{'fraction_non_alphanumeric': 0.025738798856053385, 'fraction_numerical': 0.009532888465204958, 'mean_word_length': 5.140350877192983, '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}}
Experimental determination of wall correction factors. I: Cylindrical ionisation chambers

Wall correction factors were measured for different types of ionisation chamber. The procedure was to compare the reading of an unknown chamber with that of a reference chamber (graphite Farmer chamber with graphite build-up cap), both in air in a 60Co gamma-ray beam and in a water phantom irradiated by a 20 MeV electron beam. A comparison of the authors' values with other experimental values shows good agreement, within 0.3%, after normalisation on the reference chamber values, for most chambers. However, a 0.9% lower value was observed for a nylon-walled Farmer chamber suggesting that differences in thickness of the inner surface of the thimble might occur. The use of such an inhomogeneous ionisation chamber as a reference instrument for absorbed dose determinations at the reference point in a phantom should therefore not be recommended. Generally good agreement, within 0.5%, exists between experimental and calculated wall correction factors.