ALBERT

Beschreibung: We report the development of a CaMoO4 crystal low temperature detector for the AMoRE neutrinoless double beta decay search experiment. The prototype detector cell was composed of a 216 g CaMoO4 crystal and a metallic magnetic calorimeter. An overground measurement demonstrated FWHM resolution of 6–11 keV for full absorption gamma peaks. Pulse shape discrimination was clearly demonstrated in the phonon signals, and 7.6  of discrimination power was found for the and separation. The phonon signals showed rise-times of about 1 ms. It is expected that the relatively fast rise-time will increase the rejection efficiency of two-neutrino double beta decay pile-up events which can be one of the major background sources in searches.

Beschreibung: Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3 powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3 particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3 compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3 powder particles, (b) melting and condensation of Ti5Si3 powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.

Beschreibung: 〈span〉〈div〉ABSTRACT〈/div〉Significant subduction‐zone complexity in southern Peru has been attributed to the subducting Nazca ridge. In this study, we constrained the seismic structure of the Nazca plate to the region where the ridge is subducting and its plate geometry transitions from flat to normal. We applied harmonic decomposition of teleseismic receiver functions (RFs) to retrieve isotropic and anisotropic structures of the oceanic crust and uppermost mantle of the plate, and provide model parameters that best represent the observed structures and clarify the geodynamic processes associated with plate subduction. Harmonic decomposition of the RFs revealed enhanced positive‐polarity amplitudes for the dipping oceanic Moho, indicating the presence of a strong anisotropic (10%–20%) layer near/at the oceanic Moho. This condition requires either anisotropic oceanic crust (AOC) or anisotropic mantle lid (AML) with a predominant trench‐normal fast axis of symmetry for the dipping segment of the slab. The seismic anisotropy produced by the AOC model may indicate strong crystal‐preferred orientation of minerals within the oceanic crust or/and hydrous minerals associated with outer‐rise faulting that developed prior to subduction. The presence of AML may point to frozen olivine fabric in the uppermost mantle of the slab, in alignment with the direction of paleoplate spreading. In the flat‐slab region, the fast‐axis orientation changes abruptly from trench‐normal in the dipping segment to a random direction in the flat segment of the slab. Such disrupted patterns in the fast axes indicate slab fabric deformation due to a high degree of tectonic coupling between the two plates in response to subduction of the Nazca ridge and/or a change in slab dip during the slab‐flattening process. Toward the southeast in the normal dip‐slab region, the presence of frozen olivine fabric in AML is less evident, suggesting that fossil fabric may be overprinted by earlier tectonic processes.〈/span〉

Beschreibung: 〈span〉〈div〉ABSTRACT〈/div〉Significant subduction‐zone complexity in southern Peru has been attributed to the subducting Nazca ridge. In this study, we constrained the seismic structure of the Nazca plate to the region where the ridge is subducting and its plate geometry transitions from flat to normal. We applied harmonic decomposition of teleseismic receiver functions (RFs) to retrieve isotropic and anisotropic structures of the oceanic crust and uppermost mantle of the plate, and provide model parameters that best represent the observed structures and clarify the geodynamic processes associated with plate subduction. Harmonic decomposition of the RFs revealed enhanced positive‐polarity amplitudes for the dipping oceanic Moho, indicating the presence of a strong anisotropic (10%–20%) layer near/at the oceanic Moho. This condition requires either anisotropic oceanic crust (AOC) or anisotropic mantle lid (AML) with a predominant trench‐normal fast axis of symmetry for the dipping segment of the slab. The seismic anisotropy produced by the AOC model may indicate strong crystal‐preferred orientation of minerals within the oceanic crust or/and hydrous minerals associated with outer‐rise faulting that developed prior to subduction. The presence of AML may point to frozen olivine fabric in the uppermost mantle of the slab, in alignment with the direction of paleoplate spreading. In the flat‐slab region, the fast‐axis orientation changes abruptly from trench‐normal in the dipping segment to a random direction in the flat segment of the slab. Such disrupted patterns in the fast axes indicate slab fabric deformation due to a high degree of tectonic coupling between the two plates in response to subduction of the Nazca ridge and/or a change in slab dip during the slab‐flattening process. Toward the southeast in the normal dip‐slab region, the presence of frozen olivine fabric in AML is less evident, suggesting that fossil fabric may be overprinted by earlier tectonic processes.〈/span〉

Beschreibung: We report the development of a CaMoO4crystal low temperature detector for the AMoRE neutrinoless double beta decay(0νββ)search experiment. The prototype detector cell was composed of a 216 g CaMoO4crystal and a metallic magnetic calorimeter. An overground measurement demonstrated FWHM resolution of 6–11 keV for full absorption gamma peaks. Pulse shape discrimination was clearly demonstrated in the phonon signals, and 7.6 σof discrimination power was found for theαandβ/γseparation. The phonon signals showed rise-times of about 1 ms. It is expected that the relatively fast rise-time will increase the rejection efficiency of two-neutrino double beta decay pile-up events which can be one of the major background sources in0νββsearches.

Beschreibung: Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3powder particles, (b) melting and condensation of Ti5Si3powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3is primarily dominated by the solid-liquid mechanism.