Impact force measurements of solid cryogenic pellets for Disruption Mitigation Systems

The shattering of cryogenic pellets is a key method for disruption mitigation in magnetic confinement fusion devices. A dedicated Hopkinson bar test bench has been developed and qualified for the measurement of impact forces generated by solid cryogenic projectiles under impact loading conditions relevant to ITER’s Disruption Mitigation System. The experimental methodology, including automated pellet fabrication, acceleration, impact alignment and force measurement, was validated through a reproducible campaign of sixteen impact tests. Elastic wave dispersion in the Hopkinson bar was analysed and corrected using frequency-domain phase-shift compensation, enabling reliable reconstruction of force–time histories. Measurements performed on different cryogenic solids over a range of impact energies show a linear dependence of the peak impact force on the projectile kinetic energy. The qualified test bench and the observed scaling law provide a robust experimental basis for the characterisation and modelling of cryogenic pellet fragmentation processes.