Dr Rafael Van den Bossche
Academic and research departments
About
My research project
Modelling incomplete fusion of complex nuclei at Coulomb energies: Superheavy element formationSuperheavy elements (SHE) have an atomic number Z ≥ 104, and their existence was predicted almost 50 years ago due to quantum shell effects that influence their stability and decay [1]. SHE production is very challenging (due to very small cross sections in the range of a few picobarns or less), with complete fusion of heavy ions being one of the most successful ways of producing SHEs. The complete fusion mechanism produces neutron-deficient SHEs, making investigation into new methods of production crucial for further progress in SHE research.
The aim of the project is to investigate the incomplete fusion of neutron-rich projectiles with heavy stable targets, following the binary fragmentation of a projectile at Coulomb energies. This mechanism has not been thoroughly explored yet, and could prove to be an effective way of producing neutron-rich SHE isotopes with low excitation energies [2].
To this aim, a semi-classical dynamical model is being developed by combining a classical trajectory model with stochastic breakup, as implemented in the PLATYPUS code [3], with a dynamical fragmentation theory [4] treatment of two-body clusterisation and decay of a projectile. A finite-difference method solution to the time-independent Schrödinger equation in the charge asymmetry coordinate is being explored by way of diagonalising a tridiagonal matrix with periodic boundary conditions.
Ultimately, this new model will be tested against existing experimental data [2] and used to make predictions for producing new SHE isotopes in future experiments planned at the Joint Institute for Nuclear Research in Dubna, Russia, and elsewhere [5].
References:
[1] S. Hofmann et al., Eur. Phys. J. A 52 (2016) 180.
[2] C. Borcea et al., Nucl. Phys. A 415 (1984) 169, and references therein.
[3] A. Diaz-Torres, J. Phys. G 37 (2010) 075109; Computer Physics Communication 182 (2011) 1100.
[4] S.N. Kuklin et al., Eur. Phys. J. A 48 (2012) 112.
[5] C. Borcea et al., “Superheavy Elements: A New Paradigm”, Proc. Int. Symp. on `````Exotic Nuclei (EXON-2016), http://www.worldscientific.com/doi/abs/10.1142/9789813226548_0021.
Supervisors
Superheavy elements (SHE) have an atomic number Z ≥ 104, and their existence was predicted almost 50 years ago due to quantum shell effects that influence their stability and decay [1]. SHE production is very challenging (due to very small cross sections in the range of a few picobarns or less), with complete fusion of heavy ions being one of the most successful ways of producing SHEs. The complete fusion mechanism produces neutron-deficient SHEs, making investigation into new methods of production crucial for further progress in SHE research.
The aim of the project is to investigate the incomplete fusion of neutron-rich projectiles with heavy stable targets, following the binary fragmentation of a projectile at Coulomb energies. This mechanism has not been thoroughly explored yet, and could prove to be an effective way of producing neutron-rich SHE isotopes with low excitation energies [2].
To this aim, a semi-classical dynamical model is being developed by combining a classical trajectory model with stochastic breakup, as implemented in the PLATYPUS code [3], with a dynamical fragmentation theory [4] treatment of two-body clusterisation and decay of a projectile. A finite-difference method solution to the time-independent Schrödinger equation in the charge asymmetry coordinate is being explored by way of diagonalising a tridiagonal matrix with periodic boundary conditions.
Ultimately, this new model will be tested against existing experimental data [2] and used to make predictions for producing new SHE isotopes in future experiments planned at the Joint Institute for Nuclear Research in Dubna, Russia, and elsewhere [5].
References:
[1] S. Hofmann et al., Eur. Phys. J. A 52 (2016) 180.
[2] C. Borcea et al., Nucl. Phys. A 415 (1984) 169, and references therein.
[3] A. Diaz-Torres, J. Phys. G 37 (2010) 075109; Computer Physics Communication 182 (2011) 1100.
[4] S.N. Kuklin et al., Eur. Phys. J. A 48 (2012) 112.
[5] C. Borcea et al., “Superheavy Elements: A New Paradigm”, Proc. Int. Symp. on `````Exotic Nuclei (EXON-2016), http://www.worldscientific.com/doi/abs/10.1142/9789813226548_0021.
Areas of specialism
University roles and responsibilities
- Demonstrator for undergraduate Physics classes.
Affiliations and memberships
Publications
Using a semi-classical dynamical model that combines a classical trajectory model with stochastic breakup with a dynamical fragmentation theory treatment of two-body clusterisation and decay of a projectile, results are presented for 20Ne-induced incomplete fusion reactions for the production of superheavy elements. Targets include 247,248,250Cm and 251,252,254Cf, and results include angular, excitation energy and angular momentum distributions in addition to total integrated cross sections for heavy incomplete fusion products. The results show that at Coulomb energies, the studied Cf isotopes are generally the more favourable choice of target over the studied Cm isotopes for the production of `colder’ and more stable 263Lr, 263,264,266Rf and 265Db isotopes through the ICF mechanism. Also presented are evaporation residue cross sections for the dominant primary incomplete fusion products of each of the six reactions: 263,264,266Rf and 267,268,270Sg, as well as for the primary incomplete fusion products 269,270,272Bh.
The incomplete fusion dynamics of 20Ne + 208Pb collisions at energies above the Coulomb barrier are investigated using a novel semiclassical dynamical model, which combines a classical trajectory model with stochastic breakup, as implemented in the platypus code, with a dynamical fragmentation theory treatment of two-body clusterization and decay of a projectile. A finite-difference method solution to the time-independent Schrödinger equation in the charge asymmetry coordinate is employed by way of diagonalizing a tridiagonal Hamiltonian matrix with periodic boundary conditions. Results are compared with published experimental values to indicate the success of this new model, and next steps for its development are detailed.
The eutectic alloys rhenium–carbon, platinum–carbon and cobalt–carbon have been proposed as reference standards for thermometry, with temperature and uncertainty values specified within the mise en pratique of the definition of the kelvin. These alloys have been investigated in a collaboration of eleven national measurement institutes and laboratories. Published results reported the point-of-inflection in the melting curve with extremely low uncertainties. However, to be considered as standards it is necessary to stipulate what phenomenon a temperature value has been ascribed to; specifically, this should be a thermodynamic state. Therefore, the data have been further evaluated and the equilibrium liquidus temperatures determined based on a consideration of limits and assuming a rectangular probability distribution. The values are: for rhenium–carbon 2747.91 ± 0.44 K, for platinum–carbon 2011.50 ± 0.22 K and for cobalt–carbon 1597.48 ± 0.14 K, with uncertainties at approximately a 95% coverage probability. It is proposed that these values could be used as the basis of thermodynamic temperature measurement at high temperatures (above 1300 K).
The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.