silicon drift detector, SDD

One of the energy-dispersive X-ray detector used for EDS. The principle, in which characteristic X-rays entering the detector element are converted to electron-hole pairs, is the same as for the Si(Li) detector. But unlike the Si(Li)detector, electrons generated from the detector element by the incident characteristic X-rays are efficiently guided to a small anode at the center of the element by a concentric electrode structure with a potential gradient. This unique electrode structure reduces capacitance, thus enabling high-speed signal response. Thus compared with the Si(Li) detector, voltage pulses are collected with higher-speed, higher-signal-to-noise ratio. As a result, SDD may not suffer the influence from dark current due to thermal noise, and works at approximately –15 °C by Peltier cooling. SDD provides an energy resolution comparable to the Si(Li) detector and also performs X-ray analysis with high count rate (＞1 x 10⁵ cps), which is more than one order higher than the Si(Li) detector. Since it is unnecessary to use liquid nitrogen, the detector can be compactly designed. Thus SDD has more been used in place of the Si(Li) detector.

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