Lifetime measurement of Ne-31,32

Abstract

Beta-decay half-lives of two very neutron-rich nuclei Ne-31,32 have been measured for the first time. The secondary beams of neutron-rich nuclei were produced by the projectile-like fragmentation of (40)Ar(17+) beam. Very neutron-rich nuclei in Z which is greater than or equal to 9 and is less than or equal to 11, were separated by means of the RIKEN (Institute of Physical and Chemical Research) Projectile fragment Separator (RIPS). The identification of the fragments was carried out by means of measurement of Time-Of-Flight (TOF) and energy deposit (capital delta-E). At the final focal point F3, all the detectors were mounted: a 1 mm thick Plastic scintillation counter (PL), two 0.5 mm surface barrier type silicon detectors, three lithium drift type silicon detectors, and a 2 mm thick plastic scintillation veto counter. The TOF of fragments between the production target and F3 was obtained from the PL timing and RF signal of the cyclotron. The capital delta-E of heavy ion was obtained from the first two silicon detectors. The last three Li-drift type silicon detectors allowed to perform the beta-ray detection. The efficiency of the beta-ray detection achieved to 75 percent. The half-lives of other neutron-rich isotopes F-27,29, Ne-29,30 and Na-32,33 were reexamined.

中性子に富んだ2つの核Ne-31,32のβ崩壊半減期を初めて測定した。中性子に富んだ核の2次ビームは(40)Ar(17+)ビームの入射核型破砕によって生成した。9≦Z≦11の中性子に富んだ核は理化学研究所入射核破片分離器(RIPS)を使って分離した。飛行時間(TOF)とエネルギー損失(ΔE)から破砕片を同定した。最後の焦点F3に全ての検出器、厚さ1mmのプラスチックシンチレータ(PL)1つと0.5mmの表面障壁型シリコン検出器2つとLiドリフト型シリコン検出器3つおよび厚さ2mmのプラスチックシンチレーションベトカウンタを設置した。生成標的とF3の間での破片のTOFはシンクロトロンのラジオ波信号とPLタイミングから求めた。重イオンのΔEは初めの2つのシリコン検出器から求めた。Liドリフト型シリコン検出器によってβ線を検出した。β線の検出効率は75%を達成した。中性子に富んだ他の同位核として、F-27,29、Ne-29,30およびNa-31,32,33の半減期も再測定した。