Measurement of Return Current in a Laser-Produced Plasma

Characteristics of target polarization by laser ablation

“…The ratio of the total positive target charge to the charge carried by positive ions observed with the FC is of the order of 10 −3 . In contrast with the experiments with nanoseconds to sub-picoseconds lasers (Benjamin et al, 1979;Borowitz et al, 1987), where the time of target charging was comparable with the laser pulse width, in our experiment the positive charge was balanced by a target current during a time period longer by a factor ∼100 in comparison with the laser pulse length. Moreover, a new phenomenon arising after t zero = 2.8 μs indicates that the target is being negatively charged.…”

“…The measurements of the target polarization and the target return current versus laser intensity and target properties give information on escaping electrons generated in the interaction of laser pulses with solid targets (Mendel & Olsen, 1975;Pearlman & Dahlbacka, 1977;Benjamin et al, 1979;Bialkowski et al, 1990;Cikhardt et al, 2014;Dubois et al, 2014). The voltage pulse appears on isolated targets independently of the laser pulse duration.…”

“…The voltage pulse appears on isolated targets independently of the laser pulse duration. The positive charging of the target is balanced by an opposing current which can reach a peak value up to a few kA (Benjamin et al, 1979;Cikhardt et al, 2014). It is supposed that the positive charging of the target results from high-energy electrons leaving the plasma and traveling a distance either until their kinetic energy equals the electric field energy of charge separation or until they strike the vacuum chamber walls (Crow et al, 1975;Eliezer & Hora, 1989;Dubois et al, 2014).…”

“…Although the determination of characteristics of the electronic targetcircuit including its holder system as a Langmuir probe is relatively simple, its interpretation is rather complex. The bias voltage on the target allows measuring both the positive and negative charge emission from the target (Benjamin et al, 1979). The key finding is that the target current can reach a maximum value much later than the laser pulse and shows also a dependence on target material.…”

On the origin of negative target currents during laser ablation of polyethylene

“…Target current (TC) is a relatively unexplored phenomenum in the field of laser-matter interaction. The initial studies started in the late seventies [2,3] and continued in a patchy fashion across the following decades [4,5] until recently.…”