CERN ATS note 2012 026 free download

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CERN-ATS-Note-2012-026 PERF BI DCCT Note RESULTS OF THE LHC DCCT CALIBRATION STUDIES C. Barschel1,2 , M. Ferro-Luzzi1 , J.J. Gras1 , M. Ludwig1 , P. Odier1 , and S. Thoulet1 1 CERN, Geneva, Switzerland 2 RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany May 24, 2012 Abstract An important aspect of luminosity calibration measurements is the bunch population product normal- ization. In the case of the LHC, the treatment of this normalization can be split into three subjects: the total current measurement, the corrections from the non-perfect longitudinal distribution and the relative amplitude of the individual bunch populations. In this note, we discuss the first item in details and in the context of the 2010 and 2011 luminosity calibration measurements performed for each LHC Interaction Point. Effects Internal to the DCCT, the sensitivity to external factors, uncertainty related to the abso- lute calibration and comparison of two systems are all addressed. The DCCT uncertainty and numerical examples are given. 1 CERN-ATS-Note-2012-026 PERF, May 24, 2012 Contents 1 Introduction 4 2 Description of the DCCT system 6 2.1 Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 Instrumental stability and linearity 9 3.1 Baseline subtraction method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 Automatic baseline correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3 Fourier analysis of the noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.4 In-situ tunnel measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.4.1 Long term stability over 12 hours . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4.2 Long term stability under load over 24 hours . . . . . . . . . . . . . . . . . . . . 22 3.4.3 DCCT Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22