Attenuation study for Tibet Water Cherenkov Muon Detector Array-A

TL;DR

This study develops and validates a quick, online method using terminal reflection to measure signal attenuation in Tibet MD-A's long cables, ensuring accurate calibration for muon detection.

Contribution

It introduces a practical terminal reflection technique for online calibration of cable attenuation in Tibet MD-A, validated against traditional QDC methods.

Findings

Attenuation coefficient with 250-m cable is ~13.9% at 26°C.

Terminal reflection method is fast, convenient, and suitable for online calibration.

Cable frequency response measured for studying signal time dispersion.

Abstract

This work aims at online calibrating the signal attenuation of the long cable used in Tibet Water Cherenkov Muon detector array-A (Tibet MD-A) under the 37 000 m2 Tibet air shower array. Based on the waterproof connection of the PMT (R3600_06) with the signal cable, and the characters of the high voltage divider, terminal reflection method is explored and used for measuring the signal attenuation with a practical way to eliminate the contribution of the pulse baseline (pedestal). Comparison measurement between it and QDC (Charge-to-Digital Conversion) data taking method are carried out by using open-ended cables, confirming that terminal reflection method is a fast and convenient method, and suitable to online calibrate the signal attenuation for Tibet MD-A. At 26\degree C, the measured attenuation coefficient with the 250-m cable, permanently connected to the PMT, is ~13.9%. Also, the cable frequency response is measured by using the sinusoidal signals, which could be used to study the time dispersion of the real signal produced with Tibet MD-A detector via Fourier analysis.