Search results for "fission"
showing 10 items of 421 documents
Non-destructive diagnostics of thin fissile layers
2003
We have developed a non-destructive nuclear technique useful for the diagnostic of thin layers of fissile element. The method is based on the correlation between the fission fragment energy losses and the distortion of the energy spectrum of the alpha-particles emerging from the layer itself. We have also measured the sputtering rate of atoms from a fission layer which can be the cause of an important degradation in a working apparatus.
Wien filter for cooled low-energy radioactive ion beams
2002
A Wien filter for cooled radioactive ion beams has been designed at Ion Guide Isotope Separator On Line technique (IGISOL). The purpose of such device is to eliminate doubly charged ions from the mass separated singly charged ions, based on q=+2→q=+1 charge exchange process in an ion cooler. The performance of the Wien filter has been tested off-line with a discharge ion source as well as on-line with a radioactive beam. The electron capture process of cooled q=+2 ions has been investigated in a radiofrequency quadrupole ion cooler with varying partial pressures of nitrogen. Also, the superasymmetric fission production yields of 68<A<78 nuclei have been deduced.
Beta Decay of 111Tc to 111Ru
1998
The β-decay of the very neutron-rich 111Tc nucleus has been observed. A partial decay scheme of 111Ru is presented, complementing the high-spin levels earlier reported in spontaneous fission work.
Zeptosecond contact times for element Z=120 synthesis
2020
The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of $^{48}$Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Attempts to produce nuclei with Z=120 using the $^{64}$Ni+$^{238}$U, $^{58}$Fe+$^{244}$Pu, $^{54}$Cr+$^{248}$Cm, and $^{50}$Ti+$^{249}$Cf reactions have been made, which all result in larger Coulomb forces than for $^{48}$Ca-induced reactions, but no discovery has been confirmed to date. In this work, mass and angle distributions of fission frag…
Gamma-spectroscopy of the 199At nucleus with the recoil filter detector
1998
The neutron deficient 199At nucleus has been studied in the 175Lu+28Si reaction at Eb= 141 MeV. In order to select events of interest in the presence of the very strong background caused by fission, γ-rays have been detected in coincidence with recoiling evaporation residues. The excited states of 199At observed for the first time may indicate that this nucleus is deformed.
Decay properties of265Sg(Z=106)and266Sg(Z=106)
1998
The presently known most neutron-rich isotopes of element 106 (seaborgium, Sg), {sup 265}Sg and {sup 266}Sg, were produced in the fusion reaction {sup 22}Ne+{sup 248}Cm at beam energies of 121 and 123 MeV. Using the On-Line Gas chemistry Apparatus OLGA, a continuous separation of Sg was achieved within a few seconds. Final products were assayed by {alpha}-particle and spontaneous fission (SF) spectrometry. {sup 265}Sg and {sup 266}Sg were identified by observing time correlated {alpha}-{alpha}-({alpha}) and {alpha}-SF decay chains. A total of 13 correlated decay chains of {sup 265}Sg (with an estimated number of 2.8 random correlations) and 3 decay chains of {sup 266}Sg (0.6 random correlat…
Transfer reactions in inverse kinematics, an experimental approach for fission investigations
2013
Inelastic and multi-nucleon transfer reactions between a $^{238}$U beam, accelerated at 6.14 MeV/u, and a $^{12}$C target were used for the production of neutron-rich, fissioning systems from U to Cm. A Si telescope, devoted to the detection of the target-like nuclei, provided a characterization of the fissioning systems in atomic and mass numbers, as well as in excitation energy. Cross-sections, angular and excitation-energy distributions were measured for the inelastic and transfer channels. Possible excitations of the target-like nuclei were experimentally investigated for the first time, by means of g -ray measurements. The decays from the first excited states of $^{12}$C, $^{11}$B and …
Observation of mass-asymmetric fission of mercury nuclei in heavy ion fusion
2015
Background: Mass-asymmetric fission has been observed in low energy fission of $^{180}\mathrm{Hg}$. Calculations predicted the persistence of asymmetric fission in this region even at excitation energies of 30--40 MeV.Purpose: To investigate fission mass distributions by populating different isotopes of Hg using heavy ion fusion reactions.Methods: Fission fragment mass-angle distributions have been measured for two reactions, $^{40}\mathrm{Ca}+^{142}\mathrm{Nd}$ and $^{13}\mathrm{C}+^{182}\mathrm{W}$, populating $^{182}\mathrm{Hg}$ and $^{195}\mathrm{Hg}$, respectively, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Measurements were ma…
Nuclear spin determination of100mY by collinear laser spectroscopy of optically pumped ions
2010
The nuclear spin of the τ1/2 = 0.94 s isomer in 100Y has been determined by collinear laser spectroscopy of optically pumped yttrium fission fragments at the IGISOL facility, JYFL. The isotopes 96, 98, 99, 100Y were produced by the proton-induced fission of natural uranium, and studied on the 4d5s 3D2 (1045 cm−1) → 4d5p 3P1 (32 124 cm−1) transition at 321.67 nm. Enhancement of the population of the metastable 3D2 level was achieved by optically pumping the ground state population via the 5s2 1S0 → 4d5p 1P1 transition at 363.31 nm while the ions were stored in a linear Paul trap. These data, when combined with previous spectroscopic results, give sufficient information for the nuclear spin o…
Signatures of oblate deformation in the ^{111}Tc nucleus
2011
Monoisotopic samples of exotic, neutron-rich ${}^{111}$Mo nuclei, produced in the deuteron-induced fission of ${}^{238}$U and separated using the IGISOL3 isotope separator, coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-coincidence spectroscopy of ${}^{111}$Tc. New excited levels in ${}^{111}$Tc populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{111}$Mo provide the first indication for an oblate deformation in the mass $A\ensuremath{\approx}110$ region. The wide spin range of levels populated in ${}^{111}$Tc following the decay of ${}^{111}$Mo indicates the existence of two $\ensuremath{\beta}$-decaying levels in ${…