PORTABLE GAMMA AND X-RAY ANALYZERS BASED ON PELTIER COOLED P-I-N CdTe AND Si (Li) DETECTORS

Several portable instruments are designed using previously reported CdTe detector technology and Peltier cooled Si(Li) detectors. These can be divided into 3 groups according to their energy ranges: 1) 3 to 30 keV XRF analyzers, 2) 5 to 120 keV wide range XRF analyzers and 3) γ-ray spectrometers for operation up to 1500 keV. The instruments with CdTe detectors are used to inspect several hundred samples in situ during a working day in applications such as a metal alloy verification at customs control. Heavy metals are identified through a 3 − 100 mm thick package with these instruments. Surface contamination by heavy metals (for example toxins such as Hg, Th and Pb in housing environmental control), the determination of Pb concentration in gasoline, geophysical control in mining, or nuclear material control are other applications. The weight of these XRF probes is about 1 kg and two electronic designs are used: one with embedded computer and another based on a standard portable PC. The instruments have good precision and high productivity for measurements in situ. The detection limit of Ce is about 0.03 %, when measured in the presence of 10 % barium for 15 seconds. When measuring K-shell X-ray of heavy metals contamination the detection limit is about 0.1 mg/cm for 15 s. Two types of probes for γ-spectrometry with small and large (> 30 mm ) detector volumes provide both high and low activities of nuclear fuel analysis. The maximum distance between the probes and the electronics unit is 20 m. The γ-spectrometers are equipped with electronics to correct signal distortion due to slow carrier effects. This allows one to achieve an energy resolution of about 2.5 keV at 662 keV. Several modes to process spectra are possible including the semiquantitative and the total real shape fitting.