{'fraction_non_alphanumeric': 0.017287234042553192, 'fraction_numerical': 0.011968085106382979, 'mean_word_length': 4.748091603053435, 'pattern_counts': {'":': 0, '<': 0, '<?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}}
Laser heating of air plasmas seeded by ultrashort pulse filaments

The air plasma produced by an ultrashort pulse laser filament can be used as a source of seed electrons for subsequent heating and breakdown by a higher energy long pulse laser. In this way, the threshold intensity for breakdown can be effectively lowered, raising the possibility of producing a bright, hot air plasma at a remote location. The physics of this process is examined experimentally and numerically. The experiment utilizes a 500 fs, 100 mJ pulse from a Nd:glass laser to produce the seed plasma, and a 50 ns, 1 J pulse from a Nd:YAG laser to heat the air. Radially resolved hydrodynamics calculations with detailed air chemistry are carried out to support the experiment.