The XIS has suffered the radiation damage, and the energy resolution has got worse. To recover the degradation, we decide to employ a spaced-row charge injection as shown in the right figure. Though this reduces the effective area, the energy resolution becomes much improved.
The radiation damage makes gtrapsh in X-ray CCD pixels. These traps obstruct the event transfer, which causes the degradation. However, if we put charges in front of X-ray events, these charges work as gsacrificalh events; they fill the traps and the X-ray events are transferred smoothly. Then we can restore the eneregy resolution.
We can see how the SCI works in the figure. The energy resolution is successfully improved from 200 eV to 150 eV. The center pulse height of Fe Kalpha line becomes large when we use the SCI. This means X-ray events are transferred with little charge loss.
