NDLI: All-optical control of electron trapping in tapered plasmas and channels

Content Provider	IEEE Xplore Digital Library
Author	Kalmykov, S.Y. Shadwick, B.A. Davoine, X.
Copyright Year	2013
Description	Author affiliation: DAM, CEA, Arpajon, France (Davoine, X.) \|\| Dept. of Phys. & Astron., Univ. of Nebraska - Lincoln, Lincoln, NE, USA (Kalmykov, S.Y.; Shadwick, B.A.)
Abstract	The radiation pressure of a multi-terawatt, sub-100 fs laser pulse propagating in an under-dense plasma causes complete electron cavitation. The resulting electron density “bubble” guides the pulse over many Rayleigh lengths, leaving the background ions unperturbed while maintaining GV/cm-scale accelerating and focusing gradients. The shape of the bubble, and, hence, the wakefield potentials, evolve slowly, in lockstep with the optical driver. This dynamic structure readily traps background $electrons.^{1}$ The electron injection process can thus be controlled by purely optical means.2, 3Sharp gradients in the nonlinear refractive index produce a large frequency red-shift (Δω ~ ω0), localized at the leading edge of the $pulse.^{2,3}$ Negative group velocity dispersion associated with the plasma response compresses the pulse into a relativistic optical shock (ROS). ROS formation slows the pulse (and the bubble), reducing the electron dephasing length and limiting energy $gain.^{4}$ Furthermore, the ponderomotive force due to the ROS causes the bubble to constantly expand, trapping copious unwanted electrons, polluting the electron spectrum with a high-charge, low-energy $tail.^{1,2}$ Here, we demonstrate a new, all-optical approach to compensating for the increase in pulse bandwidth, thereby delaying ROS formation and thus producing high quality, GeV-scale electron beams with 10-TW-class (rather than $PW-class^{4})$ lasers in mm-scale (rather than cm-scale4), highdensity plasmas $(n_{e0}$ > 5 x $10^{18}$ vs. $10^{17}$ $cm^{-3}).$ We show that a negatively chirped drive pulse with an ultra-high (~ 400 nm) bandwidth: extends the electron dephasing length; prevents ROS formation through dephasing; and almost completely suppresses continuous injection. Precise compensation of the nonlinear frequency shift can be achieved using a higher-order chirp extracted from reduced simulation models. ROS formation can be further delayed by using a plasma channel to suppress diffraction of the pulse leading edge, minimizing longitudinal variations in the pulse. Plasma density tapering further delays dephasing, providing an additional boost in beam energy.
Starting Page	1
Ending Page	1
File Size	61840
Page Count	1
File Format	PDF
ISBN	9781467351713
ISSN	07309244
DOI	10.1109/PLASMA.2013.6633483
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2013-06-16
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Plasmas Charge carrier processes Electron optics Nonlinear optics Optical diffraction Optical refraction Optical variables control
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
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9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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