Propagation of a laser-driven relativistic electron beam inside a solid dielectric

• Published in: Physical review. E, Statistical, nonlinear, and soft matter physics Vol. 86; no. 3 Pt 2; p. 036412
• Main Authors: Sarkisov, G S, Ivanov, V V, Leblanc, P, Sentoku, Y, Yates, K, Wiewior, P, Chalyy, O, Astanovitskiy, A, Bychenkov, V Yu, Jobe, D, Spielman, R B
• Format: Journal Article
• Language: English
• Published: United States 01.09.2012
• Subjects: Computer Simulation; Electric Conductivity; Electrons; Glass - chemistry; Glass - radiation effects; Lasers; Light; Models, Theoretical; Scattering, Radiation
• ISSN: 1550-2376
• DOI: 10.1103/PhysRevE.86.036412

Laser probe diagnostics: shadowgraphy, interferometry, and polarimetry were used for a comprehensive characterization of ionization wave dynamics inside a glass target induced by a laser-driven, relativistic electron beam. Experiments were done using the 50-TW Leopard laser at the University of Nevada, Reno. We show that for a laser flux of ∼2 × 10(18) W/cm2 a hemispherical ionization wave propagates at c/3 for 10 ps and has a smooth electron-density distribution. The maximum free-electron density inside the glass target is ∼2 × 10(19) cm-3, which corresponds to an ionization level of ∼0.1%. Magnetic fields and electric fields do not exceed ∼15 kG and ∼1 MV/cm, respectively. The electron temperature has a hot, ringlike structure with a maximum of ∼0.7 eV. The topology of the interference phase shift shows the signature of the "fountain effect", a narrow electron beam that fans out from the propagation axis and heads back to the target surface. Two-dimensional particle-in-cell (PIC) computer simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields driven by laser. The very low ionization observed after the laser heating pulse suggests a fast recombination on the sub-ps time scale.