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DOE OSTI2014

Density matrix in technique of polarized ion sources

The use of the density matrix is the most direct way to work with polarization parameters. The solutions of the equation for the density matrix are obtained for hydrogen and deuterium. The magnetic moments of nuclei are explicitly incorporated into the equations, even though numerically it does not make a big difference. It is shown that in the general case the density matrix can not be reduced to the one with the only spin variables of the nucleus in contradiction with the statement of K. Blum [K. Blum, Density Matrix Theory and Applications].

43 PARTICLE ACCELERATORS↗

DOE OSTI2025

Process Optimization and Modeling for Minerals Sustainability (PrOMMiS) v1.0.0

The U.S. Department of Energy's ("DOE") Process Optimization and Modeling for Minerals Sustainability project ("PrOMMiS Project") was initiated in 2023 to transform the national Critical Minerals and Rare Earth Elements (CM & REE) landscape, thereby supporting DOE's three enduring strategic objectives: security, economic competitiveness, and environmental responsibility. To address this initiative, the PrOMMiS Project will develop, demonstrate, and deploy an open-source, advanced system modeling, optimization, and analysis application ("PrOMMiS Software Application") that will support industry decision-makers by accelerating the scale-up of novel CM & REE technologies by de-risking the development and deployment of commercial scale processes and maximizing learning throughout the development cycle.

Beattie, KeithS [Lawrence Berkeley National Labora↗

DOE OSTI2026

Flutter

The following repositories are a set of libraries that are needed for applications that are being developed for users of the Accelerator control system. The programming language used is Dart and for the user interface use the Flutter framework. URL for code repositories: - https://github.com/fermi-ad/flutter-controls-core - https://github.com/fermi-ad/flutter-controls-plotting - https://github.com/fermi-ad/flutter-controls-auth - https://github.com/fermi-ad/flutter-gql-acsys - https://github.com/fermi-ad/flutter-gql-faas - https://github.com/fermi-ad/dart-gql-acsys - https://github.com/fermi-ad/dart-explicit-imports - https://github.com/fermi-ad/dart-gql-faas - https://github.com/fermi-ad/design-system

Neswold, Rich [Fermi National Accelerator Laborato↗

DOE OSTI2025

Pulse duration dependent effects of ultrafast laser induced damage on a 1030 nm multi-layer dielectric mirror for high repetition rate, high average power laser systems

High repetition rate, high peak, and average power laser systems are crucial for next-generation particle accelerators, inertial confinement fusion, and secondary particle sources. These applications demand durable laser optics, particularly interference coatings on optics lasting millions of shots at high fluence. This study focuses on designing, testing, and simulating multi-layer dielectric (MLD) mirrors for pulse durations of 260 fs, 77 fs, and 25 fs at 1030 nm wavelength and 45-degree incidence angle with p -polarization. S-on-1 laser-induced damage thresholds (LIDT) for varying pulse numbers were determined, with single-shot LIDT values of 0.98 Jcm -2 , 1.63 Jcm -2 , and 2.3 Jcm -2 for 25 fs, 77 fs, and 260 fs respectively. A strong correlation between blister shape and local fluence was observed, implying that the layer expansion in a blister depends on local fluence. We have also examined mechanisms responsible for laser-induced stress generation and energy release rates in blister formation. Damage mechanisms are further explored by finite-difference time-domain (FDTD) simulations, incorporating Keldysh strong field ionization, whose predictions were in excellent agreement with the onset of damage determined experimentally. These findings offer insights for enhancing MLD coating technology, promising more efficient and resilient laser systems for diverse scientific and industrial applications.

Noor, Mohamed Yaseen (ORCID:000000021036644X)↗

DOE OSTI2022

Multiphysics Simulation of the Thermal Response of a Nanofibrous Target in a High-Intensity Beam

Nanofibrous structures are of high interest to the fields of engineering and materials science, and investigation of their properties as well as discovery of novel applications for them both constitute lively areas of research. A very promising application of nanofiber mats lies in the field of accelerator technology: beam targets made from nanofiber mats offer a solution to the problem of advancing the "intensity frontier"–-the limit on the beam intensities that can be realized in fixed target experiments and neutrino production facilities. However, testing has shown that the survivability of these nanofiber targets depends strongly on their manufacturing parameters, such as the packing density of fibers. In this work, we will use multiphysics simulations to perform a thermal study on how nanofiber targets react to high intensity beams, so that the dependency of the targets’ lifetime on their construction parameters can be better understood.

43 PARTICLE ACCELERATORS↗

DOE OSTI2013

Ion Fast Ignition-Establishing a Scientific Basis for Inertial Fusion Energy --- Final Report

The Fast Ignition (FI) Concept for Inertial Confinement Fusion (ICF) has the potential to provide a significant advance in the technical attractiveness of Inertial Fusion Energy reactors. FI differs from conventional ?central hot spot? (CHS) target ignition by decoupling compression from heating: using a laser (or heavy ion beam or Z pinch) drive pulse (10?s of nanoseconds) to create a dense fuel and a second, much shorter (~10 picoseconds) high intensity pulse to ignite a small volume within the dense fuel. The compressed fuel is opaque to laser light. The ignition laser energy must be converted to a jet of energetic charged particles to deposit energy in the dense fuel. The original concept called for a spray of laser-generated hot electrons to deliver the energy; lack of ability to focus the electrons put great weight on minimizing the electron path. An alternative concept, proton-ignited FI, used those electrons as intermediaries to create a jet of protons that could be focused to the ignition spot from a more convenient distance. Our program focused on the generation and directing of the proton jet, and its transport toward the fuel, none of which were well understood at the onset of our program. We have developed new experimental platforms, diagnostic packages, computer modeling analyses, and taken advantage of the increasing energy available at laser facilities to create a self-consistent understanding of the fundamental physics underlying these issues. Our strategy was to examine the new physics emerging as we added the complexity necessary to use proton beams in an inertial fusion energy (IFE) application. From the starting point of a proton beam accelerated from a flat, isolated foil, we 1) curved it to focus the beam, 2) attached the foil to a superstructure, 3) added a side sheath to protect it from the surrounding plasma, and finally 4) studied the proton beam behavior as it passed through a protective end cap into plasma. We built up, as we proceeded, a self-consistent picture of the quasi-neutral plasma jet that is the proton beam that, for the first time, included the role of the hot electrons in shaping the jet. Controlling them?through design of the accelerating surface and its connection to the surrounding superstructure?is critical; their uniform spread across the proton accelerating area is vital, but their presence in the jet opposes focus; their electron flow away from the acceleration area reduces conversion efficiency but can also increase focusing ability. The understanding emerging from our work and the improved simulation tools we have developed allow designing structures that optimize proton beams for focused heating. Our findings include: ? The achievable focus of proton beams is limited by the thermal pressure gradient in the laser-generated hot electrons that drive the process. This bending can be suppressed using a controlled flow of hot electrons along the surrounding cone wall, which induces a local transverse focusing sheath electric field. The resultant (vacuum-focused) spot can meet IFE requirements. ? Confinement of laser-generated electrons to the proton accelerating area can be achieved by supporting targets on thin struts. That increases laser-to-proton conversion energy by ~50%. As noted above, confinement should not be total; necessary hot-electron leakage into the surrounding superstructure for proton focusing can be controlled by with the strut width/number. ? Proton jets are further modified as they enter the fuel through the superstructure?s end cap. They can generate currents during that transit that further focus the proton beams. We developed a new ion stopping module for LSP code that properly accounted for changes in stopping power with ionization (e.g. temperature), and will be using it in future studies. The improved understanding, new experimental platforms, and the self-consistent modeling capability allow researchers a new ability to investigate the interaction of large ion currents with warm dense matter. That is of direct importance to the creation and investigation of all aspects of warm dense matter as well as to proton-ignited FI.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2019

Quantification of MagLIF Morphology using the Mallat Scattering Transformation

The morphology of the stagnated plasma resulting from Magnetized Liner Inertial Fusion (MagLIF) is measured by imaging the self-emission x-rays coming from the multi-keV plasma, and the evolution of the imploding liner is measured by radiographs. Equivalent diagnostic response can be derived from integrated rad-MHD simulations from programs such as Hydra and Gorgon. There have been only limited quantitative ways to compare the image morphology, that is the texture, of simulations and experiments. We have developed a metric of image morphology based on the Mallat Scattering Transformation (MST), a transformation that has proved to be effective at distinguishing textures, sounds, and written characters. This metric has demonstrated excellent performance in classifying ensembles of synthetic stagnation images. We use this metric to quantitatively compare simulations to experimental images, cross experimental images, and to estimate the parameters of the images with uncertainty via a linear regression of the synthetic images to the parameter used to generate them. This coordinate space has proved very adept at doing a sophisticated relative back-ground subtraction in the MST space. This was needed to compare the experimental self emission images to the rad-MHD simulation images. We have also developed theory that connects the transformation to the causal dynamics of physical systems. This has been done from the classical kinetic perspective and from the field theory perspective, where the MST is the generalized Green's function, or S-matrix of the field theory in the scale basis. From both perspectives the first order MST is the current state of the system, and the second order MST are the transition rates from one state to another. An efficient, GPU accelerated, Python implementation of the MST was developed. Future applications are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2022

Collaborative Research: Explosive reconnection in relativistic magnetically-dominated plasmas

Magnetic fields can be the dominant component of astrophysical plasmas, so that the magnetic energy density might exceed even the rest-mass energy density of matter. In this extreme (and largely unexplored) regime the magnetic field controls the overall plasma evolution, dissipation, and acceleration of non-thermal particles. This plasma regime, applicable to a variety of astrophysical sources --- magnetars, pulsars and pulsar wind nebulae (PWNe), jets of Active Galactic Nuclei (AGNs) and Gamma-Ray Bursters (GRBs) --- is dramatically different from laboratory plasmas, the magnetospheres of planets, and the interplanetary plasma. Relativistic astrophysical sources then provide an unique opportunity to study the fundamental plasma physics of magnetically-dominated plasmas; a novel and quickly evolving field of theoretical research which, by investigating energy conversion and particle energization processes in plasmas, is of vital importance to the Fusion Energy Sciences DoE program.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Plasma Mirrors For High Power Lasers: A new approach for high repetition rates combined with realistic PIC simulations

We describe a research program to develop high quality plasma mirrors for use with high repetition rate, high power laser facilities to greatly facilitate experiments in high energy density physics, particularly when using solid density targets. A system delivering ultrathin, free standing liquid crystal films that could handle PW class laser pulses was developed that preserved the laser beam image quality and improved pulse contrast by over two orders of magnitude. The pulse contrast improvement was measured using a high dynamic range cross-correlation. The system operated at a repetition rate of several PMs formed in situ per minute. Extension to 1 Hz repetition rates should be possible. As a practical application, a PM system was used to separate laser accelerated electrons from the ultrashort pulse drive laser so that the electron beam emittance could be directly measured. The 20 nm thick PMs did not contribute significantly to emittance degradation. It was also demonstrated that the films could operate in the difficult plasma and laser environment present for GeV laser based electron acceleration. PM operation is still not well understood and much work with PMs is done empirically. Accordingly, we also demonstrated a particle-in-cell based simulation technique that would model PM operation, tracking the PM operation from cold, neutral atoms to a hot dense plasma by accounting for multiphoton ionization, plasma collisionality, and the dynamically changing index of refraction. Simulations in 3D were compared to a 2D based approach that was comparable. Finally, we developed a simpler model that can predict the intensity at which a plasma mirror will have its peak reflectivity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

Effects of a strong applied magnetic field on relativistic laser-plasma interactions

This project investigated the role played by strong external magnetic fields in laser-matter interactions at relativistic intensities and their impact of resulting high-energy density phenomena. The regimes that can benefit from currently available or soon to be available magnetic fields have been identified. The applications of this project include laser-driven ion acceleration and laser-driven plasma heating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Unifying Quantum Materials Modeling and Experiments: The Role of Machine Learning Interatomic Potentials

Computational experiments have emerged as a powerful complement to traditional experiments in the design of new materials. The development of machine learning (ML) and deep learning techniques, combined with database construction and data mining, has significantly enhanced traditional quantum mechanical methods. This synergy enables the rapid development of structure-property relationships. In this talk, I will discuss our recent efforts in applying Machine Learning Interatomic Potentials (MLIAPs) to accelerate materials modeling across various material classes and challenging applications where traditional methods fall short. First, I will highlight the success of MLIAPs in accurately modeling the melting behavior of complex materials. Our results demonstrate high fidelity with experimental observations and also with calculated reference melting temperatures. In the second application, I will discuss how MLIAPs are trained and applied to elucidate the interplay between segregation tendencies and surface reconstructions in CuNi alloys under oxidizing conditions. A key factor in the success of these MLIAP applications is the design of minimalistic yet flexible datasets along with a computational framework for training MLIAPs.

Saidi, Wissam↗

DOE OSTI2025

Enhancements to Lab-on-a-Fish Technology: Final Report for I3T Project 81245

PNNL has engaged in discussions with several organizations regarding potential future collaborations. PNNL has developed the Lab-on-a-Fish prototypes and produced video instructions for an organization conducting research on shark eggs. Several organizations have expressed interest in using the Lab-on-a-Fish for their studies. We’ve also updated two versions of the Lab-on-a-Fish to expand its applications to a wider range of animal studies and accelerate its commercialization. The new design of the Lab-on-a-Fish, which incorporates PCB-based electrodes, has demonstrated the ability to capture clear ECG signals without the need for additional needle-shaped electrodes. This innovation eliminates the need for implanting electrodes beneath the fish's skin at specific locations, which is required with the current version of Lab-on-a-Fish. This change significantly simplifies the manufacturing and implantation process. For the Lab-on-a-Fish design that uses an optical pulse oximeter, the measurement results were primarily influenced by respiratory activity rather than heart rate. This occurred because the oximeter was placed beneath the operculum. Further research and development are needed to explore more suitable locations and methods for accurate pulse oximeter measurements.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2025

First elliptical cavity fabricated with metallographic polishing

The development of an easy and inexpensive Nb sheet preparation process, based on metallographic polishing, has been presented earlier [1, 2]. The aim is to remove the damage layer caused by the rolling process on the sheet in order to reduce the length of surface treatment on completed cavities. The process has been applied on a QPR sample and tested in RF, without any surface chemistry. Its surface resistance is about 4 times lower than the EP baseline at 414 MHz, 2 K [3]. The first elliptical cavity based on this principle has been produced at KEK, starting with large polished sheets developed in collaboration between IJCLAB, and the company LAMPLAN. We present its 1st RF test at KEK, with a HF rinsing and a recrystallization treatment at 600C for 10h, without any chemical etching at first. References: *1: C. Antoine and R. Crooks, “Reducing Electropolishing Time with Chemical-Mechanical Polishing”, SRF2009. *2: O. Hryhorenko, et al., "An innovative approach of surface polishing for SRF cavity applications". Journal of Manufacturing and Materials Processing, 2023. 7(2): p. 62. *3: O. Hryhorenko, et al., "Recent advances in metallographic polishing for SRF application", SRF2023.

Dohmae, Takeshi [High Energy Accelerator Research ↗

DOE OSTI2025

Study of the Scintillating Properties of Materials Based on Self- Assembling Quantum Dots Embedded into a Semiconductor Bulk

The goal of the project is to investigate scintillating properties of materials based on self-assembled InAs QDs embedded into GaAs bulk. According to theoretical predictions, such materials can have scintillating properties and low self-absorption. Compared to scintillators based on inorganic scintillating crystals, QD-based scintillators could have significantly higher light yield and shorter emission times. We intend to check the theoretical predictions experimentally, measure scintillation parameters and their dependence on the QD-based materials and learn how the properties could be optimized for practical applications.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Evaluation of Damage in Medium Voltage Cable Using Machine Learning

Developments in cable test instrumentation coupled with artificial intelligence and machine learning (ML) to aid in interpretation of cable test signals supports the feasibility for automated analysis of reflectometry tests for low voltage power cables. This work seeks to leverage prior ML work and success for low voltage cables to evaluate potential application to medium voltage (2kV to 10kV) installations. The Accelerated and Real-Time Environmental Nodal Assessment (ARENA) Cable Motor Test Bed at Pacific Northwest National Laboratory (PNNL) was used to test a medium voltage cable with several types of damage including thermal aging and low resistance conductor-to-shield faults. The cable was tested using an inductive clamshell coupler to protect the test instruments from the energized cable voltages that would damage the test instruments if coupled directly to the energized conductor.

42 ENGINEERING↗

DOE OSTI2022

DEVELOPMENT OF HIGH QUANTUM EFFICIENCY STRAINED SUPERLATTICE SPIN POLARIZED PHOTOCATHODES VIA METAL ORGANIC CHEMICAL VAPOR DEPOSITION

Spin polarized photocathodes are necessary to examine parity violations and other fundamental phenomena in the field of high energy physics. To create these devices, expensive and complicated growth processes are necessary. While integral to accelerator physics, spin polarized electrons could have other exciting applications in materials science and other fields of physics. In order to explore these other applications feasibly, the relative supply of spin polarized photocathodes with a high rate of both polarization and photoemission needs to be increased. One such way to increase this supply is to develop the means to grow them faster and at a larger scale. Because most photocathodes are grown in slow, small-scale processes like Molecular Beam Epitaxy, an alternative needed to be found. In the following work, strained superlattice photocathodes were fabricated using metal organic vapor phase epitaxy. Using this growth process, we demonstrated that it is possible to create high quality photocathodes at a higher rate while maintaining a high quality of polarization and quantum efficiency, thus allowing for the exploration of other applications for these devices.

Belfore, Benjamin↗

DOE OSTI2024

On a Simplified Approach to Achieve Parallel Performance and Portability Across CPU and GPU Architectures

This paper presents software advances to easily exploit computer architectures consisting of a multi-core CPU and CPU+GPU to accelerate diverse types of high-performance computing (HPC) applications using a single code implementation. The paper describes and demonstrates the performance of the open-source C++ matrix and array (MATAR) library that uniquely offers: (1) a straightforward syntax for programming productivity, (2) usable data structures for data-oriented programming (DOP) for performance, and (3) a simple interface to the open-source C++ Kokkos library for portability and memory management across CPUs and GPUs. The portability across architectures with a single code implementation is achieved by automatically switching between diverse fine-grained parallelism backends (e.g., CUDA, HIP, OpenMP, pthreads, etc.) at compile time. The MATAR library solves many longstanding challenges associated with easily writing software that can run in parallel on any computer architecture. This work benefits projects seeking to write new C++ codes while also addressing the challenges of quickly making existing Fortran codes performant and portable over modern computer architectures with minimal syntactical changes from Fortran to C++. We demonstrate the feasibility of readily writing new C++ codes and modernizing existing codes with MATAR to be performant, parallel, and portable across diverse computer architectures.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1977

Mercury ion thruster research, 1977

The measured ion beam divergence characteristics of two and three-grid, multiaperture accelerator systems are presented. The effects of perveance, geometry, net-to-total accelerating voltage, discharge voltage and propellant are examined. The applicability of a model describing doubly-charged ion densities in mercury thrusters is demonstrated for an 8-cm diameter thruster. The results of detailed Langmuir probing of the interior of an operating cathode are given and used to determine the ionization fraction as a function of position upstream of the cathode orifice. A mathematical model of discharge chamber electron diffusion and collection processes is presented along with scaling laws useful in estimating performance of large diameter and/or high specific impluse thrusters. A model describing the production of ionized molecular nitrogen in ion thrusters is included.

Wilbur, P. J.↗