The Advantage of Detector with CdTe Sensor for Hard Radiation
Photon-counting detectors with silicon (Si) sensors are commonly used in modern laboratory X-ray diffractometers. However, Si sensors exhibit relatively low quantum efficiency for high-energy X-rays, such as those produced by molybdenum (Mo) and silver (Ag) radiation. This limitation can be significantly mitigated by using detectors equipped with cadmium telluride (CdTe) sensors, which offer much higher efficiency in this energy range.
Introduction
The most commonly used X-ray source in a powder
X-ray diffractometer (PXRD) is with copper (Cu) anode. It is primarily chosen for its high flux, excellent heat dissipation, and extended tube lifetime. X-ray sources with different anode materials are also used depending on the application. For example, a Co anode is preferred for Fe- and Co-containing samples to eliminate X-ray fluorescence. Similarly, a Cr anode is used for this purpose and for specific applications such as residual stress analysis. X-rays emitted from Cu, Co, and Cr anodes are considered 'soft radiation' due to their relatively longer wavelengths and lower energy.
In contrast, X-ray sources with Mo and Ag anodes are classified as 'hard radiation' because of their shorter wavelength and higher energy. These sources are mainly used for two purposes: (a) Their higher X-ray penetration depth allows for the study of thicker samples in transmission mode. (b) They provide a higher q-range, which is useful for applications such as Pair Distribution Function (PDF) analysis.
Modern photon-counting detectors with standard Si sensors can detect photons from both soft and hard radiation, thanks to their thicker Si sensor. However, detector with CdTe sensor is recommended for hard radiation due to their higher quantum efficiency. This increased efficiency results from the heavy elements in the detector (Cd and Te), which have high stopping power, especially for high-energy X-rays such as Mo and Ag in laboratory diffractometers. Additionally, CdTe sensors ensure excellent data collection for soft radiation as well.
XRDynamic 500, an automated multipurpose powder X-ray diffractometer from Anton Paar, offers the flexibility to use detectors with either Si or CdTe sensors. Additionally, it allows for easy exchange of the X-ray tube and detector, along with fully automated instrument alignment routines.
This report highlights the advantages of using a detector with a CdTe sensor, particularly for hard radiation.
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