title: [Theoretical investigation of the saturation correction for ionization chambers irradiated with pulsed beams of arbitrary pulse length].
abstract: In ionization chambers, not all released charge is collected due to the recombination of charge carriers. This effect is taken into account by the saturation correction factor kS. A physical description of the correction factor has been established for pulsed radiation. However, it is only accurate when the pulse length is short compared with the collection time of the ionization chamber. In this paper we develop a description of the saturation correction for radiation pulses of arbitrary length. For this, a system of partial differential equations is solved iteratively. The numerical solutions are verified experimentally for a Roos ionization chamber (PTW TM34001) exposed to a pulsed electron beam. The results of this iterative procedure describe the experimental data well. The calculations are also possible for beam structures which are experimentally hard to get and thereby contribute to a better understanding and correct description of the saturation correction at arbitrary pulse length. Among other things the pulse length dependent distributions of the charge carriers in the ionization chamber is calculated, inclusive of the transition to the conditions prevailing in the case of continuous irradiation. Furthermore is shown that the formula for kS established by Hochhäuser and Balk is applicable even at arbitrary pulse length, if pulse duration dependent effective values are used for the parameters a and p. These effective values have been determined for the Roos chamber at pulse lengths up to 300 μs.
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Dresden. Electronic address: Leonhard.Karsch@oncoray.de.
authors.forename: Leonhard
authors.initials: L
authors.lastname: Karsch
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Dresden.
authors.forename: Jörg
authors.initials: J
authors.lastname: Pawelke
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D004583:Electrons; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008962:Models, Theoretical; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Ionisationskammern; Ionization chambers; Sättigungskorrektion; arbitrary pulse length; beliebige Pulslänge; saturation correction