Deep sub-threshold $K^\ast (892)^{\circ}$ production in collisions of Ar + KCl at 1.76 A GeV

2013

Deep sub-threshold K*(892)0 production in collisions of Ar + KCl at 1.76A GeV

2013

Results on the deep sub-threshold production of the short-lived hadronic resonance K*(892)0 are reported for collisions of Ar + KCl at 1.76A GeV beam energy, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. The K*(892)0 production probability per central collision of \( P_{K^{*0}}=(4.4\pm 1.1 \pm 0.5)\times 10^{-4}\) and the K*(892)0/K0 ratio of \( P_{K^{*0}}/P_{K^0}=(1.9\pm 0.5\pm 0.3)\times 10^{-2}\) are determined at the lowest energy so far (i.e. deep below the threshold for the corresponding production in nucleon-nucleon collisions, \( \sqrt{s_{NN}}-\sqrt{s_{thr}}=-340\) MeV). The K*0/K0 ratio is compared with results of other experiments and with the pre…

Simultaneous Measurement ofβ−Decay to Bound and Continuum Electron States

2005

We report the first measurement of a ratio {lambda}{sub {beta}{sub b}}/{lambda}{sub {beta}{sub c}} of bound-state ({lambda}{sub {beta}{sub b}}) and continuum-state ({lambda}{sub {beta}{sub c}}) {beta}{sup -}-decay rates for the case of bare {sup 207}Tl{sup 81+} ions. These ions were produced at the GSI fragment separator FRS by projectile fragmentation of a {sup 208}Pb beam. After in-flight separation with the B{rho}-{delta}E-B{rho} method, they were injected into the experimental storage-ring ESR at an energy of 400.5A MeV, stored, and electron cooled. The number of both the {sup 207}Tl{sup 81+} ions and their bound-state {beta}{sup -}-decay daughters, hydrogenlike {sup 207}Pb{sup 81+} ion…

The Miniball spectrometer

2013

The Miniball germanium detector array has been operational at the REX (Radioactive ion beam EXperiment) post accelerator at the Isotope Separator On-Line facility ISOLDE at CERN since 2001. During the last decade, a series of successful Coulomb excitation and transfer reaction studies have been performed with this array, utilizing the unique and high-quality radioactive ion beams which are available at ISOLDE. In this article, an overview is given of the technical details of the full Miniball setup, including a description of the γ-ray and particle detectors, beam monitoring devices and methods to deal with beam contamination. The specific timing properties of the REX-ISOLDE facility are hi…

New results with stored exotic nuclei at relativistic energies

2004

Recently, much progress has been made with stored exotic nuclei at relativistic velocities ( v c = 0.7 ) . Fragments of 208Pb and 209Bi projectiles and fission products from 238U ions were produced, separated in flight with the fragment separator FRS, and injected into the storage-cooler ring ESR for precision measurements. 114 new masses of neutron-deficient isotopes in the lead region have been measured with time-resolved Schottky Mass Spectrometry (SMS). A new isospin dependence of the pairing energy was observed due to the improved mass accuracy of typically 1.5×10-7 (30 keV). New masses of short-lived neutron-rich fission fragments have been obtained with Isochronous Mass Spectrometry …

β -decay half-lives and β -delayed neutron emission probabilities for several isotopes of Au, Hg, Tl, Pb, and Bi, beyond N=126

2017

Background: Previous measurements of Beta-delayed neutron emitters comprise around 230 nuclei, spanning from the 8He up to 150La. Apart from 210Tl, with a minuscule branching ratio of 0.07%, no other neutron emitter is measured yet beyond A = 150. Therefore new data are needed, particularly in the heavy mass region around N=126, in order to guide theoretical models and to understand the formation of the third r-process peak at A 195. Purpose: To measure both, Beta-decay half-lives and neutron branching ratios of several neutron-rich Au, Hg, Tl, Pb and Bi isotopes beyond N = 126. Method: Ions of interest are produced by fragmentation of a 238U beam, selected and identifed via the GSI-FRS fra…

Study of Basic Nuclear Properties of Highly-Charged, Unstable Nuclei at the SIS-FRS-ESR Complex

2004

Recent progress in experiments with exotic nuclear beams at the SIS-FRS-ESR facility is summarized. New results on gross properties of exotic nuclei like binding energy, half-lives, and decay modes are presented. A brief outlook to future experiments is given.

Superallowed Gamow-Teller decay of the doubly magic nucleus $^{100}$Sn

2012

Expérience au GSI; The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During b1-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy fo…

β-delayed neutron emission measurements around the third r-process abundance peak

2013

This contribution summarizes an experiment performed at GSI (Germany) in the neutron-rich region beyond N=126. The aim of this measurement is to provide the nuclear physics input of relevance for r-process model calculations, aiming at a better understanding of the third r-process abundance peak. Many exotic nuclei were measured around 211Hg and 215Tl. Final ion identification diagrams are given in this contribution. For most of them, we expect to derive halflives and and β-delayed neutron emission probabilities. The detectors used in this experiment were the Silicon IMplantation and Beta Absorber (SIMBA) detector, based on an array of highly segmented silicon detectors, and the BEta deLayE…

β-decay and β-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis

2014

New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and β-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them (208-211Hg, 211-215Tl, 214-218Pb) were implanted with enough statistics to determine their half-lives. About half of them a…

The upgraded HADES trigger and data acquisition system

2011

The HADES experiment is a High Acceptance Di-Electron Spectrometer located at GSI in Darmstadt, Germany. Recently, its trigger and data acquisition system was upgraded. The main goal was to substantially increase the event rate capability by a factor of up to 20 to reach 100 kHz in light and 20 kHz in heavy ion reaction systems. The total data rate written to storage is about 400 MByte/s in peak.In this context, the complete read-out system was exchanged to FPGA-based platforms using optical communication. For data transport a general-purpose real-time network protocol was developed to meet the strong requirements of the system. In particular, trigger information has to reach all front-end …

pp and ππ intensity interferometry in collisions of Ar+KCl at 1.76A GeV

2011

Results on pp, π+π+, and π-π- intensity interferometry are reported for collisions of Ar+KCl at 1.76$A$~GeV beam energy, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. The experimental correlation functions as a function of the relative momentum are compared to model calculations allowing the determination of the space-time extent of the corresponding emission sources. The π π source radii are found significantly larger than the pp emission radius. The present radii do well complement the source-size excitation functions of the collision system of size $A+A \simeq 40+40$. The pp source radius at fixed beam energy is found to increase linearly with the cube r…

First Measurement of Severalβ-Delayed Neutron Emitting Isotopes BeyondN=126

2016

The β-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N≳126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.

A compact system for high precision time measurements ( < 14 ps RMS) and integrated data acquisition for a large number of channels

2011

A high precision ( < 14 ps RMS time resolution) and high channel density ( ~ 256 channels) Time to Digital Converter (TDC) module (realized in FPGAs) with integrated DAQ is presented. The data is transported over up to 8 Gigabit-Ethernet or optical links with up to 3 Gb/s. Slow-Control information is transported over the same links. It can be attached directly to the detector, which allows the elimination of long cables and crate systems. The full 256 channel TDCs are expected to use approximately 30 W electrical power. The module size is 20 cm by 23 cm. Power is provided by a galvanically isolated 48 V low noise power supply. AddOn-boards adapt to the special needs of the detector to be re…

NUCLEAR STRUCTURE ADDRESSED AT GSI/RISING

2009

Nuclear structure spectroscopy studies at GSI recently gained increased momentum within a broad international community with the installation of the Rare Isotopes Spectroscopic INvestigation at GSI (RISING) project. A wide range of physical phenomena has been addressed by high-resolution in-beam γ-ray spectroscopy experiments with radioactive beams. Relativistic radioactive beams are implanted and their subsequent γ and β decay is investigated. Within this "stopped beam campaign" germanium detectors were arranged in a close geometry around the passive stopper or an array of DSSSD detectors. The exceptionally high γ-ray efficiency of that configuration made it possible to identify decays of…

Approaching the precursor nuclei of the third r-process peak with RIBs

2013

The rapid neutron nucleosynthesis process involves an enormous amount of very exotic neutron-rich nuclei, which represent a theoretical and experimental challenge. Two of the main decay properties that affect the final abundance distribution the most are half-lives and neutron branching ratios. Using fragmentation of a primary $^{238}$U beam at GSI we were able to measure such properties for several neutron-rich nuclei from $^{208}$Hg to $^{218}$Pb. This contribution provides a short update on the status of the data analysis of this experiment, together with a compilation of the latest results published in this mass region, both experimental and theoretical. The impact of the uncertainties …