LHAASO地面簇射粒子阵列在线实时分布式数据处理

Online real-time distributed data process of LHAASO ground shower particle array

高海拔宇宙线观测站(Large High Altitude Air Shower Observatory,LHAASO)是"十二五"批复立项的国家重大科技基础设施,是我国海拔最高的大科学基础设施之一,核心目标是探索高能宇宙线。作为LHAASO的重要组成,地面簇射粒子阵列(square KiloMeter detector Array,KM2A)建成探测阵列面积高达1 km^2。不同于大多高能物理实验,KM2A共约6 500路通道,总输入约546 MB·s^(-1),没有硬件触发功能,因此,需要软件完成触发与数据处理。采用基于标准以太网和TCP/IP协议的数据传输方案,接收包括所有探测器单元同一时间的全部组包数据,利用配置的触发算法对数据包进行在线处理与计算,将具有物理意义的数据提取、打包,组成不同的有物理标签的事例,并按照配置的输出规则将这些事例送出至不同的接收方,实现了实时分布式算法调度与数据处理。软件可以实时触发筛选,降低数据量,减轻传输与存储的负担。软件已在4 410 m海拔实验现场的数据中心投入使用,至今为止一直运行良好。

[Background]The large high altitude air shower observatory(LHAASO)is a major national science and technology infrastructure approved for the 12th Five-Year Plan.It is one of the scientific infrastructures with the highest altitude in China and its core goal is to explore high-energy cosmic ray.As an important component of LHAASO,the ground shower particle array(KM2A)has a huge total area of one square kilometer.Unlike most highenergy physics experiments,the KM2A has a total of about 6500 channels,and a total input bandwidth of about 546 MB?s-1.There is no hardware trigger function in KM2A.[Purpose]This study aims to design and implement a software for KM2A to complete the trigger and real-time data processing.[Methods]Data transmission scheme based on standard Ethernet and TCP/IP protocol was employed to receive all packet data including all detector units at the same time.Online processing and calculation of data packets were achieved by using the configured trigger algorithm.Data with physical significance were extracted and packaged to form different events with physical labels,then these events were sent to different receivers according to the configured output rules.By using distributed technology and task division,this software was able to finish real-time data processing through selectable algorithm scheduling.[Results&Conclusions]The software is able to trigger KM2A in real time,reduce the amount of data,and lessen the burden of transmission and storage.It has been put into use in the data center of 4410 m altitude experiment site,and has been running well so far.