Development of an aluminium lens

As part of the CERN Antiproton Collector project, strong lenses are required to focus a 26-GeV proton beam onto the antiproton production target as well as to collect the liberated antiprotons. Gradients of 1500 T/m are expected, making possible a very short and compact lens and thus avoiding excessive absorption of beam particles by the lens material. The problems caused by the skin effect are overcome by subdivision of the lens into three mutually insulated concentric tubes connected in series through electron-beam-welded return tubes. Characteristics of this lens such as the distribution of the penetrating current, and the resulting field distributions, as well as the ohmic temperatures and the magnetic and thermal stresses computed are described. The design of the lens and the present state of this development are discussed.