Physical Sciences

Efficient accelerator modeling and particle tracking are key for the design and configuration of modern particle accelerators. In this work, we present JuTrack, a nested accelerator modeling package developed in the Julia programming language and enhanced with compiler-level automatic differentiation (AD). With the aid of AD, JuTrack enables rapid derivative calculations in accelerator modeling, facilitating sensitivity analyses and optimization tasks. We demonstrate the effectiveness of AD-derived derivatives through several practical applications, including sensitivity analysis of space-charge-induced emittance growth, nonlinear beam dynamics analysis for a synchrotron light source, and lattice parameter tuning of the future Electron-Ion Collider (EIC). Through the incorporation of automatic differentiation, this package opens up new possibilities for accelerator physicists in beam physics studies and accelerator design optimization. Program summary: Program Title: JuTrack CPC Library link to program files: https://doi.org/10.17632/r2g5zkwp7s.1 Developer's repository link: https://github.com/MSU-Beam-Dynamics/JuTrack.jl.git Licensing provisions: MIT Programming language: Julia Nature of problem: Derivatives of the physics parameters calculated in accelerator modeling are critical for sensitivity analysis and optimization of the whole system. Traditional numerical approaches often rely on finite differences for derivative computations, which can prone to numerical inaccuracies. In highly nonlinear accelerator systems, like those encountered in synchrotrons and colliders, accurate sensitivity analysis and optimization require a large number of derivative evaluations. Thus, there is a need for more efficient methods to compute these derivatives accurately, especially when optimizing complex accelerator lattices or studying complicated collective effects, such as space-charge effects, wakefield effects, and beam-beam interaction. Solution method: JuTrack addresses this problem by integrating compiler-level automatic differentiation (AD) into accelerator modeling routines, offering a powerful toolset for rapid derivative computation. Developed in the Julia programming language, JuTrack uses the Enzyme AD package to perform gradient-based analyses with minimal computational overhead. The package provides an efficient way to compute derivatives by directly differentiating through the model code, thus avoiding approximation errors associated with finite difference methods. It is designed to handle complex beam dynamics simulations, including complicated collective effects, such as space-charge effects, wakefield effects, beam-beam interaction, and combination of Truncated Power Series Algebra (TPSA) with AD. It can be applied to lattice optimization and beam dynamics analysis for future accelerators like the Electron-Ion Collider (EIC). Users can easily apply the package to their models, enabling robust optimization and sensitivity analysis in their accelerator studies. Additional comments including restrictions and unusual features: JuTrack is particularly well-suited for scenarios requiring frequent derivative calculations, such as during beam dynamics optimization, sensitivity analysis, and accelerator tuning. Its integration with the Julia programming language provides excellent performance due to Julia's just-in-time (JIT) compilation capabilities. The modular nature of JuTrack and Julia's easy-to-understand syntax allows for future extensions and custom modifications, making it adaptable to a variety of accelerator configurations.

Intermetallic phases are preferred to reduce the amount of platinum used for catalytic applications as compared to solid solution alloys, due to their stability at elevated temperatures while preserving or even enhancing the catalytic properties. Here, we show a two-step process to form an intermetallic NiPt L10 phase. In this work, NiPt solid solution thin films were fabricated by direct current and high-power impulse magnetron sputtering processes, which allow for precise thickness and chemical composition control. Following deposition, an additional annealing step is used to form the desired intermetallic phase. We show that the required annealing time for intermetallic phase formation is considerably reduced for NiPt thin films with a thickness of 240 nm, as compared to its bulk counterpart.

Residual resistance ratio (RRR) of superconducting strands is an important parameter for magnet electrical stability. RRR serves as a measure of the low-temperature electrical conductivity of the copper within a conductor that has a copper stabilization matrix. For Nb3Sn, due to the need of a reaction heat treatment, the technical requirements for high quality measurements of strands extracted from Rutherford cables are particularly demanding. Quality of wire, cabling deformation, heat treatment temperature, heat treatment atmosphere, sample handling, and measurement methods can all affect the RRR. Therefore, as an integral part of the electrical quality control (QC) of Nb3Sn Rutherford cables manufactured at the Lawrence Berkeley National Laboratory, it was prudent that we established a RRR measurement system that can isolate the assessment of cable-fabrication-related impacts from sample preparation and measurement factors. Here we describe a bespoke cryocooler-based measurement system, capable of measuring RRR of over 80 samples in a single cooldown. The samples are mounted on custom-designed printed circuit boards that accommodate the shape of strands extracted from a Rutherford cable without added deformation, which we will show is critical in ensuring that the measurements accurately represent the RRR values of the conductor within the cable. Using this sample mounting solution, we routinely measure the overall RRR of the strand as well as individual intra-strand sections corresponding to both cable edges and cable broad faces with high reproducibility. Such measurements provide valuable information on the variation of RRR along the length of the strands as well as across strand productions and cable runs over time.

Laser-driven (LD) ion acceleration has been explored in a newly constructed short focal length laser beamline at the BELLA petawatt facility (interaction point 2, iP2). For applications utilizing such LD ion beams, a beam transport system is required, which for reasons of compactness be ideally contained within 3 m. While they are generated from a micron-scale source, large divergence and energy spread of LD ion beams present a unique challenge to transporting them compared to beams from conventional accelerators. This study gives an overview of proposed compact transport designs using permanent magnets satisfying different requirements depending on the application for the iP2 laser beamline such as radiation biology, material science, and high-energy density science. These designs are optimized for different parameters such as energy spread and peak proton density according to the application's need. The various designs consist solely of permanent magnet elements, which can provide high magnetic field gradients on a small footprint. While the field strengths are fixed, we have shown that the beam size is able to be tuned effectively by varying the placement of the magnets. The performance of each design was evaluated based on high-order particle tracking simulations of typical LD proton beams. We also examine the ability of certain configurations to tune and select beam energies, critical for specific applications. A more detailed investigation was carried out for a design to deliver 10 MeV LD accelerated ions for radiation biology applications. With these transport system designs, the iP2 laser beamline is ready to house various application experiments.

Excitation of long-lived states in bromine nuclei using a tabletop laser-plasma accelerator providing pulsed (<100  fs) electron beams provided a sensitive probe of γ strength and level densities in the nuclear quasicontinuum and may indicate angular momentum coupling through electron-nuclear interactions. Solid-density active LaBr_{3} targets absorb real and virtual photons up to 35±2.5  MeV and deexcite through γ cascade into different states. A factor of 4.354±0.932 enhancement of the ^{80}Br^{m}/^{80}Br^{g} isomeric ratio was observed following electron irradiation, as compared to bremsstrahlung. Additional angular momentum transfer could possibly occur through nuclear-plasma or electron-nuclear interactions enabled by the ultrashort electron beam. Further investigation of these mechanisms could have far-reaching impact including decreased storage of long-term nuclear waste and an improved understanding of heavy element formation in astrophysical settings.

With the advent of high repetition rate laser facilities, novel diagnostic tools compatible with these advanced specifications are required. This paper presents the design of an active gamma-ray spectrometer intended for these high repetition rate experiments, with particular emphasis on functionality within a PW level laser-plasma interaction chamber's extreme conditions. The spectrometer uses stacked scintillators to accommodate a broad range of gamma-ray energies, demonstrating its adaptability for various experimental setups. In addition, it has been engineered to maintain compactness, electromagnetic pulse resistance, and ISO-5 cleanliness requirements while ensuring high sensitivity. The spectrometer has been tested in real conditions inside the PW-class level interaction chamber at the BELLA center, LBNL. The paper further details the calibration process, which utilizes a 60Co radioactive source, and describes the unfolding technique implemented through a stochastic minimization method.

Deposition using filtered pulsed cathodic arc plasma is known to produce dense and adherent thin films due to energetic ions which carry significant ion kinetic and potential energies. The role of potential energy coming from multiply charged metal ions in film formation remains under-explored, since the enhancement of charge states in cathodic arcs is coupled with an increased flux and kinetic energies of ions. In this work, the influence of ion potential energy on structural properties of thin films is investigated, while keeping the mean ion kinetic energies unchanged. Two material systems are considered: metallic V-Al and compound V-Al-N in non-reactive and reactive deposition, respectively. For V-Al plasma and thin films, the impact of metal ion potential energy is demonstrated. In the V-Al-N case, in addition to metal ions, activated (namely, ionized, dissociated, and excited) nitrogen species are found to be a significant factor for crystalline growth of the metastable cubic phase.

The particle-in-cell (PIC) and Monte Carlo collisions (MCC) methods are workhorses of many numerical simulations of physical systems. Recently, it was pointed out that, while the two methods can be exactly-or nearly-energy-conserving independently, combining the two leads to anomalous numerical heating. This paper reviews the standard explicit PIC-MCC algorithm, elucidates the origins of the anomalous numerical heating, and explains how to couple the two methods such that the anomalous numerical heating is avoided.

Quantum measurements are a fundamental component of quantum computing. However, on present-day quantum computers, measurements can be more error prone than quantum gates and are susceptible to nonunital errors as well as nonlocal correlations due to measurement crosstalk. While readout errors can be mitigated in postprocessing, this is inefficient in the number of qubits due to a combinatorially large number of possible states that need to be characterized. In this work, we show that measurement errors can be tailored into a simple stochastic error model using randomized compiling, enabling the efficient mitigation of readout errors via quasiprobability distributions reconstructed from the measurement of a single preparation state in an exponentially large confusion matrix. We demonstrate the scalability and power of this approach by correcting readout errors without matrix inversion on a large number of different preparation states applied to a register of eight superconducting transmon qubits. Moreover, we show that this method can be extended to midcircuit measurements used for active feedback via quasiprobabilistic error cancellation, and we demonstrate the correction of measurement errors on an ancilla qubit used to detect and actively correct bit-flip errors on an entangled memory qubit. Our approach enables the correction of readout errors on large numbers of qubits and offers a strategy for correcting readout errors in adaptive circuits in which the results of midcircuit measurements are used to perform conditional operations on nonlocal qubits in real time.

A 6-around-1 transposed cable using superconducting star® wires can be useful for future circular collider applications. We made three cable samples using single star® wires with a diameter of 1.3 mm. The first two samples, made with a cabling machine, used star® wires consisting of a 0.7 mm diameter Nb-Ti core. The third cable sample was manually wound and used a star® wire made with a 0.81 mm diameter Cu core. The first sample showed severe degradation after the cable was bent to a 75 mm radius. The current-carrying capability of the innermost and outermost rebco tapes in the star® wire degraded by 42% to 98% and the middle rebco tapes remained intact. This was also the case for the second and straight cable sample. After fabrication of the third cable sample, we observed only about 5% reduction in the current along the wire, measured at different locations inside the terminations. The results indicate that the differences in architecture or fabrication of the star® wires could have caused differences in critical current retention after cabling.