# Data and clock transmission interface for the WCDA in LHAASO

## TL;DR

This paper presents a high-precision data and clock transmission interface for the WCDA in LHAASO, achieving synchronization better than 50 ps and data throughput exceeding requirements using White Rabbit technology over fiber.

## Contribution

It develops and tests a prototype interface utilizing White Rabbit switches for synchronized data and clock transfer in LHAASO WCDA, ensuring high precision and throughput.

## Key findings

- Clock synchronization better than 50 ps.
- Data throughput exceeds 400 Mbps per FEE.
- Successful prototype validation for LHAASO WCDA.

## Abstract

The Water Cherenkov Detector Array (WCDA) is one of the major components of the Large High Altitude Air Shower Observatory (LHAASO). In the WCDA, 3600 Photomultiplier Tubes (PMTs) and the Front End Electronics (FEEs) are scattered over a 90000 m2 area, while high precision time measurements (0.5 ns RMS) are required in the readout electronics. To meet this requirement, the clock has to be distributed to the FEEs with high precision. Due to the "triggerless" architecture, high speed data transfer is required based on the TCP/IP protocol. To simplify the readout electronics architecture and be consistent with the whole LHAASO readout electronics, the White Rabbit (WR) switches are used to transfer clock, data, and commands via a single fiber of about 400 meters. In this paper, a prototype of data and clock transmission interface for LHAASO WCDA is developed. The performance tests are conducted and the results indicate that the clock synchronization precision of the data and clock transmission is better than 50 ps. The data transmission throughput can reach 400 Mbps for one FEE board and 180 Mbps for 4 FEE boards sharing one up link port in WR switch, which is better than the requirement of the LHAASO WCDA.

---
Source: https://tomesphere.com/paper/1907.02968