A luminosity monitor for the Large Hadron Collider

The Large Hadron Collider (LHC) nominal luminosity is 1034 cm−2 s−1, but special runs at 1028 cm−2 s−1 are also foreseen. In order to cover a luminosity dynamic range of six orders of magnitude, we have studied a new concept of luminosity monitor based on a double mode detector, working as a secondary emission counter at the highest luminosity and as an ionisation chamber at lower levels. We present the description of the device and the results obtained during tests at the CERN PS and SPS beams.