Amptek - Model XR-100T-CdTe - X-Ray & Gamma Ray Detector
The XR100T-CdTe is a thermoelectrically cooled X-ray detector and preamplifier using a CdTe diode. The high stopping power of CdTe makes excellent for applications requiring high detection efficiency at energies up to 100 keV. Its performance, small size, and low cost make it ideal for applications including monitoring of X-ray tubes and ED-XRF on the K lines of rare earth metals, lead, gold, uranium, and other high Z materials.
The XR-100T-CdTe is a high performance x-ray and gamma ray detector, preamplifier, and cooler system using either a 3 x 3 x 1 mm or 5 x 5 x 1 mm Cadmium Telluride (CdTe) diode detector mounted on a two-stage thermoelectric cooler. The XR-100T-CdTe is capable of detecting energies from a few keV to several hundreds of keV, with an efficiency that peaks from 10 to 100 keV.
Amptek has recently introduced two new variations of the CdTe detectors. The traditional -T option provides very good energy resolution but is limited to count rates of < 10 kcps. The new reset option provides the same good energy resolution but up to 100 kcps. A resistive feedback option permits operation at even higher rates but at slightly lower resolution.
Power to the XR-100T-CdTe is best provided by the PX5. The PX5 is DC powered by an AC adapter 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, RS-232, or Ethernet to a PC. The XR-100T-CdTe/PX5 system ensures stable operation in less than one minute from power turn-on.
- Medical X-Ray and Gamma Ray Detection: Mamography and Radiology
- Characterization of x-ray tubes: direct output spectrum, current stability
- X-Ray Fluorescence
- Art and Archaeology
- Portable X-Ray and Gamma Ray Instruments
- X-Ray and Gamma Ray Research
- Nuclear Plant Monitoring
- Uranium and Plutonium Detection
- CdTe Diode Detector
- Thermoelectric (Peltier) Cooler
- Cooled FET
- Temperature Monitor
- Beryllium Window
- Hermetic Package (TO-8)
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.
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
- 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)
- 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