Laser frequency upconversion in plasmas with finite ionization rates

Qu, Kenan; Fisch, Nathaniel J.

doi:10.1063/1.5110292

Cited by 10 publications

(4 citation statements)

References 32 publications

(73 reference statements)

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“…The creation of a pair plasma is modeled as a temporal interface of refractive indices, which is known to cause laser frequency upshift [40,[56][57][58][59]. The frequency upshift process [36][37][38][41][42][43][44][45][46][47] is analogous to the trivial process of laser wavelength shift when crossing a spatial interface of refractive indices. The concept of laser frequency change in dynamic media was first studied [35] theoretically by Morgenthaler in 1958.…”

Section: Laser Frequency Upshift Induced By Plasma Effectsmentioning

confidence: 99%

“…Both properties contribute to strong collective plasma effects. More importantly, the laser pulse, while creating the QED cascade, also probes the time varying pair plasma through the induced frequency change [35][36][37][38][39][40][41][42][43][44][45][46][47]. The laser frequency upshift, determined solely by the change of plasma frequency, provides a robust and unambiguous signature of the collective plasma effects.…”

Section: Introductionmentioning

confidence: 99%

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Creating pair plasmas with observable collective effects

Meuren

Fisch

2023

Plasma Phys. Control. Fusion

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Although existing technology cannot yet directly produce ﬁelds at the Schwinger level, experimental facilities can already explore strong-ﬁeld QED phenomena by taking advantage of the Lorentz boost of energetic electron beams. Recent studies show that QED cascades can create electron-positron pairs at suﬃciently high density to exhibit collective plasma eﬀects. Signatures of the collective pair plasma eﬀects can appear in exquisite detail through plasmainduced frequency upshifts and chirps in the laser spectrum. Maximizing the magnitude of the QED plasma signature demands high pair density and low pair energy, which suits the conﬁguration of colliding an over 1018Jm-3 energy-density electron beam with a 1022-1023Wcm-2 intensity laser pulse. The collision creates pairs that have a large plasma frequency, made even larger as they slow down or reverse direction due to both the radiation reaction and laser pressure. This paper explains at a tutorial level the key properties of the QED cascades and laser frequency upshift, and at the same time ﬁnds the minimum parameters that can be used to produce observable QED plasma.

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Section: Laser Frequency Upshift Induced By Plasma Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Creating pair plasmas with observable collective effects

Meuren

Fisch

2023

Plasma Phys. Control. Fusion

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“…The increase of plasma frequency abruptly reduces the vacuum refractive index which the laser is mediated. The consequence is that the laser frequency is upshifted and laser wavelength is blue shifted, according to the theory of temporal change of optical refractive index [85][86][87][88][89][90][91][92][93][94] . The pair oscillation, which is responsible for the laser frequency upshift, is coupled to the intense laser field to radiate a strong signal.…”

Section: B Producibility Vs Observability Of the Pair Plasmasmentioning

confidence: 99%

Collective plasma effects of electron-positron pairs in beam-driven QED cascades

Qu,

Meuren,

Fisch

2021

Preprint

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Understanding the interplay of strong-field QED and collective plasma effects is important for explaining extreme astrophysical environments like magnetars. It has been shown that QED pair plasmas is possible to be produced and observed by passing a relativistic electron beam through an intense laser field. This paper presents in detail multiple sets of 3D QED-PIC simulations to show the creation of pair plasmas in the QED cascade. The beam driven method enables a high pair particle density and also a low particle gamma factor, which both play equal rolls on exhibiting large collective plasma effects. Finite laser frequency upshift is observed with both ideal parameters (24 PW laser laser colliding with 300 GeV electron beam) and with existing technologies (3 PW laser laser colliding with 30 GeV electron beam).

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“…In this manner, pair density and corresponding plasma frequency changes can induce a shift in frequency, similar to ionization. [21][22][23] Note that the single particle dynamics in a QED cascade differ greatly from electrons generated through ionization. The QED cascade occurs at much higher laser intensities and corresponding particle energies than ionization.…”

Section: Introductionmentioning

confidence: 99%

Particle Deceleration for Collective QED Signatures

Griffith,

Qu,

Fisch

2022

Preprint

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Frequency upshifts have been proposed as a first experimental signature of collective effects in QED cascade generated electron-positron pair plasmas. Since the high effective masses of generated pairs will reduce any frequency change, stopped pairs at minimal Lorentz factor in the lab frame were thought to be the dominant contribution to the the laser upshift. However, we demonstrate that only considering stopped particles unduly neglects the contributions of particles re-accelerated in the laser propagation direction. Re-accelerated particles should, on a per particle basis, affect the laser more strongly, and over a much longer timescale. To maximize particle contributions to the laser upshift, we consider a Laguerre-Gaussian (LG) mode to better reflect generated pairs. The LG mode doesn't have an advantage in particle deceleration and re-acceleration when compared against a Gaussian beam, but the LG mode can maintain particle contributions for a longer duration, allowing for more pair density accumulation. Deceleration with a structured beam to keep pairs within the laser should create a larger upshift, thereby lowering the demands on the driving laser.

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Laser frequency upconversion in plasmas with finite ionization rates

Cited by 10 publications

References 32 publications

Creating pair plasmas with observable collective effects

Creating pair plasmas with observable collective effects

Collective plasma effects of electron-positron pairs in beam-driven QED cascades

Particle Deceleration for Collective QED Signatures

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