DEMON is a detector array for neutrons emitted in heavy ion induced reactions at low to intermediate energies. The neutron detection efficiency of some single DEMON modules has been measured in the ...energy range 8–21 MeV, with detection thresholds down to 0.1 MeV equivalent-electron (MeVee). The influence on the efficiency of cross talk, neutron-gamma and neutron-charged particle discrimination techniques was found to be negligibly small. Monte Carlo simulations have been performed and are compared with the experimental data. The relative weight of the interaction channel
12C(n,n′γ) in the organic liquid scintillator was determined experimentally. Taking into account observed saturation effects in the detector output, a calibration method is proposed for high light outputs, based on the energy loss of cosmic ray muons.
Measurements of proton-induced fission on
232Th,
238U,
237Np,
239Pu and
241Am nuclei at proton energies of 26.5 MeV and 62.9 MeV were performed at the Louvain-la-Neuve cyclotron facility. Neutrons ...were detected with the multidetector DEMON. Mass and energy distributions of fission fragments, neutron angular distribution and multiplicities and total fission cross sections were determined. The relative contributions of pre-equilibrium neutron emission and compound nucleus evaporation, as well as of post-scission evaporation from the fission fragments were analyzed with moving multisource fits and were also compared with the predictions of the nuclear-reaction model code TALYS. Detailed comparisons with the data indicate that there is still room for improvement in this code.
The unbound nucleus He7 has been investigated via the reaction of a 16.8 MeV He6 radioactive ion beam on a Be9 target. The measurement of the outgoing Be8 through its well characterized two-α decay ...permitted the energy of the He6+n system to be reconstructed. Through comparison with a complete Monte Carlo simulation incorporating R-matrix lineshapes, the He7 ground state was determined to lie 0.380(28) MeV above the neutron decay with a width of Γ=0.179(21) MeV. A neutron spectroscopic factor SF=0.608(18) was extracted in agreement with the most recent calculations. Significant evidence was found for a broad resonance lying at 2.6(2) MeV above threshold with a ΓFWHM=2.3(3) MeV. These parameters are fully consistent with the properties of 1/2− state reported by Wuosmaa et al. Phys. Rev. C 72, 061301(R) (2005). Limits were also put on the presence of narrow resonances seen in earlier experiments.
At finite temperatures and low densities, nuclei may undergo a phase change similar to a classical liquid-gas phase transition. Temperature is the control parameter while density and pressure are the ...conjugate variables. In the nucleus the difference between the proton and neutron concentrations acts as an additional order parameter, for which the symmetry potential is the conjugate variable. We present experimental results which reveal the N/Z dependence of the phase transition and discuss possible implications of these observations in terms of the Landau free energy description of critical phenomena.
Elemental analysis of light constituents in thin plastic films El Masri, Y.; Heitz, Ch; Keutgen, Th ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
04/2009, Letnik:
267, Številka:
7
Journal Article
Recenzirano
Experiments with 1–3
MeV
4He beams and 2.2–3.2
MeV proton beams have been performed in order to develop a precise and highly sensitive method for the detection and analysis of light elements in ...threat or drug materials using simultaneously the RBS and ERDA techniques. Commercially available plastic films have been used as samples. The 1
MeV
4He beam has been found to be inadequate owing to the rapid destruction of the targets. Best results have been obtained using proton beams with energies higher than 3
MeV. For 3.2
MeV proton beams, ERDA has been used for the analysis of the hydrogen constituent.
Inclusive cross sections (
d
2
σ
d
Ω
d
E
,
d
σ
d
E
,
d
σ
d
Ω
and
σ
T
) for the production of neutron and light charged particles induced by protons of 26.5, 48.5 and 62.9 MeV and alpha-particles of ...25.4, 45.5 and 57.8 MeV on
natSi targets have been measured. The secondary particles (
p,
d,
t,
3He,
α,
6Li,
7Li and
7Be) were detected at angles from 10° to 165° in steps of ±10° with respect to the beam axis. Neutrons emitted in these reactions were only recorded in coincidence with, at least, one detected light charged particle. A comparison of the proton- and neutron-induced reactions on Si at
E
=
62
MeV
shows evidence of charge independence of the nuclear force. The proton spectra from the two reactions scale as expected from the difference in proton–neutron and proton–proton quasi-free scattering cross sections. The new data are reproduced with moving source fits and are also compared with state-of-the-art nuclear reaction models. The codes used for this purpose, GNASH and TALYS, consider direct nuclear reactions as well as pre-equilibrium and compound nucleus emission, and were found to reproduce the general features of the experimental data, especially for the
(
p
,
p
x
)
channel. More detailed comparisons with the data indicate that there is still room for improvement in these codes.
6He + 9Be reactions at 16.8 MeV Majer, M.; Raabe, R.; Milin, M. ...
The European physical journal. A, Hadrons and nuclei,
02/2010, Letnik:
43, Številka:
2
Journal Article
Recenzirano
Reactions of a 16.8 MeV
6
He beam with a
9
Be target have been investigated using highly segmented detector setup covering a large solid angle. Data on elastic and quasi-free scattering, as well as ...two-neutron transfer, are reported. The results for elastic scattering are fairly well reproduced by a CDCC calculation, in agreement with the interpretation of a breakup effect already observed for the scattering of
6
He on other light targets. Exotic quasi-free scattering of
6
He on
-cluster in
9
Be is clearly observed. Inclusive and coincident events were used to extract information on the two-neutron transfer reaction
9
Be(
6
He,
)
11
Be . Sequential decay of the
11
Be state at the excitation energy
MeV through different channels is discussed.
6He + 9Be reactions at 16.8 MeV MAJER, M; RAABE, R; LAPOUX, V ...
The European physical journal. A, Hadrons and nuclei,
2010, Letnik:
43, Številka:
2
Journal Article
Neutron-induced fission cross-sections of
205Tl,
204,206,207,208Pb and
209Bi have been measured in the energy range from 30 to 180
MeV. The measurements were performed with quasi-monoenergetic ...neutron beams using a multi-section Frisch-gridded ionization chamber. The neutron-induced fission cross-sections of
238U were used as reference data. The experimental techniques are described in detail as well as the data processing. The results are compared with existing experimental data.
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