XR-100SDD Silicon Drift Detector (SDD) - Obsolete

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.

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.

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

Inputs

Outputs

XR-100SDD Connectors

XR-100SDD 6-Pin LEMO Connector Pin Out

NOTE

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.

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.

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

• Selection Guide
• Efficiency Package (zip file)
• Art and Archaeology
• X-Ray Fluorescence – A Description
• X-Ray Emission Line Chart
• Glossary PDF
• Publications
• History of XR100 Resolution
• Digital Pulse Processor FAQ PDF

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