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Results for “electron beam emittance”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Ultra low emittance electron beams from multi-alkali antimonide photocathode operated with infrared light

The intrinsic emittance of electron beams generated from a multi-alkali photocathode operated in a high voltage DC gun is reported. The photocathode showed sensitivity extending to the infrared part of the spectrum up to 830 nm. The measured intrinsic emittances of electron beams generated with light having wavelength longer than 800 nm are approaching the limit imposed by the thermal energy of electrons at room temperature with quantum efficiencies comparable to metallic photocathodes used in operation of modern photoinjectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Light Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.

ACCPHY↗
DOE OSTI2011

Experimental optimization of the 6-dimentional electron beam emittance at the NSLS SDL

Experimental optimization of the 6-dimensional electron beam emittance generated by a Magnesium (Mg) photocathode RF gun is presented in this report. A new electron beam optimization algorithm for a low charge (<100 pC) beam was experimentally demonstrated; where the electron beam velocity bunching inside the RF gun plays a critical role, and the transverse emittance as a function of the laser-RF timing jitter was experimentally characterized for the first time. A 20 pC electron beam was optimized to have a normalized slice emittance of 0.15 mm mrad and a longitudinal projected emittance of 3.9 ps keV. Furthermore, the upper limit of the measured thermal emittance - 0.5 mm mrad per mm of the rms laser size, is about 50% lower than the theoretical prediction for a Mg cathode (Qian et al., 2010) [1].

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Electron beam emittance at operational intensity in fourth-generation synchrotron light sources

For synchrotron light sources, the brightness of user X-ray beams is primarily determined by the electron beam emittance and energy spread at operational intensity. A common feature of fourth-generation synchrotrons is the short length of electron bunches combined with a very small transverse beam size. Consequently, the particle density is much higher than in machines of previous generations, leading to strong collective effects that significantly increase the emittance and limit the achievable brightness at operational beam intensity. In this article, we summarize our studies of the emittance scaled with the beam energy and intensity, taking into account the effects of intrabeam scattering, beam-impedance interaction, and bunch lengthening provided by higher-harmonic RF systems, to identify optimal combinations of machine and beam parameters.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Power density calculation of spontaneous radiation emission from a finite emittance electron beam in planar undulators

We extend the angular power density formulae for spontaneous radiation emission from planar undulators to include finite emittance and angular misalignment of the electron beam. Then we calculate and compare power densities estimated from integral approach with Gaussian beam distribution and summation approach with macro-particle allocation covering particle beam phase space. After showing that both approaches converge to each other, we apply the macro-particle approach to study power absorbed and transmitted by various apertures at front end of 9-ID beamline at National Synchrotron Light Source-II for misaligned electron beam. Our analysis indicate that the electron beam misalignment could lead to unwarranted power deposition at tighter apertures that would have been otherwise difficult to account for during the aperture design/choice process.

43 PARTICLE ACCELERATORS↗
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 OSTI2016

Intrinsic emittance reduction in transmission mode photocathodes

High quantum efficiency (QE) and low emittance electron beams provided by multi-alkali photocathodes make them of great interest for next generation high brightness photoinjectors. Spicer’s three-step model well describes the photoemission process; however, some photocathode characteristics such as their thickness have not yet been completely exploited to further improve the brightness of the generated electron beams. Here, we report on the emittance and QE of a multi-alkali photocathode grown onto a glass substrate operated in transmission and reflection modes at different photon energies. We observed a 20% reduction in the intrinsic emittance from the reflection to the transmission mode operation. This observation can be explained by inelastic electron-phonon scattering during electrons’ transit towards the cathode surface. Due to this effect, we predict that thicker photocathode layers will further reduce the intrinsic emittance of electron beams generated by photocathodes operated in transmission mode.

36 MATERIALS SCIENCE↗
DOE OSTI2011

NSLS-II X-Ray Diagnostics Development

NSLS-II x-ray diagnostics will provide continuous online data of electron beam dimensions, which will be used to derive electron beam emittance and energy spread. It will also provide information of electron beam tilt for coupling evaluation. X-ray diagnostics will be based on imaging of bending magnet and three-pole wiggler synchrotron radiation sources. Diagnostics from three-pole wiggler source will be used to derive particles energy spread. Beta and dispersion functions will have to be evaluated for emittance and particles energy spread calculations. Due to small vertical source sizes imaging need to be performed in x-ray energy range. X-ray optics with high numerical aperture, such as compound refractive lens, will be used to achieve required spatial resolution. Optical setups with different magnifications in horizontal and vertical directions fill be employed to deal with large aspect ratio of the source. X-ray diagnostics setup will include x-ray imaging optics, monochromatization, x-ray imaging and recording components.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

The multi-bend achromat storage rings

Not very long ago, the 3{sup rd} generation storage ring technology was judged as mature. Most of the 3{sup rd} generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA) concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Optimizing 4d Emittance Measurements Using the Pinhole Scan Technique

Accurate measurement of electron beam emittance is essential for optimizing high-brightness electron sources. The Pinhole Scan Technique measures the 4D phase space and hence the emittance by measuring the beam profile after clipping the beam using a pinhole followed by a drift section and then scanning the beam over the pinhole. This technique has been implemented in low energy (< 200 keV) beamlines at both Cornell University and Arizona State University. However, the technique poses several practical challenges. In this work, we analyze and address key issues affecting the 4D phase space and emittance measurements using this technique. We identify and investigate sources of inaccuracies like the pinhole aspect ratio, beam divergence, position-momentum correlations in the phase space, and the point-spread-function of the detector and suggest techniques to minimize them. Our findings offer a pathway to more accurate 4D phase space characterization in advanced electron beam systems.

42 ENGINEERING↗
DOE OSTI2022

Controlled Injection of Electrons for Improved Performance of Laser-Wakefield Acceleration

Our lab performed a series of experiments on controlled injection of LWFA with two extreme laser pulses: one laser pulse was used to drive LWFA. In contrast, the other precisely controls the injection of electrons into the wakefield plasma wave. We have demonstrated an efficient reduction of electron beam emittance by optical injection and novel spatio-temporal manipulation of the electron beam by the extreme laser-plasma waves. Moreover, the optical injection process involves unprecedented new physics, which will benefit studies in astrophysics, inertial confinement fusion, laser-driven x-ray light sources, and ultrafast science. We further improved the performance of LWFA by a better understanding and control of the extreme laser-plasma wave dynamics for optical injection. Three novel mechanisms were identified in the optical injection process: (1) collision of two laser pulses, (2) collision of a laser pulse with a wakefield plasma wave, and (3) collision of two laser wakefields. All three methods improved electron-beam energy spread, emittance, stability, and reproducibility. First, we identified, compared, and independently controlled these different injection mechanisms by controlling the polarization of the injector laser pulse. Second, we manipulated the spatiotemporal splitting of LWFA electron beams to reduce their emittance. Third, we applied the same laser-plasma-wave dynamics and the same experimental setup for improved performance of ion acceleration, which has also been predicted by the recent simulations.

43 PARTICLE ACCELERATORS↗