Original scientific paper
On measurements in investigating protection against roentgen and gamma rays
Josip Lončar
; Institute for General Electrotechnics and Electrical Measurements, Technical Faculty of the University of Zagreb, Zagreb
Abstract
After short introductory considerations on fundamental quantities and units of measurement, the author describes ionization chamber electronic dosage intensity meters for roentgen- and y-rays, suitable as monitors in investigations or protection against these radiations. The design of the instruments is based on author's experimental investigations carried out since 1952 at the Institute for General Electrolechnics and Electrical Measurements, Technical Faculty of the University of Zagreb. Some problems of integral dosage metering in connection with pocket dosimeters are also discussed. Two types of monitors (M1 and M2) arc described. Type M1 is a more straight forward one valve instrument with ionization chamber connected to one stage direct current amplifier allowing the use of indicating microammeters in the range of 50 microamps. The instrument is characterised by the use of a normal Brimar 1S4 Miniature Battery Beam Tetrode instead of commonly used electrometric valves. With careful construction very stable results and full scale deflections of 59 μA a t the indicating instrument could be obtained with radiation intensities of 500 mr/h. The second instrument, the M, monitor, is of a more elaborate design. Two IS4 valves have been used. For the first valve stage a starvation amplifier circuit (9) with extremely large amplification has been chosen, the second stage being a cathode follover circuit (10). In addition a feed-back circuit from the second LO the first stage (10) is used so that the amplification may be controlled in order to obtain sufficient stability. With radiation intensities of 10 mr/h full deflection (50 µA) on the microammeter could be obtained. However for very stable operation ranges of 25 mr/h or even 50 mr/h may better be used. Both instruments proved very satisfactory in investigations of protections against penetrating radiations. Difficulties were encountered, however, when measuring radiation doses from short Roentgen rays pulses as used for radiographic diagnostic work. In such cases pocket dosimeters, or pocket ionization chambers with common charging and indicating equipment, should be used. The author points out the advantages of the ionization instruments as compared with photographic film methods, although a good conducted additional film badge service may be useful for checking of results obtained with ionization instruments.
Keywords
Hrčak ID:
186667
URI
Publication date:
25.10.1954.
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