Various Types Of Accelerators Research Articles

Influence of accelerators and curing system composition on the cure characteristics, crosslinks structure and properties of acrylonitrile‐butadiene elastomer

AbstractThe goal of this work is to study the influence of the type of vulcanization accelerator and the quantitative composition of the curing system on the cure characteristics, morphology of elastomer network, crosslink density and physico‐chemical properties of acrylonitrile‐butadiene rubber (NBR) composites. Sulfur curing systems are investigated, which consist of various types of accelerators, that is, sulfenamide, guanidine and thiuram, applied in various proportions to sulfur. The type of accelerator and the sulfur/accelerator ratio significantly affect both the cure rate and the structure and number of crosslinks resulting from the vulcanization. The highest cure rate and the lowest content of polysulfidic crosslinks are exhibited by rubber composites with efficient (EV) curing systems due to the highest content of accelerators compared to semi‐efficient (SEV) and conventional (CV) systems. The structure of crosslinks strongly affect tensile properties and hardness of the vulcanizates as well as their solvent resistance, thermal stability and resistance to thermo‐oxidative aging.

Optimal scheme for stimulating photofission of shielded nuclear materials on the Microtron M-30: a combination of theoretical and experimental studies

Relevance. The photofission of shielded nuclear materials is widely used to develop methods for non-destructive analysis of their isotopic composition. To stimulate the photofission reaction, bremsstrahlung beams obtained on electronic accelerators are used. Their parameters significantly depend on the design features of accelerators and sample activation schemes. Purpose. Theoretical modelling of parameters of an optimal scheme for stimulating the photofission of shielded nuclear materials on an electronic accelerator – Microtron M-30 for the analysis of their isotopic composition, considering its technical characteristics, and experimental verification of its parameters. Methodology. Theoretical calculations of the parameters of bremsstrahlung beams for the Microtron M-30 were carried out using the GEANT4 toolkit. For experimental studies of the influence of structural elements of the optimal stimulation scheme on the integral characteristics of inhibitory photons, secondary photoneutrons, the method of activation of detectors made of gold was used; for residual electrons – the transmission method based on a passage chamber and a Faraday cylinder. Results. As a result of the combination of theoretical and experimental studies, optimal parameters of the activation scheme of nuclear materials on the Microtron M-30 have been established. The scheme provides experimental conditions under which the losses of bremsstrahlung photon beams interacting with the test samples (with energies ≥6 MeV) do not exceed 35% of their initial values, with the practical absence of residual electrons (98% of electrons are absorbed) and secondary photoneutrons (no more than 1E-9 n/e). Conclusions. The parameters of the developed stimulation scheme for the Microtron M-30 can be applied to various types of accelerators, considering their design features, characteristics of the samples, and implemented activation schemes

Status and outlook: Research and development on the neutron source for BNCT

<p indent=0mm>Boron neutron capture therapy (BNCT) is regarded as a revolutionary means for high-accuracy cancer therapy with cell level selectivity. It has unique therapeutic effects for some malignance, such as glioblastoma multiforme, melanoma, recurrent head and neck malignance. It can also be used for cancer treatment of deep organ, such as liver and lung. Even though its principle was proposed about <sc>80 years</sc> ago, it has never been utilized in routine clinic therapy in hospital until 2020. BNCT, as a binary therapeutic method, greatly depends on both high-quality neutron beam and highly target-selective boron drug. Tumor killing in cell-level accuracy can be achieved only when the two elements work together and collaborate closely. To realize such therapeutic effect, BNCT sets high requirement on both neutron source and boron drug. The research on boron drug is related with multi-disciplines, such as chemistry, biology, medicine, radiology, pharmacy and physics. This article focuses on the neutron source for BNCT. Commonly, there are two types of BNCT neutron sources: reactor-based neutron source and accelerator-based neutron source. Up to now, almost all clinic trails of BNCT therapy were performed with the former. Due to limited resources of reactor neutron source, only less than 2000 cases BNCT treatments have been carried out in the world since BNCT method was invented. Thanks for the intense beam proton accelerator development, accelerator based neutron source can provide better beam quality, and especially importantly it can be installed in a hospital environment, which is essential for wide-range application of BNCT. In accelerator-based BNCT field, China has a sound base owing to more than <sc>20 years</sc> research and development in high intensity neutron source for spallation neutron source and accelerator-driven subcritical system. It is meaningful work to transfer the related technology to accelerator-based BNCT (AB-BNCT). In this paper we will firstly introduce the demand on neutron beam specification recommended by IAEA. Then the difficulties in BNCT slow development in passing decades are reviewed. New era of BNCT is coming and one can expect a prosperous future, owing to accelerator-based BNCT. The core technology of AB-BNCT is explored and recent research achievements on BNCT research and development in China are reported. Various types of accelerators now can be used for BNCT facility, including electro-static high voltage, cyclotron and RF linac. Their pro and con are reviewed. Majorly two kinds of neutron generation targets are utilized for BNCT, and the characteristics comparison of these two are analyzed. On the newly constructed BNCT research platform in China, new boron drug research and development work are conducted in many institutes, universities and pharmacy companies. And in recent, a new AB-BNCT facility is under construction for clinic trails in a hospital. So we can have an optimistic viewpoint for BNCT future in China.

Molecular-Dynamics Simulation of the Interaction Processes of Pulsed Ion Beams with Metals

The molecular-dynamics method is used to model the interaction processes of pulsed ion beams with metal targets. The main parameters of a pulsed ion beam interacting with a target are the ion energy, pulse duration, and charge density per unit area of the target. Using averaged values of these parameters of ion beams published for various types of accelerators, a numerical study of the dependence of the dynamics of thermal and structural processes in irradiated targets upon a change in the size and heterogeneity of the structure is performed. Simulation of the irradiation processes and estimates of the distribution of beam ions in the volume are carried out in the range of beam ion energies of 1–2 keV using the concept of a shock wave. The results are important for developing the model of a pulsed ion beam and classifying the types of structural changes in the irradiated material depending on the model parameters.

Future Prospects for Particle Therapy Accelerators

Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators.This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy.The following procedure is pursued to perform a comparison between various types of accelerators:(1)The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations.(2)The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified.(3)A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion.(4)Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.

Portable Solution for Modeling Compressible Flows on All Existing Hybrid Supercomputers

A variant of a numerical algorithm for simulating viscous gasdynamic flows on unstructured hybrid grids and its software implementation for heterogeneous computations is described. The system of Navier–Stokes equations is approximated by the finite-volume method of an increased approximation order with the values of the variables being defined at the mass centers of the grid elements. The distributed software implementation of the numerical algorithm is adapted to running on hybrid computer systems of various architectures. Comparative implementations were created using the MPI, OpenMP, CUDA, and OpenCL software models permitting the use of multicore processors and various types of accelerators, including NVIDIA and AMD graphics processors, and Intel Xeon Phi multicore coprocessors. The data exchange between MPI processes and between processors and accelerators is carried out simultaneously with the execution of calculations (both in MPI + OpenMP mode and when using CUDA or OpenCL). The indicators of parallel efficiency and performance on systems with different types of computing devices are studied in detail. In the tests, up to 260 GPUs were successfully used.

Methods and means of accelerating particles of natural and technogenic origin

Various types of accelerators of solid particulates of natural and technogenic origin are analyzed in the paper. We consider the structure and principles of operation of micron- and millimeter-scale accelerators with the center of velocity distribution of about 20 km/s: electrostatic, electromagnetic, pulsed, rail electromagnetic, solenoid coil and electric-gas dynamics, combined installations. Light-gas, explosive, gas discharge and electromagnetic accelerators with different principles of action are reviewed. The focus is on the electromagnetic techniques of acceleration that are most promising for acceleration of macrobodies to supervelocities. The advantages and disadvantages of different types of accelerators of solids are pointed out. The usability of different designs of accelerators to simulate collisions of orbital meteorite particles and space debris with the surface of the spacecraft is analyzed. Problems emerging in the construction and operation of accelerators of various types are specified and solutions to these problems are presented. The results of experiments in the acceleration of solid micron- and millimeter-wave solids using accelerators of various types and methods of structural optimization of particle accelerators with a view to increasing their efficiency and the speed of the accelerated body are presented. The evolution of accelerators and the main directions of their further improvement are shown.

Electron Beam Modified Organic Materials and their Applications

The interaction of electron-beam with organic materials (e.g. Polymers, organic solvents, organic acids etc.) is known to modify their physico-chemical properties and, in many cases, these electron-beam modified materials are used for variety of societal applications. In this review article, we first describe the various types of accelerators to generate electron-beams of different energies, i.e. low (0.3 – 0.75 MeV), medium (0.75– 5 MeV) and high (5 – 10 MeV) energies, and emphasis is laid on various accelerators developed by Bhabha Atomic Research Center (BARC), Trombay, India. The energetic electrons on interaction with organic materials create free radicals that lead to modifications in material through various mechanisms such as, cross-linking, scissioning, curing and grafting. An overview of these mechanisms is presented by citing appropriate examples. Applications of electron beam-modified organic materials in different areas including bio-medical, textile, environment protection, electrical, radiation dosimetry, etc. are reviewed. The prospects and challenges involved in the electron-beam processing of organic materials are presented.

Radiation Effects in Nuclear Ceramics

Due to outstanding physicochemical properties, ceramics are key engineering materials in many industrial domains. The evaluation of the damage created in ceramics employed in radiative media is a challenging problem for electronic, space, and nuclear industries. In this latter field, ceramics can be used as immobilization forms for radioactive wastes, inert fuel matrices for actinide transmutation, cladding materials for gas-cooled fission reactors, and structural components for fusion reactors. Information on the radiation stability of nuclear materials may be obtained by simulating the different types of interactions involved during the slowing down of energetic particles with ion beams delivered by various types of accelerators. This paper presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on recent results concerning the damage accumulation processes. Energetic ions in the KeV-GeV range are used to explore the nuclear collision (at low energy) and electronic excitation (at high energy) regimes. The recovery by electronic excitation of the damage created by ballistic collisions (SHIBIEC process) is also addressed.

A High-Performance Heterogeneous Computing Platform for Biological Sequence Analysis

Advances in bioinformatics research continue to add complexity to the analyses and interpretation of biological data. Certain sequence database searches may take weeks to complete due to complicated data dependencies by dynamic programming. A reconfigurable coprocessor can remove this computational bottleneck and accelerate the operation. This paper presents a heterogeneous computing platform through Message Passing Interface (MPI) enabled enterprise computing infrastructure for high-throughput biological sequence analysis. The computing platform integrates heterogeneous computer architectures including conventional processors with Streaming Single Instruction Multiple Data Extensions 2 (SSE2) instructions, reconfigurable coprocessors, and legacy processors together into one system, and allows each to perform the task to which it is best suited. With appropriate computation and communication scheduling, the integrated heterogeneous computing infrastructure is designed to accommodate various types of accelerators to provide a High-Performance Computing (HPC) framework to support the most widely used life science applications.

A (CERN) History of Accelerator Shielding

From the early days, accelerator shielding and radiation protection in general have been influenced by the increasing knowledge of the health effects of ionizing radiation, which has progressively decreased the dose rates allowed in occupied areas. At the same time the tools available for estimating shielding have benefited from increasing computing power. Nonetheless, the simplified models of the early days are often still useful for a first estimate before going into complex and detailed Monte Carlo simulations.This paper provides a brief historical overview of accelerator shielding. As the subject is vast, it is restricted to a review of the various phases of accelerator shielding studies at CERN. CERN is a good example as its accelerators and the related shielding problems span 50 yr of history and cover all major aspects that can be encountered in accelerator radiation protection: various types of accelerators with a wide range of beam intensities producing many varieties of accelerated and secondary particles with energies from MeV to TeV.

Beam halo formation in high-intensity beams

Studies of beam halo became an unavoidable feature of high-intensity machines where uncontrolled beam loss should be kept to extremely small level. For a well-controlled stable beam such a loss is typically associated with the low-density halo surrounding beam core. In order to minimize uncontrolled beam loss or improve performance of an accelerator, it is very important to understand what are the sources of halo formation in a specific machine of interest. The dominant mechanisms are, in fact, different in linear accelerators, circular machines or energy recovering linacs (ERL). In this paper, we summarize basic mechanisms of halo formation in high-intensity beams and discuss their application to various types of accelerators of interest, such as linacs, rings and ERL.

Ultra-high-speed deformation by impact of a projectile flying at speeds on the order of km s −1

An apparatus was developed to facilitate application of an electro-thermo-chemical accelerator to high-speed deformation experiments. The apparatus is designed on the principle of sequential collision of elastic bodies. Speeds ranging from 600 to 780 m s −1 were achieved, and estimated strain rate of deformation is 10 7 s −1. The newly developed apparatus can be applied to various types of accelerators for attaining deformation speeds as high as several km s −1. Transmission electron microscopy of aluminum deformed at high speed by use of the apparatus revealed the formation of very small stacking fault tetrahedra (SFTs). This observation is quite new for aluminum; previously, SFTs had not been observed in aluminum, although deformation had been carried out at strain rates lower than 10 6 s −1. Use of the apparatus promises to provide new insight into high-speed deformation.

Special radiation protection aspects of medical accelerators.

Radiation protection aspects relevant to medical accelerators are discussed. An overview is first given of general safety requirements. Next, shielding and labyrinth design are discussed in some detail for the various types of accelerators, devoting more attention to hadron machines as they are far less conventional than electron linear accelerators. Some specific aspects related to patient protection are also addressed. Finally, induced radioactivity in accelerator components and shielding walls is briefly discussed. Three classes of machines are considered: (1) medical electron linacs for 'conventional' radiation therapy, (2) low energy cyclotrons for production of radionuclides mainly for medical diagnostics and (3) medium energy cyclotrons and synchrotrons for advanced radiation therapy with protons or light ion beams (hadron therapy).

Change of network structure of natural rubber vulcanizate with thermal aging

The effect of sulfur accelerators during the curing process in natural rubber (NR) was investigated. The samples were prepared by adding the same fraction of various types of accelerators in the compound and all samples were cured at the same temperature but for two different times. Determination of the molecular massbeween crosslinks immediately after vulcanization shows the crosslink density in the samples, which differs for different accelerators. After that, the same samples undergo thermal aging and the changes of the crosslink dinsity were studied. During the first period of thermal aging, additional crosslink were observed and then a period of deterioration of the network structure is following. From the obtained relults of the molecular mass between crosscan be drawn about the most suitable accelerator for use in certain conditions and applications. To predict the behavior of vulcanizates under various effects as heat and radiation, it is important to know more about the chemical structure of the network. The changes of crosslink density in the investigated samples were followed by eqiomobrium swelling and by mechanical measurements. IR spectroscopy was used to study the changes of the crosslink bridges. The influence of aging time on the maximum tensile strength, for NR vulcanizates cured 5 min.