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At least 145 records · Page 8

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DOE OSTI2022

Atomic-scale e-beam sculptor

A system and method (referred to as the system) fabricates controllable atomic assemblies in two and three dimensions. The systems identify by a non-invasive imager, a local atomic structure, distribution of vacancies, and dopant atoms and modify, by a microscopic modifier, the local atomic structure, via electron beam irradiation. The systems store, by a knowledge base, cause-and-effect relationships based on a non-invasive imaging and electron scans. The systems detect, by detectors, changes in the local atomic structure induced by the electron irradiation; and fabricate, a modified atomic structure by a beam control software and feedback.

Kalinin, Sergei V.↗

DOE OSTI2021

ACCELERATOR CHALLENGES OF THE LHeC PROJECT

The LHeC project studies the design of a future electron-proton collider at CERN that will run in parallel to the standard LHC operation. For this purpose, the existing LHC storage ring will be combined with an Energy Recovery Linac (ERL), to accelerate electrons up to kinetic energy of 50 GeV. This concept - also applicable to the FCC-eh collider and studied at the PERLE project as prototype version - allows a peak luminosity of 10³⁴ cm⁻² s⁻¹. A sophisticated design of the RF structures, linacs, arcs, and interaction region is required. The electrons are accelerated and, after the interaction point, their energy is recovered through the same RF structures. While this energy recovery concept is a very promising approach, severe challenges are set by the layout of the interaction region, the beam separation concept and the design of the linac and arc lattice for the highest possible momentum acceptance. Emittance control and beam-beam effect of both, electron and proton beams, have been studied in front-to-end simulations and will be presented. We summarise the design principles of the ERL, the optimization of the arc lattice, and the main parameters of the project.

Holzer, B. J.↗

DOE OSTI2023

The mapping & avoidance of high order cavity modes

In this paper a technique developed in 2016 is presented for mapping the multidimensional, multi-mode high order mode landscape of a beam driven super conducting RF cavity. The initial use case for this technique was intended to allow longitudinal gradient control of a beam driven super conducting cavity while simultaneously avoiding many dangerous high order modes and excessive component stresses. This paper will focus on the stability and component stress considerations of the 56MHz superconducting cavity, located in the 4 o’clock sector interaction region of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The 56MHz cavity is intended to work in conjunction with the Stochastic Cooling system to improve the longitudinal confinement in the central 197MHz RF bucket and thus increase the integrated luminosity during heavy ion beam runs at RHIC.

43 PARTICLE ACCELERATORS↗

DOE OSTI2023

High-Performance Accelerator Modeling: Toward Improving Controls and Diagnostics for High-Brightness Beams in Experiment

One of the main charges of beam physics is to improve the overall beam quality delivered to experiments and applications, which is generally quantified by the beam brightness. High brightness beams have numerous applications, including x-ray free electron lasers and ultrafast electron diffraction (UED). To these ends, this thesis details efforts to use high-performance models --- high-fidelity models that execute quickly --- for controls and diagnostics. To demonstrate the generality of these techniques, this thesis focuses on three of the most successful photoinjector designs currently used worldwide: the UCLA/SLAC/BNL-type high-gradient S-band gun, the continuous-wave high-repetition rate VHF APEX gun and the L-band DESY-PITZ-type gun. Work will be shown from Pegasus (UCLA), HiRES (LBNL) and FAST (FNAL).Specifically, data-driven models for online virtual diagnostics are presented, in this case, in the context of UED at HiRES, leading to a temporal resolution improvement. Methods for improving the fidelity of physics-based models are discussed, with examples at HiRES, Pegasus and FAST. Markov-chain Monte Carlo analysis is applied to match simulations, in the context of photocathode studies at HiRES and Pegasus. Lastly, the augmentation of online model-based predictions with model-independent optimization is explored in a fluctuating environment at Pegasus and HiRES. A central theme of this dissertation is working with parameter fluctuations when modeling an accelerator beamline. Long-term drifts and shot-to-shot jitter exist in every accelerator to a varying degree and therefore play an important role in every chapter of this dissertation. This thesis attempts to address the issues associated with these fluctuations when trying to develop faithful model representations of the system.

43 PARTICLE ACCELERATORS↗

DOE OSTI2026

A reactive ferroelectric tuner for microphonics compensation

Jefferson Lab (JLab) is actively pursuing an extensive research program focused on developing advanced Nb₃Sn superconducting technology for particle accel-eration. Due to the brittle nature of Nb₃Sn coatings, a Ferroelectric Tuner (FRT) currently represents the most viable approach for microphonics compensation in these next-generation cavities. We suggest a novel, fast-responding FRT integrated directly into the main coupler, eliminating the need for an additional RF port. Leveraging a unique RF design based on a magic-T configuration, this advanced FRT will enable micro-phonics compensation in the ±30 Hz range without undesirable changes to the external quality factor.

Accelerator Physics↗

DOE OSTI2026

Machine learning at the Spallation Neutron Source accelerator and target

We describe the ongoing efforts to apply Machine Learning techniques to improve the performance of our accelerator and target. Specially, we are looking to minimize halo beam losses in the absence of a proper physics model, automatically detect and log anomalies in the target support systems such as cooling, and detect and prevent errant beam pulses in the linac. We also describe the infrastructure we use to acquire and stream data to the GPU cluster for training, our code development cycle, and edge computing for model inference. To minimize halo beam losses, we use a Reinforcement Learning technique tested on a virtual accelerator. The target anomaly detection is trained on archived data using incomplete physics models and is made part of the existing target reporting system. The errant beam prevention analyzes beam current and beam phase waveforms as well as accelerator configuration data to predict errant pulses. We also develop continual learning to adapt to changes in the accelerator.

Accelerator Physics↗

DOE OSTI2026

Detectors and beam monitors based on wide bandgap semiconductors at cryogenic temperatures

Wide-bandgap semiconductors, such as single-crystal diamond and sapphire, can be used to measure the flux of passing particles through a particle-induced conductivity effect. We recently demonstrated a diamond-based, electrodeless electron beam halo monitor. This monitor utilized a thin diamond blade placed within an open, high-quality microwave resonator. The blade partially intercepted the beam and changes in the RF properties of the resonator were used to infer beam parameters. To enhance the sensitivity of our semiconductor sensors, we propose two new techniques: (1) biasing the semiconductor sensor to support avalanche multiplication of free carriers, and (2) operating at cryogenic temperatures to reduce intrinsic semiconductor losses and increase the mobility of induced carriers. These techniques are applicable not only to particle beam diagnostics but also to the detection of various types of ionizing radiation.

Accelerator Physics↗

DOE OSTI2025

Preliminary study of auto-differentiation algorithm in beam dynamics with stochastic process

Modern particle accelerator optimization requires sophisticated computational methods to address the inherently stochastic nature of beam dynamics. This research develops a framework applying AD to SDEs that specifically addresses beam dynamics challenges in particle accelerators, focusing on accurately modeling and optimizing beam behavior in regimes dominated by stochastic processes. By incorporating key physical phenomena such as synchrotron radiation, wakefield effects, and quantum excitation, the framework aims to provide auto differentiation on the figure of merit of the phase space evolution and beam dynamics. The methodology will enable effective optimization method in a dynamic system with stochastic process.

Accelerator Physics↗

DOE OSTI2025

A reactive ferroelectric tuner for microphonics compensation

Accelerator Physics↗

DOE OSTI2020

FOFB-compatible AC Local Bump as a Potential New Operations Mode for NSLS-II

AC local bumps of the beam orbit developed at NSLS-II are successfully used for accelerator physics studies. Recently, AC bumps localized at light-generating insertion devices (ID) are considered by NSLS-II beamline scientists as a possible user operation mode. The AC perturbation of the X-ray beam in a controllable way will provide a possibility to investigate the effects of the source size and temporal evolution on the coherence of the photon beam. It also can be used to average out the spatial non-uniformity of the beam intensity caused by the beamline optics. Before the implementation of the AC orbit bumps into user operations, we must investigate if the electron beam perturbation affects the other beamlines. A proof-of-principle experiment was carried out: an AC bump was created and well localized in the CSX and/or FXI beamline. Transparency of this AC bump to other beamlines has been studied, the results are discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Precise electron beam-based target-wavelength trimming for frequency conversion in integrated photonic resonators

We demonstrate post-fabrication target-wavelength trimming with a gallium phosphide on a silicon nitride integrated photonic platform using controlled electron-beam exposure of hydrogen silsesquioxane cladding. A linear relationship between the electron-beam exposure dose and resonant wavelength red-shift enables deterministic, individual trimming of multiple devices on the same chip to within 30 pm of a single target wavelength. Second harmonic generation from telecom to near infrared at a target wavelength is shown in multiple devices with quality factors on the order of 10 4 . Post-fabrication tuning is an essential tool for targeted wavelength applications including quantum frequency conversion.

Thiel, Lillian↗

DOE OSTI2024

Rapid Demonstration of Bremsstrahlung Diode Optimization

Optimization of the radiation pattern from a Bremsstrahlung target for a given application is possible by controlling the electron beam that impacts the high-atomic-number target. In this work, the electron beam is generated by a 13MV vacuum diode that terminates a coaxial magnetically insulted transmission line (MITL) on the HERMES-III machine at Sandia National Labs. Work by Sanford introduced a geometry for vacuum diodes that can control the flow within bounds. The "indented anode", as coined by Sanford, can straighten out the electron beam in a high-current diode that would otherwise be prone to beam pinching. A straighter beam will produce a more forwardly directed radiation pattern while a pinching electron beam will yield a focal point or hot spot on axis and a more diffuse radiation pattern. Either one of these may be desirable depending on the application. This work serves as a first attempt to optimize the radiation pattern in the former sense of collimating the radiation pattern given a limited parameter space. The optimization is attempted first using electromagnetic particle-in-cell simulations in the EMPIRE code suite. The setup of the models used in EMPIRE is discussed along with some basic theory behind some of the models used in the simulations such as anode heating and secondary ions. Theoretical work performed by Allen Garner and his students at Purdue is included here, which concerns the impact of collisions in these vacuum diodes. The EMPIRE simulations consider both an aggressive and a conservative design. The aggressive design is inherently riskier while the conservative design is chosen as something that, while still a risk, is more likely to perform as expected. The ultimate goal of this work was to validate the EMPIRE code results with experimental data. While the experiment that tested the diode designs proposed by the simulation results fell outside of the fiscal boundaries of this project (and for that reason the results of which are not included in this report), the hardware for the experiment was designed and drafted within those same fiscal boundaries, and is thus included in this report. However, there was yet another experiment performed in this project that tested a key feature of the diode: the hemispherical cathode. Those results are documented here as well, which show that the cathode tip is an important aspect to controlling the diode flow. A short series of simulations on this diode were also performed after the experiment in order to gain a better understanding of the effect of ions. on the flow pattern and faceplate dose profile.

43 PARTICLE ACCELERATORS↗

DOE OSTI2021

Flat epitaxial quasi-1D phosphorene chains

The emergence of peculiar phenomena in 1D phosphorene chains (P chains) has been proposed in theoretical studies, notably the Stark and Seebeck effects, room temperature magnetism, and topological phase transitions. Attempts so far to fabricate P chains, using the top-down approach starting from a few layers of bulk black phosphorus, have failed to produce reliably precise control of P chains. We show that molecular beam epitaxy gives a controllable bottom-up approach to grow atomically thin, crystalline 1D flat P chains on a Ag(111) substrate. Scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and density functional theory calculations reveal that the armchair-shaped chains are semiconducting with an intrinsic 1.80 ± 0.20 eV band gap. This could make these P chains an ideal material for opto-electronic devices.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Optically pumped gradient magnetometer

A method is provided for sensing a magnetic field in a magnetic gradiometer of the kind in which pump light and light constituting an optical carrier traverse first and second atomic vapor cells that contain host atoms and that are separated from each other by a known distance. According to such method, the host atoms are prepared in a coherent superposition of two quantum states that differ in energy by an amount that is sensitive to an ambient magnetic field. Modulation of the optical carrier in the respective cells gives rise to sidebands that interfere to generate a beat frequency indicative of the magnetic field gradient. The host atoms are prepared at least in a mode that allows measurement of ambient magnetic field components perpendicular to the axis of the pump light. In such mode, the host atoms are spin-polarized by pump light while subjected to a controlled magnetic field directed parallel to the pump beam, and then the controlled magnetic field is adiabatically extinguished.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Design Considerations and Operational Features of the Collimators for the Fermilab Main Injector and Recycler

The Fermilab Main Injector system delivers 700 kW of 120 GeV Proton beam for neutrino experiments. Since 2013 this has been achieved using slip stacking accumulation in the Recycler with up to 12 batches from the Fermilab Booster per Main Injector Ramp Cycle. To control activation from beam loss, collimation systems in the Booster to Recycler transfer line, in the Recycler and in the Main Injector are employed. Residual radiation measurements around the ring with detailed studies at the collimators are required to maintain adequate loss control. We will review design considerations, operational parameters and activation results for more than ten years of operation. Simulations with MARS15 are used to explore the activation rates and the isotopic composition of the resulting activation.

43 PARTICLE ACCELERATORS↗

DOE OSTI2021

PIP-II 800 MeV Proton Linac Beam Pattern Generator

The PIP2 IT Beam Pattern Generator is the system that synchronizes beam injection and the RF systems between the PIP2 LINAC to the Booster. The RF frequencies of these two accelerator systems are not harmonically related. Synchronization is accomplished by controlling two MEBT Beam Choppers, which select 162.5MHz beam bunches from the LEBT and RFQ to produce an appropriate reduced beam bunch pattern that enables bucket-to-bucket transfer to the Booster RF at 46.46MHz (84th harmonic). This chopping pattern also reduces the beam current to an average of 2mA over the Booster injection, matching the Linac nominal beam current. The BPG also generates the RF frequency/phase reference which the Booster will phase lock to during injection. The BPG is fully programmable, allowing for arbitrary beam patterns with adjustable timing parameters, having a fine adjustment resolution of 38ps. The latter is accomplished using digital signal processing techniques. This paper discusses the design of the BPG, its construction, test results, and operational experience after being integrated into the PIP2 IT test accelerator and concludes with a discussion of the system’s performance and future plans.

43 PARTICLE ACCELERATORS↗

DOE OSTI2022

Phase-space tailoring and cooling of charged-particle beams for energy- and intensity-frontier applications

This project addressed accelerator science & technology researches relevant to the Intensity and Energy frontiers by investigating generic techniques to tailor and cool the phase-space distributions of charged-particle beams. Specifically, the project had two main research thrusts: (i) the development of phase-space tailoring techniques using externally-applied electromagnetic fields and (ii) the investigation of phase-space control using the beam’s self-field such as the optical-stochastic cooling (OSC). The work related to the development of phase-space-tailoring techniques leveraged on the research performed under our previous grant DE-SC0011831 where new temporal-shaping methods were proposed and some experimentally demonstrated. The work related to the concept of beam manipulation using self fields, and especially OSC, built on the achievements supported by grant DE-SC0013761 which focused on a OSC proof-of-principle experiment at the Fermilab’s IOTA ring.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Beam dynamics driven design of powerful energy recovery linac for experiments

Powerful ERL for experiments (PERLE) is a novel energy recovery linac (ERL) test facility [1], designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider and the Future Circular Collider and to host dedicated nuclear and particle physics experiments. Its main goal is to demonstrate the high current, continuous wave, multipass operation with superconducting cavities at 802 MHz. With very high beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERLs and becomes a “stepping stone” between the present state-of-the-art 1 MW ERLs and the future 100 MW scale applications. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗