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Results for “COSMIC RADIATION”

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At least 667 records · Page 37Linked to original sources
PubMed2002

Monte Carlo calculation of the radiation field at aircraft altitudes.

Energy spectra of secondary cosmic rays are calculated for aircraft altitudes and a discrete set of solar modulation parameters and rigidity cut-off values covering all possible conditions. The calculations are based on the Monte Carlo code FLUKA and on the most recent information on the interstellar cosmic ray flux including a detailed model of solar modulation. Results are compared to a large variety of experimental data obtained on the ground and aboard aircraft and balloons, such as neutron, proton, and muon spectra and yields of charged particles. Furthermore, particle fluence is converted into ambient dose equivalent and effective dose and the dependence of these quantities on height above sea level, solar modulation, and geographical location is studied. Finally, calculated dose equivalent is compared to results of comprehensive measurements performed aboard aircraft.

Aircraft↗
PubMed1993

Responses of Bacillus subtilis spores to space environment: results from experiments in space.

Onboard of several spacecrafts (Apollo 16, Spacelab 1, LDEF), spores of Bacillus subtilis were exposed to selected parameters of space, such as space vacuum, different spectral ranges of solar UV-radiation and cosmic rays, applied separately or in combination, and we have studied their survival and genetic changes after retrieval. The spores survive extended periods of time in space--up to several years--, if protected against the high influx of solar UV-radiation. Water desorption caused by the space vacuum leads to structural changes of the DNA; the consequences are an increased mutation frequency and altered photobiological properties of the spores. UV-effects, such as killing and mutagenesis, are augmented, if the spores are in space vacuum during irradiation. Vacuum-specific photoproducts which are different from the 'spore photoproduct' may cause the synergistic response of spores to the simultaneous action of UV and vacuum. The experiments provide an experimental test of certain steps of the panspermia hypothesis.

Bacillus subtilis↗
PubMed2001

Calculation of the radiation environment caused by galactic cosmic rays for determining air crew exposure.

The spectra of secondary particles resulting from interactions of primary galactic cosmic rays with the nuclei in the atmosphere have been calculated using the Monte Carlo transport code FLUKA. The simulations have been carried out at solar minimum and solar maximum activity, for several values of the vertical geomagnetic cut-off. The effective dose rate and the ambient dose equivalent rate as a function of geomagnetic cut-off and altitude have been obtained using appropriate sets of conversion coefficients. The calculated results are discussed and compared with experimental data and other calculations. A simple method is proposed to calculate the radiation exposure at aircraft altitudes.

Aircraft↗
PubMed2002

Measurement for the dose-rates of the cosmic-ray components on the ground.

In this study, we aimed to measure the directly ionizing component (muons and photons) and the indirectly ionizing component (neutrons) of the cosmic-ray spectra and evaluate their dose rate contribution to the total dose rate on a ground level in Japan. Measurements were carried out in Tohoku University, Japan, from October 2000. The pulse-height spectra of the cosmic-ray photons and muons were measured with a 12.7 cm diameter and 12.7 cm long NaI(Tl) scintillation detector. In order to measure energy spectra of cosmic-ray photons and muons, response functions of the detector to photons and muons were determined by the Monte Carlo simulation codes. The cosmic-ray photon dose was evaluated directly from the measured pulse-height spectrum by using the spectrum weight function, and the cosmic-ray muon dose was evaluated by converting the measured pulse height spectrum into deposited energy within the detector. The quantity of the cosmic-ray electrons is estimated to be very small and is not taken into account in this study. The cosmic-ray neutron spectrum and the neutron dose were measured by using a multi-moderator spectrometer (Bonner ball) and a rem counter. The measurements could finally give the annual absorbed dose in tissue of the cosmic-ray muons of 315 microSv/y and annual ambient doses of the cosmic-ray photons and neutrons on the ground in Japan of 55 microSv/y and 31 microSv/y, respectively.

Background Radiation↗
PubMed1968

Natural radiation.

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Alpha Particles↗