[en] The influence of interstellar He on the fragmentation of heavy cosmic rays in the interstellar medium (ISM) has long been a controversial subject. While H-induced cross section data are now avialable over broad mass and energy ranges, little data for He-induced fragmentation exists. With the recent reports of accurate measurements of the secondary/primary ratios in cosmic rays and of H-induced cross sections the problem of including interstellar He in propagation calculations becomes even more critical. As is argued the escape lengths lambda e deduced from the B/C+) and Sc-Cr/Fe ratios cannot be reconciled within the frame of a simple leaky box model assuming the ISM composed of pure H. It is quite remarkable that the discrepancy is especially large in the GeV region where (1) secondary/primary ratios measured by several groups agree fairly well and (2) fragmentation cross sections have been recently measured with good accuracy

[en] Pure electron capture nuclei synthesized during explosive events could, under special conditions, be present in the relativistic cosmic radiation, providing an opportunity to set limits on the time elapsed between nucleosynthesis and acceleration of cosmic-ray nuclei. In this respect, measurement of the cobalt abundance in relativistic cosmic rays seems the more promising test for the near future

No abstract available

[en] The time delay between the nucleosynthesis of the elements observed in the cosmic rays and the onset of their acceleration is of critical importance for the discussion of the origin of the cosmic radiation and will affect its composition. Fe, Co and Ni isotopes illustrate this point. The presence of iron group nuclei in the galaxy is believed to be mainly due to explosive nucleo-synthesis. This process does not produce iron directly, but the proton rich progenitors ⁵⁶Ni and ⁵⁷Ni. If these isotopes survive the ejection from the exploding star they decay to thei stable isobar. ⁵⁷Ni decays quickly to ⁵⁷Co, ⁵⁶Ni and ⁵⁷Co can only decay to ⁵⁶Fe and ⁵⁷Ni via electron capture with a half life of 6.1 days and 270 days respectively. If the cosmic rays are accelerated to relativistic energies quickly after their synthesis, these decay modes are prevented, leading to large differences in the Ni/Fe and Co/Fe ratio in the cosmic rays and the solar system abundances. From existing data on the nickel, cobalt and iron abundances in the cosmic rays it is concluded that more than a few weeks and most likely more than a year elapses between the synthesis of the cosmic ray nuclei and their acceleration

[en] If cosmic rays originate in a supernova explosion, they might be accelerated immediately after their synthesis. This would prevent electron-capture decay of unstable isotopes, and could result in large differences between cosmic-ray and solar-system abundances. Existing data on the abundances of iron, cobalt, and nickel in cosmic rays show great similarity to the solar system abundances, therefore, it is concluded that more than a year elapses between the synthesis of the cosmic-ray nuclei and their acceleration to relativistic energies. 2 figures

[en] Results of mean masses of cosmic rays at energy about 3 GeV/n, for Ne, Al, Mg, Si, S, Ca, and Fe, derived from high energy astronomy observatory 3 data collected by the Danish-French experiment C2 on board (HEAO-3) are presented. A method based upon comparison between observed transmission function and a predicted one computed from a geomagnetic field model was used. Enhancement factors of 2.9 + or - .7 for 22Ne/20Ne, 2.1 + or - .4 for (25Mg+26Mg)/24Mg, and 1.6 + or - .8 for (29Si+30Si)/28Si at GCRS when compared to LG were found

[en] We present results on mean masses of cosmic rays at energy about 3 GeV/n, for Ne, Al, Mg, Si, S, Ca and Fe, derived from the data collected by the Danish-French experiment C2 on board HEAO3. We used a method based upon comparison between observed transmission function and a predicted one computed from a geomagnetic field model. We find enhancement factors of 2.9+-.7 for 22 Ne/20 Ne, 2.1+-.4 for (25 Mg + 26 Mg)/24 Mg, and 1.6+-.8 for (29 Si + 30 Si)/28 Si at GCRS when compared to LG

No abstract available

[en] The data recorded by the C2 instrument on board the HEAO3 satellite improve our understanding of isotopic composition of heavy relativistic cosmic ray nuclei. The C2 counters and hodoscope combination is suitable for an accurate determination of momentum and arrival direction of individual cosmic rays. The next step in data analysis is to assign a cut-off rigidity value to each arrival direction with the help of a magnetic field model and to build the average transmission function for each element. This method is very useful for organizing data collected in a finite cut-off rigidity range, but in spite of its conceptual simplicity it does not allow to easily figure out how systematic and statistical errors propagate. Indeed the geomagnetic method does not separate isotopes in the usual sense: it is based on a comparison of the shape of the transmission to that of reference element. In this paper we describe an analysis of the observed transmission based on its comparison to expectation. For this we have selected oxygen nuclei with directions where the rigidity cut-off is > approximately 7 GV and can be considered sharp. We describe this selection and the cut-off assignment. We present the observed transmission and compare it to that calculated under the assumption of sharp cut-offs. This calculation takes into account the finite resolution of the counters. This allows to estimate to estimate the level of systematic errors. It is also shown that under sharp cut-off selection the transmission function for a single isotope is weakly dependent on charge and does not depend on the cut-off distribution, thus ensuring an unambiguous comparison to the reference element. In conclusion we use this technique to derive a tentative abundance of Neon isotopes

[en] The abundances of heavy cosmic ray nuclei at the solar system are calculated in a 3 dimension galactic model with cylindrical symmetry and with diffusive confinement. In this model the overabundance of ²²Ne is energy dependent. A comparison with HEAO data is suggestive of a radial dependent source of ²²Ne in the galaxy steeper than the source of the other heavy cosmic rays