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Odaka, Hirokazu*; Ichinohe, Yuto*; Takeda, Shinichiro*; Fukuyama, Taro*; Hagino, Koichi*; Saito, Shinya*; Sato, Tamotsu*; Sato, Goro*; Watanabe, Shin*; Kokubun, Motohide*; et al.
Nuclear Instruments and Methods in Physics Research A, 695, p.179 - 183, 2012/12
Times Cited Count：23 Percentile：84.01(Instruments & Instrumentation)We have developed a new Si/CdTe semiconductor double-sided strip detector (DSD) Compton camera. The camera consists of a 500-
m-thick Si-DSD and four layers of 750-m-thick CdTe-DSDs all of which have common electrode configuration segmented into 128 strips on each side with pitches of 250m. In order to realize high angular resolution and to reduce size of the detector system, a stack of DSDs with short stack pitches of 4 mm is utilized to make the camera. Taking advantage of the excellent energy and position resolutions of the semiconductor devices, the camera achieves high angular resolutions of 4.5 degrees at 356 keV and 3.5 degrees at 662 keV. To obtain such high resolutions together with an acceptable detection efficiency, we demonstrate data reduction methods including energy calibration using Compton scattering continuum and depth sensing in the CdTe-DSD. We also discuss imaging capability of the camera and show simultaneous multi-energy imaging.
-ray cameraTakeda, Shinichiro*; Ichinohe, Yuto*; Hagino, Koichi*; Odaka, Hirokazu*; Yuasa, Takayuki*; Ishikawa, Shinnosuke*; Fukuyama, Taro*; Saito, Shinya*; Sato, Tamotsu*; Sato, Goro*; et al.
Physics Procedia, 37, p.859 - 866, 2012/10
Times Cited Count：22 Percentile：98.43(Physics, Applied)By using new Compton camera consisting of silicon double-sided strip detector (Si-DSD) and CdTe-DSD developed for the ASTRO-H mission, an experiment was conducted to study its feasibility for advanced hotspot monitoring. In addition to hotspot imaging already provided by commercial imaging systems, the identification of the variety of radioisotopes is realized thanks to the good energy resolution given by the semiconductor detectors. Three radioisotopes of 
Ba (356 keV), 
Na (511 keV) and 
Cs (662 keV) were individually imaged by applying event selection in the energy window and the -ray images was correctly overlapped by an optical picture. The detection efficiency of 1.68
10
(effective area: 1.710 cm
) and angular resolution of 3.8
were obtained by stacking five detector modules for 662 keV -ray. The higher detection efficiency required in a specific use can be achieved by stacking more detector modules.
Shimoyama, Iwao; Li, X.*; Shimada, Takashi*
no journal, ,
Alignment of single-walled carbon nanotubes (SWNTs) is significantly important for many applications of SWNTs. Recently, it was reported that SWNTs grown by chemical vapor deposition (CVD) align along step arrays or one-dimensional atomic arrangements on some single crystal surfaces. This method is interesting to achieve large-scale alignment of SWNTs, however, the detail of the alignment mechanism has not been clarified, yet. In order to investigate the alignment mechanism, we utilized polarization dependent Raman spectroscopy for SWNTs grown on quartz single crystal surfaces by CVD. G-band of our sample showed high-frequency G
-band and low-frequency G
-band. Though both bands exhibited qualitatively same polarization dependence, the magnitude of polarization dependence of G-band was larger than that of G-band. Spectral change for different polarization configurations clarified that vibration modes were not main reason of our result. Comparing Stokes and anti-Stokes spectra, results obtained from samples with different growth conditions, and spectra measured by different resonant excitation conditions, we concluded that different magnitude of polarization dependence between G-band and G-band originated from different orientations between semiconducting SWNTs and metallic SWNTs. This result indicates selective alignment of semiconducting SWNTs on quartz single crystal surfaces.
Shimoyama, Iwao; Li, X.*; Shimada, Takashi*
no journal, ,
It has been reported that single-walled carbon-nanotubes (SWNTs) align on several single crystal surfaces with chemical vapor deposition. In order to investigate the alignment mechanism, we measured polarization-dependent Raman spectra of aligned SWNTs formed on quartz single crystal surfaces. High- and low-frequency components in tangential vibration modes of Raman spectra, i.e., G (
1590cm
) and G bands (
1575cm), exhibited different magnitudes of polarization dependence. High-frequency G band always showed larger polarization dependence than low-frequency G band independently of polarization configuration, resonant excitation condition, and growth condition. Base on these results, we concluded that different polarization dependences between G and G bands originated from different orientations of semiconducting and metallic SWNTs. This suggests that semiconducting SWNTs selectively align on quartz crystal surfaces.
