J.R. Leslie

Analogue states excited in the reaction 56Fe(p, γ)57Co

Abstract Resonances in the reaction 56 Fe(p,γ) 57 Co at E p , ≈ 1250 keV and E p ≈ 1650 keV have been studied and identified as split analogues of states of 57 Fe. Gamma-ray angular distributions have been used to assign resonance spins, decay schemes have been constructed, and in most cases the resonance strengths have been determined. Spin assignments ( E p (keV); J ) based on this work are: ( 1247; 3 2 ), ( 1262; 1 2 , 3 2 ), ( 1267; 3 2 ), ( 1623; 3 2 , 5 2 ), ( 1637; 1 2 , 3 2 ), (1646; 3 2 ) and ( 1652; 3 2 ). The properties of these analogue resonances appear to be similar to those observed in previous investigations of the region A ≈ 50.

High-resolution γ-ray spectroscopy: a versatile tool for nuclear β-decay studies at TRIUMF-ISAC

High-resolution γ-ray spectroscopy is essential to fully exploit the unique, high-quality beams available at the next generation of radioactive ion beam facilities such as the TRIUMF isotope separator and accelerator (ISAC). The 8π spectrometer, which consists of 20 Compton-suppressed HPGe detectors, has recently been reconfigured for a vigorous research programme in weak interaction and nuclear structure physics. With the addition of a variety of ancillary detectors it has become the worlds most powerful device dedicated to β-decay studies. This paper provides a brief overview of the apparatus and highlights from recent experiments.

Corrosion of Zr-2.5 wt% Nb pressure tube material in D2O steam: deuterium depth distributions measured by nuclear reaction analysis

Abstract The corrosion of Zr-2.5 wt% Nb pressure tube material in D 2 O steam at 763 K has been studied by nuclear reaction and backscattering spectrometry. The oxide thicknesses — ranging from 3–7 μm — were determined by backscattering of 2.5 MeV protons. The deuterium depth distributions from the surface to beneath the oxide have been determined using the d( 3 He, p) 4 He nuclear reaction. The oxide contains high deuterium concentrations (0.003–0.005 D/Zr). Samples which have been “pickled” prior to corrosion have slightly thinner oxides, increased deuterium levels in the metal, and the deuterium depth profiles show a micrometer-wide depletion in deuterium, which may reflect an interfacial region with stress and plastic deformation.

The effect of anodic oxidation on near-surface deuterium in Zr-2.5 wt.% Nb

Abstract The effect of anodic oxidation on near-surface deuterium in thin ( ∼ 3.5 μm) foils of Zr-2.5 wt.% Nb has been studied with the 2 D( 3 He, p) 4 He nuclear reaction. To introduce deuterium into the foil, the native oxide was etched with a solution of 0.1% NH 4 HF 2 in D 2 O. The foils were anodized, in a compact cell in a vacuum chamber, to oxide thicknesses of 160, 200 and 280 nm and the remaining D concentration measured. The D content was also measured, in separate experiments, with the anodized surface towards the beam. Detailed analysis shows that the effect of oxidation is to return most of the D in the anodized region to the solution.

Evidence for vibrational excited states in 32S

Abstract The 0 2 + , 2 2 + and 4 1 + states at 3781, 4283 and 4461 keV respectively in 32 S were studied, with emphasis on the latter two. The spin and parity of 4 + was confirmed for the 4461 keV state. Theγ-ray energies of the 4 1 + → 2 1 + and 2 1 + → O 1 + transitions were determined as 2229.4 ± 1.2 and 2231.7 ± 1.0 keV, respectively. The lifetimes of the 4 1 + and 2 1 + states were measured by the Doppler-shift attenuation method as 0.21 ± 0.06 and 0.35 ± 0.06 ps respectively. The 2 2 + → O 1 + and 2 2 + → 2 1 + transitions have a branching ratio of 5.9 ± 0.3, and the latter is pure E2 within the experimental error. The strengths of the 2 1 + → 0 1 + , 0 2 + → 2 1 + , 2 2 + → 2 1 + and 4 1 + → 2 1 + transitions are respectively 7 ± 1, 15 ± 4, 7.3 ± 0.7 and 12 ± 3 W.u. These values suggest that the 2 1 + level is a one-phonon vibrational state and that the 0 2 + , 2 2 + and 4 1 + levels make up a predominately two-phonon vibrational triplet.

A comparative study of deuterium ingress from solution into Zr, Zircaloy-2 and Zr-2.5wt.% Nb by nuclear reaction analysis at the liquid-solid interface

We have compared deuterium ingress into thin (1.5–4.5 μm) foils of Zr, Zircaloy-2 and Zr-2.5wt.% Nb using the D( 3He, p) 4He nuclear reaction. The foils were mounted in a compact cell in a vacuum chamber and the foil and liquid in the cell were analyzed with a 3He beam. We introduced deuterium into the foils by etching their native oxide layers with a solution of 0.1% NH 4HF2 in D2O. The amount of deuterium taken up by the foils was measured in situ as well as in separate experiments ex situ in which the etched surfaces were turned toward the beam. The results show that deuterium uptake occurs in the order Zr-2.5wt.% Nb < Zr < Zircaloy-2.

In situ NRA studies of hydrogen ingress into Zr-2.5 wt.% Nb at the liquid-solid interface

Abstract Deuterium ingress into thin (3–5 μm) foils of Zr-2.5 wt.% Nb has been studied with the D( 3 He, p) 4 He nuclear reaction. The foils were mounted in a compact cell in a vacuum chamber and a 3 He beam bombarded the foil and liquid in the cell. We introduced ∼ 30at.% of D into the foil by removing the native oxide layer with a solution of 0.1 wt.% NH 4 HF 2 in D 2 O and then cathodically charging the foil using a 0.1M H 2 SO 4 in D 2 O solution. We anodized these foils, as well as unetched ones, using 0.1M H 2 SO 4 in D 2 O solutio and then measured the deuterium content in situ as well as in separate experiments with the anodized surface turned toward the beam.

Scattering recoil coincidence spectrometry: A new experimental technique for profiling hydrogen isotopes in low-Z thin films

Abstract The new technique for profiling light elements in thin, self-supporting foils, which uses a coincidence measurement over very large solid angles, has been demonstrated experimentally. A beam of 2.0 MeV 4 He particles was used to bombard films of (i) cracked ethylene and (ii) evaporated carbon which was subsequently implanted with 7.5 keV 1 H + ions to a concentration of 10 17 /cm 2 . Plots of E α vs E p clearly show the 1 H distributions in the foil.

Precision half-life measurement of 62Ga

A measurement of the half-life of 62Ga was made as part of a programme of high-precision superallowed Fermi β decay studies at the ISAC radioactive beam facility. The experiment was conducted by counting β+ particles from the decay of 62Ga in a 4π gas proportional counter. The half-life was measured to be 116.01 ± 0.19 ms. Several parameters were varied during the experiment to test for systematic effects, but no significant effects were found.

The early stage of aqueous corrosion of Zr-2.5 wt% Nb and Zircaloy-2 pressure tube materials

Abstract The early stage of aqueous corrosion has been studied in Zr-2.5 wt% Nb and Zircaloy-2 pressure tube materials by immersing specimens of these alloys in heavy water for 1 day at temperatures ranging from 293 to 573 K. The deuterium and oxygen distributions were measured by nuclear reaction analysis. The oxide layer appeared to have a non-uniform thickness. It was measured to be 20 to 40 nm over the temperature range from 293 to 473 K. Above 523 K the oxide thickness was greater than 100 nm. Deuterium was present in the oxide layer at 373 K and above, whereas deuterium levels of ~ 5 mg/kg are measured in the metallic phase above 373 or 423 K depending on whether the specimen was Zircaloy-2 or Zr-2.5 wt% Nb. It is suggested that the deuterium ingress in this early stage is controlled mainly by deuterium diffusion in the oxide.