Gamma-Ray Response of Semi-Insulating CdMnTe Crystals
Semi-insulating Cd0.9Mn0.1Te:In crystals are grown by vertical Bridgman method. The segregation coefficient of Mn in CdTe is nearly 1 so that all the CdMnTe samples obtained from one ingot have nearly a same Mn composition. Also sulfur-based passivation effectively prevent the formation of Te-oxide but large amount of Mn exist as a MnO on the CdMnTe surface. The resistivity of CdMnTe samples are low 1010 Omegacm and well resolved 241Am gamma peaks are seen for all detectors. The difference in spectral response can be attributed to the effect of excess Te and conductivity change due to over-compensation induced by indium segregation in CdMnTe. The mobility-lifetime products evaluated from the dependence of peak location on the bias voltage are 1 times 10-3 cm2/V. The higher mobility-lifetime products in our CdMnTe crystals than other previous reports are assumed due to minimization of impurity contents in MnTe by several zone refining process.
Characteristics of doped indium in Cd0.9Zn0.1Te grown by the Bridgman method
The Cd1−xZnxTe crystal is one of the key materials for room temperature x-ray and gamma-ray detectors. By the vertical Bridgman method (VBM) several indium (In) doped Cd0.9Zn0.1Te (Cd0.9Zn0.1Te: In) ingots have been grown. The characteristics of In in these ingots have been studied. It is found that the segregation coefficient of In in Cd0.9Zn0.1Te is 1.3. In is enriched at the grain boundary but homogeneously distributed inside the grains in the as-grown crystals. IR transmission measurements reveal that Cd0.9Zn0.1Te: In is almost opaque to IR emission when the wave number is larger than 1000 cm−1, then is 24% transparent when the wave number is decreased to lower than this value. This phenomenon indicates that some In atoms are interstitial impurities and act as neutral donors. These In atoms bring out a donor level of 0.12 eV below the bottom of conduction band for Cd0.9Zn0.1Te: In. Resistivity measurements reveal that the resistivity is highly increased after doping of In into Cd0.9Zn0.1Te, and the In concentration is positive to raise the resistivity of Cd0.9Zn0.1Te: In.
Ignition and burning rates of segregated waste combustion in packed beds.
Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results. Two successive stages of combustion were identified for both samples: the propagation of ignition front into the bed and combustion of the fuel above the ignition front. The burning rate of cardboard reached a peak of about 300 kg/m(2)h at the air flowrate of 936 kg/m(2)h and decreased at higher air flowrates. For waste wood, both the ignition and burning rates increased in the tested range of the air flowrate up to 702 kg/m(2)h, of which the values were very close to those for the cardboard. The model prediction was in good agreement with the test results for waste wood. However, the burning rate for cardboard was under-predicted due to strongly irregular shapes of the fuel.