Search results for "fission"
showing 10 items of 421 documents
Total photofission cross section for 238U as a substitute for the photon absorption cross section in the energy range of the first baryon resonances
1992
Abstract The total photofission cross section σγ, F for 238U has been measured as a substitute for the total photon absorption cross section σtot in the energy range of the first baryon resonances (50⩽Eγ⩽800 MeV). The experiments were performed at the tagging facility of the new 855 MeV Mainz Microton MAMI B using monochromatic photons and a sophisticated 4π-arrangement of position sensitive fragment detectors. The measured cross section agrees in the Δ-resonance region with previous results and the so-called universal curve αtot/A. In the energy region of the D13-resonance near 710 MeV resonancelike structure could be observed as is seen for the free proton.
Production of exotic hypernuclei from excited nuclear systems
2012
We show that within a hybrid two-stage approach one can explain novel experimental data on the production of hypernuclei emitted from projectile residues in relativistic ion collisions. This reaction proceeds via formation of intermediate moderately excited hypernuclear systems, which decay into conventional nuclei and hyperfragments afterward. With a similar reaction mechanism one can also obtain weakly bound exotic hypernuclei (such as $\ensuremath{\Lambda}n$ and H-dibaryons), which may not be easily accessible in other processes.
The decay of 31 sec98Zr, 2.9 sec98Nb and 51 min98Nb
1976
TheΒ- andγ-radiations of98Zr and98m, g Nb have been investigated employing scintillation and semiconductor spectrometers and coincidence techniques. Sources of98Nb were produced by the98Mo(n, p)98Nb reaction, sources of98Zr by fission of235U with thermal neutrons applying chemical separations. For98Zr, a half-life of 30.7±0.4 sec and aQ β-value of 2.3±0.2 MeV were obtained, for the98Nb isomers, half-lives of 2.86±0.06 sec and 51.3±0.4 min, andQ β-values of 4.8±0.2 MeV and 4.5±0.2 MeV, respectively. Noγ-rays were observed in the decay of98Zr. The decay of 2.9 sec98Nb was found to involve 11γ-ray transitions. In the decay of 51 min98Nb, 54γ-transitions were detected. Spin and parity of 1+ and…
Der Zerfall des93Sr
1972
The nucleide93Sr was isolated by chemical separation methods after thermal neutron induced fission of235U, and its decay properties were investigated employing scintillation and semiconductor spectrometers and coincidence techniques. A half-life of 7.43±0.03 min and aQβ-value of 4.3±0.2 MeV were found. Out of 74 gamma-rays, 55 transitions, representing 97% of the observed gamma-ray intensity, could be placed in a decay scheme comprising 22 excited states of93Y.
Decay of the 4.2-min152Pm into levels of152Sm
1975
After bombardments of enriched152Sm with 14-MeV neutrons, three isomers of125Pm reaction, have been observed with half-lives of 4.2±0.2 min, 7.5±0.2 min and 15.0±1.0 min. Sources of pure 4.2-min152Pm were obtained by separating the promethium from its parent 11-min152Nd produced by thermal-neutron induced fission of235U. The beta and gamma radiations of the 4.2-min152Pm have been investigated using semiconductor and scintillation spectrometers. Most of theγ-ray transitions could be placed in a level scheme for 152Sm. Especially interesting is a level at 1083 keV for which the assignmentI π=0+ is proposed. In a 4πβγ experiment, the ground state feeding of152Sm in theβ −-decay of the 4.2-min1…
A dedicated decay-spectroscopy station for the collinear resonance ionization experiment at ISOLDE
2013
A newdecay-spectroscopystation(DSS)has been developed to be coupled to the collinear resonance ionization spectroscopy (CRIS) beam line at CERN-ISOLDE. The system uses a rotatable wheel with ten 20 mg=cm2 carbon foils as beam implantation sites for the efficient measurement of charged decay products. Silicon detectors are placed on either side of the carbon foil in an optimal geometry to cover a large solid angle for detecting these charged particles. In addition to the silicon detectors at the on-beam axis position, a second pair of off-beam axis detectors are placed at the wheel position 108 deg. away, allowing longer-lived species to be studied. Up to three high purity germanium detector…
Energy distribution of ternaryαparticles in spontaneous fission ofCf252
2008
The energy distribution of the ternary $\ensuremath{\alpha}$ particles in spontaneous fission of $^{252}\mathrm{Cf}$ was measured. For the first time an energy threshold as low as 1 MeV was reached. The experiment used an array of unshielded silicon detectors measuring energy and time-of-flight (TOF) of ternary particles in coincidence with fission fragments. The TOF resolution of the system was sufficient for clear separation of $^{6}\mathrm{He}$ and tritons from $^{4}\mathrm{He}$. The statistics were adequate to extract the $^{6}\mathrm{He}$/$^{4}\mathrm{He}$ yield ratio. For both $^{4}\mathrm{He}$ and $^{6}\mathrm{He}$, an excess in the yield (as compared to a Gaussian shape) was observe…
Time response of TOF spectrometer to light and heavy particles
2002
Comparing time of flight (TOF) values for α particles and fission fragments measured at different distances between the start- and stop detector we have obtained 60 ps as the upper limit for the TOF error resulting from the assumption of equal and linear time calibrations for both types of particles. While the 60 ps limit relates only to the specific spectrometer, the problem and the suggested verification technique are of general interest.
Study of medium-spin states of neutron-rich 87, 89, 91Rb isotopes
2019
International audience; Excited states of the rubidium isotopes$_{37}^{87, 89, 91}$Rb have been studied at the INFN Legnaro National Laboratory. Measurements of the $\gamma$ -ray decay of fragments produced in binary grazing reactions resulting from the interaction of a beam of 530 MeV$^{96}$Zr ions with a$^{124}$Sn target have been complemented by studies of the $\gamma$ -ray decay of fission fragments produced in the interaction of a beam of 230 MeV$^{36}$S ions with a thick$^{176}$Yb target. The structure of the yrast states of$_{37}^{87, 89, 91}$Rb has been discussed within the context of spherical shell-model and cranked Nilsson-Strutinsky calculations.
Low-spin structure of85Se and theβnbranching of85As
2012
Fission fragments from neutron-induced fission of ${}^{235}$U produced at the high-flux reactor of the Institut Laue-Langevin, Grenoble, were separated with the Lohengrin separator to provide a beam of neutron-rich ${}^{85}\phantom{\rule{-0.16em}{0ex}}$As nuclei. The ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{85}\phantom{\rule{-0.16em}{0ex}}$As to ${}^{85}$Se was studied using $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ and $\ensuremath{\beta}$-$\ensuremath{\gamma}$ coincidence techniques. ${}^{85}$Se was also studied using the prompt-$\ensuremath{\gamma}$ coincidence data from spontaneous fission of ${}^{248}$Cm and ${}^{252}$Cf measured with the Eurogam2 and Gammasphere Ge arra…