New geometry of wide-aperture quadrupole magnets for plasma experiments in the FAIR project

The experiments on matter under extreme conditions of density and temperature which are proposed by the HED@FAIR plasma physics collaboration at the new accelerator facility FAIR in Darmstadt, Germany require a strong final focusing system for energetic heavy ion beams. The main components of this system are four wide-aperture quadrupoles which have to provide a millimeter-size focal spot at the target. These superconducting magnets have 33 T/m central gradient with the inner aperture diameter of 240 mm and the magnetic length of 2 m. While designing the magnets, it has turned out that the magnet’s aperture shall be increased to 260 mm, and the design distance between the magnet’s centers of 2.5 m cannot be kept. Therefore it was necessary to reduce the physical length of the magnets and correspondingly, to compensate the integral field gradient by increasing the current. New requirements led to the development of a new magnets geometry which is presented along with parameters of the correction system and considerations about the magnet’s cooling system.