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X-123CdTe Complete X-Ray & Gamma Ray Spectrometer

NEW!!! Now available with Graphite Windows that are 1 mil (25 µm) thick, made of 100% carbon, and equivalent in Energy Transmission to 4 mil (100 µm) Be windows.

The X-123CdTe combines in a single package Amptek’s standard, high performance X-ray spectroscopy components: the CdTe detector, a preamplifier, a DP5 digital pulse processor (DPP) and MCA, and a PC5 power supply. The result is a complete integrated system which can fit in your hand.

X-123 represents the culmination of 14 years of X-ray detector development at Amptek. Our philosophy has always been to create small, low power, high performance instruments while keeping them simple to operate. The X-123CdTe exemplifies this philosophy in a single package. All that is needed is a +5 Volts DC input and a USB or RS-232 connection to your computer.


  • Compact Integrated System
  • Simple to Operate
  • Small Size (2.7 x 3.9 x 1 in, 7 x 10 x 2.5 cm)
  • Low Power (2.5 Watts)
  • Light Weight (6.3 oz, 180 g)
  • USB and RS-232 Communication



  • CdTe for X-Ray and Gamma-Ray detection
  • 2-Stage thermoelectric cooler
  • Area: 25 mm2
  • Thickness: 1 mm (0.75 mm available on special order)

Typical Performance

  • Resolution at 122 keV <1.5 keV FWHM
  • Optimum energy range: 5 keV to 150 keV
  • Maximum count rate: Up to 2 x 105 cps

Detailed performance depends on detector and configuration, which can be optimized for special applications.

Figure 1. 57Co Spectrum.

Contact us for more information today!

  • Description +

    X-123CdTe Theory of Operation

    Amptek’s specialty is X-ray and gamma-ray spectrometers, which are small, low power, high performance, and simple to operate. The X-123CdTe combines in a single package Amptek’s standard, high performance X-ray spectroscopy components: the XR-100CdTe detector and preamplifier, DP5 digital pulse processor and MCA, and PC5 power supply. The result is a complete integrated system which can fit in your hand. In many commercially available systems, the preamplifier alone has more size, mass, and power than this integrated system. It requires only 2 connections to run: +5 VDC power and a standard RS-232 or USB bus. With the X-123CdTe, anyone can rapidly obtain high quality X-ray and gamma-ray spectra.

    X-rays & gamma rays interact with CdTe atoms to create an average of one electron/hole pair for every 4.43 eV of energy lost in the CdTe. Depending on the energy of the incoming radiation, this energy loss is dominated by either the photoelectric effect or Compton scattering. The probability or efficiency of the detector to “stop” the incoming radiation and create electron/hole pairs increases with the thickness of CdTe.

    The detector 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 digital pulse processor which replaces both the shaping amplifier and multichannel analyzer (MCA) found in most analog systems. The use of digital technology improves several key parameters: (1) better performance, specifically better resolution and operation at higher count rates; (2) greater flexibility since more configuration options are available and they are selected by software over a RS-232 interface, and (3) improved stability and reproducibility. The DP5 digitizes the preamplifier output, applies real-time digital processing to the signal, detects the peak amplitude (digitally), and bins this value in its histogramming memory, generating an energy spectrum. The spectrum is then transmitted over the DP5’s interface to the user’s computer. The Amptek DP5 has 6 main function blocks to implement these functions: (1) an analog prefilter; (2) an ADC; (3) a digital pulse shaper; (4) pulse selection logic; (5) histogram logic, and (6) interfacing hardware (which includes a microcontroller) and software.

    The power supply is Amptek’s PC5, a single board. The input is approximately +5 VDC with a current of about 250 mA. The PC5 uses switching supplies to produce all the low voltages required for the digital processor and the preamplifier. It also includes a high voltage multiplier to produce the detector bias voltage, typically 500 V for 1 mm thick CdTe, but variable up to 750 V, and supply for the thermoelectric cooler which provides closed loop control with a maximum temperature differential of 85 °C.

    The complete system is packaged in 7 x 10 x 2.5 cm3 aluminum box, with the detector mounted on an extender. In its standard configuration, only two connections are required: power (+5 VDC) and serial (either USB or RS-232). The DP5 board supports several additional inputs and outputs, if the X-123CdTe will be integrated with other equipment. This includes an MCA gate, a memory buffer select signal, timing outputs, and SCA ouputs.

    Figure 4. X-123CdTe Architecture and Connection Diagram.

  • Specifications +

    X-123CdTe Specifications

    System Performance

    Energy resolution @ 122 keV,  57Co <1.5 keV FWHM, typical
    Energy Range 5 to 150 keV. May be used at higher energy with lower efficiency, contact Amptek.
    Maximum Count Rate Depends on peaking time. Recommended maxima for 50% dead time with pile-up-rejection enabled are shown below.


    DP5 Peaking Time (µs) 2.4 6.4 25.6
    Shaping Time (µs) 1.0 2.9 11.6
    Recommended max rate 1.2 x 105 4.6 x 104 1.2 x 104

    Detector and Preamplifier

    Detector Type CdTe (also available with Si-PIN or SDD detector)
    Detector Area 25 mm2
    Detector Thickness 1 mm, see Figures 2 and 3 below for efficiency curves
    Window Thickness Graphite: 1mil thick (25 µm)
    Be: 4 mil thick (100 µm)
    Thermoelectric Cooler 2-stage
    Preamplifier Type – Amptek custom design Reset

    Pulse Processor

    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
    Peaking Time 24 software selectable peaking times between 0.8 and 102 µs, approximately log spaced, corresponding to semi-gaussian shaping times of 0.4 to 45 µs.
    Dead Time Total dead time is 1.05 times the peaking time. No conversion time.
    Fast Channel Pulse Pair Resolving Time 120 ns


    Number of Channels Software selectable to: 8k, 4k, 2k, 1k, 0.5k, or 0.25k channels
    Presets Time, total counts, counts in an ROI, counts in a single channel


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


    Nominal Input +5 VDC at 500 mA (2.5 W) (typical). Current depends strongly on detector ΔT. Ranges from 300 to 800 mA at 5 VDC. AC adapter provided.
    Input Range 4 V to 6 V (300 to 200 mA, 500 mA max)
    High Voltage Supply Internal multiplier, set to 500 V, adjustable to 750 V
    Cooler Supply Closed loop controller with Delta_Tmax = 85 °C

    General and Environmental

    Connectors, Interface and Software

    Operating temperature -20 °C to +50 °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: -20 °C to +50 °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
    USB Standard USB Mini 1.1 jack
    RS-232 Standard 2.5 mm stereo audio jack.


    Tip Transmit To PC Receive DB9 Pin 2 (DB25 Pin 3)
    Ring Receive To PC Transmit DB9 Pin 3 (DB25 Pin 2)
    Sleeve Ground To PC Ground DB9 Pin 5 (DB25 Pin 7)
    Ethernet Standard Ethernet connector (RJ-45)
    Power Hirose MQ172-3PA(55), Mating plug: MQ172-3SA-CV
    Auxiliary 2×8 16-pin 2 mm spacing (Samtec part number ASP-135096-01). Mates with cable assembly (Samtec P/N TCMD-08-S-XX.XX-01. Top row odd pins, bottom row even pins. Top right pin = 1, bottom right pin = 2.


    Pin # Name Pin # Name
    1 SCA1 2 SCA2
    3 SCA3 4 SCA4
    5 SCA5 6 SCA6
    7 SCA7 8 SCA8
    9 AUX_IN_1 10 AUX_OUT_1
    11 AUX_IN_2 12 AUX_OUT_2
    13 IO2 14 IO3
    15 GND 16 GND
    DPPMCA The X-123CdTe can be controlled by the Amptek DPPMCA display and acquisition software. This software completely controls and configures the X-123CdTe, 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-123CdTe comes with a free Software Developer’s Kit (SDK). The user can use this kit to easily write custom code to control the X-123CdTe 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-123CdTe 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-123CdTe 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.

    CdTe Detection Efficiency

    For 1 mm thick CdTe and 4 mil Be or 1 mil Graphite window (window dominates low energy response, 1 mm thickness defines high energy response).

    Figure 2. Log-log plot of interaction probability between 1 keV and 1 MeV.

    Figure 3. Linear plot of interaction probability between 10 keV and 250 keV.

    For more information on the efficiency of the CdTe detector see the AN-CdTe-001 application note.

    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.

  • Applications Notes +

    Application Notes

    Typical Countrate of XR-100CdTe 3x3x1 mm3 (5x5x1 mm3) from Selected Nuclides

    Nuclide Activity Radiation Level on Contact (mR/hr) Countrate on Contact (CPS) Radiation Level at 10 cm away (mR/hr) Countrate at 10 cm away (CPS)
    137Cs 0.1 mCi (3.7 MBq) 25 500 (1,400) 2.0 11 (30)
    57Co 0.1 mCi (3.7 MBq) 10 5,500 (15,000) 0.5 50 (140)
    Uranium Oxide (Natural UO3) 0.6 mCi (21 MBq) 1 22 (60) 0.3 5 (15)
    241Am 10 µCi (0.37 MBq) 10 1,400 (3,800) 0.5 20 (50)


    Please refer to the TO-8 detector drawing.

    1. The TO-8 cover is made of Ni, 14 mm diameter, 0.250 mm thick.
    2. The Detector element is located 1.27 mm behind the 100 µm thick Be window.
    3. The detector cavity is vacuum.
    4. The size of the detector is either 3x3x1 mm3 or 5x5x1 mm3. (*)
    5. The top contact is Pt of 0.2 µm thickness (- side).
    6. The bottom contact is In of 1 µm thick (+ side).
    7. The detector is placed on a ceramic substrate of 0.75 mm thickness.
    8. The thickness of the cooler is 2.75 mm.
    9. The base of the TO-8 package is made of steel (Kovar), 1.5 mm thick.

    (*) Depending on which options are selected. Typical Kovar Composition

    • Carbon – 0.02
    • Silicon – 0.20
    • Manganese – 0.30
    • Iron – 53.48
    • Cobalt – 17.0
    • Nickel – 29.0

    Do NOT use RTD when trying to compare theoretical results to actual measurements. The following applications notes may be useful when modeling the XR-100TCdTe response

    For an excellent guide to modeling solid-state detectors (SSD), please consider the following paper:

    “A modeling tool for detector resolution and incomplete charge collection” by Jorge E. Fernández, Viviana Scot and Lorenzo Sabbatucci

    The authors present an easy to use modeling tool that can be tailored to a specific detector. The tool can be used with three detector types: solid-state detectors, scintillators, and gas proportional counters. The authors used the Amptek CdTe detector as an example of peak shape.

  • Applications +

    Example Spectra

    Figure 1.

    Figure 2.

    Figure 3.

    Figure 4. 

    Figure 5.

  • Options & Additional Info +


    • 0.75 mm thick detector available
    • Collimator kit
    • Vacuum applications
    • OEM & special applications
    • For maximum flexibility and performance see the XR-100CdTe/PX5 configuration.

    Additional Information

  • Mechanicals +

    Mechanical Dimensions

    Figure 1. Mechanical Dimensions

    CdTe Detector Module

    Figure 2. CdTe Detector module mechanical.

    Mounting Hardware

    Figure 3. X-123CdTe with mounting plate and right angle bracket.

    Figure 4. X-123CdTe Mounting Plate.

    Figure 5. X-123CdTe right angle mounting bracket.

    Download the X-123 STP File

  • Documentation +