Performance and operational experience with CERN-lithium lenses

Lithium lenses were originally developed by the INP at Novosibirsk/USSR for the collection of positrons downstream from the converter target. With the advent of proton-antiproton colliders for which efficient bar p sources are required, Li-lenses serve also as the first matching element [1],[2] which transforms the strongly divergent bar p-beam into a parallel one. This paper reports on the design of lithium lens developed at CERN for the ACOL bar p source. Small lenses with diameters of 2 cm have been extensively tested in the laboratory with peak currents up to 625 kA, yielding a field gradient of up to 1000 T/m. During the commissioning of ACOL, such a lens was used successfully in the beam at its design current of 420 kA. For future use at ACOL, large lenses with a diameter of 3.6 cm have been built and submitted to current pulses of above 800 kA, providing gradients above 400 T/m. The operational experience with these lenses, their optical parameters and their performance limits are discussed