Charge-state distribution of Li ions from the β\beta decay of laser-trapped 6^{6}He atoms

Background: The accurate determination of atomic final states following nuclear $\beta$ decay plays an important role in many experiments. In particular, the charge state distributions of ions following nuclear $\beta$ decay are important for determinations of the $\beta-\nu$ angular correlation with improved precision. Purpose: Our measurement aims at providing benchmarks to test theoretical calculations. Method: The kinematics of Li$^{n+}$ ions produced following the $\beta$ decay of $^6{\rm He}$ within an electric field were measured using $^6{\rm He}$ atoms in the metastable $(1s2s,~{^3S_1})$ and in the $(1s2p,~{^3P_2})$ states confined by a magneto-optical trap. The electron shake-off probabilities were deduced including their dependence on ion energy. Results: We find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation and discuss a plausible explanation. We also point out that there is no explanation for a large discrepancy between the same calculation and a previous measurement of the Li-ion energy dependence of the charge distribution from decays of the electronic ground state

Electron Capture in Collisions of Slow Highly Charged Ions with an Atom and a Molecule: Processes and Fragmentation Dynamics

International audienceProcesses involved in slow collisions between highly charged ions (HCI) and neutral targets are presented. First, the mechanisms responsible for double electron capture are discussed. We show that, while the electron-nucleus interaction is expected to be dominant at projectile velocities of about 0.5 a.u., the electron-electron interaction plays a decisive role during the collision and gains importance when the projectile velocity decreases. This interaction has also to be invoked in the capture of core electrons by HCI. Finally, the molecular fragmentation of H2 following the impact of HCI is studied

Measurement of the Li8 half-life

We report a new measurement of the Li8 half-life using a plastic scintillator and an ultrafast waveform digitizing module. The result, T1/2=(838.40±0.36)ms, improves by a factor of 2.5 the most precise result obtained so far and is furthermore deduced with negligible corrections due to dead time.Ministerio de Ciencia e Innovación FPA2008-0468

Gaseous emissions (building, storage, pasture) of dairy systems combining or not grazing and housing

Session 05International audienceSustainable dairy farms need to make better use of feed resources, reduce the use of inputs and their environmental impacts, particularly in terms of nitrogen (N) losses. Dairy cattle are largely fed on grazed grass in Western Europe but, at certain times of the year, conserved forages and concentrates may be added to the animal diet. Few studies have investigated the consequences of this combination on the animal’s N use and manure composition. Moreover, inthese situations, animals divide their time between grazing, where urine and solid excreta fall directly onto the soil, and the building, where manure need to be managed and stored, leading to contrasted impacts on the environment. Our project focuses on strategies combining grazed and conserved forages in dairy systems and their consequences on N flows and environmental impacts. Several experiments were conducted to compare animal performance, N use efficiency and gaseous emissions (ammonia and greenhouse gases) of full-housing (FH) vs half-housing-half-grazing (HH-HG) vs full grazing (FG) management systems in spring and autumn 2022. In the FH treatment, cows were housed in mechanically ventilated rooms where they were fed a basic diet of maize silage and concentrates ad libitum. Manure was scraped, collected and transferred to controlled pens. Gaseous emissions were measured in the house and during manure storage by spot air samples, with several methods. In the FG treatment, cows grazed a temporary pasture equipped with an eddy covariance flux tower and several trace gas infrared analysers (NH3, N2O, CH4, CO2, H2O), and ALPHA passive diffusion samplers for NH3 coupled with short-range atmospheric dispersion modelling for the determination of field-scale gaseous emissions. Cows on the HH-HG treatment were housed in a mechanically ventilated room at night (receiving 8 kg DM of the basic diet) and grazed on a temporary pasture during the day (8 hours). The results will contribute to the acquisition of new knowledge on these mixed systems especially in terms of gaseous losses over the whole continuum of cattle feeding and manure management

Gaseous emissions (building, storage, pasture) of dairy systems combining or not grazing and housing

Session 05International audienceSustainable dairy farms need to make better use of feed resources, reduce the use of inputs and their environmental impacts, particularly in terms of nitrogen (N) losses. Dairy cattle are largely fed on grazed grass in Western Europe but, at certain times of the year, conserved forages and concentrates may be added to the animal diet. Few studies have investigated the consequences of this combination on the animal’s N use and manure composition. Moreover, inthese situations, animals divide their time between grazing, where urine and solid excreta fall directly onto the soil, and the building, where manure need to be managed and stored, leading to contrasted impacts on the environment. Our project focuses on strategies combining grazed and conserved forages in dairy systems and their consequences on N flows and environmental impacts. Several experiments were conducted to compare animal performance, N use efficiency and gaseous emissions (ammonia and greenhouse gases) of full-housing (FH) vs half-housing-half-grazing (HH-HG) vs full grazing (FG) management systems in spring and autumn 2022. In the FH treatment, cows were housed in mechanically ventilated rooms where they were fed a basic diet of maize silage and concentrates ad libitum. Manure was scraped, collected and transferred to controlled pens. Gaseous emissions were measured in the house and during manure storage by spot air samples, with several methods. In the FG treatment, cows grazed a temporary pasture equipped with an eddy covariance flux tower and several trace gas infrared analysers (NH3, N2O, CH4, CO2, H2O), and ALPHA passive diffusion samplers for NH3 coupled with short-range atmospheric dispersion modelling for the determination of field-scale gaseous emissions. Cows on the HH-HG treatment were housed in a mechanically ventilated room at night (receiving 8 kg DM of the basic diet) and grazed on a temporary pasture during the day (8 hours). The results will contribute to the acquisition of new knowledge on these mixed systems especially in terms of gaseous losses over the whole continuum of cattle feeding and manure management

Electron Capture in Collisions of Slow Highly Charged Ions with an Atom and a Molecule: Processes and Fragmentation Dynamics

Abstract: Processes involved in slow collisions between highly charged ions (HCI) and neutral targets are presented. First, the mechanisms responsible for double electron capture are discussed. We show that, while the electron-nucleus interaction is expected to be dominant at projectile velocities of about 0.5 a.u., the electron-electron interaction plays a decisive role during the collision and gains importance when the projectile velocity decreases. This interaction has also to be invoked in the capture of core electrons by HCI. Finally, the molecular fragmentation of H2 following the impact of HCI is studied

Precision measurements in the beta decay of 6He

International audienceWe report here about the ongoing data analysis of an experiment performed at GANIL with a 25 keV 6He+ beam to determine the Fierz interference term from the β particles energy spectrum