Abstract
Abstract
Water Cherenov detector is a vital part in most of neutrino
or cosmic ray research. As detectors grow in size, the water
attenuation length (WAL) becomes increasingly essential for detector
performance. It is essential to measure or monitor the WAL. There
are two ways to measure WAL, one is to take a water sample from the
detector and measure it in the WAL measurement device, and the other
is to put the device directly into the water Cherenkov detector. For
the device in the water, the Super-Kamiokande experiment achieved
WAL measurement capability near 100 meters with a moving light
source up and down. A novel system has been proposed to address the
challenge of investigating long WAL. This system focuses on ample
water Cherenkov detectors and features a fixed light source and
photomultiplier tubes (PMTs) at varying distances, eliminating the
need for moving parts. Each component, including LED, diffuse ball,
PMTs, and fibers, is introduced to explain uncertainty
control. Based on lab tests, the measurement uncertainty of each PMT
channel has been controlled within 5%. Additionally, camera
technology is also used during the evaluation of the system
uncertainty, which has the potential to replace PMTs in the future
for this measurement. Monte Carlo simulations have shown that the
system can achieve a 5% uncertainty at WAL of 80 meters and 8% at
WAL of 100 meters. This system can be used in experiments with large
Cherenkov detectors such as JUNO-water veto and Hyper-K.