X-ray fluorescence from the element with atomic number Z = 120

Accepted for publication in Physical Review LettersAn atomic clock based on X-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238U + 64Ni at 6.6 MeV/A. Inner shell vacancies are created during the collisions in the electronic structure of the possibly formed Z=120 compound nuclei. The filling of these vacancies accompanied by X-ray emission with energies characteristic of Z=120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the X-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K X-rays from the element with Z = 120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time $\tau$_f$ = 2.5×10−18s has been deduced for Z=120 from the measured X-ray multiplicity

Full simulation of the new generation windowless large area silicon-box for SIRIUS-S3

International audienceThe SPIRAL2 installation is being built in order to study rare elements through the production of radioactive isotopes. Its injector, a superconducting linear accelerator (LINAC) is designed to provide very high intensity (up to ~ 1014 particles/s) beams of deuterons and stable ions between carbon and uranium. The “Super Separator Spectrometer” (S3) was designed to separate and mass-analyse recoils from the various induced fusion-evaporation reactions in order to enable nuclear structure studies of proton-rich rare isotopes around 100Sn and in the region of the Super Heavy Elements. A new optimized focal plan detection system called SIRIUS for “Spectroscopy and Identification of Rare Isotopes Using S3” is developed to within the SIRIUS collaboration. The new generation windowless large area silicon-box developed in this framework is discussed in this article. We present the simulations done in order to determine the best geometry and layout for this large area silicon detector assembly

The Ca-48+Ta-181 reaction: Cross section studies and investigation of neutron-deficient 86 <= Z <= 93 isotopes

© 2019 Fusion-evaporation reactions with the doubly magic projectile 48 Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified by establishing correlated α-decay chains with short-lived sub-μs members. Data are given on decay chains stemming from 225,226 Np, 225 U, and 222,223 Pa. New information on the isotopes 225,226 Np and 222 Pa was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production cross-sections indicate that the usual advantages of using 48 Ca as a beam projectile to produce nuclei Z>100 are absent in the production of these slightly lighter nuclei.status: publishe

The ⁴⁸Ca+ ¹⁸¹Ta reaction: Cross section studies and investigation of neutron-deficient 86 ≤ Z ≤ 93 isotopes

Fusion-evaporation reactions with the doubly magic projectile Ca-48 were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and a evaporation channels were identified by establishing correlated alpha-decay chains with short-lived sub-s, members. Data are given on decay chains stemming from Np-225,Np-226 U-225, and Pa-222,Pa-223. New information on the isotopes Np-225,Np-226 and Pa-222 was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production cross-sections indicate that the usual advantages of using Ca-48 as a beam projectile to produce nuclei Z >100 are absent in the production of these slightly lighter nuclei. (C) 2019 Elsevier B.V All rights reserved

Decay Spectroscopy of Heavy Isotopes at SHIP Using the COMPASS Focal Plane Detection Set-up

International audienceThe new COMPASS detection system designed and developed at GSI, Darmstadt was employed in the focal plane of the SHIP velocity filter on-line during a period of commissioning. The isotope 254No was initially measured for control purposes, following which the nuclei, 227,228,230U, 229Np, and 229,230Pu were synthesized. The obtained data from α-decay spectroscopy is evaluated and compared with previous measurements

Fine structure in the alpha decay of U-224

224U nuclei were populated in fusion-evaporation reactions using a 206Pb target and an intense 22Ne beam. Fusion-evaporation residues were separated by the new separator SHELS at the FLNR, Dubna and implanted into a large-area double-sided silicon strip detector. Position- and time-correlated alpha decays were used to identify evaporation residues. A new α-decay line at 8095(11) keV was observed in this work and assigned as the decay from 224U to the first excited 2+ in the daughter nucleus 220Th. Coincident photons were also observed allowing to unambiguously determine the excitation energy of the first excited 2+ state in 220Th to be 386.5(1) keV and not 373.3(1)keV as previously reported. The half-life of 224U was measured to be 396(17)μs.status: publishe

FIRST EXPERIMENTAL TESTS OF SHELS: A NEW HEAVY ION SEPARATOR AT THE JINR

A new Separator for Heavy ELement Spectroscopy (SHELS) has been recently installed at the U-400 accelerator at FLNR, JINR in Dubna, Russia. The details of the upgrade as well as the results from some of the commissioning runs are discussed. In particular, transmission tests with the 208Pb(40Ar, 2–3n)245−6Fm reaction, as well as isomer spectroscopy results for 210Ra produced in 164Dy(50Ti, 3–5n)209−11Ra reaction are presented.status: publishe

SIRIUS is a state-of-the-art detector system for nuclear decay spectroscopy that will be mounted at the focalplane of S3 (Super Separator Spectrometer), which is part of the new SPIRAL2 facility at GANIL, Caen in France. Such a systemrequires high performance as it is dedicated to the study of very exotic nuclei. It is the result of collaboration between GANILCSNSM, IRFU, and IPHC It is composed of a succession of detectors (Trackers, Silicon detector DSSD and Tunnel plus anarray of five clover Germanium detectors). This set-up is mounted in a compact geometry. The energy measurement variesfrom 50 keV to over 500 MeV with high precision (2 x 10-3) at low energies and 1 % for the detection of heavy ions. A majorchallenge has been the development of new electronics with a very large dynamic range maintaining an adequate energyresolution for the measured particles (with energies from a few hundred keV up to 500 MeV).

International audienceSIRIUS is a state-of-the-art detector system for nuclear decay spectroscopy that will be mounted at the focal plane of S$^3$ (Super Separator Spectrometer), which is part of the new SPIRAL2 facility at GANIL, Caen in France. Such a systemrequires high performance as it is dedicated to the study of very exotic nuclei. It is the result of collaboration between GANILCSNSM, IRFU, and IPHC It is composed of a succession of detectors (Trackers, Silicon detector DSSD and Tunnel plus anarray of five clover Germanium detectors). This set-up is mounted in a compact geometry. The energy measurement variesfrom 50 keV to over 500 MeV with high precision (2 x 10$^{-3}$) at low energies and 1 % for the detection of heavy ions. A majorchallenge has been the development of new electronics with a very large dynamic range maintaining an adequate energyresolution for the measured particles (with energies from a few hundred keV up to 500 MeV)