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Micro-fluoresence spectroscopy and ESR study on ion beam irradiated glass
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 245 (2006) 201–203 www.elsevier.com/locate/nimb
Micro-fluoresence spectroscopy and ESR study on ion beam irradiated glass H. Kudo *, T. Akagawa, Y. Katsumura Nuclear Engineering Research Laboratory, School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188, Japan Available online 27 December 2005
Abstract Radiation effects on SiO2 glasses are well studied but not fully understood especially towards ion beam irradiation. In this work, SiO2 glasses, with an OH content of 400–1000 ppm and a thickness of 0.1 and 1 mm, were irradiated with proton beams of 1 MeV or 2.5 MeV to fluences of 1 · 1015 or 1 · 1016 cm 2, at a Van de Graaff or a Tandetron accelerator at room temperature under vacuum. The range and stopping power of the ions in SiO2 glass are 14 lm and 0.17 MeVcm2/g for 1 MeV proton and 66 lm and 0.29 MeVcm2/g for 2.5 MeV proton, respectively, according to the SRIM (stopping and ranges of ion in matter) code. The materials were subjected to micro-fluorescence spectroscopy and electron spin resonance (ESR) measurements. The micro-fluorescence spectroscopy uses excitation light of 532 nm and induced fluorescent light at 653 nm resulting from O3 formed upon proton beam irradiation was measured with a spatial resolution of 2 lm in depth. The depth profiles of fluorescent light showed good agreement with those of energy deposition based on the SRIM code. The ESR measurement was carried out at room temperature and detected a signal of dangling bonds on Si. The radical density increased linearly with fluence for 1 MeV protons whereas it saturated for 2.5 MeV protons. The radical yield (the number of radicals per 100 eV absorption, G-value) was 1.1 · 10 4 for 1 MeV protons and 2.5 · 10 4 for 2.5 MeV protons, which increased with stopping power. 2005 Elsevier B.V. All rights reserved. PACS: 81.05.Kf; 61.80.Jh Keywords: Glass; Ion beam; Radiation effects; Micro-fluorescence; ESR
1. Introduction Optical fibers are used as temperature monitors in nuclear reactors, or as amplifiers on space satellites. Such fibers are subjected to radiation in nuclear reactor or space, therefore radiation damage and resistance of the material is very important. Effects due to gamma rays or neutron irradiation have been well studied and it is known that defects such as peroxy radicals (Si–O–O) are formed upon irradiation affecting light transmittance of the fiber [1]. The fiber is made of core and clad parts and irradiation experiments on quartz glass as core material have been carried out. The radiation in space is mostly electrons, protons and heavy *
Corresponding author. Fax: +81 29 287 8488. E-mail address: [email protected] (H. Kudo).
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.11.101
ions. Though radiation effect by electron beam is attributed to gamma rays as the secondary electrons cause radiation effects and well studied by using Co-60 gamma ray sources. However, irradiation effects by proton and heavy ion beams are less well known. In this work, SiO2 quartz glasses were irradiated with protons and Ni ions at a Van de Graaff or a Tandetron accelerator and changes in optical properties were investigated. 2. Experimental The SiO2 quartz glass used in this work has an OH content of 400–1000 ppm and a thickness of 0.1 and 1 mm. The glasses were irradiated with proton beams of 1 MeV or 2.5 MeV to fluence of 1 · 1015 or 1 · 1016 cm 2, at a Van de Graaff or a Tandetron accelerator at room temperature
202
H. Kudo et al. / Nucl. Instr. and Meth. in Phys. Res. B 245 (2006) 201–203
under vacuum. The irradiation was made at the high fluence irradiation facility of the research center for nuclear science and technology of the University of Tokyo (HIT). The range and stopping power of ions in SiO2 glass are 14 lm and 0.17 MeV cm2/g for 1 MeV protons and 66 lm and 0.29 MeV cm2/g for 2.5 MeV protons, respectively, according to the SRIM (stopping and ranges of ion in matter) code [2]. The irradiated materials were investigated by micro-fluorescence spectroscopy and electron spin resonance (ESR). 3. Results and discussion 3.1. Micro-fluorescence spectroscopy The micro-fluorescence spectroscopy uses a laser with an excitation light of 532 nm (JASCO NRS-3300). The proton irradiation induced a fluorescent light at 653 nm resulting from O3 formed [3]. The glass specimen of 1 mm thickness irradiated with protons horizontally, as shown in Fig. 1, was scanned in depth (i.e. parallel to the ion beam direction) with a spatial resolution of 2 lm. Fig. 2 shows a comparison of depth profiles of the fluorescence spectra after irradiation with 1 and 2.6 MeV protons to fluence of 1015 cm 2 and energy deposition (stopping power) based on the SRIM code. The signal intensity increases with depth and the peak intensities of both irradiations are equal. From the surface to near the Bragg peak, the profiles show good agreement between the experimental data and the SRIM calculation. However, the fluorescence profiles entered to a large depth, which indicates that the ion beam may cause irradiation effects in deeper regions than the range of the incident ions.
Fig. 2. A comparison of depth profiles of fluorescence light at 653 nm after irradiation of 1 and 2.6 MeV proton to fluence of 1015 cm 2 and energy deposition (stopping power) based on the SRIM code.
3.2. Electron spin resonance (ESR)
Sc an
in
D
ep
th
The ESR measurements were carried out at room temperature (JEOL, JES-FE2XG) and detected a signal of dangling bond on Si. Fig. 3 shows the ESR spectra of a
Range
Ion Beam
Fig. 1. Irradiation and sample preparation for micro-fluoresence spectroscopy.
Fig. 3. ESR spectrum of quartz glass measured at room temperature after irradiation of 1 MeV proton to fuences of 1015 and 1016 cm 2.
quartz glass measured at RT after the irradiation with of 1 MeV proton to fluences of 1015 and 1016 cm 2. A stable singlet signal at 338 mT is observed after irradiation and by comparing changes in UV–Vis and IR spectra [4] upon proton irradiation, the singlet is assigned to Si radicals [5]. Fig. 4 shows the spin density as a function of dose, where the spin density was evaluated based on a di-phenyl picryl hydrazyl (DPPH) standard and the dose is the product of the average stopping power (energy divided by range and density) and the fluence. The radical density increased linearly with fluence for 1 MeV protons whereas the density saturated for 2.5 MeV protons. This difference in behavior may come from the range and energy deposition of the proton in the glass. The radical yield (the number of radicals per 100 eV absorption, G-value) was evaluated by a linear fit yielding 1.1 · 10 4 for 1 MeV protons and 2.5 · 10 4
H. Kudo et al. / Nucl. Instr. and Meth. in Phys. Res. B 245 (2006) 201–203
203
with 1 and 2.5 MeV H+ beam to fluence of 1015 and 1016 cm 2. The spatial distribution in depth direction and the density of defects were investigated by means of micro-fluorescence spectroscopy and ESR. The depth profile of micro-fluorescence due to O3 showed good agreement with that of energy deposition as determined with the SRIM code. The ESR detected a signal assigned to Si radical. The yield was evaluated and increased with stopping power. These data would be of importance to evaluate radiation damage and resistance of optical fiber in radiation environment. Acknowledgements
Fig. 4. Spin density in glass by means of ESR based on DPPH standard measured at room temperature after irradiation of 1 and 2.5 MeV proton beam as a function of dose.
for 2.5 MeV protons, which increased with stopping power (0.17 MeV cm2/g for 1 MeV proton and 66 lm and 0.29 MeV cm2/g for 2.5 MeV proton). 4. Conclusion To study the radiation resistance and damage of optical fiber towards ion beams, SiO2 quartz glass was irradiated
The authors thank Dr. M. Iwata and Mr. Y. Muroya of the University of Tokyo. They also thank to Dr. T. Iwai and Mr. T. Omata for operation of ion accelerators. JASCO Co. Ltd., are acknowledged for micro-fluorescence spectroscopy analysis. Dr. T. Oka, Mr. M. Kondo, Mr. D. Ichiki and Prof. Y. Hama of Waseda University are also acknowledged for ESR measurements. References [1] K. Fujita, Doctoral thesis, The University of Tokyo, 2003. [2] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Ranges of Ions in Matter, Pergamon Press, Oxford, 1985. [3] Y. Sakurai, J. Non-Cryst. Solids 316 (2003) 389. [4] H. Kudo, T. Akagawa, to be published. [5] M. Fujinami, N. Chilton, Appl. Phys. Lett. 62 (1993) 1131.
Nuclear Instruments and Methods in Physics Research B 245 (2006) 201–203 www.elsevier.com/locate/nimb
Micro-fluoresence spectroscopy and ESR study on ion beam irradiated glass H. Kudo *, T. Akagawa, Y. Katsumura Nuclear Engineering Research Laboratory, School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188, Japan Available online 27 December 2005
Abstract Radiation effects on SiO2 glasses are well studied but not fully understood especially towards ion beam irradiation. In this work, SiO2 glasses, with an OH content of 400–1000 ppm and a thickness of 0.1 and 1 mm, were irradiated with proton beams of 1 MeV or 2.5 MeV to fluences of 1 · 1015 or 1 · 1016 cm 2, at a Van de Graaff or a Tandetron accelerator at room temperature under vacuum. The range and stopping power of the ions in SiO2 glass are 14 lm and 0.17 MeVcm2/g for 1 MeV proton and 66 lm and 0.29 MeVcm2/g for 2.5 MeV proton, respectively, according to the SRIM (stopping and ranges of ion in matter) code. The materials were subjected to micro-fluorescence spectroscopy and electron spin resonance (ESR) measurements. The micro-fluorescence spectroscopy uses excitation light of 532 nm and induced fluorescent light at 653 nm resulting from O3 formed upon proton beam irradiation was measured with a spatial resolution of 2 lm in depth. The depth profiles of fluorescent light showed good agreement with those of energy deposition based on the SRIM code. The ESR measurement was carried out at room temperature and detected a signal of dangling bonds on Si. The radical density increased linearly with fluence for 1 MeV protons whereas it saturated for 2.5 MeV protons. The radical yield (the number of radicals per 100 eV absorption, G-value) was 1.1 · 10 4 for 1 MeV protons and 2.5 · 10 4 for 2.5 MeV protons, which increased with stopping power. 2005 Elsevier B.V. All rights reserved. PACS: 81.05.Kf; 61.80.Jh Keywords: Glass; Ion beam; Radiation effects; Micro-fluorescence; ESR
1. Introduction Optical fibers are used as temperature monitors in nuclear reactors, or as amplifiers on space satellites. Such fibers are subjected to radiation in nuclear reactor or space, therefore radiation damage and resistance of the material is very important. Effects due to gamma rays or neutron irradiation have been well studied and it is known that defects such as peroxy radicals (Si–O–O) are formed upon irradiation affecting light transmittance of the fiber [1]. The fiber is made of core and clad parts and irradiation experiments on quartz glass as core material have been carried out. The radiation in space is mostly electrons, protons and heavy *
Corresponding author. Fax: +81 29 287 8488. E-mail address: [email protected] (H. Kudo).
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.11.101
ions. Though radiation effect by electron beam is attributed to gamma rays as the secondary electrons cause radiation effects and well studied by using Co-60 gamma ray sources. However, irradiation effects by proton and heavy ion beams are less well known. In this work, SiO2 quartz glasses were irradiated with protons and Ni ions at a Van de Graaff or a Tandetron accelerator and changes in optical properties were investigated. 2. Experimental The SiO2 quartz glass used in this work has an OH content of 400–1000 ppm and a thickness of 0.1 and 1 mm. The glasses were irradiated with proton beams of 1 MeV or 2.5 MeV to fluence of 1 · 1015 or 1 · 1016 cm 2, at a Van de Graaff or a Tandetron accelerator at room temperature
202
H. Kudo et al. / Nucl. Instr. and Meth. in Phys. Res. B 245 (2006) 201–203
under vacuum. The irradiation was made at the high fluence irradiation facility of the research center for nuclear science and technology of the University of Tokyo (HIT). The range and stopping power of ions in SiO2 glass are 14 lm and 0.17 MeV cm2/g for 1 MeV protons and 66 lm and 0.29 MeV cm2/g for 2.5 MeV protons, respectively, according to the SRIM (stopping and ranges of ion in matter) code [2]. The irradiated materials were investigated by micro-fluorescence spectroscopy and electron spin resonance (ESR). 3. Results and discussion 3.1. Micro-fluorescence spectroscopy The micro-fluorescence spectroscopy uses a laser with an excitation light of 532 nm (JASCO NRS-3300). The proton irradiation induced a fluorescent light at 653 nm resulting from O3 formed [3]. The glass specimen of 1 mm thickness irradiated with protons horizontally, as shown in Fig. 1, was scanned in depth (i.e. parallel to the ion beam direction) with a spatial resolution of 2 lm. Fig. 2 shows a comparison of depth profiles of the fluorescence spectra after irradiation with 1 and 2.6 MeV protons to fluence of 1015 cm 2 and energy deposition (stopping power) based on the SRIM code. The signal intensity increases with depth and the peak intensities of both irradiations are equal. From the surface to near the Bragg peak, the profiles show good agreement between the experimental data and the SRIM calculation. However, the fluorescence profiles entered to a large depth, which indicates that the ion beam may cause irradiation effects in deeper regions than the range of the incident ions.
Fig. 2. A comparison of depth profiles of fluorescence light at 653 nm after irradiation of 1 and 2.6 MeV proton to fluence of 1015 cm 2 and energy deposition (stopping power) based on the SRIM code.
3.2. Electron spin resonance (ESR)
Sc an
in
D
ep
th
The ESR measurements were carried out at room temperature (JEOL, JES-FE2XG) and detected a signal of dangling bond on Si. Fig. 3 shows the ESR spectra of a
Range
Ion Beam
Fig. 1. Irradiation and sample preparation for micro-fluoresence spectroscopy.
Fig. 3. ESR spectrum of quartz glass measured at room temperature after irradiation of 1 MeV proton to fuences of 1015 and 1016 cm 2.
quartz glass measured at RT after the irradiation with of 1 MeV proton to fluences of 1015 and 1016 cm 2. A stable singlet signal at 338 mT is observed after irradiation and by comparing changes in UV–Vis and IR spectra [4] upon proton irradiation, the singlet is assigned to Si radicals [5]. Fig. 4 shows the spin density as a function of dose, where the spin density was evaluated based on a di-phenyl picryl hydrazyl (DPPH) standard and the dose is the product of the average stopping power (energy divided by range and density) and the fluence. The radical density increased linearly with fluence for 1 MeV protons whereas the density saturated for 2.5 MeV protons. This difference in behavior may come from the range and energy deposition of the proton in the glass. The radical yield (the number of radicals per 100 eV absorption, G-value) was evaluated by a linear fit yielding 1.1 · 10 4 for 1 MeV protons and 2.5 · 10 4
H. Kudo et al. / Nucl. Instr. and Meth. in Phys. Res. B 245 (2006) 201–203
203
with 1 and 2.5 MeV H+ beam to fluence of 1015 and 1016 cm 2. The spatial distribution in depth direction and the density of defects were investigated by means of micro-fluorescence spectroscopy and ESR. The depth profile of micro-fluorescence due to O3 showed good agreement with that of energy deposition as determined with the SRIM code. The ESR detected a signal assigned to Si radical. The yield was evaluated and increased with stopping power. These data would be of importance to evaluate radiation damage and resistance of optical fiber in radiation environment. Acknowledgements
Fig. 4. Spin density in glass by means of ESR based on DPPH standard measured at room temperature after irradiation of 1 and 2.5 MeV proton beam as a function of dose.
for 2.5 MeV protons, which increased with stopping power (0.17 MeV cm2/g for 1 MeV proton and 66 lm and 0.29 MeV cm2/g for 2.5 MeV proton). 4. Conclusion To study the radiation resistance and damage of optical fiber towards ion beams, SiO2 quartz glass was irradiated
The authors thank Dr. M. Iwata and Mr. Y. Muroya of the University of Tokyo. They also thank to Dr. T. Iwai and Mr. T. Omata for operation of ion accelerators. JASCO Co. Ltd., are acknowledged for micro-fluorescence spectroscopy analysis. Dr. T. Oka, Mr. M. Kondo, Mr. D. Ichiki and Prof. Y. Hama of Waseda University are also acknowledged for ESR measurements. References [1] K. Fujita, Doctoral thesis, The University of Tokyo, 2003. [2] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Ranges of Ions in Matter, Pergamon Press, Oxford, 1985. [3] Y. Sakurai, J. Non-Cryst. Solids 316 (2003) 389. [4] H. Kudo, T. Akagawa, to be published. [5] M. Fujinami, N. Chilton, Appl. Phys. Lett. 62 (1993) 1131.