Dosimetry at 28 keV synchrotron radiation for cell irradiations.

Accurate dosimetry is a prerequisite for reliable comparisons between radiobiological irradiation experiments. Parameters affecting the determination of absorbed dose to cells in the shape of a small cell pellet in a centrifuge tube, irradiated by 28 keV mono-energetic photons from a synchrotron, were investigated. Thermoluminescent dosimeter (TLD), diode and ion chambers were utilized to monitor the irradiations. The distribution of the absorbed dose and such parameters as scatter, attenuation and interface dosimetry in the target, which influence the dose, were studied. A method for inter-calibrations of two different calibration sources by using TLD and TLD readers is given. Characteristics of the TLD, that is, fading, supralinearity, energy response, self-attenuation and mini-dosimetry were considered for the dosimetry. A method for correcting photon fluence attenuation in cylindrical TLDs is presented. The study shows that the absorbed dose to cells irradiated at low photon energy at a synchrotron irradiation facility can, using accurate dosimetry protocol, be correctly and reproducibly determined.