Study of neutron unbound states using the Modular Neutron Array (MoNA)

The Modular Neutron Array (MoNA) at MSU NSCL, was conceived and built by a collaboration of primarily undergraduate schools, to perform neutron coincident experiments studying nuclear structure. The purpose, goals, setup, and results of the commissioning of MoNA utilizing the Sweeper magnet and its detectors to identify the charged particle residues in coincidence with the neutrons in MoNA are introduced. Calibration techniques are detailed along with analysis procedures. The first test experiments are presented and analyzed.; A measurement of the system resolution is made by comparing data from the one-proton knockout of 8Li to the known unbound resonance of 7He to detailed simulation of the MoNA/Sweeper setup (using a new Monte Carlo code, SIMPLE TRACK). The accuracy of the resolutions determined by calibration tests are confirmed by the final agreement with a 7He resonance at 0.425 +/- 0.02 MeV and a width of 0.18 +/- 0.04 MeV.; The absolute efficiency of the MoNA detector setup is determined from a Coulomb breakup experiment of 11Be. This reaction is chosen because the decay energy and the cross section can be calculated through both the virtual photon method and the continuum discretized coupled channels method. The data agree very well with the calculated decay curves and the total system efficiency is determined. MoNA's absolute efficiency is deduced to be 73 +/- 6% for 90 MeV neutrons. This is above the original design goal and agrees with MoNA GEANT simulations.; The first two physics experiments for the MoNA/Sweeper system are presented. The first is a measurement of the one-neutron knockout cross section from 10Be to the ground state of 9Be. Because 9Be has no bound excited states the observance of 9Be in the Sweeper focal place detectors uniquely determines the reaction channel. The reduction factor the 0p3/2 single particle spectroscopic factor in 10Be is determined to be 0.66 +/- 0.07. The results are compared to other spectroscopic factors near the same Delta S (neutron minus proton separation energies).; The second experiment concerns the population of different paired-neutron wave functions in the ground state of 12Be ((1s 1/2)2, (0p1/2)2 and, (0d5/2)2). The relative cross section to the different single particle states in 11Be can be used to determine relative admixture abundance of the corresponding neutron-pair wave function in 12Be above a 10Be core. The relative cross section to the unbound 5/2+ in 11Be is measured by a neutron knockout reaction using MoNA. The decay energy curve for the current study confirms the reported results of the previous measurements. Differences in the decay energy spectrum with previous measurements concerning the cross section to populate the 10Be 2+ state are noted and likely due to limited efficiencies at forward angels for the previous work.; Finally, a discussion of MoNA's capabilities is presented and experiments completed to date are summarized. Plans for the future of MoNA are also introduced. MoNA analysis and calibration guides are included in the appendices.