Speaker
Description
At the RIKEN Nishina Center, multilayer graphene (MG) and graphite sheets (GS) manufactured by Kaneka Corporation [1] are employed as charge strippers, enabling the stable delivery of high-intensity beams [2]. Thin carbon foils are also utilized as backing foils for targets in superheavy element search experiments, where they are typically fabricated by arc discharge or magnetron sputtering methods.
In recent years, target materials for superheavy element searches have become extremely costly, available only in limited quantities. The electrodeposition method [3,4] offers an effective means of bonding expensive target material onto metal backing foils. However, this method involves aqueous solutions, rendering it incompatible with conventional carbon foils, which are prone to cracking when dry, deforming upon absorbing water, and disintegrating in organic solvents.
It is well established that carbon backing foils extend target lifetimes compared to their metallic counterparts. We therefore pursued the development of MG-based backing foils capable of withstanding the solutions used in electrodeposition, much like metal foils. This effort posed a significant challenge due to the inherently low surface wettability of MG and GS, which results in poor adhesion to other materials. Nonetheless, we have successfully fabricated MG backing foils exhibiting good adhesion to the target material. In this contribution, we present the development process.
[1] A. Tatami et al., AIP Conference Proceedings 1962, 030005 (2018).
[2] H. Hasebe et al., EPJ Web Conf. 229 (2020) 01004.
[3] W. Parker, R. Falk, Nucl. Instr. And Meth. 16, 355-357 (1962)
[4] Y. Kudou et al., RIKEN Accel. Prog. Rep. 42, 265 (2009).