SPORT: A new sub-nanosecond time-resolved instrument to study swift heavy ion-beam induced luminescence - Application to luminescence degradation of a fast plastic scintillator

We developed a new sub-nanosecond time-resolved instrument to study the dynamics of UV-visible luminescence under high stopping power heavy ion irradiation. We applied our instrument, called SPORT, on a fast plastic scintillator (BC-400) irradiated with 27-MeV Ar ions having high mean electronic stopping power of 2.6 MeV/\mu m. As a consequence of increasing permanent radiation damages with increasing ion fluence, our investigations reveal a degradation of scintillation intensity together with, thanks to the time-resolved measurement, a decrease in the decay constant of the scintillator. This combination indicates that luminescence degradation processes by both dynamic and static quenching, the latter mechanism being predominant. Under such high density excitation, the scintillation deterioration of BC-400 is significantly enhanced compared to that observed in previous investigations, mainly performed using light ions. The observed non-linear behaviour implies that the dose at which luminescence starts deteriorating is not independent on particles' stopping power, thus illustrating that the radiation hardness of plastic scintillators can be strongly weakened under high excitation density in heavy ion environments.Comment: 5 figures, accepted in Nucl. Instrum. Methods

An electrospray ionisation apparatus for gas phase study of biomolecules

International audienceSynopsis A set-up to study large biomolecules in the gas phase based on an ElectroSpray Ionisation source has been installed at CNR-ISM in Rome, and it is currently under commissioning. Accurate ion optics simulation provide crucial feedback in the understanding and optimisation of its performance

Analgesic efficacy and haemodynamic effects of nefopam in critically ill patients

International audienc

High-resolution x-ray spectroscopy to probe quantum dynamics in collisions of Ar17+, 18(+) ions with atoms and solids, towards clusters

International audienceWe report on studies of projectile excited states produced by electron capture in both low and high velocity regimes, and when highly charged ions (HCIs) collide either with dilute or dense matter. Quantum effects in the interaction dynamics are probed via high-resolution x-ray spectroscopy for Ar17+ at 7 keV u(-1) and for Ar18+ at 13.6 MeV u(-1) on Ar, N-2 or CH4 gas targets and on carbon solid foils. Relevant comparison between those two collision velocity regimes, and between gaseous and solid targets reveal specific features. In particular, the effect of multiple capture process occurring within a single-collision with gaseous target can be compared with the consequence of multistep collisions arising at surfaces and in solid-bulk at low velocity. At high velocity, beside evidence for collective response of the target electrons due to the wake field induced by HCI passing through the solid-bulk, we demonstrate that excitation and ionization collision processes damp the populations of projectile excited states for long ion transit times. The evolution of the np population as a function of n in solid is at variance from the 1/n(3) law found in gas, and the disagreement increases with solid target thickness. We have also tackled studies of HCIs in collision with clusters showing that x-ray spectroscopy provides a powerful tool to sign the presence of clusters in a supersonic gas jet

Transport of fast excited ions through thin solids probed by X-ray spectroscopy

International audienceOver more than a decade, experimental studies of the production and transport of projectile excited states in thin solid targets have been performed at GANIL for Ar17+ and Kr35+ in the so-called high velocity domain. A range of target thicknesses from single collision condition to equilibrium has been investigated. X-ray spectroscopy techniques have allowed us to determine absolute nℓ populations of core and Rydberg projectile states, as well as the relative population of fine structure substates (nℓj). In parallel, theoretical simulations to treat on the same footing all the competing processes, i.e., collisions, radiative decay and dynamical screening due to the wake field, have been developed. Methods based on either master equations or Monte Carlo approaches have allowed us to reach an unprecedented precision in the description of the ion transport in matter in the perturbative regime. In particular, a first direct measurement of the wake field usually extracted from ion stopping power has been performed

Polymers degradation under radiolysis : experimental adaptations of devices for irradiating samples dedicated to analytical methods perspectives.

International audienceThe degradation of polymers under irradiation leads, to gas emission, and, to chemical modifications of the polymer backbone. The determination of reliable radiation chemical yields of these modifications requires the management of many different parameters, such as irradiation nature, dose, dose rate, temperature, surrounding atmosphereFor determining those chemical yields the use of analytical devices creates other constraints to deal with, such as detection limits, or samples transfers to the detector. In the LRMO laboratory, studies are realized in the context of the nuclear safety, to evaluate risks of degradation under radiolysis of the organic materials in the nuclear wastes during conditioning, transport, storage and final disposal in French deep underground repository. In these conditions, different emitters are encountered, as well as very high doses. Depending on the researched parameter, the realization of specific irradiation devices can be required with controlled atmospheres. Some devices can be batches closed vessels, or dynamic vessels for solutions, within the objective to determine radiation chemical yields under non usual conditions (very high doses up to several MGy, high temperature, under acidic atmosphere).The various glass vessels solutions, as well as the specific environment inside the vessels, for analytical methods, and for dose deposition will be presented.Moreover, many analytical tools are available, as a function of the modification that has to be evaluated. High resolution gas mass spectrometry, allowing differentiation between CO and N2 can be used for gases radiation chemical yields determination. In the case of the polymer backbone modification or for organic molecules release studies, mass spectrometers with different sources or coupled analytical techniques such as GC-MS or LC-MS can be employed. The direct measurements on irradiated polymers using FTIR methods and ATG-DSC.This poster will present some experimental devices developed in the laboratory and the connection to analytical tools

Optical properties of synthetic carbon nanoparticles as model of cosmic dust

International audienceCarbon nanoparticles synthesised by laser pyrolysis of small hydrocarbons are deposited at low energy on a silicon substrate. Infrared spectroscopy of the as-formed films are studied as a function of the synthesis parameters and post-treatments, such as annealing and heavy ion irradiation. Correlation between infrared spectroscopy and multiscale organisation of the samples is made through transmission electron microscopy, including image analysis. Changes in infrared spectra are analysed in terms of the carbon network building. The relevance of the results to model the structure and spectroscopy of carbon dust in the carbon-rich circumstellar media is discussed

Multielectron processes in heavy ion-atom collisions at intermediate velocity

International audienceUsing high resolution x-ray spectroscopy, we have measured projectile electron single and multiple cross sections when a two-electron Ar16+ ion collides with neutral target atoms. For a fixed impact velocity (vp = 23 a.u.), but using various targets from He to Xe, a range from the perturbative regime to the strong interaction regime has been investigated. Double excitation cross sections are found to be well reproduced by an independent electron model. First measurements of capture-ionization cross sections are also reported and show the importance of this often-neglected process

Polymers degradation under radiolysis : experimental adaptations of devices for irradiating samples dedicated to analytical methods perspectives.

International audienceThe degradation of polymers under irradiation leads, to gas emission, and, to chemical modifications of the polymer backbone. The determination of reliable radiation chemical yields of these modifications requires the management of many different parameters, such as irradiation nature, dose, dose rate, temperature, surrounding atmosphereFor determining those chemical yields the use of analytical devices creates other constraints to deal with, such as detection limits, or samples transfers to the detector. In the LRMO laboratory, studies are realized in the context of the nuclear safety, to evaluate risks of degradation under radiolysis of the organic materials in the nuclear wastes during conditioning, transport, storage and final disposal in French deep underground repository. In these conditions, different emitters are encountered, as well as very high doses. Depending on the researched parameter, the realization of specific irradiation devices can be required with controlled atmospheres. Some devices can be batches closed vessels, or dynamic vessels for solutions, within the objective to determine radiation chemical yields under non usual conditions (very high doses up to several MGy, high temperature, under acidic atmosphere).The various glass vessels solutions, as well as the specific environment inside the vessels, for analytical methods, and for dose deposition will be presented.Moreover, many analytical tools are available, as a function of the modification that has to be evaluated. High resolution gas mass spectrometry, allowing differentiation between CO and N2 can be used for gases radiation chemical yields determination. In the case of the polymer backbone modification or for organic molecules release studies, mass spectrometers with different sources or coupled analytical techniques such as GC-MS or LC-MS can be employed. The direct measurements on irradiated polymers using FTIR methods and ATG-DSC.This poster will present some experimental devices developed in the laboratory and the connection to analytical tools