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Author Andersen, M. ♦ Boccardi, A. ♦ Bozyigit, S. ♦ Bravin, E. ♦ Lefevre, T. ♦ Rabiller, A. ♦ Roncarolo, F.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Measurement Satellite Bunch Lhc ♦ Satellite Bunch ♦ Entire Lhc Ring ♦ Synchrotron Light Measurement ♦ Rf Gymnastics ♦ Time Resolution ♦ Longitudinal Density Monitor ♦ Arrival Time ♦ Lead Ion Bunch ♦ Transverse Beam Size ♦ Empty Rf Bucket ♦ High Energy ♦ Bunch-by-bunch Luminosity Normalization ♦ Synchrotron Light ♦ Dynamic Range ♦ Principal Instrument ♦ Dedicated Undulator ♦ Successful Modification ♦ Detector Deadtime ♦ Longitudinal Profile ♦ Heavy Ion ♦ Single Photon Counting ♦ Machine Protection ♦ Example Result
Abstract The RF gymnastics involved in the delivery of proton and lead ion bunches to the LHC can result in satellite bunches of varying intensity occupying the nominally empty RF buckets. Quantification of these satellites is crucial for bunch-by-bunch luminosity normalization as well as for machine protection. We present an overview of the longitudinal density monitor (LDM) which is the principal instrument for the measurement of satellite bunches in the LHC. The LDM uses single photon counting of synchrotron light. The very high energies reached in the LHC, combined with a dedicated undulator for diagnostics, allow synchrotron light measurements to be made with both protons and heavy ions. The arrival times of photons are collected over a few million turns, with the resulting histogram corrected for the effects of the detector’s deadtime and afterpulsing in order to reconstruct the longitudinal profile of the entire LHC ring. The LDM has achieved a dynamic range in excess of 10 5 and a time resolution of 90 ps. Example results are presented and the successful modification of the system to prevent dependence on the transverse beam size is shown.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study