Measurement of the laser pulse phase velocity in plasma channel for DLA optimization

Fuente: arXiv
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Auteurs principaux: Starodubtseva, E. M., Tsymbalov, I. N., Gorlova, D. A., Ivanov, K. A., Volkov, R. V., Savel'ev, A. B.
Format: Preprint
Publié: 2026
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author Starodubtseva, E. M.
Tsymbalov, I. N.
Gorlova, D. A.
Ivanov, K. A.
Volkov, R. V.
Savel'ev, A. B.
author_facet Starodubtseva, E. M.
Tsymbalov, I. N.
Gorlova, D. A.
Ivanov, K. A.
Volkov, R. V.
Savel'ev, A. B.
contents We demonstrate a novel, direct method for measuring the phase velocity $v_ϕ$ of an intense laser pulse within a plasma channel - the crucial parameter that controls the resonance condition in direct laser acceleration (DLA). The technique exploits the second harmonic (SH) radiation generated at the channel sheath - a phenomenon previously observed in laser-wakefield acceleration experiments. The SH emission angle is governed by a phase-matching condition that directly depends on $v_ϕ$. Experimental measurements performed using a 1 TW, 10 Hz Ti:Sa laser system yield phase velocities in the range $v_ϕ=(1.010-1.030)c$ for plasma electron densities in the range $n_e=(0.01-0.06)n_{cr}$. The diagnostic is validated through quasi-3D particle-in-cell (PIC) simulations that reproduce the experimental conditions. This work provides a way to optimize DLA schemes by enabling in-situ measurement of the laser pulse phase velocity in plasma channels.
format Preprint
id arxiv_https___arxiv_org_abs_2602_13408
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Measurement of the laser pulse phase velocity in plasma channel for DLA optimization
Starodubtseva, E. M.
Tsymbalov, I. N.
Gorlova, D. A.
Ivanov, K. A.
Volkov, R. V.
Savel'ev, A. B.
Plasma Physics
Accelerator Physics
We demonstrate a novel, direct method for measuring the phase velocity $v_ϕ$ of an intense laser pulse within a plasma channel - the crucial parameter that controls the resonance condition in direct laser acceleration (DLA). The technique exploits the second harmonic (SH) radiation generated at the channel sheath - a phenomenon previously observed in laser-wakefield acceleration experiments. The SH emission angle is governed by a phase-matching condition that directly depends on $v_ϕ$. Experimental measurements performed using a 1 TW, 10 Hz Ti:Sa laser system yield phase velocities in the range $v_ϕ=(1.010-1.030)c$ for plasma electron densities in the range $n_e=(0.01-0.06)n_{cr}$. The diagnostic is validated through quasi-3D particle-in-cell (PIC) simulations that reproduce the experimental conditions. This work provides a way to optimize DLA schemes by enabling in-situ measurement of the laser pulse phase velocity in plasma channels.
title Measurement of the laser pulse phase velocity in plasma channel for DLA optimization
topic Plasma Physics
Accelerator Physics
url https://arxiv.org/abs/2602.13408