Shunichiro Makino

Large-scale hybrid monitoring system for temperature, strain, and vibration using fiber Bragg grating sensors

Fiber Bragg grating (FBG) sensor systems have been widely developed and the feasibility of their application to various fields has been demonstrated. However, from the viewpoint of the combination of highly multiplexed system and hybrid sensing of static parameter and dynamic parameter, investigations are not adequate yet. In this paper an interrogation technique for static and dynamic FBG sensors is developed. We demonstrated that the method could measure the temperature within 1?<C and detect a frequency signal up to 300Hz. We designed a multiplexing method and evaluated that the multiplexed FBG sensor system was able to monitor a maximum of 192 FBG sensors. As a result, we confirmed the applicability of the system for large-scale monitoring of temperature, strain and vibration.

Development of Semiconductor Gamma-Camera System with CdZnTe Detectors

A CdZnTe semiconductor detector, which works at room temperature, may realize a next generation gamma-camera system due to its high spatial resolution and high energy resolution. We made a prototype gamma-camera system with CdZnTe detectors to evaluate the feasibility of the semiconductor gamma-camera. This paper described our prototype system and some results obtained with this system.

Long Scintillation Detector Using Composite Light Guide for β-ray Survey Measurement

In this paper, we describe a new type of scintillation detector that can be inserted into long, narrow tubes used in nuclear power plants to measure radioactive contamination of their inner surfaces. The sensitive area of the detector needs to cover the entire circumference and extend along the longitudinal axis, and its performance must be equivalent to that of a conventional survey meter. To construct such a sensitive area, we bonded six long, thin plastic scintillator strips around a hexagonal center core. For the hexagonal center core, we proposed a novel light collection structure called a “composite light guide,” using a wavelength-shifting technique to maintain the counting efficiency while achieving better uniformity along the longitudinal axis. We conducted basic experiments, and also established a simple light propagation model of the composite light guide, focusing on the light intensity, and confirmed its effectiveness. Using this light propagation model, we determined the optimum design and incorporated it into the manufacture of a prototype detector. From tests of the prototype detector, we verified that its performance satisfied the design requirements and that the composite light guide functioned effectively.

Development of high-counting-rate measurement system for 3 He position sensitive detector

We developed a high-counting-rate PSD system whose maximum counting rate is about four times higher than conventional PSD systems. By considering the RMS noise characteristics of the PSD, the shaping time was reduced to 0.1 μs, one fourth the time of conventional systems. In a PSD system, the trailing edge of the shaped pulse overshoots or undershoots depending on the neutron incident position, resulting in degradation of the position resolution at higher counting rates. The circuit constants were therefore optimized to keep the trailing edge constant. Moreover, the baseline fluctuation due to the ion current was eliminated by data processing. We evaluated the performance using PSDs of 6 to 25.4 mm diameter whose rise time was shortened with additive gas. Position resolution of 3.5 mm FWHM was obtained using a PSD with 12.7 mm diameter and 60 cm effective length at the value 1850V and 0.1 μs shaping time. For PSDs with diameters of 12.7 mm or less, better position resolution was obtained with 0.1 μs shaping time, and for PSDs with diameters exceeding 12.7 mm, better position resolution was obtained when the shaping time was larger than 0.1 μs. For a 0.1 μs shaping time, the position resolution obtained at 100 kcps was the same as that obtained at a low counting rate.