Proton beam induced dynamics of tungsten granules

This paper reports the results from single-pulse experiments of a 440 GeV/$c$ proton beam interacting with granular tungsten samples in both vacuum and helium environments. Remote high-speed photography and laser Doppler vibrometry were used to observe the effect of the beam on the sample grains. The majority of the results were derived from a trough containing $\sim 45 \mu \text{m}$ diameter spheres (not compacted) reset between experiments to maintain the same initial conditions. Experiments were also carried out on other open and contained samples for the purposes of comparison both with the $45 \mu \text{m}$ grain results and with a previous experiment carried out with sub-$250 \mu \text{m}$ mixed crystalline tungsten powder in helium [Phys. Rev. ST Accel. Beams 17, 101005 (2014)PRABFM1098-440210.1103/PhysRevSTAB.17.101005]. The experiments demonstrate that a greater dynamic response is produced in a vacuum than in a helium environment and in smaller grains compared with larger grains. The examination of the dynamics of the grains after a beam impact leads to the hypothesis that the grain response is primarily the result of a charge interaction of the proton beam with the granular medium.