Irradiation cosmic rays

Extraterrestrial dust particles can be proven to be nonterrestrial by a variety of methods, depending on the particle si2e. Unmelted particles have high helium. He, contents resulting from solar wind implantation. In 10-)J.m particles the concentration approaches l/(cm g) at STP and the He He ratio is close to the solar value. Unmelted particles also often contain preserved tracks of solar cosmic rays that are seen in the electron microscope as randomly oriented linear dislocations in crystals. Eor larger particles other cosmic ray irradiation products such as Mn, Al, and Be can be detected. Most IDPs can be confidently distinguished from terrestrial materials by composition. Typical particles have elemental compositions that match solar abundances for most elements. TypicaUy these have chondritic compositions, and in descending order of abundance are composed of O, Mg, Si, Ee, C, S, Al, Ca, Ni, Na, Cr, Mn, and Ti. 

The instrument MIMOS 11 is extremely miniaturized compared to standard laboratory Mossbauer spectrometers and is optimized for low power consumption and high detection efficiency (see Sect. 3.3) and [326, 327, 336-339]. All components were selected to withstand high acceleration forces and shocks, temperature variations over the Martian diurnal cycle, and cosmic ray irradiation. Mossbauer measurements can be done during day and night covering the whole diurnal temperature... 

The method assumes that the average cosmic ray flux has been constant over the mean-life of 81Kr (t81 + 3.07 x 105y) and over the overall exposure time of the sample cosmic rays. Furthermore, it is assumed that the exposure geometry has remained fixed over the period of irradiation, but no other assumptions are made regarding shielding. 

Nishiizumi, K., Regnier, S., and Marti, K., "Cosmic ray exposure ages of chondrites, pre-irradiation and constancy of cosmic ray flux in the past, 1980, Earth Planet. Sci. Lett., 50, 156-170. 

Turner, G. (1972). 40Ar-39Ar age and cosmic ray irradiation history of the Apollo 15 anorthosite 15415. Earth Planet. Sci. Letters, 14, 169-75. 

Molecular evolution which occurs preferentially in a very cold, dilute medium, permanently irradiated by diehard cosmic rays and photons. A tremendous variety of relatively complex molecules has already been produced, but it seems to have stopped well before the creation of interstellar life. 

X-ray diffraction, 39 160-161, 164-165 Radial factor, 22 214-218 Radiation, see also Irradiation cosmic, see Cosmic radiation terrestial origin, 3 288-293 Radiation chemistry, heterogeneous kinetics of, 3 198-203... 

Artificial satellites, which are now used for communication, broadcast, weather forecast, etc., are equipped with a variety of semiconductor devices, which are often exposed to the high levels of radiation found in space. Such energetic particles, called cosmic rays, cause the degradation and malfunction of semiconductor devices, which lowers both the mission lifetime and reliability of satellites. Using ion beam irradiation facilities at TIARA, which have been uniquely adapted for simulating the radiation environment of space, we have... 

Cosmic-ray exposure ages are determined from spallation-produced radioactive nuclides. Cosmic-ray irradiation normally occurs while a meteoroid is in space, but surface rocks unshielded by an atmosphere may also have cosmogenic nuclides. These measurements provide information on orbital lifetimes of meteorites and constrain orbital calculations. Terrestrial ages can be estimated from the relative abundances of radioactive cosmogenic nuclides with different half-lives as they decay from the equilibrium values established in space. These ages provide information on meteorite survival relative to weathering. 

Eugster, O., Herzog, G. F., Marti, K. and Caffee, M. W. (2006) Irradiation records, cosmic-ray exposure ages, and transfer time of meteorites. In Meteorites and the Early Solar System II, eds. Lauretta, D. S. and McSween, H. Y., Jr. Tucson University of Arizona Press, pp. 829-851. A good summary of what is known about cosmic-ray exposure ages and the transfer of meteorites from the asteroid belt to Earth. 

Noble gas isotopes are also produced through irradiation by cosmic rays. These rays are mostly high-energy protons that produce a cascade of secondary particles when they bombard other target nuclei, in a process called spallation. Neon produced by spallation reactions has similar abundances of all three isotopes (Fig. 10.8). Cosmic-ray irradiation occurs on the surfaces of airless bodies like the Moon and asteroids, as well as on small chunks of rock orbiting in space. Using these isotopes, it is possible to calculate cosmic-ray exposure ages, as described in Chapter 9. 

In INAA, a rock or mineral sample is irradiated in the reactor. The irradiated sample is removed from the reactor, and the dangerous radioactivities are allowed to decay. Then the sample is placed into a counter and the y-rays emitted by each element in the sample are counted. A variety of counters are used, including scintillation counters, gas ionization counters, or semi-conductor counters. For the most precise results, background counts in the detectors produced by electronic noise, cosmic rays, and other radioactive decays must be eliminated. The technique is very sensitive, and samples as small as a few tens of milligrams can be measured. 

In his intervention Blackett treated the discovery of the positron in cosmic rays by C. D. Anderson in 193246 and its confirmation by Blackett and Occhialini,47 who had introduced, for the first time, the technique of triggering a vertical cloud chamber by means of the coincidence between two Geiger counters, one placed above, the other below the chamber. Blackett also discussed a number of papers by Meitner and Philipp, Curie-Joliot, Blackett, Chadwick and Occhialini, and Anderson and Nedder-meyer,48 all appearing almost at the same time, on the production of positrons in various elements irradiated with the -/-rays of 2.62 MeV energy of The. These were the first observations of electron-positron pair production. He also pointed out that the observed production of positrons has a cross section larger than the nuclear dimensions, and therefore, most probably, does not originate from a nuclear process. 

The significance of radioactivity in water, food, and air has been under particular scrutiny since the advent of nuclear bomb tests and their accompanying radioactive fallout. This scrutiny has resulted in much documented data gathered over the past few decades on the health characteristics of man under various environmental conditions, such as the Denver populace who are subjected to more intense cosmic ray irradiations than the New York City populace the radium dial workers of the 1920,s who have provided data on life spans, general health, and causes of death population s drinking water with varying radium contents persons living... 

The recent detection of the [Nell] line emission at 12.81 pm from several disks by the Spitzer Space Telescope (e.g. Pascucci et al. 2007) has confirmed theoretical predictions that the disk atmosphere is heavily ionized and superheated, either by X-rays (Glassgold et al. 2007) or by extreme UV irradiation (Pascucci et al. 2007). However, X-rays and cosmic-ray particles (CRPs) may not be able to penetrate further toward the mid-plane of the planet-forming disk zone (r 3-20 AU), which makes the mid-plane essentially neutral and thus stable against accretion ( Dead Zone Gammie 1996 Dolginov Stepinski 1994). 

Table 1 summarizes some of the important properties of the carbon isotopes. Note that only the rare ( 1%), naturally occurring, stable carbon isotope, namely, C, has a nuclear spin and is observable by NMR. The organic chemist is fortunate that 99% of natural carbon is the isotope C with no nuclear spin, so that proton and carbon-13 NMR spectra of organic compounds are not complicated by spin - spin splitting arising fi om adjacent carbon atoms. The radioisotope C is made by thermal neutron irradiation of lithium or aluminum nitride (equation 1). It decays back to stable yN by jS emission, with a half-life of 5570 years (equation 2). Cosmic rays generate thermal neutrons, which leads to the formation of C02 in the atmosphere (equation 1). Metabolism of... 

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