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This study investigates that the subsurface pathways, travel time, and its interannual variability of Fukushima-derived tracers subducted with the North Pacific subtropical mode water (NPSTMW) using 22-year-long (1994-2015) eddy-resolving (1/12°) and eddy-permitting (1/4°) ocean reanalysis. The NPSTMW is a thick subsurface layer with low potential vorticity and relatively uniform potential density, making it a key indicator of the North Pacific oceanic conditions. A series of Lagrangian particle tracking simulations quantitatively revealed that the Fukushima-derived particles moved along the Kuroshio Extension (KE) and spread over the majority of the subtropical region in the northwestern Pacific within 4-5 years. Approximately 36% of the particles flowed eastward in the Kuroshio-Oyashio transition zone (KO) and thereafter reemerged to the sea surface at the remote area (near dateline), and 30% of particles moved along the KE. The remaining 34% subducted into NPSTMW layer and then widely spread out to the subtropical region along the re-circulation gyre (RG), exhibiting a subsurface pathway during entire particle tracking. When the particles were released, their pathway was immediately determined, whether it flowed along the KO (>36°N), KE (30°-36°N), or RG (<30°N). Furthermore, the interannual variability of the pathways was significantly associated with the dynamic states of KE, such as the path length of the Kuroshio jet. This result implies that understanding the subsurface dynamics and its variability of the KE and NPSTMW is crucial for predicting the dispersion of radioactive materials in the subsurface layer and its potential impact. [ABSTRACT FROM AUTHOR]

The FAST beamline is the injector for the planned Gamma-Ray Electron ENhanced Source (GREENS) program, which aims to achieve the demonstration and first application of a high-efficiency, high-average-power free-electron laser at 515 nm. FAST-GREENS requires high 5D peak brightness; transverse normalized projected emittances of 3 mm-mrad and a peak current of 600 A are the minimum beam requirements for the FEL to reach the 10% efficiency goal. In this work, studies of the low-energy section of the FAST beamline are presented toward these ends, including preliminary measurements of beam compression and beam emittance. An effort toward developing a high-fidelity simulation model that could be later optimized for FAST-GREENS is presented. [ABSTRACT FROM AUTHOR]

The FAST beamline is the injector for the planned Gamma-Ray Electron ENhanced Source (GREENS) program, which aims to achieve the demonstration and first application of a high-efficiency, high-average-power free-electron laser at 515 nm. FAST-GREENS requires high 5D peak brightness; transverse normalized projected emittances of 3 mm-mrad and a peak current of 600 A are the minimum beam requirements for the FEL to reach the 10% efficiency goal. In this work, studies of the low-energy section of the FAST beamline are presented toward these ends, including preliminary measurements of beam compression and beam emittance. An effort toward developing a high-fidelity simulation model that could be later optimized for FAST-GREENS is presented.

In this study, an integrated electrospray pyrolysis process was designed to continuously produce a representative nano-catalyst TiO2. A numerical model was also developed to simulate the flow behaviors and droplet transport inside the reactor. The electric field model and particle tracking model were coupled to describe the electrospray pyrolysis process. The effects of key parameters, including electrode configurations, applied voltage, droplet charge density, and flow type of carrying gas on the electric field distribution, particle distribution, and particle collection efficiency, were investigated to help the design and optimization of the integrated electrospray pyrolysis reactor. The results show that the electric potential and electric field strength decrease rapidly with increasing distance away from the nozzle. In addition, the results show that the droplet charge is an important parameter affecting the collection efficiency. The investigation of the key parameters shows that applying a voltage on the ring and using the "gas-bleed" introduction method are more conducive to the improvement in the collection efficiency. [ABSTRACT FROM AUTHOR]

The focusing and transmission of a sheet electron beam with periodic cusped magnetic (PCM) fields were studied for the terahertz traveling-wave tubes (TWT). Due to the limitation on the width of the sheet beam from the slow wave structure (SWS), the resulting transmission current density is inevitably high and the width of the sheet beam is highly disproportionate to the magnet system. This defines a situation different from before, which challenges the validity of the traditional PCM scheme. Thus, the focusing of a sheet beam in the above scenario was theoretically analyzed to evaluate the focusing conditions. A practical magnetic field system was then designed based on the offset-pole-piece PCM scheme with the shortened pole pieces, which can meet the focusing requirements, especially on the side focusing. The theoretical analysis and the modified PCM scheme lead to a significant improvement in the focusing/transmission of the sheet beam. The 3-D particle simulation showed that a stable long-distance transmission over 100 mm can be achieved with the two-plane PCM focusing where an elliptical-cross section sheet beam is assumed with dimensions of 0.6 mm × 0.11 mm, voltage of 24.5 kV, and current of 0.18 A. [ABSTRACT FROM AUTHOR]

Crossing the transition energy γ t in synchrotrons for high intensity proton beams requires well tuned jump schemes and is usually accompanied by longitudinal emittance growth. In order to avoid γ t crossing during proton operation in the projected SIS-100 synchrotron special high- γ t lattice settings have been developed, in order to keep γ t above the beam extraction energy. A further advantage of this scheme is the formation of alpha buckets which naturally lead to short proton bunches, required for the foreseen production and storage of antiprotons for the FAIR facility. Special attention is turned on the imperfections of the superconducting SIS-100 magnets because together with the high- γ t lattice settings, they could potentially lead to enhanced beam loss. The aim of the present work is to estimate the beam loss by means of particle tracking simulations. [ABSTRACT FROM AUTHOR]

Introduction: In radiotherapy, megaelectron volt (MeV) electrons are employed for treatment of superficial cancers. Magnetic fields can be used for deflection and deformation of the electron flow. A magnetic field is composed of non-uniform permanent magnets. The primary electrons are not mono-energetic and completely parallel. Calculation of electron beam deflection requires using complex mathematical methods. In this study, a device was made to apply a magnetic field to an electron beam and the path of electrons was simulated in the magnetic field using finite element method. Methods: A mini-applicator equipped with two neodymium permanent magnets was designed that enables tuning the distance between magnets. This device was placed in a standard applicator of Varian 2100 CD linear accelerator. The mini-applicator was simulated in CST Studio finite element software. Deflection angle and displacement of the electron beam was calculated after passing through the magnetic field. By determining a 2 to 5cm distance between two poles, various intensities of transverse magnetic field was created. The accelerator head was turned so that the deflected electrons became vertical to the water surface. To measure the displacement of the electron beam, EBT2 GafChromic films were employed. After being exposed, the films were scanned using HP G3010 reflection scanner and their optical density was extracted using programming in MATLAB environment. Displacement of the electron beam was compared with results of simulation after applying the magnetic field. Results: Simulation results of the magnetic field showed good agreement with measured values. Maximum deflection angle for a 12 MeV beam was 32.9° and minimum deflection for 15 MeV was 12.1°. Measurement with the film showed precision of simulation in predicting the amount of displacement in the electron beam. Conclusion: A magnetic mini-applicator was made and simulated using finite element method. Deflection angle and displacement of electron beam were calculated. With the method used in this study, a good prediction of the path of high-energy electrons was made before they entered the body. [ABSTRACT FROM AUTHOR]

The paper concerns the study of the ~5 MeV electron beam interaction with the thin layer experimental sample at the AREAL electron linear accelerator. The necessary exposure time and the irradiation effects parameters calculations have been performed using measured parameters of the beam and numerical simulations applying particle transport code FLUKA [1]. Numerical simulations with FLUKA provide estimation of the absorbed dose - the main parameter that defines the amount of the radiation induced crystalline structure defects. Calculations have been conducted for the experimental study of the irradiation effects on the parameters of the ferromagnetic composition Ba75Sr25TiO3 - Barium-Strontium-Titanate (BST) thin film. The main goal reached is the calculation of the required exposure time taking into account beam intensity, energy, spatial and angular distributions and experimental sample geometrical shape, size, composition and disposition for obtaining intended value of the absorbed dose. Beam parameters used for numerical simulations have been obtained from beam diagnostic measurements. [ABSTRACT FROM AUTHOR]

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Unlined pressure tunnels in sound rock, combined with pressurized sand traps at the downstream end, allow for low-cost construction of hydropower tunnel systems. This design concept is utilized in hydropower plants across the world. Currently, many such power plants are being upgraded with higher installed capacity, which may result in challenges with the sand trap efficiency. A physical scale model test, accompanied by 3D CFD simulations of a case study pressurized sand trap, has been studied for economic retrofitting. The geometric model scale is 1:36.67 while the velocity scale and sediment scale are 1:1 (same average flow velocity and sediment size in model and prototype). This is currently an uncommon scaling approach but with several advantages, as presented in this paper. Various options for retrofitting were investigated. A combined structure of ramp and ribs was found to significantly improve the sediment trap efficiency. The main novelties from this work are the proposed design of the combined ramp and rib structure. Secondary results include an efficient setup for physical scale models of pressurized sand traps and a methodology that combines the benefits of 3D CFD simulations with physical scale models testing for sand trap engineering and design. [ABSTRACT FROM AUTHOR]