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Wire scanners at LEP

Two sets of wire scanners, each for measuring the horizontal and vertical profile, are installed in LEP in a straight section where the dispersion in both planes is zero. The authors present the design and discuss some limitations of the instrument. A carbon fiber with a diameter of 36 mu m moves through the beam with a speed of about 0.5 m/s. The bremsstrahlung photons generated by the passage of the wire through the beam are detected in scintillators located 80-m downstream. During the first months of LEP operation, the fibers were destroyed occasionally. The various causes, tests and remedies are discussed. At injection energy a significant blowup of the beam results from the wire scan and has to be taken into account for the estimation of the genuine emittance. A model of this blowup is proposed, where the effect is renormalized on the actual measured data. This provides an effective data treatment to obtain the unperturbed beam size.<<ETX>>

LHC beam instrumentation

Six years before the scheduled commissioning of the LHC at CERN, the basic list of beam instruments has been established. This early date is needed due to the impact of the mechanical design of some detectors (mainly the beam position detectors) on the cryogenic part of the machine as well as for other projects due to the long R&D period (emittance measurements, tune and chromaticity diagnostics and control). This paper gives a detailed overview of the basic requirements and specifications of all beam instruments foreseen for transfer lines and main rings.