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SOME PROBLEMS IN THE ABSOLUTE MEASUREMENT OF GERMICIDAL ULTRAVIOLET RADIATION: THE USE OF ‘PEN RAY’ LAMPS AS A CALIBRATION STANDARD
Author(s) -
Věchet B.
Publication year - 1974
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1974.tb06520.x
Subject(s) - irradiance , thermopile , calibration , photometer , dosimeter , ultraviolet , optics , radiation , calibration curve , gas discharge lamp , wavelength , irradiation , materials science , environmental science , physics , chemistry , infrared , detection limit , nuclear physics , electrode , chromatography , quantum mechanics
— Problems of absolute measurement of the dose rate of ultraviolet radiation of germicidal lamps in energetic units were studied. Irradiance at 254 nm generated by three different Pen Ray SC‐1 low‐pressure mercury lamps was measured independently in different laboratories using different instruments: (a) Westinghouse SM‐600 Meter, (b) General Electric Germicidal Meter, and (c) large‐surface thermopile with a Bäckström filter. These lamps were then used as secondary standards of absolute irradiance at wavelength 254 nm and compared with the Latarjet dosimeter and the International Light IL‐254 Germicidal Photometer. Mutual agreement of calibration coefficients of three calibrated Pen Ray SC‐1 lamps was roughly within ±5 per cent error. This calibration uncertainty indicates limits of the usefulness of Pen Ray lamps as standards. A direct radiometric calibration using an FT‐16 Schwarz‐Hilger vacuum thermopile, with interference filter NB‐254 or UVR‐250, was in agreement with the above comparison. On the basis of above radiometric calibration absolute D 37 lethal doses were determined equaling 2·7. J/m 2 for the bacteriophage T2 and 11·0 J/m 2 for the bacteriophage φX‐174, the values being read from exponential survival curves.