Bottura, L Buzio, M Pauletta, S Smirnov, N Measurement of Magnetic Axis in Accelerator Magnets: Critical Comparison of Methods and Instruments We review 19 measurement systems for the magnetic axis of accelerator magnets, used to align machine components. First, we provide some background information and we describe briefly the instruments and methods used for the magnetic and the geometric measurements. For all systems we give then a performance summary in terms of magnet parameters and measurement uncertainties. The dataset is analyzed statistically to identify the parameter with the most influence on the total uncertainty, which is magnet length. Finally we derive scaling laws relating uncertainties to magnet's parameters, and we discuss the relative performance of the various methods. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=at-2007-024; http://cds.cern.ch/record/1092658/files/at-2007-024.pdf;

Imported from Invenio. Calvi, M Angrisani, L Bottura, L Di Castro, M Masi, A Siemko, A Data Analysis of Transient Energy Releases in the LHC Superconducting Dipole Magnets Premature training quenches are caused by transient energy released within the LHC dipole magnet coils while it is energized. Voltage signals recorded across the magnet coils and on the so-called quench antenna carry information about these disturbances. The transitory events correlated to transient energy released are extracted making use of continuous wavelet transform. Several analyses are performed to understand their relevance to the so called training phenomenon. The statistical distribution of the signals amplitude, the number of events occurring at a given current level, the average frequency content of the events are the main parameters on which the analysis have been focalized. Comparisons among different regions of the magnet, among different quenches in the same magnet and among magnets made by different builders are reported. Conclusions about the efficiency of the raw data treatment and the relevance of the parameters developed with respect to the magnet global behavior are finally given. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2008-1069; http://cds.cern.ch/record/1092674/files/lhc-project-report-1069.pdf;

Imported from Invenio. Sammut, N J Benedico-Mora, E Bottura, L Galbraith, P Giloteaux, D Greco, G Haverkamp, M Marchesotti, M Masi, A Micallef, J Pieloni, T Smirnov, N Tikhov, A A Hall Plate Based Instrument to Measure the Snapback in the Large Hadron Collider Superconducting Dipole Magnets The decay and snapback of the magnetic field multipoles in superconducting particle accelerators like the Large Hadron Collider (LHC) could result in a significant particle beam loss unless adequately compensated. Whilst standard instrumentation used to measure the field quality of the superconducting magnets is good enough to measure the harmonic decay, it is not fast enough to measure the snapback. Therefore, a state of the art instrument was recently developed at CERN to measure the most important harmonics with a high measurement frequency and hence improve the understanding of the snapback phenomenon. In this paper we describe the instrument's principle of operation, its mechanical arrangement, its compensation system and its digital acquisition system. We also compare the performance of two different techniques implemented to achieve the necessary measurement resolution of 6 orders of magnitude lower than the main superimposed dipole field. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2008-1068; http://cds.cern.ch/record/1092667/files/lhc-project-report-1068.pdf;

Imported from Invenio. Buzio, M Galbraith, P García-Pérez, J Laface, E Pauletta, S A Device to Measure Magnetic and Mechanical Axis of Superconducting Magnets for the Large Hadron Collider at CERN The LHC will be composed of 1232 horizontally curved, 15 meter long, cryodipoles and 474 Short Straight Sections, being assembled by different manufacturers. Magnetic axis alignment is an essential part of the magnets quality for two reasons: first, to be able to install correctly the magnets in the tunnel w.r.t. the reference beam orbit; secondly, to assess the relative alignment between the magnets composing the assembly, i.e. spool pieces for the dipoles and larger correctors for the SSS. A system called AC mole is being used extensively to measure magnetic and geometric axis, as well as roll angle, for every single magnet composing all the SSS. This paper describes its performance, its first years of operation, as well as the improvements that have made it very powerful, versatile and easy to use. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2008-1070; http://cds.cern.ch/record/1092675/files/lhc-project-report-1070.pdf;

Imported from Invenio.