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Temporal and spatial evolutions of plasma produced in a nanosecond laser field characterized by langmuir probe diagnostics
Author(s) -
Morshedian N.,
Shahverdi F.
Publication year - 2018
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.201700044
Subject(s) - langmuir probe , plasma , plume , atomic physics , electron , ion , ambipolar diffusion , materials science , nanosecond , electron temperature , laser , wavelength , plasma diagnostics , pulse duration , physics , optics , quantum mechanics , thermodynamics
Based on the temporal and spatial evolutions of the plasma plume, the behaviour of the laser‐produced plasma is studied using a wire Langmuir probe. The plasma is generated by focusing a Nd:YAG laser pulse of 30 ns pulse duration, ∼110 mJ energy, and 1064 nm wavelength) on a solid metal (steel‐316) target. By conducting experiments at low pressures (1 × 10 3 –5 × 10 −5 mbar), the following results were obtained: (a) At a lower pressure, the rise time of the electron signals is reduced, but the current amplitude is increased for both ions and electrons. (b) Fitting the shock wave model of propagation to the experimental results of the plasma plume expansion within the range 1–7 mm distance from the target shows better agreement at lower pressures. (c) For both electrons and ions, the velocity of the particles exhibited plume splitting (two regimes of velocities, namely fast and slow), which is interpreted as being dominant due to the ambipolar field. In addition, at the centimetre‐scale distance from the target and using the time‐of‐flight method, the electron and ion velocities were determined to be ∼3 × 10 7 and ∼1.2 × 10 6 cm/s, respectively. The electron temperature is in the range 2–29 eV, and the ion density is in the range 10 11 –10 13 cm −3 at milimeter to centimetre distances from the target.