7Li Ions Research Articles

Nucleon and delute cluster transfer in the reactions 6Li + 9Be

The results of experiments on studying nucleon and cluster transfer processes in the reactions of the 6Li (68 MeV) ions with the 9Be target nuclei are presented. The angular distributions for the reaction channels 9Be(6Li,α)11Bg.s and 9Be(6Li,10B)5Heg.s. have been measured. To describe the possible contributions of sequential transfer of nucleons and alpha clusters, as well as direct transfer of the 5Не cluster, the DWBA method (FRESCO) is used, the spectroscopic amplitudes are obtained for the configurations of (9Be+d) and (6Li+5He) in the 11B nucleus and (6Li+α) in the 10B nucleus. The results of the theoretical analysis agree with the experimental data and indicate a strong correlation between a neutron and an α-cluster, leading to the formation of the 5Не cluster in the transfer processes.

Monte Carlo-Based Radiobiological Investigation of the Most Optimal Ion Beam Forming SOBP for Particle Therapy.

Proton (p) and carbon (C) ion beams are in clinical use for cancer treatment, although other particles such as He, Be, and B ions have more recently gained attention. Identification of the most optimal ion beam for radiotherapy is a challenging task involving, among others, radiobiological characterization of a beam, which is depth-, energy-, and cell type- dependent. This study uses the FLUKA and MCDS Monte Carlo codes in order to estimate the relative biological effectiveness (RBE) for several ions of potential clinical interest such as p, 4He, 7Li, 10Be, 10B, and 12C forming a spread-out Bragg peak (SOBP). More specifically, an energy spectrum of the projectiles corresponding to a 5-cm SOBP at a depth of 8 cm was used. All secondary particles produced by the projectiles were considered and RBE was determined based on radiation-induced Double Strand Breaks (DSBs), as calculated by MCDS. In an attempt to identify the most optimal ion beam, using the latter data, biological optimization was performed and the obtained depth-dose distributions were inter-compared. The results showed that 12C ions are more effective inside the SOBP region, which comes at the expense of higher dose values at the tail (i.e., after the SOBP). In contrast, p beams exhibit a higher DSOPB/DEntrance ratio, if physical doses are considered. By performing a biological optimization in order to obtain a homogeneous biological dose (i.e., dose × RBE) in the SOBP, the corresponding advantages of p and 12C ions are moderated. 7Li ions conveniently combine a considerably lower dose tail and a DSOPB/DEntrance ratio similar to 12C. This work contributes towards identification of the most optimal ion beam for cancer therapy. The overall results of this work suggest that 7Li ions are of potential interest, although more studies are needed to demonstrate the relevant advantages. Future work will focus on studying more complex beam configurations.

Evidence of fast neutron detection capability of the CLLB scintillation detector

For the first time we report the ability of the CLLB scintillator to detect and discriminate fast neutrons (2–10 MeV energy range) from gamma-rays and thermal neutrons, using a digital pulse shape discrimination technique. Firstly, we conducted measurements in single mode with an Am–Be source, unshielded and shielded, and we tagged a new cluster of events as the fast neutron-induced zone. The Figure of Merit obtained for the fast neutron/gamma discrimination was 1.1. Then, in order to better characterize these new cluster of events induced by fast neutrons, we conducted measurements in coincidence mode. We used a mono-energetic pulsed neutron source, at the Van de Graaff accelerator facility at the Legnaro National Laboratories (INFN-LNL, Legnaro-Italy), and also, a continuous neutron spectrum (using a 252Cf source). Combining all experimental results with a Monte Carlo model of the CLLB detector, built using the GEANT4 tool kit, it was possible to obtain the light output function of 7Li ions in the CLLB crystal (dL/dE = κ; κ = 0.36 ± 0.02). Moreover, the intrinsic fast neutron efficiency was modeled by Monte Carlo, obtaining similar values 1.5%–2% for neutrons between 2 MeV and 10 MeV. Finally, an application of this new feature, in the field of nuclear security and nuclear safeguards, is given.

SANTA: A safety analysis code for neutron absorbers in spent nuclear fuel pools

Recent experimental reports on the premature corrosion of an Al-B4C neutron absorber in a spent nuclear fuel pool, which was possibly assisted by 10B(n, α)7Li reaction-induced porous microstructures, illustrated the need for quantitative evaluation of the neutron-induced energetic particle emission reactions inside neutron absorbers. For this purpose, we developed a Safety Analysis code for NeuTron Absorbers in spent nuclear fuel pools (SANTA) by integrating several existing codes (TRITON, ORIGEN, CSAS6, and modified SDTrimSP) with newly developed modules to provide the essential parameters for the experimental emulation of irradiation-assisted corrosion of the absorbers. The most important outputs of this code are radiation damage in displacement per atom (dpa) units and He concentration in atomic ppm. These outputs are required for the design of heavy-ion irradiation experiments on the absorbers to emulate the radiation damage induced by energetic 7Li ions and α-particles. The SANTA code is also user-friendly: its whole sequence can be executed using simplified text-based input without user intervention. This code may improve the understanding of the gas bubble formation and irradiation-assisted corrosion mechanisms of the neutron absorbers, and it could provide a foundation for the future development of more robust safety codes for spent nuclear fuel pools.

Physiological and Differential Proteomic Analysis at Seedling Stage by Induction of Heavy-Ion Beam Radiation in Wheat Seeds.

Novel genetic variations can be obtained by inducing mutations in the plant which help to achieve novel traits. The useful mutant can be obtained through radiation mutation in a short period which can be used as a new material to produce new varieties with high yield and good quality wheat. In this paper, the proteomic analysis of wheat treated with different doses of 12C and 7Li ion beam radiation at the seedling stage was carried out through a Tandem Mass Tag (TMT) tagging quantitative proteomic analysis platform based on high-resolution liquid chromatography-mass spectrometry, and the traditional 60Co-γ-ray radiation treatment for reference. A total of 4,764 up-regulated and 5,542 down-regulated differentially expressed proteins were identified. These proteins were mainly enriched in the KEGG pathway associated with amino acid metabolism, fatty acid metabolism, carbon metabolism, photosynthesis, signal transduction, protein synthesis, and DNA replication. Functional analysis of the differentially expressed proteins showed that the oxidative defense system in the plant defense system was fully involved in the defense response after 12C ion beam and 7Li ion beam radiation treatments. Photosynthesis and photorespiration were inhibited after 12C ion beam and 60Co-γ-ray irradiation treatments, while there was no effect on the plant with 7Li ion beam treatment. In addition, the synthesis of biomolecules such as proteins, as well as multiple signal transduction pathways also respond to radiations. Some selected differentially expressed proteins were verified by Parallel Reaction Monitoring (PRM) and qPCR, and the experimental results were consistent with the quantitative results of TMT. The present study shows that the physiological effect of 12C ion beam radiation treatment is different as compared to the 7Li ion beam, but its similar to the 60Co-γ ray depicting a significant effect on the plant by using the same dose. The results of this study will provide a theoretical basis for the application of 12C and 7Li ion beam radiation in the mutation breeding of wheat and other major crops and promote the development of heavy ion beam radiation mutation breeding technology.

Break-up effect of the weakly bound 6Li nuclei scattered by 208Pb target

Using different potentials based on phenomenological, semi microscopic, and microscopic models, we investigated the reaction dynamics induced by the weakly bound 6Li ions on a heavy mass target 208Pb at sixteen energy sets ranging from 25 MeV to 210 MeV. The 6Li cluster nature and its dissociation into a core (α-particle) and a valence particle (deuteron) orbiting this core was taken into consideration using the cluster folding model (CFM). The new version of Sao Paulo potential (SPP2) is also used to investigate 6Li+208Pb data. In order to reproduce the experimental data, the strength of real part of potential created using SPP and CFM should be reduced by ~ 49 % and 62 %, respectively. The data could be well reproduced using non-renormalized real cluster folding potential, if an additional dynamical polarization potential (DPP) of repulsive real surface form is introduced. The observed reduction in the strength of the real double folded and cluster folding potentials is due to the break-up effect of 6Li.

Nuclear-optical converters for detecting intense neutron

In the design of nuclear-optical converters (NOC) for detecting intense neutron fields (fluxes over 1015 cm–2·s–1), it is proposed to use hybrid gas ionization chambers (IC), in which electrical and optical neutron detecting methods are combined. For hybrid ICs, a technology is proposed for obtaining radiation-resistant and mechanically strong radiator materials capable of operating at temperatures of up to 1000 °C. This technology is based on solid-phase boron diffusion saturation of steel. It is shown that, at thermal neutron fluxes of 1×1010 n/(cm2·s) and higher, the integral intensity of argon luminescence as a result of ionization by α-particles and 7Li ions from layers of boride phases is sufficient for detection. The combination of optical and radiation properties of multicomponent fluoride glasses makes it possible to use them as condensed active substances of NOCs. Choosing the elemental and isotopic composition, it becomes possible to use fluoride glasses for multichannel neutron detection as well as to significantly simplify the procedure for separating gamma and neutron components of radiation under conditions of intense radiation fluxes. It has been experimentally shown that in irradiation with a neutron flux of 1×1017 n/(cm2·s), the intensity of Nd IR luminescence in glasses based on zirconium fluoride (ZBLAN) increases in the presence of Gd, which interacts with neutrons.

Improving position resolution of neutron detectors with ultra-thin B4C foils

A new technique for detection of slow neutrons with gaseous detectors using ultra-thin layers with 10B atoms is presented. The reaction between a thermal neutron and a 10B atom releases two secondary particles, namely a 7Li ion and an alpha particle, which due to momentum conservation are emitted in opposite directions, along the same line (back to back). Current boron coated neutron detectors are equipped with 10B films with thicknesses of several micrometers, deposited on very thick substrate plates. However, since the ranges of the 7Li ion and the alpha particle are of few micrometeres in most materials, one of these particles is always lost in the 10B layer or substrate. As such, these detectors lose the ability to reconstruct the reaction line of action and to precisely determine the neutron position, as only one of the two secondary particles tracks can be measured. With the technique now presented, the sum of the 10B layer and the substrate thicknesses is small enough to allow for both secondary particles to escape and ionize the gas in opposite sides of the 10B converter foil. Independent readout structures, one on each side of the 10B converter foil, detect each secondary particle and determine its track centroid and the deposited energy. Since the two secondary particles are emitted back to back, the neutron position can be obtained by combining the information recorded by the two readout structures. Through GEANT4 simulations, we verified that the spatial resolution can be significantly improved: our results show that, by using a B4C layer with a thickness of 1 μm on a 0.9 μm Mylar substrate, the spatial resolution can by improved by a factor of eight, compared to conventional detectors with thick 10B detection layers.

Anomaly in weakly bound 7Li nucleus in the field of 208Pb target

We have investigated the threshold anomaly observed in 7Li + [Formula: see text]Pb nuclear system by analyzing the available 7Li+[Formula: see text]Pb experimental angular distribution measurements. The experimental data for the weakly bound 7Li ions elastically scattered from [Formula: see text]Pb target at 13 energy sets ranging from 25.67 and up to 68[Formula: see text]MeV are subjected to detailed analysis using different interaction potentials created either based on phenomenological, semimicroscopic and microscopic models. The loosely bound nucleus 7Li, possessing a predominant [Formula: see text] cluster structure at 2.468[Formula: see text]MeV, is a good candidate as its break-up reaction studies would help to understand the break-up of the weakly bound unstable radioactive isotopes. In order to observe the break-up effect, reaction cross-sections are extracted and compared with the previously reported ones.

A parallel-plate RF probe and battery cartridge for 7Li ion battery studies

A new parallel-plate resonator for 7Li ion cell studies is introduced along with a removable cartridge-like electrochemical cell for lithium ion battery studies. This geometry separates the RF probe from the electrochemical cell permitting charge/discharge of the cell outside the magnet and introduces the possibility of multiplexing samples under test. The new cell has a geometry that is similar to that of a real battery, unlike the majority of cells employed for MR/MRI studies to this point. The cell, with electrodes parallel to the B1 magnetic field of the probe, avoids RF attenuation during excitation/reception. The cell and RF probe dramatically increase the sample volume compared to traditional MR compatible battery designs. Ex situ and in situ 1D 7Li profiles of Li ions in the electrolyte solution of a cartridge-like cell were acquired, with a nominal resolution of 35 µm at 38 MHz. The cell and RF probe may be employed for spectroscopy, imaging and relaxation studies. We also report the results of a T1-T2 relaxation correlation experiment on both a pristine and fully charged cell. This study represents the first T1-T2 relaxation correlation experiment performed in a Li ion cell. The T1-T2 correlation maps suggest lithium intercalated into graphite is detected by this methodology in addition to other Li species.

Separation of astatine from irradiated lead targets based on dry distillation in a glass test tube

Astatine was separated from a lead target, irradiated with 7Li ion beams, by dry distillation. Dry distillation was conducted in a glass test tube filled with nitrogen gas by heating the test tube with an electric furnace at 650 °C. The optimized conditions of the dry distillation procedure were studied by monitoring astatine radioactivity with gamma-ray spectrometers. The separation of astatine was accomplished in ~ 10 min. The cooling of the middle portion of the test tube was instrumental in recovering astatine radioactivity in high yields. The adsorption temperature of astatine on the glass surface was ~ 20 °C.

Effective charge parameter for 7Li, 12C and 16O ions in aluminum, silver, gold, polypropylene and polycarbonate foils

The effective charge parameter of 7Li, 12C and 16O ions have been calculated in aluminum, silver, gold, polypropylene and polycarbonate foils by using the experimental data of stopping power compiled by the Nuclear Data Section of International Atomic Energy Agency (IAEA). These measured values have been compared with those calculate based on theoretical formulation of Brandt-Kitagawa modified by Ziegler, Biersack and Littmark (BK-ZBL), Anthony-Lanford expression and CasP 5.2 code values in the energy range 0.4 MeV/n to 5.25 MeV/n for 7Li, to 6.25MeV/n for 12C and to 9.44MeV/n for16O. We have obtained a global fit equation, which reproduced well the experimental data of effective charge parameter.

Dose assessment with MCNP5/X code for boron neutron capture therapy of pancreas cancer

Boron neutron capture therapy is based on neutron capture by 10B and creation of high energy alpha particle and recoiled 7Li ion which have ranges comparable to cell dimensions. The MCNP5/X code is applied for calculation of the absorbed doses as well as dose distribution by depth in pancreas cancer and the organs of the analytical and voxelized Oak Ridge National Laboratory phantom, which represents the human body. The depth dose distributions for thermal, epithermal neutrons, and neutron spectrum, show that the absorbed doses are the largest exactly in the cancer, in all cases. It is found by this simulation that the epithermal neutrons are the optimal choice for BNC therapy. They deliver a similar dose to cancer as the thermal neutrons but, spare the healthy tissue more than the thermal ones.

Numerical investigation of a new ICRF heating scenario in D-T plasma on CFETR

For a fusion device, plasma pre-heating is required before the self-sustaining burning-state reactions of deuterium (D) and tritium (T) commence. Plasma heating with waves in the ion-cyclotron range of frequencies (ICRF) is effective in tokamaks. A new three-ion ICRF heating scheme for plasmas in the Chinese Fusion Engineering Test Reactor (CFETR) that require an increase in the bulk ion temperature via heating the lithium impurities in the D–T plasmas, was studied numerically. Our simulations show that the radio-frequency wave power is strongly absorbed by very few 7Li ions with concentrations of 0.01%–0.2% in a suitable mixture of D–T plasmas, the enhanced minority ion heating is related to that the 7Li fundamental resonance layer is very close to the two mode conversion layers. In adjusting the mixtures over a wide range of composition, an oscillatory behaviour in the 7Li absorption efficiency arises because of interference. Moreover, from estimates of the 7Li ion tail energy, most of the tail energy of the minority ions is found to be transferred to background ions via collisions. Compared with the routine (3He)-D–T scheme, the ICRF power is absorbed more effectively by the 7Li ions in the (7Li)-D–T heating scenario, and after the Fokker–Planck equations were solved, a large fraction of bulk ion heating was evident in the (7Li)-D–T heating scenario. The new three-ion scenario may therefore be an attractive proposition for bulk ion heating during the activated phase of the reactor.

Simultaneous Determination of the Magnetic Moments of 6Li and 7Li Nuclei Using an NMR Spectrometer

The ratio of NMR frequencies of lithium isotopes f(7Li)/f(6Li) = 2.6409061846(13) was determined with an error of 4.9·10–10. The use of a nuclear magnetic resonance spectrometer operating in the mode of simultaneous registration of signals from two nuclei to obtain data allowed the random and systematic errors in the measurement results to be reduced by an order of magnitude. The ratio of the resonant frequencies of water protons and 7Li ions was determined: f(H2O)/f(7Li) = 2.557100473(9) with an error of 3.5·10–9 for solutions with an extremely low concentration of LiOH*H2O salt in water and at a temperature of 25°C. Based on the obtained data, the magnetic moments of lithium nuclei were calculated: μ(6Li) = 0.8220454(25)μN, μ(7Li) = 3.2564171(98)μN. The known data on the magnetic moment of the proton and data on the electronic shielding of these nuclei were used. A comparison of the experimental data for μ(6Li) and μ(7Li) and the corresponding theoretical calculation data was performed.

Determination of the magnetic moments of 6Li and 7Li nuclei using an NMR spectrometer that records signals from two nuclei simultaneously

The ratio of NMR frequencies of lithium isotopes was determined: with an error of 4,9·10–10. We used a spectrometer mode with simultaneous recording of signals from two cores, which allows us to reduce random and systematic errors by an order of magnitude. The ratio of the resonant frequencies of water protons and 7Li ions was determined: with an error of 3,5·10–9 for solutions with an extremely low concentration of LiOH*H2O salt in water and at a temperature of 25 °C. Based on the data obtained, the magnetic moments of lithium nuclei were calculated. The known data on the magnetic moment of the proton and data on the electronic shielding of these nuclei were used. The comparison of experimental data on µ(6Li) and µ(7Li) with data from theoretical calculations is discussed.

Biological effects of 7lithium (7Li) ion beam radiation on mutation induction in Capsicum annuum L.

Biological effects of 7lithium (7Li) ion beam radiation on mutation induction in Capsicum annuum L.

Monte Carlo radiation transport modelling of the current-biased kinetic inductance detector

Radiation transport simulations were used to analyse neutron imaging with the current-biased kinetic inductance detector (CB-KID). The PHITS Monte Carlo code was applied for simulating neutron, 4He, 7Li, photon and electron transport, 10B(n, α)7Li reactions, and energy deposition by particles within CB-KID. Slight blurring in simulated CB-KID images originated from 4He and 7Li ions spreading out in random directions from the 10B conversion layer in the detector prior to causing signals in the X and Y superconducting Nb nanowire meander lines. 478 keV prompt gamma rays emitted by 7Li nuclei from neutron-10B reactions had negligible contribution to the simulated CB-KID images. Simulated neutron images of 10B dot arrays indicate that sub 10μm resolution imaging should be feasible with the current CB-KID design. The effect of the geometrical structure of CB-KID on the intrinsic detection efficiency was calculated from the simulations. An analytical equation was then developed to approximate this contribution to the detection efficiency. Detection efficiencies calculated in this study are upper bounds for the reality as the effects of detector temperature, the bias current, signal processing and dead-time losses were not taken into account. The modelling strategies employed in this study could be used to evaluate modifications to the CB-KID design prior to actual fabrication and testing, conveying a time and cost saving.

Production of Intense Beams of Lithium, Magnesium, Phosphorus, and Calcium Ions by the ECR Ion Source at the DC-60 Cyclotron

The results of experiments on the production of intense beams of heavy lithium, magnesium, phosphorus, and calcium ions with a microevaporator are reported. The first beams of 7Li, 24Mg, 31P, and 40Ca ions were produced in these experiments conducted in 2017–2018 at the DC-60 cyclotron. The modes of acceleration of these ions to an energy of 1.75 Mev/nucleon were also optimized.

Numerical investigation for lithium isotope effect in ionic superconductor

The lithium isotope effect in ionic superconductors is numerically investigated. Using first-principles and kinetic Monte–Carlo simulations, the diffusion coefficients of 6Li and 7Li ions are calculated. Two important effects that cause the difference in the mobilities of lithium isotopes are also shown: the quantum effect, which decreases the activation barrier energy for lithium ion in a certain structure and increases the ratio of the diffusion coefficient of Li isotopes, as well as the correlation effect between 6Li and 7Li ions and vacancies. These results will assist in finding materials that exhibit large lithium isotope effect. The preferred chemical composition of lithium isotopes required to enhance the lithium isotope effect and the application of these isotopes as a separation membrane for the lithium ionic superconductors are discussed.