Search for α-condensed state in ²⁰Ne – 1

Alpha particle clustering is an important phenomenon in light nuclei. On the basis of the Ikeda diagram, the α cluster structure has been predicted to emerge near the α-decay threshold energy. The 0⁺₂ state at E_x = 7.65 MeV in ¹²C, which is located higher than the 3α-decay threshold by 0.39 MeV, is a well-known 3α cluster state. This state is considered to be theα-condensed state (ACS) where the three α clusters are condensed into the lowest orbit. Similar ACSs are theoretically expected in heavier nuclei but have never been experimentally established.

The ACSs are expected to decay by emitting low-energy α particles, therefore, we searched for the ACS in ²⁰Ne by measuring inelastic α scattering at forward angles including 0°and subsequent particle decays. For the decay particle measurement, we used 6 sets of Si detector array, and each array consists of three Si detectors. Because energies of decay α particles are low, it is difficult to measure these particles using the conventional ²⁰Ne gas target with several-μm-thick organic membranes as the gas sealing windows. So, we used 100-nm-thick Silicon Nitride membranes.

In the present talk, we will report the experimental details focusing on the ²⁰Ne gas target with ultra-thin gas sealing windows and the Si detector arrays.