333 research outputs found
Characteristics of light charged particle emission in the ternary fission of 250Cf and 252Cf at different excitation energies
The emission probabilities and the energy distributions of tritons, α and ^6He particles emitted in the spontaneous ternary fission (zero excitation energy) of ^250Cf and ^252Cf and in the cold neutron induced fission (excitation energy ≈ 6.5 MeV) of ^249Cf and 251Cf are determined. The particle identification was done with suited ΔE-E telescope detectors, at the IRMM (Geel, Belgium) for the spontaneous fission and at the ILL (Grenoble, France) for the neutron induced fission measurements. Hence particle emission characteristics of the fissioning systems ^250Cf and ^252Cf are obtained at zero and at about 6.5 MeV excitation energies. While the triton emission probability is hardly influenced by the excitation energy, the ^4He and ^6He emission probability in spontaneous fission is higher than for neutron induced fission. This can be explained by the strong influence of the cluster preformation probability on the ternary particle emission probability
Efficient extraction of a collimated ultra-cold neutron beam using diffusive channels
We present a first experimental demonstration of a new method to extract a
well-collimated beam of ultra-cold neutrons (UCN) from a storage vessel.
Neutrons with too large divergence are not removed from the beam by an
absorbing collimation, but a diffuse or semidiffuse channel with high Fermi
potential reflects them back into the vessel. This avoids unnecessary losses
and keeps the storage time high, which may be beneficial when the vessel is
part of a UCN source with long buildup time of a high UCN density
New experimental limits on neutron - mirror neutron oscillations in the presence of mirror magnetic field
Present probes do not exclude that the neutron () oscillation into mirror
neutron (), a sterile state exactly degenerate in mass with the neutron,
can be a very fast process, in fact faster than the neutron decay itself. This
process is sensitive to the magnetic field. Namely, if the mirror magnetic
field exists at the Earth, oscillation probability can be
suppressed or resonantly amplified by the applied magnetic field ,
depending on its strength and on the angle between and
. We present the results of ultra-cold neutron storage measurements
aiming to check the anomalies observed in previous experiments which could be a
signal for oscillation in the presence of mirror magnetic field ~G. Analyzing the experimental data on neutron loses, we obtain a new lower
limit on oscillation time s (95 % C.L.) for any
between 0.08 and 0.17 G, and s (95 % C.L.)
for any in the interval () G
- …