Silicon Drift Detector (SDD)
Definition
The current standard EDS detector type, using a reverse-biased silicon chip cooled by a Peltier element to achieve high count-rate capability (up to 500,000 counts per second) and energy resolution of approximately 125-135 eV.
- Detector class
- Energy-dispersive X-ray spectroscopy (EDS) detector
- Cooling method
- Peltier (thermoelectric) element, no liquid nitrogen needed
- Max count rate
- Up to approximately 500,000 counts per second
- Energy resolution
- Approximately 125-135 eV
Common questions
How does an SDD differ from an older Si(Li) detector?+
SDDs use thermoelectric Peltier cooling and stay operational without a liquid nitrogen dewar, while Si(Li) detectors need continuous cryogenic cooling. SDDs also handle far higher count rates, which shortens acquisition time on forensic trace samples.
What is the practical limit of SDD energy resolution?+
At 125-135 eV, an SDD can separate most elemental X-ray peaks used in gunshot residue and paint analysis, but it cannot resolve peaks as finely as wavelength-dispersive spectroscopy, which is used when overlapping peaks need to be distinguished.
Related terms
- ASTM E1588
- ASTM International standard practice for gunshot residue analysis by scanning electron microscopy with energy-dispersive spectrometry. Defines particle classification (characteristic, consistent-with, indicative), morphology...
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- Characteristic X-Ray
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- Energy-Dispersive X-Ray Spectroscopy (EDS)
- An X-ray detection method that simultaneously measures the energies of all characteristic X-ray photons emitted from the interaction volume, identifying all elements...
- FIB (Focused Ion Beam)
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- Interaction Volume
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- Lead-Free GSR
- Gunshot residue produced by ammunition using non-lead primer formulations (SINTOX, Diazol, or other variants). Does not contain the conventional Pb-Sb-Ba three-element combination;...
- Secondary Electron (SE)
- Low-energy electron (below 50 eV) ejected from the top few nanometres of the sample when the primary beam knocks a loosely bound...
- Sputter Coating
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- Ultramicrotome
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- ZAF Correction
- A software correction applied to raw EDS X-ray intensities to account for atomic number (Z), absorption (A), and fluorescence (F) effects within...