Fabrication and Test Results of the First 2 m Model Magnet of Beam Separation Dipole for the HL-LHC Upgrade

The large aperture superconducting beam separation dipole (D1) must be developed as part of the high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN. The most important specifications of the D1 are a coil aperture of 150 mm and field integral of 35 T·m at 12.0 kA and 1.9 K. The technical challenges of this magnet include predicting the changes in the size of the coils during fabrication, achieving a high radiation resistance, and management of the iron saturation. KEK is in charge of developing the D1. After conducting a series of design studies, a design consisting of a single-layer coil based on Nb-Ti technology with a collared yoke structure was selected. The fabrication of the first 2 m model of the D1 started at KEK in 2015. Newly developed radiation resistant glass-fiber-reinforced-plastics were utilized as coil parts in the accelerator magnets for the first time. The 2 m model was subjected to two cycles of cold test in the vertical cryostat at KEK. In this paper, we report on the fabrication of the 2 m model. We also present and discuss the quench test results from the perspective of the coil prestress.