Background: Theoretical calculations have shown that the energy and angular correlations in the three-body decay of the two-neutron unbound O26 can provide information on the ground-state wave function, which has been predicted to have a dineutron co
nfiguration and 2n halo structure. Purpose: To use the experimentally measured three-body correlations to gain insight into the properties of O26, including the decay mechanism and ground-state resonance energy. Method: O26 was produced in a one-proton knockout reaction from F27 and the O24+n+n decay products were measured using the MoNA-Sweeper setup. The three-body correlations from the O26 ground-state resonance decay were extracted. The experimental results were compared to Monte Carlo simulations in which the resonance energy and decay mechanism were varied. Results: The measured three-body correlations were well reproduced by the Monte Carlo simulations but were not sensitive to the decay mechanism due to the experimental resolutions. However, the three-body correlations were found to be sensitive to the resonance energy of O26. A 1{sigma} upper limit of 53 keV was extracted for the ground-state resonance energy of O26. Conclusions: Future attempts to measure the three-body correlations from the ground-state decay of O26 will be very challenging due to the need for a precise measurement of the O24 momentum at the reaction point in the target.
The DRAGON recoil mass separator at TRIUMF exists to study radiative proton and alpha capture reactions, which are important in a variety of astrophysical scenarios. DRAGON experiments require a data acquisition system that can be triggered on either
reaction product ($gamma$ ray or heavy ion), with the additional requirement of being able to promptly recognize coincidence events in an online environment. To this end, we have designed and implemented a new data acquisition system for DRAGON which consists of two independently triggered readouts. Events from both systems are recorded with timestamps from a $20$ MHz clock that are used to tag coincidences in the earliest possible stage of the data analysis. Here we report on the design, implementation, and commissioning of the new DRAGON data acquisition system, including the hardware, trigger logic, coincidence reconstruction algorithm, and live time considerations. We also discuss the results of an experiment commissioning the new system, which measured the strength of the $E_{text{c}.text{m}.} = 1113$ keV resonance in the $^{20}$Ne$left(p, gamma right)^{21}$Na radiative proton capture reaction.
The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure the free neutrons and heavy charged particles from the radioactive ion beam induced 32Mg + 9Be reaction. The fragmentation reaction was simulated with the Constrained Molec
ular Dynamics model(CoMD), which demonstrated that the <N/Z> of the heavy fragments and free neutron multiplicities were observables sensitive to the density dependence of the symmetry energy at sub-saturation densities. Through comparison of these simulations with the experimental data constraints on the density dependence of the symmetry energy were extracted. The advantage of radioactive ion beams as a probe of the symmetry energy is demonstrated through examination of CoMD calculations for stable and radioactive beam induced reactions.
The ground state of $^{28}$F has been observed as an unbound resonance $2underline{2}0$ keV above the ground state of $^{27}$F. Comparison of this result with USDA/USDB shell model predictions leads to the conclusion that the $^{28}$F ground state is
primarily dominated by $sd$-shell configurations. Here we present a detailed report on the experiment in which the ground state resonance of $^{28}$F was first observed. Additionally, we report the first observation of a neutron-unbound excited state in $^{27}$F at an excitation energy of $25underline{0}0 (2underline{2}0)$ keV.
The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound $^{28}textrm{F},$ determined to be a resonance in the $^{27}textrm{F} + n$ continuum at $2underline{2}0 (underline{5
}0)$ keV. States in $^{28}textrm{F}$ were populated by the reactions of a 62 MeV/u $^{29}textrm{Ne}$ beam impinging on a 288 $textrm{mg/cm}^2$ beryllium target. The measured $^{28}textrm{F}$ ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that $pf$ shell intruder configurations play only a small role in the ground state structure of $^{28}textrm{F}$ and establishing a low-$Z$ boundary of the island of inversion for N=19 isotones.
