Study of Quasielastic Barrier Distributions as a Step towards the Synthesis of Superheavy Elements with Hot Fusion Reactions

The excitation functions for quasielastic scattering of Ne22+Cm248, Mg26+Cm248, and Ca48+U238 are measured using a gas-filled recoil ion separator. The quasielastic barrier distributions are extracted for these systems and are compared with coupled-channel calculations. The results indicate that the barrier distribution is affected dominantly by deformation of the actinide target nuclei, but also by vibrational or rotational excitations of the projectile nuclei, as well as neutron transfer processes before capture. From a comparison between the experimental barrier distributions and the evaporation residue cross sections for Sg (Z=106), Hs (108), Cn (112), and Lv (116), it is suggested that the hot fusion reactions take advantage of a compact collision, where the projectile approaches along the short axis of a prolately deformed nucleus. A new method is proposed to estimate the optimum incident energy to synthesize unknown superheavy nuclei using the barrier distribution.This research was partially supported by a Grantin-Aid for Specially Promoted Research, 19002005, from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and by the U.S. DOE Office of Nuclear Physics. T. T. thanks the RIKEN Junior Research Associate Program

Superheavy element nuclear chemistry at RIKEN

金沢大学理工研究域物質化学系A gas-jet transport system has been coupled to the RIKEN gas-filled recoil ion separator GARIS to startup superheavy element (SHE) chemistry at RIKEN. The performance of the system was appraised using an isotope of element 104, 261Rf, produced in the 248Cm(18O,5n) 261Rf reaction. Alpha-particles of 261Rf separated with GARIS and extracted to a chemistry laboratory were successfully identified with a rotating wheel apparatus for α spectrometry. The setting parameters such as the magnetic field of the separator and the gas-jet conditions were optimized. The present results suggest that the GARIS/gas-jet system is a promising approach for exploring new frontiers in SHE chemistry: (i) the background radioactivities of unwanted reaction products are strongly suppressed, (ii) the intense beam is absent in the gas-jet chamber and hence high gas-jet efficiency is achieved, and (iii) the beam-free condition also allows for investigations of new chemical systems. © 2010 American Institute of Physics

Application of quantum computing techniques in particle tracking at LHC

In the near future, the LHC detector will deliver higher luminosity, causing the demand on large amount of computing resources. Therefore an efficient way to reconstruct physical objects are required. Recent studies showed that one of the quantum computing techniques, quantum annealing (QA), can be used to perform the particle tracking with efficiency higher than 90% in the high pileup region in the high luminosity environment. The algorithm starts from determining the connection between the hits, and classify the topological objects with their pattern. The current study aims to improve the pre-processing efficiency in the QA-based tracking algorithm by implementing a graph neural network (GNN), which is expected to efficiently generate the topological object needed for the annealing process. Moreover, the tracking performances with data collected from ATLAS experiment are also included

Production of Bh 266 in the Cm 248 (Na 23,5n) Bh 266 reaction and its decay properties

The nuclide 266Bh was produced in the 248Cm(23Na,5n) 266Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of 266Bh were investigated with a rotating wheel apparatus for α and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated α-α and α-SF decay chains, a total of 23 chains were assigned to 266Bh and its daughter nuclide 262Db and granddaughter 258Lr. The half-life of 266Bh was measured to be T1/2 = 10.0+2.6 −1.7 s which is an order of magnitude longer than the literature data. The α-particle energies of 266Bh disperse widely in the range of Eα = 8.62-9.40 MeV. The maximum production cross section for the 248Cm(23Na,5n) 266Bh reaction was determined to be σ = 57 +- 14 pb at 130.6 MeV, whereas the upper limit for the 248Cm(23Na,4n) 267Bh reaction was σ 14 pb at 121.2 MeV. These cross sections are discussed by comparing with the literature data as well as the theoretical calculationst. This research was partially supported by the Ministry of Education, Culture, Sports, Science, and Technology, Japan, Grant-in-Aids No. 19002005, No. 26286082, and No. 17H01081, and by the National Natural Science Foundation, China, Grants No. 11675227 and No. 11079006

High Precision Mass Measurements of Intermediate-mass Neutron-deficient Nuclei via MRTOF-MS

International audiencePrecision mass measurements of ^63Cu, ^64–66Zn, ^65–67Ga, ^65–67Ge, ^67As, ^79,81Br, ^79Kr, ^80,81Rb, and ^79,80Sr were performed with a multireflection time-of-flight mass spectrograph. The masses of these nuclides were determined by the single reference method using isobaric references. In order to obtain precise results, time-of-flight drift compensations were performed and a phenomenological fit function was employed. Consequently, in the case of ^65Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of $\delta m/m = 3.5 \times 10^{ - 8}$, was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation