Application of a mesh experiment for a proton beam onto the charge-coupled device

We report here the effect or a ´notch´ structure inside the charge-coupled device (CCD) that is designed to he radiation hard. Using a proton beam, we confirmed that the notch structure improved the charge transfer inefficiency (CTI) by a factor of 3. We applied a mesh technique in the proton beam experiment on a CCD. The proton beam energy is 600 keV that leaves bigger damage than those high energy widely reported. The CCD employed has 1024 × 1024 pixels with a notch structure. The mesh technique enables us to confine the proton beam to a circular region of 2 μm diameter within a 24 × 24 μm² pixel. Some pixels are damaged in the notch region while others in the out-of-notch region. After the proton irradiation, we measured the CTI using ⁵⁵Fe which showed that the CTI of pixels damaged in the notch region is larger by a factor of 3 than that of pixels damaged in the out-of-notch region. We experimentally showed, for the first time, that the CTI depends on the damaged region in a pixel.