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xr100t-cdte x-ray and gamma-ray detector

xr100t-cdte x-ray and gamma ray detector photo xr100t-cdte x-ray and gamma ray detector diagram
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.

Features

  • CdTe Diode Detector
  • Thermoelectric (Peltier) Cooler
  • Cooled FET
  • Temperature Monitor
  • Beryllium Window
  • Hermetic Package (TO-8)

Additional Information

Applications

Application Notes

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!

xr100t-cdte x-ray and gamma ray detector 57co spectrum
Figure 1. 57Co Spectrum.

Theory of Operation

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.

Vacuum Operation

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.


Specifications

Model XR-100T-CdTe X-Ray and Gamma Ray Detector


General
Detector typeCadmium Telluride (CdTe) Diode
Detector areas3 x 3 mm (9 mm2), 5 x 5 mm (25 mm2)
Detector thickness1 mm, click here for efficiency curves
Energy resolution @ 122 keV,  57Co9 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 windowBe, 4 mil thick (100 µm), click here for transmission curves
PreamplifierCharge Sensitive, with Current Divider Feedback
Case Size3.00 x 1.75 x 1.13 in (7.6 x 4.4 x 2.9 cm)
Case weight4.4 ounces (125 g)
Total powerLess than 1 watt
Operation conditions0°C to +40°C
Storage and ShippingLong term storage: 10+ years in dry environment
Typical Storage and Shipping: -20°C to +50°C, 10 to 90% humidity non condensing
TUV CertificationTUV Certification
Certificate #: CU 72072412 01
Tested to: UL 61010-1: 2004 R7 .05
CAN/CSA-C22.2 61010-1: 2004

Inputs
Preamp power±8 volts @ 25 mA
Detector power+500 volts @ 1 µA
Cooler power
 
Current = 350 mA maximum
Voltage = 4 V maximum

Outputs
Preamplifier:
Sensitivity
Polarity

0.82 mV/keV
Negative signal out (1 kohm max. load)
Temperature monitor:
Sensitivity


PX5: direct reading in K through software.

Options

x-123 configuration
Figure 3. The CdTe detector in the X-123CdTe configuration.

XR-100T-CdTe Connectors

Preamp outputBNC coaxial connector
Power and Signal6-Pin LEMO connector (Part# ERA.1S.306.CLL)
Interconnect Cable6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 6-Pin LEMO (5 ft. length)

6-Pin Lemo Connector Pin Out

Pin 1Temperature monitor diode
Pin 2+H.V. detector bias, +500 volt
Pin 3-8 volt preamp power
Pin 4+8 volt preamp power
Pin 5Cooler power return
Pin 6Cooler power (0 to +4 volt @ 0.350 A max.)
CaseGround and shield


PX5 Digital Pulse Processor, MCA, and Power Supply for the XR-100T-CdTe

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.

px5 digital pulse processor, mca, and power supply block diagram
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.

throughput, input vs. output count rate for silicon drift detector
Figure 5. Throughput for various peaking times. The XR-100T-CdTe provides the best resolution between 1 and 6 µs peaking time.


CdTe Detection Efficiency

For 1 mm thick CdTe and various Be window thicknesses (window dominates low energy response).

xr100t-cdte x-ray and gamma ray detector CdTe 1 mm thick efficiency curve - log scale
Figure 7. Log-log plot of interaction probability between 1 keV and 1 MeV.

xr100t-cdte x-ray and gamma ray detector CdTe 1 mm thick efficiency curve - linear scale
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.


Additional Information

CdTe/CZT Application Notes

XR-100T-CdTe Specifications in PDF format (105 k)


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Revised May 27, 2011