Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “BUNCHES”

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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Electron Bombardment of ZnTe EO Bunch Charge Detector for Signal Lifetime Studies in Radiation Environment

Electro-optic detection of bunch charge distribution utilizing the nonlinear Pockel's and Kerr effect of materials has been implemented at various facilities as a method of passive detection for beam preservation throughout characterization. Most commonly, the inorganic II-VI material ZnTe is employed due to it's strong Pockel's EO effect and relatively high temporal resolution (~90 fs). Despite early exploration of radiation damage on ZnTe in exploration of semi-conductor materials in the 1970's, full characterization of EO response over radiation lifetime has yet to be performed. The following poster presents a method for ZnTe crystal characterization studies throughout radiation exposure at various energies and dosages by analyzing the changes in index of refraction including bulk uniformity, and THz signal response changes.

Williams, J.↗
DOE OSTI2021

Impact of Coherent Beam-Beam Interaction on the Collisionless Damping of the Transverse Coupled-Bunch Instability

In the EIC design, at high average-current operation, the transverse coupled-bunch instability (TCBI) induced by the long-range transverse resistive-wall wakefield in the electron storage ring (eSR) has a fast growth rate and requires efficient mitigation. A natural mitigation mechanism is provided by the beam-beam interaction at the interaction point (IP), which gives a strong Landau damping for the TCBI in the eSR. In this study, using a simplified simulation model, we investigate how this Landau damping from the beam-beam interaction behaves when the coherent beam-beam interaction at IP is considered. Our method and results will be presented in this paper.

Li, R.↗
DOE OSTI2023

Microbunching Gain Evaluation of Bunch Stretcher Designs

The planned Electron Ion Collider (EIC) has an Energy Recovery Linac (ERL) which provides Strong Hadron Cooling (SHC) in order to control the beam quality of the hadrons. This requires that the electron beam delivered to the cooling section be minimally perturbed by the preceding bunch stretcher necessary in the 100 GeV configuration. This paper evaluates different stretcher designs for the SHC ERL, based on current design requirements.

Deitrick, Kirsten↗
DOE OSTI2024

SINGLE BUNCH TRACKING ON THE TEN-PASS ER@CEBAF ENERGY RECOVERY BEAMLINE

The proposed ten-pass energy recovery linac (ERL) demonstration (five accelerating, five decelerating) at the CEBAF accelerator, ER@CEBAF, involves a multi-GeV en- ergy range of a continuous electron beam. New CEBAF transverse optics were designed for this ERL demonstration. This redesign incorporates additional components in Arc A, including a path length chicane and new quadrupoles to ensure proper dispersion localization. The new five energy recovery passes with a shared arc transport scheme chal- lenge the overall beamline optics design, including large beta functions in the CEBAF spreaders and recombiners. Here we discuss results of bunch tracking performed using the elegant tracking code for the full ER@CEBAF beamline

Neththikumara, I.↗
DOE OSTI2020

Ultrashort Laser Pulse Shaping and Characterization for Tailored Electron Bunch Generation

Temporally shaped laser pulses are desirable in various applications including emittance reduction and beam-driven acceleration. Pulse shaping techniques enable flexible controls over the longitudinal distribution of electron bunches emitted from the photocathode. While direct manipulation and measurement of an ultrashort pulse can be challenging in the time domain, both actions can be performed in the frequency domain. In this paper, we report the study and development of laser shaper and diagnostics at Argonne Wakefield Accelerator (AWA). Simulations of the shaping process for several sought-after shapes are presented along with the temporal diagnosis. Status of the experiment at the AWA facility is also discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Single-Bunch Instabilities at the Fermilab Recycler Ring

Understanding and characterizing collective instabilities is critical for high-intensity operation at the Fermilab Recycler Ring. This work presents an application of the the Nested Head-Tail (NHT) formalism for modeling single-bunch transverse instabilities, incorporating analytical solutions to the resistive wall impedances in the absence of space charge. Predicted growth rates and mode structures are benchmarked against PyHEADTAIL simulations and ongoing experimental measurements. The experimental program includes studies of bare-machine instabilities at different machine parameters. These results support the understanding of naturally-occurring instabilities in the Recycler and contribute to the development of predictive tools for beam stability in future high-intensity configurations.

Gonzalez-Ortiz, C. [Fermilab]↗
DOE OSTI2011

Much Ado about Microbunching: Coherent Bunching in High Brightness Electron Beams

The push to provide ever brighter coherent radiation sources has led to the creation of correspondingly bright electron beams. With billions of electrons packed into normalized emittances (phase space) below one micron, collective effects may dominate both the preservation and use of such ultra-bright beams. An important class of collective effects is due to density modulations within the bunch, or microbunching. Microbunching may be deleterious, as in the case of the Microbunching Instability (MBI), or it may drive radiation sources of unprecedented intensity, as in the case of Free Electron Lasers (FELs). In this work we begin by describing models of microbunching due to inherent beam shot noise, which sparks both the MBI as well as SLAC's Linac Coherent Light Source, the world's first hard X-ray laser. We first use this model to propose a mechanism for reducing the inherent beam shot noise as well as for predicting MBI effects. We then describe experimental measurements of the resulting microbunching at LCLS, including optical radiation from the MBI, as well as the first gain length and harmonic measurements from a hard X-ray FEL. In the final chapters, we describe schemes that use external laser modulations to microbunch light sources of the future. In these sections we describe coherent light source schemes for both both linacs and storage rings.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Longitudinal Bunch Pattern Measurements through Single Photon Counting at SPEAR3

The Stanford Synchrotron Radiation Lightsource (SSRL), a division of SLAC National Accelerator Laboratory, is a synchrotron light source that provides x-rays for experimental use. As electrons are bent in the storage ring, they emit electromagnetic radiation. There are 372 different buckets which electrons can be loaded into. Different filling patterns produce different types of x-rays. What is the bunch pattern at a given time? Which filling pattern is better? Are there any flaws to the current injection system? These questions can be answered with this single photon counting experiment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Short-Bunch Stacking Mode for The PSR: An Overview

The overall upgrade involving a short-bunch PSR mode proceeds from the WNRproposed-project main goals, namely greatly enhancing the ability of WNR to measure neutron cross-sections and reaction dynamics, in a wide neutron-energy range (from thermal to ~100 MeV.) Such measurements, with currently (and surprisingly) sparse data, are of strong interest to several areas of application including weapons physics, nuclear science and engineering, astrophysics, homeland defense, and isotope production. As well as accelerator enhancement, the project plans to enhance radiochemistry facilities, revive the shelved radioactive-species-isotope separator, create a new faster version (TANGO) of the DANCE detector used at LANSCE, and enhance the WNR target and data-taking infrastructure. The cost of all this has not been well established and funding (so far negligible) is needed to achieve a credible figure. A proposal has been sent to NNSA and is currently under review.

Accelerator Design, Technology, and Operations↗
DOE OSTI2012

First-order beam dynamics and RF parameters for the PSR short-bunch ("pulse-stacking") mode

Here we mainly discuss the longitudinal ring beam dynamics and RF control for the bunching needed to maintain the short (a few nanoseconds) proton pulses required by the Weapons Neutron Research Center (WNR) for measurement of neutron cross sections and reaction dynamics, as specified in the recent upgrade proposal known as “Pulse Stacking.” Single micropulses, each containing 6x10 8 protons, are to be delivered to the Proton Storage Ring (PSR) from the LANSCE linac and successively overlaid in from 1 to 4 RF buckets per ring turn until a maximum number of particles in the bucket is achieved. This is distinct from the currently used long-pulse mode in which the bucket equals the ring circumference and a 201-MHz micropulse stream is injected at each turn to fill ¾ of the bucket to obtain pulses ~270 ns long.

Accelerator Design, Technology, and Operations↗
DOE OSTI2016

Analytical Formulas for Short Bunch Wakes in a Flat Dechirper

We develop analytical models of the longitudinal and transverse wakes, on and off axis for realistic structures, and then compare them with numerical calculations, and generally find good agreement. These analytical "first order" formulas approximate the droop at the origin of the longitudinal wake and of the slope of the transverse wakes; they represent an improvement in accuracy over earlier, "zeroth order" formulas. In example calculations for the RadiaBeam/LCLS dechirper using typical parameters, we find a 16% droop in the energy chirp at the bunch tail compared to simpler calculations. With the beam moved to 200 m from one jaw in one dechiper section, one can achieve a 3 MV transverse kick differential over a 30 m length.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Instability of a witness bunch in a plasma bubble

The stability of a trailing witness bunch, accelerated by a plasma wake accelerator (PWA) in a blow-out regime, is discussed. The instability growth rate as well as the energy spread, required for BNS damping, are obtained. A relationship between the PWA power efficiency and the BNS energy spread is derived.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Can YAG screen accept LEReC bunch train?

LEReC RF diagnostic beamline is supposed to accept 250 us long pulse trains of 1.6 MeV – 2.6 MeV (kinetic energy) electrons. This beamline is equipped with YAG profile monitor. Since we are interested in observing only the last macro bunch in the train, one of the possibilities is to install a fast kicker and a dedicated dump upstream of the YAG screen (and related diagnostics equipment). This approach is expensive and challenging from engineering point of view. Another possibility is to send the whole pulse train to the YAG screen and to use a fast gated camera (such as Imperex B0610 with trigger jitter under 60ns) to observe the image from the last pulse only. In this paper we study the feasibility of the last approach.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Polarized e-bunch acceleration at Cornell RCS: Tentative tracking simulations

An option as an injector into eRHIC electron storage ring is a rapid-cyclic synchrotron (RCS). Rapid acceleration of polarized electron bunches has never been done, Cornell synchrotron might lend itself to dedicated tests, which is to be first explored based on numerical investigations. This paper is a very preliminary introduction to the topic.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Vertical Coupled Bunched-Beam Breakup Due to Resistive-Wall Wake

We estimate in this note the magnitude of the vertical rigid coupled-bunch mode of Courant and Sessler [1] at NSLS-II. If the proposed mini gap undulators (MGUs) are operated at the room temperature, the threshold current is calculated to be about 10 mA; this is to be compared to the designed beam current of 500 mA. If the MGUs are operated at 4.2 Kelvins, the threshold current is about 120 mA. In either case, a feedback damper is needed in order to operate NSLS-II at 500 mA.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Emittance growth generated by bunched beam electron cooling

The low energy RHIC electron cooling (LEReC) project at Brookhaven employs a linac to supply electrons with kinetic energies from 1.6 to 2.6 MeV. Along with cooling the stored ion beam the electron bunches create a coherent space charge field which can cause emittance growth. This process is investigated both analytically and through simulation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Vertical Coupled Bunched-Beam Breakup Due to Resistive-Wall Wake

We estimate in this note the magnitude of the vertical rigid coupled-bunch mode of Courant and Sessler at NSLS-II. If the proposed mini gap undulators (MGUs) are operated at the room temperature, the threshold current is calculated to be about 10 mA; this is to be compared to the designed beam current of 500 mA. If the MGUs are operated at 4.2° Kelvins, the threshold current is about 120 mA. In either case, a feedback damper is needed in order to operate NSLS-II at 500 mA.

36 MATERIALS SCIENCE↗