Lattice correction and commissioning simulation of the Advanced Light Source upgrade storage ring
Not Available
43 PARTICLE ACCELERATORS↗
SEARCH · Engineering Papers
Results for “Accelerator Simulation”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient
Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday’s law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Simulation of Conduction Cooled SRF Cavity
SRF cavities are used heavily in high energy physics research, and simplifying operation of SRF cavities could enable their use in many fields of industry. Liquid helium coolant systems are a notable complexity of operating SRF cavities, and replacing liquid helium with cryocooler conduction cooling is an important research and development interest. As part of this effort, a system consisting of a 650 MHz single cell cavity, a commercial grade pulse tube refrigerator, and an aluminum thermal link was simulated through finite element analysis. The electromagnetic fields inside the cavity, heat flow through the system, and temperature distribution of the thermal link and cavity were calculated. Based on the simulations, the pulse tube refrigerator is capable of supplying adequate cooling power to a cavity with \ce{Nb3Sn} coating operating with an accelerating gradient between 6 and 12 MV/m. The maximum simulated temperature of the cavity was below 7 K, and the oscilla tions in temperature introduced by the pulse tube refrigerator were shown to dampen in amplitude before reaching the cavity surface.
43 PARTICLE ACCELERATORS↗
Investigating Coastal Vegetation Dynamics and Ecosystem Impacts Under Elevated CO 2 and Temperature: A Process‐Based Approach
Coastal forests are increasingly vulnerable to climate change and sea-level rise, with flooding and salinity driving transitions to marsh-dominated ecosystems. Using the coastal version of FATES-Hydro, we conducted 30-year simulations at two coastal forest sites—a broadleaf swamp white oak stand at Lake Erie and a conifer loblolly pine stand at Chesapeake Bay—under historical climate and elevated CO 2 (+100 ppm) and temperature (+1.5°C) scenarios. Elevated CO 2 increased net primary productivity at both sites, while warming alone intensified hydraulic stress and accelerated mortality, particularly in the conifer stand. Simulations show that elevated temperatures intensify vapor pressure deficit and hydraulic stress on trees already experiencing salinity- and submersion-driven water stress, increasing tree mortality beyond what would be expected in a non-water-limited environment. Marsh expansion partially compensated for tree loss at the Lake Erie site but reduced ecosystem productivity in the conifer forest at Chesapeake Bay. In conclusion, our results highlight how differences in stand structure, phenology, and local hydrology modulate ecosystem trajectories under climate change, emphasizing the importance of demographic and community-level processes for predicting the fate of coastal forests.
Ding, Junyan [Barcelona Supercomputing Center (BSC↗
SU-F-T-84: Measurement and Monte-Carlo Simulation of Electron Phase Spaces Using a Wide Angle Magnetic Electron Spectrometer
Purpose: To measure and simulate well-defined electron spectra using a linear accelerator and a permanent-magnetic wide-angle spectrometer to test the performance of a novel reconstruction algorithm for retrieval of unknown electron-sources, in view of application to diagnostics of laser-driven particle acceleration. Methods: Six electron energies (6, 9, 12, 15, 18 and 21 MeV, 40cm × 40cm field-size) delivered by a Siemens Oncor linear accelerator were recorded using a permanent-magnetic wide-angle electron spectrometer (150mT) with a one dimensional slit (0.2mm × 5cm). Two dimensional maps representing beam-energy and entrance-position along the slit were measured using different scintillating screens, read by an online CMOS detector of high resolution (0.048mm × 0.048mm pixels) and large field of view (5cm × 10cm). Measured energy-slit position maps were compared to forward FLUKA simulations of electron transport through the spectrometer, starting from IAEA phase-spaces of the accelerator. The latter ones were validated against measured depth-dose and lateral profiles in water. Agreement of forward simulation and measurement was quantified in terms of position and shape of the signal distribution on the detector. Results: Measured depth-dose distributions and lateral profiles in the water phantom showed good agreement with forward simulations of IAEA phase-spaces, thus supporting usage of this simulation source in the study. Measured energy-slit position maps and those obtained by forward Monte-Carlo simulations showed satisfactory agreement in shape and position. Conclusion: Well-defined electron beams of known energy and shape will provide an ideal scenario to study the performance of a novel reconstruction algorithm using measured and simulated signal. Future work will increase the stability and convergence of the reconstruction-algorithm for unknown electron sources, towards final application to the electrons which drive the interaction of TW-class laser pulses with nanometer thin target foils to accelerate protons and ions to multi-MeV kinetic energy. Cluster of Excellence of the German Research Foundation (DFG) “Munich-Centre for Advanced Photonics”.
07 ISOTOPE AND RADIATION SOURCES↗
From Femtoseconds to Gigaseconds: The SolDeg Platform for the Performance Degradation Analysis of Silicon Heterojunction Solar Cells
Heterojunction Si solar cells exhibit notable performance degradation. Here, we modeled this degradation by electronic defects getting generated by thermal activation across energy barriers over time. To analyze the physics of this degradation, we developed the SolDeg platform to simulate the dynamics of electronic defect generation. First, femtosecond molecular dynamics simulations were performed to create a-Si/c-Si stacks, using the machine learning-based Gaussian approximation potential. Second, we created shocked clusters by a cluster blaster method. Third, the shocked clusters were analyzed to identify which of them supported electronic defects. Fourth, the distribution of energy barriers that control the generation of these electronic defects was determined. Fifth, an accelerated Monte Carlo method was developed to simulate the thermally activated time-dependent defect generation across the barriers. Our main conclusions are as follows. (1) The degradation of a-Si/c-Si heterojunction solar cells via defect generation is controlled by a broad distribution of energy barriers. (2) We developed the SolDeg platform to track the microscopic dynamics of defect generation across this wide barrier distribution and determined the time-dependent defect density N(t) from femtoseconds to gigaseconds, over 24 orders of magnitude in time. (3) We have shown that a stretched exponential analytical form can successfully describe the defect generation N(t) over at least 10 orders of magnitude in time. (4) We found that in relative terms, Voc degrades at a rate of 0.2%/year over the first year, slowing with advancing time. (5) We developed the time correspondence curve to calibrate and validate the accelerated testing of solar cells. We found a compellingly simple scaling relationship between accelerated and normal times t normal ∝ t accel T(accel)/T(normal) . (6) We also carried out experimental studies of defect generation in a-Si:H/c-Si stacks. We found a relatively high degradation rate at early times that slowed considerably at longer time scales.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Parameter Dependencies of Early-Stage Tangential Discontinuity-Driven Foreshock Bubbles in Local Hybrid Simulations
Foreshock bubbles (FBs) are significant foreshock transients that can accelerate particles and disturb the magnetosphere-ionosphere system. In the kinetic formation model, foreshock ions interact with the discontinuity by performing partial gyrations to generate currents that change the magnetic field topology around the discontinuity. However, how different foreshock ion properties affect the growth of the field variations is not well understood. Therefore, we use 2-D local hybrid simulations to study the effects of different foreshock ion distributions and properties on the growth of tangential discontinuity (TD)-driven FBs. We discover that for a gyrophase-bunched distribution with an initial phase where the guiding center is on the other side of the TD, the foreshock ions gyrate together across the TD, causing more foreshock ions to cross the TD and leading to a faster expansion of the structure than for a Maxwellian distribution. A ring distribution also yields higher expansion speeds because of the higher projected velocity into the new perpendicular direction. For Maxwellian distributions, there are positive and linear correlations of the FB expansion speeds with the initial foreshock ion densities, thermal speeds, parallel speeds, and sine of the TD magnetic shear angles. These parameter dependencies grow in strength as the structures evolve with time. The foreshock ion distributions and properties that lead to stronger currents produce more significant magnetic field variations and higher expansion speeds. Our study helps quantify the formation and expansion of FBs to forecast their space weather effects and contribution to shock acceleration.
Andrew Vu↗
APOLLO: a facility-scale differentiable virtual accelerator at Fermilab FAST/IOTA
As the design complexity of modern accelerators grows, there is more interest in using advanced simulations that have fast execution time or yield additional insights like gradients. The FAST/IOTA facility has been working on implementing and experimentally validating an end-to-end digital twin that is both fast and gradient-aware, allowing for rapid prototyping of new software and experiments with minimal beam time costs. Our framework integrates physics and ML codes for linac and ring simulation through a set of generic interfaces between surrogate and physics-based sections. To reproduce device inputs and outputs, system state is exposed as a deterministic event loop in a specialized discrete event simulator architecture. Because Fermilab is undergoing control system transition, several APIs were implemented as final user interfaces - a fully asynchronous EPICS soft IOC, a gRPC-based Data Pool Manager (DPM), and legacy ACNET protocols. We discuss implementation details as well as challenges handling live data assimilation and future plans to extend modelling to main complex proton accelerators like PIPII and Booster.
Kuklev, Nikita [Fermilab]↗
Double Power-law Formation by Sequential Particle Acceleration
Spectral double power laws are common in solar high-energy phenomena such as flares and interplanetary energetic-electron events. However, the physical mechanism that produces the changes in power-law index within a single spectrum is unclear. We developed a fully analytical method of forming single power-law spectra from sequential acceleration of particles orbiting inside and hopping between simulated large-scale magnetic islands formed by flare reconnection. Here, we extend the analytical method to the formation of double power-law spectra by assuming sequential acceleration in two successive regions with different acceleration and particle-transport rates. The resulting spectral distribution is continuous and smooth, with a flattening at low energies, two power-law regions at mid-energies, and a steep rollover at high energies. The model provides analytical expressions for the spectral indices, all energy breaks, and normalization constants as functions of just three physical parameters of each acceleration region: (1) the energy gain in each accelerator, (2) the percentage of particles transferred between accelerators, and (3) the number of accelerators visited. One of the most salient predictions of our work is that the spectral index at high (low) energies is determined by the parameters of the first "seed" (second) acceleration region. By constructing the spectral distribution through an iterative analytical process, the evolution toward a double power law is easily characterized and explained. Our analytical model provides tools to interpret space- and ground-based observations from RHESSI, FOXSI, NuSTAR, Solar Orbiter/STIX, EOVSA, and future high-energy missions.
Solar flares↗
RELAP5-3D HTGR Validation Work at Idaho National Laboratory
Prismatic block-type high-temperature gas-cooled reactors (HTGRs) were built in the United States decades ago, and now advanced reactor vendors are seeking to deploy them again for a variety of applications. Deploying these reactors requires modelling and simulation tools that have been validated against conditions representative of the HTGR application. Idaho National Laboratory (INL) is leading the execution an of HTGR thermal hydraulics benchmark to accelerate the validation of thermal hydraulics modelling and simulation tools for these applications. That benchmark is based on a facility called the High Temperature Test Facility (HTTF). This work provides an overview of work conducted at INL over the last 2 years to validate RELAP5-3D against data from HTTF. This presentation shows results from multiple RELAP5-3D models and an HTTF experiment to assess the impact of certain modelling assumptions on results. The contents of this talk sit on the cutting edge of RELAP5-3D validation for HTGR analysis.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Modeling of a chain of three plasma accelerator stages with the WarpX electromagnetic PIC code on GPUs
The fully electromagnetic particle-in-cell code WarpX is being developed by a team of the U.S. DOE Exascale Computing Project (with additional non-U.S. collaborators on part of the code) to enable the modeling of chains of tens to hundreds of plasma accelerator stages on exascale supercomputers, for future collider designs. The code is combining the latest algorithmic advances (e.g., Lorentz boosted frame and pseudo-spectral Maxwell solvers) with mesh refinement and runs on the latest computer processing unit and graphical processing unit (GPU) architectures. In this paper, we summarize the strategy that was adopted to port WarpX to GPUs, report on the weak parallel scaling of the pseudo-spectral electromagnetic solver, and then present solutions for decreasing the time spent in data exchanges from guard regions between subdomains. In Sec. IV, we demonstrate the simulations of a chain of three consecutive multi-GeV laser-driven plasma accelerator stages.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Debris and meteoroid proportions deduced from impact crater residue analysis
This study is a further investigation of space-exposed samples recovered from the LDEF satellite and the Franco-Russian 'Aragatz' dust collection experiment on the Mir Space Station. Impact craters with diameters ranging from 1 to 900 micron were found on the retrieved samples. Elemental analysis of residues found in the impact craters was carried out using Energy Dispersive X-ray spectrometry (EDX). The analyses show evidence of micrometeoroid and orbital debris origins for the impacts. The proportions of these two components vary according to particle size and experimental position with respect to the leading edge of the spacecraft. On the LDEF leading edge 17 percent of the impacts were apparently caused by micrometeoroids and 11 percent by debris; on the LDEF trailing edge 23 percent of the impacts are apparently caused by micrometeoroids and 4 percent consist of debris particles - mostly larger than 3 micron in diameter - in elliptical orbits around the Earth. For Mir, the analyses indicate that micrometeoroids form 23 percent of impacts and debris 9 percent. However, we note that 60-70 percent of the craters are unidentifiable, so the definitive proportions of natural v. man-made particles are yet to be determined. Experiments carried out using a light gas gun to accelerate glass spheres and fragments demonstrate the influence of particle shape on crater morphology. The experiments also show that it is more difficult to analyze the residues produced by an irregular fragment than those produced by a spherical projectile. If the particle is travelling above a certain velocity, it vaporizes upon impact and no residues are left. Simulation experiments carried out with an electrostatic accelerator indicate that this limit is about 14 km/s for Fe particles impacting Al targets. This chemical analysis cut-off may bias interpretations of the relative populations of meteoroid and orbital debris. Oblique impacts and multiple foil detectors provide a higher likelihood of detection of residues as the velocities involved are lower.
Berthoud, Lucinda↗
Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator
Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration that accompanies the radial compression of the plasma in conical theta pinches.
Hallock, Ashley K.↗
ELECTRON ACCELERATION AT A CORONAL SHOCK PROPAGATING THROUGH A LARGE-SCALE STREAMER-LIKE MAGNETIC FIELD
Using a test-particle simulation, we investigate the effect of large-scale coronal magnetic fields on electron acceleration at an outward-propagating coronal shock with a circular front. The coronal field is approximated by an analytical solution with a streamer-like magnetic field featuring a partially open magnetic field and a current sheet at the equator atop the closed region. We show that the large-scale shock-field configuration, especially the relative curvature of the shock and the magnetic field line across which the shock is sweeping, plays an important role in the efficiency of electron acceleration. At low shock altitudes, when the shock curvature is larger than that of the magnetic field lines, the electrons are mainly accelerated at the shock flanks; at higher altitudes, when the shock curvature is smaller, the electrons are mainly accelerated at the shock nose around the top of closed field lines. The above process reveals the shift of the efficient electron acceleration region along the shock front during its propagation. We also find that, in general, the electron acceleration at the shock flank is not as efficient as that at the top of the closed field because a collapsing magnetic trap can be formed at the top. In addition, we find that the energy spectra of electrons are power-law-like, first hardening then softening with the spectral index varying in a range of −3 to −6. Physical interpretations of the results and implications for the study of solar radio bursts are discussed.
79 ASTRONOMY AND ASTROPHYSICS↗
Monte Carlo Analysis of the Performance of the ITER Diagnostic Residual Gas Analyzer
The composition of exhausted gas is a key parameter in long-pulse plasma fusion experiments, and its evolution shall be monitored at timescales relevant to plasma dynamics and plasma-wall interactions. A diagnostic residual gas analyzer (DRGA) is a multisensor instrument particularly suited to these studies, and ITER will adopt DRGAs in the equatorial and in the divertor tokamak regions. In this work, we have revisited the design of the ITER divertor DRGA through simple vacuum analytical considerations supported by simulations conducted with Molflow+, a test particle Monte Carlo (TPMC) simulation code commonly used in the particle accelerator community. Here, starting with recommendations on the manufacturing of the vacuum piping of the DRGA, this work is followed by a complete vacuum characterization of the diagnostic vacuum setup (pressure profiles at base pressure and during sampling, orifice diameter, and length optimization), and finally, the in-vessel residence time of the most important gas species is simulated. These studies have allowed us to give insights into some experimental results recently found on the prototype DRGA installed in the Wendelstein W7-X stellarator.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Modeling and simulation challenges pursued by the Consortium for Advanced Simulation of Light Water Reactors (CASL)
The Consortium for the Advanced Simulation of Light Water Reactors (CASL), the first Energy Innovation Hub of the Department of Energy, was established in 2010 with the goal of providing modeling and simulation (M&S) capabilities that support and accelerate the improvement of nuclear energy's economic competitiveness and the reduction of spent nuclear fuel volume per unit energy, and all while assuring nuclear safety. To accomplish this requires advances in M&S capabilities in radiation transport, thermal-hydraulics, fuel performance and corrosion chemistry. To focus CASL's R&D, industry challenge problems have been defined, which equate with long standing issues of the nuclear power industry that M&S can assist in addressing. To date CASL has developed a multi-physics “core simulator” based upon pin-resolved radiation transport and subchannel (within fuel assembly) thermal-hydraulics, capitalizing on the capabilities of high performance computing. CASL's fuel performance M&S capability can also be optionally integrated into the core simulator, yielding a coupled multi-physics capability with untapped predictive potential. Material models have been developed to enhance predictive capabilities of fuel clad creep and growth, along with deeper understanding of zirconium alloy clad oxidation and hydrogen pickup. Understanding of corrosion chemistry (e.g., CRUD formation) has evolved at all scales: micro, meso and macro. CFD R&D has focused on improvement in closure models for subcooled boiling and bubbly flow, and the formulation of robust numerical solution algorithms. For multiphysics integration, several iterative acceleration methods have been assessed, illuminating areas where further research is needed. Finally, uncertainty quantification and data assimilation techniques, based upon sampling approaches, have been made more feasible for practicing nuclear engineers via R&D on dimensional reduction and biased sampling. Industry adoption of CASL's evolving M&S capabilities, which is in progress, will assist in addressing long-standing and future operational and safety challenges of the nuclear industry. - Highlights: • Complexity of physics based modeling of light water reactor cores being addressed. • Capability developed to help address problems that have challenged the nuclear power industry. • Simulation capabilities that take advantage of high performance computing developed.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
TH-AB-BRA-07: PENELOPE-Based GPU-Accelerated Dose Calculation System Applied to MRI-Guided Radiation Therapy
Purpose: The clinical commissioning of IMRT subject to a magnetic field is challenging. The purpose of this work is to develop a GPU-accelerated Monte Carlo dose calculation platform based on PENELOPE and then use the platform to validate a vendor-provided MRIdian head model toward quality assurance of clinical IMRT treatment plans subject to a 0.35 T magnetic field. Methods: We first translated PENELOPE from FORTRAN to C++ and validated that the translation produced equivalent results. Then we adapted the C++ code to CUDA in a workflow optimized for GPU architecture. We expanded upon the original code to include voxelized transport boosted by Woodcock tracking, faster electron/positron propagation in a magnetic field, and several features that make gPENELOPE highly user-friendly. Moreover, we incorporated the vendor-provided MRIdian head model into the code. We performed a set of experimental measurements on MRIdian to examine the accuracy of both the head model and gPENELOPE, and then applied gPENELOPE toward independent validation of patient doses calculated by MRIdian’s KMC. Results: We achieve an average acceleration factor of 152 compared to the original single-thread FORTRAN implementation with the original accuracy preserved. For 16 treatment plans including stomach (4), lung (2), liver (3), adrenal gland (2), pancreas (2), spleen (1), mediastinum (1) and breast (1), the MRIdian dose calculation engine agrees with gPENELOPE with a mean gamma passing rate of 99.1% ± 0.6% (2%/2 mm). Conclusions: We developed a Monte Carlo simulation platform based on a GPU-accelerated version of PENELOPE. We validated that both the vendor provided head model and fast Monte Carlo engine used by the MRIdian system are accurate in modeling radiation transport in a patient using 2%/2 mm gamma criteria. Future applications of this platform will include dose validation and accumulation, IMRT optimization, and dosimetry system modeling for next generation MR-IGRT systems.
60 APPLIED LIFE SCIENCES↗
Impact of Momentum Perturbation on Convective Boundary Layer Turbulence
Mesoscale-to-microscale coupling is an important tool for conducting turbulence-resolving multiscale simulations of realistic atmospheric flows, which are crucial for applications ranging from wind energy to wildfire spread studies. Different techniques are used to facilitate the development of realistic turbulence in the large-eddy simulation (LES) domain while minimizing computational cost. Here, we explore the impact of a simple and computationally efficient Stochastic Cell Perturbation method using momentum perturbation (SCPM-M) to accelerate turbulence generation in boundary-coupled LES simulations using the Weather Research and Forecasting model. We simulate a convective boundary layer (CBL) to characterize the production and dissipation of turbulent kinetic energy (TKE) and the variation of TKE budget terms. Furthermore, we evaluate the impact of applying momentum perturbations of three magnitudes below, up to, and above the CBL on the TKE budget terms. Momentum perturbations greatly reduce the fetch associated with turbulence generation. When applied to half the vertical extent of the boundary layer, momentum perturbations produce an adequate amount of turbulence. However, when applied above the CBL, additional structures are generated at the top of the CBL, near the inversion layer. The magnitudes of the TKE budgets produced by SCPM-M when applied at varying heights and with different perturbation amplitudes are always higher near the surface and inversion layer than those produced by No-SCPM, as are their contributions to the TKE. This study provides a better understanding of how SCPM-M reduces computational costs and how different budget terms contribute to TKE in a boundary-coupled LES simulation.
17 WIND ENERGY↗