Speakers
Description
The calibration of surface contamination monitors requires the use of Large Area Reference Sources (LAAS) whose emission properties must strictly comply with the ISO 8769 standard. A critical requirement of this standard is the uniformity of the surface emission rate, which must be periodically verified to ensure measurement traceability. Currently, the lack of dedicated national instrumentation for mapping the uniformity of α and β emitting sources leads to dependence on external services and high logistical costs. This work describes the development of a compact gas flow proportional counter prototype, specifically designed for the detailed mapping of these measurement standards.
The prototype is constructed with a stainless-steel housing and features a 2.5 x 2.5 cm entrance window, resulting in an active area of 6.25 cm2. The design focuses on internal electric field stability through the optimization of the anode wire diameter and cathode geometry. The signal processing electronic chain utilizes NIM modules for high-voltage bias and spectroscopy amplification.
The detector characterization methodology includes the experimental determination of the counting plateau and the optimization of the gas flow rate to ensure counting reproducibility. Key metrological parameters will be evaluated, such as intrinsic efficiency, dead time, stability, and energy resolution. In the validation phase, the counter will be moved over a 4 x 6 matrix to characterize the uniformity of a 10 x 15 cm source, as prescribed by ISO 8769 criteria. This prototype is expected to provide a robust national solution for quality control and the guarantee of metrological traceability for large area reference sources in Brazil.