Mechanical design of the superconducting solenoid package for the saraf-linac project

Abstract The Soreq Applied Research Accelerator Facility (SARAF) in Israel will provide an intense source of fast neutrons and radioactive nuclei for neutron applications, to explore rare nuclear reactions and produce new types of radiopharmaceuticals for nuclear medicine. CEA Paris-Saclay is in charge of the design, construction and commissioning of this superconducting linear particle accelerator (linac) to produce the first particle beams in 2022. The superconducting linac is part of the SARAF accelerator and it will be equipped with twenty identical solenoid packages arranged in four 5-metre long cryomodules; they are located between the cavities and they ensure the beam control. The solenoid package is a complex mechanical system and it is designed to operate at cryogenic temperatures. It comprises the main solenoid coil with an integrated square flux density of 3.5 T2 m , two lateral shielding coils to reduce the fringe fields on the cavities as well as two pairs of steering coils. This ensemble is enclosed in a stainless steel helium vessel. In this study, we present the mechanical design of the first prototype of the solenoid package with a particular focus on the main coil, whereby the superconducting wire (Nb–Ti/Cu) is wound and cured on two extremity flanges made of epoxy reinforced with glass cloth (G-10). The modelling of the solenoid components is carried out using Finite Element Analysis (FEA) and the results of simulations are used to assess the structural integrity of the components. Moreover, an extensive literature review is conducted to collect the mechanical properties at cryogenic temperature of the composite materials used for the construction. Finally, the results of the experimental validation of the first solenoid prototype are presented. The experimental campaign is carried out using a cryostat designed on purpose to reproduce both the final operating temperature and magnetic field.