Search NASA⌕ Search

SEARCH · Search NASA

Results for “Beam halos”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Transfer Line at Fermilab

Beam loss in high-intensity H- linacs, such as the PIP-II linac at Fermilab, is a critical challenge that requires comprehensive study and understanding to ensure efficient and safe operation. This study explores the various beam loss mechanisms encountered in the PIP-II linac and its beam transfer line, drawing parallels from other high-intensity H- linacs. Key loss mechanisms include residual gas stripping, where H- ions interact with residual gas molecules leading to electron detachment; field stripping, caused by the interaction of H- ions with magnetic fields; and intra-beam stripping, resulting from interactions within the beam itself. Beam halo formation, particularly due to Twiss function mismatch, is another significant source of beam loss, which can be exacerbated by Landau damping mechanisms. Adhering to the 1 W/m loss criterion is essential to maintain hands-on maintenance capability and ensure the longevity of the accelerator components. By understanding these mechanisms and implementing targeted mitigation strategies, the PIP-II linac can achieve its design goals while maintaining safe and efficient operations.

Pathak, Abhishek↗
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 OSTI2026

First experimental report of nonlinear collimator in the SuperKEKB

SuperKEKB collimator system protects the superconducting final focusing magnets (QC1 and QC2) from quenching caused by beam halo particles. For effective shielding, the minimum aperture of vertical collimators is set smaller than the physical aperture of QC1. However, such collimators become dominant sources of beam coupling impedance, which can limit the maximum beam current due to impedance-driven instabilities. To address this issue, a nonlinear collimator (NLC) was introduced in February 2024. NLC is designed to reduce both beam backgrounds and collimator impedance, thereby suppressing beam instabilities caused by short-range wakefields. In this paper, we describe the results on impedance effects, beam background reduction, and beam lifetime when the nonlinear collimation system is turned on and off. These results validate the NLC concept and offer a promising approach for future high-luminosity colliders.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Electron lenses in RHIC: status and prospects

Two electron lenses are installed in Relativistic Heavy Ion Collider (RHIC). They were used as operational head-on beam-beam compensators in proton-proton collisions, with Gaussian transverse electron beam profiles. One of the lenses was also used with a hollow transverse profile to test hadron beam halo removal under various conditions. Although presently not in the design, the lenses may find applications in the Electron-ion Collider (EIC) for either collimation or beam-beam mitigation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Measurements of the Five-Dimensional Phase Space Distribution of an Intense Ion Beam

No simulation of intense beam transport has accurately reproduced measurements at the level of beam halo. One potential explanation of this discrepancy is a lack of knowledge of the initial distribution of particles in six-dimensional (6D) phase space. A direct 6D measurement of an ion beam was recently performed at the Spallation Neutron Source (SNS) Beam Test Facility (BTF), revealing nonlinear transverse-longitudinal correlations in the beam core that affect downstream evolution. Unfortunately, direct 6D measurements are limited in resolution and dynamic range; here, we discuss the use of three slits and one screen to measure a 5D projection of the 6D phase space distribution, overcoming these limitations at the cost of one dimension. We examine the measured 5D distribution before and after transport through the BTF and compare to particle-in-cell simulations. We also discuss the possibility of reconstructing the 6D distribution from 5D and 4D projections.

Hoover, Austin↗
DOE OSTI2021

McMillan electron lens in a system with space charge

Space charge (SC) forces of a circulating beam in a ring have both linear (defocusing) and nonlinear components, due to a nonuniform beam distribution. The linear component of SC forces produces a betatron tune shift, which is the largest for a zero-amplitude particle, while the nonlinear component produces an amplitude-dependent betatron tune spread. These SC effects are responsible for several undesirable phenomena in accelerators: emittance growth, particle losses, beam halo, etc. In this paper, we investigate the possibility to mitigate the distributed SC forces by a thin McMillan lens, providing an axially-symmetric kick, which is qualitatively opposite to the accumulated effect of beam's own SC. Experimentally, the proposed concept can be tested in Fermilab's IOTA ring. A thin McMillan lens can be implemented by a short (70) insertion of an electron beam with a specifically chosen density distribution in transverse directions. In this article, to test if McMillan lenses can reduce the tune spread induced by SC, we make several simulations with a 6-D particle tracking code, Synergia. We choose such beam and lattice parameters that the SC tune spread is roughly 0.5 and the emittance growth due to the half-integer resonance is clearly observed without the SC compensation. Then, we focus on reducing the emittance growth by adjusting the bare betatron tunes using the ring quadrupoles, and reducing the tune spread by the McMillan lenses. The results of reducing a large tune spread (≈ 0.5), reported here, are not perfect, but substantial. There is still room for further investigation. The simulations performed so far in this work indicate that McMillan lenses can cope with an SC tune spread of ≈ 0.1 per lens.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Final Physics Design of Proton Improvement Plan-II at Fermilab

This paper presents the final physics design of the Proton Improvement Plan-II (PIP-II) at Fermilab, focusing on the linear accelerator (Linac) and its beam transfer line. We address the challenges in longitudinal and transverse lattice design, specifically targeting collective effects, parametric resonances, and space charge nonlinearities that impact beam stability and emittance control. The strategies implemented effectively mitigate space charge complexities, resulting in significant improvements in beam quality—evidenced by reduced emittance growth, lower beam halo, decreased loss, and better energy spread management. This comprehensive study is pivotal for the PIP-II project's success, providing valuable insights and approaches for future accelerator designs, especially in managing nonlinearities and enhancing beam dynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Final Physics Design of Proton Improvement Plan-II At Fermilab

This paper presents the final physics design of the Proton Improvement Plan-II (PIP-II) at Fermilab, focusing on the linear accelerator (Linac) and its beam transfer line. We address the challenges in longitudinal and transverse lattice design, specifically targeting collective effects, parametric resonances, and space charge nonlinearities that impact beam stability and emittance control. The strategies implemented effectively mitigate space charge complexities, resulting in significant improvements in beam quality -- evidenced by reduced emittance growth, lower beam halo, decreased loss, and better energy spread management. This comprehensive study is pivotal for the PIP-II project's success, providing valuable insights and approaches for future accelerator designs, especially in managing nonlinearities and enhancing beam dynamics.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Theoretical formulation of phase space microbunching instability in the presence of intrabeam scattering for single-pass or recirculation accelerators

Microbunching instability (MBI) has been one of the most challenging issues in designs of high-brightness beam transport lines for single-pass or recirculating accelerators. Although the intrabeam scattering (IBS) has long been studied in lepton or hadron storage rings as a slow diffusion process or in high-intensity proton linear accelerators as one mechanism for the beam halo, the effects of IBS on single-pass or recirculating electron accelerators have drawn attention only in the recent two decades due to emergence of linac-based or energy-recovery-linac-based fourth-generation light sources, which require high-quality electron beams during the beam transport. In this paper we develop a theoretical formulation of microbunching instability in the presence of IBS for single-pass or recirculation accelerators. To quantify MBI with inclusion of IBS, we start from the Vlasov-Fokker-Planck (VFP) equation, combining both collective interactions and incoherent IBS effects. The linearized VFP equation and the corresponding friction and diffusion coefficients are derived. The evolutions of the resultant density and energy modulations are formulated as a set of coupled integral equations. The theoretical formulation is then applied to a recirculating beamline design. The results from the semianalytical calculation are compared and show good agreement with massive particle tracking simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Modeling LANSCE Line D and RI Beamlines in Elegant and Impact-T

This technical report describes models in Elegant and Impact-T of two LANSCE high-energy beamlines: LineD and Ring Injection. These two beamlines transport the 800 MeV H- beam from the exit of the 805 MHz Linac to the entrance of the PSR. Computer models of all LANSCE high-energy beamlines exist in Transport but include a limited model of the space charge forces. A motivation for using Elegant as an optional beam dynamics code is that the existing model of the PSR is in Elegant, therefore enabling the modeling of the full beam injection scheme. Also, Elegant is a modern code being used by a large accelerator physics community which makes the calculation results more reliable. The drawback is that Elegant has also a limited space charge force model. Therefore, we have opted to include the Particle-In-Cell (PIC) code Impact-T as an alternate beam dynamics code to verify the Elegant calculations. We will use the new Line D and RI models to study beam halo in the transport leading into the PSR, and to evaluate collimation schemes as part of the PSR upgrade. The new models can also be readily used in support of other LANSCE activities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

LAMP DTL Scoping Studies (Technical Report)

The present studies are based on the preliminary design efforts, and on the Scoping Studies of the “Strawman” design of LAMP front-end upgrade, referred in the text below to as “Feb.2024 Iteration”, presented in. The main accomplishment of present studies was substantial increase of the fidelity of the beam dynamics simulations in the proposed drift tube linac (DTL). The main accent was on development of the methodology for calculation of the longitudinal (synchrotron) and transverse (betatron) oscillations frequencies (phase advance per focusing period) values and providing the accelerating structure focusing lattice that has safe parameters of such oscillations to avoid unwanted emittance growth and possible beam halo formation. The resulting values of the oscillations phase advances are presented in Table 1, and in Figure 5 in the main body of the report. Special efforts were made to achieve the RF power consumption within limits of the existing RF power system and make sure that DTL fits in the existing tunnel. The LAMP scope does not suggest any additional building and/or tunnel construction. Table 1 summarizes some of these results, as well as Table 3 in the main body of the report.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

The Trigger System of ICARUS-T600 Detector at Fermilab

The ICARUS-T600 liquid argon (LAr) time projection chamber (TPC) detector is currently deployed as a far detector of the Short Baseline Neutrino (SBN) program at Fermilab (USA) to search for a possible LSND-like sterile neutrino signal at $\Deltam^2 \approx 1eV^2$ with the Booster (BNB) and Main Injector (NuMI) Neutrino Beams. A global physical event rate of $\approx 0.6$ Hz, including the genuine neutrino interactions in LAr, beam halos and cosmic interactions inside the proton pulse time windows, is expected, roughly corresponding to $\approx 4$ PB of data for the total 6.6 $10^{20}$ pot exposure if the full ICARUS-T600 detector is readout ($\approx 200$ MB event size). The designed trigger system described here will collect the genuine neutrino interactions with a $\approx 95$\% expected efficiency.

Copello, S. [INFN, Pavia]↗
DOE OSTI2021

Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses

We present the results of numerical simulations and experimental studies about the effects of resonant and random excitations on proton losses, emittances, and beam distributions in the Large Hadron Collider (LHC). In addition to shedding light on complex nonlinear effects, these studies are applied to the design of hollow electron lenses (HEL) for active beam halo control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable amount of energy will be stored in the beam tails. To control and clean the beam halo, the installation of two hollow electron lenses, one per beam, is being considered. In standard electron-lens operation, a proton bunch sees the same electron current at every revolution. Pulsed electron beam operation (i.e., different currents for different turns) is also considered, because it can widen the range of achievable halo removal rates. For an axially symmetric electron beam, only protons in the halo are excited. If a residual field is present at the location of the beam core, these particles are exposed to time-dependent transverse kicks and to noise. We discuss the numerical simulations and the experiments conducted in 2016 and 2017 at injection energy in the LHC. The excitation patterns were generated by the transverse feedback and damping system, which acted as a flexible source of dipole kicks. Proton beam losses, emittances, and transverse distributions were recorded as a function of excitation patterns and strengths. The resonant excitations induced rich dynamical effects and nontrivial changes of the beam distributions, which, to our knowledge, have not previously been observed and studied in this detail. We conclude with a discussion of the tolerable and achievable residual fields and proposals for further studies.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Progress towards halo modeling at the SNS Beam Test Facility

The SNS beam test facility is a model of the SNS front end (source through medium-energy transport). On-going work at the BTF focuses on accurate modeling of the beam distribution to enable the prediction of halo losses (>100 parts per million). This presentation will discuss the latest progress towards this goal, including recent results after a reconfiguration of the test beamline. Good agreement within the 90% beam core is shown for a 30 mA beam at 2.5 MeV.

Ruisard, Kiersten↗
DOE OSTI2026

Exploring Causes of Beam Loss at CEBAF

At Jefferson Lab, the Continuous Electron Beam Accelerator (CEBAF) features a unique design with two linear accelerators and two arc sections allowing for multiple turns of the electron beam, as well as four experimental end stations. This topology leads to increased beam losses, especially in the spreader and recombiner regions connecting the arcs to the linacs and in the extraction regions connecting the experimental end stations to the accelerator. These losses result in equipment activation and operational interruptions. Recent upgrades to the facility’s diagnostic systems, including the addition of xenon ion chambers, have provided higher-resolution data regarding these loss events. Building on this improved observational capability, we are developing a simulation framework using optics codes and the Geant4-based BDSIM to model beam extinction and halo formation in these regions. This work aims to correlate simulation results with experimental data to isolate the causes of beam loss and inform future machine tuning strategies. We present a summary of conclusions drawn from recent operational studies and outline a plan to model the beam loss and validate the simulations.

Matthews, C. [Old Dominion Univ., Norfolk, VA (Uni↗
DOE OSTI2021

Nonlinear dynamics of proton beams with hollow electron lens in the CERN high-luminosity LHC

The design stored beam energy in the CERN high-luminosity large hadron collider (HL-LHC) upgrade is about 700 MJ, with about 36 MJ in the beam tails, according to estimates based on scaling considerations from measurements at the LHC. Such a large amount of stored energy in the beam tails poses serious challenges on its control and safe disposal. In particular, orbit jitters can cause significant losses on primary collimators, which can lead to accidental beam dumps, magnet quenches, or even permanent damage to collimators and other accelerator elements. Thus, active control of the diffusion speed of halo particles is necessary and the use of hollow electron lenses (HELs) represents the most promising approach to handle overpopulated tails at the HL-LHC. HEL is a very powerful and advanced tool that can be used for controlled depletion of beam tails, thus enhancing the performance of beam halo collimation. For these reasons, HELs have been recently included in the HL-LHC baseline. In this paper, we present detailed beam dynamics calculations performed with the goal of defining HEL specifications and operational scenarios for HL-LHC. The prospects for effective halo control in HL-LHC are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗