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

Baydjanov M.

Turin Polytechnic University in Tashkent www.polito.uzInstitute of Nuclear Physics, Uzbekistan www.inp.uz

2

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

Polymicro Technologies LLC

3

coreSiO2

Optical fiber

Type of core diameter, μm

Type of clad diameter, μm

Protective buffer

OH-group content, ppm

FVP300 SiO2 , 300 (F)SiO2 , 330 Polyimide 1000FIP300 SiO2 , 300 (F)SiO2 , 330 Polyimide <1

FSHA600 SiO2 , 600 Polymer , 660 Acrylate 1000JTFLH600 SiO2 , 600 Polymer , 660 Tefzel <1

Optical fiber samples

CCDR =1.1(Clad to core ratio)

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

clad(F) SiO2

Buffer

cladpolymer

4

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≡

PURE SILICA FIBERS with High-OH group content

≡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

www.polymicro.com

5

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

γ-rays γ-rays

1 2

3 3

4

5 6

7

Fig.1. Experimental setup for in-situ measurements of radiation induced losses and light emission under γ-irradiation of 60Co (1.25 MeV): 1) Probing lamp; 2) Lenses; 3) connectors; 4) Transporting part of fiber 5) EPP2000C Spectrometer; 6) PC; 7) Irradiated part of fiber coiled into a ring with diameter 4.5 cm.

6

7

Radiation induced losses of transmission

In-situ measurement of losses

Stable losses Unstable losses

Stable color centers Transient color centersUnstable color centers

- in-situ losses

- stable losses - unstable losses

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

8

00 02 05 08 11 14 17 200

0.5

1

1.5

2

2.5 450nmP=360R/s

92kRad 1Mrad4.7MRad 8MRad84MRad

t, min

A(λ

), dB

/m

00 02 05 08 11 14 17 200.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2 P=360R/s, D=84MRad

610nm 500nm450nm 400nm

t, min

A(λ

), re

lativ

e.un

.

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.

9

0

0.5

1

1.5

2

2.5

3

3.5

4

300 400 500 600 700 800λ, нм

A(λ

), дБ

/м

1

2

34

а)

0

1

2

3

4

5

6

7

8

500 550 600 650 700 750 800 850λ, нм

A(λ

), дБ

/м

1

2 3 4

б)

Fig. 3. γ-induced in-situ losses:a) FVP300 at dose rate 6R/s (1) 8 10∙ 6; (3) 3,5 10∙ 7 Rad; at dose rate 360 R/s (2) 8 10∙ 6; (4) 3,5 10∙ 7.b) FIP300 at dose rate 6 R/s (1) 3,5 10∙ 6; (2) 8 10∙ 6 Rad; at dose rate 360 R/s (3) 3,5 10∙ 6; (4) 8 10∙ 6

Rad.

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

High-OH FVP300

Low-OH FIP300

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

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

10

400 450 500 550 600 650 700 750 800 8500

0.51

1.52

2.53

3.54

4.55

λ, nm

A(λ

), dB

/m

1

23

Low-OH JT-FLH600

400 450 500 550 600 650 700 750 800 8500123456789

10

λ, nm

A(λ

), dB

/m

1

65

43

2

Low-OH FIP300

300 350 400 450 500 550 600 650 700 750 800 8500

0.51

1.52

2.53

3.54

4.55

λ, nm

A(λ

), dB

/m

12

34

56

High-OH FVP300

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

300 350 400 450 500 550 600 650 700 750 800 8500.0

0.2

0.4

0.6

0.8

1.0

λ, nm

A(λ

), dB

/m1 2

3

4

High-OH FSHA600

In-situ losses at dose rate 6 R/s

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

11

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!

0

0.1

0.2

350 400 450 500 550 600 650λ, нм

A(λ

), дБ

/м

D=7.8кРад

1

2

3

D=52.4кРад

0

0.1

0.2

0.3

0.4

350 400 450 500 550 600 650λ, нм

A(λ

), дБ

/м

123

1

D=0.75МРад

0

0.5

1

1.5

350 400 450 500 550 600 650λ, нм

A(λ

), дБ

/м

12

31

30

0.5

1

1.5

2

2.5

350 400 450 500 550 600 650λ, нм

A(λ

), дБ

/м

D=1.45МРад

123

Fig. 6. In-situ (1), stable (2) and unstable (3) losses spectra in FSHA600, measured at 10 R/s. The length of irradiated part is L=5 m.

12

Comparing stable and unstable losses

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

≡ Si – O – Si ≡ → ≡ Si – O• + •Si ≡ (1)

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

≡ Si – H → ≡ Si• H0 or HCl (3)

≡ Si – O – H → ≡ Si – O• + HCl (4)

≡ Si – Cl → ≡ Si• HCl (5)

13

A(λ)

, dB

/m

Dose, Rad (log. scale)

0

2

4

105 106 107 108

FSHA600

0

2

4

6

8

Dose, Rad (log. scale)

105 106 107 108

A(λ)

, dB

/m

2?108

FVP300

Fig. 8. Unstable losses spectra for high-OH FVP300 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) 2·108 Rad (P=360 R/s).

Fig. 9. Unstable losses spectra for low- 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) 2·108 Rad (Р=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)

00.5

11.5

22.5

33.5

44.5

5

500 550 600 650 700 750 800 850λ, nm

A(λ

), дБ

/м

1

2

345

6 7-10

00.20.40.60.8

11.21.41.61.8

2

300 350 400 450 500 550 600 650 700 750λ, nm

A(λ

), дБ

/м

12

3

45-8

14

Increasing of unstable losses intensity with dose

0

0.2

0.4

0.6

0.8

1

1.2

1.4A

(λ),

дБ/м

400 нм450 нм500 нм

105 106 107 108

Dose, Rad (Log. scale)

FSHA600

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

A(λ

), дБ

/м

400нм450нм500нм610нм

104 105 106 107 108 109

Dose, Rad (Log. scale)

FVP300

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

0

0.5

1

1.5

2

2.5

3

3.5

4

A(λ

), дБ

/м

650 нм670 нм700 нм650670700

Dose, Rad (Log. scale)105 106 107 108 109

FIP300

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

15

16

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.

17

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?

Fig. 12. UV-induced losses spectra in high-OH fiber FVP300: (1) right after irradiation (2) 10 min after irradiation;

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

012345678

200 220 240 260 280 300λ, нм

A(λ

), дБ

/м

1

2

0

0.2

0.4

0.6

0.8

1

1.2

200 220 240 260 280 300λ, нм

A(λ

), дБ

/м

1 - 2

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

012345678

200 220 240 260 280 300λ, нм

A(λ

), дБ

/м

20

3040

50 6070

8090

100

18

UV-induced losses in high –OH fuber

00.20.40.60.8

11.21.41.6

0 100 200 300 400Dose rate, R/s

A(λ

), dB

/m

1

2

3

00.20.40.60.8

11.21.4

0 100 200 300 400Dose rate, R/s

A(λ

), dB

/m

1

2

3

00.20.40.6

0.81

1.21.4

0 100 200 300 400Dose rate, R/s

A(λ

), dB

/m

1

2

3

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400Dose rate, R/s

A(λ

), dB

/m

1

2

00.20.40.60.8

11.21.4

0 100 200 300 400Dose rate, R/s

A(λ

), dB

/m

1

2

Fig. 15. Dose rate dependency of induced losses in high-OH fiber FVP300 in wavelength range 450 nm: 1) in-situ; 2) unstable.

4,7·106 Рад 3,4·107 Rad

4,7·106 Rad 8·106 Rad 3,4·107 Rad

Fig. 16. Dose rate dependency of unstable losses in high-OH fiber FVP300 in different wavelength ranges: 1) 400 nm; 2) 450 nm; 3) 600 nm.

Linear dependence can be used as a parameter to control radiation dose rate19

0

0.5

1

1.5

2

0 100 200 300 400Dose rate, R/s

A(λ)

, dB/

m 1

2

4,7·106 Rad 8·106 Rad

20

γ-Radiation Induced Light Emission

Cherenkov’s emission Radioluminescence

Transporting part - L

Spectrometer

Irradiated part - lg

Influence of reabsorption process on radiation-induced emission in fibers

Intensity of Cherenkov’s emission

N

n

lnlALAR II g

10

1,01.0 1010 0

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

lg L

(1)

301~

I

21

350 450 550 650 750 8500

0.5

1

1.5

2

λ, nm

I R(λ

), ar

b. u

n.

a)1

2

34

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

a) 1 – Real spectrum of Cherenkov’s emission plotted by formula I0(λ)=k/λ3;2 – lg=4 m and L=22 m. A(λ) for D=106 Rad, P=70 R/s (МТ-22С-accelerator));3 – lg=3 m и L=6 m, A(λ) при D=1,5 10∙ 6 Рад, P=360 Р/с;4 – при D=1,5 10∙ 6 Рад.

b) A(λ) for D=106 Rad; 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.

350 450 550 650 750 8500

0.5

1

1.5

2

λ, nm

I R(λ

), ar

b. u

n.

b)1

2

34

22

23

Dependence of the length of transporting fiber on reabsorption

200 300 400 500 600 700 8000

0.02

0.04

0.06

0.08

Wavelength, nm

Inte

nsity

, arb

. uni

ts

Zoom a)5 6 7

8910

1112

13

1415

200 300 400 500 600 700 8000

0.2

0.4

0.6

0.8

1

Wavelength, nm

Inte

nsity

, arb

. uni

ts

a)0

1

2

3

4

5

0

1

2

34

200 300 400 500 600 700 8000

0.2

0.4

0.6

0.8

1

Wavelength, nm

Inte

nsity

, arb

. uni

ts

b)

5

200 300 400 500 600 700 8000

0.02

0.04

0.06

0.08

Wavelength, nmIn

tens

ity, a

rb. u

nits

5

6

7

8 9

1011

1213

1415

Zoom b)

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.

24

200 300 400 500 600 700 8000

0.2

0.4

0.6

0.8

1

Wavelength, nm

Inte

nsity

, arb

. uni

ts

c)0 12

3

4

56

200 300 400 500 600 700 8000

0.02

0.04

0.06

0.08

Wavelength, nm

Inte

nsity

, arb

. uni

ts

Zoom c)5

6

7 8

91011

1213

1415

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.

25

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

26

l

I0

Irradiated part of fiber

AAlNAAlAAL

AAlLA

Rirr

trINI000

0

0

1.011.01.0

1.01.0

101010

11010

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

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

Fig. 18. γ-induced light emission spectra of high-OH fibers: a) measured; b) and c) after calculations.1 – 7,3∙104; 2 – 1,4∙106; 3 – 5∙106; 4 – 8∙106; 5 – 3,45∙107; 6 – 6∙107 Рад, P=360Р/с.

27

c)

FVP300true

FVP300false

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

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

28

λ, nm 350 450 550 650 750 850

0,5

1

1,5

λ, nm 350 450 550 650 750 850

0,5

1

1,5

Inte

nsity

arb

. uni

ts

12

3

44-1

350 450 550 650 750 850λ, nm

0

1

1,5

1

3

20,5

б)

350 450 550 650 750 850λ, nm

0

1

1,5

3-1

0,5

Inte

nsity

arb

. uni

ts

Fig. 21. γ-induced light emission of high-OH FVP300:а) at dose rates 10 (1), 40 (2), 70 (3) R/s;b) Different of curves 3-1. Irradiated by bremmhstrahlung γ-radiation of MT-22C accelerator.

Fig. 21. γ-induced light emission of high-OH FVP300:а) at dose rates 6 (1), 65 (2), 160 (3), 360 R/s (4);b) Different of curves 4-1. Irradiated by 60Со source.

29

a)

a) b)

b)

30

Fig. 23. Dose rate dependency of emission intensity at the wavelength 450 and 650 nm.

0

2

4

6

8

10

12

0 100 200 300 400P, R/s

Inte

nsity

, arb

.un.

450 nm

650 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.

31

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.

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 nm Si–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.

32

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

0

20

40

60

80

100

120

140

200 250 300 350 400λ, нм

A(λ

), дБ

/м

3-1

2-1

4-1

0

20

40

60

80

100

120

200 250 300 350λ, нм

A(λ

), дБ

/м

1

7

6

54

3

2

0

1

2

3

4

5

6

7

350 450 550 650 750 850λ, нм

A(λ

), дБ

/м

1- 92кРад2- 1МРад3- 4,7МРад4- 8МРад5- 34МРад6- 34,5МРад7- 84МРад8- 0.1ГРад9- 2ГРад

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) and 108 Rad (7)

а) UV-range.б) differences of spectra;в) VIS-range

1234

5

67

8

9

33

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

450 500 550 600 650 700λ, нм

A(λ

), дБ

/м 7

6

5

4

8Fig. 26. γ-induced losses spectra of high-OH FVP300 fiber preliminary irradiated by neutrons fluence 1012 n·cm-2

a) UV-range;b) VIS-range.Doses: 105 (1), 5·105 (2), 106 (3, 4), 5·106 (5), 107 (6), 5·107 (7), 108 Rad (8).

0

20

40

60

80

100

120

140

200 250 300 350 400λ, нм

A(λ

), дБ

/м

4-1

3-1

2-10

10

20

30

40

50

60

70

200 250 300 350

A(λ

), дБ

/м

3

2

1

4

56

34

0

12

3

45

6

78

9

400 450 500 550 600 650 700λ, нм

A(λ

), дБ

/м

1

7

6

5

43

2

0

1

2

3

4

5

6

7

8

4 5 6 7 8lgD, Рад

A(λ

), дБ

/м

1

23

Fig. 27. γ-induced losses spectra of high-OH FVP300 fiber preliminary irradiated by neutrons fluence 1014 n·cm-2

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

Fig. 28. Kinetics of change of the value of A(λ) at 610 nm in(1) preliminary unirradiated.(2) preliminary irradiated by 1012 n·cm-2.(3) 1014 n·cm-2.

35

O Si H

γ

γ e-

e- e- γ

e+

e+

36

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

0

1

2

3

4

5

6

350 400 450 500 550 600 650 700λ, нм

Инд

уцир

ован

ные

поте

ри, д

Б/м

4

2

5

3

16

7

7

6

-0.1

0.1

0.3

0.5

0.7

0.9

1.1

1.3

350 400 450 500 550 600 650 700λ, нм

Инд

уцир

ован

ные

поте

ри, д

Б/м

8

9

8

9

10,11,12

13

13

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.

37

-0.3-0.2-0.1

00.10.20.3

0.40.50.6

300 350 400 450 500 550 600 650 700λ , nm

ΔA(λ

), дБ

/м1

12 2

-0.4

-0.2

0

0.2

0.4

0.6

0.8

300 350 400 450 500 550 600 650 700λ , nm

ΔA(λ

), дБ

/м

33

4

4

-0.5

0

0.5

1

1.5

2

2.5

300 350 400 450 500 550 600 650 700λ , nm

ΔA(λ

), дБ

/м 5

5

5

6

6

-0.1

0.1

0.3

0.5

0.7

0.9

1.1

300 350 400 450 500 550 600 650 700λ , nm

ΔA(λ

), дБ

/м 7

8

8

9 9

-0.2

-0.1

0

0.1

0.2

0.3

300 350 400 450 500 550 600 650 700λ , nm

ΔA(λ

), дБ

/м

10 1011

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;

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300 350 400 450 500 550 600t , C

K(λ

), от

н.ед

.

380nm 425nm

600nm 650nm0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300 350 400 450 500 550 600t , C

K(λ

), от

н.ед

.

360nm 450nm

550nm 400nm

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

38

39