F. Fessler

Bio: F. Fessler is an academic researcher from Karlsruhe Institute of Technology. The author has contributed to research in topics: KASCADE & Cosmic ray. The author has an hindex of 7, co-authored 15 publications receiving 303 citations.

Large-Scale Cosmic-Ray Anisotropy with KASCADE

Abstract: We present the results of an analysis of the large-scale anisotropy of cosmic rays in the PeV range. The Rayleigh formalism is applied to the right ascension distribution of extensive air showers measured by the KASCADE (Karlsruhe Shower Core and Array Detector) experiment. The data set contains about 108 extensive air showers in the energy range 0.7-6 PeV. No hints of anisotropy are visible in the right ascension distributions in this energy range. This accounts for all showers, as well as for subsets containing showers induced by predominantly light or heavy primary particles, respectively. Upper flux limits for Rayleigh amplitudes are determined to be between 10-3 at a primary energy of 0.7 PeV and 10-2 at 6 PeV.

A warm-liquid calorimeter for cosmic-ray hadrons

Abstract: An iron sampling calorimeter for cosmic-ray hadrons used in the centre of a large air shower experiment is described. The iron absorber is interspersed with eight layers of ionisation chambers filled with the room-temperature liquids tetramethylsilane and tetramethylpentane. Experiences gained from the calorimeter, its performance and long-term stability are presented. For energies in the TeV range shower profiles and transition curves have been measured and are compared with Monte Carlo calculations employing the FLUKA code. Good agreement has been found except in the lateral halo region. In the outer regions the energy deposition found is smaller than that obtained by the simulations.

Search for Cosmic-Ray Point Sources with KASCADE

Abstract: A survey of the northern hemisphere for astrophysical point sources with continuous emission of high-energy cosmic rays is presented Around 47 × 107 extensive air showers with primary energies above ≈300 TeV measured by the KASCADE detector field are selected for this analysis Besides the sky survey, a search for signal excess in the regions of the Galactic plane and of selected point-source candidates has been performed There is no evidence for any significant excess This is valid for an analysis of all recorded showers, as well as for a data set enhanced by γ-ray-induced showers An upper flux limit of around 3 × 10-10 m-2 s-1 for a steady point source that transits the zenith is obtained Additionally, the distribution of the arrival directions of extensive air showers with energies above 80 PeV was studied by an autocorrelation analysis

LOPES: detecting radio emission from cosmic ray air showers

Abstract: Radio pulses emitted in the Atmosphere during the air shower development of high-energy primary cosmic rays were measured during the late 1960ies in the frequency range from 2 MHz to 520 MHz. Mainly due to difficulties with radio interference these measurements ceased in the late 1970ies. LOFAR (Low Frequency Array) is a new digital radio interferometer under development. Using high bandwidth ADCs and fast data processing it it will be able to filter out most of the interference. By storing the whole waveform information in digital form one can analyze transient events like air showers even after they have been recorded. To test this new technology and to demonstrate its ability to measure air showers a "LOFAR Prototype Station" (LOPES) is set up to operate in conjunction with an existing air shower array (KASCADE-Grande). The first phase consisting of 10 antennas is already running. It operates in the frequency range of 40 to 80 MHz, using simple short dipole antennas and direct 2nd Nyquist sampling of the incoming wave. It has proven to be able to do simple astronomical measurements, like imaging of a solar burst. It has also demonstrated how digital interference suppression and beamforming can overcome the problem of radio interference and pick out air shower events.

About these proceedings

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Detection and imaging of atmospheric radio flashes from cosmic ray air showers

Abstract: The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.

The cosmic-ray experiment KASCADE

Abstract: KASCADE has been designed to measure air showers of primary cosmic-ray energies in the PeV region and to investigate the knee phenomenon in the all-particle energy spectrum. Several observations are measured simultaneously for each event by different detector systems. The experiment started to take data in 1996 and has been completed and extended since then. The individual detector systems and their performances are described. Also, the experience in long-term operation of the experiment and the interplay between different components is outlined.

On the knee in the energy spectrum of cosmic rays

Abstract: Results from direct and indirect measurements of cosmic rays are reviewed. Emphasis is given to the understanding of the knee in the energy spectrum. The data are compared to contemporary models for the knee. Implications on the present understanding of the origin of galactic cosmic rays are discussed.