First images of digital autoradiography system based on a Medipix2 hybrid silicon pixel detector

摘要

We present the first images of beta autoradiography obtained with the high-resolution hybrid pixel detector consisting of the Medipix2 single photon counting read-out chip bump-bonded to a 300 μm thick silicon pixel detector. This room temperature system has 256 * 256 square pixels of 55 μm pitch (total sensitive area of 14 * 14 mm~2), with a double threshold discriminator and a 13-bit counter in each pixel. It is read out via a dedicated electronic interface and control software, also developed in the framework of the European Medipix2 Collaboration. Digital beta autoradiograms of ~(14)C microscale standard strips (containing separate bands of increasing specific activity in the range 0.0038-32.9 kBq g~(-1)) indicate system linearity down to a total background noise of 1.8 * 10~(-3) counts mm~(-2) s~(-1). The minimum detectable activity is estimated to be 0.012 Bq for 36 000 s exposure and 0.023 Bq for 10 800 s exposure. The measured minimum detection threshold is less than 1600 electrons (equivalent to about 6 keV Si). This real-time system for beta autoradiogaphy offers lower pixel pitch and higher sensitive area than the previous Medipix1-based system. It has a ~(14)C sensitivity better than that f micro channel plate based systems, which, however, shows higher spatial resolution and sensitive area.