Periodic Reporting for period 1 - BeLaPEx (Beta-decay studies with laser-polarised beams of exotic nuclei)
Reporting period: 2022-02-01 to 2024-01-31
The first European station for beta-decay spectroscopy with laser-polarised beams of radioactive nuclei has been developed at CERN’s nuclear physics facility ISOLDE. The new setup creates unique opportunities for studies of very neutron-rich nuclei, often called exotic, which are extremely unstable due to a large surplus of neutrons. Experimental exploration of these exotic nuclei helps us understand the building blocks of the world around and the nuclear reactions that happen in the plethora of cosmic events where a dense neutron flux is present.
The experimental investigation of very neutron-rich nuclei emitting neutrons following their decay was a major focus of the BeLaPEx project. The aim was to gain insight into the mechanism of beta-delayed neutron emission, which is the primary decay mode of exotic nuclei involved in one of the astrophysical processes responsible for the formation of about half of the chemical elements heavier than iron.
The overall strategy of the project was aimed at three main objectives: 1) developing the new beta-decay spectroscopy station dedicated to measurements with laser-polarised beams of very neutron-rich nuclei, 2) applying and extending the novel experimental technique that utilises anisotropic emission of radiation from spin-polarised nuclei to unambiguously assign spins and parities of nuclear states, and 3) utilising the full potential of the new setup, which allows for coincidence measurements of radiation emitted from spin-oriented nuclei, and 4) launching a unique research program at ISOLDE.
The experimental investigation of very neutron-rich nuclei emitting neutrons following their decay was a major focus of the BeLaPEx project. The aim was to gain insight into the mechanism of beta-delayed neutron emission, which is the primary decay mode of exotic nuclei involved in one of the astrophysical processes responsible for the formation of about half of the chemical elements heavier than iron.
The overall strategy of the project was aimed at three main objectives: 1) developing the new beta-decay spectroscopy station dedicated to measurements with laser-polarised beams of very neutron-rich nuclei, 2) applying and extending the novel experimental technique that utilises anisotropic emission of radiation from spin-polarised nuclei to unambiguously assign spins and parities of nuclear states, and 3) utilising the full potential of the new setup, which allows for coincidence measurements of radiation emitted from spin-oriented nuclei, and 4) launching a unique research program at ISOLDE.
Research activities included conception, design, construction, installation, commissioning, and upgrades of the rst European station for beta-decay spectroscopy with laser-polarised beams of radioactive nuclei. The new experimental setup was integrated with the VITO beamline, where the ion beam from ISOLDE is overlapped with a laser beam to induce spin polarisation. The new station, called DeVITO, enables coincidence measurements of radiation emitted from spin-oriented nuclei. The detection system is tailored for beta-decay studies of very neutron-rich nuclei. In particular, it allows us to determine the beta-decay asymmetry for excited states populated in the nuclear decay products.
The new setup developed at VITO enables to adopt and extend the novel approach to beta-decay experiments that overcomes some inherent limitations of conventional beta-decay measurements, particularly the limited ability to assign spins and parities of nuclear states. The key advancement is the use of spin-polarised beams of beta-decaying nuclei that allows us to benefit simultaneously from two essential features of the nuclear beta decay, that is, from high angular-momentum-selectivity of beta transitions and the parity non-conserving nature of the weak interaction. Resultantly, these advanced experimental capabilities pave the way towards a rmly founded discussion of exciting nuclear structure phenomena that occur in exotic nuclei. Experiments performed at the DeVITO station will provide experimental data that are crucial for the verification and guidance of theoretical models describing beta-delayed neutron emission.
The new setup for beta-decay spectroscopy at ISOLDE allows various end-station congurations and a diverse research programme concerning aspects of nuclear structure, weak interaction studies, astrophysics, and nuclear reactor applications.
The new setup for beta-decay spectroscopy at ISOLDE allows various end-station congurations and a diverse research programme concerning aspects of nuclear structure, weak interaction studies, astrophysics, and nuclear reactor applications.