Transient changes in electric fields induced by interaction of ultraintense laser pulses with insulator and metal foils: Sustainable fields spanning several millimeters

The temporal evolutions of electromagnetic fields generated by the interaction between ultraintense lasers ($1.3\times {10}^{18}$ and $8.2\times {10}^{18}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$) and solid targets at a distance of several millimeters from the laser-irradiated region have been investigated by electron deflectometry. For three types of foil targets (insulating foil, conductive foil, and insulating foil onto which a metal disk was deposited), transient changes in the fields were observed. We found that the direction, strength, and temporal evolution of the generated fields differ markedly for these three types of targets. The results provide an insight for studying the emission dynamics of laser-accelerated fast electrons.

Figure 1

(a) Schematic of the experimental setup. (b) Magnified schematic showing the irradiation positions and target materials.

Figure 2

Deflection of electron pulses as a function of time delay for three types of targets: PE target (triangle), fully coated target (diamond), and disk-coated target (circle). Deflection for a distance L of (a) 2.5 mm and (b) 5 mm. Insets show the deflection along the $y$ axis.

Figure 3

Deflection for the PE target [(a) and (b)] and disk-coated target [(c) and (d)] for different laser intensities. The circles and diamonds show the deflection of the OAP1 pulses with energies and intensities of 160 mJ and $8.2\times 10{}^{18}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$ (high intensity) and 62 mJ and $1.3\times {10}^{18}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$ (low intensity), respectively. The scale of the vertical axis for the high-intensity pulses for the disk-coated target is fivefold that for the low-intensity pulses.