X-123SDD Complete X-Ray Spectrometer with Silicon Drift Detector (SDD)

The X-123SDD uses a silicon drift detector (SDD) similar to a Si-PIN photodiode but with a unique electrode structure to improve energy resolution and increase count rates. The SDD is mounted on a thermoelectric cooler along with the input FET and coupled to a custom charge sensitive preamplifier. The thermoelectric cooler reduces the electronic noise in the detector and preamplifier but the cooling is transparent to the user: it operates like a room temperature system.

The pulse processor is the DP5, a second generation digital pulse processor (DPP) which replaces both the shaping amplifier and MCA found in analog systems. The digital technology improves several key parameters:

1. Better performance, specifically better resolution and higher count rates
2. Greater flexibility since more configuration options are available and selected by software
3. Improved stability and reproducibility.

The DPP digitizes the preamplifier output, applies real-time digital processing to the signal, detects the peak amplitude, and bins this in its histogram memory. The spectrum is then transmitted to the user’s computer. The PC5 supplies the power to the detector, including low voltages for the preamps, high voltage to bias the detector, and a supply for the thermoelectric cooler which provides closed loop control with a maximum temperature differential of 85 °C. All of these are under software control. The X-123SDD input power is an unregulated +5 VDC with a current of about 300 mA.

The complete system is packaged in 7 x 10 x 2.5 cm³ aluminum box. The detector is mounted on an extender, with lengths from 0 to 9” (vacuum flanges are available). In its standard configuration only two connections are required: power (+5 VDC) and communications (USB, RS232, or Ethernet). An auxiliary connector provides several additional inputs and outputs used if the X-123SDD will be integrated with other equipment. This includes an MCA gate, timing outputs, and eight SCA outputs. The X-123SDD is supplied with our DPPMCA data acquisition and control software. It also includes an Application Programming Interface (API) DLL to integrate the unit with custom software. Options include software for analyzing X-ray spectra, vacuum accessories, several collimation and mounting options, and X-ray tubes to complete a compact system for X-ray fluorescence.

Figure 1. X-123SDD Architecture and Connection Diagram.

Figure 2. Resolution vs. Peaking Time and Temperature for the silicon drift detector (SDD).

 

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 9.6 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.

Performance for Different Operating Conditions

Ultimate Resolution

• 125 eV FWHM Resolution @ 5.9 keV
• 11.2 µs Peaking Time
• 100,000 CPS
• Peak to Background Ratio 20,000:1

Not fast enough? Try…

• 155 eV FWHM Resolution @ 5.9 keV
• 0.8 µs Peaking Time
• 500,000 CPS

Operation for Handheld Devices

• 150 eV FWHM Resolution @ 5.9 keV
• 3.2 µs Peaking Time
• 200,000 CPS
• Detector Temperature at 250 K (-24 °C)

X-123SDD Specifications

System Performance

Detector and Preamplifier

Detector Type	Silicon Drift Diode (SDD)
Detector Area	25 mm2 (collimator area 17 mm2)
Detector Thickness	500 µm
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 FAST SDD®
Collimator	Multilayer
Thermoelectric Cooler	2-stage (85° ΔTmax)
Preamplifier Type	Amptek custom reset, charge sensitive.
Preamp Conversion Gain	0.8 mV/keV (typical)

Digital Pulse Processor (DPP)

Gain	Combination of coarse and fine gain yields overall gain continuously adjustable from 0.84 to 127.5.
Coarse Gain	Software selectable from 1.12 to 102 in 16 log steps. 1.12, 2.49, 3.78, 5.26, 6.56, 8.39, 10.10, 11.31, 14.56, 17.77, 22.42, 30.83, 38.18, 47.47, 66.26, 102.0
Fine Gain	Software selectable, 0.75 to 1.25, 10 bit resolution.
Full Scale	1000 mV input pulse @ X1 gain
Gain Stability	<20 ppm/°C (typical)
Pulse Shape	Trapezoidal (A semi-Gaussian amplifier with shaping time t has a peaking time of 2.2t and is comparable in performance with the trapezoidal shape of the same peaking time.)
ADC Clock Rate	20 or 80 MHz, 12 bit ADC
Peaking Time	30 software selectable peaking times between 0.2 and 102 µs, corresponding to semi-Gaussian shaping times of 0.1 to 45 µs.
Flat Top	16 software selectable values for each peaking time (depends on the peaking time), >0.05 µs.
Baseline Restoration	Asymmetric, 16 software selectable slew rate settings.
Fast Channel Pulse Pair Resolving Time	120 ns
Dead Time Per Pulse	1.05 times the peaking time. No conversion time.
Maximum Count Rate	4 x 106 s-1 (periodic). Output count rate of 7 x 105 s-1 for a random input of 1.9 x 106 s-1.
Dead Time Correction	Manual correction based on Fast Channel measurement of ICR. Accurate to 1% for ICR <1 Mcps under typical conditions.
Pulse Selection Options	Pile-up rejection, risetime discrimination, gate

Multichannel Analyzer (MCA)

Number of Channels	Software selectable to: 8k, 4k, 2k, 1k, 0.5k, or 0.25k channels
Bytes per channel	3 bytes (24 bits) – 16.7M counts
Acquisition Time	10 ms to 466 days
Data Transfer Time	1k channels in 12 ms (USB) or 280 ms (RS-232)
Conversion Time	None.
Presets	Time, total counts, counts in an ROI, counts in a single channel
MCS Timebase	10 ms/channel to 300 s/channel
External MCA Controls	Gate input: Pulses accepted only when gated on by external logic. Input can be active high or active low. Software controlled.
Counters	Slow channel events accepted by MCA, Incoming counts (fast channel counts above threshold), SCA8 counts, event rejected by selection logic, and external event counter. Sixteen ROI counters.

Auxiliary Inputs/Output

Single Channel Analyzers	8 SCAs, independent software selectable LLDs and ULDs, LVCMOS (3.3 V) level (TTL compatible)
Digital Outputs	Two independent outputs, software selectable between 8 settings including INCOMING_COUNT, PILEUP, MCS_TIMEBASE, etc. LVCMOS (3.3 V) levels (TTL compatible).
Digital Inputs	Two independent inputs, software selectable for MCA_GATE, EXTERNAL_COUNTER
I/O	Two general purpose I/O lines for custom application
Digital Oscilloscope	Displays oscilloscope traces on the computer. Software selectable to show shaped output, ADC input, etc., to assist in debugging or optimizing configurations.

Communications

USB	2.0 full speed (12 Mbps)
Serial	Standard RS-232 at 115.2k or 57.6k baud
Ethernet	10base-T

Power

Nominal Input Power	+5 VDC at 500 mA (2.5 W) (typical). Current depends strongly on detector ΔT. Ranges from 300 to 800 mA at 5 VDC.
Input Range	4 V to 5.5 V (at 0.4 to 0.7 A typical)
Initial transient	2 A for <100 µs
High Voltage Supply	Internal multiplier, software control -70 to -200 V, negative polarity
Cooler Supply	Closed loop controller with ΔTmax = 85 °C

Physical

Dimensions	7 x 10 x 2.5 cm (2.7 x 3.9 x 1 in) excluding extender
Extender Lengths	1.5” (3.8 cm) standard. Options include no extender, 3/8”, 5”, 9”, and vacuum flanges.
Weight	180 g (6.3 oz)

General and Environmental

Operating temperature	-35 °C to +80 °C
Warranty Period	1 Year
Typical Device Lifetime	5 to 10 years, depending on use
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
Compliance	RoHS Compliant
	TUV Certification Certificate #: CU 72101153 01 Tested to: UL 61010-1: 2009 R10.08 CAN/CSA-C22.2 61010-1-04+GI1

Connectors

Interface Software

DPPMCA	The X-123SDD can be controlled by the Amptek DPPMCA display and acquisition software. This software completely controls and configures the X-123SDD, and downloads and displays the data. It and supports regions of interest (ROI), calibrations, peak searching, and so on. The DPPMCA software includes a seamless interface to the XRF-FP quantitative X-ray analysis software package. Runs under Windows XP PRO SP3 or later. Click here for the software download page.
SDK	The X-123SDD comes with a free Software Developer’s Kit (SDK). The user can use this kit to easily write custom code to control the X-123SDD for custom applications or to interface it to a larger system. Examples are provided in VB, VC++, etc. Click here for the software download page.
VB Demonstration Software	The VB demonstration software runs on a personal computer and permits the user to set the X-123SDD parameters, to start and stop data acquisition, and to save data files. It is provided with source code and can be modified by the user. This software is intended as an example of how to manually control the X-123SDD through either the USB, RS-232, or Ethernet interface using the most basic calls without the SDK. This is primarily needed as an example when writing software for non-Windows platforms. Click here for the software download page.

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.

Window Options and Thicknesses

Amptek SDDs are available with beryllium windows, and our FastSDDs are optionally available with our 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 12.5 μm). The Patented C-Series windows are designed for low Z element detection down to Boron (B).

Options and Accessories

• Patented C Series Windows (Fast SDD only)
  
• Collimator Kit for high flux applications
• External Collimator
• Vacuum Accessories
• OEM Applications

Figure 15a. The XR100SDD/PX5 configuration, which includes the detector, preamplifier, digital processor, and power supplies.

Figure 15b. The detector/preamplifier is available in OEM configurations to fit the requirements of any system. Pictured is the detector with the PA-230 preamplifier and housing. See the OEM page for details.

Figure 16. X-123SDD Detector Extender Options.

X-123 with 9 inch extender STP file.

Use of Collimators

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.

Figure 17. This plot shows a comparison between a collimated detector and a detector without a collimator.

Multilayer Collimator (ML)

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
• Publications
• History of XR100 Resolution

Mechanical Dimensions

Figure 15. Dimensions: in [mm].

Mounting Hardware

Figure 16. The X-123SDD is supplied with two types of mounting hardware: right-angle and flat.

Figure 17. X-123 Mounting Plate.

Figure 18. X-123 right angle mounting bracket.

Download the X-123 STP File