Three-body correlations for the ground-state decay of the lightest two-proton emitter 6 Be are studied both theoretically and experimentally. Theoretical studies are performed in a three-body hyperspherical-harmonics cluster model. In the experimental studies, the ground state of 6 Be was formed following the α decay of a 10 C beam inelastically excited through interactions with Be and C targets. Excellent agreement between theory and experiment is obtained demonstrating the existence of complicated correlation patterns which can elucidate the structure of 6 Be and, possibly, of the A=6 isobar.

In this paper, we present results of initial measurements and calculations of prompt gamma ray spectra (produced by proton-nucleus interactions) emitted from tissue equivalent phantoms during irradiations with proton beams. Measurements of prompt gamma ray spectra were made using a high-purity germanium detector shielded either with lead (passive shielding), or a Compton suppression system (active shielding). Calculations of the spectra were performed using a model of both the passive and active shielding experimental setups developed using the Geant4 Monte Carlo toolkit. From the measured spectra it was shown that it is possible to distinguish the characteristic emission lines from the major elemental constituent atoms (C, O, Ca) in the irradiated phantoms during delivery of proton doses similar to those delivered during patient treatment. Also, the Monte Carlo spectra were found to be in very good agreement with the measured spectra providing an initial validation of our model for use in further studies of prompt gamma ray emission during proton therapy.

The γ-ray strength function and level density in the quasi-continuum of 151,153 Sm have been measured using BGO shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow for an extraction of the γ strength down to unprecedentedly low γ energies of ≈ 500 keV. For the first time an enhanced lowenergy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well known scissors resonance have been observed simultaneously for the same nucleus. HauserFeshbach calculations show that this strength enhancement at low γ energies could have an impact of 2-3 orders of magnitude on the (n,γ) reaction rates for the r-process nucleosynthesis.

The14 C(n, γ) 15 C reaction plays an important role in inhomogeneous big bang models. In [N. K. Timofeyuk et al., Phys. Rev. Lett. 96, 162501 (2006)] it was shown that the 14 C(n, γ) 15 C radiative capture at astrophysically relevant energies is peripheral reaction, i.e. the overall normalization of its cross section is determined by the asymptotic normalization coefficient (ANC) for 15 C → 14 C+n. Here we present new measurements of the 14 C(d, p) 15 C differential cross sections at deuteron incident energy of 17.06 MeV and the analysis to determine the ANCs for neutron removal from the ground and first excited states of 15 C. The results are compared with the previous estimations.

The β-delayed γ and proton decay of 23 Al has been studied with a novel detector setup at the focal plane of the MARS separator at Texas A&M University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous β-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the 23 Al ground state at Ex = 7803 keV in 23 Mg, was observed. Instead we assign the observed low energy group Ep,cm = 206 keV to the decay from a state 16 keV below the IAS. We measured both proton and gamma branches from the decay of this state at Ex = 7787 keV in 23 Mg, a very rare case in the literature. Combining our data with its measured lifetime, we determine its resonance strength to be ωγ = 1.4 +0.5 −0.4 meV. The value is in agreement with older direct measurements, but disagrees with a new direct measurement. This state is the most important resonance for the radiative proton capture 22 Na(p,γ) 23 Mg in some astrophysical environments, such as novae.

The purpose of this work was to characterize how prompt gamma (PG) emission from tissue changes as a function of carbon and oxygen concentration, and to assess the feasibility of determining elemental concentration in tissues irradiated with proton beams. For this study, four tissue-equivalent water-sucrose samples with differing densities and concentrations of carbon, hydrogen, and oxygen were irradiated with a 48 MeV proton pencil beam. The PG spectrum emitted from each sample was measured using a high-purity germanium detector, and the absolute detection efficiency of the detector, average beam current, and delivered dose distribution were also measured. Changes to the total PG emission from 12C (4.44 MeV) and 16O (6.13 MeV) per incident proton and per Gray of absorbed dose were characterized as a function of carbon and oxygen concentration in the sample. The intensity of the 4.44 MeV PG emission per incident proton was found to be nearly constant for all samples regardless of their carbon concentration. However, we found that the 6.13 MeV PG emission increased linearly with the total amount (in grams) of oxygen irradiated in the sample. From the measured PG data, we determined that 1.64 × 107 oxygen PGs were emitted per gram of oxygen irradiated per Gray of absorbed dose delivered with a 48 MeV proton beam. These results indicate that the 6.13 MeV PG emission from 16O is proportional to the concentration of oxygen in tissue irradiated with proton beams, showing that it is possible to determine the concentration of oxygen within tissues irradiated with proton beams by measuring 16O PG emission.

Following neutron knockout from a 13 O beam, 12 O fragments were created and the three decay products following two-proton decay were detected. A new ground-state mass was determined by the invariant mass method implying a decay kinetic energy of 1.638(24) MeV, and the width was found to be less than 72 keV. The latter is inconsistent with previous measurements with lower experimental resolutions, but consistent with theoretical estimates. The isobaric analog of 12 O in 12 N was produced from proton knockout reactions with the same beam and decayed by twoproton emission to the isobaric analog state in 10 B with a decay kinetic energy of 1.165(29) MeV. It represents only the second case of an analog state where two-proton decay is the only isospin and energy conserving particle decay mode. With our measurements of the mass excesses of 12 O and it analog, the quadratic form of the isobaric multiplet mass equation was found to fit the A=12 quintet and any deviations are less than the magnitude found for the A=8 quintet and A=7 and 9 quartets.