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BackgroundComplete kinematic measurements in the medium or high-energy region is a common experimental method to study the structure and properties of exotic nuclides on the neutron-rich side. The experiment setup in the Cooling Storage Ring - Radioactive Ion Beam Line in Lanzhou (CSR-RIBLLII), a typical nuclear external target facility, comprises many detectors with different requirements. The anticoincidence (Veto) detector is an essential part of the external target facility for eliminating the interference of charged particles and measuring medium or high-energy neutrons with high reliability and performance by combining them with a neutron wall detector. The original Veto detector with photomultiplier (PMT) readouts has many disadvantages, such as low detection efficiency and poor uniformity, resulting in significant differences or contradictions between experimental and calculation results.PurposeThis study aims to upgrade the original Veto detector using wave length shifter fiber (WLS) and silicon photomultiplier (SiPM) to improve the detection efficiency of charged particles.MethodsFirstly, a new configuration for the anticoincidence Veto detector unit was designed and the detector thickness was increased by 5 mm compared to the previous Veto detector, resulting in a final thickness of 1 cm. The Veto detector was embedded with 15, 7, and 3 WLS fibers from both ends, and read using SiPM. Furthermore, to systematically explore the performance of the detector unit, a linear relationship was calibrated between the number of photons of the SiPMs and the number of Analog-to-Digital Converter (ADC) channels. This relationship was used to accurately calculate the threshold value, laying a foundation for calculating detection efficiency. Then, based on Multi-Wire Proportional Chamber (MWPC), a detection efficiency test platform was established, and time position conversion and track selection data analysis methods were developed as test methods. Finally, a detailed test on the whole and each part of the anticoincidence Veto detector unit was carried out on the MWPC test platform.ResultsTest results show the highest anticoincidence efficiencies of SiPMs at both ends for the Veto detector embedded with 15, 7, and 3 WLS fibers are 99.99%, 99.94%, and 99.82%, respectively; increased by over 22.74% compared with the original Veto detector.ConclusionsThe new Veto detector based on WLS fiber and SiPM readout meets the needs of the CSR-RIBLLII external target facility.

Balance field length is one of the important technical indexes in civil aircraft design and operation, and it has an important influence on civil aircraft economy, safety and universality, and also determines the aircraft decision speed. The concept and calculation method of balance field length and the relation between balance field length and decision speed are introduced, as well as three sensitivity analysis theories are list. Taking a civil aircraft as an example, the effects of takeoff weight, airport height, wind speed, temperature, runway slope and other factors on the balance field length is studied. The sensitivities of different factors to balance field length are calculated based on the above three analysis theories. The results show that the length of balance field and the decision speed increased with the increase of takeoff weight, airport height, tailwind speed and temperature. They decreased with the increase of headwind speed. The effect of runway slope on the balance field length could be negligible. The positive and negative correlations of those parameters obtained by the sensitivity analysis methods are consistent, and the sensitivity values of the five variables are ranked as follows: takeoff weight> wind speed> airport height> temperature> runway slope.