Observed proton beam induced disruption of a tungsten powder sample at CERN

Abstract

Fluidized tungsten powder has been proposed as a potential target technology for particle accelerator applications with very high power highly focused pulsed beams. This has motivated a series of experiments carried out at the HiRadMat facility at CERN to study the response of a tungsten powder sample to an impinging high energy proton beam pulse. The main observation was that of beam induced lifting of the powder sample which was recorded by high speed video. In this paper we consider three mechanisms to explain the observed powder lift including aerodynamic, thermal expansion and induced charge effects. Simulations of the aerodynamic effect revealed that this could not explain the magnitude of the observed eruptions especially during tests carried out with the powder in a vacuum. Thermal expansion of tungsten particles giving rise to the eruption seems implausible due to the propensity for the powder to absorb perturbations. We show that the observations can be explained by a Coulombic eruption of the tungsten particles. The high energy beam leaves a pattern of charge distributed in the poorly conducting powder sample, which creates an electric field that consequently results in a force acting on the individual charged particles. We calculate the charge deposited, the electric field and the resulting acceleration and show that this is a plausible mechanism for causing the observed eruptions. We believe the response of a granular conductive sample to an incident proton beam has not previously been explained.

High Power Targetry R&D and support for future generation accelerator

“…Flowing liquid metals have also been successfully used as high-power neutron-production targets [33][34][35] after significant R&D to mitigate issues such as cavitation-induced erosion damage [36][37][38][39][40][41][42]. Other novel targetry concepts being explored include a fixed granular target design, a conveyor target (being developed at Fermilab to support the Mu2e-II experiment) and a flowing granular target (possible Muon collider target) [43][44][45][46][47][48][49][50]. Significant R&D work will be needed to further develop and optimize the aforementioned novel targetry concepts to support the requirements of future experiments that are well beyond the limit of any existing target technology.…”

Beam impact tests of a prototype target for the beam dump facility at CERN: Experimental setup and preliminary analysis of the online results

“…The Beam Dump Facility conditions require slow extraction of the beam, therefore the HiRadMat facility at CERN [7] could not be used, as done for target technologies tests in the past [8][9][10][11][12][13]. The target prototype experimental setup was therefore located in the North Area target zone of CERN (TCC2), where the SPS proton beam is regularly sent under slow extraction with intensities up to 3-4·10 13 protons per pulse for physics experiments and test beams.…”