Some basic features of the beam emittance

Floettmann, K.

doi:10.1103/physrevstab.6.034202

Cited by 155 publications

(109 citation statements)

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“…A particular problem encountered in the case of selfinjected beams is related to the fact that the canonical phase-space emittance grows strongly in a drift in all cases where a large beam divergence is combined with a large energy spread. This fundamental process is described in general form in [3] and applied to the case of a plasma based electron source in [4]. The relevance of the phasespace emittance lies in the fact that the trace-space emittance rapidly growths up to the value of the phasespace emittance as soon as the divergence of the beam is reduced, i.e., in the next focusing element [3].…”

Section: The Conditions Inside the Plasma Channelmentioning

confidence: 99%

Adiabatic matching section for plasma accelerated beams

Floettmann

2014

Phys. Rev. ST Accel. Beams

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An adiabatic matching section is discussed as option to control the divergence and emittance growth of a beam exiting a plasma channel. Based on a general analytical solution of a focusing channel with varying focusing strength, a focusing profile is proposed which allows for a fast expansion of the beam size while keeping the emittance growth minimal. The solution is also applicable to other cases, e.g., the matching of a positron source to the downstream accelerating section, which are, however, not discussed in this contribution.

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Section: The Conditions Inside the Plasma Channelmentioning

confidence: 99%

Adiabatic matching section for plasma accelerated beams

Floettmann

2014

Phys. Rev. ST Accel. Beams

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“…This stochastic space charge effect is caused by an irreversible growth in RMS beam emittance 46 due to the fluctuating components of the nonlinear electron dynamics. In the UEM, it is correlated with virtual cathode formation during the electron pulse generation.…”

Section: Density-dependent Phase Space Structure Evolutions: Theoretimentioning

confidence: 99%

Active control of bright electron beams with RF optics for femtosecond microscopy

Williams¹,

Zhou²,

Sun³

et al. 2017

Structural Dynamics

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A frontier challenge in implementing femtosecond electron microscopy is to gain precise optical control of intense beams to mitigate collective space charge effects for significantly improving the throughput. Here, we explore the flexible uses of an RF cavity as a longitudinal lens in a high-intensity beam column for condensing the electron beams both temporally and spectrally, relevant to the design of ultrafast electron microscopy. Through the introduction of a novel atomic grating approach for characterization of electron bunch phase space and control optics, we elucidate the principles for predicting and controlling the phase space dynamics to reach optimal compressions at various electron densities and generating conditions. We provide strategies to identify high-brightness modes, achieving ∼100 fs and ∼1 eV resolutions with 106 electrons per bunch, and establish the scaling of performance for different bunch charges. These results benchmark the sensitivity and resolution from the fundamental beam brightness perspective and also validate the adaptive optics concept to enable delicate control of the density-dependent phase space structures to optimize the performance, including delivering ultrashort, monochromatic, high-dose, or coherent electron bunches.

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“…Beams with large energy spread can experience emittance growth while propagating in vacuum, even without any space charge interactions [84]. This is relevant to electron sources produced by laser-plasma based accelerators.…”

Section: Emittance Growth For Beams With Large Energy Spreadmentioning

confidence: 99%

Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

Fubiani

2005

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Doctor Wim P. Leemans, ChairPlasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures. The characteristic scalelength of the accelerating field is the plasma wavelength and for typical densities ranging from 10 18 − 10 19 cm −3 , the accelerating fields and scalelength can hence be on the order of 10 − 100 GV/m and 10 − 40 µm, respectively.The production of quasi monoenergetic beams was recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and i ii Abstract even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread. AcknowledgementsThere are many people that I wish to thank for valuable help they gave me during the course of my PhD. It was overall a great experience for me, I learned a lot in many areas and this work confirmed my deep passion for science in general.My great thanks to my adviser Wim Leemans. He gave me such a great opportunity by inviting me to come to l'OASIS group as a PhD student. He was always present for both the good and doubtful times when the results were not

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Some basic features of the beam emittance

Abstract: Some general features of the beam emittance are discussed. The significance of rms values for the emittance calculation and emittance measurements is emphasized and it is shown that the emittance of a beam is not necessarily constant in a drift space.

Cited by 155 publications

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Adiabatic matching section for plasma accelerated beams

Adiabatic matching section for plasma accelerated beams

Active control of bright electron beams with RF optics for femtosecond microscopy

Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

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