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« Radiation-induced processes in silica core high-OH optical fibers under gamma-irradiation of 60 Co » . Baydjanov M. Turin Polytechnic University in Tashkent www.polito.uz Institute of Nuclear Physics, Uzbekistan www.inp.uz. Application of silica optical fibers Telecommunication

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Baydjanov m turin polytechnic university in tashkent polito uz

«Radiation-induced processes in silica core high-OH optical fibers under gamma-irradiation of 60Co»

Baydjanov M.

Turin Polytechnic University in Tashkent www.polito.uz

Institute of Nuclear Physics, Uzbekistan www.inp.uz


Baydjanov m turin polytechnic university in tashkent polito uz

  • Application of silica optical fibers

  • Telecommunication

  • Sensors

  • Dosimeters

  • Medicine

  • Radiation-resistant optical fibers

  • DESY – beam loss monitoring

  • Nuclear Reactors – transfer information in IR-region of spectrum

  • LHC CERN – detection of high-energy charged particles

  • UV-irradiation in medicine

  • Nuclear Power Plant

  • In the future

  • ITER – plasma diagnostics (400-700 nm)

  • Space technologies

  • Expansion of optical fiber application fields is continuing


Baydjanov m turin polytechnic university in tashkent polito uz

Optical fiber samples

Polymicro Technologies LLC

clad

polymer

clad

(F) SiO2

core

SiO2

Buffer

CCDR=1.1

(Clad to core ratio)

Effective range of high-OH fibers is 400 – 500 nm


Baydjanov m turin polytechnic university in tashkent polito uz

PURE SILICA FIBERS with High-OH group content

www.polymicro.com

  • Why OH-groups?

  • OH-groups are formed during adding hydrogen gas during optical fiber drawing.

  • Accompanied with two main processes:

  • suppressing ruptured Si-O-Si bonds during fiber drawing

  • reducing radiation-induced defects

  • OH-groups are necessary to increase a radiation resistance

≡Si–O–Si ≡ → Si•+ •O–Si → ≡Si–H + H–O–Si≡

≡Si• – electronic E′-center - absorption band 215 nm

•O–Si≡ – Non-bridging oxygen hole center (NBOHC) - absorption band 260, 620 nm

≡Si–O–H •O–Si≡ – NBOHC-H - absorption band 600 nm

MPNP’09


Baydjanov m turin polytechnic university in tashkent polito uz

  • What happens to optical parameters of fibers under the influence of ionizing radiation?

  • Radiation-induced absorption(induced losses) of light caused by color centers

  • Radiation-induced light emission

    • Cherenkov’s effect – high-energy charged particles

    • Luminescence of color centers

    • Reabsorption of induced emission


Baydjanov m turin polytechnic university in tashkent polito uz

3

3

6

2

5

1

4

γ-rays

γ-rays

7

Fig.1.Experimental setup for in-situ measurements of radiation induced losses and light emission under γ-irradiation of60Co (1.25 MeV): 1) Probing lamp; 2) Lenses; 3) connectors; 4) Transporting part of fiber5) EPP2000C Spectrometer; 6) PC; 7) Irradiated part of fiber coiled into a ring with diameter 4.5 cm.


Baydjanov m turin polytechnic university in tashkent polito uz

Radiation induced losses of transmission

In-situ measurement of losses

Stable losses

Unstable losses

Transient color centers

Unstable color centers

Stable color centers

- in-situ losses

- stable losses

- unstable losses


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 2. High-OH fiber FVP300: Relaxation kinetics after γ-irradiation.

Unstable losses are caused by unstable color centers that are created under irradiation and annealed within 10 min.

Stable losses are caused by stable color centers that are created under irradiation and living longer than 10 min.


Baydjanov m turin polytechnic university in tashkent polito uz

Low-OH FIP300

High-OH FVP300

Fig. 3. γ-induced in-situ losses:

a) FVP300 at dose rate6R/s(1) 8∙106; (3) 3,5∙107Rad; at dose rate360R/s(2) 8∙106; (4) 3,5∙107.

b) FIP300 at dose rate6 R/s(1) 3,5∙106; (2) 8∙106Rad; at dose rate360R/s(3) 3,5∙106; (4)8∙106 Rad.

The magnitude of in-situ losses depends not-only on radiation dose but also dose rate


Baydjanov m turin polytechnic university in tashkent polito uz

In-situ losses at dose rate 6 R/s

Fig. 5. (1) 1,2∙105; (2) 3,6∙105; (3) 5∙105Rad

Fig. 4. (1) 3,3∙103; (2) 2∙104; (3) 4∙105; (4) 3,5∙106; (5) 107; (6) 6∙107Rad.

(1) 1.7 ∙105; (2) 1.5 ∙106; (3) 4.8 ∙106; (4) 8 ∙106; (5) 3.4 ∙107; (6) 8.45 ∙107 Rad

(1) 3.6 ∙103; (2) 104; (3) 4 ∙104; (4) 4.5 ∙105


Baydjanov m turin polytechnic university in tashkent polito uz

Optical fibers with pure silica core and F-silica clad and high-OH group content shows better radiation resistance and that optical fibers with same core and polymer clad.

But the cost of silica/polymer fibers are low and diameter is higher .

If the maximum annual dose is not more that 108 Rad and temperature is under 100°C in addition very long length of fiber is required then it is convenient to use silica/polymer fibers.

Optical fiber with buffer (coating) Tefzel is not radiation resistant!


Baydjanov m turin polytechnic university in tashkent polito uz

Comparing stable and unstable losses

Fig. 6. In-situ (1), stable (2) and unstable (3) losses spectrainFSHA600, measured at 10 R/s. The length of irradiated part is L=5 m.


Baydjanov m turin polytechnic university in tashkent polito uz

8

4

FVP300

FSHA600

6

dB/m

dB/m

),

λ

4

(

),

2

A

λ

(

A

2

0

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2?

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Dose, Rad (log. scale)

Fig 7. Dose dependency of induced losses at 610 nm in high-OH fibers.

≡ Si – O – Si ≡ → ≡ Si – O• + •Si≡(1)

≡ Si – O – HH – O – Si ≡ → ≡ Si – O• H – O – Si ≡ + H+(2)

≡ Si – H → ≡ Si•H0orHCl(3)

≡ Si – O – H → ≡ Si – O• + HCl(4)

≡ Si – Cl → ≡ Si•HCl(5)


Baydjanov m turin polytechnic university in tashkent polito uz

Increasing of unstable losses intensity with dose

  • Fig. 9. Unstable losses spectra forlow- OH FIP300 at the doses:

  • 1) 2,3·105; 2) 106; 3) 1,7·106; 4) 2·106; 5) 3,5·106; 6) 8·106; 7) 3,4·107; 8) 6·107; 9) 1,5·108; 10) 2·108Rad (Р=360 R/s)

  • Fig. 8. Unstable losses spectra for high-OHFVP300 at the doses:

  • 1) 9,2·104; 2) 106; 3) 4,7·106; 4) 7,9·106; 5) 3,4·107; 6) 5,9·107; 7) 8,4·107; 8) 108; 9) 2·108Rad (P=360 R/s).

≡ Si – O – Si ≡ → ≡ Si – O- + •Si≡(6)

≡ Si – H → ≡ Si• + H+(7)

≡ Si – O – H → ≡ Si – O• + H + (8)

≡ Si – Cl → ≡ Si• +Cl(9)


Baydjanov m turin polytechnic university in tashkent polito uz

FVP300

FSHA600

Dose, Rad (Log. scale)

Dose, Rad (Log. scale)

FIP300

105

106

107

108

109

Dose, Rad (Log. scale)

105

106

107

108

104

105

106

107

108

109

Fig. 10. Dose dependency of unstable losses in high-OH fibers.

Fig. 11. Dose dependency of unstable losses in low-OH fibers


Baydjanov m turin polytechnic university in tashkent polito uz

If the diameter of the core of fiber is larger then the number of unstable color centers will be smaller, so fiber becomes more resistant to radiation.

Linear dependence of unstable losses and saturation effect can be used for dosimetry purposes.


Baydjanov m turin polytechnic university in tashkent polito uz

If unstable losses are caused by unstable color centers then where is its maximum located?

What is the nature of this center?

How the number of this center can be reduced?


Baydjanov m turin polytechnic university in tashkent polito uz

UV-induced losses in high –OH fuber

Fig. 12. UV-induced losses spectra in high-OH fiberFVP300: (1) right after irradiation (2) 10 min after irradiation;

Fig. 13. Difference of (1) – (2) from Fig. 12.

Fig. 14. UV-induced losses spectra after excitation pulses n=20 – 100.


Baydjanov m turin polytechnic university in tashkent polito uz

3

1.4

2

1

1

2.5

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1.4

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Dose rate, R/s

Dose rate, R/s

4,7·106 Рад

3,4·107Rad

4,7·106Rad

8·106Rad

Fig. 15. Dose rate dependency of induced lossesin high-OH fiberFVP300 in wavelength range 450 nm: 1) in-situ; 2) unstable.

4,7·106Rad

3,4·107Rad

8·106Rad

Fig. 16. Dose rate dependency of unstable lossesin high-OH fiberFVP300in different wavelength ranges: 1) 400 nm; 2) 450 nm; 3) 600 nm.

Linear dependence can be used as a parameter to control radiation dose rate


Baydjanov m turin polytechnic university in tashkent polito uz

γ-Radiation Induced Light Emission

Radioluminescence

Cherenkov’s emission

Spectrometer

Transporting part - L

Irradiated part - lg


Baydjanov m turin polytechnic university in tashkent polito uz

lg

L

Influence of reabsorption process on radiation-induced emission in fibers

Intensity of Cherenkov’s emission

(1)

IR(λ) – Intensity of Cherenkov’s emission exposed to reabsorption within transporting (L) and irradiated (lg) lengths of optical fiber


Baydjanov m turin polytechnic university in tashkent polito uz

a)

b)

IR(λ), arb. un.

IR(λ), arb. un.

1

1

2

2

3

3

4

4

λ, nm

λ, nm

Fig. 17. Possible spectra of Cherenkov’s emission plotted by formula (1) at different given values for lgandL:

a) 1 – Real spectrum of Cherenkov’s emission plotted by formula I0(λ)=k/λ3;

2 – lg=4 mandL=22 m.A(λ)forD=106Rad, P=70 R/s (МТ-22С-accelerator));

3 – lg=3 m и L=6 m, A(λ) при D=1,5∙106 Рад, P=360 Р/с;

4 – при D=1,5∙106 Рад.

b) A(λ) forD=106Rad; P=70 R/s (МТ-22С-accelerator), 1 – построенный по I0(λ)=k/λ3;

2 – L=5 m;

3 – L=22 m;

4 – L=50 m.


Baydjanov m turin polytechnic university in tashkent polito uz

Dependence of the length of transporting fiber on reabsorption

0

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a)

Zoom a)

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Fig. 2. Theoretical Cherenkov’s emission spectra (curve (0)) and plotted by eq. 2) for different length of fiber samples: a) FVP; b) J-LowSol; c) J-UltraSol. Numbered curves correspond to the length of fibers as follows: (1) – 1 m; (2) – 2 m; (3) – 5 m; (4) – 10 m; (5) – 20 m; (6) – 50 m; (7) – 75 m; (8) – 100 m; (9) – 150 m; (10) – 200 m; (11) – 250 m; (12) – 300 m; (13) – 400 m; (14) – 500 m; (15) – 103 m.

5


Baydjanov m turin polytechnic university in tashkent polito uz

From 1 to 20 m J-UltraSol sample has the best performance, 2nd FVP and 3rd is J-LowSol.

At the length of 20 m for J-UltraSol the intensity magnitude is still highest while for FVP and J-LowSol it is comparably equal.

At 20 < L < 75 m J-UltraSol, J-LowSol and FVP correspondingly in order of highest intensity to lowest.

100 < L < 250 m – J-UltraSol, FVP, J-LowSol.

250 < L < 1000 m – FVP, J-UltraSol, J-LowSol.

5

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7

Zoom c)

1

c)

8

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Baydjanov m turin polytechnic university in tashkent polito uz

Reabsorption takes place in irradiated and transporting parts of optical fibers.

Reabsorption depends on the lengths of irradiated part, transporting part and dose of irradiation.

Reabsorption changes the shape of real spectrum – deformation of spectrum.

Is it possible to restore the real shape of the spectra?

Yes, if we measure in-situ losses simultaneously with radiation-induced emission spectrum!


Method of restoring the true emission spectra

Irradiated part of fiber

l

I0

Method of restoring the true emission spectra

Details in Jap. J. Appl. Phys. 2008 (47) 1 301-302.

Intensity of true emission with taking into account reabsorption within irradiated and transporting parts of optical fiber.


Baydjanov m turin polytechnic university in tashkent polito uz

FVP300

false

FVP300

true

  • Fig. 18. γ-induced light emission spectra of high-OH fibers: a) measured; b) andc) after calculations.

  • 1 – 7,3∙104; 2 – 1,4∙106; 3 – 5∙106; 4 –8∙106; 5 – 3,45∙107; 6 – 6∙107Рад, P=360Р/с.

c)


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 19. Difference of spectra (6) and (1) from Fig. 18 b) and c).

  • Fig. 20. Real spectrum(1), Cherenkov’s emission spectrum(1/λ3) (2) and their difference(3).


Baydjanov m turin polytechnic university in tashkent polito uz

1,5

1,5

1

1

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0,5

650

650

350

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850

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λ,nm

Intensity arb. units

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Intensity arb. units

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Fig. 21. γ-induced light emission of high-OHFVP300:

а) at dose rates 6 (1), 65 (2), 160 (3), 360 R/s(4);

b) Different of curves4-1. Irradiated by60Со source.

b)

a)

Fig. 21. γ-induced light emission of high-OHFVP300:

а) at dose rates 10 (1), 40 (2), 70 (3)R/s;

b) Different of curves3-1. Irradiated by bremmhstrahlungγ-radiation of MT-22C accelerator.


Baydjanov m turin polytechnic university in tashkent polito uz

Fig.23. Dose rate dependency of emission intensity at the wavelength 450 and650 nm.

Increasing dose rate brings to the increase of the number secondary electrons responsible for Cherenkov’s emission therefore its intensity increases linearly.

This linear dependence of radiation induced light emission can be used to control dose rates of radiation sources or beam loss monitoring.


Baydjanov m turin polytechnic university in tashkent polito uz

In-situ measurements can give us full information about optical properties of radiation resistant fibers.

Reabsorption causes deformation of radiation-induced emission spectra therefore it must be taken into account.

Linear dependencies of unstable losses, light emission on dose or dose rate can be used in development of fiber based detectors of radiation.

The method presented here probably can be used in beam loss monitoring with silica fibers.


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 24. Dose dependencies of absorption band at(1) 610 nm, luminescence bands(2) 450 and(3) 650 nm. (norm. un.)

  • It was supposed that 610 nm absorption band is formed by the sum of absorption bands of two types of NBOHC: 600 nm (Si–O• H–O–Si) and 630 nmSi–O•

  • Difference in dose dependencies of absorption band 610 nm and luminescence bands 450 and 650 nm shows that :

  • some part of NBOHC are making non-radiative relaxation.

  • different centers other than NBOHC are also responsible for formation of 610 nm absorption band.


Baydjanov m turin polytechnic university in tashkent polito uz

Influence of preliminary neutron irradiation on color centers creation under gamma-irradiation

  • Fig.25. γ-induced losses spectra of high-OH FVP300 fiber preliminary unirradiated by neutrons at the doses:

  • 103(1), 5·103 (2), 104 (3), 5·104 (4), 5·106 (5), 5·107 (6) and108Rad(7)

    • а) UV-range.

    • б) differences of spectra;

    • в) VIS-range

9

8

7

6

5

4

3

2

1


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 26. γ-induced losses spectra of high-OH FVP300 fiber preliminary irradiated by neutrons fluence1012n·cm-2

UV-range;

VIS-range.

Doses: 105(1), 5·105 (2), 106 (3, 4), 5·106 (5), 107 (6), 5·107 (7), 108Rad(8).


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 27. γ-induced losses spectra of high-OH FVP300 fiber preliminary irradiated by neutrons fluence1014n·cm-2

Doses 105(2), 5.105 (3), 106 (4), 9.106 (5), 1,5.107 (6) and6,5.107Rad(7)

Fig. 28. Kinetics of change of the value of A(λ) at 610 nm in

preliminary unirradiated.

preliminary irradiated by 1012n·cm-2.

1014n·cm-2.


Baydjanov m turin polytechnic university in tashkent polito uz

Si

O

H

γ

e+

γ

e-

e+

γ

e-

e-


Baydjanov m turin polytechnic university in tashkent polito uz

Effect of high temperature heating on transmission recovery of irradiated high-OH fibers

Fig.29. Spectra of γ-induced losses before Aγ(λ) (1) and after heating ΔAi(λ) after the following temperatures:

1000С (2);

1500С (3);

2000С (4);

2500С (5);

3000С (6);

3500С (7);

(8) 4000С;

(9) 4500С;

(10) 5000С;

(11) 5500С;

(12) 6000С;

(13) after cooling to room temperature.


Baydjanov m turin polytechnic university in tashkent polito uz

Fig. 30. Difference of curves of Fig 29.:

1) 1-2;2) 2-3; 3) 3-4; 4) 4-5;5) 5-6;7) 7-8;8) 8-9;9) 9-10;10) 10-11;11) 11-12;6) 6-7;12) 12-13;

Fig. 31. Temperature dependence of K(λ)=Ai(λ)/Aγ(λ)


Baydjanov m turin polytechnic university in tashkent polito uz

Dankefür die Aufmerksamkeit

Thank you for your attention

Спасибо за внимание

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