John D. Despotopulos's research while affiliated with Lawrence Livermore National Laboratory and other places

Publications (34)

Article
The extraction of 224Ra and 228Ac with dibenzo-21-crown-7 resin was studied in solutions with Rose Bengal and identical solutions without Rose Bengal (blanks) from pH 3 to 12. Batch studies demonstrated that actinium is extracted at high pH (> 10) from both solutions but with a significantly higher extraction from the Rose Bengal solutions (maximum...
Article
The extraction behavior of 212Pb, 197mHg, and 194Au on TEVA resin in HCl and HNO3 solutions was studied with batch uptake, kinetics, and column studies. The uptake of mercury and gold was extremely high from HCl solutions, with maximum k’ >80,000 for both elements. The uptake of mercury was lower in HNO3 than HCl with a maximum k’ of ~ 8,000 in 0.0...
Article
The extraction of no carrier added mercury by tri-isobutyl phosphine sulfide (TIBPS) was characterized in HCl and HNO3 media. The extraction of 197mHg as a function of acid concentration was similar in both acids over a large acid concentration (0.001 M to conc.) with high extraction (D ~ 1000) at low concentrations and decreasing extraction for hi...
Article
The unsaturated hexathia-18-crown-6 (UHT18C6) molecule was investigated for the extraction of Hg(II) in HCl and HNO3 media. This extractant can be directly compared to the recently studied saturated hexathia-18-crown-6 (HT18C6). The default conformation of the S lone pairs in UHT18C6 is endodentate, where the pocket of the charge density, according...
Article
The uptake behavior of 197mHg, 194Au and 212Pb in HCl on CL resin (Triskem) was studied. The extraction of mercury and gold is high (Dw > 5,000) at all concentrations of HCl, with a maximum extraction of gold at 4 M HCl (Dw ~ 53,000) and maximum extraction of mercury at 0.01 M HCl (Dw ~ 44,000). Lead has moderate uptake on CL resin (Dw ~ 100) from...
Article
The separation of zirconium and hafnium isotopes from the early actinides and rare earth elements (REE) with Eichrom’s Pb resin has been studied. Batch studies were performed to characterize the behavior of actinium, thorium, zirconium, hafnium, lutetium, and yttrium on Pb resin from HCl solutions (0.001 M to 11 M). The early actinides and REE had...
Article
A new, rapid method for isolating no-carrier-added 197m,gHg from proton irradiated Au foils has been developed based on a commercially available crown ether-containing extraction chromatography resin, Eichrom Pb resin. The separation procedure allows for loading Au dissolved in Aqua Regia directly onto a pre-packed Pb resin column. Under these cond...
Article
Full-text available
The on-going developments in laser acceleration of protons and light ions, as well as the production of strong bursts of neutrons and multi-MeV photons by secondary processes now provide a basis for novel high-flux nuclear physics experiments. While the maximum energy of protons resulting from Target Normal Sheath Acceleration is presently still li...
Article
Mercury extraction has been studied in nitric and hydrochloric acids with hexathia-18-crown-6 dissolved in carbon tetrachloride. Batch study experiments have been performed to determine the best conditions for maximum extraction. In both acids, Hg(II) was best extracted at low molarity while almost no extraction was observed above 2 M. Speciation s...
Article
The neutron activation of gold is the basis of an implosion performance diagnostic at the National Ignition Facility at Lawrence Livermore National Laboratory. In support of this diagnostic, a series of γ -ray spectrometric measurements of the decay of ¹⁹⁶ Au m 2 ( J π = 12 ⁻ ) was performed to improve the currently accepted literature values of th...
Article
We have studied some of the nuclear decay properties of Com58. The half-life is found to be (8.853±0.023) hours, which is significantly different from the evaluations found in the literature. The absolute intensity of the 24.9-keV γ ray emitted in the internal transition decay is (0.0387±0.0016)%, in agreement with the calculated yield of a transit...
Article
As a continuation of previous work (Kmak et al. in J Radioanal Nucl Chem 314:985–989, 2017), an isotope generator column based on the ²¹⁰Pb decay chain has been made to produce highly radiopure ²¹⁰Po. Two replicate studies were performed on AG 50Wx8 columns with an average yield of 90.4 ± 1.9%. ²¹⁰Pb breakthrough was seen at the 6 month elution for...
Article
A large area solid radiochemistry collector was deployed at the National Ignition Facility (NIF) with a collection efficiency for post-shot, solid target debris of approximately 1% of the total 4π solid angle. The collector consisted of a 20-cm diameter vanadium foil surrounded by an aluminum side-enclosure and was fielded 50 cm from the NIF target...
Article
Nuclear fusion experiments performed at the National Ignition Facility produce radioactive debris, arising in reactions of fast neutrons with the target assembly. We have found that postshot debris collections are fractionated, such that isotope ratios in an individual debris sample may not be representative of the radionuclide inventory produced b...
Article
A crown-ether based extraction chromatography resin, Eichrom Pb, has been characterized for separations of the flerovium (Fl) pseudo-homolog Hg. Previous results on the batch uptake of Pb(II) and Sn(IV) are compared with newly investigated Hg(II) in HCl matrices. It was determined that all three elements can be strongly retained by the resin at dif...
Article
Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z =112), nihonium (Nh, Z =113), and flerovium (Fl, Z =114), were carried out using short-lived radioisotopes. The interaction with Au and SiO 2 surfaces was studied and the overall chemical yield...
Article
A new procedure has been developed for isolating no-carrier-added 197m,gHg from 20 to 25 MeV α-particle irradiations of high purity Pt foils. A previously published procedure for isolation of 197m,gHg from 12 to 15 MeV proton irradiations of Au foils has been further characterized. From these procedures two separate methods have been established to...
Article
A simple generator using AG 50Wx8 cation exchange resin has been developed for continual elution of ²¹²Pb and ²¹²Bi from the parent radionuclide ²²⁸Th, derived from ²³²U. Using 0.4 M HCl as an eluent will elute ²¹²Bi while ²¹²Pb is eluted with 2 M HCl. The generator has shown good reproducibility of elution bands. A generator set-up in 2013 has bee...
Article
A separation of 209Po, 207Bi and 212Pb using AG 50Wx8 and AG MP 50 cation exchange resins in an HCl medium was developed. A procedure in which Po(IV) elutes first in 0.2 M HCl, followed by Bi(III) in 0.4 M HCl and finally Pb(II) in 2 M HCl was established. The separation using AG 50Wx8 provides a much better elution profile than that of AG MP 50 wi...
Article
The solid debris collection capability at the National Ignition Facility has been expanded to include a third line-of-sight assembly. The solid radiochemistry nuclear diagnostic measurement of the ratio of gold isotopes is dependent on the efficient collection of neutron-activated hohlraum debris by passive metal disks. The collection of target deb...
Article
Eichrom’s Pb resin, a crown-ether-based extraction chromatography resin, was characterized for separation of the flerovium (Fl) homologs, Pb and Sn. Batch uptake of Pb(II) and Sn(IV) radionuclides was determined from an HNO3 matrix. Pb(II) was strongly retained on the resin at all HNO3 concentrations, while Sn(IV) showed no uptake. Extraction kinet...
Article
A crown-ether-based extraction chromatography resin, Eichrom Pb resin, was characterized for separations of flerovium (Fl) homologs, specifically Pb and Sn. The batch uptake of Pb(II) and Sn(IV) radionuclides was determined from an HCl matrix. Both Pb(II) and Sn(IV) are strongly retained on the resin at different HCl concentrations. The affinity fo...
Article
Full-text available
Nuclear reaction measurements are performed at the National Ignition Facility in a high energy density plasma environment by adding target materials to the outside of the hohlraum thermo-mechanical package on an indirect-drive exploding pusher shot. Materials are activated with 14.1-MeV neutrons and the post-shot debris is collected via the Solid R...
Article
A high-purity carrier-free 7Be was efficiently isolated following proton bombardment of a lithium hydroxide–aluminum target. The separation of beryllium from lithium and aluminum was achieved through a hydrochloric acid elution system utilizing cation exchange chromatography. The beryllium recovery, +99%, was assessed through gamma spectroscopy whi...
Article
New procedures have been developed to isolate no-carrier-added (NCA) radionuclides of the homologs and pseudo-homologs of flerovium (Hg, Sn) and element 115 (Sb), produced by 12–15 MeV proton irradiation of foil stacks with the tandem Van-de-Graaff accelerator at the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry (C...
Article
Activated Au from a fragmented and dispersed NIF hohlraum is of interest to measure the induced 14.1-MeV 198m+gAu/196gAu isotope ratio as an assessment of shot performance. A radiochemical recovery procedure, based on Au complexation by cyanide in NaOH-NaCN solution, was developed to reclaim radiogold (*Au) residues from post-detonation graphite co...
Article
A diglycolamide-based resin was characterized for Group 5 (Ta, Nb and pseudo-homolog Pa) separation from Group 4 (Hf and Zr) and tri-valent actinides (Am). The batch uptake of the radionuclides of interest were determined for HNO3/HF matrices and the results were used to develop a column separation method that could be used for element 105 (Db) pur...
Article
We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,γ) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fu...
Article
The use of the Solid Radiochemistry diagnostic platform at the National Ignition Facility (NIF) has allowed the development and implementation of the Target Option Activation Device assembly for fielding materials of interest inside the NIF chamber during high yield neutron shots. Preliminary studies with ultra-depleted uranium have allowed for the...
Article
Studies of the chemical properties of superheavy elements (SHE) pose interesting challenges due to their short half-lives and low production rates. Chemical systems must have extremely fast kinetics, fast enough kinetics to be able to examine the chemical properties of interest before the SHE decays to another nuclide. To achieve chemistry on such...

Citations

... Further optimization of the platform towards a higher ion yield is of interest regarding the production of short ion bunches for ps-pulse radiolysis research [Bal08]. Single shots with high brilliance sources are ideal for not time averaged observations, promising for unprecedented insights [BZN+20]. ...
... For the lighter congener mercury (Hg), PBE-D3 provides an adsorption energy of −0.75 eV, which is in reasonable agreement with the experimental value of −1.01 eV. 59,60 The fact that the calculated value is significantly too small compared to the experiment is consistent with previous computational predictions, which are ranging from −0.32 eV (no dispersion) to −0.81 eV (revPBE-D3). 33,34,61 The difference between the calculated adsorption energies of Hg and Cn is moreover in very good agreement with the difference of the dissociation energies for the diatomic species Au-Hg and Au-Cn, [62][63][64][65] Flerovium (Fl) exhibits a pseudo closed-shell configuration due to the strong spin-orbit stabilisation of the 7p 1/2 level (splitting ≈ 4 eV), causing a dramatic difference in reactivity compared to its lighter congener Pb. ...
... In contrast to medical applications utilizing reasonably long-lived radionuclides, the off-line production of short lived radionuclides is of special interest for fundamental nuclear chemistry research, e.g., providing homologs of superheavy elements (Z ≥ 104), like lead isotopes in case of flerovium (Fl, Z = 114) [12], and bismuth isotopes for moscovium (Mc, Z = 115) [13,14]. ...
... The strongly retained in anion exchange resins were used Dowex -exchange resins. 1, Dowex-2, IR-120, AG 50 W × 8 and AG MP50 and Bio-Rad AG1-× 4 (Figgins P, 1961;Kmak KN et al., 2017;Strelow F, 1988). This procedure is usually timeconsuming (prolonged flow rate). ...
... However, hot spot mix originating from a few localized spots [31][32][33] for which data and simulations suggest a primary seed is at the capsule support tent contact lift-off location for CH [34][35][36][37] does not measurably influence the compression ratio. Specifically the tentless CH HF N160509 yielded the same (within 5%) average DSR and 4π ρR sensitive radiochemical Au isotope ratio [38] as tented shots. Fig. 1 also shows that the CH LF shot N120412 recorded the second highest DSR despite having the second highest hot spot mix level [10,42]. ...
... Work presented here is a continuation of the work in Ref. [1], ''Characterization of the homologs of flerovium with crown ether based extraction chromatography resins: studies in hydrochloric acid.'' As mentioned in [1] some predictions indicate that Fl, element 114, has a volatility and inertness greater than the other group 14 elements, which might lead to a potential chemical behavior more like Hg or a noble gas like behavior, which leads to Hg being a pseudo-homolog of Fl [2][3][4][5]. ...
... Consequently, the conditions achieved in the hot spot now enable access to a range of nuclear and astrophysical regimes. The density, temperature, and pressure of the hot spot are the closest on earth to conditions in the sun [11,12], and the neutron density (> 10 23 neutron=cc) is now relevant for nucleosynthesis studies (such as the s process), which have traditionally been in need of an intense, laboratory-based neutron source [13,14]. ...
... For these reasons, 90 Y has recently been clinically used for internal radiation therapy [2]. In the nuclear decay process, 90 Y is generated from the beta decay of 90 Sr, and the decay line of 90 [3], solvent extraction [4], ion exchange [5], use of liquid membranes [6], and extraction chromatography [7]. ...
... Tracer solutions of 212 Pb, 113 Sn and 197m Hg were prepared with activity concentrations ranging from 2 to 10 cps per 20 lL. The 113 Sn and 197m Hg were produced and isolated carrier-free as described in Ref. [12]. The 232 U (legacy material, Lawrence Livermore National Laboratory (LLNL)) decay chain was used to obtain 212 Pb as a tracer for all studies by milking the 212 Pb from a generator [13]. ...
... 22 Ne, 26 Mg, 48 Ca) to create synthetic "super-heavy elements" (Z > 103) . [25] Milligram quantities of the heavy isotopes used in targets are extracted and purified from irradiated research nuclear fuels via hydrometallurgy and notably solvent extraction and ion-exchange. [26] Over the past few decades, Oak Ridge National Laboratory (Tennessee, USA) has been at the forefront of these radio-hydrometallurgical purification processes [27] and, interestingly, element 117 has been officially named "tennessine" in 2016, not to give credit the place where it was first synthesized (Dubna, Russia), but to acknowledge the place that produced and purified the target made of 249 Bk. ...