Indirect measurements of neutron-induced reaction cross sections at storage rings

Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars. However, their measurement is very difficult due to the radioactivity of the targets involved. We propose to circumvent this problem by using for the first time the surrogate reaction method in inverse kinematics at heavy-ion storage rings. In this contribution, we describe the developments we have done to perform surrogate-reaction studies at the storage rings of GSI/FAIR. In particular, we present the first results of the proof of principle experiment, which we conducted recently at the Experimental Storage Ring (ESR)

AIFIRA: a light ion beam facility for ion beam analysis and irradiation

AIFIRA is a small-scale ion beam facility equipped with a single-stage electrostatic accelerator delivering bright beams of light ions (protons, deuterons and helium ions) in the MeV energy range. The facility provides ion beam irradiation, analysis, and imaging techniques to academic research groups and companies. These techniques cover a wide range of applications including materials research, life sciences, environment, geology and geochemistry, archeometry, and applied physics. About 200 days of beam time are allocated each year to internal and external users either coming from local, national, or international teams. AIFIRA is certified as a research platform by its two parent institutions: CNRS/IN2P3 and the university of Bordeaux. Therefore, beamtime allocation is opened to external teams that are accompanied by local experts to prepare, perform and analyze their experiments. This paper describes the facility and the developments performed in the last years. We highlight two original features of the facility: charge collection studies using a microbeam and the production of secondary neutron fields

Status on the DESIR High Resolution Separator Commissioning

Many nuclear reactions used to create radioactive isotopes for nuclear research produce, in addition to the isotope of interest, many contaminants, which are often produced in much larger amounts than the isotope of interest. Many installations using the ISOL approach are therefore equipped with high-resolution mass separators to remove at least isotopes with a different mass number. In the present paper, we present the results of the commissioning of the DESIR HRS presently under development at LP2I Bordeaux (formerly CENBG). Optical aberrations are corrected up to 3rd order and a mass resolution of M/$\Delta$M of 25000 is reached with a transmission of about 70% for a 133Cs+ beam at 25 keV

Status on the DESIR High Resolution Separator Commissioning

Many nuclear reactions used to create radioactive isotopes for nuclear research produce, in addition to the isotope of interest, many contaminants, which are often produced in much larger amounts than the isotope of interest. Many installations using the ISOL approach are therefore equipped with high-resolution mass separators to remove at least isotopes with a different mass number. In the present paper, we present the results of the commissioning of the DESIR HRS presently under development at LP2I Bordeaux (formerly CENBG). Optical aberrations are corrected up to 3rd order and a mass resolution of M/$\Delta$M of 25000 is reached with a transmission of about 70% for a 133Cs+ beam at 25 keV

Status on the DESIR High Resolution Separator Commissioning

Many nuclear reactions used to create radioactive isotopes for nuclear research produce, in addition to the isotope of interest, many contaminants, which are often produced in much larger amounts than the isotope of interest. Many installations using the ISOL approach are therefore equipped with high-resolution mass separators to remove at least isotopes with a different mass number. In the present paper, we present the results of the commissioning of the DESIR HRS presently under development at LP2I Bordeaux (formerly CENBG). Optical aberrations are corrected up to 3rd order and a mass resolution of M/$\Delta$M of 25000 is reached with a transmission of about 70% for a 133Cs+ beam at 25 keV

Commissioning of the DESIR high-resolution mass separator

International audienceDESIR is, together with S3-LEB, the low-energy part of the SPIRAL2 ISOL facility at GANIL. The High-Resolution mass Separator (HRS) included in DESIR is a 180° symmetric online separator with two 90° magnetic dipole sections arranged with electrostatic quadrupoles, sextupoles and a 48-pole electrostatic multipole on the mid plane. The HRS is now completely mounted at LP2i Bordeaux and under commissioning for the next years before its transfer to the entrance of the DESIR facility. Optical aberrations, mainly introduced by the dipoles, must be corrected up to the highest possible order to guarantee an optimal resolution of the separator. They are measured with a pepperpot-type emittance-meter, analyzed then corrected with the multipole. Up to now, 2nd order (hexapolar) and part of 3rd order (octupolar) aberrations are under control and an optimal FWHM separation has been achieved for two identical beams with a relative energy difference of .In this paper, we present the effects of optical aberrations on the beam and its emittance figure, as well as the effect of the associated corrections with the multipole. Finally, we will show the latest resolution measurements and associated methodology

WISArD : Weak Interaction Studies with 32^{32}Ar Decay

International audienceThe WISArD experiment is probing the possible existence of exotic currents in the electroweak sector using nuclear $\beta$ decay, to improve the constraints on beyond Standard Model physics. The setup of the experiment underwent a full upgrade between 2018 and 2021 in preparation of a second run of data taking at ISOLDE, CERN, scheduled for October 2021. The detector stage was completely renewed to improve statistics and minimize the main systematic effects identified in a proof-of-principle run in 2018. With this upgrade, the objective is to reach the per-mil level of uncertainty on the angular correlation coefficent $a$ and on the Fierz interference term $b$, in a pure Fermi transition. In this case, both parameters are directly sensitive to the possible contribution of exotic scalar currents

PIPERADE: A double Penning trap for mass separation and mass spectrometry at DESIR/SPIRAL2

A double Penning trap is being commissioned at CENBG Bordeaux for the future DESIR/SPIRAL2 facility of GANIL. The setup is designed to perform both high-resolution mass separation of the ion beam for trap-assisted spectroscopy, and high-accuracy mass spectrometry of short-lived nuclides. In this paper, the technical details of the new device are described. First offline tests with the purification trap are also presented, showing a mass resolving power of about 105

Simultaneous measurements of the β\beta -neutrino angular correlation in 32^{32}Ar pure Fermi and pure Gamow-Teller transitions using β\beta -proton coincidences

We report first time measurements of the beta-neutrino angular correlation based on the kinetic energy shift of protons emitted in parallel or anti-parallel directions with respect to the positron in the beta decay of $^{32}$Ar. This proof of principle experiment provided simultaneous measurements for the superallowed 0$^+$~$\rightarrow$~0$^+$ transition followed by a 3356~keV proton emission and for a Gamow-Teller transition followed by a 2123~keV proton emission. The results, respectively ${\tilde a_{\beta\nu}}=1.01(3)_{(stat)}(2)_{(syst)}$ and ${\tilde a_{\beta\nu}}=-0.22(9)_{(stat)}(2)_{(syst)}$, are found in agreement with the Standard Model. A careful analysis of the data shows that future measurements can reach a precision level of 10$^{-3}$ for both pure Fermi and pure Gamow-Teller decay channels, providing new constraints on both scalar and tensor weak interactions