XR-100CR Si-PIN X-Ray Detector

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. This makes it the best performing Si-PIN detector available.

The XR-100CR is a high performance thermoelectrically cooled Si-PIN X-ray detector and preamplifier. It is typically used in laboratory X-ray spectroscopy applications requiring moderate energy resolution and moderate count rates where cost is important. It is well suited to many XRF applications such as identifying metal alloys, verifying RoHS/WEEE compliance, and detecting lead in paint.

The energy resolution of the XR-100CR ranges from 139 to 190 eV FWHM depending on the detector area. It is best at count rates below 30 kcps and is suited to X-rays between 1.5 and 30 keV.  It uses a fully depleted 500 um Si-PIN photodiode, and is available with 1 or 0.5 mil Be windows.

In the XR-100CR 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 Si-PIN detectors are available in the smaller X-123 package or with smaller preamplifiers for OEMs and custom systems.

Figure 1. 55Fe Spectrum taken with a 6 mm2/500 µm detector.
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Applications

  • X-Ray Fluorescence (XRF)
  • RoHS/WEEE
  • Portable Instruments
  • OEM
  • Nuclear Medicine
  • Teaching and Research
  • Art and Archaeology
  • Process Control
  • Mössbauer Spectrometers
  • Space and Astronomy
  • Environmental Monitoring
  • Nuclear Plant Monitoring
  • Toxic Dump Site Monitoring
  • PIXE

Features

  • Si-PIN Photodiode
  • Available in 6, 13 and 25 mm2
  • 2-Stage Thermoelectric Cooler
  • Temperature Monitor
  • Beryllium Window
  • Multilayer Collimator
  • Hermetic Package (TO-8)
  • Wide Detection Range
  • Easy to Operate

  • Description +


    The XR-100CR was a breakthrough in X-ray detector technology, providing “off-the-shelf” performance previously available only from expensive cryogenically cooled systems. Although newer detector technologies are now available, including Amptek’s XR-100SDD and the FastSDD®, the XR-100CR is still the workhorse of the XRF industry because of the combination of good performance and low cost.

    The heart of Amptek’s XR-100CR is a thermoelectrically cooled Si-PIN photodiode which senses the X-rays. The two stage thermoelectric cooler keeps the detector and its input JFET at approximately -55 °C, reducing electronic noise without cryogenic liquid nitrogen. This cooling is key to the XR-100CR since it permits high performance in a compact, convenient package.

    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-100CR detector includes an internal multilayer collimator to minimize background and spectral artifacts. It has a reset-style preamplifier, using a unique method of resetting through the high voltage connection to minimize noise.

    In the XR-100CR the preamplifier is enclosed in a metal box, 3.0 x 1.75 x 1.125 inches, with the detector on an extender (available lengths: no extender, 1.5″, 5″, and 9”). The XR-100CR 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.

    X-rays interact with silicon atoms to create an average of one electron/hole pair for every 3.62 eV of energy lost in the silicon. Depending on the energy of the incoming radiation, this loss is dominated by either the Photoelectric Effect or Compton scattering. The probability or efficiency of the detector to “stop” an x-ray and create electron/hole pairs increases with the thickness of the silicon. For more information, please refer to the Efficiency Curves on the “Performance” tab.

    In order to facilitate the electron/hole collection process, a 100-200 volt bias voltage is applied across the silicon depending on the detector thickness. This voltage is too high for operation at room temperature, as it will cause excessive leakage, and eventually breakdown. Since the detector in the XR-100CR is cooled, the leakage current is reduced considerably, thus permitting the high bias voltage. This higher voltage decreases the capacitance of the detector, which lowers system noise.

    The thermoelectric cooler cools both the silicon detector and the input FET transistor to the charge sensitive preamplifier. Cooling the FET reduces its leakage current and increases the transconductance, both of which reduce the electronic noise of the system.

    Since optical reset is not practical when the detector is a photodiode, the XR-100CR incorporates a novel feedback method for the reset to the charge sensitive preamplifier. The reset transistor, which is typically used in most other systems has been eliminated. Instead, the reset is done through the high voltage connection to the detector by injecting a precise charge pulse through the detector capacitance to the input FET. This method eliminates the noise contribution of the reset transistor and further improves the energy resolution of the system.

    A temperature monitor diode chip is mounted on the cooled substrate to provide a direct reading of the temperature of the internal components, which will vary with room temperature. Below -20 °C, the performance of the XR-100CR will not change with a temperature variation of a few degrees. Hence, closed loop temperature control is not necessary when using the XR-100CR at normal room temperature. For OEM applications or hand held XRF instrumentation a closed loop temperature control is recommended. The Active Temperature Control is standard in Amptek electronics such as the PX5 and DP5/PC5.

  • Performance +


    Figure 1. Resolution vs. Peaking Time and Temperature for the 6, 13, and 25 mm² Si-PIN detectors.

    Figure 3. Resolution vs. input count rate (ICR) for various peaking times. Taken with XR-100CR and PX5.

    Figure 4. PX5 throughput for various peaking times.

    Efficiency Curves

    Figure 5 (linear). Shows the intrinsic full energy detection efficiency for the XR-100CR detectors. This efficiency corresponds to the probability that an X-ray will enter the front of the detector and deposit all of its energy inside the detector via the photoelectric effect.

    Figure 6 (log). Shows the probability of a photon undergoing any interaction, along with the probability of a photoelectric interaction which results in total energy deposition. As shown, the photoelectric effect is dominant at low energies but at higher energies above about 40 keV the photons undergo Compton scattering, depositing less than the full energy in the detector.

    Both figures above combine the effects of transmission through the Beryllium window (including the protective coating), and interaction in the silicon detector. The low energy portion of the curves is dominated by the thickness of the Beryllium window, while the high energy portion is dominated by the thickness of the active depth of the Si detector. Depending on the window chosen, 90% of the incident photons reach the detector at energies  ranging from 2 to 3 keV. Depending on the detector chosen, 90% of the photons are detected at energies up to 9 to 12 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.

    Theoretical Resolution as a Function of Energy

    Figure 7. Resolution as a function of energy for various detector resolutions. For example, a detector with an 55Fe resolution of 145 eV FWHM will follow the red curve.

    Resolution at Common Characteristic X-ray Energies

    Example: Find the 55Fe row in the above table and locate the resolution of the detector (bold). The column with that resolution lists the resolutions of that detector for these common energies.

  • Specifications +


    General

    Detector Type Si-PIN
    Detector Sizes 6 mm2 (collimated to 4.4 mm2)
    13 mm2 (collimated to 11.1 mm2)
    25 mm2 (collimated to 21.5 mm2)
    Silicon Thickness 500 µm
    Collimator Multilayer
    Energy Resolution @ 5.9 keV (55Fe) 139 eV FWHM to 230 eV FWHM depending on detector type and shaping time constant.
    Background Counts <5 x 10-3/s, 2 keV to 150 keV for 6 mm2/500 µm detector
    Detector Be Window Thickness 1 mil (25 µm), or 0.5 mil (12.5 µm)
    Charge Sensitive Preamplifier Amptek custom design with reset through the H.V. connection
    Gain Stability <20 ppm/°C (typical)
    Case Size 3.00 x 1.75 x 1.13 in (7.6 x 4.4 x 2.9 cm)
    Weight 4.9 ounces (139 g)
    Total Power <1 Watt
    Warranty Period 1 Year
    Typical Device Lifetime 5 to 10 years, depending on use
    Operation conditions -35 °C to +80 °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 non condensing
    TUV Certification
    Certificate #: CU 72072412 01
    Tested to: UL 61010-1: 2004 R7 .05
    CAN/CSA-C22.2 61010-1: 2004

    Inputs

    Preamp Power ±8 to 9 V @ 15 mA with no more than 50 mV peak-to-peak noise
    Detector Power +180 V (power supply should be able to produce between +100 to 200 V @ 1 µA) very stable <0.1% variation
    Cooler Power Current = 350 mA maximum, voltage = 4 V maximum with <100 mV peak-to-peak noise
    Note: the XR-100CR includes its own closed loop temperature controller (Delta_Tmax=85°C)

    Outputs

    Reset Output Waveform The output of the XR100CR swings from +5 V to -5 V.
    The reset period will vary with detector type and count rate.
    Preamplifier Sensitivity 1 mV/keV typical (may vary for different detectors)
    Preamplifier Polarity Negative signal output (1 kohm maximum load)
    Preamplifier Feedback Reset through the detector capacitance
    Temperature Monitor Sensitivity (Diode) 770 mV = -50 °C
    For Amptek electronics direct reading in K through software.

    XR-100CR Connectors

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

    6-Pin LEMO Connector Pin Out

    Pin 1 Temperature monitor diode
    Pin 2 +H.V. Detector Bias, +100 – 200 V maximum
    Pin 3 -9 V Preamp power
    Pin 4 +9 V Preamp power
    Pin 5 Cooler power return
    Pin 6 Cooler power
    0 to +4 V @ 350 mA
    Case Ground and shield

    Vacuum Operation

    The XR-100CR can be operated in air or in vacuum down to 10-8 Torr. There are two ways the XR-100CR can be operated in vacuum: 1) The entire XR-100CR detector and preamplifier box can be placed inside the chamber. In order to avoid overheating and dissipate the 1 Watt of power needed to operate the XR-100CR, good heat conduction to the chamber walls should be provided by using the four mounting holes. An optional Model 9DVF 9-Pin D vacuum feedthrough connector on a Conflat is available to connect the XR-100CR to the PX5 outside the vacuum chamber. 2) The XR-100CR can be located outside the vacuum chamber to detect X-Rays inside the chamber through a standard Conflat compression O-ring port. Optional Model EXV9 (9 inch) vacuum detector extender is available for this application. Click here for more information on vacuum applications and options.

  • Applications +


    XR-100CR Si-PIN Application Spectra

    The most common applications of the XR-100CR are in the field of X-Ray fluorescence, or XRF. This is an analytical technique which determines the elements present in a sample, and does so non-destructively and very rapidly.

    RoHS/WEEE Application
    Alloy Analysis: XRF of SS316, XRF of Ag/Cu
    XRF of lead (Pb)
    Metal Plating
    Process Control
    XRF of a Saint Gaudens US $20 Gold Coin
    XRF of a Various Jewelry
    Glass Analysis
    Paper Analysis
    Mössbauer Spectroscopy
    Multi-Element Fluorescence Sample
    Low Z Element Fluorescence
    241Am Spectrum

    RoHS/WEEE Application

    The RoHS / WEEE [Restriction of Hazardous Substances / Waste from Electrical and Electronic Equipment] directive requires that the electronics industry certify that products comply with maximum concentration amounts of particular elements and compounds (Cr VI, Pb, Cd, Hg, Br PBB/PBDE) by July, 2006. The chart below shows the X-ray spectrum emitted by a combination of chromium (Cr), lead (Pb), and cadmium (Cd). The XR-100CR can be used to verify compliance with the RoHS/WEEE requirements as part of a quality assurance program, via XRF. It permits users to measure the concentration of the specified elements, quickly, accurately, and non-destructively. Companies can verify supplier compliance and demonstrate their own compliance.

    Figure 8. Chromium (Cr), lead (Pb), and cadmium (Cd) XRF. The RoHS / WEEE directive requires that the electronics industry certify product to comply with maximum concentration amounts of particular elements and compounds (Cr VI, Pb, Cd, Hg, Br PBB/PBDE) by July, 2006.

    XRF of SS316

    XRF can be used to determine exactly the alloy of a particular piece of metal. Each alloy has a unique ratio of elements, and with XRF, one can non-destructively determine the ratio of elements from the ratio of the intensities of the peaks. The spectrum below shows the spectrum of X-rays emitted from a piece of stainless steel 316, when excited by 109Cd. The strong Fe line indicates that this is based on iron, while the Cr, Mn, Ni, and Mo peaks can be used to identify the alloy. This can be very important in numerous applications, such as quality assurance (verifying a vendor used the correct alloy), process control, metal recycling, etc.

    Figure 9. X-Ray Fluorescence (XRF) of SS316 from 109Cd.

    XRF of Silver (Ag) and Copper (Cu) Alloy

    Figure 10. XRF of Silver (Ag) and Copper (Cu) Alloy.

    XRF of lead (Pb)

    A very important special case in the field of metals analysis is that of lead (Pb). Lead has been commonly used in many products for years, from paint to plumbing solders to electronic assemblies. XRF provides a non-destructive method to assess whether or not lead is present in an item, without damaging the item. The spectrum below shows the characteristic L X-rays emitted from a piece of pure lead, with a 109Cd excitation source.

    Figure 11. X-Ray Fluorescence (XRF) of lead (Pb) from 109Cd.

    Figure 12. Lead (Pb) Fluorescence showing both K and L lines.

    Plating on a Steel Connector

    The spectrum below show the plating on electronic connectors. Since Cd cannot be used in certain connector applications, it can be important to verify its presence or absence. This spectrum clearly demonstrate that Cd and Cr were both used in the plating on the steel connector.

    Figure 13. Cadmium & chromium plated steel

    Gold (Au) Plated on Nickel (Ni)

    Figure 14. Gold plated on nickel

    XRF of Galvanized Steel

    Figure 15. Galvanized Steel: Zinc (Zn) plating on Iron (Fe).

    Process Control: XRF of Smoke Stack in Steel Plant

    Figure 16.

    XRF of a Saint Gaudens US $20 Gold Coin

    Figure 17. XRF analysis of a Saint Gaudens US $20 gold coin with 90% Gold (Au) and 10% Copper (Cu).

    XRF of a Platinum (Pt) Ring

    Figure 18. Analysis of a Platinum (Pt) ring containing Copper (Cu), traces of Nickel (Ni), and Palladium (Pd).

    XRF of a 14k Gold/White Gold (Au) Chain

    Figure 19. Analysis of a 14k Gold/White Gold (Au) chain containing Copper (Cu) and Nickel (Ni).

    XRF of Glass

    Figure 21.

    XRF of Paper

    Figure 22.

    Mössbauer Spectroscopy

    The XR-100CR 7 mm2/300 µm detector is an excellent detector for Mössbauer Spectroscopy. Since the thickness of the detector is only 300 µm, it is very efficient at 14.4 keV and very inefficient at 122 keV. The 57Co spectrum shown here shows a detection efficiency ratio between 14.4 keV and 122 keV of about 1700/1. By using a thin Aluminum absorber between the detector and the source, the 6.4 keV and 7.1 keV peaks can also be eliminated, leaving the 14.4 keV as the only detectable energy peak.

    Figure 24.

    Multi-Element Fluorescence Sample

    Figure 25. X-ray fluorescence (XRF) of multi-element sample from109Cd.

    Low Z Element Fluorescence

    Figure 26. Low (Z) element x-ray fluorescence (XRF) with 6 mm2/500 µm detector.

    241Am Spectrum

    Figure 27. 241Am Spectrum.

  • Options & Additional Info +


    Options and Accessories


    Figure 28a. The X-123 configuration, which includes
    the detector, preamplifier, digital processor, and power
    supplies all in one box.

    Figure 28b. 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 29. XR-100CR Detector Extender Options.

    Additional Information

    Use of Collimators

    All of Amptek’s Si-PIN 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.

    The 6 mm2/13 mm2/25 mm2 X 500 µm detectors exhibit “edge effects” due to partial charge collection at the edge of the detector which produce a secondary peak.

    Figure 30. This plot shows a comparison between a collimated detector and a detector without a collimator.

    Although a small effect, approximately 1% of the counts of the 5.9 keV peak, an internal multilayer (see below) collimator is used on all 6 mm2/13 mm2/25 mm2 X 500 µm detectors in order to remove the secondary peak.

    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).

    Application Notes, Tutorials and Resources

  • Mechanicals +


    1.5 Inch Extender (standard)


    Figure 31. All dimensions in inches ±0.005.

    XR-100 STP File

    No Extender


    Figure 32. All dimensions in inches ±0.005.

    General AXR (T0-8) Mechanical Dimensions


    Figure 33. All dimensions in inches ±0.005.

    TO-8 STP File

    Typical Detector Geometry


    Figure 34. Typical Detector Geometry.

    Right Angle Heat Sink Mechanical Dimensions (supplied with OEM components)

    Figure 35. All dimensions in inches ±0.005.

    Figure 36. Detector, PA210 or PA230 preamplifier, and heat sink assembly.

    Figure 37. Detector, PA210 or PA230 preamplifier, and heat sink assembly.

    Download the Detector with Heat Sink STP File

  • Documentation +