Speaker
Description
Micro-pattern gaseous detectors (MPGDs), when integrated with optical imaging sensors, have been proven to effectively and accurately capture radiation beam information. To address the challenges of monitoring the dose and profile of medical pencil proton beams, which have a high density of greater than 109 Hz/cm2, an optical readout micro-mesh gaseous structure (ORM) was proposed. A Micromegas prototype was manufactured with a glass substrate coated with transparent indium tin oxide as the detector anode. Its effective area is 25 cm × 25 cm. The ORM was firstly characterized with an Iron-55 X-ray source (55Fe) and a silver target X-ray tube individually, high gain greater than 104, and spatial resolution of 400 µm (10% MTF) were achieved. The prototype was then tested with the medical pencil proton beams. The evaluation revealed linear dose responses exceeding 99% (R-squared value) for both single-point and nine-point beam spots at various beam energies and doses. The size and center position deviation of the nine-point spot measurement were within 0.35 mm and 1 mm, respectively, indicating the good potential of this method for MPPB spot quality assurance. The prototype also conducted radiotherapy gamma ray testing, and it allows for more accurate measurement of rising edges. In addition, by adding appropriate conversion layers, ORM is expected to be extended to monitor other types of high-throughput beams.
