High Isotopic Purity Research Articles

Tritium neutral beam injection on JET: calibration and plasma measurements of stored energy

Neutral beam injection (NBI) is a flexible auxiliary heating method for tokamak plasmas, capable of being efficiently coupled to the various plasma configurations required in the Tritium and mixed deuterium-tritium experimental campaign on the Joint European Torus (JET) device. High NBI power was required for high fusion yield and alpha particle studies and to provide mixed deuterium-tritium (D-T) fuelling in the plasma core, it was necessary to operate the JET NBI systems in both deuterium and tritium. Further, the pure tritium experiments performed required T NBI for high isotopic purity and reduced 14 MeV neutron yield. Accurate power calibrations are also essential to machine safety. Previously on JET there have been a number of questions raised on the NBI power calibration, in particular following the Trace Tritium Experiments (TTEs). Operator activities on the tokamak NBI system, including calibrations, were performed in 2020. Following these activities, a series of plasma experiments were devised to further corroborate the T NBI power by comparing the plasma response to the D NBI power. A series of stationary, L-mode plasmas were performed on JET with different beam combinations used in different phases of the same pulse. By comparing the plasma response for D and T NBI it was possible to corroborate the T NBI power calibration using the D NBI power calibration. The stored energy as measured by magnetic diagnostics, corrected for fast particle stored energy, show that the uncertainty in NBI power calibration in T is comparable to that in D.

Precision Deuteration Using Cu-Catalyzed Transfer Hydrodeuteration to Access Small Molecules Deuterated at the Benzylic Position.

A highly regio- and chemoselective Cu-catalyzed aryl alkyne transfer hydrodeuteration to access a diverse scope of aryl alkanes precisely deuterated at the benzylic position is described. The reaction benefits from a high degree of regiocontrol in the alkyne hydrocupration step, leading to the highest selectivities reported to date for an alkyne transfer hydrodeuteration reaction. Only trace isotopic impurities are formed under this protocol, and analysis of an isolated product by molecular rotational resonance spectroscopy confirms that high isotopic purity products can be generated from readily accessible aryl alkyne substrates.

Generation of 13C-Labeled Inositol and Inositol Phosphates by Stable Isotope Labeling Cell Culture for Quantitative Metabolomics.

Inositol and inositol phosphates (IPx) are central metabolites. Their accurate quantitative analysis in complex biological samples is challenging due to lengthy sample preparation procedures, sample losses by strong adsorption to surfaces, and unpredictable matrix effects. Currently, U13C-inositol and U13C-IPx are not available from commercial sources. In this study, we developed a method that is capable of generating U13C-inositol and U13C-IPx. An inositol-independent cell line L929S was cultured in inositol-free medium supplemented with U13C-glucose. Inositol contamination in FBS was observed as the critical parameter for labeling efficiency (LE). A balance between cell growth and LE was achieved by adopting a two-step labeling strategy. In the first step, a LE of 90% could be obtained by normal cell growth in the long-term. Cells were then cultured in a second step in ultra-labeling medium for improved LE for a short duration before harvesting. The generated U13Canalogs were of high isotopic purity (>99%). Utilized as internal standards spiked before sample preparation in biological applications, U13Canalogs can effectively compensate sample loss during sample preparation as well as the matrix effect during electrospray ionization. An exemplary pharmacological study was conducted with phospholipase C inhibitor and activator to document the great utility of the prepared stable isotope-labeled internal standards in elucidating the PLC-dependent IP code. U13CIPx are used as internal standards to generate quantitative profiles of IPx in HeLa cell samples after treatment with PLC inhibitor and activator. This established method generating U13Canalogs is cost-effective, robust, and reproducible, which can facilitate quantitative studies of inositol and IPx in biological scenarios.

Strong Isotopic Fractionation of Oxygen in TiO2 Obtained by Surface-Enhanced Solid-State Diffusion.

Isotopically pure semiconductors have important applications for cooling electronic devices and quantum computing and sensing. Raw materials of sufficiently high isotopic purity are expensive and difficult to obtain; therefore, a post-synthesis method for removing isotopic impurities would be valuable. Through isotopic self-diffusion measurements of oxygen in rutile TiO2 single crystals immersed in water, we demonstrate fractionation of 18O by a factor of 3 below natural abundance in a near-surface region up to 10 nm wide. The submerged surface injects O interstitials that displace lattice 18O deeper into the solid as a result of the statistics of interstitialcy-mediated diffusion combined with steep chemical gradients of O interstitials. Slightly acidic and slightly basic liquid solutions both enhance the fractionation and affect the details of isotopic profile shapes through several chemical and physical mechanisms.

Production of Four 15N-Labelled Cobalamins via Biosynthesis Using Propionibacterium freudenreichii.

Cobalamins (vitamin B12) are required by humans for their essential roles as enzyme cofactors in diverse metabolic processes. The four most common cobalamin vitamers are hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl). Humans are not able to synthesise cobalamins de novo and thus must acquire them from external sources. Therefore, a reliable and robust analytical method to determine the cobalamins in dietary sources is highly required. For such a purpose, stable isotope dilution assays (SIDAs) with LC-MS/MS are most suited due to their superior sensitivity, specificity, and ability to compensate for matrix effects and analyte loss during sample work-up. However, a critical bottleneck for developing a SIDA method for cobalamins is the availability of stable isotope-labelled internal standards. In the present study, we harnessed the potential of Propionibacterium (P.) freudenreichii for the biosynthesis of 15N-labelled cobalamins. First, we developed a chemically defined medium (CDM) containing ammonium sulphate as a single nitrogen source except three essential vitamins that supported long-term stable growth of P. freudenreichii throughout continuous transfers. The CDM was further optimised for cobalamin production under different incubation schemes. With the optimised CDM and incubation scheme, fully 15N-labelled cobalamins were obtained in P. freudenreichii with a final yield of 312 ± 29 μg/L and 635 ± 102 μg/L, respectively, for [15N]-OHCbl and [15N]-AdoCbl. Additionally, an optimised incubation process under anaerobic conditions was successfully employed to produce specifically labelled [15N, 14N2]-cobalamins, with a yield of 96 ± 18 μg/L and 990 ± 210 μg/L, respectively, for [15N, 14N2]-OHCbl and [15N, 14N2]-AdoCbl. The labelled substances were isolated and purified by solid phase extraction and semi-preparative HPLC. Chemical modifications were carried out to produce [15N]-CNCbl and [15N]-MeCbl. Eventually, 15N-labelled compounds were obtained for the four cobalamin vitamers in high chromatographic and isotopic purity with desired 15N-enrichment and labelling patterns, which are perfectly suited for future use in SIDAs or other applications that require isotopologues.

Combination of DGA and LN Columns: A Versatile Option for Isotope Production and Purification at Oak Ridge National Laboratory

ABSTRACT The chromatographic resins DGA and LN have been used sequentially to separate curium, californium, plutonium, and various fission products (FPs) to obtain products with a pure radioisotope or a radioelement with high isotopic purity. This 2-step combination of resins has found applications in the 252Cf and 238Pu campaigns performed at Oak Ridge National Laboratory. Experiments have been carried out in glove boxes, shielded caves, and hot cells, demonstrating that these resins are adequate and maintain their performance in highly radiolytic environments. Using these resins has led to the recovery of curium highly enriched (>95%) in 248Cm, the clean separation of 251Cf for the superheavy element research, and the recovery of 147Pm from the FP stream obtained during the 238Pu production campaign while demonstrating that the raffinate post DGA is essentially free of transuranic elements.

Isotope analysis of highly enriched “silicon-28” by high-resolution inductively coupled plasma mass spectrometry using an internal standard

In order to study the isotopic effects in semiconductor materials, single crystals of high chemical and isotopic purity are required. The reliability of the obtained data on the magnitude and the direction of isotopic shifts depends on the accuracy of determining the concentration of all stable isotopes. In the isotopic analysis of enriched “silicon-28” with a high degree of enrichment (> 99.99%), it is necessary to determine the impurities of 29Si and 30Si isotopes at the level of 10-3 ¸ 10-5 at. %. At this concentration level, these isotopes can be considered as impurities. It is difficult to achieve high measurement accuracy with simultaneous registration of the main and “impurity” isotopes in such a wide range of concentrations. The registration of analytical signals of silicon isotopes must be carried out in the solutions with different matrix concentrations. The use of the solutions with the high concentration of the matrix element requires the introduction of corrections for matrix noise and the drift of the instrument sensitivity during the measurement. It is possible to reduce the influence of the irreversible non-spectral interference and sensitivity drift by using the method of internal standardization. The inconsistency of the literature data on the selection criteria for the internal standard required studying the behavior of the signals of the “candidates for the internal standard” for the ELEMENT 2 single-collector high-resolution inductively coupled plasma mass spectrometer on the matrix element concentration and the nature of the solvent, as well as on the solution nebulizing time. Accounting for the irreversible non-spectral matrix noise and instrumental drift in isotopic analysis of enriched “silicon-28” and initial 28SiF4 by inductively coupled plasma mass spectrometry had allowed us to reduce by 3-5 times the random component and by more than an order of magnitude the systematic component of the measurement error in comparison with the external standard method. This made it possible to carry out, with sufficient accuracy, the operational control of the isotopic composition of enriched “silicon-28”, both in the form of silicon tetrafluoride and polycrystalline silicon obtained from it, using a single serial device in the range of isotopic concentrations 0.0001–99.999%.

Tritium Supply and Processing for the First KATRIN Tritium Operation

The main task of the Tritium Laboratory Karlsruhe (TLK) in 2018 was the commissioning and First Tritium (FT) operation of the windowless gaseous tritium source (WGTS) of the Karlsruhe Tritium Neutrino (KATRIN) experiment. It was paramount to enable the FT measurement run of the KATRIN experiment, to yield first scientific results with the complete KATRIN beamline.The aim of KATRIN is to determine the mass of the electron-antineutrino by precise spectroscopy of the tritium β-spectrum close to its maximum energy of 18.6 keV. KATRIN uses an ultraluminous source (WGTS) and a high-resolution electrostatic spectrometer. While the inner loop system of KATRIN has the task of providing stabilized tritium circulation with a throughput of 40 g·day−1 for the WGTS, the outer loop incorporates the entire TLK infrastructure for tritium cleanup, purification, and accountancy prior to reinjection of tritium into the inner loop.For KATRIN’s FT run, ≈5 × 1013 Bq (2.3 × 10−2 mol) of tritium was provided in 3.2 mol of deuterium. In contrast to the high isotopic purity of >95% tritium necessary for future KATRIN operation, a concentration of 7 × 108 Bq·m−3 (resulting in 0.5% nominal source luminosity) had to be kept constant during the entire FT campaign. This required a processing scheme deviating from the later KATRIN outer loop processing procedure.This paper describes the procedures used to supply the KATRIN inner loop with its FT gas. Furthermore, experience gained during operation of the different gas processing steps and tritium accountancy is presented.

Production of 98Tc with high isotopic purity

In this work, technetium-98 (98Tc) was prepared with high isotopic purity via the nuclear reaction 98Mo (p, n) 98Tc for the first time. An enriched 98Mo metal target formed by spark plasma sintering was bombarded with 9.4 MeV protons in a CS-30 cyclotron. A microgram amount of 98Tc with 99.18% isotopic purity was separated from the irradiated target by anion exchange chromatography. Additionally, a chemical procedure for recovering the enriched 98Mo with a 97% recovery rate was developed.

Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light-Emitting Diode.

We have explored alkyl substitution of the ligands as a means to improve the performance of the title complexes in photoredox catalytic systems that produce synthetically useable amounts of hydrated electrons through photon pooling. Despite generating a super-reductant, these electron sources only consume the bioavailable ascorbate and are driven by a green light-emitting diode (LED). The substitutions influence the catalyst activity through the interplay of the quenching parameters, the recombination rate of the reduced catalyst OER and the ascorbyl radical across the micelle-water interface, and the quantum yield of OER photoionization. Laser flash photolysis yields comprehensive information on all these processes and allows quantitative predictions of the activity observed in LED kinetics, but the latter method provides the only access to the catalyst stability under illumination on the timescale of the syntheses. The homoleptic complex with dimethylbipyridine ligands emerges as the optimum that combines an activity twice as high with an undiminished stability in relation to the parent compound. With this complex, we have effected dehalogenations of alkyl and aryl chlorides and fluorides, hydrogenations of carbon-carbon double bonds, and self- as well as cross-coupling reactions. All the substrates employed are impervious to ordinary photoredox catalysts but present no problems to the hydrated electron as a super-reductant. A particularly attractive application is selective deuteration with high isotopic purity, which is achieved simply by using heavy water as the solvent.

A General, Rhodium‐Catalyzed, Synthesis of Deuterated Boranes and N‐Methyl Polyaminoboranes

The rhodium complex [Rh(Ph2 PCH2 CH2 CH2 PPh2 )(η6 -FC6 H5 )][BArF4 ], 2, catalyzes BH/BD exchange between D2 and the boranes H3 B⋅NMe3 , H3 B⋅SMe2 and HBpin, facilitating the expedient isolation of a variety of deuterated analogues in high isotopic purities, and in particular the isotopologues of N-methylamine-borane: R3 B⋅NMeR2 1-dx (R=H, D; x=0, 2, 3 or 5). It also acts to catalyze the dehydropolymerization of 1-dx to give deuterated polyaminoboranes. Mechanistic studies suggest a metal-based polymerization involving an unusual hybrid coordination insertion chain-growth/step-growth mechanism.

Neutron capture cross section of 85Kr

Neutron capture and β− -decay are competing branches of the s-process nucleosynthesis path at 85Kr, which makes it an important branching point. The knowledge of its neutron capture cross section is therefore an essential tool to constrain stellar models of nucleosynthesis. The goal is the measurement of the 85Kr(n,γ) cross section via the time-of- flight method. For this, several methods for the production of 85Kr will be investigated. One of these is the irradiation of a 82Se target with an α-beam. Here, the produced 85Kr stays trapped inside the crystalline structure of the selenium. Due to technical difficulties and low yields, an alternative method is the use of reactor produced 85Kr. For future measurements of the neutron capture cross section of 85Kr at FRANZ (Frankfurter Neutronenquelle am Stern-Gerlach-Zentrum), the goal is the use of a target with a high isotopic purity to reduce the background from 83Kr.

Getting the most neutrinos out of IsoDAR

Several experimental collaborations worldwide intend to test sterile neutrino models by measuring the disappearance of antineutrinos produced via isotope decay at rest (IsoDAR). The most advanced of these proposals have very similar setups, in which a proton beam strikes a target yielding neutrons which are absorbed by a high isotopic purity {}^7hbox {Li} converter, yielding {}^8hbox {Li} whose resulting decay yields the antineutrinos. In this note, we use FLUKA and GEANT4 simulations to investigate three proposed modifications of this standard proposal. In the first, the {}^7hbox {Li} is replaced with {}^7hbox {Li} compounds including a deuterium moderator. In the second, a gap is placed between the target and the converter to reduce the neutron bounce-back. Finally, we consider cooling the converter with liquid nitrogen. We find that these modifications can increase the antineutrino yield by as much as 50%. The first also substantially reduces the quantity of high purity {}^7hbox {Li} which is needed.

The solid state physics programme at ISOLDE: recent developments and perspectives

Solid state physics (SSP) research at ISOLDE has been running since the mid-1970s and accounts for about 10%–15% of the overall physics programme. ISOLDE is the world flagship for the on-line production of exotic radioactive isotopes, with high yields, high elemental selectivity and isotopic purity. Consequently, it hosts a panoply of state-of-the-art nuclear techniques which apply nuclear methods to research on life sciences, material science and bio-chemical physics. The ease of detecting radioactivity—<1 ppm concentrations—is one of the features which distinguishes the use of radioisotopes for materials science research. The manner in which nuclear momenta of excited nuclear states interact with their local electronic and magnetic environment, or how charged emitted particles interact with the crystalline lattices allow the determination of the location, its action and the role of the selected impurity element at the nanoscopic state. ISOLDE offers an unrivalled range of available radioactive elements and this is attracting an increasing user community in the field of nuclear SSP research and brings together a community of materials scientists and specialists in nuclear solid state techniques. This article describes the current status of this programme along with recent illustrative results, predicting a bright future for these unique research methods and collaborations.

Production of germanium stable isotopes single crystals

It is reported on production of germanium stable isotopes 72Ge, 73Ge,74Ge,76Ge single crystals with high isotopic and chemical purity by hydride method. Separation of isotopes was carried out by centrifugal method using monogermane as the initial volatile substance. Samples of monoisotopic monogermanes 72GeH4, 73GeH4,74GeH4, 76GeH4 were purified by the method of low‐temperature rectification. Elementary polycrystalline germanium was extracted by pyrolysis from respective monogermane and purified from impurities by the method of zone melting. Single crystals of germanium isotopes were grown by Czochralski method. The content of the main isotope in the produced single crystals 72Ge, 73Ge,74Ge,76Ge was 99.98; 99.90; 99.93 and 87.5 at. %, respectively, and the content of the impurities of stable elements was less than 10−5 –10−6 mass %.

A non-destructive internal nuclear forensic investigation at Argonne: discovery of a Pu planchet from 1948

A plutonium alpha standard dating from 1948 was discovered at Argonne National Laboratory and characterized using a number of non-destructive analytical techniques. The principle radioactive isotope was found to be 239Pu and unique ring structures were found across the surface of the deposition area. Due to chronological constraints on possible sources and its high isotopic purity, the plutonium in the sample was likely produced by the Oak Ridge National Lab X-10 Reactor. It is proposed that the rings are resultant through a combination of polishing and electrodeposition, though the hypothesis fails to address a few key features of the ring structures.

Epitaxially Grown Monoisotopic Si, Ge, and Si1–x Ge x Alloy Layers: Production and Some Properties

The technology of the growth of Si, Ge, and Si1–xGex layers by molecular-beam epitaxy with the use of a sublimation source of monoisotopic 30Si or 28Si and/or gas sources of monogermane 74GeH4 is demonstrated. All of the epitaxial layers are of high crystal quality. The secondary-ion mass spectroscopy data and Raman data suggest the high isotopic purity and structural perfection of the 30Si, 28Si, 74Ge, and 30Si1–x74Gex layers. The 30Si layers doped with Er exhibit an efficient photoluminescence signal.

Monogermanes 74GeH4 and 73GeH4 of high isotopic and chemical purity

Monogermanes 74GeH4 and 73GeH4 of high isotopic and chemical purity

ChemInform Abstract: Monoisotopic Varieties of Silicon and Germanium with a High Chemical and Isotopic Purity

AbstractReview: 25 refs.

The production of radionuclides for nuclear medicine from a compact, low-energy accelerator system

IntroductionThe field of nuclear medicine is reliant on radionuclides for medical imaging procedures and radioimmunotherapy (RIT). The recent shut-downs of key radionuclide producers have highlighted the fragility of the current radionuclide supply network, however. To ensure that nuclear medicine can continue to grow, adding new diagnostic and therapy options to healthcare, novel and reliable production methods are required. Siemens are developing a low-energy, high-current – up to 10MeV and 1mA respectively – accelerator. The capability of this low-cost, compact system for radionuclide production, for use in nuclear medicine procedures, has been considered. MethodologyThe production of three medically important radionuclides – 89Zr, 64Cu, and 103Pd – has been considered, via the 89Y(p,n), 64Ni(p,n) and 103Rh(p,n) reactions, respectively. Theoretical cross-sections were generated using TALYS and compared to experimental data available from EXFOR. Stopping power values generated by SRIM have been used, with the TALYS-generated excitation functions, to calculate potential yields and isotopic purity in different irradiation regimes. ResultsThe TALYS excitation functions were found to have a good agreement with the experimental data available from the EXFOR database. It was found that both 89Zr and 64Cu could be produced with high isotopic purity (over 99%), with activity yields suitable for medical diagnostics and therapy, at a proton energy of 10MeV. At 10MeV, the irradiation of 103Rh produced appreciable quantities of 102Pd, reducing the isotopic purity. A reduction in beam energy to 9.5MeV increased the radioisotopic purity to 99% with only a small reduction in activity yield. ConclusionThis work demonstrates that the low-energy, compact accelerator system under development by Siemens would be capable of providing sufficient quantities of 89Zr, 64Cu, and 103Pd for use in medical diagnostics and therapy. It is suggested that the system could be used to produce many other isotopes currently useful to nuclear medicine.