We present results of the monitoring method we have used to characterize the optical performance deterioration due to the dust of our mirror segments produced for fluorescence detectors used in ...astrophysics experiments. The method is based on the measurement of scatter profiles of reflected light. The scatter profiles and the reflectivity of the mirror segments sufficiently describe the performance of the mirrors from the perspective of reconstruction algorithms. The method is demonstrated on our mirror segments installed in frame of the Pierre Auger Observatory project. Although installed in air-conditioned buildings, both the dust sedimentation and the natural aging of the reflective layer deteriorate the optical throughput of the segments. In the paper, we summarized data from ten years of operation of the fluorescence detectors. During this time, we periodically measured in-situ scatter characteristics represented by the specular reflectivity and the reflectivity of the diffusion part at the wavelength of 670 nm of the segment surface (measured by means of the optical scatter technique as well). These measurements were extended with full Bidirectional Reflectance Distribution Functions (BRDF) profiles of selected segments made in the laboratory. Cleaning procedures are also discussed in the paper.
A measurement of the absolute fluorescence yield of the 337 nm nitrogen band, relevant to ultra-high energy cosmic ray (UHECR) detectors, is reported. Two independent calibrations of the fluorescence ...emission induced by a 120 GeV proton beam were employed: Cherenkov light from the beam particle and calibrated light from a nitrogen laser. The fluorescence yield in air at a pressure of 1013 hPa and temperature of 293 K was found to be Y 337 = 5.61 +/- 0.06 stat +/- 0.22 syst photons/MeV. When compared to the fluorescence yield currently used by UHECR experiments, this measurement improves the uncertainty by a factor of three, and has a significant impact on the determination of the energy scale of the cosmic ray spectrum.
The bright optical flash from GRB 060117 Jelínek, M.; Prouza, M.; Kubánek, P. ...
Astronomy and astrophysics (Berlin),
08/2006, Letnik:
454, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present a discovery and observation of an extraordinarily bright prompt optical emission of the GRB 060117 obtained by a wide-field camera atop the robotic telescope FRAM of the Pierre Auger ...Observatory from 2 to 10 min after the GRB. We found rapid average temporal flux decay of $\alpha = -1.7 \pm 0.1$ and a peak brightness $R = 10.1$ mag. Later observations by other instruments set a strong limit on the optical and radio transient fluxes, unveiling an unexpectedly rapid further decay. We present an interpretation featuring a relatively steep electron-distribution parameter $p \simeq 3.0$ and providing a straightforward solution for the overall fast decay of this optical transient as a transition between reverse and forward shock.
The possibility of detection of some features of high energy particle interactions with detectors placed at medium depths underground through studies on high energy muons is studied. These muons ...carry information about the early interactions occurring during the development of the hadron cascade near the top of the atmosphere. They might reveal the effects resulting from creation of quark gluon plasma in interactions of ultra high energy cosmic ray iron nuclei with air nuclei.
The DELPHI detector at Large Electron-Position collider (LEP) at CERN near Geneva, has been used to detect multi-muon bundles originated from cosmic ray interactions in the atmospheres. The muon ...multiplicity distribution has been measured over a wide range of multiplicities. The cosmic events registered during the years 1999 and 2000 correspond roughly to 1.6 10
6
s of effective run time. This paper provides a preliminary comparison between the data and a prediction of the QGSJET model implemented to the CORSIKA simulation package.
A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time ...resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper refers to the construction and utilization of the chamber that has been used for measurement of fluorescence yield within the frame of the project AIRFLY. The chamber was designed to ...simulate some physical conditions in high levels of the atmosphere, particularly pressure, temperature and humidity. The aim of the AIRFLY (AIR FLuorescence Yield) project is to simulate and to measure the process of the fluorescence and Cherenkov emission produced by impact of high-energy cosmic rays (UHECR) on molecules of nitrogen in high levels of the atmosphere. This is required for calibration of fluorescence detectors (FDs) dedicated for monitoring particles of these energies by means of fluorescence measurements.
The fluorescence detection of ultra high energy (≳10
18
eV) cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules, which are excited by the cosmic ray ...shower particles along their path in the atmosphere. We have made a precise measurement of the fluorescence light spectrum excited by MeV electrons in dry air. We measured the relative intensities of 34 fluorescence bands in the wavelength range from 284 to 429
nm with a high resolution spectrograph. The pressure dependence of the fluorescence spectrum was also measured from a few hPa up to atmospheric pressure. Relative intensities and collisional quenching reference pressures for bands due to transitions from a common upper level were found in agreement with theoretical expectations. The presence of argon in air was found to have a negligible effect on the fluorescence yield. We estimated that the systematic uncertainty on the cosmic ray shower energy due to the pressure dependence of the fluorescence spectrum is reduced to a level of 1% by the AIRFLY results presented in this paper.
The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, ...corresponding to altitudes typical of the cosmic ray shower development in the atmosphere. We have studied the temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air. Results for the 313.6, 337.1, 353.7 and 391.4
nm bands are reported in this paper. We found that the temperature and humidity dependence of the quenching process changes the fluorescence yield by a sizeable amount (up to 20% for the temperature dependence in the 391.4
nm band) and its effect must be included for a precise estimation of the energy of ultra high energy cosmic rays.
The knowledge of the fluorescence emission as a function of atmospheric parameters is essential for the detection of extensive air showers with the fluorescence technique. In this paper, we summarize ...AIRFLY published measurements of the pressure dependence of the fluorescence yield. The spectral distribution of the fluorescent light between 280 and 429
nm has been measured with high resolution. Relative intensities of 34 spectral lines have been determined. The pressure dependence of 25 lines was measured in terms of quenching reference pressures
p
λ
′
in air. This set of AIRFLY measurements yields the most comprehensive parametrization of the pressure dependence of the fluorescent spectrum.
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