Yttrium Oxide Freeze-Casts: Target Materials for Radioactive Ion Beams.

Eva Kröll,Juliana Schell,Jochen Ballof,Sebastian Rothe,Doru C Lupascu,Simon Stegemann,Miriana Vadalà

doi:10.3390/ma14112864

Eva Kröll, Juliana Schell + Show 5 more

Open Access

https://doi.org/10.3390/ma14112864

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Abstract

Highly porous yttrium oxide is fabricated as ion beam target material in order to produce radioactive ion beams via the Isotope Separation On Line (ISOL) method. Freeze casting allows the formation of an aligned pore structure in these target materials to improve the isotope release. Aqueous suspensions containing a solid loading of 10, 15, and 20 vol% were solidified with a unidirectional freeze-casting setup. The pore size and pore structure of the yttrium oxide freeze-casts are highly affected by the amount of solid loading. The porosity ranges from 72 to 84% and the crosslinking between the aligned channels increases with increasing solid loading. Thermal aging of the final target materials shows that an operation temperature of 1400 °C for 96 h has no significant effect on the microstructure. Thermo-mechanical calculation results, based on a FLUKA simulation, are compared to measured compressive strength and forecast the mechanical integrity of the target materials during operation. Even though they were developed for the particular purpose of the production of short-lived radioactive isotopes, the yttria freeze-cast scaffolds can serve multiple other purposes, such as catalyst support frameworks or high-temperature fume filters.

Highlights

IntroductionISOLDE [1] is a radioactive ion beam (RIB) facility, located at the Proton Synchrotron
The ISOLDE targets are placed in a resistively heated tantalum furnace connected to an ion source in a vacuum vessel bombarded with a high-energy proton beam of 1.4 GeV, delivered from the Proton SynchrotronBooster (PSB) accelerator
This study demonstrates that the fabrication of anisotropic yttrium oxide scaffolds by unidirectional solidification is feasible

Summary

Introduction

ISOLDE [1] is a radioactive ion beam (RIB) facility, located at the Proton Synchrotron. The ISOLDE targets are placed in a resistively heated tantalum furnace connected to an ion source in a vacuum vessel (target and ion source unit) bombarded with a high-energy proton beam of 1.4 GeV, delivered from the PSB accelerator. By heating the target to high temperatures (maximum temperatures range up to 2000 ◦ C) the released isotopes move through the target matrix to its surface, from which they are desorbed, followed by effusion to the ion sources, where they are charged to form typically singly charged positive ions. An extraction potential accelerates the ions to energies up to 60 keV, which allows them to be transferred via a dipole mass separator magnet (see Figure 1), selecting an isobar, and to the research beam lines distributed in the ISOLDE hall [2]

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