A Substandard Condenser Dosemeter and its Calibration against Four National Free-Air Standard Chambers

A complete installation for standard measurements of roentgen radiation was planned and designed at the Institute of Radiophysies by the author in 1929. This was completed in 1930 (4), and its free-air ionization chamber has since been the primary Swedish standard for quantitative radiation measurements, by which substandards and sec­ ondary instruments are calibrated. However, on account of its principle, a free-air standard chamber can only be used for radiation measurements in a narrow beam of accurately defined direction, and is therefore merely a laboratory standard instrument. Measurements of effective doses, or dose rates, i. e. with backscatter included, are, however, met with in most clinical and experimental radi­ ologie work. For such purposes, other kinds of ionization chambers are required, and small, closed chambers of various types and sizes are then at our disposal. The second step necessary for a complete introduction of the r-unit in general clinical and experimental radiologie work in