Abstract
The search for neutrinoless double beta decay (0
νββ
) remains one of the most compelling experimental avenues for the discovery in the neutrino sector. Electroluminescent gas-phase time ...projection chambers are well suited to 0
νββ
searches due to their intrinsically precise energy resolution and topological event identification capabilities. Scalability to ton- and multi-ton masses requires readout of large-area electroluminescent regions with fine spatial resolution, low radiogenic backgrounds, and a scalable data acquisition system. This paper presents a detector prototype that records event topology in an electroluminescent xenon gas TPC via VUV image-intensified cameras. This enables an extendable readout of large tracking planes with commercial devices that reside almost entirely outside of the active medium. Following further development in intermediate scale demonstrators, this technique may represent a novel and enlargeable method for topological event imaging in 0
νββ
.
We present a tunable metal ion beam that deliverscontrollable ion currents in the picoamp range for testing ofdry-phase ion sensors. Ion beams are formed by sequential atomicevaporation and single or ...multiple electron impact ionization,followed by acceleration into a sensing region. Controllability ofthe ionic charge state is achieved through tuning of electrodepotentials that influence the retention time in the ionizationregion. Barium, lead, and cadmium samples have been used to test thesystem, with ion currents identified and quantified using aquadrupole mass analyzer. Realization of a clean Ba2+ ion beam within a bench-top system represents an important technicaladvance toward the development and characterization of bariumtagging systems for neutrinoless double beta decay searches in xenongas. This system also provides a testbed for investigation of novelion sensing methodologies for environmental assay applications, withdication beams of Pb2+ and Cd2+ also demonstrated for thispurpose.
Abstract
Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. In noble element systems, it is often coated with ...tetraphenyl butadiene (TPB) to allow detection of vacuum ultraviolet scintillation light. In this work this dependence is investigated for PTFE coated with TPB in air for light of wavelengths of 200 nm, 260 nm, and 450 nm. The results show that TPB-coated PTFE has a reflectance of approximately 92% for thicknesses ranging from 5 mm to 10 mm at 450 nm, with negligible variation as a function of thickness within this range. A cross-check of these results using an argon chamber supports the conclusion that the change in thickness from 5 mm to 10 mm does not affect significantly the light response at 128 nm. Our results indicate that pieces of TPB-coated PTFE thinner than the typical 10 mm can be used in particle physics detectors without compromising the light signal.
Recent fieldwork, geochemistry, and U-Pb geochronology in the Palaeoproterozoic Ketilidian orogen provide substantial insights into the timing and mechanisms of its magmatic, sedimentary, and ...tectonic accretion. From north to south the orogen comprises an Archaean foreland and Border Zone, a calc-alkaline arc, and a migmatized fore arc. Contrasting the marginally older Nagssugtoqidian orogen of central West Greenland, the Ketilidian orogen is juvenile, lacks evidence of continent-continent collision, and probably evolved during northward subduction of an oceanic plate under the Archaean craton, with a suture south of the present orogen. Palaeoproterozoic dolerite dyke emplacement into the cratonic margin was followed by deposition of Ketilidian cover rocks. Thrusting and dextral transpression before 1848 Ma in the northwest may correlate with 1895-1870 Ma dextral transpression in the Makkovik orogen, Labrador. Sinistral transpression and I-type granite emplacement followed at 1848-1805 Ma. In the northeast, limited geochronology indicates deformation and metamorphism at ca. 1800 Ma. The calc-alkaline Julianehab batholith was largely emplaced between 1854-1795 Ma during sinistral transpression, giving rise to steep magmatic fabrics and northeast-trending shear zones. Until 1790 Ma, the proximal fore-arc basin (Psammite Zone) received coarse detritus from the batholith, and turbidity currents swept sands and muds into distal parts. Fore-arc sedimentation, pervasive deformation, high temperature - low pressure (HT-LP) metamorphism and anatexis occurred at 1795-1785 Ma: flat-lying planar fabrics with top-to-northeast transport were due to tectonic decoupling at the outboard batholith margin during continued transpression. Rapakivi granite sheets were emplaced at 1755-1732 Ma and folded into broad arches and narrow synclinal cusps compatible with late-stage sinistral transpression.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cretaceous rocks on the continental margin of northern Chile record a complex geodynamic evolution. Cycles of transtensional and transpressional deformation and of extrusive and intrusive magmatism ...are linked to the development of crustal-scale lineaments. The Landsat Thematic Mapper is used here as a tool to define these structural features. Geocorrected data were digitally enhanced and lineaments plotted directly from a hard copy image, thereby excluding artificial or non-geological features that might degrade the subsequent structural analysis. The lineaments were then digitized and analysed using a Weighted Moving Average (WMA) technique to suppress noise and to enhance azimuthal variation. Statistical analysis of the data reveals three lineament populations. The first is a set of NNE-trending lineaments that belong to the margin-parallel, sinistral Atacama Fault System. The second is a series of NW-trending lineaments with a similar orientation to large-scale structures identified across the South American continental plate. The third is a widely spaced set of NE-trending lineaments. The key result of this study is that lineaments identified from remotely sensed data may have orientation patterns that differ considerably from those identified by traditional geological mapping and that full structural analysis of structurally complex crustal regions will likely be incomplete without a comprehensive analysis of remotely sensed data. Although the NW-trending structures are numerically dominant on the Landsat TM image, they are seldom recorded at map scale and are under-represented on published geological maps. Of the 275 faults marked on the published geological map sheets, 89 are N to NNE-trending and only 88 are NW-trending. By contrast, of 841 lineaments identified from the satellite image, 455 are NW-trending and 178 are N- to NNE-trending. The lack of prior recognition of the NW-trending structures means that their importance has been underestimated in reconstructions of the geodynamic evolution of the region. In addition, as major ore deposits in the region are frequently located at intersections between two fracture systems, the recognition here of the NW-trending set of structures should illuminate future mineral exploration programmes.
In this paper we discuss the evolution and tectonic significance of the Mesozoic trench-parallel fault systems which affected the Coastal Cordillera and their relation to magmatism and crustal ...rotation. The oldest, extensional, fault system separates basement from rift-related Late Triassic and younger sedimentary units. This system I subsequently developed into a wider extensional fault system which acted as the locus of magma ascent and emplacement of the Coastal Batholith during much of the Jurassic to earliest Cretaceous period. This extensional fault system defined the forearc sliver during this period and was the consequence of a retreating subduction boundary. During the Early Cretaceous (c. 132–125 Ma) the kinematics of this fault system changed to transtension II and accommodated a major component of left-lateral strike-slip motion, the principal fault being the Atacama Fault Zone along which plutons continued to be emplaced. The final phase of pluton emplacement within the Coastal Cordillera appears to be c. 106 Ma, after which this magmatic arc and fault system was abandoned. An Late Cretaceous arc and fault system III developed some 20 Ma later and located some 50 km to the east in what is now the Central Valley of northern Chile. This paper seeks to show that the Coastal Cordillera was deformed as a whole by this Late Cretaceous fault system III which formed a crustal-scale left-lateral transpressional duplex. During this deformation the thermally weakened crust was dissected into a series of large-scale blocks bounded by NW-trending left-lateral strike-slip faults which merge into a NNE–SSW fault zone which forms the eastern boundary to the duplex. We term this eastern boundary zone the Central Valley Fault Zone (CVFZ) and this together with the NW-trending faults defines the duplex system which we refer to as a whole as the Coastal Cordillera Fault System (CCFS) III. We have traced the CCFS duplex between 25°S and 29°S and suspect that it continues northward. The timing of the deformation is constrained to be post 106 Ma, the age of Coastal Cordillera arc abandonment, and pre-Tertiary based on the deformation and pluton emplacement in and along the Central Valley Fault Zone. Palaeomagnetic data from the fault bound blocks within the CCFS duplex indicate 35°–45° of post-Early Cretaceous clockwise rotation with no substantial latitudinal motion. We suggest that the observed fault kinematics of the CCFS are consistent with this crustal-scale duplex model where rotations would have occurred in response to left-lateral transpression.
Abstract
NEXT-100 is currently being constructed at the Laboratorio
Subterráneo de Canfranc in the Spanish Pyrenees and will search
for neutrinoless double beta decay using a high-pressure gaseous
...time projection chamber (TPC) with 100 kg of xenon. Charge
amplification is carried out via electroluminescence (EL) which is
the process of accelerating electrons in a high electric field
region causing secondary scintillation of the medium proportional to
the initial charge. The NEXT-100 EL and cathode regions are made
from tensioned hexagonal meshes of 1 m diameter. This paper
describes the design, characterization, and installation of these
parts for NEXT-100. Simulations of the electric field are performed
to model the drift and amplification of ionization electrons
produced in the detector under various EL region alignments and
rotations. Measurements of the electrostatic breakdown voltage in
air characterize performance under high voltage conditions and
identify breakdown points. The electrostatic deflection of the mesh
is quantified and fit to a first-principles mechanical model.
Measurements were performed with both a standalone test EL region
and with the NEXT-100 EL region before its installation in the
detector. Finally, we describe the parts as installed in NEXT-100,
following their deployment in Summer 2023.
Abstract
We present a tunable metal ion beam that delivers
controllable ion currents in the picoamp range for testing of
dry-phase ion sensors. Ion beams are formed by sequential atomic
evaporation ...and single or multiple electron impact ionization,
followed by acceleration into a sensing region. Controllability of
the ionic charge state is achieved through tuning of electrode
potentials that influence the retention time in the ionization
region. Barium, lead, and cadmium samples have been used to test the
system, with ion currents identified and quantified using a
quadrupole mass analyzer. Realization of a clean Ba
2+
ion beam within a bench-top system represents an important technical
advance toward the development and characterization of barium
tagging systems for neutrinoless double beta decay searches in xenon
gas. This system also provides a testbed for investigation of novel
ion sensing methodologies for environmental assay applications, with
dication beams of Pb
2+
and Cd
2+
also demonstrated for this
purpose.
In the Palaeoproterozoic Ketilidian orogen of South Greenland, tabular intrusions of the rapakivi granite suite exposed at Graah Fjelde. Lindenow Fjord and Qernertoq, and a Mesoproterozoic syenite of ...the Gardar province exposed at Paatusoq, were emplaced by a combination of roof uplift and floor depression. The strain associated with the emplacement of the intrusions mainly involved redistribution of mass vertically within the lithosphere. Space for the emplacement of the rapakivi plutons was not created during regional extension on low-angle, ductile shear zones as claimed by some previous workers and there is no evidence that emplacement of the intrusions coincided with extensional collapse of the orogen following crustal thickening. The rapakivi granites post-date peak metamorphism in the orogen by 35-46 Ma and their contacts cross-cut and clearly post-date intense, flat-lying D1/D2 fabrics that formed by partitioning of deformation into arc-normal and arc-parallel components during oblique convergence.
Three fault systems were responsible for Permian to Late Cretaceous deformation of the overriding plate of the Andean convergent margin in the Coastal Cordillera of northern Chile (25°30' to ...27°00'S). Displacements were linked to crustal growth expressed by the emplacement of a sequence of magmatic arcs. The Tigrillo Fault System, active from Triassic to Early Cretaceous time, was characterized by arc-normal extension with increasing left-oblique extension (transtension) from Early Jurassic to Early Cretaceous time. Stretching of the crust created space for Triassic, Early Jurassic and Early Cretaceous arc basins where epiclastic, volcaniclastic and volcanic sequences accumulated in continental to shallow marine environments. Tabular plutonic complexes were emplaced by roof uplift-floor subsidence that allowed a vertical transfer of material in the crust without significant horizontal extension. The Atacama Fault System was initiated at c. 132 Ma as a (mainly) left strike-slip fault during left-oblique extension of the margin. Elongate, tabular plutonic complexes were emplaced within the Atacama Fault System between c. 132 and c. 106 Ma, again by roof uplift-floor subsidence mechanisms. Ductile-brittle transitions in synplutonic mylonitic rocks of the Atacama Fault System provided the setting for Kiruna-type Fe-apatite, and Fe oxide (with Cu and/or Au) ores. The Chivato Fault System was active as an extensional fault system at the eastern side of the Coastal Cordillera during displacement on the Tigrillo Fault System and later, between c. 125 and c. 93 Ma, as a partitioned left-oblique extensional fault system. In post-Early Cretaceous time the Chivato Fault System was inverted by left-oblique contraction (transpression) when NW-trending transfer faults, some probably reactivated lateral ramps in the Tigrillo Fault System, accommodated clockwise vertical-axis rotations of 35-45°. Contraction inverted the Atacama Fault System and Tigrillo Fault System and was responsible for west-vergent, thin-skinned, fold-thrust deformation in stratified rocks throughout the margin.
