Analysis of Eddy Current Distributions in the CMS Magnet Yoke During the Solenoid Discharge

TL;DR

This paper measures magnetic flux density in the CMS detector's steel yoke during solenoid discharge by analyzing voltages in flux loops, estimating eddy currents through simulations, and reporting the results.

Contribution

It provides the first detailed calculation and analysis of eddy current distributions in the CMS magnet yoke during solenoid discharge.

Findings

Eddy current distributions were successfully calculated using ELEKTRA.

The measurements achieved a few percent accuracy in flux density estimation.

The study offers insights into the impact of eddy currents on magnetic field measurements.

Abstract

Flux loops have been installed on selected segments of the magnetic flux return yoke of the 4 T superconducting coil of the Compact Muon Solenoid (CMS) detector under construction at CERN. Voltages induced in the loops during discharge of the solenoid will be sampled online during the entire discharge and integrated offline to provide a measurement of the initial magnetic flux density in steel at the maximum field to an accuracy of a few percent. Although the discharge of the solenoid is rather slow (190 s time constant), the influence of eddy currents induced in the yoke elements should be estimated. The calculation of eddy currents is performed with Vector Fields' program ELEKTRA. The results of the calculations are reported.