Uncertainty Reduction Via Parameter Design of A Fast Digital Integrator for Magnetic Field Measurement

At European Centre of Nuclear Research (CERN), within the new Large Hadron Collider (LHC) project, measurements of magnetic flux with uncertainty of 10 ppm at a few of decades of Hz for several minutes are required. With this aim, a new Fast Digital Integrator (FDI) has been developed in cooperation with University of Sannio, Italy [1]. This paper deals with the final design tuning for achieving target uncertainty by means of experimental statistical parameter design

Performance of the Room Temperature Systems for Magnetic Field Measurements of the LHC Superconducting Magnets

The LHC will be composed of 1232 horizontally curved, 15-meter long, superconducting dipole assemblies and 474 Short Straight Sections containing various types of quadrupoles. These magnets are manufactured by several European companies and half of them are currently produced. The field quality at room temperature is strictly monitored to guide and validate the assembly at different stages of the production in the industry. Dipoles and quadrupoles are measured with two different rotating coil systems. These âﾜmolesâ travel inside the 50 mm aperture and accurately measure the field and gradient strength integrated over the length, the field direction and high order harmonics. We describe here these two systems, their performance and the experience gained through the two first years of operation

A Fast Digital Integrator for Magnetic Field Measurements at CERN

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

Measurement of the inductance of resistive magnets: two case studies

This note concerns the main definitions of self-inductance (i.e. differential, secant and energy-based) that are relevant for the electromagnetic modelling of accelerator magnets. In particular, we consider the case of iron-dominated resistive magnets. The different definitions, which coincide in the linear limit at low field, tend to diverge dramatically as the iron becomes saturated. We describe the measurement technique and the results for two case studies, i.e. the PS MTE octupole and a main SPS dipole of MBB type. We show that the differential inductance may drop dramatically at high current, up to about a factor two, even for magnets where the field non linearity is within a few percent only

Measurements of noise on the PS B-train’s B-dot signal

This note reports the results of a series of magnetic field measurements carried out in the PS reference magnet U101 in February 2011, aimed at investigating the source of an abnormally high noise on the B-dot signal noticed by operation. Results indicate that the noise can be ascribed to actual field perturbations which may be traced back to power converter ripple. Due to the filtering effect of the magnet, however, the perturbations are very small i.e. generally less than 0.1 G above 1 kHz, which is unlikely to represent a serious beam disturbance

Magnetic measurements of a CEA/IPHI 28.5° dipole for the Linac4 diagnostic beam line

This reports summarizes the results of a recent test campaign carried out on a spectrometer dipole for the Linac4 diagnostic line. These results include point-like measurements done with NMR and Hall effect probes and are intended as a cross-check of a more extensive campaign carried out at Sigma Phi. They are aimed specifically at the issue of the reproducibility of the field on different cycling conditions. In the Appendix, a field control algorithm which can be used to guarantee the requested 0.1% reproducibility is spelled out in full detail