{'fraction_non_alphanumeric': 0.03212435233160622, 'fraction_numerical': 0.019689119170984457, 'mean_word_length': 4.8545454545454545, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Acceleration history in laser-ablative impulse measured using velocity interferometer (VISAR)

The aim of the present study is to clarify the time-dependent characteristics of the impulsive force generated by irradiating a laser pulse onto metallic and polymer materials. A Velocity Interferometer System for Any Reflector (VISAR) is employed to measure the acceleration driven by the laser ablation. The VISAR has two delay-lines that enable the velocity measurement in the range from 10 m/s to 100 m/s. The ablation impulse is inferred from the measured acceleration history. The influence of the ambient air on the ablation pressure is investigated for aluminum using a Nd:YAG laser (wavelength: 1064 nm, pulse energy < 1 J, pulse duration ~ 10 ns) and for a polymer material using a CO2 laser (wavelength: 1.06 μm, pulse energy < 10 J, pulse duration ~ 2 μs). The results of the preliminary experiments revealed the promising potential of the VISAR measurement.