Elongation mechanism of the ion shaping of embedded gold nanoparticles under swift heavy ion irradiation

The elongation process under swift heavy ion irradiation (74 MeV Kr ions) of gold NPs, with a diameter in the range 10-30 nm, and embedded in a silica matrix has been investigated by combining experiment and simulation techniques: three-dimensional thermal spike (3DTS), molecular dynamics (MD) and a phenomenological simulation code specially developed for this study. 3DTS simulations evidence the formation of a track in the host matrix and the melting of the NP after the passage of the impinging ion. MD simulations demonstrate that melted NPs have enough time to expand after each ion impact. Our phenomenological simulation relies on the expansion of the melted NP, which flows in the track in silica with modified (lower) density, followed by its recrystallization upon cooling. Finally, the elongation of the spherical NP into a cylindrical one, with a length proportional to its initial size and a width close to the diameter of the track, is the result of the superposition of the independent effects of each expansion/recrystallization process occurring for each ion impact. In agreement with experiment, the simulation shows the gradual elongation of spherical NPs in the ion-beam direction until their widths saturate in the steady state and reach a value close to the track diameter. Moreover, the simulations indicate that the expansion of the gold NP is incomplete at each ion impact.Peer reviewe

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Performance studies of the CMS strip tracker before installation

Peer reviewe

Ion-matter interaction: the three-dimensional version of the thermal spike model. Application to nanoparticle irradiation with swift heavy ions NA

International audienceIn the framework of swift heavy ion-matter interaction, the thermal spike has proved its worth for nearly two decades. This paper deals with the necessary refinement of the computation due to the kind of materials of interest, i.e. nanomaterials such as multilayered systems or composite films constituted of nanocylinders or nanospheres embedded in an insulating matrix. The three-dimensional computation of the thermal spike model is applied for the first time in the case of ions striking layers containing spherical nanoparticles embedded in a silica matrix. The temperature profiles calculated at each point (x, y, z) of the target for a total duration up to 10(-10) s and different values of ion impact parameter allow a possible explanation of the particle shape change under irradiation with swift heavy ions having an energy of several MeVamu(-1

Some feauters of current-voltage characteristics of irradiated GaP light diodes

Electrical characteristics of red and green GaP light diodes irradiated by fast electrons and neutrons were studied. It has been found that S-type current voltage curves, measured in current generator mode at low-temperature, show presence of fine structure. The mechanism of negative differential resistance formation and influence of radiation on current transport and relaxation mechanisms have been studied. Estimation of the effective cross-section for electron capture by recombination levels and its changes under irradiation were obtained from experimental data. Detailed study of radiation modification of GaP light diode parameters makes it possible to propose these devices as high sensitive sensors of gamma rays and electrons

BACTERIAL LYSATES OF ESCHERICHIA COLI STIMULATE PRODUCTION OF DEFENSINS BY PERIPHERAL BLOOD NEUTROPHILS

Aim. Study effect of a microbial-origin preparation based on Escherichia coli bacteria lysate (Uro-Vaksom) on defensin production (HNP1-3, lactoferrin - LF) and IgM/IgA in patients with recurring infections oflower urinary tract (RILUT). Materials and methods. 40 women with RILUT aged 18 - 68 years, who received monotherapy with Uro-Vaksom (bacterial lysate of 18 E. coli strains), and 26 healthy women were included into the study. Levels of defensins and immunoglobulins in blood were determined using ELISA (HNP1-3, LF, Elisa Kit, Hycult biotech, Netherlands; Serazym Human IgA, IgM, Germany). Rerate. A reduced level of defensins HNP1-3 and LF was noted in patients with RILUT, that gives evidence on chronical course of the inflammatory process on the organism. Use of E. coli lysate resulted in normalization of these parameters in blood sera of women. IgM and IgA levels in blood of the patients remained within normal values, and use of the bacterial lysate did not affect them. Conclusion. Use of Uro-Vaksom based on E. coli bacteria lysate has immune-correcting effect during therapy of patients with RILUT

Ion shaping of single-layer Au nanoparticles in amorphous silicon dioxide, in silicon nitride, and at their interface

International audienceWe present the shape transformation of a single layer of Au nanoparticles (NPs) when embedded in, and at the interface of, amorphous SiNx and SiOx (a−SiNx and a−SiOx) thin films upon irradiation with 185-MeV Au ions to fluences ranging from 0.3 to 30×1013cm−2. Transmission electron microscopy (TEM) and high angular annular dark field microscopy were used to study the ion-shaping process. The former allows us to follow the overall change in geometry, size, and structure, while the latter reveals information about the relative position with respect to the interface. For Au NPs embedded in a single material, a lower elongation rate for a−SiNx was found in comparison to a−SiOx. When at the interface of the two materials, TEM reveals a preferential elongation towards a−SiOx. The latter demonstrates the use of a−SiNx for confining the ion-shaping process within an intermediate a−SiOx layer. The simulation of the temperature evolution during a single-ion impact was used to understand the difference in elongation rates between a−SiNx and a−SiOx, as well as the asymmetric behavior when located at the interface using the three-dimensional inelastic thermal spike model with bulk thermophysical properties. The calculations show good agreement with the experimental observations and reveal a correlation between the thermal profile and the resulting NP geometry

Irradiation effects on thin epitaxial silicon detectors.

Radiation hardness of silicon detectors based on thin epitaxial layer on Czochralski (CZ) substrate for the LHC upgrade (Super-LHC) was studied. No type inversion was observed after irradiation by 24 GeV/c protons up to the fluence of 1016 p/cm2 due to overcompensating donor generation. After long-term annealing (corresponding to 500 days at room temperature) proton irradiated devices show a decrease of the effective doping concentration and then undergo type inversion. Measurements confirm that thin epitaxial devices on CZ substrate could be used for innermost layers of vertex detectors in future experiments at the Super-LHC