High-energy Field Research Articles

Ultrasonic Intensification of Low-Temperature Plasma Synthesis of Ceramic-Like Coatings of Valve Metals

The authors have presented a method of ultrasonic intensification of anode–cathode interactions during the formation, in water–alkali electrolytes, of ceramic-like coatings on the surface of valve metals in the process of low-temperature plasma synthesis. An algorithm of directional influence of high-energy fields on the distinctive features and rate of chemical reactions at the electrolyte–metal–coating interface through changing the solution’s state by ultrasonic pulses in the process of anodic microarc oxidation has been developed. The authors have elucidated the mechanism and have determined the character and level of effect of the proposed intensification on the dynamics of growth of a coating under low-temperature-plasma conditions of a liquid medium. It has been shown that mechanical (ultrasonic) activation of the electrolyte is responsible for the intensification of the process of transfer of charge carriers, which are primarily electrolyte ions. Procedures and equipment have been described using which the values of an ultrasonic signal formed under various conditions were recorded. The nature of more intense buildup in the thickness of a ceramic-like coating with reduced energy expenditure to form it has been elucidated. This is explained by the appearance in the electrolyte, during its ultrasonic activation, of the great number of high-frequency damped oscillations of irregular waveform with a high amplitude as far as the current is concerned (5 A or higher), which is attributable to the occurrence of a synergetic effect.

Stress, strain and electromechanical analyses of (RE)Ba2Cu3Ox conductors using three-dimensional/two-dimensional mixed-dimensional modeling: fabrication, cooling and tensile behavior

High temperature superconducting (HTS) conductors, represented by Rare Earth-Barium-Copper-Oxide (REBCO) conductors, are promising for high energy and high field superconducting applications. In practical applications, however, the HTS conductors experience different stresses and strains, including residual stresses due to thermal mismatch and tensile stresses due to Lorentz forces, resulting in some circumstances to a reduction in the load-carrying capacity as well as the risk of degradation in conductor critical current. In this study a mixed-dimensional high-aspect-ratio laminated composite finite element model for REBCO conductor is developed for stress and strain analyses in the processes of fabricating and cooling, as well as tensile testing. The model includes all the major constituent layers of a typical REBCO conductor and is experimentally validated. First, the thermal residual stresses and strains accumulated during the fabrication and cooling processes are analyzed by a multi-step modeling method that emulates the manufacturing process. Then, with the residual stresses and strains as initial stresses and strains, the mechanical behavior under a tensile load is studied. Lastly, a phenomenological critical current-strain model based on the Ekin power-law formula and the Weibull distribution function is combined with the mixed-dimensional conductor model to predict the strain dependence behavior of critical current in the reversible and irreversible degradation strain ranges. Simulation results show that the multi-step modeling is an effective method for stress and strain analyses of REBCO conductors during the fabrication and cooling processes and under and tensile loads. Compressive thermal residual stress generated on the REBCO layer during fabrication and cooling strongly affects the subsequent mechanical and current-carrying properties. Stress–strain curves generated by tensile loads are analyzed and experimentally validated at both the conductor and constituent-layer levels. Simulation results for the strain dependence of critical current are in good agreement with experiment data in both the reversible and irreversible degradation stages.

Multi-octave, CEP-stable source for high-energy field synthesis.

The development of high-energy, high-power, multi-octave light transients is currently the subject of intense research driven by emerging applications in attosecond spectroscopy and coherent control. We report on a phase-stable, multi-octave source based on a Yb:YAG amplifier for light transient generation. We demonstrate the amplification of a two-octave spectrum to 25 μJ of energy in two broadband amplification channels and their temporal compression to 6 and 18 fs at 1 and 2 μm, respectively. In this scheme, due to the intrinsic temporal synchronization between the pump and seed pulses, the temporal jitter is restricted to long-term drift. We show that the intrinsic stability of the synthesizer allows subcycle detection of an electric field at 0.15 PHz. The complex electric field of the 0.15-PHz pulses and their free induction decay after interaction with water molecules are resolved by electro-optic sampling over 2 ps. The scheme is scalable in peak and average power.

Design and Implementation of Digital Control System Based on PAC Architecture for Large-Capacity Pulse Power Supply

In Tokamak device, many larger capacity pulsed power supplies have been installed to provide high-energy magnetic field to control plasma. In this article, a new digital control system for satisfying larger capacity pulse power supply is introduced. This control scheme uses programmable automation controller (PAC) architecture, which consists of software platform and hardware platform to design a new digital control system, and in this system, real-time operation system (OS) and real-time communication network can provide much more precise and predictable timing characteristics to fulfill the requirements of the real-time control for pulse power supply in Tokamak device. Its hardware architecture based on integration and modularization can provide reliability, stability, and flexibility for digital control application; meanwhile, its software platform is used to handle data communication, close-looping control, protection strategy execution, and trigger output. After the digital control system of the large-capacity pulse power supply is built, its performance is verified through the HL-2A experiments. The result shows that the digital control system achieves the design goals and has high reliability and stability.

Numerical investigation on decreasing radial stress in epoxy impregnated REBCO pancake coils by overband

Rare-earth-barium-copper-oxide (REBCO) coated conductors are promising conductors for high energy and high field superconducting applications. In the case of epoxy impregnated REBCO superconducting pancake coils, however, excessive radial tensile stress generated in the winding when the coils are cooled from room temperature to 77 K or less can cause delamination, resulting in irreversibly degradation in the coils. To ensure the stable operation of superconducting coils, it is important to decrease radial tensile stress in epoxy impregnated REBCO pancake coils. In this study, the fabrication method of overband radial build in epoxy impregnated REBCO pancake coils is presented and numerically analyzed. A two-dimensional axisymmetric finite element model (FEM) with the equivalent homogeneous coil properties is built and validated to analyze the effect of overband on the stress distribution in epoxy impregnated REBCO coils. Furthermore, a series of parametric studies on overband radial build effects on radial stress in an epoxy impregnated coil are carried out based on the proposed FEM. Finally, the predictions of radial stresses in epoxy impregnated REBCO coils with overbands made of different engineered materials are presented and evaluated. The results show that the fabrication method of constructing overband radial build in epoxy impregnated REBCO pancake coils can effectively reduce the radial tensile stress in the windings.

Improved workability using preheating in the electromagnetic forming process

Electromagnetic forming (EMF) is a high-speed method used to shape metals using a high-energy magnetic field generated by a forming coil. In this study, EMF experiments were conducted on heat-treated aluminum pipes in an attempt to improve the workability of the metal, in which the heating temperature was varied. Heating to 200 °C and 250 °C resulted in deformation displacements of 1 and 5 mm, respectively. Coupled EM-structural numerical analyses revealed that the EM force was lower by 16 % after heating at 250 °C due to the reduction in the conductivity of aluminum at higher temperatures, resulting in a higher resistance. However, the flow stress decreased by about 50 % at 250 °C. Thus, the increase in displacement despite the reduction in the EM force at higher temperatures indicates that the workability of metals during EMF can be improved with preheating.

Using Multiwavelength Variability to Explore the Connection among X-Ray Emission, the Far-ultraviolet H2 Bump, and Accretion in T Tauri Stars

Abstract The high-energy radiation fields of T Tauri stars (TTS) should affect the surrounding circumstellar disk, having implications for disk transport and heating. Yet observational evidence of the effect of high-energy fields on disks is scarce. Here we investigate the connection between X-ray emission and the innermost gas disk by leveraging the variability of TTS. We obtained multiple epochs of coordinated data (taken either simultaneously or within a few hours) of accreting TTS with the Hubble Space Telescope, the Neil Gehrels Swift Observatory, and the Chandra X-ray Observatory. We measured the far-ultraviolet (FUV) H2 bump feature at 1600 Å, which traces gas <1 au from the star; the near-ultraviolet emission, from which we extract the accretion luminosity; and also the X-ray luminosity. We do not find a correlation between the FUV H2 bump and X-ray luminosity. Therefore, an observable tracer of the effect of X-ray ionization in the innermost disk remains elusive. We report a correlation between the FUV H2 bump and accretion luminosity, linking this feature to the disk surface density. We also see a correlation between the X-ray luminosity and the accretion column density, implying that flaring activity may influence accretion. These results stress the importance of coordinated multiwavelength work to understand TTS.

Numerical study on electromagnetic crimping of tubes

Electromagnetic crimping process is a non-conventional, high energy, high-velocity, and solid state impact crimping process. In this process, high energy and high-density electromagnetic field were used to accelerate and impact the flyer tube onto the base tube. A sequential coupled electromagnetic field analysis of electromagnetic crimping was performed using finite element method and boundary element method in the LS-DYNA software. In this study, three types of actuators having cross-sections namely circular, rectangular and square were modelled and analysed for electromagnetic crimping of aluminium Al 3003 and 4340 steel tubes. For this study, the length, number of turns, the pitch and the magnitude of a cross-sectional circumference of the actuators were kept constant. Process parameters such as discharge voltage, standoff distance, and actuator cross-section were varied in this study. Properties like a magnetic field, plastic strain, current density, radial deformation, impact velocity, Lorentz force and Tresca maximum shear stress developed in the flyer tube were compared with all three types of actuators and it was found that the actuator with square cross-section gives the better results. From this study, it was observed that the use of the square cross-section coil is more efficient than that of the circular or rectangular cross-section.

Instrument intercomparison in the high-energy field at the CERN-EU reference field (CERF) facility and comparison with the 2017 FLUKA simulations

This paper discusses an instrument intercomparison performed in the high-energy field at the CERF facility at CERN between 2015 and 2017 (October 2015, May 2016, November 2016 and June 2017). Measurements were performed in several reference exposure locations with the CERN extended-range Bonner Sphere Spectrometer (BSS), a Berthold LB4611, the LINUS rem counter from CERN, the LUPIN rem counter from ELSE Nuclear, the FHT 762 Wide Energy Neutron Detection Instrument (WENDI-II) from Thermo Scientific, the LUDLUM MODEL 42–41 PRESCILA NEUTRON PROBE and two models of Tissue-equivalent proportional counters (TEPCs) from Far West Technologies. All results are compared with the latest FLUKA reference values from simulations performed in 2017.

Simulation of irradiation uniformity for polyethylene and polypropylene in various high energy fields

When material samples are subjected to an irradiation field, the radiation energy may distribute unevenly at different depths, which greatly influences the irradiation induced modification. In this study, a novel method to improve the radiation uniformity is proposed. The dose distribution inside polyethylene and polypropylene in γ-ray and electron beam irradiation fields are simulated using the software GEANT4 by Monte Carlo method. Based on the simulation results, it is found that the addition of auxiliary aluminum layer after the sample can improve the radiation uniformity under γ-ray irradiation because of the contribution of the secondary electrons emitted from the aluminum layer. Furthermore, the uniformity of energy deposition using electron beams is better when the beam energy is higher. The energy deposition distributions inside the samples are simulated, and the most uniform ranges where the deviations are less than 2%, 3%, and 5% for polyethylene and polypropylene are suggested. This work may serve as a reference of irradiation uniformity for certain materials.

Deeply-sourced formate fuels sulfate reducers but not methanogens at Lost City hydrothermal field

Hydrogen produced during water-rock serpentinization reactions can drive the synthesis of organic compounds both biotically and abiotically. We investigated abiotic carbon production and microbial metabolic pathways at the high energy but low diversity serpentinite-hosted Lost City hydrothermal field. Compound-specific 14C data demonstrates that formate is mantle-derived and abiotic in some locations and has an additional, seawater-derived component in others. Lipids produced by the dominant member of the archaeal community, the Lost City Methanosarcinales, largely lack 14C, but metagenomic evidence suggests they cannot use formate for methanogenesis. Instead, sulfate-reducing bacteria may be the primary consumers of formate in Lost City chimneys. Paradoxically, the archaeal phylotype that numerically dominates the chimney microbial communities appears ill suited to live in pure hydrothermal fluids without the co-occurrence of organisms that can liberate CO2. Considering the lack of dissolved inorganic carbon in such systems, the ability to utilize formate may be a key trait for survival in pristine serpentinite-hosted environments.

Моделирование залечивания поврежденности металла высокоэнергетическим импульсным электромагнитным полем

Моделирование залечивания поврежденности металла высокоэнергетическим импульсным электромагнитным полем

Observation of Volkov-Pankratov states in topological HgTe heterojunctions using high-frequency compressibility

It is well established that topological insulators sustain Dirac fermion surface states as a consequence of band inversion in the bulk. These states have a helical spin polarization and a linear dispersion with large Fermi velocity. In this article we report on a set of experimental observations indicating the existence of massive surface states. These states are confined at the interface and dominate equilibrium and transport properties at high energy and/or high electric field. By monitoring the AC admittance of HgTe topological insulator field-effect capacitors, we access the compressibility and conductivity of surface states in a broad range of energy and electric fields. The Dirac surface states are characterized by a compressibility minimum, a linear energy dependence and a high mobility persisting up to energies much larger than the transport bandgap of the bulk. New features are revealed at high energies with signatures such as conductance peaks, compressibility bumps, a strong charge metastability and a Hall resistance anomaly. These features point to the existence of excited massive surface states, responsible for a strong intersubband scattering with the Dirac states and the nucleation of metastable bulk carriers. The spectrum of excited states agrees with predictions of a phenomenological model of the topological-trivial semiconductor interface. The model accounts for the finite interface depth and the effect of electric fields. The existence of excited topological states is essential for the understanding of topological phases and opens a route for engineering and exploiting topological resources in quantum technology.

Abstract ID: 125 Fundamental study for practical application of radiotherapy treatment planning system capable of evaluating neutron dose generated by various radiotherapy beams

There are many papers focused on secondary neutrons by calculation or measurement in high-energy radiotherapy fields [1] , [2] . Monte Carlo calculation is easy to acquire the three-dimensional spatial distribution of the neutrons and is considered to be particularly useful tool for evaluating the “on-axis” of the primary radiotherapy beam. In this study, calculations were performed for practical application of treatment planning that can take three-dimensional neutron dose into account by combining with new treatment planning system “Tsukuba-Plan” currently developed by University of Tsukuba. The incident radiotherapy beams were X-rays and “passive” particle beams (proton beam, carbon-ion beam). Particle and Heavy Ion Transport code System (PHITS) [3] was used as Monte Carlo code. We constructed calculation geometries that reproduces the actual beam delivery systems of these radiotherapy fields as precisely as possible, and confirmed consistency by comparing with measured percentage depth absorbed dose. The neutron doses and energy spectrums of “on-axis” and “off-axis” in homogeneous water phantom were calculated by irradiating each primary beams. Calculated neutron doses were compared with some published literatures. As next step, we used the Tsukuba-Plan to obtain the three-dimensional neutron dose distributions in human-shaped phantom in case of irradiating clinical beams with patient-specific devices such as bolus and collimators. We achieved a relative comparison of the secondary neutron doses and energy spectrums at “on-axis” and “off-axis” of each incident beams by using PHITS code. Additionally, the three-dimensional neutron dose distributions in the human-shaped phantom by each beams were obtained by combining the Tsukuba-Plan. In the future, this function can be used for various evaluation of the secondary neutrons in radiotherapy fields under individualized irradiation conditions.

Dynamic assessment of direct-current mobility in field-assisted sintered oxide dispersion-strengthened V-4Cr-4Ti alloys

BackgroundVanadium alloy is one of the potential candidate material for structural applications in a commercial fusion reactor. Extended survival of a structural material has a direct consequence on the net energy produced in a fusion reaction, it is important to develop ultra-functional materials with tailored microstructures, to meet the harsh fusion environments. Microstructure of material, indeed depend upon the thermodynamics and kinetics of material processing.MethodsAiming to meet the harsh fusion conditions, we have developed oxide dispersion strengthened V-4Cr-4Ti alloys by high energy ball milling and field assisted sintering technique. Possible microstructural, morphological aftermaths observed in ball milled yttria dispersed V-4Cr-4Ti powders is explored.Results and conclusionElectron microscopy and laser particle analysis acknowledge that yttria addition aids powder agglomeration during ball milling. Ball milled powder was then consolidated (to a relative density of ~100%) using field assisted sintering technique, under optimal sintering conditions. Densification profile has implied that heterogeneous powder characteristic (apparent particle size and shape of powder) tends to impede the direct-current conductivity across the powder particle during various stages of field assisted sintering. In order to understand the kinetics of the field assisted sintering process on the starting powders, a new method was developed to compute the activation energy required for the direct-current conductivity across the individual powder particles. Relatively higher activation energy (for direct-current conductivity) is required for sintering yttria dispersed V-4Cr-4Ti powder than its V-4Cr-4Ti counterpart.Graphical Quantitative dynamic sintering kinetics analysis of FAST processed vanadium alloys

CORRECTION FACTORS FOR ATTENUATION AND SCATTERING OF THE WALL OF A CYLINDRICAL IONIZATION CHAMBER IN THE 6-7 MeV HIGH-ENERGY PHOTON REFERENCE FIELD.

In high-energy photon reference fields the value of the air kerma rate is determined by using ionization chambers (ICs). From the charge collected inside the IC the dose can be calculated using a set of calibration and correction factors according to ISO 4037-2. A crucial parameter is the correction for the attenuation and scattering of the primary radiation due to the chamber wall. This parameter can be determined using Monte Carlo calculations. The evaluation of the factor was performed for a commercially available IC of the type Victoreen 550-3 under different build-up conditions. The results were verified by measurements in the R-F high-energy photon fields according to ISO 4037-1 at the Physikalisch-Technische Bundesanstalt (PTB) and the Japan Atomic Energy Agency (JAEA).

Neutron measurements in radiotherapy: A method to correct neutron sensitive devices for parasitic photon response

One of the major causes of secondary malignancies after radiotherapy treatments are peripheral doses, known to increase for some newer techniques (such as IMRT or VMAT). For accelerators operating above 10MV, neutrons can represent important contribution to peripheral doses. This neutron contamination can be measured using different passive or active techniques, available in the literature. As far as active (or direct-reading) procedures are concerned, a major issue is represented by their parasitic photon sensitivity, which can significantly affect the measurement when the point of test is located near to the field-edge. This work proposes a simple method to estimate the unwanted photon contribution to these neutrons. As a relevant case study, the use of a recently neutron sensor for “in-phantom” measurements in high-energy machines was considered. The method, called “Dual Energy Photon Subtraction” (DEPS), requires pairs of measurements performed for the same treatment, in low-energy (6MV) and high energy (e.g. 15MV) fields. It assumes that the peripheral photon dose (PPD) at a fixed point in a phantom, normalized to the unit photon dose at the isocenter, does not depend on the treatment energy. Measurements with ionization chamber and Monte Carlo simulations were used to evaluate the validity of this hypothesis. DEPS method was compared to already published correction methods, such as the use of neutron absorber materials. In addition to its simplicity, an advantage of DEPs procedure is that it can be applied to any radiotherapy machine.

Limiting factors in the pro-oxidants production with the use of fatty acids mixture separated from soapstock

The synthesis of prooxidants - carboxylates of variable valence metals (iron, copper and cobalt) was carried with the use of a mixture of fatty acids with an acid number of 100-120 mg KOH / g, separated from the soapstock, which is a liquid waste of oil- and fatproduction. Carboxylates of variable valency metals were synthesized in a high-energy ultrasound field using a generator USG13-0.1 / 22. Mixed thermal and ultrasound effects contribute to an increase in the yield of metal carboxylates. The maximum yield of prooxidates was over 84% (by weight).When carrying out the synthesis of carboxylates of metals of variable valence, ion activity was revealed in the exchange reactions with sodium salts on the basis of a mixture of fatty acids in the following order: Co2+ >Cu2+ >Fe2+. The synthesis of carboxylates of variable valence metals is a multifactor system and depends on temperature regimes, metal activity, viscosity and structural characteristics of a fatty acids mixture. The formation of metal carboxylates was carried out in a water-alcohol medium at a high rate for the heterogeneous systems, which are the exchange reactions between strong alkali salts and carbon acids. It should be noted that an increase in the synthesis temperature above 60 ° C with simultaneous ultrasound exposure reduced the yield of products and influenced the quality composition of the carboxylates of metals of variable valency.We should also take into account that ultrasound impact allows to obtain a prooxidant of the required dispersity and it is extremely important in the production of multifunctional and targeted additives. The use of ultrasound fields of high intensity in the synthesis of carboxylates of metals of variable valence is preferable in a less viscous medium due to the better ultrasound spread

Applicability of the two-angle differential method to response measurement of neutron-sensitive devices at the RCNP high-energy neutron facility

Quasi-monoenergetic high-energy neutron fields induced by 7Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Experiments were performed under 96–387MeV quasi-monoenergetic high-energy neutron fields at the Research Center for Nuclear Physics (RCNP), Osaka University. The measurement results for large high-density polyethylene (HDPE) sphere detectors agreed well with Monte Carlo calculations, which verified the adequacy of the two-angle differential method. By contrast, discrepancies were observed in the results for small HDPE sphere detectors and metal-induced sphere detectors. The former indicated that detectors that are particularly sensitive to low-energy neutrons may be affected by penetrating neutrons owing to the geometrical features of the RCNP facility. The latter discrepancy could be consistently explained by a problem in the evaluated cross-section data for the metals used in the calculation. Through those discussions, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.

Epistemic and Technical Things: The Phenomenological Boundaries of STS

We will introduce the words of Sharon Traweek presented in the book Beamtimes and lifetimes: the world of high energy physicists, affirming that in the field of high energy physics a “detector” (an instrument) that works perfectly will be considered worthless from the point of view of research. Our intentions are to make a contribution to the study of the nature of broken technologies and their relation to knowledge. To our help we will comment also a text of Cyrus C.M. Mody and Michael Lynch titled “Test objects and other epistemic things: a history of a nanoscale object”. Professors Mody and Lynch studied an object named silicon “(111) 7 X 7” that they describe as a “test object”. This object behaves as both a “technical object” and as an “epistemic thing”. In our terms, the silicon “(111) 7 X 7”-object, behaves as a prototype, that is as a “broken technology” that we do not really know how to describe and we do not really know how to use. In fact, the only way to answer to these interrogatives is manipulating the artifact and testing it in different epistemic and pragmatic situations. Our approach is phenomenological and that means that for us, every technology must be correlated to the human body. For phenomenology, the everyday world –included the exceptional case of the laboratory-world- is the expression of embodied intentionality.