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Journal Articles

Fabrication of hard-coated optical absorbers with microstructured surfaces using etched ion tracks; Toward broadband ultra-low reflectance

Amemiya, Kuniaki*; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Shitomi, Hiroshi*; Numata, Takayuki*; Kinoshita, Kenichi*; Tanabe, Minoru*; Fukuda, Daiji*

Nuclear Instruments and Methods in Physics Research B, 356-357, p.154 - 159, 2015/08

 Times Cited Count:9 Percentile:64.82(Instruments & Instrumentation)

Broadband low reflectance materials have various applications in the field of optical energy management; however, materials with ultra-low reflectance (below 0.1%) have been considered as mechanically delicate. We have developed a novel hard-surface optical absorber with microstructured, diamond-like carbon coated ion tracks on CR-39 plastic substrate. The spectral reflectance of the first prototype was below 2% for wavelengths ranging from 400 nm to 1400 nm; moreover, the optical absorber had mechanically hard surface and exhibited temporal durability. Choosing the appropriate design of the surface structure and coating layer is likely to reduce the reflectance to the order of 0.1%. This technique yields easy-to-handle broadband ultra-low reflectance absorbers.

JAEA Reports

Study of an instrumentation system for a nuclear reactor plant based on optical fiber Bragg gratings

Amemiya, Kuniaki*; Nakazawa, Masaharu*; Ariyoshi, Masahiko; Ito, Keisuke

JNC TY9400 2004-008, 52 Pages, 2004/04

JNC-TY9400-2004-008.pdf:2.65MB

A new monitoring system of nuclear reactor plants by means of optical fiber Bragg gratings (FBGs) was developed which have sensitivity in temperature, distortion and vibration. The reflective wavelength of FBGs was not influenced by gamma-ray irradiation up to 1.4MGy and by exposure to fast neutrons in excess of 10 sup14 n/cm sup2. A temperature-insensitive vibration sensing system was constructed and operated with no trouble in gamma-ray environments up to 100kGy. Furthermore, a multiple point vibration sensing system was designed and constructed. The system was successfully demonstrated on a cooling system at the "Yayoi" reactor. Thus, we tried to apply the monitoring system to a primary loop area of JOYO to confirm the applicability of FBG sensors for the commercial power reactors. Although a correlation of sodium flow in side pipes and vibration measured by FBG sensors was found before starting of the reactor, it became impossible after starting operation of the reactor because of a decline of signal amplitude. Investigating the reason, it was mainly caused by significant transmission losses at the splicing point and there were no problems with FBG sensors. Various methods, for example, using a more powerful light source and changing the splicing method, may be used to improve it in the future.

Oral presentation

Toward user-friendly thermal radiometers; Microfabrication of novel photo-thermal sensors and broadband ultra-black absorbers

Amemiya, Kuniaki*; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Shitomi, Hiroshi*; Kinoshita, Kenichi*; Numata, Takayuki*; Tanabe, Minoru*; Fukuda, Daiji*

no journal, , 

A thermal radiometer absorbs all incoming photons and has a high sensitivity to detect the resulting temperature rise. The big challenges here were insufficient mechanical stability of broadband ultra-black absorbers and low sensitivity of photo-thermal sensors. We developed a robust optical absorber and low-noise photo-thermal sensor by new microfabrication techniques. The optical absorbers had micrometer-sized surface structures of chemically-etched ion tracks on CR-39 plastic and hard carbon coating as an optical absorption layer, therefore, exhibiting a spectral reflectance suppressed to below 1% in the ultra-violet to near infrared range of wavelengths. Importantly, they were never made susceptible to dust blow off as well as to mechanical contact. The photo-thermal detectors were equipped with the bimetal MEMS system, which can sensitively respond to thermally-induced deformation. They were found sensitive enough to reach almost the theoretical limit.

Oral presentation

Design and fabrication of novel broadband near-perfect black absorber having microstructured surface

Amemiya, Kuniaki*; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Shitomi, Hiroshi*; Kinoshita, Kenichi*; Numata, Takayuki*; Tanabe, Minoru*; Fukuda, Daiji*

no journal, , 

The novel broadband near-perfect black absorber for an absolute radiometer has been developed. Microstructured surface having high-aspect-ratio conical pores was fabricated by swift heavy ion beam irradiation and following etching process; subsequently, the surface was coated with black layer. Incident light which enters into the surface microstructure experiences multiple reflections which enhance optical absorption; therefore, the net reflectance decreases much less than 1% with sufficient pit aspect ratio and absorption layer thickness, which can be designed by finite differential time domain (FDTD) method calculation. Furthermore, a prototype of the novel black absorber also exhibited good mechanical durability. This newly developed black material is also expected to have potential application in various fields of optical energy management such as stray light elimination.

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