We present an improved method for the precise reconstruction of cosmic-ray air showers above 1017 eV with sparse radio arrays. The method is based on the comparison of measured pulses to predictions ...for radio pulse shapes by CoREAS simulations. We applied our method to the data of Tunka-Rex, a 1 km2 radio array in Siberia operating in the frequency band of 30–80 MHz. Tunka-Rex is triggered by the air-Cherenkov detector Tunka-133 and by scintillators (Tunka-Grande). The instrument collects air-shower data since 2012. The present paper describes an updated data analysis of Tunka-Rex and details of the new method applied. After quality cuts, when Tunka-Rex reaches its full efficiency, the energy resolution of about 10% given by the new method has reached the limit of systematic uncertainties due to the calibration uncertainty and shower-to-shower fluctuations. At the same time the shower maximum reconstruction has improved compared to the previous method based on the slope of the lateral distribution and reaches a precision of better than 35 g/cm2. We also define conditions of the measurements at which the shower maximum resolution of Tunka-Rex reaches a value of 25 g/cm2 and becomes competitive to optical detectors. To check and validate our reconstruction and efficiency cuts we compare individual events to the reconstruction of Tunka-133. Furthermore, we compare the mean of the shower maximum as a function of primary energy to the measurements of other experiments.
The radio technique is a promising method for detection of cosmic-ray air showers of energies around 100PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be ...measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately 10% – limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level.
We reconstructed the energy and the position of the shower maximum of air showers with energies E ∼> 100 PeV applying a method using radio measurements performed with Tunka-Rex. An event-to-event ...comparison to air-Cherenkov measurements of the same air showers with the Tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. The Tunka-Rex reconstruction methods and absolute scales have been tuned on CoREAS simulations and yield energy and X{sub max} values consistent with the Tunka-133 measurements. The results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. The energy precision of Tunka-Rex is comparable to the Tunka-133 precision of 15%, and exhibits a 20% uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. For X{sub max}, this is the first direct experimental correlation of radio measurements with a different, established method. At the moment, the X{sub max} resolution of Tunka-Rex is approximately 40 g/cm{sup 2}. This resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations.
Tunka-Rex is a radio detector for cosmic-ray air showers in Siberia, triggered by Tunka-133, a co-located air-Cherenkov detector. The main goal of Tunka-Rex is the cross-calibration of the two ...detectors by measuring the air-Cherenkov light and the radio signal emitted by the same air showers. This way we can explore the precision of the radio-detection technique, especially for the reconstruction of the primary energy and the depth of the shower maximum. The latter is sensitive to the mass of the primary cosmic-ray particles. In this paper we describe the detector setup and explain how electronics and antennas have been calibrated. The analysis of data of the first season proves the detection of cosmic-ray air showers and therefore, the functionality of the detector. We confirm the expected dependence of the detection threshold on the geomagnetic angle and the correlation between the energy of the primary cosmic-ray particle and the radio amplitude. Furthermore, we compare reconstructed amplitudes of radio pulses with predictions from CoREAS simulations, finding agreement within the uncertainties.
The paper presents the structure and phase composition of Ti−Al−Si powder composites produced in different conditions, which include vacuum sintering and self-propagating high-temperature synthesis ...(SHS). The certain ratios of reactive components are used in experiments for the formation of two-phase composites, matching the TiAl
3
+ Ti
5
Si
3
and Ti
3
Al + Ti
5
Si
3
compositions. The vacuum sintering of Ti−Al−Si powder composites provides mostly the formation of the two-phase structure, but the quantitative ratio of the appeared phases can considerably differ from the calculated compositions. The lattice parameters in these phases are rather distorted. The analysis of the synthesis in the wave mode combustion of Ti−Al−Si powder composites shows that the synthesis completes only in the TiAl
3
+ Ti
5
Si
3
composite. This allows us to prepare the powder from the synthesized product. The paper analyzes the behavior of the synthesized powder based on the phase composition of the TiAl
3
+ Ti
5
Si
3
composite after the vacuum sintering of the powder compacts. It is found that after the 1300°C vacuum sintering of the SHS products based on the TiAl
3
+ Ti
5
Si
3
composite, its qualitative phase composition remains with a small change in the quantitative phase composition. The compaction of the SHS products is observed together with the reduction in the residual porosity.
Tunka-133: Results of 3 year operation Prosin, V.V.; Berezhnev, S.F.; Budnev, N.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2014, Letnik:
756
Journal Article
Recenzirano
Odprti dostop
The EAS Cherenkov light array Tunka-133, with ~3km2 geometric area, is taking data since 2009. The array permits a detailed study of cosmic ray energy spectrum and mass composition in the PeV energy ...range. After a short description of the methods of EAS parameter reconstruction, we present the all-particle energy spectrum and results of studying CR composition, based on 3 seasons of array operation. In the last part of the paper, we discuss possible interpretations of the obtained results.
Theoretical and experimental study of the synthesis of porous composites from powder mixtures for Ti-Si and Ti-Al-Si systems in the reaction sintering mode is carried out in the present work. The ...thermokinetic model of reaction sintering is formulated taking into account competing physicochemical stages. The model includes the heat balance equation, the kinetic equations for the components involved in the reactions, the kinetic equation for porosity changing during heating, reaction sintering, and cooling. The melting is assumed to occur within the temperature range of liquidity and solidus. These processes lead to the appearance of local stresses and volumetric changes. The results of experimental studies show good agreement with the numerical calculations.
The EAS Cherenkov light array Tunka-133, with ~ 3 km2 geometric area, is taking data since 2009.The array permits a detailed study of energy spectrum and mass composition of cosmic rays in the ...energy range from 6 · 1015 to 1018 eV. We describe the methods of time and amplitude calibration of the array and the methods of EAS parameters reconstruction. We present the all-particle energy spectrum, based on 7 seasons of operation.
Among the increasingly popular materials are composites combining the properties of metals and ceramic, and also the properties that result from the interaction of their dissimilar components. This ...paper provides a brief review of methods used to prepare components for synthesizing oxide-doped composites. The review is supplemented with experimental data on the sintering of Ti-based powder mixtures and with an analysis of physicochemical stages that may accompany the sintering of Ti–Al–Fe
2
O
3
and Ti–Fe–Al
2
O
3
powders of the same elemental composition under controlled heating. It is found that the sequence of phase formation stages depends on the factors of interparticle contacts. The sintering of powder mixtures composed of two metals and an oxide phase creates conditions for the formation of complex solutions (TiFeAl for Ti–Al–Fe
2
O
3
) and double oxides (FeAl
2
O
4
for Ti–Fe–Al
2
O
3
) and decreases the probability of intermetallic compound formation. Of importance for Ti–Al–Fe
2
O
3
is the mode of mixing as it determines the stages of mesoscale processes.
The structure and phase composition of (TiB)–Ti powder metal matrix composites synthesized by wave combustion with subsequent vacuum sintering are studied. The selected ratio of the reacting ...components correspond to the presence of unreacted titanium in the combustion products. The behavior of the SHS composite powders synthesized by vacuum sintering is estimated. An analysis of the volumetric and structural changes in the synthesized powder compacts demonstrates that at sintering temperatures of 1300–1350°С, no significant structure transformation occurs, and a slight decrease in the compact volume and the residual pore content is observed. A qualitative phase composition is maintained regardless of the amount of excess titanium and the selected temperature of sintering of the metal matrix composite. The vacuum sintering condition facilitates the redistribution of proportions of phases formed in a nonequilibrium state during synthesis. After sintering, the titanium diboride phase content decreases in favor of a more stable titanium monoboride.
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