The power tests of the D2 prototype were completed in May. This is the first full-size recombination dipole giving 4.5 T over a 7.8 m magnetic length, manufactured at ASG under the helm of INFN Genova.

The magnet was received at CERN in March 2022 and integrated into the 14-m-long cold mass including two MCBRD correctors, namely the prototype MCBRDP1 made at CERN in building 927, and the prototype MCBRDP2 made at WST as part of the IHEP in-kind contribution.

The test started in October 2022, with the nominal current reached without quenches and the ultimate current reached with one training quench (see figure). During the second powering, the magnet reached the ultimate current without further training; at 4.5 K the magnet quenched above the nominal current. After observing a loss of preload during the second powering, we decided to perform another thermal cycle to better assess the performance. During the third powering tests, the magnet reached again ultimate current at 1.9 K without retraining and showed no further loss of preload. At 4.5 K ultimate current was reached without quenches, corresponding to 96% of the short sample limit.

During the power test, the main magnet D2 was also ramped simultaneously with one of the correctors to nominal current. The second corrector had a short coil-to-ground, located by the ELQA team in the central voltage tap and, for this reason, was not powered.

The cold mass will be disassembled to recover the two correctors in the coming months. Although the prototype met the requirements, it will not be used for installation in the HL-LHC. The first series D2 magnet is being manufactured at ASG, and shall be completed by the end of the summer.

By Ezio Todesco, WP3 Leader.