Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-06 Cooperative journals: 《天文研究与技术》
Abstract： The Large High Altitude Air Shower Observatory (LHAASO) is located in Haizi Mountain, Daocheng County, Sichuan Province, with an average altitude of 4410 meters. It belongs to a typical alpine climate with rapid weather changes. The Wide Field of view Cherenkov Telescope Array (WFCTA), as one of the three major observation arrays of LHAASO, requires operation in the clear nights. To ensure the normal operation of the telescope, it is necessary to constantly detect rain and snow conditions, so that WFCTA can be closed promptly in case of rain and snow weather. However, due to the low temperature, traditional rain and snow sensors cannot work properly at the LHAASO site. Therefore, the heating device was induced to make the rain and snow sensors fit the weather in Daocheng. After designing and testing in the laboratory, the on-site experiment was also carried out at the LHAASO site. The results show that the high-sensitivity rain and snow sensor can maintain the temperature above ice point at the surface of the sensor in horrible weather, and can effectively monitor rain and snow in real-time at the LHAASO site, which can provide strong support for the normal operation of the Wide Field of view Cherenkov Telescope Array.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-04 Cooperative journals: 《天文研究与技术》
Abstract： The Large High Altitude Air Shower Observatory (LHAASO) is situated in Haizi Mountain, Daocheng County, Sichuan Province, at an average altitude of 4 410 meters. The laser calibration system is a vital component of the Wide-Field-of-view Cherenkov Telescope Array (WFCTA) in LHAASO, utilized to calibrate the absolute gain of WFCTA for the received photons. The energy measurement system in the laser calibration system comprises an energy sensor, an energy meter, and a temperature control system, primarily employed to precisely measure the energy of the pulsed laser beam emitted into the WFCTA field of view. This paper primarily focuses on the relative calibration and performance of the energy sensor, and proposes a temperature control system to ensure the energy sensor′s normal operation in the harsh plateau environment. The accuracy of energy measurement about laser pulse can be improved by relative calibration. The performance test results of the energy sensor demonstrate that the non-uniformity is less than 1.5% within the circular area with a diameter of 8 mm centered on the energy sensor. The incident angle of the laser beam has negligible impact on the measurement of the laser pulse energy by the energy sensor, but the reflection of the laser by the energy sensor can damage the laser when the laser beam is vertically incident. Hence, avoiding the vertical incidence of the laser beam on the energy sensor is crucial. Furthermore, the energy sensor exhibits a strong temperature effect. Therefore, an independent temperature control system is developed in this paper to ensure the energy sensor′s normal operation, fulfilling the experiment′s requirements. These research works serve as the foundation for the laser calibration system′s regular operation and functioning.
Subjects: Astronomy >> Astrophysical processes submitted time 2021-09-29 Cooperative journals: 《天文研究与技术》
Abstract：三维升降转台是高海拔宇宙线观测站(LHAASO)广角切伦科夫望远镜阵列(WFCFA)成像激光雷达标定系统的核心组成部分，主要由慢控子系统、机械子系统和标准零点子系统构成，用于精确控制激光束的出射方向。本文采用高精度数字图像处理技术对三维升降转台的性能进行研究，结果表明其旋转和升降定位精度分别为0.005°和0.056 mm、重复精度分别为0.003°和0.075 mm，满足成像激光雷达标定系统的实验要求。三维升降转台的自动控制巡航功能，有效减少了人工干预，提高了系统远程使用的可靠性和效率。标准零点的校准功能可以有效地监测三维升降转台的定位精度并且在失准的情况下，能够实现远程校准，以确保三维升降转台长期高精度稳定运行。
Subjects: Astronomy >> Astrophysical processes submitted time 2021-07-06 Cooperative journals: 《天文研究与技术》
Abstract：芯位重建是地面宇宙线探测实验开展物理分析的前提和基础。本文基于广延大气簇射的对称性，结合探测器的特征，提出一种新的芯位重建算法——椭圆拟合法，用于模拟数据的芯位重建并与重心法对比。对于能量大于1 TeV的芯内宇宙线质子事例，芯位分辨率在小于5m,明显优于重心法；对于临近阵列边界20 m范围内能量大于1 TeV的事例芯位分辨率小于10 m，相比于传统方法有显著优势。由于该方法能够在保证精度的前提下重建边沿事例和部分芯外事例，极大地增大了事例利用率，对于1-10 PeV质子事例的探测器阵列面积利用率比重心法增大1倍左右。
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