Performance of the Charge-Injection Capability of Suzaku XIS
Abstract
A charge-injection technique is applied to the X-ray CCD camera, XIS (X-ray Imaging Spectrometer) aboard Suzaku. The charge transfer inefficiency (CTI) in each CCD column (vertical transfer channel) is measured by the injection of charge packets into a transfer channel and subsequent readout. This paper reports on the performances of the charge-injection capability based on the ground experiments using a radiation-damaged device, and in-orbit measurements of the XIS. The ground experiments show that charges are stably injected with a dispersion of 91eV in FWHM in a specific column for the charges equivalent to an X-ray energy of 5.1keV. This dispersion width is significantly smaller than that of the X-ray events of 113eV (FWHM) at approximately the same energy. The amount of charge loss during transfer in a specific column, which is measured with the charge-injection capability, is consistent with that measured with the calibration source. These results indicate that the charge-injection technique can accurately measure column-dependent charge losses, rather than the calibration sources. The column-to-column CTI correction to the calibration source spectra significantly reduces the line widths compared to those with a column-averaged CTI correction (from 193eV to 173eV in FWHM on an average at the time of one year after the launch). In addition, this method significantly reduces the low-energy tail in the line profile of the calibration source spectrum.
- Publication:
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Publications of the Astronomical Society of Japan
- Pub Date:
- February 2008
- DOI:
- 10.1093/pasj/60.sp1.S1
- arXiv:
- arXiv:0705.1771
- Bibcode:
- 2008PASJ...60S...1N
- Keywords:
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- Astrophysics
- E-Print:
- Paper contains 18 figures and 15 tables. Accepted for publication in PASJ