H.E.S.S.––the high energy stereoscopic system––is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m
2 mirror area for each of four telescopes, and photomultiplier ...cameras with a large field of view (5°) and small pixels (0.16°). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components––dish, mirrors, and Winston cones––as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.
Mirror facets of the high energy stereoscopic system imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the photomultiplier camera, viewed by a CCD camera. ...The alignment procedure works reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4° from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications.
Astropart.Phys.20:129-143,2003 Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are
aligned using stars imaged onto the closed lid of the PMT camera, viewed by a
CCD camera. The ...alignment procedure works reliably and includes the automatic
analysis of CCD images and control of the facet alignment actuators. On-axis,
80% of the reflected light is contained in a circle of less than 1 mrad
diameter. The spot widens with increasing angle to the telescope axis. In
accordance with simulations, the spot size has roughly doubled at an angle of
1.4 degr. from the axis. The expected variation of spot size with elevation due
to deformations of the support structure is visible, but is completely
non-critical over the usual working range. Overall, the optical quality of the
telescope exceeds the specifications.
Astropart.Phys.20:111-128,2003 H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large
imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for
each of four ...telescopes, and photomultiplier cameras with a large field of view
(5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to
provide good imaging properties over the full field of view, combined with
mechanical stability. The paper describes the design criteria and
specifications of the system, and the individual components -- dish, mirrors,
and Winston cones -- as well as their characteristics. The optical performance
of the telescope as a whole is the subject of a companion paper.
Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the PMT camera, viewed by a CCD camera. The alignment procedure works ...reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4 degr. from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications.
H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for each of four telescopes, and photomultiplier ...cameras with a large field of view (5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components -- dish, mirrors, and Winston cones -- as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.
In order to determine the required duration of whole-body exposure to extreme cold (−110 °C) in males and females for achieving the same cold-induced response, a mathematical model of skin cooling ...kinetics was developed. This modeling is derived from the implementation of a new experimental cryotherapy protocol to obtain continuous skin temperature maps over time. Each 3-min whole-body cryostimulation session was divided into six incremental sessions of 30 s carried out over six consecutive days. Seventeen young, healthy subjects (8 males aged 22.6 ±3.0 years and 9 females aged 23.7 ±4.7 years) agreed to participate in this study. The smallest sex-related difference in temperature was found in the trunk area (2.93 °C after 3 min) while the greatest temperature drop was found in the lower limbs (5.92 °C after 3 min). The largest temperature variation was observed between the trunk and the lower limbs, and peaked at 2.67 °C in males and 6.99 °C in females. For both sexes, skin cooling kinetics showed a strong transient exponential type decrease followed by linear regression behavior. It appeared that for achieving the same cold-induced response, the required duration of cryostimulation is longer for males. For example, a trunk skin cooling of −12 °C could be achieved in 125s for females vs 170s for males (+36% longer); for the lower limbs, the same skin cooling magnitude could be reached after 87s for females vs 140s for males (+62% longer).
With the increasing applications of nuclear technology, radiation protection has become very important especially for the environment and the personnel close to radiation sources. Natural clays can ...be used potentially for shielding the X-ray radiations. In this study, the correlation between structural parameters and radiation shielding performance of natural clay extracted from Algerian Sahara (Adrar, Reggan, and Timimoune) was investigated. Phase composition and structural parameters (lattice parameters, average crystallite size, and microstrain) were determined by the Rietveld refinements of X-ray diffraction patterns in the frame of HighScore Plus software. The obtained results showed that the studied clays are nanocrystalline (nano-clay) since the calculated crystallite size was ≈3 nm for the feldspar phase. FTIR spectra confirmed the presence of all phases already detected by XRD analysis besides Biotite (around the band at 3558 cm−1). The remaining bands corresponded to absorbed and adsorbed water (3432 cm−1 and 1629 cm−1, respectively) and atmospheric CO2 (2356 cm−1). The shielding properties (mass absorption coefficient—µ/ρ and radiative attenuation rate—RA) for (green-yellow, green, and red) clays of Adrar, (red, white, and white-red) clays of Reggan, and red clay of Timimoune at same energy level were examined. The results of clay samples were compared with each other. The obtained results indicated that the green clay of Adrar exhibited the superior radiation shielding, i.e., 99.8% and 243.4 cm2/g for radiative attenuation rate and mass absorption coefficient, respectively.
This study aims to investigate the impact of body heat loss on the thermal and aerodynamic conditions in a whole-body cryotherapy chamber. The underlying hypothesis is that the heat generated by the ...human body alters the thermal and aerodynamic environment inside the cabin. A numerical study was conducted to test this hypothesis and analyze the thermodynamic exchanges between the human body and the cabin during a 3 min whole-body cryotherapy session. The computational fluid dynamics (CFD) approach was used to study the unsteady heat transfer between the human body and the interior of the cryotherapy cabin. A thermal boundary condition, based on a mathematical model developed from experimental data, was applied to simulate skin cooling kinetics over time. The post-processing of the 3D results, including temperature, velocity fields, and thermal flux maps at the body surface, provided insight into the thermo-convective mechanisms involved in a whole-body cryotherapy session. The study found that body heat loss significantly affects the temperature fields inside the cabin, leading to global modifications of the aeraulic and thermal conditions. These findings suggest that cryotherapy protocols may need to be adjusted or the cabin set temperature optimized to enhance the therapeutic benefits.
Whole-body cryotherapy (WBC) is a therapeutic practice involving brief exposure to extreme cold, typically lasting one to four minutes. Given that WBC sessions often occur in groups, there is a ...hypothesis that cumulative heat dissipation from the group significantly affects the thermo-aerodynamic conditions of the cryotherapy chamber. Computational fluid dynamics (CFD) is employed to investigate thermal exchanges between three subjects (one man, two women) and a cryotherapy chamber at −92 °C during a 3-minute session. The investigation reveals that collective body heat loss significantly influences temperature fields within the cabin, causing global modifications in aerodynamic and thermal conditions. For example, a temperature difference of 6.7 °C was calculated between the average temperature in a cryotherapy chamber with a single subject and that with three subjects. A notable finding is that, under an identical protocol, the thermal response varies among individuals based on their position in the chamber. The aerodynamic and thermal characteristics of the cryotherapy chamber impact the heat released at the body’s surface and the skin-cooling rate needed to achieve recommended analgesic thresholds. This study highlights the complexity of physiological responses in WBC and emphasizes the importance of considering individual positions within the chamber for optimizing therapeutic benefits.
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