Description
In laser-ion acceleration experiments, the leading edge of a high power laser pulse can cause target preionization and subsequent preexpansion multiple up to hundreds of picoseconds before the arrival of the main laser peak. The specific amount if target preexpansion is decisive for the ion-acceleration mechanism at play [1]. For dielectric targets, the start of target pre-expansion is characterized by the point in time at which the target undergoes laser-induced breakdown (LIB) [2].
In this contribution, we present a recently published method to determine the time of LIB in interactions of a sub-micron-thick Formvar target with a high-power laser pulse [3]. The method includes a measurement of the LIB thresholds of Formvar and applies them to a third-order autocorrelator measurement of the lasers leading edge. A comparison to previously published data facilitates an empirical LIB scaling for other wide-band-gap dielectric targets that are commonly used in laser-ion acceleration.
[1] N. Dover et al., Light: Science & Applications 12, 71 (2023)
[2] C. Bernert et al., PR Applied 19, 014070 (2023)
[3] S. Assenbaum et al., Plasma Phys. Control. Fusion 67, 015032 (2025)