FLNR SCIENTIFIC AND TECHNICAL COUNCIL MEETINGS AND SCIENTIFIC SEMINARS|
27.04.2018 - FLNR Scientific Seminar "Study of fusion-fission and quasi-fission of Z=102-116 superheavy elements in reactions with 48Ca ions.", 15-30, Flerov Lab Conference Hall.
Speaker: E.V.Chernyshova (On Candidate's thesis)
This work concerns the study of the competition of the processes of fusion-fission and quasi-fission in reactions of 48Ca double magic ions with 208Pb double-magic spherical nucleus and with 232Th, 238U, 244Pu, 248Cm deformed actinide targets. Experiments were performed at U400 accelerator complex using CORSET double-arm time-of-flight spectrometer (CORSET - CORrelation SETup). Mass-energy distributions (MEDs) of reaction fragments and capture cross- sections were measured.
Our studies show that for 48Ca+208Pb reaction 256No compound nucleus fusion-fission is the dominant channel. Quasi-fission in this reaction appears only for ML ~ 60-90 a.m.u. light fragment mass and MH ~ 166-196 a.m.u. heavy fragment mass.
In reactions of 48Ca ions with 232Th, 238U, 244Pu, 248Cm actinide targets the QFasym asymmetric quasi-fission with the heavy fragment peak in the area of double-magic Pb (MH >> 208 a.m.u.) is the main reaction channel. Analysis of fragment energy distributions was developed and used to divide MED fragments into FF fusion-fission, QFsym symmetric and QFasym asymmetric quasi-fission components.The analysis shows that for 48Ca + 238U, 244Pu and 248Cm reactions at Elab= 230-245 MeV energies fragments with M = A/2 ± 20 a.m.u. by energy characteristics mostly belong to fusion-fission process. SFF fission cross-sections, Wsur survival probabilities, 254-256No, 283-286Cn, 289-292Fl, 293-296Lv nuclei lower limits of fission barriers were estimated analysing energy characteristics.
26.04.2018 - FLNR STAD Scientific Seminar "Permanent magnet deflecting system with adjustable angle of beam deflection", 11-00, Flerov Lab, b.131, room 250, second floor.
Deflecting system of two modules of permanent dipole magnets is under consideration in this work. Permanent neodymium (NdFeB) magnets are magnetizing elements of each module. Beam deflection angle may be adjusted by module rotation. May be used as a beam path adjuster. Our adjuster is smaller in size at the given field integral, cheaper in operation with higher operational reliability.
25.04.2018 - FLNR Chemical Seminar, 15-30, Flerov Lab Conference Hall
Speaker: Paul Ionescu, Paul Scherrer Institute
On the road to understanding the chemistry of the presently heaviest known elements, one must look for inspiration in nature. Presented will be the pathway to better understanding the chemistry of superheavy elements Copernicium (Z=112) and Flerovium (Z=114) through the use of gas chromatography. Experiments were performed using the lighter homologue mercury on a selenium surface as a model off-line. This method was used to differentiate between different selenium allotropes and to develop alpha-spectroscopy detectors for the use in chromatographic separation of superheavy elements in Dubna 2018, which will provide further insight into relativistic effects on the electron shell as well as on the volatility of Cn.
Speaker:Yuri Demidov, Institure of Nuclear Physics, St.Petersburg
Empirical regularities between adsorption enthalpies of heavy element atoms and properties of two-atom molecules are discussed in this work. The main energy characteristics and equilibrium configurations of PoAu, PoAg, PoPt, PoCu were found. Binding energies of these molecules were compared with experimental adsorption enthalpies of Po atoms on gold, silver, platinum, copper surfaces. Mercury was compared likewise. Peculiarities of Cn and Fl electronic structures in the adsorption on different metal surfaces are discussed.
02.04.2018 - FLNR Scientific Seminar "Particle fluxes from clouds and Lightning initiation", 16-00, Flerov Lab Conference Hall
Speaker: Ashot Chilingarian for SEVAN Collaboration
Yerevan Physics Institute, Armenia
Strong electric fields emerging in the clouds accelerate and multiplied seed electrons from the ambient population of cosmic rays. However, measurements in South Africa initiated by C.T.R. Wilson in the first half of last century fail to prove the existence of high-energy radiation. Only last decades there was noticeable progress in detecting radiation and particles from the thunderclouds by orbiting gamma-ray observatories and particle detectors located on balloons, aircraft and on the earth’s surface. However, reported fluxes were very brief ranging from microseconds to few minutes. The relationship of lightning and particle fluxes (electrons, gamma rays and neutrons) in the thunderclouds is not fully understood to date. Using the particle beams (the so-called Thunderstorm Ground Enhancements – TGEs) as a probe we investigate the characteristics of the interrelated atmospheric processes. The continuous monitoring of particle fluxes, electric fields, and meteorological conditions during thunderstorms on Aragats performed last decade, provides insights into the overall radiation produced in clouds and shows that particle fluxes are many orders of magnitude larger than expected from the previous measurements. Networks of NaI spectrometers sensitive to energy ranges 0.3 – 50 MeV have shown by measured differential energy spectra of electrons and gamma rays that particle fluxes can last for many hours and that avalanches continuously develop in different locations of a huge thundercloud. That may change common expectation in many areas ranging from Carbon dating until aircraft crew safety. The experiments using the terrestrial atmosphere as a target, i.e. surface arrays registering Extensive Air Showers(EASs) and Atmospheric Cherenkov Telescopes (ACTs) should introduce corrections to energy estimates of primary hadrons and gamma rays introduced by the particle propagation in the extended intracloud electric fields.
The SEVAN collaboration last 10 years explored the Solar Physics and Space Weather issues. Now we plan to investigate particle fluxes from the newly discovered cloud radiation in all details. The link of the particle detector data with atmospheric physics already tested at Aragats proves that SEVAN network can be a unique instrument for research of coupling of solar and atmospheric effects. We need to install on SEVAN sites in Eastern Europe the sensors of the electric field and perform joint measurements to find out the relation of solar activity, intracloud electric fields and radiation from clouds on climate change issues. Thus, we plan to path the gap in our knowledge of high energy processes in the clouds and how these processes along with solar activity influence the terrestrial climate.