Particle Transport System Research Articles

Simulating the head of a TrueBeam linear particle accelerator and calculating the photoneutron spectrum on the central axis of a 10-MV photon using particle and heavy-ion transport system code.

Photon energy is higher than the (γ,n) threshold, allowing it to interact with the nuclei of materials with high z properties and liberate fast neutrons. This represents a potentially harmful source of radiation for humans and the environment. This study validated the Monte Carlo simulation, using the particle and heavy-ion transport code system (PHITS) on a TrueBeam 10-MV linear particle accelerator's head shielding model and then used this PHITS code to simulate a photo-neutron spectrum for the transport of the beam. The results showed that, when comparing the simulated to measured PDD and crosslines, 100% of the γ-indexes were<1 (γ3%/3mm) for both simulations, for both phase-space data source and a mono energy source. Neutron spectra were recorded in all parts of the TrueBeam's head, as well as photon neutron spectra at three points on the beamline.

Radiation levels outside a patient undergoing 177Lu-PSMA radioligand therapy

Understanding the spatial distribution of radiation levels outside of a patient undergoing 177Lu radioligand therapy is not only helpful for conducting correct tests for patient release, but also useful for estimation of its potential exposure to healthcare workers, caregivers, family members, and the general public. In this study, by mimicking the 177Lu-labeled prostate-specific membrane antigen radioligand therapy for prostate cancers in an adult male, the spatial distribution of radiation levels outside of the phantom was simulated based on the Monte Carlo software of Particle and Heavy Ion Transport System, and verified by a series of measurements. Moreover, the normalized dose rates were further formulized on the three transverse planes representing the heights of pelvis, abdomen and chest. The results showed that the distributions of radiation levels were quite complex. Multi-directional and multi-height measurements are needed to ensure the external dose rate to meet the release criteria. In general, the radiation level was higher at the horizontal plane where the source was located, and the levels in front and behind of the body were higher than those of the left and right sides at the same height. The ratio of simulated dose rates to measured ones ranged from 0.82 to 1.19 within 1 m away from the body surface in all directions. Based on the established functions, the relative root mean square deviation between the calculated and simulated values were 0.21, 0.25 and 0.23 within a radius of 1 m on the pelvis, abdomen and chest transverse planes, respectively. It is expected that the results of this study would be helpful for guiding the test of extracorporeal radiation to determine the patient’s release, and of benefit to estimate the radiation exposure to others.

Techno-Economic Analysis of Candidate Oxide Materials for Thermochemical Storage in Concentrating Solar Power Systems

The thermal storage capability is an important asset of state-of-the-art concentrating solar power plants. The use of thermochemical materials, such as redox oxides, for hybrid sensible/thermochemical storage in solar power plants offers the potential for higher specific volume and mass storage capacity and as a consequence reduced levelized cost of electricity making such plants more competitive. For the techno-economic system analysis, three candidate redox materials were analyzed for their cost reduction potential: cobalt-based, manganese–iron–based, and perovskite-based oxide materials. As a reference process the use of inert commercial bauxite particles (sensible-only storage) was considered. A solar thermal power plant with a nominal power of 125 MWe and a storage capacity of 12 h was assumed for the analysis. For each storage material a plant layout was made, taking the specific thermophysical properties of the material into account. Based on this layout a particle break-even cost for the specific material was determined, at which levelized cost of electricity parity is achieved with the reference system. Cost factors mainly influenced by the material selection are storage cost and steam generator cost. The particle transport system cost has only a minor impact. The results show differences in the characteristics of the materials, for example, regarding the impact on storage size and cost and the steam generator cost. Regarding the economic potential of the candidate redox materials, the perovskite-based particles promise to have advantages, as they might be produced from inexpensive raw materials.

Microfluidic Synthesis of Liquid Crystalline Elastomer Particle Transport Systems which Can Be Remote‐Controlled Magnetically

AbstractHere, the microfluidic synthesis of liquid crystalline elastomer (LCE) particles, which can be remote‐controlled magnetically and used as transport systems, is presented for the first time. Ferri‐magnetic, rod‐shaped Fe3O4nanoparticles are functionalized with poly(methyl methacrylate) to make them compatible with organic LCE precursor compounds. Their influence on the LCE precursor alignment is studied and thermoresponsive as well as photoresponsive LCE microparticles containing 0–6 wt% Fe3O4are synthesized with a microfluidic device. Thermal and photochemical actuations of these particles are investigated. Their magnetic addressability is studied with a recently developed magnetic setup, by which the particles can be guided on liquid surfaces in the centimeter range–but with a precision in the submillimeter range. This allows the performance of reversible light‐ or heat‐controlled actuations at desired positions. The potential of synthesized LCE particles as transport systems is demonstrated by the transport of plastic, textiles or copper, which can be pushed just due to magnetic forces or transported in general by taking advantage of the phase dependent “stickiness” of LCEs. These studies open doors to novel applications of LCEs as microrobots using magnetism as a control.

Pre-discard estimation of radioactivated materials in positron emission tomography cyclotron systems and concrete walls of a cyclotron vault.

The concrete vault, cyclotron body, and peripheral equipment in a cyclotron room become radioactivated by neutrons generated by operating an unshielded cyclotron. Radionuclides and the amounts of radioactivated materials must be identified before discarding a cyclotron system. The present study aimed to reduce the amounts of concrete from cyclotron vaults, as well as cyclotron components and peripheral equipment, that will be disposed of as radioactivated waste by clarifying the nature and quantity of radioactivated materials remaining in facilities after cyclotron operations have ceased. Cylindrical concrete cores were bored into all four walls, ceiling, and floor of a room where a Cypris 370 cyclotron had been operated for 22.8yr and then cooled for 40months. The accelerated particles comprised protons and deuterons with constant energy of 18 and 10MeV, respectively. The types and amounts of radionuclides in these cores, in 38 components of the cyclotron including the yoke, and in 13 pieces of equipment in the room, were determined by γ-ray spectrometry. Concentrations of radioactivity were also calculated using an updated version of Particle and Heavy Ion Transport System and DCHAIN-SP. Amounts of materials with both measured and calculated total radioactivity concentration (ΣD) of <0.1Bq/g were identified as being nonradioactivated. The major radionuclides in the concrete were 60 Co and 152 Eu. The radioactivated concrete was distributed to a depth of <38cm. Most cyclotron components and equipment were radioactivated by neutrons. The major radionuclides in cyclotron components and equipment were 54 Mn, 60 Co, and 65 Zn. A 33% volume of the yoke was regarded as nonradioactivated. The estimated amount of radioactivated waste in the concrete was about 70,000kg (12.5% of the total concrete). Most components of the cyclotron except for the 33% volume of the yoke (20% of the cyclotron body), as well as most peripheral equipment in the room, were radioactivated. Part-by-part assessments of radioactive materials using measurements and calculations could distinguish nonradioactive from radioactive materials before they are discarded.

Formulation, Pretreatment, and Densification Options to Improve Biomass Specifications for Co-Firing High Percentages with Coal

There is a growing interest internationally to use more biomass for power generation, given the potential for significant environmental benefits and long-term fuel sustainability. However, the use of biomass alone for power generation is subject to serious challenges, such as feedstock supply reliability, quality, and stability, as well as comparative cost, except in situations in which biomass is locally sourced. In most countries, only a limited biomass supply infrastructure exists. Alternatively, co-firing biomass along with coal offers several advantages; these include reducing challenges related to biomass quality, buffering the system against insufficient feedstock quantity, and mitigating the costs of adapting existing coal power plants to feed biomass exclusively. There are some technical constraints, such as low heating values, low bulk density, and grindability or size-reduction challenges, as well as higher moisture, volatiles, and ash content, which limit the co-firing ratios in direct and indirect co-firing. To achieve successful co-firing of biomass with coal, biomass feedstock specifications must be established to direct pretreatment options in order to modify biomass materials into a format that is more compatible with coal co-firing. The impacts on particle transport systems, flame stability, pollutant formation, and boiler-tube fouling/corrosion must also be minimized by setting feedstock specifications, which may include developing new feedstock composition by formulation or blending. Some of the issues, like feeding, co-milling, and fouling, can be overcome by pretreatment methods including washing/leaching, steam explosion, hydrothermal carbonization, and torrefaction, and densification methods such as pelletizing and briquetting. Integrating formulation, pretreatment, and densification will help to overcome issues related to physical and chemical composition, storage, and logistics to successfully co-fire higher percentages of biomass (>40%) with coal.

Pump-free transport of magnetic particles in microfluidic channels

The use of magnetic particles in microfluidic devices offers new possibilities and a new degree of freedom to sequential synthesis and preparative or analytical procedures in very small volumes. In contrast to most of the traditional approaches where the liquid phase is flushed or pumped along a solid phase, the transport of magnetic particles through a microfluidic channel has the advantage of reduced reagent consumption and simpler, smaller systems. By lining up different reservoirs along the transport direction, reactions with different agents can be accomplished. Here, we present a pump and valve-free microfluidic particle transport system. By creating a simple and very effective layout of soft magnetic structures, which concentrate an external homogeneous magnetic field, a passive, thus easy to operate structure was generated. Most importantly, this layout is based on a simple tube by which fluidic and magnetic parts are separated. The tube itself is disposable and can be replaced prior to vital reactions, thus helping reduce sample cross-contaminations without affecting the particle transport properties. The layout of the device was thoroughly examined by a computer simulation of the particle trajectories, and the results were confirmed by experiments on a micro-machined demonstrator, which revealed an effective transport speed of up to 5 mm/s in 30 mT magnetic fields. Thus, we present a microfluidic transport device that combines the advantages of magnetic particles in microfluidic systems with a simple single-use technology for, e.g., bioanalytical purposes.

The effects of realistic pancake solenoids on particle transport

Solenoids are widely used to transport or focus particle beams. Usually, they are assumed as being ideal solenoids with a high axial-symmetry magnetic field. Using the Vector Fields Opera program, we modeled asymmetrical solenoids with realistic geometry defects, caused by finite conductor and current jumpers. Their multipole magnetic components were analyzed with the Fourier fit method; we present some possible optimized methods for them. We also discuss the effects of “realistic” solenoids on low energy particle transport. The findings in this paper may be applicable to the lower energy particle transport system design.

Electrostatic Transport of Lunar Soil for In Situ Resource Utilization

To realize a long-term lunar exploration, it is essential to develop a technology for transporting lunar soil for in situ resource utilization. We are developing a particle transport system that utilizes electrostatic traveling waves. The conveyer consists of parallel electrodes printed on a plastic substrate. Four-phase rectangular voltage is applied to the electrodes to transport particles on the conveyer. Mechanical vibration was applied to the conveyer to transport particles more efficiently. The results of our investigation are as follows: (1) The observed transport rate in air was 13.5 g/min for a conveyer with a width of 100 mm. By performing numerical calculations on the basis of the 3D distinct element method, we predicted that the system performance would improve in the high-vacuum and low-gravity environment on the moon. (2) Power consumption in this system is much less. It was only 10 W for a conveyer with an area of 1.0 m2 . (3) We demonstrated an inclined and curved transport path as well ...

Third order transfer matrices for real Wien filters with homogeneous main fields

The determination of the ion optical aberrations of the Wien filters operated independently or in more complex mass analyzing or charged particle transport systems needs the calculation of the trajectories in a third order approximation. The trajectory calculations for crossed electric and magnetic fields generate unmanageably long formulas for the matrix elements. The reduction of the extent of the matrix elements to usable size can be reached by restricting calculations to less complex configurations as the homogeneous main fields Wien filters, which are probably the most often used crossed field velocity filters. Analytic expressions for transfer matrix elements for homogeneous main fields Wien filters were determined up to third order accuracy level. The elements of three pairs of matrices, those of entry fringing fields, those of the main fields and those of the exit fringing fields were derived for the plane of mass dispersion (radial) and for a direction normal to it (axial). The third order accuracy was kept over all the calculated contributions to the ion trajectory. The first order elements, to be multiplied by first order small quantities were calculated in a second order approximation, those of second order with a first order accuracy, while those of third order were not allowed to contain small quantities in their expressions. The matrix elements describing the ion position, trajectory slope, ion energy and mass were accounted for. In the fringing field matrix elements the effect of the electric and magnetic field boundary curvature radii were included. In a brief application, on one spectrometer geometry, the calculated matrices were used to determine the effect of third order angular aberration generated by the Wien filter alone on the resolution when the second order aberration has been cancelled.

Application of Liquid Solid Semi-moving Bed to Fractionation of Cesium Ion in Wastewater

A liquid solid semi-moving bed with non-mechanical particle transport system is proposed and used for fractionation of cesium ion in wastewater. The particle transport system, which consists of a suction chamber, a mixing chamber, a nozzle and a riser tube, is designed to be controlled completely by hydraulic force. Experiments show that continuous feeding and discharging of resin can be realized by the transport system. The removal of cesium ion from wastewater is realized. The concentration of cesium ion in effluent liquid remains below 0.1g · L −1 (the initial concentration is 5.3g · L −1) during the 73 hours' experiment. The average exchange capacity of resin discharged from the bed is 0.57 mmol · (g dry resin) −1, which is close to the saturated capacity of 0.65 mmol · g −1. And it is also proved that the non-homogeneity of particle vertical velocity along the radial direction can seriously influence the ion-exchange process.

Analysis of pulsating electric signals generated in gas–solids pipe flow

In gas–solids pipe flow, particles are electrostatically charged as a result of repeated impacts on the inner walls. When a section of the pipe made of metal is electrically isolated and the charge leakage to the ground is monitored, pulsating electric signals are detected. In the present work, these signals have been studied both experimentally and theoretically. Micrometer-sized alumina particles were dispersed through an ejector and continuously transported in dilute phase. The pipes used were 6 mm in inner diameter, and a pre-charging pipe and detection pipes were installed in the particle transport system. The pulsating electric signals were found to vary in a wide range from positive to negative. The variation of the electric signals was attributed to two electrostatic phenomena (i) the induced current caused by the transport of a cloud of charged particles and (ii) the particle charging caused by repeated impacts on the inner wall. Based on analyses of these phenomena, the total charge, transferred charge, and particle concentration of the cloud can be evaluated. Furthermore, the average velocity of the cloud flowing in the pipe can be obtained from the time interval between peak signals measured with a detection pipe or using a two-detection pipe system based on the correlation method.

Study on the stress distribution and modeling of the stand pipe in a circulating moving bed

The liquid–solid circulating moving bed reactor is a novel one, which consists of two reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through a coupling standpipe and to the particle transport system through a bottom standpipe, and are then conveyed into the upper reaction chamber through a riser. A stress distribution model based on the equations of continuity and momentum balance in the reactor is established and used for simulations which shows that the stress concentration regions are at the coupling standpipe and the bottom of the regeneration chamber. To reduce the largest stress in the stress concentration regions and to minimize catalyst consumption, the regeneration chamber should be designed to give a low ratio of height to diameter. Zoning diagrams of the flow patterns in the bottom standpipe are proposed and the flow patterns can be readily deduced from the pressure gradient.

Operation characteristics of a new liquid-solid circulating moving bed reactor

The liquid-solid circulating moving bed reactor is a novel one, which consists of two or more reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through an upper conduit and to the particle transport system through a lower conduit, and then are conveyed into the upper reaction chamber through a riser. The circulating rate of particles and the flow of liquid in the two conduits are key factors to the continuous steady operation of the reactor; they can be controlled by varying operating conditions: the outlet liquid flow rate in the regeneration chamber, the outlet liquid flow rate in the reaction chamber, the inlet liquid flow rate of the reactants, and the flow rate of driving flow. A flow model has been proposed to quantify the operation characteristics of the reactor. The results predicted by the model show satisfactory agreement with the experimental data.

Force collision and next event estimation of pulse height tallies

Pulse height cannot be easily tallied with commonly used analog transport methods when the recording cells are much smaller than the whole particle transport system. This paper presents a new transport scheme and applies it to a simple modeling problem of an industrial CT. The results show that for an important class of problems, FC-NEE is much more efficient than geometry splitting with Russian roulette, DXTRAN or conventional analog transport methods. The new method has been tested on an MCNP benchmark.

Particle transport by jet pump in a new liquid–solid circulating moving bed reactor

The liquid–solid circulating moving bed reactor is a novel one, which consists of two or more reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through an upper conduit and to the particle transport system through a lower conduit, and then are conveyed into the upper reaction chamber through a riser. The renewing speed of particles in the reaction chamber is determined by the circulating rate of particles, which is one of the key factors in the operation of the reactor. Three different kinds of auxiliary liquids are used to regulate the circulating rate of particles, and a suitable configuration of particle transport system is established. A model of particle transport based on mass, momentum and energy balance is proposed and used for simulation of the process.

Numerical Modeling of Space-Charge-Limited Charged-Particle Emission on a Conformal Triangular Mesh

Orbit tracing is a numerical technique to design high-current charged particle guns and transport systems. Although most available programs use the finite-difference approach to calculate electric fields, the finite-element method has advantages for accuracy and versatility. This paper describes an effective algorithm to model space-charge-limited emission and a procedure to apply it to variable-resolution conformal triangular meshes with multiple emission regions. Improved tabulations of space-charge solutions for sharply curved emission surfaces are given. In a benchmark Pierce diode simulation, the procedure gives an absolute current prediction within 0.2% of the analytic value and particle orbits within 0.1° of the predicted exit angle.

In situ ultra-high vacuum transmission electron microscopy studies of nanocrystalline copper

We have built a particle production and transport system that allows the characterization of nanocrystals without exposure to contaminating atmospheres such as air. Nanocrystals (formed by inert gas condensation of a sputtered atom population) are transported in situ via the gas phase to an ultra-high vacuum transmission electron microscope (UHVTEM) equipped with a heating stage and gas exposure system. With this system, we can study various nanoparticle phenomena in real time and under clean conditions. In this paper we discuss the experimental design and preliminary studies using imaging and diffraction techniques. These include, the time-evolution of copper nanoparticle morphology and sintering behavior as a function of particle size, temperature, oxygen/atmosphere exposure and supporting substrate. In particular, we have observed immediate room temperature sintering of clean copper nanocrystals which does not occur with nanoparticles that have been exposed to oxygen. Furthermore, we have seen an interaction between copper nanocrystals and amorphous carbon which produces graphite shells. This shell formation process suggests a solid state analog to that seen when nanoparticles catalyze the growth of carbon fibers through a hydrocarbon atmosphere decomposition.

POP — an interactive charged particle transport system design tool

POP calculates the paths of moving charged particles through particle accelerators, analysers and focussing devices over suitable ranges of geometric and kinematic phase space such as those found emanating from ion sources or reaction spots on samples or targets in many types of experimental measurements. Within the limits of a lumped system, POP calculates a small group of such trajectories using chromatically accurate matrix techniques which are truncated to 2nd-order geometrically. The trajectories and a schematic representation of the system are displayed at a graphics terminal and can be usefully printed on a variety of devices. Parameters can be edited interactively. The design can be saved at any stage to a named file in a format which can be reused later. The format can be used by other software.

Removal of nonlinear effects in deflecting magnets

This paper presents the analysis of the influence of second-order terms in the magnetic field expansion upon the motion of charged particles in deflecting magnets. It has been indicated that at large values of the field-index n nonlinear effects at exit angles result in essential corrections which should be taken into account in the calculations of particle transport systems. The dependence has been found of the magnetic field upon the radius, which will make it possible to minimize nonlinear eflects for most of the cases taking place in practice.