparations are in progress to collide 3.5 to 6.5 GeV/c antiprotons with a hydrogen gas jet target.