Proton Bombardment Research Articles

Structural and Magnetic Changes Induced by Electron and Ion Irradiation on HOPG

In recent decades, many studies reported magnetism in carbon-based materials. This phenomenon was attributed to structural defects within the sample. Many authors showed an increase of magnetization in HOPG (Highly Oriented Pyrolytic Graphite) induced by proton bombardment, meanwhile the effect of electronic irradiation on the magnetic behavior has been unattended till now. The aim of this work is to contribute to the understanding of defect-induced effects on the structural and magnetic properties of graphite. For this purpose, we performed experiments of irradiation on HOPG with two different impinging projectiles −electrons and ions. The structural characterization of the bombarded samples was carried out by Raman spectroscopy. On both irradiated samples we identify the D band, associated to the disorder induced by bombardment, with significantly distinct contributions depending on the projectile type. In order to interpret Raman results, a theoretical model proposed by Ferrari et al. was used to classify the generated defects. The relationship between the induced damage and magnetization was evaluated by magnetic characterization measurements with a SQUID (Superconducting Quantum Interference Device). Our results suggest that electron bombardment produces a higher change in the magnetic order compared to the magnetization induced by ion bombardment.

GPU-accelerated visualisation of ADS granular flow target model

This paper presents a discrete element method to handle particle collision detection and responses in transport simulation the simulation of transport of protons and neutrons in granular flow target geometric model based on GPUs. Discrete element method was adopted in the realisation of large-scale particle visualisation. The method simulates and solves edge detection, position judging, motion direction, calculation of the next collision point using GPU acceleration during the process of transport, and demonstrates the complete interaction process through OpenGL. Results show that the model presented exploits the acceleration of GPUs and has gained remarkable functional improvement compared with traditional method using solely CPUs. In addition, we used the MCNPX to calculate this model with high-speed proton bombardment. The distribution of power energies verifies that the granular flow target model is reliable and feasible.

Cyclotron production of 52Mn and Monte Carlo benchmarking

52Mn with 5.6 day half-life was produced by proton bombardment on natural chromium. Natural chromium was electroplated on the copper substrate and to reach a high activity product, the optimum energy range of bombardment was selected to be 16–6 MeV via theoretical calculation. It yielded 12.1 ± 1.2 MBq μA−1 h−1 after 1 h bombardment by the current of 150 μA. Separation of chromium and manganese was carried out by extraction method to achieve a more pure product. On the other hand, the production route, in parallel to this experiment, was simulated using Monte Carlo method, and the production yield was estimated and it showed a good agreement with the experimental results.

Evolution of the emissivity of tungsten at high temperature with and without proton bombardment

The Solar Probe Plus mission (NASA) will be the first mission to enter the solar corona. The spacecraft will orbit the Sun at 8.5 solar radii from the Sun’s surface at closest approach. Some metallic parts of the two on-board instruments, SWEAP (a Faraday cup) and FIELDS (antennas), will directly face the Sun, while the rest of the payload will be protected by a heat shield. For application to these instruments, a candidate refractory material, tungsten, was studied, confronting conditions similar to the ones expected close to the Sun: high radiative flux leading to high temperatures (1100–2500K) and proton bombardment (1 and 4keV; 1016, 1017 and 1018ionsm−2s−1) to simulate the solar wind in high vacuum (10−4Pa). Total directional and hemispherical emissivities in the two wavelength ranges 0.6–2.8 and 0.6–40μm were recorded in situ during treatments. Material characterization was performed before and after each high temperature and bombardment experiment to correlate a possible emissivity evolution to other material properties: mainly the microstructure and the surface topography. This paper reports some results on the evolution of the emissivity at high temperature for two different tungsten materials elaborated by two manufacturers – having thus different initial surface states, impurity contents and microstructures – and also with the addition of proton bombardment to the high temperature. However, the proton bombardment showed no effect on the surface topography or the emissivity, despite the fact that the ion fluxes used in our experiments were up to three orders of magnitude higher than the one expected from the solar winds.

Development of (111)In-labeled porphyrins for SPECT imaging.

The aim of this research was the development of (111)In-labeled porphyrins as possible radiopharmaceuticals for the imaging of tumors. Ligands, 5, 10, 15, 20-tetrakis (3, 5-dihydroxyphenyl) porphyrin) (TDHPP), 5, 10, 15, 20-tetrakis (4-hydroxyphenyl) porphyrin (THPP) and 5, 10, 15, 20-tetrakis (3,4-dimethoxyphenyl) porphyrin) (TDMPP) were labeled with (111)InCl3 (produced from proton bombardment of natCd target) in 60 min at 80 ºC. Quality control of labeled compounds was performed via RTLC and HPLC followed by stability studies in final formulation and presence of human serum at 37 ºC for 48 h as well as partition coefficient determination. The biodistribution studies performed using tissue dissection and SPECT imaging up to 24h. The complexes were prepared with more than 99% radiochemical purity (HPLC and RTLC) and high stability to 48 h. Partition coefficients (calculated as log P) for (111)In-TDHPP, (111)In-THPP and (111)In-TDMPP were 0.88, 0.8 and 1.63 respectively. Due to urinary excretion with fast clearance for (111)In-TDMPP, this complex is probably a suitable candidate for considering as a possible tumor imaging agent.

Optical system of the proton bombarding setup on the U-70 accelerator at the institute for high energy physics

The results of physical substantiation and the magnetic optical scheme of the proton radiographic setup with an energy of 50–70 GeV and the field of view of a diameter not smaller than 200 mm are presented.

Proton Bombardment in Mercury Target for Neutron Production - Impact Dynamics on Interface between Liquid and Solid Metals

Innovative researches using neutrons are being performed at the Materials & Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC), in which a mercury target system is installed as MW-class pulse spallation neutron sources. In order to produce neutrons by the spallation reaction, proton beams are injected into the mercury target. At the moment when the intense proton beam hits the target, pressure waves are generated in mercury because of abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall, i.e. the interface between liquid and solid metals. Localized impacts by microjets and/or shock waves that are caused by cavitation bubble collapse impose pitting damage on the vessel wall. The pitting damage that degrades the structural integrity of the target vessel is a crucial issue for the high power mercury targets. Therefore, the mitigation techniques for the pitting damages and cavitation are needed to reach the MW-class pulsed spallation neutron sources.

Characterization of the effects of 3-MeV proton irradiation on fine-grained isotropic nuclear graphite

The irradiation-induced damage on the fine-grained isotropic nuclear graphite, IG-110, was investigated by 3-MeV proton irradiation at room temperature. The irradiation effects were characterized using scanning electron microscopy, transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and nano-indentation. The surface morphology showed a fragmented shape after irradiation, indicating that the surface microstructure of the graphite was damaged by proton bombardment. The TEM images revealed clear and convincing evidence for the increase in defect clusters (probably interstitial clusters), basal plane bending, and basal plane dislocations, which might be the main reason for property changes. Raman studies indicated a rapid increase in the interstitial and vacancy defects, and decrease of in-plane “crystallite size”. The XRD results indicated a slight increase in the interlayer spacing and decrease in crystallite size. The enhancement in the hardness and modulus can be attributed to the pinning of basal plane dislocations by lattice defects produced by proton irradiation.

Effect of MeV protons on the phase behaviour and thermal stability of polytetrafluoroethylene

Thermomechanical spectroscopy analysis was used to study the influence of accelerated protons on the molecular-topological properties of polytetrafluoroethylene (PTFE). The study showed changes in a wide number of polymer parameters as a result of bombardment with 1, 2 and 4 MeV protons at fluences up to 2 × 1015 protons/cm2. The basic topological process occurring under proton bombardment is amorphicity, as found for γ-irradiation of PTFE. The flow temperature of bombarded PTFE significantly decreases with increasing the fluxes and energy of the accelerated protons. The general process resulting from proton bombardment is cleavage of C-F bonds, leading to formation of “centered” radicals ∼CF2CF · CF2∼ and HF. The thermal stability of bombarded PTFE is below than that of virgin polymer. The rate of thermal destruction noticeably increases and the temperature of the initiation of effective thermal decomposition decreases after bombardment. The gaseous products generated during thermal destruction of the bombarded and virgin PTFE are similar.

Epithermal neutron formation for boron neutron capture therapy by adiabatic resonance crossing concept

Low-energy protons from the cyclotron in the range of 15–30 MeV and low current have been simulated on beryllium ( Be ) target with a lead moderator around the target. This research was accomplished to design an epithermal neutron beam for Boron Neutron Capture Therapy (BNCT) using the moderated neutron on the average produced from 9 Be target via (p, xn) reaction in Adiabatic Resonance Crossing (ARC) concept. Generation of neutron to proton ratio, energy distribution, flux and dose components in head phantom have been simulated by MCNP5 code. The reflector and collimator were designed in prevention and collimation of derivation neutrons from proton bombarding. The scalp-skull-brain phantom consisting of bone and brain equivalent material has been simulated in order to evaluate the dosimetric effect on the brain. Results of this analysis demonstrated while the proton energy decreased, the dose factor altered according to filters thickness. The maximum epithermal flux revealed using fluental, Fe and bismuth ( Bi ) filters with thicknesses of 9.4, 3 and 2 cm, respectively and also the epithermal to thermal neutron flux ratio was 103.85. The potential of the ARC method to replace or complement the current reactor-based supply sources of BNCT purposes.

M X-ray cross sections from 75 to 300 keV proton bombardment of selected 5d transition elements

M X-ray production cross sections for selected thick targets of Hf, W, Re, Pt, Au and Pb impacted by 75–300keV protons are presented and compared with ECPSSR and RPWBA theories using different atomic data bases, including comparisons with other investigators. The results for the major M X-ray transitions exhibit a universal character with respect to the reduced proton velocity in agreement with expectations from theory.

Implementation of Multi-Curie Production of (99m)Tc by Conventional Medical Cyclotrons.

(99m)Tc is currently produced by an aging fleet of nuclear reactors, which require enriched uranium and generate nuclear waste. We report the development of a comprehensive solution to produce (99m)Tc in sufficient quantities to supply a large urban area using a single medical cyclotron. A new target system was designed for (99m)Tc production. Target plates made of tantalum were coated with a layer of (100)Mo by electrophoretic deposition followed by high-temperature sintering. The targets were irradiated with 18-MeV protons for up to 6 h, using a medical cyclotron. The targets were automatically retrieved and dissolved in 30% H2O2. (99m)Tc was purified by solid-phase extraction or biphasic exchange chromatography. Between 1.04 and 1.5 g of (100)Mo were deposited on the tantalum plates. After high-temperature sintering, the (100)Mo formed a hard, adherent layer that bonded well with the backing surface. The targets were irradiated for 1-6.9 h at 20-240 μA of proton beam current, producing up to 348 GBq (9.4 Ci) of (99m)Tc. The resulting pertechnetate passed all standard quality control procedures and could be used to reconstitute typical anionic, cationic, and neutral technetium radiopharmaceutical kits. The direct production of (99m)Tc via proton bombardment of (100)Mo can be practically achieved in high yields using conventional medical cyclotrons. With some modifications of existing cyclotron infrastructure, this approach can be used to implement a decentralized medical isotope production model. This method eliminates the need for enriched uranium and the radioactive waste associated with the processing of uranium targets.

2 MeV PROTON IRRADIATION EFFECTS ON ZnO SINGLE CRYSTAL

Melt grown ZnO single crystal was irradiated with varying fluence of 2 MeV proton beam in the range of 1 × 1016 H +/cm2 to 5 × 1017 H +/cm2. The irradiated spots exhibited varying degree of discoloration due to the irradiation indicating surface and volume defects. The surface roughness of the irradiated spots was measured using atomic force microscopy indicating surface modification of the sample. The extent of the damage on the ZnO single crystal from radiation was assessed using Raman spectroscopy. The emergence of the A1( LO ) band at 579 cm-1 pointed to the significant surface alteration in the ZnO crystal due to proton bombardment.

Production of 89Zr via the 89Y(p,n)89Zr reaction in aqueous solution: Effect of solution composition on in-target chemistry

The existing solid target production method of radiometals requires high capital and operational expenditures, which limit the production of radiometals to the small fraction of cyclotron facilities that are equipped with solid target systems. Our objective is to develop a robust solution target method, which can be applicable to a wide array of radiometals and would be simply and easily adopted by existing cyclotron facility for the routine production of radiometals. We have developed a simplified, solution target approach for production of (89)Zr using a niobium target by 14 MeV energy proton bombardment of aqueous solutions of yttrium salts via the (89)Y(p,n)(89)Zr nuclear reaction. The production conditions were optimized, following a detailed mechanistic study of the gas evolution. Although the solution target approach avoided the expense and complication of solid target processing, rapid radiolytic formation of gases in the target represents a major impediment in the success of solution target. To address this challenge we performed a systematic mechanistic study of gas evolution. Gas evolution was found to be predominantly due to decomposition of water to molecular hydrogen and oxygen. The rate of gas evolutions varied >40-fold depending on solution composition even under the same irradiation condition. With chloride salts, the rate of gas evolution increased in the order rank Na<Ca<Y. However, the trend was reversed with the corresponding nitrate salts, and further addition of nitric acid to the irradiating solution minimized gas evolution. At optimized condition, (89)Zr was produced in moderate yield (4.36 ± 0.48 MBq/μA • h) and high effective specific activity (464 ± 215 MBq/μg) using the solution target approach (2.75 M yttrium nitrate, 1.5 N HNO3, 2h irradiation at 20 μA). The novel findings on substrate dependent, radiation-induced water decomposition provide fundamental data for the development and optimization of conditions for solution targets. The developed methodology of irradiation of nitrate salts in dilute nitric acid solutions can be translated to the production of a wide array of radiometals like (64)Cu, (68)Ga and (86)Y, and is well suited for short-lived isotopes.

Uptake, Biological Fate, and Toxicity of Metal Oxide Nanoparticles

Studies of the uptake, biological fate, and toxicity of several metal oxide nanoparticles (NPs), such as Al2O3, TiO2, CeO2‐x, and ZnO NPs undertaken in the European Project “Health Impact of Engineered Metal and Metal Oxide Nanoparticles: Response, Bioimaging and Distribution at Cellular and Body Level” are reviewed here. Metal oxide NPs are radiolabeled by direct proton bombardment of commercially available NPs or enriched during synthesis with 18O to generate 18F after‐proton bombardment. Size, degree of aggregation, and zeta potential of the metal oxide NPs are studied in the presence of proteins and cell media. NP uptake and intracellular fate are followed by ion beam microscopy (IBM), transmission electron microscopy, confocal Raman microscopy and confocal laser scanning microscopy. IBM allows for the quantification of the intracellular dose of NPs. Cell viability studies and the immune response are studied “in vitro” in primary alveoli, and immortalized cell lines. Biodistribution studies in rodents are performed with positron emission tomography following different exposure routes: intravenous, oral, topical, and inhalation using radiolabelled NPs. Activity per organ is quantified for the different uptake routes and with the time.

Cross sections of proton-induced reactions on 152Gd, 155Gd and 159Tb with emphasis on the production of selected Tb radionuclides

Cross sections are presented for various Dy, Tb and Gd radionuclides produced in the proton bombardment of 159Tb as well as for the reactions 152Gd(p,4n)149Tb and 155Gd(p,4n)152Tb up to 66MeV. The experimental excitation functions are compared with theoretical predictions by means of the geometry-dependent hybrid (GDH) model as implemented in the code ALICE/ASH, as well as with values from the TENDL-2012 library and previous literature experimental data, where available. Physical yields have been derived for the production of some of the medically important radioterbiums, namely 149Tb (radionuclide therapy), 152Tb (PET) and 155Tb (SPECT). The indirect production of high-purity 155Tb via the decay of its precursor 155Dy is reported. The possibility of a large-scale production facility based on a commercial 70MeV cyclotron is also discussed.

Dry Distillation of Radioiodine from TeO2 Targets

As medical cyclotrons are becoming more abundant, 123I and 124I are getting more attention as alternatives to 131I for diagnostics of thyroid disease. Both 123I and 124I provide better diagnostics, deliver less dose to patients and both reduce the risk of thyroid stunning, facilitating subsequent therapy. Dry distillation of radioiodine from tellurium dioxide targets has become the standard approach to producing these radioiodines. Setting up such a production of radioiodine is associated with a lengthy optimization of the process and for this purpose natural tellurium is often used for economical reasons. In this paper, the distillation parameters are scrutinized to ensure optimal distillation temperature, in order to minimize time spent and prevent loss of expensive target material. It is further demonstrated how the individual iodine isotopes, produced from proton bombardment of natTe, will diffuse out of the target in a time dependent ratio. We believe the effect is due to the isotopes having their maximum cross section at different energies. The individual isotopes produced will thus have their highest concentration at different depths in the target. This results in individual mean diffusion lengths and diffusion times for the different isotopes.

On the natural origin of bismuth-207

The existing and other possible versions of the cosmic origin of 207Bi (proton bombardment of lead ores) are analyzed on the basis of published data. The 207Bi activity level attained in these processes is shown to be very low and impossible to detect. The version of the artificial origin of 207Bi is briefly discussed, but it does not make significant contribution to the contamination of BGO crystals, detected throughout the world. A hypothesis is put forward that the detected activity assigned to 207Bi can actually originate from 227Ac present in the objects under consideration.

Design measures to counteract pressure wave effects in the liquid metal target META:LIC

The liquid metal target concept META:LIC (MEgawatt TArget:Lead bIsmuth Cooled) is considered as a comparative target option for the long pulse spallation neutron source ESS (European Spallation Source). MW-class proton bombardment of liquid metal can result in pressure waves that impact the structure of the target. An analytical and a thermo-mechanical analysis with ANSYS CFX/LS-DYNA is performed. For the analytical analysis a modified Joukowsky equation to approximate the thermally induced peak pressure at the beginning of the pulse is introduced. The analysis indicates that the stressing of the target container due to pressure pulses initiated at the beginning and end of each pulse is less important compared to the stressing due to integral thermal expansion of the fluid during the full pulse period. Additionally, it is shown that a ramped proton pulse reduces the maximum pressure at the beginning of a pulse. Dedicated design measures to prevent high stresses and cavitation on the target container are described. These design measures include an expansion volume and a spoiler enforcing flow detachment. Internal free surfaces in the target module are created. The feasibility of stable internal free surfaces is confirmed by CFD simulations, however an experimental confirmation is mandatory.

Bremsstrahlung in carbon thick targets by proton incidence

The subtraction of the continuum from an X-ray spectrum emitted by proton bombardment is usually carried out by means of a mathematical fitting. The purpose of the present work is to develop an analytical function to model the continuous spectrum generated in a PIXE experiment for different incident beam energies in carbon thick targets. With this purpose, PIXE spectra of a carbon bulk sample were measured in an ion accelerator. The proton beam energies were varied between 0.7MeV and 2MeV and the X-rays generated were collected by an energy dispersive spectrometer. The spectra analysis was performed taking into account the main effects underlying the production of the continuous spectrum. Nevertheless, for the cases considered here, it was found that the atomic bremsstrahlung is the most important and other contributions were neglected. The experimental spectra from carbon thick targets were corrected by self-absorption and detector efficiency. The results show that the spectral shape corresponding to thick targets corrected by these effects is similar to the functional behavior presented by thin targets.