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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Theories derived from Haissinski equation and their applications to electron storage rings

As a stationary solution of the Vlasov–Fokker–Planck equation, the Haissinski equation predicts the equilibrium line density of a bunch that circulates in a storage ring for a given wake function. The research in this paper shows that some equations regarding the centroid shift of the bunch, the peak position of the bunch profile, bunch length, and the impedance from the bunch profile can be derived from the Haissinski equation in a self-consistent manner. Specifically, a generalized quadratic equation for potential-well bunch lengthening is derived to accommodate any arbitrary impedance model (that is, the impedance spectrum under consideration can take any form). This expands upon Zotter's cubic equation, which is primarily applicable to inductive impedance. The equations derived in this paper are tested using computed impedance models for some electron storage rings, showing machine-dependent properties of impedance effects. We conclude that these equations can be employed in electron storage rings to effectively bridge the gap between impedance computations and beam-based measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Beam Breakup Simulations for the Scorpius Flash-Radiography Accelerator

Beam breakup (BBU) in linear induction accelerators (LIAs) used for flash radiography is problematic because the high-frequency beam motion can blur the source spot, thereby degrading resolution. Amplification of BBU depends directly on details of cell design and is suppressed in operation by the solenoidal magnetic field focusing on the electron beam. Therefore, much effort has gone into design of the cells and magnetic focusing for the new Scorpius radiography LIA. Here, in this article, we use computer simulations to demonstrate that BBU in Scorpius should be no more than in present radiography LIAs at the Los Alamos National Laboratory.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Analytical estimates of beam intensity limitations in the EIC Beam Accumulator Ring

This report summarizes analytical estimates of beam intensity limitations in the Beam Accumulator Ring (BAR), a part of the Electron-Ion Collider injector complex under development at Brookhaven National Laboratory. The BAR is designed to accumulate a polarized electron beam with a single-bunch charge up to 28 nC for subsequent acceleration in the Rapid Cycling Synchrotron and then injection into the Electron Storage Ring. Analytical models of longitudinal and transverse collective effects are developed using a broadband impedance model calibrated with the beam-based measurement results from NSLS VUV. The study evaluates the impact of resistive-wall and geometric impedances, assessing microwave and transverse mode coupling instabilities, bunch lengthening, and beam-induced heating.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Improvement of the AC orbit bump method of local kick factor measurement using reference bunches

Here we have improved the AC orbit bump technique of local kick factor measurement. This technique, developed at NSLS-II a few years ago, is based on local sine-wave excitation of the electron beam by four fast correctors adjacent to the impedance location. By implementing reference bunches and the time gate function of beam position monitors, we are now able to measure the AC orbits of bunches with different intensities simultaneously. This improvement allows us to obtain the impedance-driven orbit distortion in a single measurement, significantly improving the measurement accuracy and reducing the measurement time.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Improving Longitudinal Impedance of Inductive Inserts

Space charge compensation is essential to keeping the beam inside a ring such as PSR in the desired bunch form. The space charges of the ring will lead to the beam debunching, and the most prominent form of compensation for this is the use of RF to bunch the ring back. It has long been known however, that the impedance presented to the beam by its space charge could be compensated by a passive component. Such a passive component has been in use in PSR since 2000, but upgrading it could greatly improve the capabilities of the PSR. Additionally, the inserts presently used would require updating to match any changes in the beam pipe, both mechanically and to increase the space charge compensation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Project FELICIA - A probe to survey the RHIC magnet beampipe diameter for EIC beam screen insertion

The Electron Ion Collider (EIC) Hadron Storage Ring (HSR) will reuse many of the existing superconducting (SC) magnets of the RHIC storage rings. To comply with the beamline vacuum requirements in more demanding operational scenarios, the beampipe of the RHIC SC magnets will be equipped with low surface impedance, low secondary electron yield (SEY) beam screens. The installation of these beam screens will be done with the SC magnets as installed today, thus making it a critical operation for a timely EIC installation. The beam screen inner dimensions must be maximized to retain enough aperture to the beam. On the other hand, keeping enough clearance between the screen and the beampipe is critical to ensure a smooth beam screen installation. A survey probe was designed and built to measure the inner diameter of several RHIC SC magnets in-situ and provide critical data for the beam screen design optimization. This paper reports on the design of the probe and the results from the survey campaign.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

An Upgrade Path for the Fermilab Accelerator Complex

The completion of the PIP-II project and its superconducting linear accelerator will provide up to 1.2 MW of beam power to the LBNF/DUNE facility for neutrino physics. It will also be able to produce high-power beams directly from the linac that can be used for lower-energy particle physics experiments as well, such as directing beam toward the Muon Campus at Fermilab for example. Any further significant upgrade of the beam power to DUNE, however, will be impeded by the limitations of the present Booster synchrotron at the facility. To increase the power to DUNE by a factor of two would require a new accelerator arrangement to feed the Main Injector that does not include the Booster. In what follows, a path toward upgrading the Fermilab accelerator complex to bring the beam power for DUNE to 2.4 MW is presented, using a new rapid-cycling synchrotron plus an energy upgrade to the PIP-II linac. The path includes the ability to instigate a new lower-energy, very high-power beam delivery system for experiments that can address much of the science program presented by the Booster Replacement Science Working Group. It also allows for the future possibility to go beyond 2.4 MW up to roughly 4 MW from the Main Injector.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Nanoscale imaging of He-ion irradiation effects on amorphous TaO x toward electroforming-free neuromorphic functions

Resistive switching in thin films has been widely studied in a broad range of materials. Yet, the mechanisms behind electroresistive switching have been persistently difficult to decipher and control, in part due to their non-equilibrium nature. Here, we demonstrate new experimental approaches that can probe resistive switching phenomena, utilizing amorphous TaO x as a model material system. Specifically, we applied scanning microwave impedance microscopy and cathodoluminescence (CL) microscopy as direct probes of conductance and electronic structure, respectively. These methods provide direct evidence of the electronic state of TaO x despite its amorphous nature. For example, CL identifies characteristic impurity levels in TaO x , in agreement with first principles calculations. We applied these methods to investigate He-ion-beam irradiation as a path to activate conductivity of materials and enable electroforming-free control over resistive switching. However, we find that even though He-ions begin to modify the nature of bonds even at the lowest doses, the films' conductive properties exhibit remarkable stability with large displacement damage and they are driven to metallic states only at the limit of structural decomposition. Finally, we show that electroforming in a nanoscale junction can be carried out with a dissipated power of <20 nW, a much smaller value compared to earlier studies and one that minimizes irreversible structural modifications of the films. Importantly, the multimodal approach described here provides a new framework toward the theory/experiment guided design and optimization of electroresistive materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Coherent wiggler radiation impedance at the storage ring cooler for the EIC project

The Electron Ion Collider project is presently under design at Brookhaven National Laboratory. One of the options how to achieve an electron-proton high-luminosity of 10 34 cm –2 s –1 range, is the storage ring cooler concept, which is based on employing a significant amount of the damping wigglers. One of the main concerns, in achieving the required beam parameters, is the collective effects, especially the coherent synchrotron radiation impedance produced by the damping wigglers and its effect on the longitudinal beam dynamics. Low energy of the electrons, E o =149.6 MeV, small vacuum chamber aperture, b=15 mm, small bending radius and a big number of poles make the coherent synchrotron radiation simulations for the damping wiggler with D. Zhou’s CSRZ code, pretty challenging. The obtained numerical results have been compare with a theoretical approach of Stupakov and Zhou. The strong narrow-band impedance, due to a presence of the periodic poles and the vacuum chamber, have been identified and classified. To suppress or detune the high-Q resonance peaks, a design of the damping wiggler with a varied period of length is presented and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

A novel approach to RF power coupling in Radio-Frequency Quadrupole (RFQ) structures: built-in coaxial double-loop coupling port

Efficient and reliable RF power couplers in accelerating cavities require precise impedance matching and mechanical stability to ensure optimal beam energy transfer. In radio-frequency quadrupole (RFQ) accelerators, power is commonly delivered using waveguide iris or coaxial loop couplers. Iris couplers can handle high RF power but lack tunability, while coaxial loop couplers offer tuning flexibility but are limited in power handling and thermal performance. We propose a new RFQ power coupling concept utilizing a single input coaxial center-fed double-loop antenna built into a vane in an RFQ structure . The design integrates back-to-back loops into the RFQ vanes, fed by a TEM coaxial transmission line with standard 50-Ω characteristic impedance. The configuration can allow straightforward and easy ceramic window replacement without retuning, and coupling strength is adjusted with protruding tuning rods. Numerical simulations, performed with both a simplified RFQ model and the Spallation Neutron Source RFQ, demonstrate improved RF performance and reduced dipole mode excitation. The results establish the coaxial double-loop coupler as a practical alternative for high-power RFQ coupling applications.

Lee, Sung-Woo [ORNL] (ORCID:000000030915835X)↗
DOE OSTI2025

Improving Longitudinal Impedance of Inductive Inserts

In this article, we discuss methods for improving the longitudinal impedance of inductive inserts used for space charge compensation in the proton storage ring (PSR) at Los Alamos Neutron Science Center (LANSCE) Facility. The PSR relies on inductive inserts to counteract the capacitive impedance produced by the space charge of the proton beam, which can otherwise lead to beam debunching. Existing inductive inserts, which utilize Toshiba M4C21A ferrite, have been effective but require heating to reduce resistive components that can cause instabilities at higher frequencies. This article explores the potential of alternative ferrite materials, specifically National Magnetics C2050, to enhance the performance of these inserts by reducing the need for heating and minimizing resistive impedance. Through both analytical modeling and CST Particle Studio simulations, it is demonstrated that optimized ferrite materials and geometries can significantly improve space charge compensation while mitigating instability risks, ultimately enhancing the performance of the PSR.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Thermal Analysis and Simulations of the Abort Kicker Magnets Systems for the Electron-Ion Collider

The Abort Kicker Magnets system used in the current Relativistic Heavy Ion Collider (RHIC) to steer the circulating beam into the dump will be subjected to higher heat loads in the Electron-Ion Collider (EIC). After analyzing the existing abort kicker magnets and running thermal simulations in ANSYS it was concluded that they may not be suitable for use as-is in the future EIC due to heat and impedance concerns in the magnets. Possible solutions include adding a round titanium-coated ceramic beam tube to help solve the heat and impedance concerns, but this will reduce the limiting aperture of the kicker magnet. Another possible solution to meet all the performance requirements for EIC would be to add titanium-coated ceramic plates with water-cooling and tapered transitions that significantly improve the impedance and lower the heat in the magnets with less reduction to the aperture.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

NSLS-II longitudinal impedance budget

From the beginning of the NSLS-II project, the vacuum chamber of the NSLS-II storage ring has been optimized to reduce its impedance. The optimization, performed in close collaboration with the Diagnostic, Vacuum, RF, and Mechanical Engineering groups, has been achieved via calculating the impedance of the vacuum chamber components with the use of both analytical and numerical tools, with the numerical computations carried out with the GdfidL code. Fore reliable NSLS-II operation with the total beam current of 500 mA, each component of the vacuum chamber has been individually optimized to minimize the beam-induced heating and to prevent single-bunch and coupled-bunch instabilities. In this study, the impedance calculation and optimization know-how are summarized for all the chamber components, and the total longitudinal impedance budget is analyzed. As a result of this extensive research and engineering effort, the design beam current of 500 mA has been recently accumulated in NSLS-II without any major problem caused by collective effects.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Current-Pulse Excitation of Beam Breakup in Scorpius

Perhaps the most dangerous instability for electron linear induction accelerators (LIA) is the beam breakup (BBU) instability. For flash-radiography LIAs like DARHT or Scorpius it is particularly troublesome, because low-level high-frequency BBU motion can blur the source spot. Theoretically, the number of e-foldings Γ of exponential BBU growth in an LIA is linearly proportional to beam current I, number of accelerating cells N, and transverse coupling impedance Z ⊥ , and inversely proportional to the strength of magnetic focusing B.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Proton Dynamics Scenarios in the Integrable Optics Test Accelerator (IOTA) at Fermilab

The Integrable Optics Test Accelerator (IOTA) at Fermilab provides a versatile platform for studying the interplay of space-charge, impedance, and non-linear optics in high-intensity hadron beams within synchrotrons and storage rings. This report examines the parameters and dynamics of 2.5~MeV proton beam operations in two configurations of the bare IOTA lattice: one for demonstrating Non-linear Integrable Optics with the Danilov-Nagaitsev magnet, and the other for use with electron cooling. We offer order-of-magnitude estimates of the transverse emittance growth rate as a function of beam intensity, highlighting contributions from residual gas scattering, intra-beam scattering, and space-charge effects. Under nominal conditions, the beam lifetime is projected to be less than 7~minutes at low intensity with the current vacuum quality, and fewer than 100,000~turns at high intensity due to strong space-charge effects. The calculations presented here will guide strategies to mitigate emittance growth and inform future IOTA experiments.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Capture Cavities for the CW Polarized Positron Source Ce+BAF

The initial design of the capture cavities for a continuous wave (CW) polarized positron beam for the Continuous Electron Beam Accelerator Facility (CEBAF) up-grade at Jefferson Lab is presented. A chain of standing wave multi-cell copper cavities inside a solenoid channel are selected to capture positrons in CW mode. The cavity shunt impedance is surveyed by tuning the cavity geometry while considering accommodating large phase space distribution positron beams with large beam pipe radius while ensuring a large enough passband mode separation. The RF field wall loss power and maximum wall loss power density are considered in cavity and waveguide design. A range of design parameters are given for larger system optimization when the capture cavities are considered together with thermal calculation and beam dynamics in next phase of work.

Wang, S.↗
DOE OSTI2021

A BEAM SCREEN TO PREPARE THE RHIC VACUUM CHAMBER FOR EIC HADRON BEAMS: CONCEPTUAL DESIGN AND REQUIREMENTS

The Electron Ion Collider (EIC) Hadron Storage Ring (HSR) will use the existing Relativistic Heavy Ion Collider storage rings, including the superconducting magnet arcs [1]. The vacuum chambers in the superconducting magnets and the cold mass interconnects were not designed for EIC beams and so must be updated to reduce resistive-wall heating and to suppress e-clouds. To do so without compromising the EIC luminosity goal, a stainless steel beam screen with colaminated copper and a thin layer of amorphous carbon will be installed. This paper describes the main requirements that our solution for the hadron ring vacuum chamber needs to satisfy, including impedance, aperture limitations, vacuum, thermal and structural stability, mechanical design, installation and operation. The conceptual design of the beam screen currently under development is introduced.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Recent Beam Stability Analysis for the EIC

This document summarizes work done in WBS 6.02.02 during FY23. Additional details can be found in the EIC overview paper presented at IPAC’23 [1], and the references therein. Progress has been made in the ESR and HSR lattice design, dynamic aperture optimization, and the RCS lattice design. The impedance and Collective effects are progressing and include the impedance optimization process of the vacuum systems for RCS, HSR, and ESR; collective effects studies; collective effects and beam-beam interaction; coupled bunch instabilities and the crab cavities; low-level RF feedback system design and beam-ion instability. The reversed phasing RF system has been numerically studied for the ESR to mitigate Robinson instability and demonstrate reliable stable beam operation. Various codes, including C++, SPACE [2], ELEGANT [3], and Mbtrack2 [4] have been employed to benchmark the results. The simulation of HSR bunch splitting with beam loading has been performed at 275 GeV energy. The evaluation of Beam Position Monitors aimed to validate their expected performance, with the primary objective being to verify their accuracy. Calculations of Electron Polarization in the ESR, RCS, and HSR are showing good progress. In the RCS, preliminary studies indicate excellent polarization transmission over intrinsic spin resonances, achieving over 90% transmission with improved performance compared to the previous lattice. Preliminary simulations in the ESR indicate encouraging results in minimizing depolarization and improving equilibrium polarization.

43 PARTICLE ACCELERATORS↗