Free ion yield observed in liquid isooctane irradiated by   rays. Comparison with the Onsager theory

Abstract

We have analyzed data on the free ion yield observed in liquid isooctane irradiated by 60 Co γ rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian type function and an exponential function.A linear dependence between free ion yield and external electric field has been found at low electric field values (E < 1.2 M V /m) in excellent agreement with the Onsager theory. At higher electric field values we obtain a solution in power series of the external field using the Onsager theory.

Characterization of tetramethylsilane for liquid-filled ionization dosimeters: Ion mobilities, free-ion yield and general recombination

“…Experimental results for a TMS-filled microLion taken from [8] are compared to results computed with the Boag equation and the experimental parameters obtained in this work. We also show results for an isooctane-filled LIC for the sake of comparison, with experimental parameters taken from [19]. The agreement between experimental and numerical results for TMS is good except for the largest dose per pulse (2.7 mGy).…”

“…[8], and numerical collection efficiencies (solid lines, with dashed lines showing the uncertainty interval), obtained by using the Boag equation and the experimental G fi obtained in this work, in pulsed radiation for a h ¼0.35 mm parallel-plate TMS-filled (A). For the sake of comparison we also show collection efficiencies for an isooctane-filled LIC, with experimental parameters taken from [19].…”

Modeling ion recombination in liquid ionization chambers — Improvement and analysis of the two‐dose‐rate method

“…The Onsager theory for initial recombination has been validated for isooctane in the work by Pardo et al, which involved experiments with γ rays from a 60 Co source. However, for densely ionizing radiation and liquids with high electron mobilities, such as tetramethylsilane, Tachiya described deficiencies with employing the Onsager theory to interpret results from several radiation chemistry experiments .…”

Liquid-filled ionization chamber temperature dependence

“…If the collection efficiency is very close to the unit, temperature dependence of the measured signal is due to the free ion yield variation. Within the Onsager theory, and working at moderate electric field E values [9], the free ion yield can be expressed as…”

“…When applying this formula to the sensitive medium, isooctane, the dielectric constant is ¼ 1:94 0 and thermalization distance is r ¼ 170 Â 10 À10 m [9]. In particular, the liquid gap thickness of our detector is 0.6 mm, which was calculated through electrical capacity measurements.…”