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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.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Beam manipulation and acceleration with Dielectric-Lined Waveguides

The development of next-generation TeV+ electron accelerators will require either immense footprints based on conventional acceleraton techniques or the development of new higher{gradient acceleration methods. One possible alternative is beam-driven acceleration in a high-impedance medium such as a dielectric-lined-waveguide (DLW), where a highcharge bunch passes through a DLW and can excite gradients on the order of GV/m. An important characteristic of this acceleration class is the transformer ratio which characterizes the energy transfer of the scheme. This dissertation discusses alternative methods to improve the transformer ratio for beam-driven acceleration and also considers the use of DLWs for beam manipulation at low energy.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Dielectric-Based Wakefield Power Extractor

In the Two Beam Accelerator (TBA), wakefield power extractors which extract high power RF from a high current beam are used to power high gradient accelerating structures. A dielectric-based Wakefield Power Extractor (DWPE) is one option in addition to the metallic structures considered previously, like the CLIC PETS (Power Extraction and Transfer Structure). 7.8 GHz and 26 GHz DWPE prototypes have been successfully built and tested at the Argonne Wakefield Accelerator (AWA) facility. We are currently designing an X-band version for a potential application with the CLIC beam. In this article, we report on test results of the 26 GHz DWPE and the preliminary design of the X-band structure. Future plan and possible difficulties in the development of DWPEs are also discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Simulation of a cascaded longitudinal space charge amplifier for coherent radiation generation

Longitudinal space charge (LSC) effects are generally considered as harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. It was pointed out, however, that such \micro-bunching instabilities" could be potentially useful to support the generation of broadband coherent radiation. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we augment these previous investigations by combining a grid-less space charge algorithm with the popular particle-tracking program elegant. This high-fidelity model of the space charge is used to benchmark conventional LSC models. We then employ the developed model to optimize the performance of a cascaded longitudinal space charge amplifier using beam parameters comparable to the ones achievable at Fermilab Accelerator Science & Technology (FAST) facility currently under commissioning at Fermilab.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Overview and Lessons Learned of the Jefferson Lab Cryomodule Production for the CEBAF 12 GeV Upgrade

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is nearing completion of an energy upgrade from 6 to 12 GeV. An integral part of the upgrade is the addition of ten new cryomodules, each consisting of eight seven-cell superconducting radio-frequency (SRF) cavities. An average performance of 100+MV of acceleration per cryomodule is needed to achieve the 12 GeV beam energy goal. The production methodology was for industry to provide and deliver the major components to Jefferson Lab, where they were tested and assembled into cryomodules. The production process begins with an inspection upon receiving of all major components followed by individual performance qualification testing. The SRF cavities received their final chemical processing and cleaning at Jefferson Lab. The qualified components along with all associated hardware and instrumentation are assembled, tested, installed into CEBAF and run through an integrated system checkout in preparation for beam operations. The production process is complete and one of the first completed cryomodules has successfully produced 108 MV of acceleration with a linac beam current of 465 {micro}A.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

PARTICULATE STUDY OF NEG PUMPS IRRADIATED IN THE CEBAF TUNNEL

Non-evaporable getter (NEG) pumps are being used to maintain ultra-high vacuum in the beamline of superconducting radio-frequency (SRF) accelerators, such as the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Because of the sensitivity of the performance of SRF cavities to particulate contamination, it is important to evaluate the integrity of the NEG material after exposure to high radiation during beam operation. The particulate from two NEG pumps based on ZAO® getter alloy was measured with a particle counter in a clean-room. The pumps were assembled onto a hermetically sealed setup which was placed in the CEBAF tunnel. The setup was exposed to 24 h beam operation for ~ 230 days. The total gamma-rays dose measured on the test setup was ~ 1.6 Mrad. The total neutron dose measured at ~ 75 cm of the test setup was ~ 11 krad. The particulate count from the two pumps was measured again in the clean-room after irradiation. Whereas an increase of particulate counts was measured, compared to before irradiation, subsequent measurements indicate the absence of systematically loose particulate. The pumping speed of one of the irradiated pumps was also measured to be consistent with that of a non-irradiated one, corroborating the absence of significant damage to the ZAO® NEG material due to irradiation.

Ciovati, G. [Thomas Jefferson National Accelerator↗
DOE OSTI2026

PARTICULATE STUDY OF NEG PUMPS IRRADIATED IN THE CEBAF TUNNEL

Non-evaporable getter (NEG) pumps are being used to maintain ultra-high vacuum in the beamline of superconducting radio-frequency (SRF) accelerators, such as the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Because of the sensitivity of the performance of SRF cavities to particulate contamination, it is important to evaluate the integrity of the NEG material after exposure to high radiation during beam operation. The particulate from two NEG pumps based on ZAO® getter alloy was measured with a particle counter in a clean-room. The pumps were assembled onto a hermetically sealed setup which was placed in the CEBAF tunnel. The setup was exposed to 24 h beam operation for ~ 230 days. The total gamma-rays dose measured on the test setup was ~ 1.6 Mrad. The total neutron dose measured at ~ 75 cm of the test setup was ~ 11 krad. The particulate count from the two pumps was measured again in the clean-room after irradiation. Whereas an increase of particulate counts was measured, compared to before irradiation, subsequent measurements indicate the absence of systematically loose particulate. The pumping speed of one of the irradiated pumps was also measured to be consistent with that of a non-irradiated one, corroborating the absence of significant damage to the ZAO® NEG material due to irradiation.

Ciovati, Gianluigi [Thomas Jefferson National Acce↗
DOE OSTI2013

Field Emission and Consequences as Observed and Simulated for CEBAF Upgrade Cryomodules

High gamma and neutron radiation levels were monitored at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) after installation of new cavity cryomodules and initial test runs in the frame of the ongoing 12 GeV upgrade program. The dose rates scaled exponentially with cavity accelerating fields, but were independent of the presence of an electron beam in the accelerator. Hence, field emission (FE) is the source of origin. This has led to concerns regarding the high field operation (100 MV per cryomodule) in the future 12 GeV era. Utilizing supercomputing, novel FE studies have been performed with electrons tracked through a complete cryomodule. It provides a principal understanding of experimental observations as well as ways to mitigate FE as best as practicable by identification of problematic cavities.

Marhauser, Frank↗
DOE OSTI2011

Studies of spin-orbit correlations at JLAB

Studies of single spin asymmetries for pion electroproduction in semi-inclusive deep-inelastic scattering are presented using the polarized \sim6 GeV electrons from at the Thomas Jefferson National Accelerator Facility (JLab) and the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) with the Inner Calorimeter. The cross section versus the azimuthal angle {\phi}_h of the produced neutral pion has a substantial sin {\phi}_h amplitude. The dependence of this amplitude on Bjorken x_B and on the pion transverse momentum is extracted and compared with published data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Ingot Nb based SRF technology for the International Linear Collider

The International Linear Collider (ILC) is anticipated to be built as the next energy-frontier electron-positron colliding accelerator with a global effort in particle physics. Niobium based Superconducting Radio-Frequency (SRF) technology is required to provide beam-accelerating structure with elliptical cavity strings to linearly accelerate the electron and positron beams up to 250 GeV and to realize a center-of-mass energy of 500 GeV in collisions. The accelerator design and R&D efforts progressed, and the ILC Technical Design Report (ILC-TDR) was published in 2013. Niobium will take a critical role to generate electric field gradient with a frequency of 1.3 GHz, for accelerating the beam with the best efficiency, in energy balance, using RF superconductivity. This paper discusses a technical approach to provide Nb material (ingot) and thin disks for producing the elliptical cavity structure, with direct slicing from Nb ingot having sufficiently optimized purity and residual resistance ration (RRR) necessary for the ILC SRF cavities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Error and Correction Analysis for the FFA@CEBAF Energy Upgrade

An energy upgrade design for the Continuous Electron Beam Accelerator Facility (CEBAF) is under development, using fixed field alternating gradient (FFA) return arcs to recirculate electron beam up to an additional five times through the accelerating structures at CEBAF. A necessary component of any large accelerator is a beam steering and optical correction system. Small environmental changes and system errors can lower beam quality or even shut down the machine; and in pursuit of the scientific mission of JLab, high quality electron beams must be delivered to the experimental halls on a predictable schedule. Correction in the novel FFA arcs of the current upgrade design is complicated by several factors. These complexities inform the choice of correction algorithm structure and parameter values. A baseline algorithm in addition to diagnostic and correction hardware configuration is presented. The effect of this correction protocol is shown with respect to estimated errors, and several possible extensions of the algorithm are discussed. This work presents an important proof of concept for the FFA@CEBAF design effort, and provides a functional correction strategy which may be simply adjusted and optimized for future design changes.

Coxe, Alex [Old Dominion Univ., Norfolk, VA (Unite↗
DOE OSTI2015

Preliminary experimental investigation of a Ku-band radial line oscillator based on transition radiation effect

A Ku-band radial line oscillator (RLO) with low guiding magnetic field was proposed in our previous work. In order to weaken the impedance mismatch between the oscillator and an intense electron accelerator with higher impedance, a transverse electromagnetic reflector is added to improve the RLO, which is favorable to increase the Q-factor and accelerate the device saturation. A preliminary experiment is carried out to investigate the performance of the improved RLO. The radial-radiated electron beam is restrained well under the designed guiding magnetic field of 0.52 T. The preliminary experimental results indicates that high power microwaves with a power of 120 MW and a frequency of 14.12 GHz are generated when the diode voltage is 420 kV and the beam current 14.2 kA. The experimental results suggest the feasibility of the presented RLO generating high power microwaves at a high frequency band. Additionally, more work is needed regarding promotion of the electron beam quality and the impedance match between the electron beam accelerator and the oscillator.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging

Here, the recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense laser probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Application of Chebyshev Formalism to Identify Nonlinear Magnetic Field Components in Beam Transport Systems

An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a beam-based technique for characterizing the extent of the nonlinearity of the magnetic fields of a beam transport system. Horizontally and vertically oriented pairs of air-core kicker magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the beam orbit relative to the unperturbed reference orbit. Fourier decomposition of the position data at eight different points along the beamline was then used to measure the amplitude of these frequencies. For a purely linear transport system one expects to find solely the frequencies that were applied to the kickers with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. Chebyshev polynomials and their unique properties allow one to directly quantify the magnitude of the nonlinearity with the minimum error. A calibration standard was developed using one of the sextupole magnets in a CEBAF beamline. The technique was then applied to a pair of Arc 1 dipoles and then to the magnets in the Transport Recombiner beamline to measure their multipole content as a function of transverse position within the magnets.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Improved calibration of rf cavities for relativistic electron beams: Effects of secondary corrections and experimental verification

In the aspect of longitudinal beam bunching, the bunching strength can be controlled by the rf cavity phase and voltage. However, these machine parameters are different from those that interact with the beam itself. In order to gain control of the beam-cavity interaction, cavity calibration must be performed. Furthermore, it relies on fitting the beam energy gain versus cavity phase to a calibration function. Under the conventional assumption of relativistic beam conditions, the calibration function is a first harmonic sinusoidal function (a sinusoidal function with a period of 2π). However, this expression is insufficient for a high-voltage bunching cavity. Due to beam acceleration inside the cavity, an energy bias and a second harmonic function should be included to modify the conventional calibration function, even for a relativistic electron beam. In this paper, we will derive this modification and provide a comparison to both the Coherent Electron Cooling Experiment and the IMPACT T simulation, respectively.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Measurement of Single Spin Asymmetry in 3 He↑(e, e'K ± )X from a Transversely Polarized 3 He Target

Spin-dependent observables are a powerful tool to probe the internal structure of the nucleon and to study the dynamics of the strong interaction. Experimental study of the nucleon spin structure has provided us with many exciting and often surprising results. The so-called "spin crisis" in the 1980s revealed the limitation of naive quark-parton models and led to a worldwide effort to study the nucleon spin structure. However, this effort has been focused mainly on the nucleon's longitudinal spin structure. Recently, when the pioneer work revealed the significant role that transverse spin plays in understanding the full structure of the nucleon and in understanding the dynamics of the strong interaction, the study of the transverse spin structure became the new focus of the worldwide effort. Jefferson Lab (JLab) is located at Newport News, VA, US. It is equipped with the continuous electron beam accelerator facility (CEBAF) and four experimental halls: A, B, C and D. The accelerator can provide a continuous electron beam (2 ns beam bunch) with high polarization (up to ~ 90%) and high current (up to ~ 200μA) for fixed target experiments in all experimental halls. Hall A consists of two standard high-resolution spectrometers (HRS): left HRS (LHRS) and right HRS (RHRS). Another spectrometer, the BigBite spectrometer, can be installed on request by certain experiments. The experiment E06-010 ("Transversity Experiment") at JLab Hall A is the first measurement of the transverse spin structure of the neutron using a transversely polarized 3 He target and a 5.89 GeV incident electron beam. The experiment measured target single spin asymmetries (SSA) and beam-target double-pin asymmetries (DSA) in semi-inclusive deep-inelastic scattering (SIDIS) and in deep-inelastic scattering (DIS) processes. It also collected inclusive hadron (pion, kaon and proton) production data parasitically. The scattered electrons were detected in the BigBite spectrometer with associated detectors while the hadrons were detected with the LHRS which had excellent particle identification capabilities. In this dissertation, the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized 3 He target will be discussed. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematical range of 0.1 bj <0.4 for K + and K - production. While the Collins and Sivers moments for K+ are consistent with zero within the experimental uncertainties, both moments for K- favor negative values. The Sivers moments are compared to the theoretical prediction from a phenomenological fit to the world data. While the K + Sivers moments are consistent with the prediction, the K - results differ from the prediction at the 2-sigma level. The measurements of SSA and DSA in the inclusive hadron (pion, kaon, proton) production channels, with an average transverse momentum T >=0.64 GeV/c, will also be discussed. The asymmetries strongly depend on the flavor of hadron. The π + and π - asymmetries are opposite in sign, demonstrated a strong flavor dependency similar to what has been observed in polarized p ↑ +p collisions. These measurements have provided important inputs to the world's data set on the investigation of transverse spin structure of the nucleon. They also laid the foundation for the future high precision study of the subject in the 12-GeV JLab and a future electron-ion collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1995

Energy measurement of electron beams by Compton scattering

A method has been proposed to utilize the well-known Compton scattering process as a tool to measure the centroid energy of a high energy electron beam at the 0.01% level. It is suggested to use the Compton scattering of an infrared laser off the electron beam, and then to measure the energy of the scattered gamma-rays very precisely using solid-state detectors. The technique proposed is applicable for electron beams with energies from 200 MeV to 16 GeV using presently available lasers. This technique was judged to be the most viable of all those proposed for beam energy measurements at the nearby Continuous Electron Beam Accelerator Facility (CEBAF). Plans for a prototype test of the technique are underway, where the main issues are the possible photon backgrounds associated with an electron accelerator and the electron and laser beam stabilities and diagnostics. The bulk of my ASEE summer research has been spent utilizing the expertise of the staff at the Aerospace Electronics Systems Division at LaRC to assist in the design of the test. Investigations were made regarding window and mirror transmission and radiation damage issues, remote movement of elements in ultra-high vacuum conditions, etc. The prototype test of the proposed laser backscattering method is planned for this December.

Keppel, Cynthia↗
DOE OSTI2024

Resonant Emittance Mixing of Flat Beams in Plasma Accelerators

Linear colliders rely on high-quality flat beams to achieve the desired event rate while avoiding potentially deleterious beamstrahlung effects. Here, we show that flat beams in plasma accelerators can be subject to quality degradation due to emittance mixing. This effect occurs when the beam particles' betatron oscillations in a nonlinearly coupled wakefield become resonant in the horizontal and vertical planes. Emittance mixing can lead to a substantial decrease of the luminosity, the main quantity determining the event rate. In some cases, the use of laser drivers or flat particle beam drivers may decrease the fraction of resonant particles and, hence, mitigate emittance deterioration.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Demonstration of cooling by the Muon Ionization Cooling Experiment

The use of accelerated beams of electrons, protons or ions has furthered the development of nearly every scientific discipline. However, high-energy muon beams of equivalent quality have not yet been delivered. Muon beams can be created through the decay of pions produced by the interaction of a proton beam with a target. Such ‘tertiary’ beams have much lower brightness than those created by accelerating electrons, protons or ions. High-brightness muon beams comparable to those produced by state-of-the-art electron, proton and ion accelerators could facilitate the study of lepton–antilepton collisions at extremely high energies and provide well characterized neutrino beams. Such muon beams could be realized using ionization cooling, which has been proposed to increase muon-beam brightness. Here we report the realization of ionization cooling, which was confirmed by the observation of an increased number of low-amplitude muons after passage of the muon beam through an absorber, as well as an increase in the corresponding phase-space density. The simulated performance of the ionization cooling system is consistent with the measured data, validating designs of the ionization cooling channel in which the cooling process is repeated to produce a substantial cooling effect. The results presented here are an important step towards achieving the muon-beam quality required to search for phenomena at energy scales beyond the reach of the Large Hadron Collider at a facility of equivalent or reduced footprint.

43 PARTICLE ACCELERATORS↗