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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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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

When and how to treat an IMRT patient on a second accelerator without replanning?

When a linear accelerator is unavailable for treatment, a clinical decision is imminent regarding whether a patient should be treated on a linear accelerator other than the machine the patient was scheduled on, or whether treatment should be postponed until the original Linac becomes available. This work investigates the feasibility of switching patients to different accelerators for intensity-modulated radiation therapy (IMRT). We have performed Monte Carlo simulations of photon beams from different Linac models and vendors. Prostate and head and neck (H&N) treatment plans for Siemens Primus, Primart, and Varian 21EX accelerators are studied in this work. Dose distributions for given plans are recalculated using different beam data with the same nominal energy from different Linacs. We have compared dose-volume histograms (DVHs) and the maximum, the minimum, and the mean doses to the target and critical structures because of switching accelerators. In the process of switching a treatment plan to a different accelerator, issues exist, including optimum penumbra compensation, dose distribution at the boundary of target and critical structures, and multileaf collimator (MLC) leaf-width effects, which need to be considered and verified with measurements. Our Monte Carlo simulation results confirm that, for the cases we tested, the dose received by 95% of the planning target volume differs by 0.2% to 1.5% between Siemens Primus and Varian 21EX Linacs. The discrepancy is within our clinical acceptance criteria of 3% for IMRT treatments. In making the final decision on whether to switch machines or not, the tumor control probabilities (TCPs) based on a linear-quadratic model are compared. Based on the analyses performed in this work, it is therapeutically more beneficial to switch a patient to a different machine than to postpone a treatment until the original machine is available, especially for fast-growing tumors such as H&N cancers.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Accelerated test protocols to predict service life and durability of solid oxide fuel cells

Reliable accelerated test protocols are needed for solid oxide fuel cell research to facilitate rapid learning on key durability issues, identify potential modes of failure expeditiously, and eventually predict the calendar lifetime of an electrochemical cell. In this work, solid oxide fuel cells operated at a constant current density were compared to cells undergoing accelerated measurements, which are composed of intermittent current injection to the cell. A general accelerated test profile was developed by cycling a solid oxide fuel cell from open circuit to a predetermined operating current density that is the same as the current density during a steady-state operation, to accelerate the local redox environment. The following parameters were studied: current density, operation temperature, moist level, sintering temperature, cycling current, cycling frequency, and operation time. Up to 1,320,000 cycles were generated in this work. The cell degradation was accelerated by nearly 10 times, suggesting the feasibility of using this protocol for acceleration test to predict life performance and durability of solid oxide fuel cells.

08 HYDROGEN↗
DOE OSTI2019

Generation and acceleration of electron bunches from a plasma photocathode

Plasma waves generated in the wake of intense, relativistic laser or particle beams can accelerate electron bunches to gigaelectronvolt energies in centimetre-scale distances. This allows the realization of compact accelerators with emerging applications ranging from modern light sources such as the free-electron laser to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre wakefields can accelerate witness electron bunches that are either externally injected or captured from the background plasma. Here in this work, we demonstrate optically triggered injection and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This ‘plasma photocathode’ decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical density down-ramp injection and is an important step towards the generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness. This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultrahigh-brightness beams.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

An inverse free electron laser acceleration-driven Compton scattering X-ray source

Abstract The generation of X-rays and γ-rays based on synchrotron radiation from free electrons, emitted in magnet arrays such as undulators, forms the basis of much of modern X-ray science. This approach has the drawback of requiring very high energy, up to the multi-GeV-scale, electron beams, to obtain the required photon energy. Due to the limit in accelerating gradients in conventional particle accelerators, reaching high energy typically demands use of instruments exceeding 100’s of meters in length. Compact, less costly, monochromatic X-ray sources based on very high field acceleration and very short period undulators, however, may enable diverse, paradigm-changing X-ray applications ranging from novel X-ray therapy techniques to active interrogation of sensitive materials, by making them accessible in energy reach, cost and size. Such compactness and enhanced energy reach may be obtained by an all-optical approach, which employs a laser-driven high gradient accelerator based on inverse free electron laser (IFEL), followed by a collision point for inverse Compton scattering (ICS), a scheme where a laser is used to provide undulator fields. We present an experimental proof-of-principle of this approach, where a TW-class CO 2 laser pulse is split in two, with half used to accelerate a high quality electron beam up to 84 MeV through the IFEL interaction, and the other half acts as an electromagnetic undulator to generate up to 13 keV X-rays via ICS. These results demonstrate the feasibility of this scheme, which can be joined with other techniques such as laser recirculation to yield very compact photon sources, with both high peak and average brilliance, and with energies extending from the keV to MeV scale. Further, use of the IFEL acceleration with the ICS interaction produces a train of high intensity X-ray pulses, thus enabling a unique tool synchronized with a laser pulse for ultra-fast strobe, pump-probe experimental scenarios.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Laser based 100 GeV electron acceleration scheme for muon production

High energy muons, due to their unique ability to penetrate deeply into matter, can enable radiography of structures that cannot be probed by other forms of radiation. Current terrestrial sources of muons require conventional GeV-TeV particle accelerators which are hundreds to thousands of meters in size. Laser wakefield acceleration (LWFA) can achieve acceleration gradients of two-to-three orders of magnitude greater than conventional accelerators, thus shrinking the accelerator to a number of meters. We propose a concept for a compact muon source based on the first self-consistent PIC simulations of an all optical LWFA that uses a guiding channel to achieve electron energies of 100 GeV in a distance of 6 m with a driving laser energy of 300 J in a single stage. From the resulting electron energy spectrum we estimate muon production for this source. We show that this accelerator, coupled with high average power laser driver technology, provides the basis for a high energy and high flux muon source.

laser-produced plasmas↗
DOE OSTI2018

A proposal for antiparallel acceleration of positrons using CEBAF

Here, we present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e - acceleration and counter clockwise e + acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increased energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Ab-initio Cu alloy design for high-gradient accelerating structures

Operation of normal conducting accelerator structures at high accelerating gradients is beneficial for many accelerator applications in basic science, industry, medicine, and National Security. RF breakdown is the major factor that limits the achievable accelerating gradients. Previous experiments on copper (Cu) have demonstrated that RF breakdown probability can be significantly decreased by hardening the material and alloying Cu with solutes such as silver (Ag). In this paper, we propose a figure-of-merit (FOM) that characterizes the ability of Cu alloys to withstand high-gradients. The FOM represents a trade-off between hardening through solid solution strengthening and the additional thermal stress induced by incremental RF pulse heating resulting from changes in electronic properties induced by alloying. We performed high-throughput ab initio calculations and computed the FOM for a large number of binary Cu alloys. Several promising candidate alloys for high-gradient accelerating structures were identified, such as CuAg, CuCd, CuHg, CuAu, CuIn, and CuMg. CuAg alloys have previously exhibited low RF breakdown rates in experiments. The results provide guidance for selecting alloys for the future high-gradient normal conducting accelerating structures operating at very high gradients.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Machine learning for reducing noise in RF control signals at industrial accelerators

Industrial particle accelerators typically operate in dirtier environments than research accelerators, leading to increased noise in RF and electronic systems. Furthermore, given that industrial accelerators are mass produced, less attention is given to optimizing the performance of individual systems. As a result, industrial accelerators tend to underperform their own hardware capabilities. Improving signal processing for these machines will improve cost and time margins for deployment, helping to meet the growing demand for accelerators for medical sterilization, food irradiation, cancer treatment, and imaging. Our work focuses on using machine learning techniques to reduce noise in RF signals used for pulse-to-pulse feedback in industrial accelerators. Here we review our algorithms and observed results for simulated RF systems, and discuss next steps with the ultimate goal of deployment on industrial systems.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Microsecond-latency feedback at a particle accelerator by online reinforcement learning on hardware

The commissioning and operation of future large-scale scientific experiments will challenge current tuning and control methods. Reinforcement learning (RL) algorithms are a promising solution due to their ability to dynamically adapt to changing environments and consider delayed consequences. In many real-world applications, RL policies must produce actions in real time, often within microseconds to milliseconds, imposing significant constraints on system latency and computational overhead that conventional machine learning libraries are not designed to handle. To control phenomena in real time at these timescales, RL needs to be deployed on-the-edge, namely on dedicated hardware located near the system it controls, without relying on a host CPU or cloud-based inference. In this work we present the design and deployment of an experience accumulator system in a particle accelerator. In this system, deep-RL algorithms run using hardware acceleration and act within a few microseconds, enabling the use of RL for control of phenomena like beam instabilities. The training uses the collected data offline to reduce the number of operations carried out on the acceleration hardware. The proposed architecture was tested in real experimental conditions at the Karlsruhe research accelerator, a synchrotron light source, where the system was used to control artificially induced horizontal betatron oscillations in real-time, with a control loop period of just 2.7 μs. The results showed a performance comparable to the commercial feedback system available at the accelerator, demonstrating the viability and potential of this approach. Due to the self-learning and reconfiguration capability of this implementation, a seamless application to other control problems is possible. Applications range from particle accelerators to large-scale research and industrial facilities.

FPGA↗
DOE OSTI2018

Synchronous acceleration with tapered dielectric-lined waveguides

Here, we present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that a $\sim 200$-keV electron beam can be accelerated to an energy of $\sim10$~MeV over $\sim 10$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Differentiable Preisach Modeling for Characterization and Optimization of Particle Accelerator Systems with Hysteresis

Future improvements in particle accelerator performance are predicated on increasingly accurate online modeling of accelerators. Hysteresis effects in magnetic, mechanical, and material components of accelerators are often neglected in online accelerator models used to inform control algorithms, even though reproducibility errors from systems exhibiting hysteresis are not negligible in high precision accelerators. Here, we combine the classical Preisach model of hysteresis with machine learning techniques to efficiently create nonparametric, high-fidelity models of arbitrary systems exhibiting hysteresis. We experimentally demonstrate how these methods can be used in situ, where a hysteresis model of an accelerator magnet is combined with a Bayesian statistical model of the beam response, allowing characterization of magnetic hysteresis solely from beam-based measurements. Finally, we explore how using these joint hysteresis-Bayesian statistical models allows us to overcome optimization performance limitations that arise when hysteresis effects are ignored.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Summary of Working Group 3: Laser and High-Gradient Structure-Based Acceleration

Accelerating particles at high gradients with high efficiencies is essential for reduction of size and cost of future accelerators for science and industry. This includes a future multi-TeV e+e- collider for particle, free-electron lasers for basic energy sciences and national security, industrial accelerators for energy and environmental applications, and accelerators for other applications. One way to achieve this is to use advanced externally-powered structures, both laser and RF driven. Working Group 3 (WG3) discussed novel accelerating structures with new geometries, new materials, frequencies from microwave to THz and optical spectrum, and operating conditions from room temperature to cryogenic. Presentations included recent advances in understanding RF breakdown and multipactor phenomena at different frequencies and materials, and other physics limitations to the accelerating gradient. Other relevant topics, such as developing high-gradient photoinjectors, high-efficiency RF power sources, and RF structures for a potential muon collider were discussed also. More details on each of the WG3 topics can be found in the articles published in these proceedings.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Method for computationally efficient design of dielectric laser accelerator structures

Here, dielectric microstructures have generated much interest in recent years as a means of accelerating charged particles when powered by solid state lasers. The acceleration gradient (or particle energy gain per unit length) is an important figure of merit. To design structures with high acceleration gradients, we explore the adjoint variable method, a highly efficient technique used to compute the sensitivity of an objective with respect to a large number of parameters. With this formalism, the sensitivity of the acceleration gradient of a dielectric structure with respect to its entire spatial permittivity distribution is calculated by the use of only two full-field electromagnetic simulations, the original and ‘adjoint’. The adjoint simulation corresponds physically to the reciprocal situation of a point charge moving through the accelerator gap and radiating. Using this formalism, we perform numerical optimizations aimed at maximizing acceleration gradients, which generate fabricable structures of greatly improved performance in comparison to previously examined geometries.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration

Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser *. Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Fermilab Accelerator Complex: Status and Improvement Plans

Fermilab carries out an extensive program of accelerator-based high-energy particle physics research, which relies on 8 GeV and 120 GeV proton accelerators. Routine operations with 700 kW, 120 GeV proton beam power on a neutrino target was achieved in 2017. There are plans to further increase the beam power to the 900 kW range. The next major upgrade of the Fermilab accelerator complex, the PIP-II project, is under development. Its goal is to deliver 1.2 MW of beam power on target at the start of the DUNE experiment in the middle of the next decade. PIP-II will replace the existing 40-year old 400 MeV normal-conducting Linac with a modern 800 MeV superconducting RF based linear accelerator. There are several concepts for future upgrades that will increase the beam power to >2.4 MW, after replacement of the existing 8 GeV Booster synchrotron. The Muon Campus provides 3.1 GeV polarized muons to the g-2 experiment and will provide 8 kW of 8 GeV protons to the Mu2e production target. The Fermilab Test Beam Facility provides a primary 120 GeV proton beam of moderate intensity, (1-300 kHz) and secondary particle beams of energies down to about 1 GeV, consisting of hadrons, muons and/or electrons/photons for detectors tests. In this article we discuss the current performance of the Fermilab accelerator complex, the upgrade plans for the next two decades, and the accelerator R&D program to address cost and performance risks for these upgrades.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Collaboration on Radiation Driven Chemistry and Accelerator Operations

The Notre Dame Radiation Laboratory (NDRL) will contribute subject matter expertise to increase the Fermilab Illinois Accelerator Research (IARC) team’s knowledge of radiation chemistry processes. NDRL will do this by offering guidance on what analytical equipment to use to measure the effects of electron beam treatment during and post treatment. NDRL will also offer guidance that will help further develop IARC applications. The application areas are not limited to, but may include chemistries in the energy generation, industrial and environmental sectors. Fermi National Accelerator Laboratory’s IARC team will contribute subject matter expertise on accelerator operations to help NDRL optimize operation of their Titan-Beta accelerator. The objective of NDRL is to optimize accelerator output, as well as the beam transport and focusing from the accelerator to several experimental beam ports. NDRL also wants to install and optimize a new subharmonic pre-buncher to be able to deliver sub-nanosecond timescale doses for the study of reaction kinetics decoupled from molecular diffusion.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Maximizing the efficiency of plasma-based lepton accelerators

The next generation of particle accelerators will likely rely on compact accelerating structures to achieve very high gradients; one such candidate is accelerators using plasmas for the accelerating structures. Because of the small length scales of these structures, they can also be prone to the beam break-up instability, which would spoil the quality of the beam and leave it unsuitable for many applications. The goal of this project is to develop a framework for understanding the instabilities in plasma accelerators using language from conventional linear accelerator instabilities, such as wake fields and wake functions. During the course of this Phase I, we benchmarked a pseudo-spectral particle-in-cell code to determine its suitability for computing wake functions, and developed a procedure for extracting wake functions from a sequence of simulations using this code.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

RF Accelerator Technology R&D: Report of AF7-rf Topical Group to Snowmass 2021

Accelerator radio frequency (RF) technology has been and remains critical for modern high energy physics (HEP) experiments based on particle accelerators. Tremendous progress in advancing this technology has been achieved over the past decade in several areas highlighted in this report. These achievements and new results expected from continued R&D efforts could pave the way for upgrades of existing facilities, improvements to accelerators already under construction (e.g., PIP-II), well-developed proposals (e.g., ILC, CLIC), and/or enable concepts under development, such as FCC-ee, CEPC, C 3 , HELEN, multi-MW Fermilab Proton Intensity Upgrade, future Muon Colloder, etc. Advances in RF technology have impact beyond HEP on accelerators built for nuclear physics, basic energy sciences, and other areas. Recent examples of such accelerators are European XFEL, LCLS-II and LCLS-II-HE, SHINE, SNS, ESS, FRIB, and EIC. To support and enable new accelerator-based applications and even make some of them feasible, we must continue addressing their challenges via a comprehensive RF R&D program that would advance the existing RF technologies and explore the nascent ones.

43 PARTICLE ACCELERATORS↗