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1

Determination of initial recombination of ions created in quasi-pulsed radiation fields

Zielczyński M., Golnik N., Gryziński M. A.

Nukleonika

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2008

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Vol. 53, suppl. 2

33--36

EN

A new method is proposed for the determination of ion collection efficiency due to initial recombination process only, in a high pressure ionization chamber, operating in a quasi-pulsed radiation field. It is shown that the influence of undesirable volume recombination can be eliminated using a semi-empirical formula. The unknown function of the chamber polarizing voltage, included to the formula, can be found experimentally in the investigated radiation field, using the approach proposed in the paper. The function is the same for all radiation fields with similar time structure.

2

Applications of recombination chambers in the dosimetry of high energy radiation fields

Zielczyński M., Golnik M., Gryziński M. A.

Nukleonika

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2008

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Vol. 53, suppl. 1

45-52

EN

High energy radiation fields exist in space, in the atmosphere at the height of commercial flights and in the vicinity of some accelerators. The characteristic features of these fields are their complex composition and broad energy spectrum. Estimation of the absorbed dose in such fields cannot be performed by consideration of the doses from all the radiation field components. The physically possible way to solve the problem is to determine the operational quantity-ambient dose equivalent H* (10). The radiation detector used for the determination of H* (10) should be large enough in order to simulate the ICRU sphere. Its effective wall thickness should not be very different than 10 mm of tissue. The REM-2 type recombination chamber is an example of such a detector. The review paper presents specific challenges of high energy radiation field dosimetry and discusses a number of examples of measurements at high energy accelerators, including some international intercomparisons. We show that the REM-2 chamber is especially suitable for radiation monitoring in the vicinity of high energy accelerators.

3

Initial recombination of ions in ionization chambers filled with hydrocarbon gases

Gryziński M., Golnik N., Zielczyński M.

Nukleonika

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2007

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Vol. 52, nr 1

7-12

EN

Data on the initial recombination of ions are needed for designing recombination chambers, used in mixed radiation dosimetry in order to obtain information about radiation quality. Nevertheless, experimental data for pressurized gases are scarce, whereas reliable theoretical models are absent. The paper provides experimental data on the initial recombination in hydrocarbon gases (methane, ethane and propane) depending on gas pressure up to 1.8 MPa. The data were derived from the measurements of saturation curves of a tissue equivalent recombination chamber of an REM-2 type, in reference radiation fields of 137Cs and 239Pu-Be sources. Ion recombination due to volume recombination and back diffusion of ions was subtracted from the measured values of ion collection efficiency. The values of gas parameters needed for the subtraction procedure were determined by measurements of saturation curves of the chamber at several dose rates for each gas pressure. The important practical rule resulting from the experiments is that in the first approximation the initial recombination does not depend on the kind of the hydrocarbon gas but only on its density in the chamber.