Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

Keisuke Iwano, Kohei Yamanoi, Yuki Iwasa, Kazuyuki Mori, Yuki Minami, Ren Arita, Takuma Yamanaka, Kazuhito Fukuda, Melvin John F. Empizo, Keisuke Takano, Toshihiko Shimizu, Makoto Nakajima, Masashi Yoshimura, Nobuhiko Sarukura, Takayoshi Norimatsu, Masanori Hangyo, Hiroshi Azechi, Bess G. Singidas, Roland V. Sarmago, Makoto Oya & 1 others Yoshio Ueda

Research output: Contribution to journalArticle

Abstract

We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

Original languageEnglish
Article number105108
JournalAIP Advances
Volume6
Issue number10
DOIs
Publication statusPublished - Oct 1 2016

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infrared windows
fusion reactors
transmittance
sapphire
ion irradiation
helium ions
vacuum
crystals
ions
color centers
crystal surfaces
annealing
optical absorption
power reactors
hydrogen isotopes
causes
polishing
crystal lattices
wavelengths
deuterium

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors. / Iwano, Keisuke; Yamanoi, Kohei; Iwasa, Yuki; Mori, Kazuyuki; Minami, Yuki; Arita, Ren; Yamanaka, Takuma; Fukuda, Kazuhito; Empizo, Melvin John F.; Takano, Keisuke; Shimizu, Toshihiko; Nakajima, Makoto; Yoshimura, Masashi; Sarukura, Nobuhiko; Norimatsu, Takayoshi; Hangyo, Masanori; Azechi, Hiroshi; Singidas, Bess G.; Sarmago, Roland V.; Oya, Makoto; Ueda, Yoshio.

In: AIP Advances, Vol. 6, No. 10, 105108, 01.10.2016.

Research output: Contribution to journalArticle

Iwano, K, Yamanoi, K, Iwasa, Y, Mori, K, Minami, Y, Arita, R, Yamanaka, T, Fukuda, K, Empizo, MJF, Takano, K, Shimizu, T, Nakajima, M, Yoshimura, M, Sarukura, N, Norimatsu, T, Hangyo, M, Azechi, H, Singidas, BG, Sarmago, RV, Oya, M & Ueda, Y 2016, 'Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors', AIP Advances, vol. 6, no. 10, 105108. https://doi.org/10.1063/1.4965927
Iwano, Keisuke ; Yamanoi, Kohei ; Iwasa, Yuki ; Mori, Kazuyuki ; Minami, Yuki ; Arita, Ren ; Yamanaka, Takuma ; Fukuda, Kazuhito ; Empizo, Melvin John F. ; Takano, Keisuke ; Shimizu, Toshihiko ; Nakajima, Makoto ; Yoshimura, Masashi ; Sarukura, Nobuhiko ; Norimatsu, Takayoshi ; Hangyo, Masanori ; Azechi, Hiroshi ; Singidas, Bess G. ; Sarmago, Roland V. ; Oya, Makoto ; Ueda, Yoshio. / Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors. In: AIP Advances. 2016 ; Vol. 6, No. 10.
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AU - Iwano, Keisuke

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AU - Mori, Kazuyuki

AU - Minami, Yuki

AU - Arita, Ren

AU - Yamanaka, Takuma

AU - Fukuda, Kazuhito

AU - Empizo, Melvin John F.

AU - Takano, Keisuke

AU - Shimizu, Toshihiko

AU - Nakajima, Makoto

AU - Yoshimura, Masashi

AU - Sarukura, Nobuhiko

AU - Norimatsu, Takayoshi

AU - Hangyo, Masanori

AU - Azechi, Hiroshi

AU - Singidas, Bess G.

AU - Sarmago, Roland V.

AU - Oya, Makoto

AU - Ueda, Yoshio

PY - 2016/10/1

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N2 - We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

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