[en] We have measured the cross sections for the ¹⁹⁷Au(α,γ)²⁰¹Tl and ¹⁹⁷Au(α,2n)¹⁹⁹Tl reactions in the 17.9- to 23.9-MeV energy range, and ¹⁹⁷Au(α,n)²⁰⁰Tl reaction in the 13.4- to 23.9-MeV energy range using an activation technique. Thick-target yields for the ⁶⁴Zn(α,γ)⁶⁸Ge (7- to 14-MeV) and ⁶³Cu(α,γ)⁶⁷Ga (7-MeV) reactions were measured. For all measurements, natural elements were bombarded with He⁺ beams from the 88'' Cyclotron at the Lawrence Berkeley National Laboratory (LBNL). Irradiated samples were counted using a g-spectrometry system at LBNL's Low Background Facility. Measured ¹⁹⁷Au(α,γ)²⁰¹Tl cross-sections were compared with the NON-SMOKER theoretical values. The thick-target yields for the ⁶⁴Zn(α,γ)⁶⁸Ge and ⁶³Cu(α,γ)⁶⁷Ga reactions are also compared with the theoretical yield, calculated numerically using the energy dependent NON-SMOKER cross section data. In both cases, measured values are found to follow a trend of overlapping the predicted value near the alpha nucleus barrier height and fall below with a slowly widening difference between them in the sub barrier energy points

[en] We have measured cross sections for the ⁶³Cu(α,γ)⁶⁷Ga reaction in the 5.9-8.7 MeV energy range using an activation technique. Natural Cu foils were bombarded with alpha beams from the 88'' Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Activated foils were counted using a gamma spectrometry system at LBNL's Low Background Facility. The ⁶³Cu(α,γ)⁶⁷Ga cross-sections were determined and compared with the latest NONSMOKER theoretical values. Experimental cross sections were found to be in agreement with theoretical values

[en] In this study, a vibration energy harvester is investigated which uses a Ni–Mn–Ga sample that is mechanically strained between 130 and 300 Hz while in a constant biasing magnetic field. The crystallographic reorientation of the sample during mechanical actuation changes its magnetic properties due to the magnetic shape memory (MSM) effect. This leads to an oscillation of the magnetic flux in the yoke which generates electrical energy by inducing an alternating current within the pick-up coils. A power of 69.5 mW (with a corresponding power density of 1.37 mW mm"−"3 compared to the active volume of the MSM element) at 195 Hz was obtained by optimizing the biasing magnetic field, electrical resistance and electrical resonance. The optimization of the electrical resonance increased the energy generated by nearly a factor of four when compared to a circuit with no resonance. These results are strongly supported by a theoretical model and simulation which gives corresponding values with an error of approximately 20% of the experimental data. This model will be used in the design of future MSM energy harvesters and their optimization for specific frequencies and power outputs. (paper)

[en] In step and shoot spot-scanning, a small-diameter proton beam is magnetically swept and varied in energy in order to cover the tumour. Initial estimates of the beam size indicate that additional collimating hardware will be needed for lower energy proton beams in order to achieve a clinically acceptable lateral dose falloff at the edge of the proton beam. In this report, we present dosimetric data from Monte Carlo simulations with a model of a simple multi-leaf collimator which indicate that such a device may be used to improve the lateral dose fall-off. The dosimetric quantities relevant to the clinical usefulness of the device are studied, including lateral penumbra, leaf transmission and scalloping effect. Multi leaf collimation is compared with a differential spot-weighting technique of sharpening the lateral dose falloff. (authors)

[en] We have measured the cross sections for the ¹⁹⁷Au(α,γ)²⁰¹Tl and ¹⁹⁷Au(α,2n)¹⁹⁹Tl reactions in the 17.9- to 23.9-MeV energy range, and ¹⁹⁷Au(α,n)²⁰⁰Tl reaction in the 13.4- to 23.9-MeV energy range using an activation technique. Thick-target yields for the ⁶⁴Zn(α,γ)⁶⁸Ge (7- to 14-MeV) and ⁶³Cu(α,γ)⁶⁷Ga (7-MeV) reactions were measured. For all measurements, natural elements were bombarded with He⁺ beams from the 88 In. Cyclotron at the Lawrence Berkeley National Laboratory (LBNL). Irradiated samples were counted using a γ-spectrometry system at LBNL's Low Background Facility. Measured ¹⁹⁷Au(α,γ)²⁰¹Tl cross sections were compared with the NON-SMOKER theoretical values. The thick-target yields for the ⁶⁴Zn(α,γ)⁶⁸Ge and ⁶³Cu(α,γ)⁶⁷Ga reactions are also compared with the theoretical yield, calculated numerically using the energy dependent NON-SMOKER cross section data. In both cases, measured values are found to follow a trend of overlapping the predicted value near the alpha nucleus barrier height and fall below with a slowly widening difference between them in the sub-barrier energy points

[en] The Low Background Facility (LBF) at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California provides low background gamma spectroscopy services to end-users in two unique facilities: locally within a carefully-constructed, low background laboratory space; and a satellite underground station (600 m.w.e) in Oroville, CA. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic and anthropogenic products, as well as active screening via neutron activation analysis for specific applications. A general overview of the facilities, services, and capabilities will be discussed. Recent activities will also be presented, including the recent installation of a 3π muon veto at the surface facility, cosmogenic activation studies of TeO₂ for CUORE, and environmental monitoring of Fukushima fallout

[en] Flux-averaged cross sections for cosmogenic-neutron activation of natural tellurium were measured using a neutron beam containing neutrons of kinetic energies up to ~800 MeV, and having an energy spectrum similar to that of cosmic-ray neutrons at sea-level. Analysis of the radioisotopes produced reveals that ^110mAg will be a dominant contributor to the cosmogenic-activation background in experiments searching for neutrinoless double-beta decay of ¹³⁰Te, such as CUORE and SNO+. Here, an estimate of the cosmogenic-activation background in the CUORE experiment has been obtained using the results of this measurement and cross-section measurements of proton activation of tellurium. Additionally, the measured cross sections in this work are also compared with results from semi-empirical cross-section calculations.

[en] The Berkeley Low Background Facility (BLBF) at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California provides low background gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low background laboratory on the surface at LBNL and at the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products; active screening via neutron activation analysis for U,Th, and K as well as a variety of stable isotopes; and neutron flux/beam characterization measurements through the use of monitors. A general overview of the facilities, services, and sensitivities will be presented. Recent activities and upgrades will also be described including an overview of the recently installed counting system at SURF (recently relocated from Oroville, CA in 2014), the installation of a second underground counting station at SURF in 2015, and future plans. The BLBF is open to any users for counting services or collaboration on a wide variety of experiments and projects

[en] In preparation for future clinical BNCT trials, neutron production via the ⁷Li(p,n) reaction as well as subsequent moderation to produce epithermal neutrons have been studied. Proper design of a moderator and filter assembly is crucial in producing an optimal epithermal neutron spectrum for brain tumor treatments. Based on in-phantom figures-of-merit, desirable assemblies have been identified. Experiments were performed at the Lawrence Berkeley National Laboratory's 88-inch cyclotron to characterize epithermal neutron beams created using several microamperes of 2.5 MeV protons on a lithium target. The neutron moderating assembly consisted of Al/AlF₃ and Teflon, with a lead reflector to produce an epithermal spectrum strongly peaked at 10-20 keV. The thermal neutron fluence was measured as a function of depth in a cubic lucite head phantom by neutron activation in gold foils. Portions of the neutron spectrum were measured by in-air activation of six cadmium-covered materials (Au, Mn, In, Cu, Co, W) with high epithermal neutron absorbtion resonances. The results are reasonably reproduced in Monte Carlo computational models, confirming their validity

[en] The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.