Engineering topics

Roberto, James B.

Publications and source records attributed to Roberto, James B..

5 records

DOE OSTI2023

Actinide targets for the synthesis of superheavy nuclei

The use of heavy actinide targets, including 243 Am, 240,242,244 Pu, 245,248 Cm, 249 Bk, and 249 Cf, irradiated by intense heavy ion beams of 48 Ca has resulted in a significant expansion of the periodic table since 2000, including the discovery of five new heaviest elements and more than 50 new isotopes. These actinide materials can only be produced by intense neutron irradiation in very high flux reactors followed by chemical processing and purification in specialized hot cell facilities available in only a few locations worldwide. This paper reviews the reactor production of heavy actinides, the recovery and chemical separation of actinide materials, and the preparation of actinide targets for superheavy element experiments. The focus is on 248 Cm, 249 Bk, mixed 249–251 Cf, and 254 Es, including current availabilities and new production processes. The impacts of new facilities, including the Superheavy Element Factory at Dubna, accelerator and separator upgrades at RIKEN, and proposed upgrades to the High Flux Isotope Reactor at Oak Ridge are also described. Examples of recent superheavy element research are discussed as well as future opportunities for superheavy research using actinide targets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

New isotope 286 Mc produced in the 243 Am + 48 Ca reaction

In this paper, we present results of the second experiment on the synthesis of Mc isotopes in the 243 Am + 48 Ca reaction performed at the gas-filled separator DGFRS-2 of the SHE Factory at JINR. Here, the new isotope 286 Mc was synthesized, and its half-life of $20^{+98}_{–9}$ ms and α-particle energy of 10.71 ± 0.02 MeV were determined. A 286 Mc α–decay chain was recorded down to the spontaneous fission of 266 Db. The spontaneous fission of 279 Rg was observed for the first time in one of four new decay chains of 287 Mc. The excitation function of the reaction was measured at three 48 Ca energies of 242, 250, and 259 MeV; the latter resulted in the first observation of the 5$\textit{n}$–evaporation channel with a cross section of $0.5^{+1.3}_{–0.4}$ pb. The decay properties of 21 previously known odd–$\textit{Z}$ isotopes were improved. The potential for an electron-capture decay mode is discussed for 288 Mc and 284 Nh isotopes. The half-lives of spontaneously fissioning nuclei produced in the 48 Ca–induced reactions with actinide targets are compared with several theoretical predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Investigation of 48 Ca-induced reactions with 242 Pu and 238 U targets at the JINR Superheavy Element Factory

Experiments using a 48 Ca beam on 238 U and 242 Pu targets to produce superheavy nuclei were performed at the gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the SHE Factory at JINR. The decay properties of 286 Fl and 287 Fl, as well as their α-decay products, were refined after the detection of 25 and 69 new decay chains, respectively. In addition, 16 decay chains of 283 Cn were observed in the 238 U+ 48 Ca reaction. The possibility of existing of isomeric states in the 287 Fl consecutive α decays is discussed. A new α line with an energy of 100–200 keV lower than the main one at 10.19 MeV was observed for the first time for even-even 286 Fl decay. A maximum cross section of $10.4^{+3.5}_{-2.1}$pb was measured for the 242 Pu( 48 Ca,3n) 287 Fl reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Probing Optimal Reaction Energy for Synthesis of Element 119 from 51 V+ 248 Cm Reaction with Quasielastic Barrier Distribution Measurement

Here, the quasielastic barrier distribution of 51 V+ 248 Cm was extracted by measuring the excitation function of quasielastic backscattering using a gas-filled recoil ion separator, GARIS-III. The obtained barrier distribution is well explained by the coupled-channels calculation, indicating a significant effect of the rotational excitation of deformed 248 Cm. From the measured average Coulomb barrier height and deformation parameters of 248 Cm, the side-collision energy leading to a compact configuration of colliding nuclei was obtained. The relation between the side collision energy and the excitation function of the evaporation-residue cross sections in the 48 Ca+ 248 Cm system was evaluated as a reference for the 51 V+ 248 Cm case. The optimal reaction energy to synthesize a new element 119 at the 51 V+ 248 Cm fusion reaction (3n and 4n channels) was estimated with an aid of these experimental data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

First Experiments: New Science Opportunities at the Spallation Neutron Source Second Target Station (abridged)

This brochure is an abridged version of a more comprehensive companion report. DOE proposes to build a Second Target Station (STS) at SNS to produce beams of cold neutrons with world-leading peak brightness at a repetition rate of 15 Hz, providing broad energy/wavelength ranges that can be used simultaneously. Construction of the STS will provide transformative capabilities that allow thousands of users from national laboratories, universities, and industry to address grand scientific challenges [Hemminger 2015], advance energy research, and accelerate industrial innovations through the combination of cold (long-wavelength) neutrons of unprecedented peak brightness and short neutron pulses with broad ranges of usable wavelengths or energy. The STS Project, now in progress at ORNL, will design, construct, install, and commission the facilities and equipment needed to create a world-leading source of cold neutrons of unprecedented peak brightness at SNS. Key aspects of the STS design, including preliminary descriptions of an illustrative suite of eight instruments, are presented in the section “The STS at SNS.” The capabilities offered by the STS instruments (22 when fully built out) will complement those of the FTS and HFIR, providing the United States with unparalleled resources for neutron scattering at the world’s leading high–peak brightness cold neutron source.

43 PARTICLE ACCELERATORS↗