A. O. Strekalovsky

Status and prospects of investigations into the collinear cluster decay of heavy nuclei

Basic experimental results confirming the existence a new cluster-decay type called collinear cluster tripartition (CCT) are presented. Decays of this type manifest themselves, in particular, as a two-dimensional region of a locally enhanced yield of fragments (bump) that corresponds to specific missing-mass values in the mass-mass distribution of fission fragments. One of the decay modes that contribute to the bump can be treated as a cluster-decay type that is new in relation to the well-known heavy-ion or lead radioactivity. The conclusions drawn from an analysis of correlation mass distributions are confirmed by the results obtained from neutron-gated data, measurements of the nuclear charge for CCT events, and the direct detection of new-decay products.

Preliminary Results on Observation of New Shape Isomers

In our previous publications devoted to the collinear cluster tri-partition (CCT) of the low excited nuclei [1, 2] we have discussed the role of scattering medium in the registration of the CCT products.

Examination of evidence for collinear cluster tri-partition

CITATION: Pyatkov, Yu. V., et al., 2017. Examination of evidence for collinear cluster tri-partition. Physical Review C, 96(6):1-16, doi:10.1103/PhysRevC.96.064606.

Analysis of some modes of multibody decays of low excited actinide nuclei

At the previous ICPPA (2015) we presented the report [1] where we discussed the results of the solution of the problem of estimation of statistical reliability of linear point structures, obtained from the experiments at the FOBOS spectrometer [2] dedicated to study of the spontaneous fission of the 252Cf nucleus in the mass correlation distribution of fission fragments. These new unusual structures bounded by magic clusters were interpreted as a manifestation of a new exotic decay called collinear cluster tri-partition (CCT) [3]. The reliability of these structures was estimated on the basis of methods of morphological image analysis [1], [4], [5]. To improve the quality of revealing and further estimation of linear structures statistical reliability in the mass correlation distribution of fission fragments we used the formalism of oblique projecting [6] and subjective modeling [7], [8].

Time-of-flight measurements of heavy ions using Si PIN diodes

A new off-line timing method for PIN diode signals is presented which allows the plasma delay effect to be suppressed. Velocities of heavy ions measured by the new method are in good agreement within a wide range of masses and energies with velocities measured by time stamp detectors based on microchannel plates.

Experimental testing of heavy ions mass search procedure in the measurements with PIN diodes

We discuss the quality of heavy ions (HI) mass reconstruction in the wide range of HI energies and masses using Si PIN diodes for measuring both energy and time-of-flight. The results are based on the experimental data obtained at the IC-100 accelerator in the Flerov Laboratory of the JINR (Dubna, Russia).

New Kind of Nuclear Multi-body Decay (CCT)—Status and Perspectives of Studies

The present paper is devoted to the observation of a new kind of ternary decay of low-excited heavy nuclei. This decay mode has been called by us “collinear cluster tri-partition” (CCT) in view of the observed features of the effect, that the decay partners fly’ apart almost collinearly and at least one of them has magic nucleon composition.

EXPERIMENTAL TESTING OF THE HI MASS RECONSTRUCTION PROCEDURE AT LIS SETUP

Reconstruction of the heavy ion masses in the time-of-flight spectrometry is known to be a complicated task due to distortions both in timing and measuring of the ions energy using PIN diodes. Original procedure which takes into account simultaneously pulse height defect (PHD) and plasma delay for unbiased mass reconstruction was tested in series of experiments at the LIS setup using degrader foils.

STATUS OF THE VEGA PROJECT

Motivation and status of the VEGA (Velocity-Energy Guide based Array) project is presented. One armed fission fragments spectrometer with an electrostatic guide system is proposed for installation at the vertical experimental channel of the IBR-2 reactor. Scientific program aimed at investigation of new multi-body decays of actinides, shapeisomeric states in fission fragments and fission modes is reported.

STUDY OF SHAPE ISOMERIC STATES IN FISSION FRAGMENTS

In one of our experiments aimed at studying of the new multi-body decay called collinear cluster tri-partition (CCT) [1–3] additional absorber (Ti foil) was introduced just after the source at the distance of approximately 1 mm. It was motivated by the peculiarity of the CCT manifestation in the experiments namely specific structures in the region of an essential missing mass in the fission fragments (FFs) mass correlation distribution were observed in the spectrometer arm faced to the Cf source backing only. The effect was traced back to some angular divergence between two CCT partners flying in the same direction after passing the scattering medium on the flight pass due to the multiple scattering. As a result one of them can be lost in the PIN diode frame what is observed as” missing mass” or both fragments will be detected independently in the neighboring diodes. We have observed significant mass deficit in the total mass of the fission fragments detected in coincidence with Ti ions knocked out from the foil (fig. 1) [4]. For the sake of convenience, the FFs from such events are labeled as M1, M2 and M3 in an order of decreasing masses in the ternary event. The total mass of the two heavier fragments Ms = M1 + M2 is plotted vs. the mass of the lighter fragment M3. Such effect could be expected if the scattered fragment looks like a di-nuclear system destroying due to inelastic scattering on the Ti nucleus. A mean flight time between the Cf source and the foil does not exceed 0.1 ns. It can be regarded as a low limit for the life time of the di-nuclear system (shape isomer).