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XR-100SDD Silicon Drift Detector (SDD)

Amptek recently brought silicon wafer manufacturing in-house and improved the process. The result is a detector with lower noise, lower leakage current, better charge collection, and uniformity from detector to detector.

The XR-100SDD is a thermoelectrically cooled solid-state silicon drift detector (SDD) and preamplifier.  It is recommended for applications requiring the best energy resolution, very high count rates, and lowest X-ray energies.  Its performance, small size, and low cost make it the ideal detector for many laboratory and OEM X-ray spectroscopy applications, including EDS and XRF.

The XR-100SDD can provide a resolution of 125 eV FWHM at the Mn Kα line (electronic noise of 4.5 electrons rms), a peak to background of 20,000:1, an output count rate over 500 kcps, and can detect X-rays down to the Be Kα line (110 eV).  It has a 25 mm2 active area and is 500 μm thick.

The standard XR-100SDD has a 0.5 mil Be window for good efficiency above 2 keV. For lower energies, the optional Patented C-Series windows  available with our FAST SDD® provide good efficiency down to the B line.   For count rates >200 kcps, the FAST SDD® is recommended.

In the XR-100SDD, the detector is mounted on an extender (several different lengths are available), with the preamplifier in the attached metal box. It requires a separate signal processor and power supplies; Amptek’s PX5 is recommended and is ideally suited for most laboratory uses. The same SDD detectors are available in the smaller X-123SDD package or with smaller preamplifiers for OEMs and custom systems.

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  • 125 eV FWHM Resolution @ 5.9 keV
  • High Peak-to-Background Ratio – 20,000:1
  • 25 mm2 – collimated to 17 mm2
  • 500 µm Thick
  • 2-Stage Thermoelectric Cooler
  • Cooling ΔT>85 K
  • Temperature Monitor
  • Thin Beryllium 0.3 or 0.5 mil
    Patented C-Series windows available with FAST SDD
  • Multilayer Collimator
  • Hermetic Package (TO-8)
  • Wide Detection Range
  • Easy to Operate
  • Radiation Hard


  • X-Ray Fluorescence
    • RoHS/WEEE
    • Precious metals
    • Alloy analysis
    • Light elements
  • EDS
  • Teaching and Research
  • Process Control
  • Mössbauer Spectrometers
  • PIXE
  • Wavelength dispersive XRF

Figure 1. 55Fe spectrum taken with the Amptek silicon drift detector (SDD).

  • Description +

    Amptek recently brought silicon wafer manufacturing in-house and improved the process. The result is a detector with lower noise, lower leakage current, better charge collection, and uniformity from detector to detector.

    • Lower noise → Better resolution down to 125 eV FWHM
    • Lower leakage current → Higher temperature operation (save battery life)
    • Better charge collection → Better photopeak shape (no tailing)
    • Quality → Detectors have consistent performance allowing for easier calibrations

    The XR-100SDD is an enhanced version of Amptek’s thermoelectrically cooled X-ray detectors. It uses a silicon drift detector (SDD), a silicon photodiode with a special electrode configuration giving very low capacitance, resulting in low electronic noise at high frequencies. This provides the improved energy resolution and count rate. The SDD uses special “drift” electrodes to guide the charge into its anode, hence the name “drift detector”.

    As with Amptek’s other XR-100 detectors, the photodiode is mounted on a two stage thermoelectric cooler, keeping the detector and its input JFET at approximately -55 °C, reducing electronic noise without cryogenic liquid nitrogen. This cooling permits high performance in a compact, convenient package, and has been a core enabler of the portable XRF analyzer.

    The hermetic TO-8 package of the detector has a light tight, vacuum tight, thin Be window to enable soft X-ray detection. There is vacuum inside the enclosure for optimum cooling. The XR-100SDD detector includes an internal multilayer collimator to minimize background and spectral artifacts. It has a reset-style preamplifier.

    In the XR-100SDD, the preamplifier is enclosed in a metal box, 3.0 x 1.75 x 1.125 in (76.2 x 44.45 x 28.58 mm), with the detector on an extender (available lengths range from 3/8” to 9” or 9.53 to 228.6 mm). The XR-100SDD with a 5” or 9” extender is suitable for vacuum measurements, using the optional CP75 vacuum flange. Alternate preamplifiers are available, recommended for OEMs or where space is limited.

  • Performance +

    Figure 2. Resolution vs. peaking time at different detector temperatures. Note that there is little change in resolution over detector temperature for the peaking times that are typically used with the SDD (<4µs).


    Figure 4. Resolution vs. Input Count Rate for different peaking times for the silicon drift detector (SDD) with the DP5.
    The plot also shows the curve of maximum output count rate. Operating to the right of that curve results in less throughput than the maximum despite a higher input rate. See Figure 5 below.

    Figure 5. Throughput with the silicon drift detector (SDD). Due to the detector’s smaller capacitance, a much shorter peaking time is used in the shaping amplifier without sacrificing resolution. Typically 4 µs or less is used. This dramatically increases the throughput of the system.

    Figure 6. 55Fe spectrum with 4 million counts in the peak channel taken with the silicon drift detector (SDD).

    Figure 7. Resolution vs. Energy for Different Peaking Times taken with the silicon drift detector (SDD).

    Figure 8. Energy resolution, efficiency, and X-ray energy:  This plot shows how the intrinsic efficiency (top) and energy resolution (bottom) depend on the X-ray energy.

    In the bottom plot, the black curve represents “Fano broadening”, the theoretical limit with a Si based detectors, arising from quantum fluctuations in the charge production process.  The colored curves represent the combination of Fano broadening and intrinsic electronic noise under optimum conditions (full cooling and long peaking time).  The detector selection is most important at the lowest energies because Fano broadening dominates at high enough energies.

    In the top plot, the efficiency at low energies is determined by transmission through the window and detector dead layer.  The efficiency at high energies is determined by attenuation in the active depth of the detector.  A Si detector with Be window is recommended between about 2 and 30 keV.  A Si detector with a C1 or C2 window is recommended at lower energies, while a CdTe detector is best at energies above 30 keV.

    Efficiency Package: A ZIP file of coefficients and a FAQ about efficiency. This package is provided for general information. It should not be used as a basis for critical quantitative analysis.

  • Specifications +

    Detector Type Silicon Drift Detector (SDD)
    Detector Area 25 mm2 – collimated to 17 mm2
    Silicon Thickness 500 µm
    Collimator Internal Multilayer
    Energy Resolution @ 5.9 keV (55Fe) 125 – 135 eV FWHM at 11.2 µs peaking time
    Peak to Background 20,000:1 (ratio of counts from 5.9 keV to 1 keV) (typical)
    Detector Window Options Beryllium (Be): 0.5 mil (12.5 µm) or 0.3 mil (8 µm)
    Patented C-Series: C1 and C2 low energy windows available with FastSDD
    Charge Sensitive Preamplifier Amptek custom reset preamplifier.
    Gain Stability <20 ppm/°C (typical)
    XR-100SDD Case Size 3.00 x 1.75 x 1.13 in (7.6 x 4.4 x 2.9 cm)
    XR-100SDD Weight 4.4 ounces (125 g)
    Total Power <2 Watt
    Warranty Period 1 Year
    Typical Device Lifetime 5 to 10 years, depending on use
    Operation conditions -35 °C to +50 °C
    Storage and Shipping Long term storage: 10+ years in dry environment
    Typical Storage and Shipping: -40 °C to +85 °C, 10 to 90% humidity noncondensing
    TUV Certification
    Certificate #: CU 72072412 02
    Tested to: UL 61010-1: 2004 R7 .05
    CAN/CSA-C22.2 61010-1: 2004


    Preamp Power ±8 to 9 V @ 15 mA with no more than 50 mV peak-to-peak noise
    Detector Power -100 to -180 V @ 25 µA very stable <0.1% variation
    Cooler Power Current = 450 mA maximum, voltage = 3.5 V maximum with <100 mV peak-to-peak noise
    Note: When the XR-100SDD is provided without an Amptek DPP, it includes its own closed loop temperature controller.  When shipped with an Amptek DPP, temperature control is done by the DPP. (Delta_Tmax=85°C)


    Preamplifier Sensitivity 0.8 mV/keV typical
    Preamplifier Polarity Positive signal output (1 kohm maximum load)
    Preamplifier Feedback Reset
    Preamplifier Output Rise Time <60 ns
    Temperature Monitor Sensitivity PX5: direct reading in Kelvin through software.

    XR-100SDD Connectors

    Preamp Output BNC coaxial connector
    Power and Signal 6-Pin LEMO connector (Part# ERA.1S.306.CLL)
    Interconnect Cable XR-100SDD to PX5: 6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 6-Pin LEMO (5 ft length)
    XR-100SDD stand-alone: 6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 9-Pin D (5 ft length)

    XR-100SDD 6-Pin LEMO Connector Pin Out

    Pin 1 Temperature monitor diode
    Pin 2 -H.V. Detector Bias, -100 to -180 V
    Pin 3 -9 V Preamp power
    Pin 4 +9 V Preamp power
    Pin 5 Cooler power return
    Pin 6 Cooler power
    0 to +3.5 V @ 450 mA
    Case Ground and shield


    The silicon drift detector (SDD) requires negative high voltage and produces a positive preamplifier output. This is the opposite of the Si-PIN which requires positive high voltage and produces a negative preamplifier output.

    The PX5 can produce both negative and positive high voltage. When the PX5 is ordered with an XR-100SDD, the PX5 is set for negative high voltage. Using a Si-PIN XR-100CR with a negative high voltage setting will destroy the Si-PIN XR-100CR and will not be covered under warranty. Likewise, if the PX5 was ordered with a Si-PIN XR-100CR, using a positive high voltage with an XR-100SDD will destroy the silicon drift detector (SDD) detector and not be covered under warranty.

  • Applications +

    Application Spectra

    Figure 9. XRF of stainless steel SS316 taken with the silicon drift detector (SDD) and the Mini-X x-ray tube.

    Figure 10. RoHS/WEEE PVC sample taken with the silicon drift detector (SDD) and the Mini-X x-ray tube.

    Figure 11. CaCl2 solution (800 ppm Ca, 1200 ppm Cl) taken with silicon drift detector (SDD) and the Mini-X x-ray tube.

    Figure 12. Sulphur in crude oil (1100 ppm) with some KCl taken with silicon drift detector (SDD) and the Mini-X x-ray tube.

    Figure 13. Automotive Catalyst taken with silicon drift detector (SDD) and the Mini-X x-ray tube.

    Figure 14. Platinum (Pt) ring XRF taken with silicon drift detector (SDD) and the Mini-X x-ray tube.

  • Options & Additional Info +

    Signal Processor/Power Supply Modules

    PX5 Digital Pulse Processor, MCA and Power Supply

    Power to the XR-100SDD is provided by the PX5 Digital Pulse Processor and Power Supply. The PX5 is DC powered by an AC adapter and provides a variable Digital Pulse Processing Amplifier (0.200 µs to 100 µs peaking time), the MCA function, and all power supplies for the detector.

    The XR-100SDD/PX5 systems ensures stable operation in less than one minute from power turn-on.

    Block diagram of a typical system using the PX5 and an Amptek XR-100SDD detector. Several different detector and preamp configurations are available from Amptek, Inc., with different pinouts and voltages.

    DP5/PC5 OEM Digital Pulse Processor, MCA, and Power Supply

    XR-100SDD with the DP5 and PC5 is an option that requires some assembly and possibly a custom enclosure depending on the application on the part of the customer.

    Figure 15. Standard XR-100 box connected to the DP5 and PC5.

    Window Options and Thicknesses

    Amptek SDDs are available with either beryllium windows, or our Patented C-Series windows.  The Be options are Paralyne coated (to prevent gas diffusion), and are supplied in two thicknesses, 0.3 mil or 0.5 mil (8 or 12 μm). ThePatented C-Series windows are designed for low Z element detection down to Beryllium (Be).

    Options and Accessories

    • C-Series Windows
    • Collimator Kit for high flux applications
    • External Collimator
    • Vacuum Accessories
    • OEM Applications

    Figure 17. XR-100SDD Detector Extender Options.

    Internal Multilayer Collimator

    All of Amptek’s Si detectors contain internal multilayer collimators to improve spectral quality. X-rays interacting near the edges of the active volume of the detector may produce small pulses due to partial charge collection. These pulses result in artifacts in the spectrum which, for some applications, obscure the signal of interest. The internal collimator restricts X-rays to the active volume, where clean signals are produced. Depending on the type of detector, collimators can improve peak to background (P/B), eliminate edge effects, eliminate false peaks.

    A multilayer collimator is made by progressively using lower Z materials. Each layer acts as an absorber to the fluorescence peaks of the previous layer. The final layer will be of the lowest Z material whose fluorescence peaks are of low enough energy to be outside the anticipated X-ray detection range.

    Amptek has developed a state-of-the-art internal Multilayer Collimator (ML). The base metal is 100 µm of tungsten (W), the first layer is 35 µm of chromium (Cr), the second layer is 15 µm of titanium (Ti), and the last layer is 75 µm of aluminum (Al).

    Additional Information

  • Mechanicals +

    1.5 Inch Extender (standard)

    Figure 19. All dimensions in inches ±0.005.

    XR-100 STP File

    No Extender

    Figure 20. All dimensions in inches ±0.005.

    General AXR (T0-8) Mechanical Dimensions

    Figure 21. All dimensions in inches ±0.005.

    TO-8 STP File

    Typical Detector Geometry

    Figure 22. Typical Detector Geometry.


    XR-100 STP File

    Detector (TO-8) STP File

  • Documentation +