Transport and cooling of singly-charged noble gas ion beams

The transport and cooling of noble gas singly-charged ion beams by means of a Radio Frequency Quadrupole Cooler Buncher (RFQCB) have been studied at the LIMBE low energy beam line of the GANIL facility. Ions as light as $^{4}He^+$ have been cooled and stored before their extraction in bunches using $H_2$ as buffer gas. Bunches characteristics have been studied as a function of the parameters of the device. Sizeable transmissions of up to 10 $$ have been obtained. A detailed study of the lifetime of ions inside the buncher has been performed giving an estimate of the charge exchange cross-section. Results of a microscopic Monte-Carlo transport code show reasonable agreement with experimental data.Comment: 13 figure

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

Electron shakeoff following the β+ decay of trapped 35Ar+ ions

The electron shakeoff of 35Cl atoms resulting from the β+ decay of 35Ar+ ions has been investigated using a Paul trap coupled to a recoil-ion spectrometer. The charge-state distribution of the recoiling daughter nuclei is compared to theoretical calculations accounting for shakeoff and Auger processes. The calculations are in excellent agreement with the experimental results and enable one to identify the ionization reaction routes leading to the formation of all charge states.D.R. acknowledges support from the Spanish ministry of Economy and Competitiveness under the project FPA2010-14803 and the action AIC10-D000562

A GEANT4 Monte-Carlo Simulation Code for precision beta spectroscopy

The measurement of the beta asymmetry parameter in nuclear beta decay is a potentially very sensitive tool to search for non V-A components in the charge-changing weak interaction. To reach the required precision (percent level) all effects that modify the emission pattern of the beta radiation, i.e. the geometry of the setup, the effect of the magnetic field on the trajectories of beta particles as well as (back)scattering in the source, on the sample holder and on the detector, have to be correctly taken into account in the analysis of the data. A thorough study of these effects and a new method based on detailed GEANT4 Monte-Carlo simulations that was developed for this purpose is presented here. The code was developed for beta asymmetry measurements by means of the Low Temperature Nuclear Orientation (LTNO) method, but can in principle be generalized to other experimental setups using other polarization techniques

Weak Interaction Studies ith \u3csup\u3e6\u3c/sup\u3eHe

The 6He nucleus is an ideal candidate to study the weak interaction. To this end we have built a high-intensity source of 6He delivering ∼1010 atoms/s to experiments. Taking full advantage of that available intensity we have performed a high-precision measurement of the 6He half-life that directly probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a measurement of the beta-neutrino angular correlation in 6He beta decay that will allow to search for new physics beyond the Standard Model in the form of tensor currents. © 2013 AIP Publishing LLC

Is there a dark decay of neutrons in 6^6He ?

Motivated by the four standard deviations discrepancy between the mean values for the neutron lifetime obtained from beam and bottle experiments, we have searched for a hypothetical neutron dark decay in $^6$He nuclei through the channel $^6{\rm He} \rightarrow ^4{\rm He}+n+\chi$. The experiment used a 25~keV high intensity $^6$He$^+$ beam with a high efficiency neutron detector. The search for a signal correlated with the $^6$He activity in the neutron detection rate resulted in a branching ratio ${\rm Br}_\chi \leq 4.0\times10^{-10}$ with a 95\% C.L. over the mass window $937.993 < m_\chi < m_n-0.975$ MeV. This result is five orders of magnitude smaller than required to solve the neutron lifetime discrepancy

In gas laser ionization and spectroscopy experiments at the Superconducting Separator Spectrometer (S3): Conceptual studies and preliminary design

International audienceThe results of preparatory experiments and the preliminary designs of a new in-gas laser ionization and spectroscopy setup, to be coupled to the Super Separator Spectrometer S3 of SPIRAL2-GANIL, are reported. Special attention is given to the development and tests to carry out a full implementation of the in-gas jet laser spectroscopy technique. Application of this novel technique to radioactive species will allow highsensitivity and enhanced-resolution laser spectroscopy studies of ground- and excited-state properties of exotic nuclei

Geometry optimisation of a transparent axisymmetric ion trap for the MORA project

International audienceIn the frame of the project MORA (Matter’s Origin from the Radio Activity of trapped and oriented ions), a transparent axially symmetric radio-frequency ion trap (moratrap) was designed in order to measure the triple correlation parameter D in nuclear $\beta$-decay of laser-polarised ions. The trap design was inspired from the lpctrap geometry, operated at GANIL from 2005 to 2013. In a real (non-ideal) Paul trap, the quadrupole electric potential is not perfect leading to instabilities in ion motion and therefore affecting the overall trapping efficiency. This paper presents a numerical method aiming to optimise the geometry of a trap. It is applied to moratrap in order to improve the trapping efficiency and to enlarge the axial transparent solid angle compared to lpctrap. In the whole optimisation process, numerical computation of electric potential and field was carried out using an electrostatic solver based on boundary element method (BEM). The optimisation consisted in minimising an objective function (fitness function) depending on higher order multipoles of the potential. Finally, systematic changes of trap dimensions and electrode displacements were applied to investigate geometrical effects on the potential quality