ИСТИНА

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10,000-ton steel flux-return yoke. This steel also serves as part of the muon detection system of the detector and accurate characterization of the magnetic flux density inside the steel is necessary. The flux density everywhere in the detector has been calculated, but to assess the reliability of the calculations in the steel and to measure the influence of differing permeability in various portions of the steel, it is desirable to make measurements of the flux density in the steel when the solenoid is energized. Flux loops have been installed on select segments of the steel yoke and voltages induced in these loops during fast discharge of the solenoid will be sampled and integrated to measure the change in average flux density in the steel due to the discharge. The results of laboratory studies made using model iron blocks equipped with flux loops and magnetized with a controlled power supply, are reported.