High-energy Proton Beam Research Articles

Research and Assessments of Geomagnetically Induced Currents

The geomagnetic storm which is caused by the sun's activity is a global natural disaster. When the sun surface activity is exuberant, especially in sun spots period, the surface of the sun will release X-ray, ultraviolet, visible and high-energy proton or electron beam. Part of the charged particles form current and influence the earth's magnetic field, current shock caused severe change occurs, geomagnetic happens. it can induce Geomagnetically induced currents (GIC).The GIC has very big effect on various man-made long distance conductors. The electric field produced during a geomagnetic disturbance is dependent on the magnitude and frequency of magnetic field variations and the Earth’s surface impedance. The GIC in a conductor system is also related to the infrastructure of the system. This paper introduces the principle of GIC, algorithm method and the geomagnetic storms rules.

Initial observations of cavitation-induced erosion of liquid metal spallation target vessels at the Spallation Neutron Source

During operation of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory the mechanical properties of the AISI 316L target module are altered by high-energy neutron and proton radiation. The interior surfaces of the target vessel are also damaged by cavitation-induced erosion, which results from repetitive rapid heating of the liquid mercury by high-energy proton beam pulses. Until recently no observations of cavitation-induced erosion were possible for conditions fully prototypic to the SNS. Post-Irradiation Examination (PIE) of the first and second operational SNS targets was performed to gain insight into the radiation-induced changes in mechanical properties of the 316L target material and the extent of cavitation-induced erosion to the mercury vessel inner surfaces. Observations of cavitation-induced erosion of the first and second operational SNS target modules are presented here, including images of the target vessel interiors and specimens removed from the target beam-entrance regions.

Electrochemical behaviour of stainless steel in PWR primary coolant conditions: Effects of radiolysis

Few data are available in the literature on the role of the water radiolysis on the corrosion of stainless steel core components in PWR operating conditions (300 °C, 155 bar). The present approach uses a high energy proton beam to control the production of radiolytic species at the interface between a stainless steel sample and water in a high temperature and high pressure (HP–HT) electrochemical cell working in the range 25 °C/1 bar–300 °C/90 bar. The cell is designed to record the free corrosion potential of the AISI 316L/water interface mounted in line with a cyclotron delivering the proton beam. The evolution of the potential is compared before, during and after the proton irradiation. The first results are obtained with an aqueous solution containing boron, lithium and dissolved hydrogen, as in PWR primary coolant circuit. The stainless steel/water interfaces are irradiated between 25 °C and 300 °C with protons emerging at 22 MeV at the interface. The flux is varied by five orders of magnitude, from 6.6 × 10 11 to 6.6 × 10 15 H + m −2 s −1. The evolution of the free corrosion potential is highly dependent on the temperature and/or pressure. For a given temperature and pressure, it evolves with the flux and the ageing of the AISI 316L/water interfaces. An important role of the temperature of irradiation on the electrochemical response was observed. These results give a better understanding of the role of radiolysis on stainless steel corrosion in high temperature conditions.

Yields of Fission Products in the Gamma Induced Fission of Preactinides and Actinides

Nuclear data such as fission cross-sections and yields of fission products in neutronand gammainduced fission of pre-actinides and actinides are important for the Accelerator-Driven Subcritical systems (ADSs). Particularly yields of fission products in high energy neutronand gamma-induced fission of long lived minor actinides (Np, Pu, Am and Cm) and pre-actinides (e.g., Pb and Bi) are needed for decay heat calculation. This is because in ADSs high energy (GeV) proton beam from accelerator are bombarded on Pb and Bi to produce high energy neutron by spallation process, which can incinerate minor actinides and transmute long-lived fission products to solve the problem of radioactive hazard. In this process high energy γ-ray also produce, which can cause reaction and fission of the spallation source and minor actinides. We present the yields of fission products from the bremsstrahlung induced fission of Bi and Pb by using 50, 60, 70 MeV and 2.5 GeV electron beam of the Pohang Accelerator Laboratory, Korea. The yields of fission products obtained in the 8 – 10 MeV bremsstrahlung induced fission of Th, U and Pu using Microtron at Mangalore University and electron LINAC at EBC centre, Kharghar, New-Mumbai, India are also discussed.

Performance of electronic devices submitted to X-rays and high energy proton beams

In this work we have studied the radiation effects on MOSFET electronic devices. The integrated circuits were exposed to 10 keV X-ray radiation and 2.6 MeV energy proton beam. We have irradiated MOSFET devices with two different geometries: rectangular-gate transistor and circular-gate transistor. We have observed the cumulative dose provokes shifts on the threshold voltage and increases or decreases the transistor’s off-state and leakage current. The position of the trapped charges in modern CMOS technology devices depends on radiation type, dose rate, total dose, applied bias and is a function of device geometry. We concluded the circular-gate transistor is more tolerant to radiation than the rectangular-gate transistor.

Preliminary study on the thorium-loaded accelerator-driven system with 100 MeV protons at the Kyoto University Critical Assembly

At the Kyoto University Critical Assembly (KUCA), spallation neutrons generated by high-energy proton beams are injected into the thorium-loaded systems on March 2010. By combining the Fixed Field Alternating Gradient (FFAG) accelerator with the thorium-loaded system at KUCA, a series of the ADS experiments is carried out under conditions whereby the spallation neutrons are generated at a tungsten target by 100 MeV protons at an intensity of 30 pA. Prompt neutron behavior in the time evolution is observed and thorium fission reactions are attained through the experiments and calculations, respectively. And the effects of neutron leakage and spectrum softening are experimentally observed through the neutron multiplication and reaction rate analyses. From the experimental and numerical analyses, in the future, experimental conditions need to be improved to attain further neutron multiplication using the variation of fuels (thorium, highly-enriched and natural uranium) and moderators (graphite, polyethylene, aluminum and beryllium).

Monte Carlo evaluation of the Filtered Back Projection method for image reconstruction in proton computed tomography

Abstract In this paper the use of the Filtered Back Projection (FBP) Algorithm, in order to reconstruct tomographic images using the high energy (200–250 MeV) proton beams, is investigated. The algorithm has been studied in detail with a Monte Carlo approach and image quality has been analysed and compared with the total absorbed dose. A proton Computed Tomography (pCT) apparatus, developed by our group, has been fully simulated to exploit the power of the Geant4 Monte Carlo toolkit. From the simulation of the apparatus, a set of tomographic images of a test phantom has been reconstructed using the FBP at different absorbed dose values. The images have been evaluated in terms of homogeneity, noise, contrast, spatial and density resolution.

TH-E-BRC-05: Dosimetric Effects of Tissue Heterogeneity and Small Field Size in Proton Therapy - a Monte Carlo Study

Purpose: Proton beams have finite range and a potential to deliver a more conformal dose to the treatment target while sparing surrounding healthy tissues. To fully take advantage of the dosimetric advantage of proton beams, accurate dose calculation and range determination, especially for heterogeneous tissue and small fields, are important. The purpose of this work is to study the dosimetric effects of tissue density change and small field size in proton therapy plans using Monte Carlo methods. Methods: Using Monte Carlo code MCNPX 2.5.0, we simulated the proton dose distribution for the following cases: 1) a water phantom with heterogeneity inserts of various densities; 2) a water phantom using various beam sizes from 0.1, 0.25, 0.5, 2.0, 4.0 and 8.0 cm), 3) a phantom of low density (from 0.4 to 0.9 g/cm3 with 0.1 g/cm3 density interval) with proton beam energy at 150 MeV and 250 MeV respectively. Results: Proton penetration range and dose distributions changed significantly with inserts of various densities. Proton Bragg curves degraded when small beam with beam radius at several mm range. Proton Bragg curves degraded also when high energy proton beam irradiated to low density material. For high energy proton beam and small size beam, the Bragg curves degraded more significantly. For high energy proton beam and low density tissue, the Bragg curves degraded more significantly. Comparison of dose distributions between Monte Carlo simulation and treatment planning system calculations is underway. Conclusion: Accurate proton dose calculations are challenging in protontreatment planning for heterogeneous tissues. For low density tissue and small field size beams, proton Bragg curves degrades significantly and needs to take into account in protontreatment planning. By simulating detailed particle transport and energy deposition, Monte Carlo simulations provide accurate dose calculations in inhomogeneous tissues and for small field size beams.

Cavitation inception and damage effects in liquid mercury exposed to a high-energy pulsed proton beam.

The Oak Ridge National Laboratory Spallation Neutron Source (SNS) employs a high-energy proton beam incident on a liquid mercury target to generate short bursts of neutrons. Concomitant with neutron production is the rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these bubbles may result in the premature erosion of the target’s steel walls. We report on a multi-pronged effort to both understand and address the problem by (1) inhibiting cavitation inception using bubble injection, (2) analyze cavitation and cavitation cloud dynamics using passive noise diagnostics, and (3) mitigating vessel wall damage using surface modification techniques. [Work supported by the ORNL Spallation Neutron Source, which is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.]

Microstructure evolution of nanostructured and submicrometric porous refractory ceramics induced by a continuous high-energy proton beam

The production of radioactive ion beams by the isotope mass separation online (ISOL) method requires a fast diffusion and effusion of nuclear products from thick refractory target materials under high-energy particle beam irradiation. A new generation of ISOL nanostructured and submicrometric porous materials have been developed, exhibiting enhanced release of exotic isotopes, compared to previously used conventional micrometric materials. A programme was developed at PSI within the framework sof the Design Study of EURISOL, the next generation European ISOL-type facility to study aging under irradiation on porous ceramic pellets and dense thin metal foils at high temperatures. Ceramic oxides and carbide samples underwent proton damage with fluence up to 3.0 × 10 20 and 1.3 × 10 21 cm −2 respectively. The post-irradiation examination on Al 2O 3, Y 2O 3 and SiC – C nanotube composite matrices show a proton-induced densification region in which a moderate grain growth occurred. The microstructural evolution effects were associated to the combination of radiation-enhanced diffusion and thermal diffusion. The irradiated Al 2O 3 shows higher sintering rates than in similar non-irradiation isothermal conditions, in particular at the lowest irradiation temperature, subjected to a proton fluence inferior to 1.1 × 10 15 cm −2. The apparent activation energy for its sintering controlling mechanism was found to be between 44 and 88 kJ mol −1. However, despite the enhanced sintering, shrinkage and increased grain growth, the selected nanostructured and submicrometric TARPIPE materials did not display an average grain diameter above 2 μm, which confirms that these materials are suited as production targets for present and next generation ISOL facilities.

Shear punch testing of candidate reactor materials after irradiation in fast reactors and spallation environments

Ferritic/martensitic steels and nickel-base superalloys are potential materials for use in spallation targets and fusion and fast reactors. To investigate the effects of irradiation on these materials, tests were performed after irradiation in the high energy proton beam at the Paul Scherrer Institute (SINQ Target Irradiation Program (STIP), 570MeV), as well on specimens obtained from a driver duct irradiated in the Fast Flux Test Facility (FFTF). Dose accumulations were up to 18dpa for STIP irradiations (at 147–406°C) and up to 155dpa in FFTF (at 383–505°C). The helium/dpa ratios ranged from 0.2 to 80appm/dpa. Mechanical testing was performed at 25°C. Increases in shear yield and shear maximum stress with increasing dose mirrored the results observed from companion tensile tests.

Immunohistochemical Verification of Stereotactic Proton Radiosurgery Targeting Accuracy in the Rat Brain

We have developed a system for targeting functional areas in the rat brain with narrow proton beams. Due to the extremely sharp lateral dose falloff of high-energy proton beams, a cross-fire technique with multiple shoot-through beams converging on the target will be used to selectively irradiate small regions in the rat brain. The spatial accuracy of dose delivery is crucial and needs to be verified. This ongoing study intends to verify the accuracy and precision of the targeting method by developing immunohistochemical staining protocols based on IgG leakage through the radiation-induced breakdown of the blood-brain barrier (BBB) and various DNA damage markers. Male Sprague-Dawley (8 weeks, 150-190g) rats were subjected to hemispheric proton irradiation with 250 MeV proton beams at doses of 0 Gy, 8 Gy, and 25 Gy. IgG extravasation was used to show BBB damage from 4 to 72 hours after irradiation. Rat brains perfused with 4% paraformaldehyde-perfused were cryostat-sectioned and slide-mounted. Sections then underwent immunohistochemical staining using the ABC method (Santa Cruz Biotechnology). Radiation-induced H2AX phosphorylation, a sensitive marker of DNA double strand breaks (DSBs), was detected by Donkey anti-mouse IgG Alexa Fluor 488 (green), while nuclei were counterstained with propidium iodide (PI, red). After 25 Gy proton irradiation, radiation-induced BBB damage resulted in IgG extravasation as indicated by positive immunostaining for anti-IgG. Detection of γH2AX was also possible after hemibrain proton irradiation with 8 Gy. IgG staining is sensitive to local vascular radiation damage, which has the advantage of being maintained during longer time intervals (days to weeks rather than hours) compared to short-term DNA damage markers. The DSB marker γH2AX can be used for rapid confirmation of the targeted area. IgG staining and γH2AX immunofluorescences are useful for microscopic verification of the targeting accuracy of small-animal radiosurgery procedures with sub-millimeter resolution.

Therapeutic application of metallic nanoparticles combined with particle-induced x-rayemission effect

Metallic nanoparticles (MNP) are able to release localized x-rays when activated with a highenergy proton beam by the particle-induced x-ray emission (PIXE) effect. The exploitationof this phenomenon in the therapeutic irradiation of tumors has been investigated.PIXE-based x-ray emission directed at CT26 tumor cells in vitro, when administered witheither gold (average diameter 2 and 13 nm) or iron (average diameter 14 nm) nanoparticles(GNP or SNP), increased with MNP solution concentration over the range of 0.1–2 mg ml − 1. With irradiation by a 45 MeV proton therapy (PT) beam, higher concentrations had adecreased cell survival fraction. An in vivo study in CT26 mouse tumor modelswith tumor regression assay demonstrated significant tumor dose enhancement,thought to be a result of the PIXE effect when compared to conventionalPT without MNP (radiation-only group) using a 45 MeV proton beam (p < 0.02). Those receiving GNP or SNP injection doses of300 mg kg − 1 body weight before proton beam therapy demonstrated 90% or 75% tumor volumereduction (TVR) in 20 days post-PT while the radiation-only group showed only 18% TVRand re-growth of tumor volume after 20 days. Higher complete tumor regression (CTR) wasobserved in 14–24 days after a single treatment of PT with an average rate of 33–65% forthose receiving MNP compared with 25% for the radiation-only group. A lower bound oftherapeutic effective MNP concentration range, in vivo, was estimated as 30–79 µg g − 1 tissue for both gold and iron nanoparticles. The tumor dose enhancement may compensatefor an increase in entrance dose associated with conventional PT when treating large, solidtumors with a spread-out Bragg peak (SOBP) technique. The use of a combined highenergy Bragg peak PT with PIXE generated by MNP, or PIXE alone, may result in newtreatment options for infiltrative metastatic tumors and other diffuse inflammatorydiseases.

Production of cordycepin by a repeated batch culture of a Cordyceps militaris mutant obtained by proton beam irradiation

Cordycepin (3'-deoxyadenosine) is one of the most versatile metabolites of Cordyceps militaris due to its broad spectrum of biological activity. In our previous study, the C. militaris mutant G81-3, which produces higher levels of cordycepin, was obtained by high-energy proton beam irradiation. In this study, the effects of adenosine on cordycepin production in a surface liquid culture of the mutant and the wild type strains were investigated. For the mutant strain, the optimum dose of adenosine yielded a 30% increase in cordycepin production; the maximum levels of production with adenosine and without adenosine were 8.6g/l and 6.7 g/l, respectively. In contrast, the increase due to adenosine supplementation for the wild type strain was only 15% (3.1g/l with adenosine and 2.7 g/l without adenosine). Furthermore, a repeated batch culture, an efficient production method, was carried out to eliminate the relatively long lag phase of the mutant culture. Over four cycles, both the mutant and the wild type strain maintained a production level of more than 85% of that of the initial cycle. As a result, the disadvantage of the mutant was successfully overcome, resulting in a productivity (0.48 g/(ld)) higher than that of the batch culture (0.29 g/(ld)). The productivity for cordycepin obtained in this study is the highest reported value to date, and this method could be applied to large-scale production of cordycepin at industrial levels.

Evidence of the primary-color photoluminescence in ion (H+,H2+,C−) irradiated and thermal annealed SrTiO3

We have measured photoluminescence (PL) spectrum of (1) thermal-annealed SrTiO 3 /Si thin film and undoped SrTiO 3 single crystal; (2) SrTiO 3 single crystal irradiated by high energy (3 MeV) proton, deuterium, and He ion beams and (3) SrTiO 3 single crystal irradiated by low energy (60 keV) H + and C − ions. Two PL emissions are induced in (1) and (2) at visible frequencies 3 and 2.45 eV, while another PL peak is induced at 2 eV in (3). When compared with our previous PL experiments on high-temperature annealed SrTiO 3 /SiO 2 /Si thin film and 3 MeV proton (H + ) irradiated STO single crystal, these results confirm that the three PL emissions with blue (3 eV), green (2.45 eV), and red-orange (2 eV) frequencies originate indeed from SrTiO 3 . These primary-color PL effect induced at room-temperature makes STO a strong candidate material for future oxide-based optoelectronic application.

Detecting cavitation in mercury exposed to a high-energy pulsed proton beam

The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 muC will be reported on. Cavitation was initially detected for a beam charge of 0.082 muC by the presence of an acoustic emission approximately 250 mus after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 muC and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber ( approximately 300 mus), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.

Tuning of the Electronic Characteristics of ZnO Nanowire Field Effect Transistors by Proton Irradiation

We demonstrated a controllable tuning of the electronic characteristics of ZnO nanowire field effect transistors (FETs) using a high-energy proton beam. After a short proton irradiation time, the threshold voltage shifted to the negative gate bias direction with an increase in the electrical conductance, whereas the threshold voltage shifted to the positive gate bias direction with a decrease in the electrical conductance after a long proton irradiation time. The electrical characteristics of two different types of ZnO nanowires FET device structures in which the ZnO nanowires are placed on the substrate or suspended above the substrate and photoluminescence (PL) studies of the ZnO nanowires provide substantial evidence that the experimental observations result from the irradiation-induced charges in the bulk SiO(2) and at the SiO(2)/ZnO nanowire interface, which can be explained by a surface-band-bending model in terms of gate electric field modulation. Our study on the proton-irradiation-mediated functionalization can be potentially interesting not only for understanding the proton irradiation effects on nanoscale devices, but also for creating the property-tailored nanoscale devices.

Evaluation of the anticorrosive properties of benzotriazole alkyl derivatives on 6% Sn bronze alloy

This paper focuses on the anticorrosive behaviour of surface films formed by different benzotriazole alkyl derivatives on a Cu6Sn bronze (B6), whose composition is similar to materials used for outdoor artefacts. Some alkyl derivatives of the 1,2,3-benzotriazole (BTA) as: 5-hexyl-1,2,3-benzotriazole; 5-dodecyl-1,2,3-benzotriazole and [5-(1-undecyl)dodecyl]-1,2,3-benzotriazole were synthesized in order to investigate the influence exerted by the aliphatic chain on the inhibiting properties of the base molecule (BTA) toward bronze corrosion. The protective efficiency of the organic films, after a preliminary evaluation by electrochemical measurements, was determined by thin layer activation (TLA) and gravimetric techniques on the samples submitted to artificial weathering experiments in acid rain. For TLA measurements a γ-emitting radio nuclide 65Zn ( t 1/2 = 244 days), used as a corrosion tracer, was produced on the bronze surface by a high energy proton beam. At the end of artificial weathering exposures the radioactivity recovered on the bronze surface, once it was treated with a picking solution, allowed determination of the thickness loss. All the results arising from the different techniques, used in this study, show that BTA molecules bearing long aliphatic chain act as the best corrosion inhibitors.

Accurate measurements of high energy proton beam by secondary electron compensation

Accuracy in the measurement of an intense high-energy proton beam is generally disturbed by high energy proton induced secondary electron emission. In the present work,the compensation mechanism for secondary electron emission is investigated for the accurate measurement of high-energy proton beam. An experimental approach with using three metal foils to compensate for secondary electron emission is implemented and described. The experiment is carried out on the HI-13 tandem accelerator. The current detected from the middle metal foil is 0.7% of the proton beam. The experimental results show that the measured current of the high-energy proton beam is reliable within 1%.

Low-energy neutrino factory design

The design of a low-energy (4 GeV) neutrino factory (NF) is described, along with its expected performance. The neutrino factory uses a high-energy proton beam to produce charged pions. The ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ decay to produce muons (${\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}$), which are collected, accelerated, and stored in a ring with long straight sections. Muons decaying in the straight sections produce neutrino beams. The scheme is based on previous designs for higher energy neutrino factories, but has an improved bunching and phase rotation system, and new acceleration, storage ring, and detector schemes tailored to the needs of the lower energy facility. Our simulations suggest that the NF scheme we describe can produce neutrino beams generated by $\ensuremath{\sim}1.4\ifmmode\times\else\texttimes\fi{}{10}^{21}$ ${\ensuremath{\mu}}^{+}$ per year decaying in a long straight section of the storage ring, and a similar number of ${\ensuremath{\mu}}^{\ensuremath{-}}$ decays.