| Published Articles | |
| Title | First observation of spalling in tantalum at high temperatures induced by high energy proton beam impacts |
| Author(s) | Torregrosa Martin, Claudio (CERN) ; Solieri, Nicola (CERN) ; Fornasiere, Elvis (CERN ; Ecole Polytechnique, Lausanne) ; Busom Descarrega, Josep (CERN) ; Calviani, Marco (CERN) ; Canhoto Espadanal, Joao (CERN) ; Perillo-Marcone, Antonio (CERN) ; Spätig, Philippe (Ecole Polytechnique, Lausanne ; PSI, Villigen) |
| Publication | 2021 |
| Number of pages | 16 |
| In: | European Journal of Mechanics - A/Solids 85 (2021) 104149 |
| DOI | 10.1016/j.euromechsol.2020.104149 |
| Subject category | Accelerators and Storage Rings ; Detectors and Experimental Techniques |
| Abstract | Spalling in tantalum has been observed in an experiment aiming at testing an antiproton production target prototype at CERN’s HiRadMat Facility. The experiment consisted in impacting 47 intense and high-energy proton beams onto a target equipped with ten cylindrical cores made of tantalum of Ø8 mm by 16 mm. Each of these proton beam impacts induced a sudden rise of temperature in the bulk of the Ta cores around 1800 °C in 0.9 s leading to the excitation of a vibration mode which exposed their material to compressive-to-tensile pressures ranging from 2 GPa to 9 GPa, with pressure rates up to 20 GPa/s. Post-irradiation analyses such as neutron tomography and metallographic examination of the cores, revealed the creation of voids in the bulk of the tantalum cores ranging from to 2 m to 1 mm in diameter. These voids present a non-uniform size and density distribution within the cores, with limited growth and coalescence in areas subjected to higher temperatures and tensile pressures. Grain-growth due to a fast, thermally-induced, recrystallization has been also observed in some zones. In this work, we present a detailed characterization of the unique thermal and mechanical load that has induced this spall process by means of Finite Element and hydrocode simulations, together with post-experiment microscope and EBSD observations of the Ta rods. This analysis suggests that spall-induced void growth and coalescence is enhanced in the temperature and pressure window of 1300-1800 °C and 3-6.5 GPa, whereas is restrained at temperatures and tensile pressures above 2000 °C and 6.5 GPa. In addition, the analysis suggests that full thermal-recrystallization in tantalum can take place when exposed to temperatures above 2000 °C for less than 2 s. Four different hypotheses to explain the observed void size distribution trends are presented. |
| Copyright/License | © 2020 The Authors (License: CC-BY-4.0) |
Zapis kreiran 2020-11-13, zadnja izmjena 2021-10-11
