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
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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.
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.
The Large Aperture GRB Observatory (LAGO) project aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique in ground-based water-Cherenkov ...detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550
m a.s.l.), Bolivia (Chacaltaya, 5300
m a.s.l.) and Venezuela (Mérida, 4765
m a.s.l.). We report on detector calibration and operation at high altitude, search for bursts in 4 months of preliminary data, as well as search for signal at ground level when satellites report a burst.
The transition energy from galactic to extragalactic cosmic ray sources is still uncertain, but it should be associated either with the region of the spectrum known as the second knee or with the ...ankle. The baseline design of the Pierre Auger Observatory was optimized for the highest energies. The surface array is fully efficient above 3
×
10
18
eV and, even if the hybrid mode can extend this range below 10
18
eV, the second knee and a considerable portion of the wide ankle structure are left outside its operating range. Therefore, in order to encompass these spectral features and gain further insight into the cosmic ray composition variation along the transition region, enhancements to the surface and fluorescence components of the baseline design are being implemented that will lower the full efficiency regime of the Observatory down to ∼10
17
eV. The surface enhancements consist of a graded infilled area of standard Auger water Cherenkov detectors deployed in two triangular grids of 433
m and 750
m of spacing. Each surface station inside this area will have an associated muon counter detector. The fluorescence enhancement, on the other hand, consists of three additional fluorescence telescopes with higher elevation angle (30°–58°) than the ones in operation at present. The aim of this paper is threefold. We study the effect of the segmentation of the muon counters and find an analytical expression to correct for the under counting due to muon pile-up. We also present a detailed method to reconstruct the muon lateral distribution function for the 750
m spacing array. Finally, we study the mass discrimination potential of a new parameter, the number of muons at 600
m from the shower axis, obtained by fitting the muon data with the above mentioned reconstruction method.
Magnetic and thermal properties of Ferromagnetic (FM) Ce2.15(Pd1-xAgx)1.95In0.9 alloys were studied in order to determine the Quantum Critical Point (QCP) at TC → 0. The in- crease of band electrons ...produced by Pd/Ag substitution depresses TC (x) from 4.1K down to TC (x = 0.5)=1.1K, with a QCP extrapolated to xQCP ≥ 0.5. Magnetic susceptibility from T > 30K indicates an effective moment slightly decreasing from μeff =2.56μB to 2.4μB at x=0.5. These values and the paramagnetic temperature θP ≈ -10K exclude significant Kondo screening effects. The TC (x) reduction is accompanied by a weakening of the FM magnetization and the emergence of a specific heat Cm(T) anomaly at T* ≈ 1K, without signs of magnetism detected from AC-susceptibility. The magnetic entropy collected around 4K (i.e. the TC of the x = 0 sample) practically does not change with Ag concentration: Sm(4K) ≈ 0.8 Rln2, suggesting a progressive transfer of FM degrees of freedom to the non-magnetic (NM) compo- nent. No antecedent was found concerning any NM anomaly emerging from a FM system at such temperature. The origin of this anomaly is attributed to an entropy bottleneck originated in the nearly divergent power law dependence for T >T*
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