A potential space- and power-effective muon sensor module for imaging a volcano

Hideaki Taira,Hiroyuki K M Tanaka

doi:10.5047/eps.2009.06.005

Abstract

The application of muon radiography will be greatly enhanced by the use of two muon sensor modules that save electric power consumption and are easily transportable. Muon sensor modules used for a volcano observation must have a low electric power consumption requirement and be both waterproof and portable. In this article, we discuss two candidate sensor modules: (1) a portable muon sensor module with wavelength-shifting (WLS) fibers and a multi-anode photomultiplier tube (MAPMT), and (2) a regular scintillator telescope with PMT complemented by a low-power Cockcroft-Walton circuit (CWPMT). A realistic telescope system consisting of a muon sensor module with MAPMT has been tested and found to consume 76 W, most of which (72 W) is used by the redundant electronic circuit required for pulse shaping; this could be modified to drastically improve the power consumption. In comparison, a muon telescope system with a CWPMT was found to consume 7.57 W. We also calculated the muon stopping length in SiO2 by means of a Monte-Carlo simulation. This calculation provided the average density structure along the muon path in rock, where the muon path length was shorter than 1.5 km, with an accuracy of about 5% during a 90-day measurement period by assuming a 1-m2 muon detector with an angular resolution of 25 mrad.

Highlights

For a number of years, researchers have been attempting to image volcanoes (e.g., Tanaka et al, 2003, 2005, 2007a, b, 2008; Tanaka and Yokoyama, 2008), pyramids (e.g., King et al, 1999), and contrabands (e.g., Borozdin et al, 2003) radiographically using cosmic-ray muons
A realistic telescope system consisting of a muon sensor module with multi-anode photomultiplier tube (MAPMT) has been tested and found to consume 76 W, most of which (72 W) is used by the redundant electronic circuit required for pulse shaping; this could be modified to drastically improve the power consumption
(4) We confirmed that the total power consumption of the muon sensor system with the MAPMT was 76 W, with the discriminator consuming 72 W of electrical power

Summary

Introduction

For a number of years, researchers have been attempting to image volcanoes (e.g., Tanaka et al, 2003, 2005, 2007a, b, 2008; Tanaka and Yokoyama, 2008), pyramids (e.g., King et al, 1999), and contrabands (e.g., Borozdin et al, 2003) radiographically using cosmic-ray muons. To interpret the dynamics of the volcanic explosion, it is necessary to be able to interpret the variation in the interior density structure of volcanoes over time For this purpose, we have proposed a new muon sensor system which is lightweight and requires less electrical power. Since this method uses the signal height of the PMT as the trigger for timing, the position is influenced by the surrounding temperature changes at the volcano site For these reasons, we developed a module utilizing a crossaligned plastic scintillator array, i.e. the third candidate detector system. (1) We observed the analog output signal of each channel of MAPMT and that of CWPMT with the oscilloscope, measured the distribution of pulse height, and optimized the discrimination level.

Findings

Discussion

Conclusion