Sputtering of targets in high-intensity heavy-ion beam experiments

TL;DR

This paper reviews models and experimental data on target atom sputtering in high-intensity heavy-ion experiments, especially for superheavy nuclei synthesis, highlighting the importance of target design and sputtering yield reliability.

Contribution

It provides estimates and simulations of sputtering yields in superheavy element experiments, comparing them with experimental data to assess target longevity and reliability.

Findings

Large rotating targets reduce sputtering yields effectively.

Sputtering yields are critical for low cross-section superheavy element synthesis.

Simulations align with some experimental data on actinide targets.

Abstract

Based on available models and experimental data, the sputtering of target atoms in long-term experiments with intense heavy ion (HI) beams has been considered. The experiments on the synthesis of superheavy nuclei (SHN), which are carried out in laboratories around the world, are examples of such experiments encountering the target atoms sputtering in specific conditions. Rotating wheels with a relatively large target annulus area are used in these experiments to reduce the temperature and radiation loads on the target. Large areas of rotating targets allow one to reduce the sputtering yields of target atoms significantly. The question arises about the reliability of these yields in experiments on the synthesis of SHN with Z > 118. These nuclei can be produced with extremely low cross sections, requiring HI beam doses exceeding 1020 particles passed through the target to observe several decay events of the thus synthesized SHN. Estimates based on approximations and simulations considered in this work are presented and compared with some data on actinide target sputtering obtained in experiments performed on the synthesis of SHN.