The location of the quench development in modern superconducting magnets is one of the
key information to be retrieved during a powering test to evaluate possible limitations
or instabilities. The most common technologies used to locate the state transition are
the voltage taps and the quench antenna, thanks to their reliability and accuracy.
However, during the production phase of a magnet, the number of voltage taps is commonly
reduced to simplify the construction process and quench antennas are generally used only
for dipoles or quadrupoles to limit the antenna design complexity. A new method for the
quench localization has been optimized and applied to the High Order Corrector Magnets
for the HL-LHC upgrade project during the series production. After the magnet discharge,
the position of the quenched coil/coils can be retrieved considering the effect of the
still magnetized superconductors on the total magnetic field harmonics, measured using
standard techniques. From the comparison of the predicted quenched coil position and the
measurements of the HO series power tests, this method of quench localization proves
to be a powerful tool to improve diagnostic technologies for the development of modern
superconducting magnets.