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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.

Laser illumination is considered to be a revolution of new lighting technology due to its high efficiency and pure color. Similar to the white Light Emitting Diode (LED), phosphor convertor is also a necessary component to generate light in laser illumination technology. In order to improve the performance of laser, designing and optimizing phosphor with high color purity is an effective method. In our study, the pure-red Sr2GdTaO6:Er3+/Yb3+ powders were synthesized and optimized using a high-temperature solid-phase method. The phosphor structure of the obtained phosphors was analyzed through X-ray diffraction (XRD), confirming all products are Sr2GdTaO6 polycrystalline powders. Theoretical models, optimized through experimental design, established regression equations correlating Er3+/Yb3+ doping concentrations with luminescence intensity. Leveraging a genetic algorithm, the optimal solutions for the equations were calculated, resulting in Er3+ and Yb3+ doping concentrations of 4.99% and 24.85% under 980 nm laser excitation and 4.95% and 23.19% under 1550 nm laser excitation, respectively. Under the same conditions, the up-conversion fluorescence emission spectra of the samples were measured, revealing strong green and red emissions with peaks at 550 nm, 563 nm, and 663 nm, corresponding to transitions from 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 energy levels. For the optimal samples at 980 nm and 1550 nm, the relationship between up-conversion luminescence and laser operating current was explored, indicating that the up-conversion luminescence in these two cases is a two-photon and three-photon process, respectively. The up-conversion luminescence mechanism was analyzed and discussed in detail. Additionally, the relationship between up-conversion fluorescence and temperature was investigated for the optimal samples, revealing excellent temperature-sensing characteristics for up-conversion emissions excited by both 980 nm and 1550 nm lasers. The CIE coordinates (0.5986, 0.3973) and (0.7089, 0.2910) of the optimal sample were calculated under excitation at 980 nm and 1550 nm wavelengths. [ABSTRACT FROM AUTHOR]