GABRIELA : a new detector array for gamma-ray and conversion electron spectroscopy of transfermium elements

With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear Reactions, JINR, Dubna. GABRIELA (Gamma Alpha Beta Recoil Investigations with the Electromagnetic Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of alpha- and beta-particles, fission fragments, gamma- and X-rays, and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.Comment: 24 pages, Submitted to NIM

Separator for Heavy ELement Spectroscopy – velocity filter SHELS

International audienceThe SHELS velocity filter originated upon reconstruction of the VASSILISSA electrostatic separator used for investigations of heavy nuclei produced in complete fusion reactions. The goals of this modernization were to increase the transmission of products of asymmetric reactions and to extend the region of reactions to be investigated up to symmetric combinations. The first tests of the set-up were performed with the beams of accelerated 22 Ne, 40 Ar, 48 Ca, and 50 Ti ions

On-line separator for γ\gamma-spectroscopic studies at FLNR JINR

International audienceA JINR — IN2P3 collaboration project named “GABRIELA” aimed at the nuclear spectroscopy of transfermium elements using the recoil separator VASSILISSA was launched in 2004 at JINR in Dubna. In the close future the FLNR cyclotron U400M will go through a major upgrade with the goal to deliver heavy ion beams at the energy close to the Coulomb barrier in a new experimental area. Here we report about R&D of the new separator for spectroscopic studies which we plan to install at the beam of the modernized accelerator and which will allow to realize new possibilities of the GABRIELA project

Digital Signal Processing for the GABRIELA Detector Assembly

International audienceThis paper briefly describes the main ways of digital signal processing. The goal of the digital algorithms is to reduce the dead time of the spectrometry path to tens of nanoseconds without loss of energy and time resolutions. The new kσ-trigger with extrapolation technique is proposed in the paper. The method allows to find overlapped signals almost irrespective of their closeness in time

The emission of prompt neutrons from the spontaneous fission of No-252 and Fm-244

The neutron detector with (3)He -filled counters placed in the focal plane of the VASSILISSA separator is used for measuring the average number and determining the multiplicity distribution of prompt neutrons from the spontaneous fission of heavy short-lived isotopes. The test reaction is used for tuning the separator settings and calibrating the detector system with the spontaneous fission of the (252)No . The average neutron number per (252)No spontaneous fission event is as large as . The short-lived heavy isotope (244)Fm , produced in the complete fusion reaction (40)Ar + (206)Pb , is investigated. The average number of neutrons per spontaneous fission of (244)Fm from the experimental data ( is determined for the first time

Spontaneous-fission decay properties and production cross-sections for the neutron-deficient nobelium isotopes formed in the \chem{^{44,48}Ca +\,^{204,206,208}Pb} reactions

Heavy-ion fusion reactions $^{48}$Ca + $^{204}$Pb and $^{44}$Ca + $^{208}$Pb leading to the same compound nucleus $^{252}$No$^{*}$ were run in attempts to produce new neutron-deficient spontaneous-fission isotopes of $^{249,250}$No using the electrostatic separator VASSILISSA. Production cross-sections for the spontaneous-fission activities with the half-lives 5.6 and 54 $\mu$s observed in these reactions are compared with the measured ones for the well-known isotopes of $^{251 - 255}$No formed in the heavy-ion fusion reactions $^{48}$Ca + $^{206}$Pb and $^{48}$Ca + $^{208}$Pb. The obtained excitation functions for the reaction products formed after the evaporation of 1–4 neutrons from the corresponding compound No nuclei have been compared with similar data obtained earlier and results of statistical model calculations

Prototype of the Digital Electronics Chain for the GABRIELA Detector Assembly and First Tests

International audienceThis paper describes a digital electronics chain prototype for the GABRIELA detector assembly. The goal of the digital algorithm is to reduce the dead time of the electronics to tens of nanoseconds without loss of energy and time resolution. The structure and temporal diagrams of the algorithm are given in the text. The paper also shows the energy resolution of the algorithm in comparison with the existing analog system and the results of the first in beam run

Detailed Study of the Radioactive Decay Properties of No, Rf, and Db Isotopes

International audienceProperties of the radioactive decay of No, Rf isotopes are studied in the reaction $^{50}$Ti + $^{209}$Bi → $^{259}$Db* . The cross sections of Db and Rf isotopes production in channels xn and pxn, respectively, are measured. High intensity beams of accelerated heavy ions $^{22}$Ne, $^{48}$Ca, $^{50}$Ti, and $^{54}$Cr of the U400 cyclotron and SHELS kinematic separator are used in the experiments

GABRIELA setup for nuclear spectroscopy of the transfermium element isotopes at the VASSILISSA separator

The JINR (Dubna)-IN2P3 (France) Collaboration project aimed at the alpha, beta, gamma spectroscopy of the transfermium element isotopes using heavy-ion beams of the U-400 cyclotron and the modernized recoil separator VASSILISSA was launched at Dubna. During the first full-scale experiment in September-October 2004, nobelium and lawrencium isotopes produced in the Ca-48 + Pb-207,Pb-208 -> No-255,No-256* and Ca-48 + Bi-209 -> Lr-257* reactions were studie