Luminosity Monitor System Research Articles

Simulation study on luminosity feedback for horizontal beam stabilization at SuperKEKB

The SuperKEKB e+ e− collider uses highly focused ultra-low emittance bunches colliding every 4 ns to reach a very high luminosity of 8 × 1035cm−2s−1. It is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between the colliding beams in the presence of ground motion disturbances. For the horizontal motion, a luminosity monitoring system, based on measuring the rate of the Bhabha process at vanishing scattering angle, is developed as input signal to the feedback system. The relative precision needed for this monitor is studied in detail, for the different successive stages of luminosity operation, based on a full simulation of this system, including the detector, DAQ, lock-in amplifier, and feedback control.

MPX Detectors as LHC Luminosity Monitor

A network of 16 Medipix-2 (MPX) silicon pixel devices was installed in the ATLAS detector cavern at CERN. It was designed to measure the composition and spectral characteristics of the radiation field in the ATLAS experiment and its surroundings. This study demonstrates that the MPX network can also be used as a self-sufficient luminosity monitoring system. The MPX detectors collect data independently of the ATLAS data-recording chain, and thus they provide independent measurements of the bunch-integrated ATLAS/LHC luminosity. In particular, the MPX detectors located close enough to the primary interaction point are used to perform van der Meer calibration scans with high precision. Results from the luminosity monitoring are presented for 2012 data taken at sqrt(s) = 8 TeV proton-proton collisions. The characteristics of the LHC luminosity reduction rate are studied and the effects of beam-beam (burn-off) and beam-gas (single bunch) interactions are evaluated. The systematic variations observed in the MPX luminosity measurements are below 0.3% for one minute intervals.

Simulation study of real-time monitor for BEPC-II luminosity

A fast and real time luminosity monitor system will be used in the BEPC-II (Beijing Electron Positron Collider, China). Photons generated in radiative Bhabha scattering at the interaction point are transformed into charged particles, and then the luminosity of each bunch pair is measured through collecting the Cherenkov light produced by charged particles in fused silica. The whole process happening in the detector is simulated. The physics acceptance and detection threshold with the monitor accuracy of 1% are set based on the simulation spectra of photoelectron yield calibrated by e− beam data.

A proposed luminosity monitor for CMS based on small angle diamond pixel telescopes

Measurement and monitoring of the luminosity in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN will be essential both for physics measurements (e.g., production cross-sections of top, Higgs and SUSY) and for accurate simulation of rate dependent detector characteristics. Our proposal for a CMS luminosity monitoring system consists of a set of small angle diamond pixel telescopes. These telescopes are situated close to the beam pipe where radiation levels are very high and room for mechanical structures and services is quite limited. The CMS pixel readout chip provides a fast over-threshold signal that will be used to monitor the bunch-to-bunch luminosity variations by counting the number of particles that hit the telescope array in each beam crossing. The proposed system will determine the individual bunch-to-bunch luminosity variations to a precision of better than 1% over a 1 s time scale.

A luminosity monitor for the A4 parity violation experiment at MAMI

A water Cherenkov luminosity monitor system with associated electronics has been developed for the A4 parity violation experiment at MAMI. The detector system measures the luminosity of the hydrogen target hit by the MAMI electron beam and monitors the stability of the liquid hydrogen target. Both are required for the precise study of the count rate asymmetries in the scattering of longitudinally polarized electrons on unpolarized protons. Any helicity correlated fluctuation of the target density leads to false asymmetries. The performance of the luminosity monitor, investigated in about 2000 h with electron beam, and the results of its application in the A4 experiment are presented.

A fast luminosity monitor system for PEP II

The PEP II fast luminosity system provides a measurement of luminosity to the control system with a time constant of 0.3 s and fluctuations less than 0.1% for this interval, adequate for use in feedback systems. Continuous visual updates of luminosity are provided. The alignment of the positron beam at the collision point can also be monitored, and there is a visual display of the luminosity associated with each bunch pair in the machine, sampled approximately every 2 s.

A luminosity monitor system for the JETSET experiment at LEAR

Abstract A luminosity-monitor system for the JETSET experiment at LEAR is described. Four silicon-strip detectors are used as position sensitive devices to monitor the elastic p p-scattering. The design concept, data-acquisition and results of the detector system are presented. On-line monitoring is used to assure the proper operation of the JETSET experiment.

A Luminosity Monitor at PEP

The luminosity monitor system utilized by the MKII Detector and by the PEP operators is described. This system processes information from 56 photomultipliers and calculates independent luminosities for each of the 3 colliding bunches in PEP. Design considerations, measurement techniques, and sources of error in the luminosity measurement are discussed.