C(α,α') with the MAIKo active target*

In the present talk, we will report the measurement of ¹⁰C(α,α') reaction  at 75 MeV/u using the MAIKo active target to search for alpha cluster structures in unstable ¹⁰C nuclei.

Alpha cluster structure have beem widely examined among Z=N=2n self-cojugate nuclei. When excess nucleons are added to such nuclei, these nucleons occupy the molecular orbitals between the alpha cores and exhibit new variety of molecular structures.

In addition, recent theoretical study predicts that the comparison between the isobaric analog states will unveil the inner structures of cluster states [1]. Therefore, we proposed to investigate alpha cluster structures in ¹⁰C which is the mirror nucleus of ¹⁰Be.

Measurement of monopole strengths is a usuful method to search for alpha cluster structures [2]. Missing mass spectroscopy of alpha inelastic scattering, which has been successfully applied among stable nuclei to measure monopole strengths, should be perfoemed for  unstable ¹⁰C. However, such a measurement requires the detection of low-energy (~1 MeV) recoil alpha particles which is not possible with a normal setup.

To realize the detection of low-energy recoil particles, we have developed a new active target system MAIKo at RCNP. The system consists of a time projection chamber (TPC) in which the detection medeum is used also for the target gas. Since the reaction occurs inside the detector, the detection threshold can be lowered. In MAIKo, we utilize the micro-pixel chamber (μ-PIC) to multiply and detect the drift electrons. μ-PIC is one type of micro-pattern gaseous detectors which is developed at Kyoto University.

[1] M. Ito, EPJ web of Conferences 117, 06014 (2016).

[2] T. Kawabata et al., Physics Letters B 646, 6 (2007).