Control measurement method of range switch for dual GM counter tubes

Abstract

BackgroundEffective measurement using dual Geiger-Müller (GM) counter tubes hinges on the range switch control technology. This technology facilitates the selection of the appropriate counter tube for measurement. Nonetheless, the performance disparities between the two types of GM counter tubes imply that the conventional method of bifurcating the measurement range into two sections results in reduced linearity for the overlapping measurement ranges.PurposeThis study aims to propose a new control method for range switching to enhance the linearity of the overlapping ranges in the measurement using dual GM counter tubes.MethodsA dual GM counter detector was consisted of a low range GM counter tube with measurement range of 0.1 μ Sv· h-1~10 mSv·h-1, and a high range GM counter tube with measurement range of 1 mSv·h-1~100 Sv·h-1. The measurement range of 0.1 μSv·h-1~100 Sv·h-1 was segmented into three categories: low, medium, and high. Rapid and automatic transitions between these three ranges were facilitated by high-voltage control circuit, measurement range control circuit and dead time regulation circuit. During the medium range of 1~10 mSv·h-1 measurement, two range switching threshold points were set within the overlapping area, and data from the two GM counters were weighting processed respectively in the single-chip processor, hence appropriate weighting factors that maximize the linear fit of the measurement results of the dual GM counter were obtained. Finally, the 241Am source and 60Co ource were employed to test the dual GM counter detector circuits.ResultsPreliminary test results indicate that the proposed dual GM counter detector facilitates fast automatic transitions among the three measurement ranges, and the linear fit of the counter tube in the overlapping area from 1 000 μGy·h-1 to 10 000 μGy·h-1 is enhanced, making the linear fit of the dual GM counter reach up to 0.999 1 within the measurement range of 251~25 130 μGy·h-1.ConclusionsThe overall measurement linearity of the dual GM counter is effectively improved by proposed control method of this study for range switching.

Keywords

• dual geiger miller counter tubes
• range switch
• overlapping region