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Miller, D.

Publications and source records attributed to Miller, D..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Experimental study of the β - γ and β - n γ decay of the neutron-rich nucleus 85 Ga

We studied the β-decay properties of neutron-rich 85 Ga produced in proton-induced fission of 238 U at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Data consisted of β-γ and β-γ-γ coincidences were collected at the Low-energy Radioactive Ion Beam Spectroscopy Station after high-resolution on-line mass separation. For the first time, the excited states in the N=53 isotone 85 Ge were established from β-delayed γ decay of 85 Ga. The level scheme of the N=52 isotone 84 Ge was improved and includes now 0 + , 2 + , (2) + , 4 + , and (0) + states populated in the β-delayed-neutron-γ decay of 85 Ga. Advanced shell-model calculations were used to analyze experimental data on 85 Ge and 84 Ge.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Large beta-delayed one-neutron and two-neutron emission rates in the decay of 86Ga

Beta decay of Ga86 was studied by means of β-neutron-γ spectroscopy. An isotopically pure 86 Ga beam was produced at the Holifield Radioactive Ion Beam Facility using a resonance ionization laser ion source and high-resolution electromagnetic separation. The decay of 86 Ga revealed a half-life of 43+21-15 ms and large β-delayed one-neutron and two-neutron branching ratios of P 1n =60(10)% and P 2n =20(10)%. The βγ decay of 86 Ga populated a 527 keV transition that is interpreted as the deexcitation of the first 2 + state in the N=54 isotone Ge86 and suggests a quick onset of deformation in Ge isotopes beyond N=50.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Examination of an Optical Transmittance Test for Photovoltaic Encapsulation Materials (Presentation)

The optical transmittance of encapsulation materials is a key characteristic for their use in photovoltaic (PV) modules. Changes in transmittance with time in the field affect module performance, which may impact product warranties. Transmittance is important in product development, module manufacturing, and field power production (both immediate and long-term). Therefore, an international standard (IEC 62788-1-4) has recently been proposed by the Encapsulation Task-Group within the Working Group 2 (WG2) of the International Electrotechnical Commission (IEC) Technical Committee 82 (TC82) for the quantification of the optical performance of PV encapsulation materials. Existing standards, such as ASTM E903, are general and more appropriately applied to concentrated solar power than to PV. Starting from the optical transmittance measurement, the solar-weighted transmittance of photon irradiance, yellowness index (which may be used in aging studies to assess durability), and ultraviolet (UV) cut-off wavelength may all be determined using the proposed standard. The details of the proposed test are described. The results of a round-robin experiment (for five materials) conducted at seven laboratories to validate the test procedure using representative materials are also presented. For example, the Encapsulation Group actively explored the measurement requirements (wavelength range and resolution), the requirements for the spectrophotometer (including the integrating sphere and instrument accessories, such as a depolarizer), specimen requirements (choice of glass-superstrate and -substrate), and data analysis (relative to the light that may be used in the PV application). The round-robin experiment identified both intra- and inter-laboratory instrument precision and bias for five encapsulation materials (encompassing a range of transmittance and haze-formation characteristics).

14 SOLAR ENERGY↗
DOE OSTI2013

Framework for a Comparative Accelerated Testing Standard for PV Modules: Preprint

As the photovoltaic industry has grown, the interest in comparative accelerated testing has also grown. Private test labs offer testing services that apply greater stress than the standard qualification tests as tools for differentiating products and for gaining increased confidence in long-term PV investments. While the value of a single international standard for comparative accelerated testing is widely acknowledged, the development of a consensus is difficult. This paper strives to identify a technical basis for a comparative standard.

14 SOLAR ENERGY↗
DOE OSTI2013

Imaging of molybdenum erosion and thermography at visible wavelengths in Alcator C-Mod ICRH and LHCD discharges

The spatially complex plasma-material interactions (PMI) in magnetic fusion devices which can deposit excess heat and particle fluxes causing respective melting and erosion of plasma facing components (PFC’s) requires the use of imaging diagnostics to understand experimental operations. In future magnetic fusion devices, imaging diagnostics must over come difficulties which do not occur in many present machines.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2013

Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Mod

Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed reduced with the FA antenna configuration, the mechanism determining the SOL plasma potential in the presence of ICRF and its impact on impurity contamination and sources remains to be understood.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

On-Line Commissioning of the HRIBF Resonant Ionization Laser Ion Source

A highly-selective resonant ionization laser ion source has been successfully commissioned at the Holifield Radioactive Ion Beam Facility, Oak Ridge National Laboratory, for the production of pure beams of short-lived nuclei for spectroscopic studies. The laser ion source provided beams of neutron-rich Ga isotopes to the Low-energy Radioactive Ion Beam Spectroscopy Station for beta decay measurements. The radioactive Ga isotopes were produced by 50-MeV proton induced fission of 238U and ionized by laser radiation using a two-step resonant ionization scheme. Isobarically pure 83Ga, 85Ga, and 86Ga beams were delivered to the experiment at approximate rates of 12000 ions/s, 100 ions/s, and 3 ions/s, respectively.

Liu, Yuan↗