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Hanke, K.

Paper Title Page
WEO2A02 A Time-resolved SEM Monitor with Large Dynamic Range 434
  • M. Hori
    MPQ, Garching, Munich
  • K. Hanke
    CERN, Geneva

The Linac4 at CERN will provide 160-MeV negative hydrogen beams of high intensity N =2x1014 ions/s. Before this beam can be injected into the CERN PS Booster or future Superconducting Proton Linac for further acceleration, some sequences of 500-ps-long micro-bunches must be removed from it, using a beam chopper. We developed a monitor to measure the time structure and spatial profile of this chopped beam, with resolutions 1 ns and 2mm. Its large active area 40mm x 40mm and dynamic range also allows investigations of beam halos. The ion beam first struck a carbon foil, and secondary electrons emerging from the foil were accelerated by a series of parallel grid electrodes. These electrons struck a phosphor screen, and the resulting image of the scintillation light was guided to a thermoelectrically cooled, charge-coupled device camera. The time resolution was attained by applying high-voltage pulses of sub-nanosecond rise and fall times to the grids. The monitor has been tested with 700-ps-long UV laser pulses, and a 3-MeV proton beam. Its response over a wide range of beam intensities between 5 and 4x108 electrons emitted from the foil per pulse was studied.


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