Abstract
In this paper we present a method for obtention of neutron
images with Commercial-Off-The-Shelf (COTS) CMOS image sensors
through the activation of indium foils. This detection method has
...been designed specifically for the acquisition of thermal and
epitermal neutron images in mixed beams with a high gamma flux, and
also for the study of high radioactive samples that are usually
placed into research reactor pools. We also present a technique to
obtain multi-spectral neutron images taking advantage of the high
neutron absorption cross-section of this material in the thermal
energy range, as well as around the 1.45 eV resonance. Measurements
performed in a neutron beam of the RA6 nuclear research reactor
located in Bariloche, Argentina, confirm the capability of the
proposed technique.
We present a position-sensitive neutron detection technique based on a Commercial Off-The-Shelf CMOS image sensor (CIS) covered with nanoparticles of sodium gadolinium fluoride (NaGdF4). The ...synthesis procedure and characterization of the NaGdF4 nanoparticles are detailed, as well as the deposition method of the conversion layers over the surface of the chips. We also present a manufacture method of test patterns made with neutron-absorbing materials. These patterns were designed to evaluate the performance of the proposed technique. Analyzing the obtained neutron images we conclude that the intrinsic spatial resolution of the developed method is better than (15±6) μm, this upper bound for the spatial resolution is comparable with that obtained with the best neutron position-sensitive detectors available nowadays.
The surface detector system of the Pierre Auger Observatory Allekotte, I.; Barbosa, A.F.; Bauleo, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2008, Letnik:
586, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Pierre Auger Observatory is designed to study cosmic rays with energies greater than 1019eV. Two sites are envisaged for the observatory, one in each hemisphere, for complete sky coverage. The ...southern site of the Auger Observatory, now approaching completion in Mendoza, Argentina, features an array of 1600 water-Cherenkov surface detector stations covering 3000km2, together with 24 fluorescence telescopes to record the air shower cascades produced by these particles. The two complementary detector techniques together with the large collecting area form a powerful instrument for these studies. Although construction is not yet complete, the Auger Observatory has been taking data stably since January 2004 and the first physics results are being published. In this paper we describe the design features and technical characteristics of the surface detector stations of the Pierre Auger Observatory.
Low temperature thermal and magnetic measurements performed on ferro-magneticl (FM) alloys of composition Ce2.15(Pd1−xAgx)1.95In0.9 are presented. Pd substitution by Ag depresses TC(x) from 4.1 K ...down to 1.1 K for x = 0.5, which is related to the increase of band electrons, with a critical concentration extrapolated to xcr≈0.6. The TC(x) decrease is accompanied by a weakening of the magnetization of the FM phase. At high temperature (T > 30 K) the inverse magnetic susceptibility reveals the presence of robust magnetic moments (2.56 μeff 2.4 μB), whereas the low value of the Curie-Weiss temperature θP≈−10 K excludes any relevant effect from Kondo screening. The specific heat jump at TC(x) decreases accordingly, while an anomaly emerges at a fixed temperature T∗≈1 K. This unexpected anomaly does not show any associated sign of magnetism checked by AC-susceptibility measurements. Since the total magnetic entropy (evaluated around T=TC(x=0)) practically does not change with Ag concentration, the transference of degrees of freedom from the FM component to the non-magnetic T* anomaly is deduced. The origin of this anomaly is attributed to an arising magnetic frustration of the ground state and the consequent entropy bottleneck produced by the divergent increasing of density of excitations at low temperature.
Abstract
The Dark Matter Daily Modulation experiment (DMSQUARE) seeks for dark matter interactions with a Skipper CCD. It is currently running at surface level in Bariloche, Argentina, and will be ...moved to a shallow underground site at Sierra Grande, Argentina in November 2021. The low threshold achieved by Skipper CCDs allows to search for electron recoil events with an ionization energy down to 1.2 eV. In order to extract a potential dark matter signal from noise at the single electron level, we propose to search for a diurnal modulation of events, resulting from the potential interaction of the dark matter wind with the particles in the Earth. Depending on the model, mass and cross-section, this modulation can be maximum at 40deg of latitude in the Southern Hemisphere, where DMSQUARE is operated. In this article we present the experiment, report preliminary results with a prototype Skipper CCD taking data at surface level and comment on future prospects.
•In this manuscript we study the crystalline and superconducting properties of this system, as a possible material to be used in solid state neutron detector sensors.•The results show that this ...superlattice system can be grown even for very thin layers, in spite of the Nb-B binary system showing many possible compounds, which could enhance interdifussion at the interfaces.•Also, the superconducting properties are not degraded, and they are even enhanced with respect to those of single Nb films of the same thickness.•In conclusion, we find that this system is a good potential candidate for the design and construction of solid state neutron Transition Edge Sensors.
We study the growth, stacking and superconducting properties of Nb and B thin films and superlattices. The interest in these resides in their possible use in transition edge neutron sensors. The samples were grown by magnetron sputtering over Si (1 0 0) substrates. The X-ray diffraction patterns for all Nb containing samples show a Nb (1 1 0) preferential orientation. From the low-angle X-ray reflectivity we obtain information on the superlattice structure. The superconducting transition temperatures of the superlattices, obtained from the temperature dependence of the magnetization, are higher than those of single Nb films of similar thickness. The temperature dependence of the perpendicular and parallel upper critical fields indicate that the superlattices behave as an array of decoupled superconducting Nb layers.
We studied the magnetic, transport, and thermodynamic properties of the alloy CeTi1-xScxGe in order to shed some light into the origin of the exceptionally large antiferromagnetic (AFM) ordering ...temperature TN 47 K in pure CeScGe. We observed a complex magnetic phase diagram, which present an interesting dichotomy: Despite strong changes in the nature of the ordered state, from ferromagnetic (FM) for x ≤ 0.55 to AFM for x > 0.55, the ordering temperature increases smoothly and continuously from TC 7 K at x 0.25 to TN 47 K at x 1. Within the AFM regime we observe a metamagnetic transition at a critical field increasing from H 0 at x ≈ 0.55 to μ0 * H ≈ 6 Tesla at x 1. Furthermore a second transition appears at TL ≤ TN for x ≥ 0.65. In contrast to observations in CeRh2Si2 or CeRh3B2, we found no evidence for a strong hybridization of the 4f electrons at large Sc contents. Therefore the exceptionally large TN of CeScGe could be attributed to the unusually strong RKKY interaction in this type of compounds.
Structural, magnetic (M) and thermal (Cm) studies on Ce2(Ni1-yPdy)2Sn alloys are presented within the 0 ≤ y ≤ 0.55 range of concentration, showing evidences for itinerant to local electronic ...transformation. At variance with RKKY type interactions between localized moments μeff, the substitution of Ni by isoelectronic Pd leads the antiferromagnetic transition to decrease from TN 3.8K to 1.2K between y 0 and 0.48, while M(H) measured at H 5T and 1.8K rises from 0.12 up to 0.75μB/Ce-at. Furthermore, the Cm(TN) jump increases with concentration whereas |θP| decreases. The magnetic entropy Sm(T) grows moderately with temperature for y 0 due to a significant contribution of excited levels at low energy, while at y 0.5 it shows a incipient plateau around Sm Rln2. All these features reflect the progressive ground state transformation of from itinerant to a local character. Another peculiarity of this system is the nearly constant value of Cm(TN) that ends in an entropy bottleneck as TN decreases. Consequently, the system shows a critical point at ycr ≈ 0.48 with signs of ferromagnetic behavior above Hcr ≈ 0.3T. A splitting of the Cm(TN) maximum, tuned by field and concentration, indicates a competition between two magnetic phases, with respective peaks at TN ≈ 1.2 K and TI ~ 1.45 K.
Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the ...absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33±0.16 (1.61±0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.
We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. We find that the measured fluctuations are in good ...agreement with predictions from air shower simulations. This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop.
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