A focusing insertion will be constructed at an intersection of the ISR, to achieve a reduction of the effective beam height by about a factor 6 in the interaction diamond and a corresponding increase of the luminosity. It will contain eight superconducting quadrupole magnets. capable of Droducing eradients of 43 Tm1 in a warm bore of 173 mm diameter: four of them have a magnetic length of 1.15 m and four of 0.65 m. The magnets are also equipped with sextupole windings, to match the gradients to particle momenta over the beam width, and with dodecapole correction windings. After construction and successful operation of a prototype magnet in the laboratory, competitive tenders were obtained from industry on the basis of technical specifications and manufacturing drawings. The magnets proper and the cryostats are being manufactured under two separate contracts. The insertion will be installed within 1980 at intersection I8, for use in physics experiments with a large magnetic spectrometer.

The determination of the mass and the width of the Z boson at CERN's LEP accelerator, an e + e storage ring with a circumference of approximately 27 kilometres, imposes heavy demands on the knowledge of the LEP counter-rotating electron and positron beam energies. The precision required is of the order of 1 MeV or 20 ppm frequency. Due to its size the LEP collider is inuenced by various macroscopic and regional factors such as the position of the moon or seasonal changes of the rainfall in the area, as reported earlier. A new and not less surprising eect on the LEP energy was observed in 1995: railroad trains in the Geneva region perturb the dipole eld. A parasitic ow of electricity, originating from the trains, travels along the LEP ground cable and the vacuum chamber, interacting with the dipole eld. An account of the phenomenon with its explanation substantiated by dedicated measurements is presented.to be submitted to Nuclear Instruments and Methods

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