0000000000347114
AUTHOR
V. G. Lyapin
showing 14 related works from this author
Neutron yields from a thick 13C target irradiated by 30 MeV protons
2002
Abstract Total neutron yields resulting from the proton bombardment of a thick 13 C target have been measured for 30 MeV protons. Absolute intensities, angular distributions and energy spectra of neutrons have been obtained by the time-of-flight technique where the detectors provided continuous coverage from 0° to 120°. Resonances have been found, some of which can be attributed to known states in 14 N. A total yield of 0.022(3) n/p was observed with a slight angular anisotropy towards forward angles. The measured yields are compared to the neutron yields produced by using deuterons on thick 12 C and 9 Be targets.
Neutron and fragment yields in proton-induced fission of 238U at intermediate energies
2001
The primary fission fragment mass and kinetic energy distributions, and neutron multiplicities as function of fragment mass have been measured in the proton-induced fission of 238 U at energies Ep ¼ 20, 35, 50 and 60 MeV using time-of-flight technique. Pre-scission and post-scission neutron multiplicities have been extracted from double differential distributions. The fragment mass dependence of the post-scission neutron multiplicities reveals the gross nuclear shell structure effect even at the higher proton energies we measured. The yields ofneutron-rich fission products in the fission of 238 U by 25 MeV protons were measured using an ion guide-based isotope separator technique. The resul…
Neutron yields from thick 12C and 9Be targets irradiated by 50 and 65 MeV deuterons
2001
Abstract Absolute intensities, angular distributions and energy spectra of neutrons emitted from thick 12 C and 9 Be targets irradiated with 50 and 65 MeV deuterons, respectively, have been measured. The neutron spectra were measured by time-of-flight (TOF) technique. The detectors provided continuous coverage from 0° to 60° where a significant angular dependence of emitted neutrons was found. The yield of 0.109(10) neutrons/deuteron from the 9 Be target is a factor of two higher than that from the 12 C target, 0.056(6) neutrons/deuteron. The hardness parameters of the neutron spectra are calculated for the radiation damage studies of the silicon devices.
Beta-delayed neutron decay of 33Na
2002
Abstract Beta-delayed neutron decay of 33 Na has been studied using the on-line mass separator ISOLDE. The delayed neutron spectra were measured by time-of-flight technique using fast scintillators. Two main neutron groups at 800(60) and 1020(80) keV were assigned to the 33 Na decay, showing evidence for strong feeding of states at about 4 MeV in 33 Mg. By simultaneous β–γ–n counting the delayed neutron emission probabilities P 1n =47(6)% and P 2n =13(3)% were determined. The half-life value for 33 Na, T 1/2 =8.0(3) ms , was measured by three different techniques, one employing identifying gamma transitions and two employing beta and neutron counting.
Peculiarities in fragment mass distribution in the 238U + 40Ar (243 MeV) reaction
2001
A pronounced fine structure (FS) in the form of distinct peaks was observed in neutron gated mass spectra from the decay of the 278110 composite system produced in the reaction 238U + 40Ar (243 MeV) at an initial excitation energy E * > 70 MeV. The FS peaks are located in the vicinity of mass numbers 70-80, 100, and 130, which correspond to those of magic nuclei (clusters). In the data there is also evidence for a new type of decay -- collinear cluster tripartition of an excited nucleus.
Breakthrough in pulse-shape based particle identification with silicon detectors
2000
Identification of charged particles is an important method in nuclear spectroscopy. We have achieved a major breakthrough that makes the pulse-shape discrimination (PSD) method with a single solid-state detector comparable to and sometimes better than the traditional telescope technique. By using rear-side injection in over-biased surface barrier n-type Si detectors made from homogeneously doped n-TD silicon, and extracting the pulse-shape information already at the preamplifier level we have reached improved Z and even A discrimination over a wide dynamic range. Previously good separation with the PSD technique required a major degradation of time resolution and inferior energy resolution.…
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…
Neutron and gamma-ray emission in the proton induced fission of 238U and 242Pu
2004
Abstract Average prescission Mpren and postscission Mpostn neutron multiplicities as well as average γ-ray multiplicity 〈Mγ〉, average energy 〈Eγ〉 emitted by γ-rays as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+ 242 Pu→ 243 Am , p+ 238 U→ 239 Np at proton energy Ep=13, 20 and 55 MeV.
Beta-delayed neutron spectroscopy by the TOF technique at IGISOL: 95Rb as a test case
2003
Nuclides with a large neutron excess have high Q β values, making it possible to extract the β-strength function (SF) over a large energy range using β-decay spectroscopy. However, because of the low neutron binding energies, neutron emission from excited states will occur and β-delayed neutron spectroscopy is required to determine the SF over the full Q β window.
Fission product yields at intermediate energy
1998
The results of experimental and theoretical studies of fission product yields in proton-induced fission of 238U are presented. The yields of neutron-rich Ni, Cu, Zn, Ga and Ge—isotopes were measured by 25 MeV protons and the ion guide-based isotope separator technique. The pre-neutron emission fragment mass distributions were measured by protons at energies Ep=20, 35, 50 and 60 MeV using time-of-flight method. The results indicate enhancement for superasymmetric mass division at intermediate excitation energy of the fissioning nucleus. A model calculation of fission products yields for fission of 238U by protons and neutrons is presented which predicts the formation cross sections for neutr…
Pre- and post-scission neutron emission in the reaction180Hf(40Ar, fission) atE lab=216 MeV
1996
Neutron and fission fragment spectra following the180Hf(40Ar,f) reaction atE lab=216MeV were measured. The following neutron total, pre- and post-scission multiplicities were extracted:M tot =7.2±1.3,M pre =2.7±0.9,M post =4.5±0.9. The average temperature parameters of the neutron spectra areT pre=(1.63±0.16) MeV andT post=(1.14±0.26)MeV. The mean total kinetic energy of the fission fragments is TKE=(166±10) MeV and the measured width is σTKE=17.3MeV. The width of the fragment mass distribution is σ A =18.3u. The same reaction was analyzed using a modified statistical code which includes nuclear dissipation effects and particle and γ-ray emission in the equilibrium compound nucleus state an…
Fragment mass distribution in superasymmetric region in proton-induced fission of U and Th
1998
Fission fragment mass distributions down to super-asymmetric mass region and both pre- and post-scission neutron multiplicity for238U(p,fission) reaction atEp = 20, 35, 50, 60 MeV and for232Th(p, fission) reaction atEp = 50, 60 MeV were measured using HENDES set-up. The results indicate enhancement for super-asymmetric mass division at intermediate excitation energies.
Fine structure in fragment mass-energy distribution from 238U+40Ar (275 MeV)
2003
Existence of a new feature in fragment mass-energy distribution is reported. Careful analysis of the data obtained in the reaction 238U + 40Ar (275 MeV) shows that small but statistically significant ripples visible already in the gross mass spectrum come from extended and regular 2D patterns in the TKE vs. mass matrix. Intensity distributions of these patterns coincide with the location of heavy clusters such as 78Ni, 108Mo, or 132Sn. Presumably, the observed patterns show the dominant trajectories in the elongation vs. mass-asymmetry space of the decaying system. This information, unknown in the past, can shed a new light even on the previously well-studied reactions.
Position-sensitive neutron detector
2002
Abstract A position-sensitive neutron detector has been developed for use in nuclear physics research. The detector consists of a ∅5.5 cm×100 cm long quartz tube filled with liquid scintillator viewed from both ends by photomultipliers and enclosed in a light-tight titanium container. The properties of the detector were determined both experimentally and by Monte Carlo simulations (EFEN code). A time resolution of 0.4 ns was reached resulting in the position resolution of less than 4 cm. The neutron registration efficiency varies from 36% to 20% within neutron energy range 1–10 MeV and is practically independent of the position along the detector length. Good n–γ separation is achieved for …