Development of a detector for bunch by bunch measurement and optimization of luminosity in the LHC

Abstract

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high-luminosity insertions of the LHC each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (∼235 W at design luminosity 10 34 cm −2 s −1). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. Novel segmented, multi-gap, pressurized gas ionization chambers are proposed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal-to-noise ratio and by the very high radiation environment. The ionization chambers are instrumented with state-of-the-art low noise, fast, pulse-shaping electronics capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity of approximately 2×10 3 bunch crossings are sufficient for a 1% luminosity measurement.