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Journal Articles

Spectroscopic measurements of L X-rays with a TES microcalorimeter for a non-destructive assay of transuranium elements

Nakamura, Keisuke; Morishita, Yuki; Takasaki, Koji; Maehata, Keisuke*; Sugimoto, Tetsuya*; Kiguchi, Yu*; Iyomoto, Naoko*; Mitsuda, Kazuhisa*

Journal of Low Temperature Physics, 193(3-4), p.314 - 320, 2018/11

 Percentile:100(Physics, Applied)

Journal Articles

Recovery of radiation degradation on inverted metamorphic triple-junction solar cells by light soaking

Shibata, Yuichi*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi; Ooka, Sachiyo*; Takamoto, Tatsuya*

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.65 - 68, 2015/11

Radiation response is one of the important properties for space solar cells. It should be well understood so as to accurately predict their degradation in orbit and also to improve their radiation tolerance. Recently, a phenomenon, recovery from the radiation degradation by light soaking, on inverted metamorphic (IMM) triple-junction (3J) solar cells was found out. In this work, the light soaking annealing effects on electron irradiated IMM 3J solar cells are reported. IMM 3J solar cells irradiated with 1 MeV electrons with the fluence of 3$$times$$10$$^{15}$$ e$$^-$$/cm$$^2$$ showed the recovery of open-circuit voltage, Voc, up to 43 mV after light (AM0, 1 sun) soaking of 3 hours. The increment of the electroluminescence intensity for InGaP in the IMM 3J cells due to the light soaking suggests that the Voc recovery occurs in InGaP top-cell rather than GaAs middle-cell or InGaAs bottom-cell.

Journal Articles

Measurement of ion beam induced current in quantum dot solar cells

Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Sugaya, Takeyoshi*; Mochizuki, Toru*; Okano, Yoshinobu*; Oshima, Takeshi

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.73 - 76, 2015/11

The radiation effect on GaAs p-i-n solar cells with quantum dot (QD) in the i-layer was investigated. In a previous work, we particularly noted the degradation of fill-factor (FF) for the QD cells. In this work, to clarify the reason of the FF degradation in QD cells, generation current due to low-energy proton irradiation, which we call ion beam induced current (IBIC), was observed to characterize behavior of the generated minority carrier by the protons in the depletion region where QDs are located. The energy of protons was adjusted to damage the depletion region, and decrease of generation current was measured during the proton irradiation. The results suggest that the serious degradation of FF is caused by a decrease of the carrier collection efficiency in the depletion region due to proton damage.

Journal Articles

Development and application test of radiation detector for the UARMS

Sanada, Yukihisa; Yamada, Tsutomu; Ishibashi, Satoshi; Torii, Tatsuo

Dai-57-Kai Jido Seigyo Rengo Koenkai Koen Rombunshu (USB Flash Drive), p.695 - 698, 2014/11

The Great East Japan Earthquake that occurred on March 11, 2011, generated a series of large tsunami waves that caused serious damage to the Fukushima Daiichi Nuclear Power Plant, following which a large amount of radioactive material was discharged from the nuclear power plant into the environment. In JAEA and JAXA, UARMS (Unmanned Airplane Radiation Monitoring System) was developing as collaborative research. Here, we report about an aerial radiation monitoring technology for UARMS.

Journal Articles

Investigation of single-event damages on silicon carbide (SiC) power MOSFETs

Mizuta, Eiichi*; Kuboyama, Satoshi*; Abe, Hiroshi; Iwata, Yoshiyuki*; Tamura, Takashi*

IEEE Transactions on Nuclear Science, 61(4), p.1924 - 1928, 2014/08

 Times Cited Count:23 Percentile:3.93(Engineering, Electrical & Electronic)

Journal Articles

First flight demonstration of glass-type space solar sheet

Shimazaki, Kazunori*; Kobayashi, Yuki*; Takahashi, Masato*; Imaizumi, Mitsuru*; Murashima, Mio*; Takahashi, Yu*; Toyota, Hiroyuki*; Kukita, Akio*; Oshima, Takeshi; Sato, Shinichiro; et al.

Proceedings of 40th IEEE Photovoltaic Specialists Conference (PVSC-40) (CD-ROM), p.2149 - 2154, 2014/06

The electrical performance of a glass-type space solar sheet (G-SSS) was demonstrated in space. G-SSS comprises InGaP/GaAs dual-junction and InGaP/GaAs/InGaAs triplejunction solar cells. It is lightweight solar generation sheet, less than 0.5 mm thick. It is mounted on the "HISAKI" (SPRINT-A) small scientific satellite, which was launched on September 14, 2013. The initial flight data were successfully acquired and this flight demonstration was a world-first experiment for G-SSS using III-V multi-junction thin-film solar cells. The cells demonstrated superior performance and the electrical outputs matched the flight prediction.

Journal Articles

A Conference report on the 2013 IEEE NSS/MIC/RTSD

Nagao, Yuto

Hoeikyo Nyusu, (78), p.14 - 15, 2014/01

no abstracts in English

Journal Articles

Quantum-well solar cells for space; The Impact of carrier removal on end-of-life device performance

Hoheisel, R.*; Gonz$'a$lez, M.*; Lumb, M.*; Scheiman, D.*; Messenger, S. R.*; Bailey, C. G.*; Lorentzen, J.*; Tibbits, T. N. D.*; Imaizumi, Mitsuru*; Oshima, Takeshi; et al.

IEEE Journal of Photovoltaics, 4(1), p.253 - 259, 2014/01

 Times Cited Count:8 Percentile:53.77(Energy & Fuels)

Analysis on the radiation response of solar cells with multi quantum wells (MQW) included in the quasi-intrinsic region between the emitter and the base layer is presented. We found that in the case of MQW devices, carrier removal (CR) effects are also observed. Experimental measurements and numerical simulations reveal that with increasing radiation dose, CR can cause the initially quasi-intrinsic background doping of the MQW region to become specifically n- or p-type. This can result in a significant narrowing and even the collapse of the electric field between the emitter and the base where the MQWs are located. The implications of the CR-induced modification of the electric field on the current-voltage characteristics and on the collection efficiency of carriers generated within the emitter, the MQW region, and the base are discussed for different radiation dose conditions. This paper concludes with a discussion of improved radiation hard MQW device designs.

Journal Articles

Temperature influence on performance degradation of hydrogenated amorphous silicon solar cells irradiated with protons

Sato, Shinichiro; Sai, Hitoshi*; Oshima, Takeshi; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Kondo, Michio*

Progress in Photovoltaics; Research and Applications, 21(7), p.1499 - 1506, 2013/11

 Times Cited Count:4 Percentile:73.07(Energy & Fuels)

Proton degradation behaviors of hydrogenated amorphous silicon (a-Si:H) solar cells irradiated with protons at 331 K are compared with that at 298 K (room temperature). Variations with time in the post-irradiation electrical properties are also investigated. It is found that the radiation degradation of the electrical properties at 331 K is significantly smaller than that at room temperature. Also, all the electrical properties (short-circuit current, open-circuit voltage, output maximum, and fill factor) recover with time after irradiation even at room temperature. The characteristic time of thermal annealing of short-circuit current is larger as the temperature is higher. These results indicate that temperature during irradiation and elapsed time from irradiation to measurement is an important parameter for radiation degradation of a-Si:H solar cells. Therefore, these parameters should be controlled in conducting the ground radiation tests.

Journal Articles

Comparative study on degradation characteristics of component subcells in IMM triple-junction solar cells irradiated with high-energy electrons and protons

Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Tajima, Michio*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.3243 - 3248, 2013/06

Radiation response of InGaP, GaAs, InGaAs (In=20%) and InGaAs (In=30%) single-junction solar cells, which are the component sbcells of IMM3J cells, were comparatively studied. High-energy electrons (1 MeV) and protons (10 MeV) were irradiated to the four types of the cells. The InGaP cell has the highest radiation resistance to both electrons and protons amongst the four cells as expected. On the other hand, the InGaAs cells have less resistant for Isc compared to InGaP and GaAs cells. However, the resistance of Voc of InGaAs cells is comparable to that of the other two cells. As a general result, InGaAs cells have less radiation resistance to electrons, while they have the resistance against protons equivalent to GaAs cell. These radiation response properties of InGaAs cells are thought to be useful to design radiation resistant IMM3J space solar cells.

Journal Articles

Estimation of subcell photocurrent in IMM3J using LED bias light

Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.0696 - 0700, 2013/06

The estimation method of subcell photocurrent (I$$_{photo}$$) in multi-junction solar cells using not external quantum efficiency (EQE) but light current-voltage (LIV) characteristics after irradiation is proposed. To obtain I$$_{photo}$$ of each subcell, it is necessary to estimate the reverse saturation current density (J$$_0$$) and shunt resistance (R$$_{sh}$$) of each subcell using EL and LED bias light (LBL) method. Since estimated I$$_{photo}$$ is in agreement with experimental LIV characteristics under illumination of AM0 solar simulator, we can evaluate of complicated maximum power (Pmax) of the inverted metamorphic triple-junction (IMM3J) solar cell after irradiation.

Journal Articles

A Study on the artifact external quantum efficiency of Ge bottom subcells in triple-junction solar cells

Sugai, Mitsunobu*; Harada, Jiro*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.0715 - 0720, 2013/06

no abstracts in English

Journal Articles

Radiation study in quantum well III-V multi-junction solar cells

Gonz$'a$lez, M.*; Hoheisel, R.*; Lumb, M.*; Scheiman, D.*; Bailey, C. G.*; Lorentzen, J.*; Maximenko, S.*; Messenger, S. R.*; Jenkins, P. P.*; Tibbits, T. N. D.*; et al.

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.3233 - 3236, 2013/06

The radiation response of multi quantum wall (MQW) triple junction and component cells was analyzed. Initial results show that for 1MeV electron irradiation the middle MQW cell governs the degradation of the triple junction. This is attributed the specific middle cell design, in particular the thick 0.98 $$mu$$m depletion region, and alternative, more radiation hard, designs are presented. Additionally, characterization studies, including dark IV, external quantum efficiency, electroluminescence, as well as defect characterization were investigated.

Journal Articles

Radiation effects in solar cells

Imaizumi, Mitsuru*; Oshima, Takeshi

Proceedings of SPIE, Vol.8725 (CD-ROM), 8 Pages, 2013/06

 Times Cited Count:2 Percentile:16.27

Radiation effects in solar cells are described. Degradation behavior of space solar cells, such as silicon solar cells and InGaP/GaAs/Ge triple-junction solar cells, due to high-energy electrons and protons are elaborated in the presentation. Space solar cell design technology is also explained. In addition, technologies for practical application of solar cells in space including methodology for radiation protection and degradation prediction are interpreted. Furthermore, recent development status of state-of-the-art space solar cells is introduced.

Journal Articles

Three-dimensional and multienergy $$gamma$$-ray simultaneous imaging by using a Si/CdTe Compton camera

Suzuki, Yoshiyuki*; Yamaguchi, Mitsutaka; Odaka, Hirokazu*; Shimada, Hirofumi*; Yoshida, Yukari*; Torikai, Kota*; Sato, Takahiro; Arakawa, Kazuo*; Kawachi, Naoki; Watanabe, Shigeki; et al.

Radiology, 267(3), p.941 - 947, 2013/06

 Times Cited Count:5 Percentile:68.09(Radiology, Nuclear Medicine & Medical Imaging)

Journal Articles

Applicability of redundant pairs of SOI transistors for analog circuits and their applications to phase-locked loop circuits

Makihara, Akiko*; Yokose, Tamotsu*; Tsuchiya, Yoshihisa*; Miyazaki, Yoshio*; Abe, Hiroshi; Shindo, Hiroyuki*; Ebihara, Tsukasa*; Maru, Akifumi*; Morikawa, Koichi*; Kuboyama, Satoshi*; et al.

IEEE Transactions on Nuclear Science, 60(1), p.230 - 235, 2013/02

 Times Cited Count:2 Percentile:72.96(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Change in the electrical performance of GaAs solar cells with InGaAs quantum dot layers by electron irradiation

Oshima, Takeshi; Sato, Shinichiro; Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*

Solar Energy Materials and Solar Cells, 108, p.263 - 268, 2013/01

 Times Cited Count:11 Percentile:44.92(Energy & Fuels)

GaAs solar cells which have a PiN structure with 50 self-organized In$$_{0.4}$$Ga$$_{0.6}$$As Quantum Dot (QD) layers were irradiated with 1 MeV electrons up to 1$$times$$10$$^{16}$$ /cm$$^{2}$$. After irradiation at 1$$times$$10$$^{16}$$/cm$$^{2}$$, the remaining factor of I$$_{rm SC}$$, V$$_{rm OC}$$ and P$$_{rm MAX}$$ for the InGaAs 50 QD solar cell becomes 80, 90 and 55% of the initial values, respectively. On the other hand, those values for non QD GaAs solar cells decrease to 95, 80 and 63% of the initial values, respectively. Since the i-layer for the 50 QD solar cells (1.1 $$mu$$m) is thicker than the non QD solar cells (660 nm), the larger degradation of I$$_{rm SC}$$ for the 50 QD solar cells than the non QD ones can be interpreted in terms that the carrier recombination in the i-layer for the 50 QD solar cells is larger than that for the non QD solar cells. For V$$_{rm OC}$$, the 50 QD solar cells showes better radiation resistance than the non QD solar cells. Furthermore, the annealing behavior of the electrical characteristics for the 50 QD and the non QD solar cells was investigated at RT under AM 0 immediately after the irradiation. As a result, the recovery of the electrical characteristics for both solar cells was observed, and the GaAs solar cells shows relatively larger recovery compared to the 50 QD solar cells. Although the mechanism of this recovery has not yet been clarified, the origin of this recovery is thought not to come from the existence of QDs because the GaAs solar cell without QD layers also shows the recovery.

Journal Articles

An Evaluation of three-dimensional imaging by use of Si/CdTe Compton cameras

Yamaguchi, Mitsutaka; Nagao, Yuto; Kawachi, Naoki; Fujimaki, Shu; Kamiya, Tomihiro; Odaka, Hirokazu*; Kokubun, Motohide*; Takeda, Shinichiro*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 3 Pages, 2013/00

Journal Articles

A New method for monitoring beam range by measuring low energy photons

Yamaguchi, Mitsutaka; Torikai, Kota*; Kawachi, Naoki; Shimada, Hirofumi*; Sato, Takahiro; Nagao, Yuto; Fujimaki, Shu; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2 Pages, 2013/00

Journal Articles

High-resolution Compton cameras based on Si/CdTe double-sided strip detectors

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:15 Percentile:14.63(Instruments & Instrumentation)

We have developed a new Si/CdTe semiconductor double-sided strip detector (DSD) Compton camera. The camera consists of a 500-$$mu$$m-thick Si-DSD and four layers of 750-$$mu$$m-thick CdTe-DSDs all of which have common electrode configuration segmented into 128 strips on each side with pitches of 250$$mu$$m. 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.

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