{'fraction_non_alphanumeric': 0.023613963039014373, 'fraction_numerical': 0.03182751540041068, 'mean_word_length': 4.571428571428571, '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}}
Characterization of a surface barrier discharge in helium

A surface barrier discharge (SBD) operated with helium is investigated in a pressure range from 50 mbar to 1 bar and a gas flow of up to 400 sccm. A sinusoidal or pulsed excitation signal with a voltage amplitude of up to 1 kV and frequency in the range of 4 to 8 kHz is applied. Time resolved and time averaged ICCD pictures of the discharge are analysed. The temporally and spatially resolved concentrations of metastable excited species are determined using diode laser atomic absorption spectroscopy. The transition 23S → 33P °, absorbing the light of wavelength 388.975 nm, is used for the He(23S) diagnostics. The absorption of the transition from the resonant level (21P ° → 31D) at 667.999 nm is shown for comparison. Parallel to the absorption, the total light emission and the electrode voltage and current are traced. The role of the metastable excited species in sustaining a SBD in helium is discussed.