Speaker
Description
The micro X-ray computed tomography is a non-destructive 3D imaging technique, being especially interesting for characterizing materials opaque to visible light, as minerals and biological samples. Conventional equipment (benchtop, medical, or industrial tomographs) offer limited spatial resolution of a few tens of micrometers for small samples (a few millimeters), and measurements are taken over long periods (hours). Sirius, Brazil's 4th generation synchrotron light source, has a micro and nano X-ray tomography line, called MOGNO. At the MOGNO microstation, samples up to 80 mm diameter undergo tomographic acquisition with spatial resolution ranging from 5 to ~55 µm at 67 keV, with measurements performed in a few minutes. Furthermore, by enabling rapid measurements, it provides 4D (spatial and temporal resolutions) evaluations of dynamic processes, as the real-time growth of biological samples. While offering opportunities for advancement, radiosensitivity in biological samples and induced damage by ionizing radiation must be minimized. Thus, the dose rate at the sample position is of fundamental importance. Currently, the dose rate has not been experimentally quantified at the MOGNOs microstation, mainly due experimental limitations for dosimetry using active detectors in a high brightness and small FOV. We evaluated the dose rate at the sample position on the MOGNOs microstation using commercial OSL (Optically Stimulated Luminescence) detectors based on BeO (Thermalox 995, Materion Co) and Al2O3:C (Luxel tape, Landauer Inc). The readings of calibrated detectors, at a standard narrow beam (61 keV), were performed on an automated Riso TL/OSL reader (DTU-Nutech). The estimated dose rate in air was approximately 100 µGy/s with both BeO and Al2O3:C detectors, demonstrating the reliability of the measurements. From this value, experimental measurements on the MOGNO`s microstation are underway to minimize the occurrence of tissue reactions or radio-induced damage in imaging.