Division of systems engineering

A 16 kW proton beam was delivered by SPIRAL2's LINAC at the end of November 2020. This represents 10% of the machine's maximum proton power and marks an important milestone for the project. The ramp-up was done progressively, according to a 4-phase plan to control risks and validate the beam accelerator (Figure 2). The first two phases were carried out in 2019 with a very low intensity beam, in order not to damage the machine in case of loss of particles (see milestone).

Since the return to activity at the exit of the first shutdown in 2020, great efforts have been made by the teams in order to start a gradual increase in beam current up to its nominal peak intensity. Numerous machine studies have made it possible to resolve one by one the various difficulties inherent in the operation of a machine of such power. On October 10, 2020, a 4.8 mA beam was accelerated, representing the end of phase 3 of the ramp-up in compliance with the operating rules of an INB (basic nuclear installation). It demonstrates the control of the full beam intensity.

On November 18, a beam with a power of 16 kW was accelerated to the accelerator's main beam stop (Figure 3). It demonstrates the control of the extremely low beam loss level of less than ten watts throughout the machine. This loss control was made possible thanks to a very good understanding of the physics of acceleration, the result of numerous simulations and error calculations, and by the optimization of several advanced techniques such as the adjustment of the RF wave injection servo-controls during the beam passage or the use of advanced functions such as the "feedforward" of the cavities, developed by the DIS within the LLRF (Low Level Radio Frequency) control electronics that this laboratory has developed. It should be noted that during all these phases, the GANIL has been able to rely on the RF (Radio Frequency) expertise of the DACM in particular during cavity conditioning as well as on active support in beam optics in particular concerning the improvement of the theoretical model of the machine based on the DACM simulation tools.