J.P. Stoquert

Irradiations of implanted cobalt nanoparticles in silica layers

Abstract Cobalt ions have been implanted at an energy of 160 keV at fluences of 2×10 16 , 5×10 16 and 10 17 Co + xa0cm −2 in silica layers and at temperatures of 77, 295 and 873 K. The nanocomposites formed have further been irradiated with electrons and swift heavy ions. Magnetic properties of the nanoparticles studied by a SQUID magnetometer at 295 and 5 K have been related to the modification of particle size and size distribution, which have been observed by transmission electron microscopy.

Carbon sputtering of polymer-like amorphous carbon by swift heavy ions

Abstract Thin films of “polymer-like” deuterated amorphous carbon have been irradiated at GANIL (Caen, France) by several swift heavy ion beams : S, Ar, Nb, Sn, Pb and U in the energy range between 2 and 10 MeV/amu, covering the electronic stopping power (Se) range between 1 and 13 keV/nm. Using Rutherford backscattering spectrometry, the carbon content remaining in the film has been determined versus fluence for several values of Se. The deduced yield of carbon sputtering increases significantly above a Se threshold value of 2.5xa0±xa01.0 keV nm−1, which is larger than the Se threshold value of deuterium effusion (0.75xa0±xa00.35 keV nm−1). Using the thermal spike model, an effective temperature around 2800 K is defined for carbon sputtering in polymer-like amorphous carbon in the Se regime.

Detailed investigations of shower formation in Ge- and W-crystals traversed by 40–287 GeV/c electrons

Abstract The development of electromagnetic cascades along crystalline directions have for the first time been measured. As compared to random incidence the number of produced particles is enhanced more than 10 times along axial directions in Ge and increasing with particle energy. The critical angle for this strongly enhanced shower formation is around 1 mrad which means that the effect could be harnessed for high-resolution gamma-ray telescopes.

Electronic stopping power threshold of damage creation in yttrium iron garnet

Abstract Electronic stopping power threshold of damage creation in yttrium iron garnet (YIG) has been determined by extrapolation using the known model for nuclear and electronic damage creation calibrated by 2 MeV alpha and 510 MeV argon irradiations respectively. This value is equal 4.5

Crystallization of ultrathin W-Si multilayer structures by high-energy heavy ion irradiations

1.0 keV/nm and its is three times lower than the dE/dx value at which chemical etching appears indicating that electronic stopping power damage can exist at very low value of dE/dx for non radiolytic insulating materials.

Slowing down of heavy ions in solids near the stopping power maximum

Ultrathin amorphous multilayers structures (1.55 nm bilayer period) were irradiated by high‐energy heavy ion (127I and 238U ions). Transmission electron microscopy study shows that the ion‐material interaction in such a configuration leads to an irreversible transformation of the initial amorphous structures. In this letter, we report the first observation of the crystallization of the multilayers induced by the heavy ion irradiations with a subsequent formation of a new WSi structure. The crucial role of the electronic effects in the crystallization process is discussed relatively to the other phenomena induced under the ion irradiation.

Instability and structural transformation of amorphous ultra-thin W-Si multilayer structures during heavy ion irradiation

Abstract We have measured energy losses of C, O, Al, Cu, Ti, I, Ag and Au ions in absorbers of C, Al, Cu, Ag, Ta and Au in the region of the stopping power maximum by using secondary ions produced by primary incident beams of 127 I (240 MeV) and 197 Au (200 MeV). Different corrections due to the effective charge and to the high order Barkas and Bloch terms are discussed and compared with the experimental data.

Energy loss straggling of protons and He ions in gold from 0.1 to 1.0 MeV/u

Abstract The W-Si multilayer structure behaviour after high-energy heavy-ion irradiation has been investigated by transmission electron microscopy and electron diffraction. The results show modifications of the initial amorphous multilayers and the formation of a new W-Si crystalline structure after ion passages. The interpretation of the results is based upon an interfacial reaction induced by the heavy ions.

Swift heavy ions in magnetic insulators: A damage-cross-section velocity effect

Abstract Energy loss straggling of protons (atomic and molecular beams) and He ions in gold has been measured in the region of the stopping power maximum with a high resolution electrostatic analyser. The results are compared with the predictions of Bethe-Livingston and Lindhard-Scharff theories. Contributions from additional stragglings are investigated in solids, where they are of practical interest. Some results for energy loss and straggling of 14N and 16O ions in the range 20 keV/u to 60 keV/u are also given and compared to the velocity proportional theory.