J. Kvitek

Investigation of the (n, α) reaction on sm and nd isotopes in the neutron energy region below 1 keV

Abstract Alpha widths for sixteen resonances in the 149Sm(n, α) reaction have been measured on the IBR Pulsed Reactor of the Joint Institute for Nuclear Research. The results obtained are discussed together with the improved data on α-widths for the 143Nd, 145Nd and 147Sm resonances in the neutron energy region 0.04–900 eV. From the dependence of α-widths on resonance spins, spin assignment of the 143Nd resonances is made. The experimental values of the average α-widths for the given isotopes are compared with those calculated from the statistical nuclear model. The effect of neutron pairing correlations on the probability of α-decay of excited states is discussed. Alpha-width fluctuations relative to the average value are considered.

Alpha decay from excited states of samarium isotopes

The (n,α) reactions on 147Sm and 149Sm have been investigated at neutron energies up to 200 eV. The life times with respect to alpha-decay have been obtained for thirteen excited states of 148Sm and 150Sm with Jπ = 4- and 3-. Calculations, made according to the statistical theory, of the probabilities of 4- → 2+ transitions in 150Sm are in good agreement with the experiments. The life times of nine 148Sm states are in the region of 0.2 to 4 ns. The life times of the 3- and 4- levels differ by an order of magnitude.

The147Sm(n,α)144Nd Reaction on 2 keV neutrons

Using a scandium neutron filter the spectrum ofα-particles from147Sm(n, α) reaction at neutron energies around 2 keV has been measured. The partialα-widths averaged over the capturing compound states for twoα-transitions have been obtained.

The investigation of the reaction22Na(n, p)22Ne for a neutron energy to 1,000 eV

The reaction22Na(n, p)22Ne has been investigated at a neutron energy up to 1,000 eV by the time-of-flight method at the reaction IBR-30 of JINR. A neutron resonance was found in the reaction cross section. By fit, the parameters assigned to the resonance wereE0=145±11 eV;Γn0=1.6±0.2eV;Γp1=114±20eV. The presence of this resonance explains the large values for the thermal cross section of this reaction.

Experimental study of ternary fission of U235 with thermal and resonance neutrons

The alpha particle spectra from ternary fission of U235 have been investigated in the thermal and the resonance neutron energy regions. The resonance neutrons have been obtained by passing the reactor neutron flux through a boron filter. A silicon surface barrier detector telescope technique for alpha particle detection has been used. In the resonance neutron energy region the ratio 〈Γαf/Γf〈 has been found to be 1·02 ± 0·2 times the value of γαf/γf in the thermal region. The non-gaussian tail of the LRA energy distribution has been observed.

Study of the 22Na(n,p)22Ne Reaction in the Neutron Energy Range up to 1 keV

The 22Na(n,p) 22Ne reaction has been investigated at a neutron energy up to 1000 eV by the time-of-flight method at IBR-30 reactor of JINR. A neutron resonance was found in the reaction cross section. By fit, the parameters assigned to the resonance were Eo=145±11 eV; Γno; =1.6±0.2 eV; Γp1 =114±20 eV. The presence of this resonance explains large values for the thermal cross section of this reaction.

The143Nd (n.∝)140Ce reaction with 2 keV neutrons

She143Nd (n,α) reaction was investigated with 2 keV neutrons obtaiaed from a scandium filter. The cross section of (32±6) × 10−30 cm2 for averagedα-transitions from the states of144Nd compound nucleus to the140Ce ground state was obtained.

The147Sm (n, α)144Nd reaction on 2 keV neutrons

AbstractUsing a scandium neutron filter the α-particle transitions from147Sm (n, α)144Nd at 2 keV neutrons have been measured. For the α-transitions from the excited states of148Sm to the ground state of

Experimental study of the149Sm(n, α) reaction with thermal neutrons

^{144} Nd{\rm{ }}\bar \Gamma _\alpha = (5 \cdot 3{\rm{ }} \pm {\rm{ }}1 \cdot 4){\rm{ }} \times {\rm{ }}10^{ - 6}