Assembly and Tests of SQ02, a Nb 3Sn Racetrack Quadrupole Magnet for LARP

The US LHC Accelerator Research Program (LARP) is developing accelerator magnets for a possible LHC luminosity upgrade. As part of the LARP supporting R&D, a subscale racetrack quadrupole magnet (SQ) has been developed in order to provide a cost effective tool for technology development studies. The first magnet (SQO₁), reported earlier, was tested as a proof-of-principle model that applied for the first time LBNL shell-based loading structure to racetrack coils in a quadrupole configuration. The new loading structure, pre-loaded with water-pressurized bladders and keys, provided predictable and controllable pre-stress to four subscale racetrack coils, both in the end region and across the straight section. A second magnet (SQO₂) has been recently completed, with the goal of assessing the conductor performance and the influence of the coil axial support on training. SQO₂ implements four new coils wound around aluminum bronze islands and instrumented with voltage taps and spot heaters, in order to monitor quench locations and propagation velocities. This paper reports the SQO₂ test results, including magnet quench performance with respect to short sample expectations, training history, and quench locations.