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BS EN ISO 20785-1:2017 pdf free

BS EN ISO 20785-1:2017 pdf free.Dosimetry for exposures to cosmic radiation in civilian aircraft
The primary galactic cosmic radiation (and energetic solar particles) interact with the atomic nuclei of atmospheric constituents, producing a cascade of interactions and secondary reaction products that contribute to cosmic radiation exposures that decrease in intensity with depth in the atmosphere from aviation altitudes to sea level.[5][6] Galactic cosmic radiation (GCR) can have energies up to 1020 eV, but lower energy particles are the most frequent. After the GCRs penetrate the magnetic field of the solar system, the peak of their energy distribution is at a few hundred MeV to 1 GeV per nucleon, depending on solar magnetic activity, and the spectrum follows a power function of the form E -2,7 eV up to 1015 eV;above that energy, the spectrum steepens to E-3 eV. The fluence rate of GCR entering the solar system is fairly constant in time, and these energetic ions approach the Earth isotropically.
The magnetic fields of the Earth and sun alter the relative number of GCR protons and heavier ions reaching the atmosphere. The GCR ion composition for low geomagnetic cut-off and low solar activity is approximately 90 % protons, 9 % He ions, 1 % heavier nuclei; at a vertical cut-off of 15 GV, the composition is approximately 83 % protons, 15 % He ions, and nearly 2 % heavier ions.[7][8]
The changing components of ambient dose equivalent caused by the various secondary cosmic radiation constituents in the atmosphere as a function of altitude are illustrated in Figure 1. At sea level, the muon component is the most important contributor to ambient dose equivalent and effective dose; at aviation altitudes, neutrons, electrons, positrons, protons, photons, and muons are the most significant components. At higher altitudes, nuclear ions heavier than protons start to contribute. Figures showing representative normalized energy distributions of fluence rates of all the important particles at low and high cut-offs and altitudes at solar minimum and maximum are shown in Annex A.BS EN ISO 20785-1 pdf download.

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