Alpha-particle Bombardment Research Articles

Behaviour, use and safety aspects of astatine-211 solvated in chloroform after dry distillation recovery

Targeted alpha therapy of disseminated cancer is an emerging technique where astatine-211 is one of the most promising candidate nuclides. Astatine-211 can be produced in medium energy cyclotrons by alpha particle bombardment of natural bismuth. The produced astatine is then commonly recovered from the irradiated solid target material through dry distillation. The dry distillation process often includes elution and solvation of condensed astatine with chloroform, forming Chloroform Eluate. In this work the handling and safe use of the high activity concentration Chloroform Eluate has been investigated. Correctly performed, evaporation of Chloroform Eluate results in a dry residue with complete recovery of the astatine. The dry residue can then serve as a versatile starting material, using appropriate oxidizing or reducing conditions, for subsequent downstream chemistry. However, it has been found that when evaporating the Chloroform Eluate, astatine can be volatilized if continuing the process beyond the point of dryness. This behavior is more pronounced when the Chloroform Eluate has received a higher absorbed dose. Upon water phase contact of the Chloroform Eluate, a major part of the astatine activity becomes water soluble, leaving the organic phase. A behavior which is also dependent on dose to the solvent.

Stability of Al and Ag metallic thin film mirrors in a space environment under the implantation of low energy helium ions

The stability of aluminum (Al) and silver (Ag) metallic thin films (MTFs) under helium ion bombardment has been investigated in the laboratory to replicate the effect of alpha particle bombardment on spacecrafts and satellites in a space environment. The implanted helium ions have varying fluence and energies ranging from 0.5 - 3 keV. The helium ion fluence in the present study has been chosen according to 4 and 6 years journey of a solar orbiter. The reflectivity of Al and Ag MTFs is investigated over a wide range of electromagnetic radiation covering ultraviolet to near infrared (200 - 2500 nm), prior and post helium ion implantation. It is observed that the degradation in the reflectivity of the above-mentioned MTFs is reasonably low for helium ion implantation and no significant impact is observed on reflectivity of both (Al and Ag) MTFs in the investigation. This opens a channel of utilization of these MTFs to provide better protection for the optical components used in spacecrafts. Surface characterization such as surface roughness is carried out to investigate the surface morphology of MTFs prior and post implantation using atomic force microscopy (AFM). It is observed that the effect of implantation on surface morphology is in accordance with the experimental results of reflectivity. SRIM/TRIM simulations help to obtain the distribution profile and penetration depth of helium ions inside the Al and Ag MTFs.

The Crystallinity of Apatite in Contact with Metamict Pyrochlore from the Silver Crater Mine, ON, Canada

The purpose of this work is to evaluate the long-term effects of radiation on the structure of naturally occurring apatite in the hope of assessing its potential for use as a solid nuclear waste form for actinide sequestration over geologically relevant timescales. When a crystal is exposed to radioactivity from unstable constituent atoms undergoing decay, the crystal’s structure may become damaged. Crystalline materials rendered partially or wholly amorphous in this way are deemed “partially metamict” or “metamict” respectively. Intimate proximity of a non-radioactive mineral to a radioactive one may also cause damage in the former, evident, for example, in pleochroic haloes surrounding zircon inclusions in micas. Radiation damage may be repaired through the process of annealing. Experimental evidence suggests that apatite may anneal during alpha particle bombardment (termed “self-annealing”), which, combined with a low solubility in aqueous fluids and propensity to incorporate actinide elements, makes this mineral a promising phase for nuclear waste storage. Apatite evaluated in this study occurs in a Grenville-aged crustal carbonatite at the Silver Crater Mine in direct contact with U-bearing pyrochlore (var. betafite)—a highly radioactive mineral. Stable isotope analyses of calcite from the carbonatite yield δ18O and δ13C consistent with other similar deposits in the Grenville Province. Although apatite and betafite imaged using cathodoluminescence (CL) show textures indicative of fracture-controlled alteration, Pb isotope analyses of betafite from the Silver Crater Mine reported in previous work are consistent with a model of long term Pb loss from diffusion, suggesting the alteration was not recent. Thus, it is interpreted that these minerals remained juxtaposed with no further metamorphic overprint for ≈1.0 Ga, and therefore provide an ideal opportunity to study the effects of natural, actinide-sourced radiation on the apatite structure over long timescales. Through broad and focused X-ray beam analyses and electron backscatter diffraction (EBSD) mapping, the pyrochlore is shown to be completely metamict—exhibiting no discernible diffraction associated with crystallinity. Meanwhile, apatite evaluated with these methods is confirmed to be highly crystalline with no detectable radiation damage. However, the depth of α-decay damage is not well-understood, with reported depths ranging from tens of microns to just a few nanometers. EBSD, a surface sensitive technique, was therefore used to evaluate the crystallinity of apatite surfaces which had been in direct contact with radioactive pyrochlore, and the entire volume of small apatite crystals whose cores may have received significant radiation doses. The EBSD results demonstrate that apatite remains crystalline, as derived from sharp and correctly-indexed Kikuchi patterns, even on surfaces in direct contact with a highly radioactive source for prolonged periods in natural systems.

Mechanical behavior of copper containing a gas-bubble superlattice

Helium implantation can cause the formation of a helium gas-bubble superlattice in crystalline materials. Experimental studies of the mechanical response of a material hosting such a superlattice are lacking, especially at the microstructural level. By employing a novel, high-throughput, high-precision nanoscale helium implantation technique, in combination with in-situ transmission electron microscopy nanomechanical testing, we find that the helium-bubble superlattice structure in copper is disordered or maintained depending on whether the material's plasticity occurs by multiple ordinary full dislocations or by deformation twinning. In addition, helium implantation can harden the material significantly: the higher the dose, the larger the yield stress. The measured hardening behavior agrees well with the trend predicted by the Friedel-Kroupa-Hirsch model. Our findings shed new light on understanding the mechanical and microstructural properties of materials subjected to intense helium generation by neutron and alpha-particle bombardment in nuclear fusion, fission or spallation systems.

Radiation damage from long-term alpha particle bombardment of silicates – a microfocus XRD and Fe K-edge XANES study

AbstractA detailed understanding of the response of mineral phases to the radiation fields experienced in a geological disposal facility (GDF) is currently poorly constrained. Prolongued ion irradiation has the potential to affect both the physical integrity and oxidation state of materials and therefore may alter a structure's ability to react with radionuclides. Radiohalos (spheres of radiation damage in minerals surrounding radioactive (α-emitting) inclusions) provide useful analogues for studying long term α-particle damage accumulation. In this study, silicate minerals adjacent to Th- and U-rich monazite and zircon were probed for redox changes and long/short range disorder using microfocus X-ray absorption spectroscopy (XAS) and high resolution X-ray diffraction (XRD) at Beamline I18, Diamond Light Source. Fe3+ → Fe2+ reduction has been demonstrated in an amphibole sample containing structural OH– groups – a trend not observed in anhydrous phases such as garnet. Coincident with the findings of Pattrick et al. (2013), the radiolytic breakdown of OH– groups is postulated to liberate Fe3+ reducing electrons. Across all samples, high point defect densities and minor lattice aberrations are apparent adjacent to the radioactive inclusion, demonstrated by micro-XRD.

Neutron Interferometry: Lessons in Experimental Quantum Mechanics, Wave–Particle Duality, and Entanglement. 2nd Ed. By Helmut Rauch and Samuel A. Werner. Oxford University Press, 2015. Price (hardcover) GBP 70. ISBN 978-0-19-871251-0.

There is a story, perhaps apocryphal, that Nobel Laureate physicist I. I. Rabi, upon learning of the discovery of the muon in 1936, exclaimed ‘Who ordered that!’ His surprise came from the belief that, with the discovery of the neutron by James Chadwick just four years earlier, physicists ’ model of the sub-atomic world was satisfactorily complete. At the time of its discovery in 1932, the neutron was precisely what physicists would have ordered to resolve a variety of troubling observations. It accounted for the existence of isotopes, for the neutral non-electromagnetic radiation that emerged from alpha particle bombardment of certain elements like beryllium or boron, for the apparent emergence of electrons from inside a nucleus that underwent beta decay, and for the puzzling fact that nitrogen-14 was a boson when, according to a proton–electron model, it should have been a fermion. However satisfied Chadwick may have been to find that the neutron resolved a host of problems physicists faced in the 1930s, were he alive now I suspect he would be rendered speechless in amazement by Rauch and Werner’s comprehensive and lucid book of the very many ways neutrons have been employed since then to test physical principles and to study the properties of condensed matter. At the core of this versatility is the fact that the neutron participates in all the known fundamental interactions: the strong nuclear interaction (it helps maintain the integrity of a nucleus against the mutual electrostatic repulsion of protons), the weak nuclear interaction (it is itself unstable against beta decay with a free-state half-life of about 10 min), gravity (it not only falls in a gravitational field but responds to a gravitational potential under conditions where there is no classical gravitational force) and electromagnetism (although it is neutral, it has a magnetic moment and therefore can respond to magnetic fields as well as to laboratory electric fields that, by virtue of special relativity, transform to magnetic fields in the neutron’s rest frame). Neutron Interferometry examines the manifold consequences of these interactions through detailed explanations of experiments, executed for the most part within the authors’ own research groups, employing the extraordinarily sensitive perfect silicon crystal neutron interferometer. Although a wide variety of experiments are described in the book, the typical experimental configuration is that of a Mach–Zehnder interferometer of monolithic design, the various reflecting plates of which were cut from a single Si crystal which forms the base. The essential feature of the apparatus, as highlighted by the authors, is that the reflecting planes are arranged undisturbed throughout the entire macroscopic apparatus (enclosed areas up to about 100 cm have been tested) with a precision comparable to the lattice spacing. Although a prospective reader may infer from the book title that the subject is limited to interferometry, one discovers immediately from perusing the contents that, from the perspective of modern physics, this is hardly a limitation at all. Interferometry, whether optical, electron or neutron, has played a key role in elucidating many of the most fundamental physical problems of the 20th century, and I expect that to continue throughout the 21st. Among the numerous issues upon which neutron interferometry has been brought to bear, as discussed by Rauch and Werner, are key questions relating to ISSN 1600-5767

Separation of no-carrier-added 111In and 109Cd from α-particle induced Ag target using glass wool surface

Alpha particle bombardment on thick silver target produced no-carrier-added (NCA) 111In and 109Cd radioisotopes in the matrix. NCA 111In and 109Cd were separated from the target matrix by solid–liquid extraction using glass wool surface. At 10−2 M HNO3 concentration, ~100 % 111In and 93 % 109Cd were adsorbed on the glass wool surface along with 16 % contamination of bulk Ag. After quantitative removal of bulk Ag from glass wool surface by de-ionized water, 111In and 109Cd were desorbed by 0.1 M HNO3. The mutual separation between 111In and 109Cd was achieved by column chromatography using Dowex 50WX-50 resin.

TCAD simulation for alpha-particle spectroscopy using SIC Schottky diode.

There is a growing requirement of alpha spectroscopy in the fields context of environmental radioactive contamination, nuclear waste management, site decommissioning and decontamination. Although silicon-based alpha-particle detection technology is mature, high leakage current, low displacement threshold and radiation hardness limits the operation of the detector in harsh environments. Silicon carbide (SiC) is considered to be excellent material for radiation detection application due to its high band gap, high displacement threshold and high thermal conductivity. In this report, an alpha-particle-induced electron-hole pair generation model for a reverse-biased n-type SiC Schottky diode has been proposed and verified using technology computer aided design (TCAD) simulations. First, the forward-biased I-V characteristics were studied to determine the diode ideality factor and compared with published experimental data. The ideality factor was found to be in the range of 1.4-1.7 for a corresponding temperature range of 300-500 K. Next, the energy-dependent, alpha-particle-induced EHP generation model parameters were optimised using transport of ions in matter (TRIM) simulation. Finally, the transient pulses generated due to alpha-particle bombardment were analysed for (1) different diode temperatures (300-500 K), (2) different incident alpha-particle energies (1-5 MeV), (3) different reverse bias voltages of the 4H-SiC-based Schottky diode (-50 to -250 V) and (4) different angles of incidence of the alpha particle (0°-70°).The above model can be extended to other (wide band-gap semiconductor) device technologies useful for radiation-sensing application.

Distribution of footprint marked by energetic alpha particle bombardment on the first wall

Abstract Full orbit-following calculations for the final orbit of lost alpha particles in an ITER equilibrium are performed using a Lorentz orbit code LORBIT [M. Isobe, et al. Rev. Sci. Instrum. 70 (1999) 827] to obtain parameter dependence of the footprint of alpha particle bombardment on the first wall. Determination of the poloidal location for the footprint is dominated by the pitch angle at the starting point. Toroidal distribution of the footprint location is inhomogeneous even for equipartitioned starting points because of the shadow of the magnetic field line on the first wall surface. Due to a hopping motion of an alpha particle on the surface of the first wall, a lined footprint is generated. Energy deposition is found to be dispersed along the line.

The Discovery of Artificial Radioactivity

We reconstruct Frederic Joliot and Irene Curie’s discovery of artificial radioactivity in January 1934 based in part on documents preserved in the Joliot–Curie Archives in Paris, France. We argue that their discovery followed from the convergence of two parallel lines of research, on the neutron and on the positron, that were focused on a well-defined experimental problem, the nuclear transmutation of aluminum and other light elements. We suggest that a key role was played by a suggestion that Francis Perrin made at the seventh Solvay Conference at the end of October 1933, that the alpha-particle bombardment of aluminum produces an intermediate unstable isotope of phosphorus, which then decays by positron emission. We also suggest that a further idea that Perrin published in December 1933, and the pioneering theory of beta decay that Enrico Fermi also first published in December 1933, established a new theoretical framework that stimulated Joliot to resume the researches that he and Curie had interrupted after the Solvay Conference, now for the first time using a Geiger-Muller counter to detect the positrons emitted when he bombarded aluminum with polonium alpha particles.

Light-ion-irradiation-induced thermal spikes in nanoporous silica

Improving mechanical properties of low-density nanoporous solids has been a long standing challenge. Here, we study how alpha particle bombardment and thermal annealing can be used to improve mechanical properties of nanoporous silica aerogels analysed by depth-sensing nanoindentation. Data suggest that light-ion irradiation creates non-melting thermal spikes in unconstrained nanoligaments of the aerogel, resulting in improved ligament connectivity.

Surface electrical degradation due to ion bombardment of ITER insulators

Insulators will be used in ITER diagnostic systems where they will play an important role for optical components, as well as in neutral beam injector system. In addition to neutron and gamma radiation, these materials will be subjected to bombardment by low energy ions and neutral particles. Previous works carried out in silica have shown a dramatic surface electrical and optical degradation with a marked temperature dependence when the material is subjected to proton or alpha particle bombardment, due to loss of oxygen from the surface caused by preferential sputtering by energetic ions. Therefore, it was necessary to extend the study to the main candidate ceramic insulators for ITER (alumina, BeO and AlN), in order to evaluate possible issues for both diagnostic and heating and current driven systems. A clear optical and electrical degradation have been found in all the materials studied after implantation, in general this appears to be an issue common to all the insulator materials studied. This degradation is related with oxygen loss from the implanted zone for alumina and BeO, as observed previously for silica, and nitrogen loss for AlN. For silica implanted at higher energies data show surface degradation in all cases again due to loss of oxygen with a markedly different behaviour for each implanted ion.

Electrical surface degradation of electron irradiated sapphire and silica

Two types of oxides, silica and sapphire have been irradiated with 1.8 MeV electron and 54 keV He + in order to study surface electrical and optical degradation processes. It has been found that both materials suffer severe surface degradation as a consequence of radiation induced oxygen removal for either 1.8 MeV electron irradiation or 54 keV He + implantation. Degradation is higher in the case of alpha particle bombardment, but the results strongly suggest that the fundamental processes taking place are basically the same. Ionizing radiation rather than knock-on displacements appears to be the origin of the severe oxygen removal from the irradiated surface. The possibility of such surface degradation in insulators for ITER and future fusion reactors needs to be fully assessed.

Ion irradiation induced nitrogen mobility in a GaInNAs quantum well laser

Changes in the optical properties in GaInNAs/GaAs quantum wells after alpha particle bombardment followed by low temperature annealing are reported. Both blue and red shifts of the lasing wavelength are observed under different annealing conditions. This differs from the usually observed blue shift which is found after high-temperature post-grown annealing. Competing processes that result in the lasing wavelength shifts are energetic considerations which act to increase the number of Ga–N and In–As bonds (maximize the cohesive energy), minimizing the strain of the system which increases the number of In–N and Ga–As bonds (large-ion-small-ion links), maximizing the number of N located at lattice sites effective at shrinking the band-gap and moving the N position within the quantum well. For the case of high-temperature post-grown annealing the increase of Ga–As and In–N bonding wins, resulting in the blue shift observed. The wavelength shifts are discussed in terms of these competing mechanisms.

Surface electrical degradation for low mass ion implanted SiO 2: Dependence on ion mass, energy and dose rate

KS-4V quartz glass (SiO 2) is a candidate material to be used in ITER diagnostic systems where it will play an important role for optical components and possibly as electrical insulator. In addition to neutron and gamma radiation, the material will be subjected to bombardment by low energy ions and neutral particles. Previous work has shown severe electrical and optical degradation with a marked temperature dependence when the material is subjected to proton or alpha particle bombardment, due to loss of oxygen from the surface caused by preferential sputtering by energetic ions. In this work, a systematic study of ion bombardment induced surface degradation as a function of the ion mass, energy and dose rate has been carried out. A clear dependence on ion mass has been observed, with degradation occurring much more rapidly for heavier ions. Also the surface electrical degradation depends strongly on the implanted particle energy, degradation is higher for higher energy. No dependence on dose rate was observed.

Neutron yield and dose equivalent from heavy ion interactions on thick target

Thick target neutron yields and angular distributions are essential for shielding calculations for ion beam accelerators. Most of such measurements available in the literature are for proton and alpha particle bombardments. In case of heavy ions, very few data are available in the energy region of 20 MeV amu −1 and below. We report here the neutron yield, double differential neutron yields and neutron dose equivalent values obtained from the double differential yields at 0° and 90° with respect to the beam for various heavy ions in the energy range of 3.5–7.0 MeV amu −1. Pulse shape discrimination was used to separate neutrons from gamma rays and time of flight technique was used for energy measurement. The double differential neutron yields were fitted using the moving source model and the nuclear temperature and source intensity are also determined. The neutron yield increases inversely with the mass of the projectile except in the case of 7Li where the yields are much lower than that obtained from 11B. This could be due to the structure of the loosely bound 7Li projectile. The neutron dose equivalent shows increasing trend with the decrease of the mass of the projectile.

Influence of alpha particle bombardment and postannealing on photoluminescence from GaAs/Al0.35Ga0.65As multiple quantum wells

Multiple quantum well (MQW) samples grown by the molecular beam epitaxy method were irradiated by alpha particles from isotope Pu239. The photoluminescence (PL) spectra and PL integrated intensity dependencies are presented at various alpha particle fluences, up to 1011 cm−2. The experimental results are in agreement with a model which assumes that point centers (residual impurities and point defects introduced during irradiation) are responsible for PL intensity decrease with the alpha particle fluence. It was found that annealing of irradiated MQW samples at a temperature above 650 K nearly restores the PL intensity. An enhancement of PL by more than an order of magnitude was observed at annealing temperatures higher than 850 K, just before GaAs and Al0.35Ga0.65As interdiffusion begins.

Optical properties of as grown and ion implanted (Ar +,N 2+,α) GaAs nipi doping superlattices

A brief review of the optical properties of GaAs nipi doping superlattices (DSLs) subjected to N 2 +, Ar + ions, and alpha particle bombardment is given. Several experimental techniques, such as low temperature CW and time resolved photoluminescence (CW and TR-LTPL) as well as Raman spectroscopy (RS) and spectroscopic ellipsometry (SE) have been used to detect new optically active bands. An attempt is made to explain the origin of these new bands.

Angular dependence of defects introduced in GaAs by alpha-particle bombardment

It is commonly assumed that ion beams used for channelling experiments create little damage when moving along a principal axial channel of a crystal. We have employed deep level transient spectroscopy (DLTS) to characterise the defects induced by 300 keV He-ions in a GaAs crystal when entering it along the 〈100〉 axis (hyperchannelling: α i = 0°) as well as at small angles with respect to this axis ( α i ≤ 1.2°). The results we obtained indicate that the commonly observed alpha-particle induced defects in Si-doped GaAs (As VI As pairs, isolated As V and a Si-related metastable defect) were introduced at all angles of incidence investigated. The concentration of these defects was a minimum for α i = 0 and increased with increasing angle of incidence. Finally, we observed a difference between the relative concentrations of defects introduced during hyperchannelling and during bombardment off the channel axis.

Excitation functions and yields of the reactions induced by alpha-particle bombardment of natural silver

Stacked targets of natural silver were bombarded by α-particles of energies up to 26.3 MeV. The excitation functions of the 107Ag(α,n) 110mIn, 107Ag(α,pn) 109Cd and 109Ag(α,2n) 111In reactions were determined. Based on these results thick target yields were calculated. The experimental results were compared with the calculations made using the exciton model. Both are basically in agreement.