The ¹⁷F(p, γ)¹⁸Ne reaction of astrophysical importance has been studied using the surrogate reaction 17F(d, n)18Ne in inverse kinematics. The usefulness of this type of approach has been demonstrated in previous experiments at the RESOLUT facility[1]. In this work we have developed a compact neutron detector array, RESONEUT, which is specialized for (d, n) reactions in inverse kinematics. The threshold and efficiency properties of the neutron detectors were characterized using the ¹²C(d, n)¹³N reaction. Spectroscopy of the ¹⁸Ne nucleus was accomplished using two methods. The first was by neutron time of flight spectroscopy and the second was by kinematic reconstruction of the unbound compound nucleus by detecting the emitted proton and heavy ion. We compared our results with those obtained from ¹⁷F+p elastic scattering measurements and from the direct ¹⁷F(p, γ) measurement conducted at Oak Ridge[2,3]. Our results provide additional confirmation that the state at ~600 keV is the 3⁺ state. No other resonances directly above the proton threshold were detected. However, using NaI(T1) detectors detecting gammas in coincidence with the neutrons in RESONEUT, we have placed upper limits on the possibility of having a low-lying proton resonance with a significant Γ_γ > Γ_p branching ratio.
[1] Peplowski et al, PRC 79, 032801 (2009)
[2] Bardayan et al, PRL 83, 45(1999)
[3] Chipps et al, PRL 102, 152502 (2009)

High-precision measurements of β-decays are sensitive probes of new physics beyond the Standard Model (SM). Particularly, the β-ν correlation of Gamow-Teller decays is sensitive to the exotic tensor type weak current which is predicted by the leptoquark model and some super symmetric models. A new experiment that measures the β-ν correlation coefficient α_βν of the ⁶He decay is being developed at the Center of Experimental Nuclear Physics and Astrophysics (CENPA), University of Washington. In this experiment, the ⁶He atoms are laser-trapped while both the β-particle and the recoil ion are detected. The α_βν is extracted by fitting the time-of-flight (TOF) spectrum of the recoil ions. The ultimate goal of this experiment is a 0.1% determination of α_βν and the short-term goal is to determine α_βν at or lower than 1% and pave the way to the 0.1% level measurement.
In this talk, the construction of the 6He production system, atomic trapping system, β-particle detectors and recoil ion detectors are presented. The ⁶He are produced through reaction ⁷Li + ²H -> ⁶He + ³He. Deuterons are accelerated to 18 MeV by the Van De Graaff accelerator at CENPA, and then hit the molten lithium target. ⁶He atoms diffuse out from the target and then are slowed down and trapped in the magneto-optical trap (MOT). A multi-wire proportional chamber (MWPC) and a plastic scintillator are put above the MOT for β-particle detection, while a micro-channel plate (MCP) is placed below the MOT for recoil ion detection. A uniform electric field is applied in order to increase the ion detection solid angle. The detail design and construction of the detector system are discussed. The Monte Carlo simulation and data analysis software developments are also presented. The sensitivities of systematic effects are studied and the detectors are calibrated to the desired precision and accuracy. Particularly, the position accuracy of the MCP is calibrated below 10 μm and the resolution is improved to 85 μm FWHM. A total systematic uncertainty of the α_βν is expected to be around 0.6% with the present setup.

This work is supported by DOE, Office of Nuclear Physics, under contract nos. DE-AC02-06CH11357 and DE-FG02-97ER41020.

Halo nuclei occur at the limits of stability, where a low binding energy allows valence nucleons to tunnel beyond the nuclear core to form a diffuse nuclear cloud. Several experimental probes have been used to identify and characterize halo nuclei, including interaction cross section measurements, momentum distributions following knockout reactions, and Coulomb dissociation reactions. In particular, an enhanced electric dipole (E1) response at low energy has become a unique signature of halo nuclei. Despite numerous investigations into the E1 response, there is very little information on the magnetic dipole (M1) response of halo nuclei.
In this talk, I will present results of a lifetime measurement of the 3/2⁺ -> 1/2⁺ transition in ¹⁹C. This represents the first measurement of an M1 transition in a halo nucleus. The measurement utilized the line-shape and recoil-distance methods. In the line-shape method, the lifetime is determined based on a distortion of the Doppler-corrected gamma spectrum. With the recoil-distance method, the radioactive beam passes through a degrader downstream of the target, creating fast and slow peaks in the Doppler-corrected gamma spectrum. Both techniques exploited the excellent energy and position resolution of the tracking array GRETINA to identify peak shapes. The results are compared to advanced shell-model calculations in order to understand the microscopic features that allow such an M1 transition. In addition, preliminary results from a one-proton knockout reaction from ²⁰N measured at 70 MeV/nucleon will be presented, and the implications for the structure of ¹⁹C will be compared with the lifetime measurement.

The excited states of ¹⁹⁹At and ²⁰¹At were studied using fusion evaporation reactions, a gas-filled recoil separator and various tagging methods. The level scheme of ²⁰¹At was extended a lot including a cascade of magnetic dipole transitions, that is suggested to form a shears band. In addition, a 29/2⁺ [T_1/2 = 3.39(9) ms] isomeric state was observed. The 29/2⁺ state is suggested to originate from the π(h_9/2)X|²⁰⁰Po; 11^- > configuration, and it depopulates through 269-keV E2 and 339-keV E3 transitions. In both nuclei ^199,201At we have observed also the isomeric 1/2⁺ [T_1/2 = 273(9), 45(3) ms, respectively] intruder state, that is suggested to originate from the π(s_1/2)^-1 configuration. The 1/2⁺ state decays through 103-keV and 269-keV E3 transitions in ^199,201At, respectively. In both nuclei the 1/2⁺ state is fed from 3/2⁺ and 5/2⁺ states, which are suggested to originate from the π(d_3/2)^-1 and π(d_5/2)^-1 configurations, respectively.
The text above is the abstract of my doctoral thesis. In this talk I will give an introduction to its topics. The used experimental devices and methods will be presented together with the three mentioned main results.

The competition between spherical and deformed configurations gives rise to shape coexistence in the neutron-deficient isotopes around Z~82 and N~104 [1] while on the neutron-rich side, effects due to octupole deformation in the vicinity of N~133 could be expected [2]. In order to determine to which extent the ground and isomeric states of these nuclides are affected by these phenomena, an extensive campaign of investigation of changes in the mean-square charge radii and electromagnetic moments is being conducted by our collaboration at the mass-separator ISOLDE (CERN). The measurements rely on the high sensitivity provided by the in-source laser spectroscopy technique [3, 4].
In this contribution, we will present the extended systematics of charge radii and magnetic moments recently obtained for the mercury (April 2015), gold (May 2015) and astatine (September 2014) isotopic chains at ISOLDE. In all three cases, the Windmill decay spectroscopy setup [5] and the Multi-Reflection Time-of-Flight (MR-TOF) mass separation technique [6] were used.

[1] K. Heyde and J. Wood, Rev. Mod. Phys. 83, 1467 (2011)
[2] L.P. Gaffney et al., Nature, 497, 199 (2013)
[3] B.A. Marsh et al., NIM B 317, 550 (2013)
[4] A. E. Barzakh et al., Rev. Sci. Instr. 83, 02B306 (2012)
[5] A.N. Andreyev et al,, Phys. Rev. Lett. 105, 252502 (2010)
[6] R. N. Wolf et al., NIM A 686, 82-90 (2012)

Fusion-evaporation is the dominant reaction mechanism in medium-mass heavy-ion collisions around the Coulomb barrier. At these energies and at moderate sub-barrier energies, enhancement of the fusion cross-sections was observed whereas hindrance of the fusion cross- section has been identified in many systems at deep sub-barrier energies. Fusion cross-sections around the Coulomb barrier have been discussed extensively to be driven by couplings of the relative motion of the colliding nuclei to their low energy surface vibrations and/or stable deformations. The corresponding coupled-channel calculations and the distributions of barriers have revealed to be a powerful tool to better understand the role of couplings to collective degrees of freedom of the target and projectile.
The strong sensitivity of the sub-barrier fusion probability to the structure of the colliding nuclei will be presented as well as recent results on the influence of particle transfer channels on the fusion cross-sections in medium mass systems like Ca+Ca and Ca+Ni.
For lighter systems like C+C and C+O, nuclear fusion is strongly connected to astrophysics, as it is an essential step in the synthesis of the chemical elements in stars. Experimental work on resonances observed in these systems will be discussed.