Bias Polarity Switching-Type TlBr X-Ray Imager

This study introduces an X-ray imager that uses TlBr detectors and demonstrates its potential for X-ray imaging applications. Although TlBr detectors are suitable for X-ray imaging applications because of the associated large attenuation coefficients and direct conversion behavior, realizing a flat-panel detector with TlBr involves developing processes. The proposed imager is constructed utilizing a combination of existing technologies; it comprises a plate electrode containing thallium metal to suppress the polarization phenomenon, pixelated silver electrodes with 80 μm pitch, and a photon-counting-type readout integrated circuit (ROIC) that can work in the hole as well as electron collection modes. The modulation transfer function (MTF) of the imager is calculated based on the imaging results of an X-ray test chart, and the result corresponds to 180 μm sampling. Even though the imager is not designed specifically for TlBr detectors, the measured high-MTF shows the immense potential of TlBr detectors for X-ray imaging applications. In addition, the polarization phenomenon and its recovery effect through bias switching are confirmed to be similar to conventional detectors with large electrodes. The results of this study can motivate the development of flat-panel-detector processes optimized for TlBr detectors.