Radiation damage in the Chandra X-ray CCDs

被引：44

作者：

Prigozhin, G ^{[1
]}

Kissel, S ^{[1
]}

Bautz, M ^{[1
]}

Grant, C ^{[1
]}

LaMarr, B ^{[1
]}

Foster, R ^{[1
]}

Ricker, G ^{[1
]}

Garmire, G ^{[1
]}

机构：

[1] MIT, Ctr Space Res, Cambridge, MA 02139 USA

来源：

X-RAY OPTICS, INSTRUMENTS, AND MISSIONS III | 2000年 / 4012卷

关键词：

Charge Coupled Devices; X-ray spectroscopy; radiation damage; electron traps;

D O I：

10.1117/12.391612

中图分类号：

V [航空、航天];

学科分类号：

08 ; 0825 ;

摘要：

Front side illuminated CCDs comprising focal plane of Chandra X-ray telescope have suffered some radiation damage in the beginning of the mission. Measurements of CTI and dark current at different temperatures led us to conclusion that the type of damage is inconsistent with the much studied type of damage created by protons with energies higher than 10 MeV. Intensive ground based investigation showed that irradiation of CCD with low energy protons (about 100 keV) results in the device characteristics very similar to the ones of the flight chips (very low dark current, the shape of the CTI temperature dependence). We were able to reliably determine that only image section of the flight chips was damaged and therefore only fast transfer from image to frame store section was affected. We have developed several techniques in order to determine the parameters of the electron traps introduced into the transfer channel of the irradiated device. One of them is based on the analysis of the amplitude of the signal in the pixels trailing the pixel that absorbed an X-ray photon of known energy. Averaging over large number of photons allowed us to get high signal/noise ratio even for pixels with extremely low signal far behind the X-ray event. Performing this analysis at different temperatures we were able to measure trap density, emission time constant, and trap cross section. Another techique is based on the analysis of the tail behind the events of very high amplitude, such as cosmic ray hits. At least 3 different types of traps were detected, two of them with short time constants in the range from tens to a few hundred microseconds. The most damaging for the device performance is the third one with longer time constant in the millisecond range. The measurement of the trap parameters allows us to accurately model charge transfer inefficiency and helps to choose optimal operational parameters, and eventually will lead to techniques that may noticeably improve performance of a damaged CCD.

引用

页码：720 / 730

页数：11

共 7 条

[1] DISPLACEMENT DAMAGE EFFECTS IN MIXED PARTICLE ENVIRONMENTS FOR SHIELDED SPACECRAFT CCDS [J].