New magnetic shielding for ECAL

Electromagnetic calorimeter ECAL will operate in about 3 Gauss magnetic field. Used photomultipliers are very sensitive to magnetic field of even less than 1 Gauss and thus magnetic shielding is a needed component of the detector.

Due to sudden shortfall in supplies of originally designed magnetic shielding from partner institution, a new type had to be quickly developed and tested in house. Samples from dedicated Mu-metal sheet (80% Ni alloy) were manufactured to desired shape and passed tests in dipole magnet at cyclotron in Řež. Micro-welding machine was constructed to be able to produce the shielding in big series. Based on the successful tests of the first prototype as well as final design, mass production was started at the beginning of December 2016. From first prototype to mass production it took less than two months including order of dedicated material.