[en] In order to provide accurate and reliable data for the study of nuclear signal digital processing, the real-time nuclear signal readout system based on AXI4 bus is designed. The system takes Zynq series chip as the core, caches high-speed streaming data by ping-pong mode, uses AXI4 bus to realize high-speed data communication between programmable logic array and internal microprocessor, and finally transmits the data in microprocessor to PC in real time through gigabit Ethernet, and saves the data to file. Use NaI (T1) detector as experimental detector and ¹³⁷Cs source as experimental source, 25 MHz ADC was used to test the design system. Experimental results show that the system is actually measured 180 s, which can read 9 GB nuclear signal data in real time and achieve high-speed and zero-loss readout. The long-term stability test of 168 h shows that the maximum data loss rate of the system is 0.0146%, which meets the requirements of long-term stability. (authors)

[en] The Pt/Si/Ta/Ti multilayer metal contacts on 4H–SiC are annealed in Ar atmosphere at 600 °C–1100 °C by a rapid thermal processor (RTP). The long-term thermal stability is evaluated by aging the annealed contact at 600 °C in air. The contact’s properties are determined by current–voltage measurement, and the specific contact resistance is calculated based on the transmission line model (TLM). Transmission electron microscope (TEM) and energy-dispersive x-ray spectrometry (EDX) are used to characterize the interface morphology, thickness, and composition. The results reveal that a higher annealing temperature is favorable for the formation of an Ohmic contact with a lower specific contact resistance, and causes the rapid degradation of the Ohmic contact in the aging process. (paper)

[en] Energy resolution is affected by the intrinsic energy resolution of the detector, ballistic deficit, pile-up pulses and noise. Pile-up pulses become the dominant factor that degrades energy resolution after the system is established, so pile-up rejection is often applied to obtain good energy resolution by discarding pulses that are expected to be contaminated by pile-up. However, pile-up rejection can reduce count rates and thus lower the measurement precision. In order to improve count rates and maintain energy resolution, a new method of pile-up pulse identification based on trapezoidal pulse shaping is presented. Combined with pulse width discrimination, this method is implemented by recording pulses that are not seriously piled up. Some experimental tests with a Cu-Pb alloy sample are carried out to verify the performance of this method in X-ray spectrometry. The results show that the method can significantly improve count rates without degrading energy resolution. (authors)

[en] We present an optical design for the lens depth of a periscope-type 3 × zoom lens with 8-megapixel sensor in mobile phone. In the practice application, the lens depth of zoom lens must be less than the thickness of the mobile phone mechanism. The lens depth is thus the upper size limit of the prism thickness or the maximum surface aperture in the Y-direction of the zoom lens. The zoom lens in the designed system has an F-number of F/3.5 to F/5.5, a focal length of 4.514 mm to 13.442 mm, the half field angle in the x-direction is 23.96° to 8.488°, and the half field angle in the y-direction is 14.035° to 4.798°. The smallest lens depth of the zoom lens is 5.377 mm. These results show that the depth of a periscope-type zoom lens can be embedded in the mobile phone.