First experiment at TASCA towards X-ray fingerprinting of element 115 decay chains

115番元素崩壊連鎖のX線同定に向けたTASCAにおける最初の実験

Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Jeppsson, J.*; Rudolph, D.*; Andersson, L.-L.*; Ackermann, D.*; 浅井 雅人  ; Block, M.*; Eberhardt, K.*; Even, J.*; Dllmann, Ch. E.*; Dvorak, J.*; Gates, J. M.*; Gregorich, K. E.*; Herzberg, R.-D.*; Heberger, F. P.*; Jger, E.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kratz, J. V.*; Krier, J.*; Kurz, N.*; Lahiri, S.*; Lommel, B.*; Maiti, M.*; Merchn, E.*; Omtvedt, J. P.*; Parr, E.*; Runke, J.*; Schaffner, H.*; Schdel, M.; Yakushev, A.*

Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Jeppsson, J.*; Rudolph, D.*; Andersson, L.-L.*; Ackermann, D.*; Asai, Masato; Block, M.*; Eberhardt, K.*; Even, J.*; Dllmann, Ch. E.*; Dvorak, J.*; Gates, J. M.*; Gregorich, K. E.*; Herzberg, R.-D.*; Heberger, F. P.*; Jger, E.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kratz, J. V.*; Krier, J.*; Kurz, N.*; Lahiri, S.*; Lommel, B.*; Maiti, M.*; Merchn, E.*; Omtvedt, J. P.*; Parr, E.*; Runke, J.*; Schaffner, H.*; Schdel, M.; Yakushev, A.*

Caビームとアクチノイド標的を用いて合成される超重元素の原子番号と質量数は、実験的に直接決定されておらず、新元素同定という意味では疑念が残る。本研究は、それらの超重元素の原子番号を特性X線の観測により直接同定することを目的とする。超重元素の合成と分離には、ドイツ重イオン研究所のガス充填型反跳核分離装置TASCAを用い、その焦点面に高効率の--electron同時計数測定装置を構築した。反跳核の輸送効率と収束性を実測し、シミュレーションと比較した。115番元素のX線測定を実現するのに十分な性能を達成した。

The atomic numbers and mass numbers of superheavy elements produced in the reactions of Ca beam with actinide targets have not been identified with direct experimental evidences. This causes a little doubt about a new element synthesis. The aim of this study is to identify the atomic numbers of those superheavy elements through characteristic X-ray measurements. To produce and separate superheavy elements, we employed a gas-filled separator TASCA at GSI, and constructed high-efficiency --electron multi-coincidence detector setup at the focal plane of TASCA. Transmission efficiencies and focusing abilities were tested experimentally, and compared with simulations. We achieved a good performance to realize X-ray measurement for the element 115.