A Fast Digital Integrator for Magnetic Field Measurements at Cern

Abstract

A self-calibrating digital instrument for flux measurements on magnets for accelerators used in basic research on subnuclear particles is proposed. The instrument acquires voltage arising from rotating coils transducers with a theoretical resolution of 10 ppt and a maximum sampling frequency of 800 kS/s. Then, samples are integrated on-line and suitably processed in order to improve time resolution and flux accuracy. This allows the limits of state-of-the-art digital fluximeters, related mainly to newgeneration rotating coils, with trigger rate of 20 kHz and coils speed of 10 rps, to be overcome. The instrument has been prototyped at Magnetic Measurement and Testing (MTM) Group of European Laboratory for Nuclear Research (CERN), under a framework of cooperation with the University of Sannio. Details on hardware and firmware conception, as well as on experimental results of the instrument principle validation, and of the preliminary metrological characterization of the prototype, are provided.

NbTi/Nb/Cu Multilayer Shield for the Superconducting Shield (SuShi) Septum

“…The purpose of this coil was to pick up sudden changes of the external magnetic field in case of a flux jump, measure its time difference with respect to the signals of the internal Hall sensors, and ultimately to evaluate the feasibility of this method as an early diagnostics of flux jumps, to safely abort the beam before the penetrating field has fatal consequences. The voltage measured at the two terminals of the pickup coil was measured by a fast digital integrator (FDI v3 [7]), and recorded by a computer at a sampling rate of 1 kHz.…”

Precision Analysis and Design of Rotating Coil Magnetic Measurements System

“…2020, 10, x FOR PEER REVIEW 2 of 16 than the Hall effect [4,5]. For this technique, a coil is put in a cylindrical rod called a "search coil" [6][7][8][9], and its length must be longer than the magnet, measuring more than 20% of the magnet's length. In addition to controlling the constant speed of the coil, assembling the untested devices, in terms of natural frequency, mechanical unbalance [10][11][12], misalignment [13,14], and looseness, into the structure of the instrument can lead to the problems with rotating machine which can affect the whirling of shaft containing the coil inside.…”

“…While rotating coil magnetic field measurement is also a magnetic field measurement, it is faster than the Hall effect [4,5]. For this technique, a coil is put in a cylindrical rod called a "search coil" [6][7][8][9], and its length must be longer than the magnet, measuring more than 20% of the magnet's length.…”

Digital Integrator for Fast Accurate Measurement of Magnetic Flux by Rotating Coils

“…It was provided by a dichotomic automatic procedure for calibration and correction of gain and offset errors. Details of such a procedure are reported in [8]. A field-programmable gate array acts as an input-output processor: it supervises the PGA operations at low level and provides the interface for the board bus peripheral component interface extensions for instrumentation.…”