|The XR-100T-CdTe represents a breakthrough in x-ray detector technology by providing "off-the-shelf" performance previously available only from expensive cryogenically cooled systems.|
Model XR-100T-CdTe is a high performance x-ray and gamma ray detector, preamplifier, and cooler system using a 3 x 3 x 1 mm (or 5x5x1) Cadmium Telluride (CdTe) diode detector mounted on a two-stage thermoelectric cooler. Also on the cooler are the input FET feedback components to the charge sensitive preamplifier. The internal components are kept at approximately -30 ºC and can be monitored by an internal temperature sensor. The hermetic TO-8 package of the detector has a light tight, vacuum tight 4 mil (100 µm) Beryllium window.
All the critical connections between the detector and the preamplifier have been made internally to the XR-100T-CdTe to ensure quick, first time operation by the user. The XR-100T-CdTe is provided complete with BNC connectors and power cable.
The XR-100T-CdTe is capable of detecting energies from a few keV to several hundreds of keV!
Figure 1. 57Co Spectrum.
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.
In order to facilitate the electron/hole collection process in the CdTe detector, a + 500 volt potential is applied. This voltage is too high for operation at room temperature, as it will cause excessive leakage, and eventually a breakdown. Since the detector in the XR-100T-CdTe is cooled, the leakage current is reduced considerably, thus permitting the high bias voltage.
The thermoelectric cooler cools both the CdTe detector and the input FET transistor to the charge sensitive preamplifier. Cooling the FET reduces its leakage current and increases the transconductance, which in turn reduce the electronic noise of the system.
In order to further reduce electronic noise, the feedback capacitor and part of the current feedback network to the preamplifier are also placed on the same substrate as the detector and FET. This minimizes parasitic capacitance at the input.
A temperature monitoring sensor is placed on the cooled substrate to provide a direct reading of the temperature of the internal components, which will vary with room temperature. Once the internal temperature gets below minus 10 °C the performance of the XR-100T-CdTe will not change with a temperature variation of a few degrees. Hence, accurate temperature control is not necessary when using the XR-100T-CdTe inside the laboratory.
The XR-100T-CdTe can be operated in air or in vacuum down to 10-8 Torr. There are two ways the XR-100T-CdTe can be operated in vacuum: 1) The entire XR-100T-CdTe 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-100T-CdTe, 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-100T-CdTe to the PX5 outside the vacuum chamber. 2) The XR-100T-CdTe 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. See photograph of XR-100T-CdTe with extender and Conflat and components for vacuum applications.
|Detector type||Cadmium Telluride (CdTe) Diode|
|Detector areas||3 x 3 mm (9 mm2), 5 x 5 mm (25 mm2)|
|Detector thickness||1 mm, click here for efficiency curves|
|Energy resolution @ 122 keV, 57Co||9 mm2: <1.2 keV FWHM, typical|
25 mm2: <1.5 keV FWHM, typical
|Dark counts||<5 x 10-3 counts/sec @ 10 keV < E < 1 MeV|
|Detector window||Be, 4 mil thick (100 µm), click here for transmission curves|
|Preamplifier||Charge Sensitive, with Current Divider Feedback|
|Case Size||3.00 x 1.75 x 1.13 in (7.6 x 4.4 x 2.9 cm)|
|Case weight||4.4 ounces (125 g)|
|Total power||Less than 1 watt|
|Operation conditions||0°C to +40°C|
|Storage and Shipping||Long term storage: 10+ years in dry environment|
Typical Storage and Shipping: -20°C to +50°C, 10 to 90% humidity non condensing
Certificate #: CU 72072412 01
Tested to: UL 61010-1: 2004 R7 .05
CAN/CSA-C22.2 61010-1: 2004
|Preamp power||±8 volts @ 25 mA|
|Detector power||+500 volts @ 1 µA|
|Cooler power||Current = 350 mA maximum|
Voltage = 4 V maximum
Negative signal out (1 kohm max. load)
PX5: direct reading in K through software.
Figure 3. The CdTe detector in the X-123CdTe configuration.
|Preamp output||BNC coaxial connector|
|Power and Signal||6-Pin LEMO connector (Part# ERA.1S.306.CLL)|
|Interconnect Cable||6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 6-Pin LEMO (5 ft. length)|
|Pin 1||Temperature monitor diode|
|Pin 2||+H.V. detector bias, +500 volt|
|Pin 3||-8 volt preamp power|
|Pin 4||+8 volt preamp power|
|Pin 5||Cooler power return|
|Pin 6||Cooler power (0 to +4 volt @ 0.350 A max.)|
|Case||Ground and shield|
Power to the XR-100T-CdTe is provided by the PX5. The PX5 is DC powered by an AC adaptor and provides a variable Digital Pulse Shaping Amplifier (0.2 µs to 100 µs peaking time), the MCA function, and all necessary power supplies for the detector and preamplifier. The PX5 connects via USB, RS232, or Ethernet to a PC.
The XR-100T-CdTe/PX5 system ensures stable operation in less than one minute from power turn-on.
Figure 4. This diagram shows the internal connections between the AXR hybrid sensor and the electronics within the case, as well as the external connections to the PX5.
Figure 5. Throughput for various peaking times. The XR-100T-CdTe provides the best resolution between 1 and 6 µs peaking time.
For 1 mm thick CdTe and various Be window thicknesses (window dominates low energy response).
Figure 7. Log-log plot of interaction probability between 1 keV and 1 MeV.
Figure 8. Linear plot of interaction probability between 10 keV and 250 keV.
For more information on the efficiency of the CdTe detector see the ANCZT-1 application note.
Efficiency Package: A ZIP file of coefficients and a FAQ about efficiency. This pacakge is provided for general information. It should not be used as a basis for critical quantitative analysis.
XR-100T-CdTe Specifications in PDF format (105 k)
Revised May 27, 2011