EFDA
Association
Euratom-Belgium
European Fusion Development Agreement
Report on radiation effects on optical fibres at SCKCEN:
H2-loading, infrared-fibres and fibre current sensor
Nuclear Belgian Research Center
Boeretang, 200
2400 Mol Belgium
Benoît Brichard, Hans Ooms, Stan van
Ierschot, Jean Pouders, Stan Hendrieckx
Instrumentation Department
Tel: +32 14 33 26 40
Secr: +32 14 33 26 07
Fax: +32 14 31 19 93
bbrichar@sckcen.be
www.sckcen.be
Overview

Progress in on-going EFDA-IRRCER fibre-related tasks
Development & Irradiation testing of radiation-resistant fibres
TW5-TPDC/IRRCER-Deliverable 1 & 2
IR fibres for thermography application: gamma radiation-sensitivity
TW4-TPDC/IRRCER-Deliverable 16
fiber current sensor behaviour at cryogenic temperature
TW5-TPDC/IRRCER-Deliverable 9

New fibre optic technology for ITER: a proposal
2
Defects and imperfections cause photons to
be absorbed at specific wavelengths in fibres
Intrinsic spectral absorption in silica fibre
dB/km
104
UV
edge
Total intrinsic
optical absorption
IR phonon
absorption edge
Drawing
defects
l< 0.6 µm
Si-OH
> 10-2 dB/m
102
1.8 µm >
l > 1 µm
< 1x10-3 dB/m
Waveguide
imperfections
Rayleigh
scattering ~l-4
1
200
600
1000
1400
Wavelength [nm]
Radiation creates additional
or new defects
1800
2200
3
Radiation affects
the optical properties of silica

Radiation-Induced Absorption (RIA)
 Due to defect formations: E’,NBOHC,POR,STH,…

Radiation-Induced Luminescence (RIL)
 Due to Photoluminescence
 Due to Cherenkov effect in SiO2

Radiation-Induced Refractive Index Change
(RIRIC)
 Compaction-densification
 Colour centres
5
H2-treatment drastically reduces the 2 eV
RIA band formation in all type of fibres
Fission–reactor irradiation of High OH silica fibres
200 µm core – Acrylate coated
RIA in dB/m
12
KU1
80°C
12 MGy
8
2.7x1017 n/cm2
(E>0.1 MeV)
4
0
410
KU1 treated
with H2
500
600
700
800
900
Wavelength in nm
B. Brichard, A. L. Tomashuk & al., SCKCEN, J. of Nucl. Mat.,
329, p1456, 2004
6
H2 slows down the RIA growth at 600 nm while
OH content is enhanced at the same time
RIA [dB/m]
Low OH silica without H2
Low OH silica with H2
1.5
1.25
1.6 MGy
1.6 MGy
1
394 kGy
0.75
394 kGy
0.5
55 kGy
55 kGy
0.25
550 670 790
1030
0
1390
Wavelength [nm]
0.1 eV
 Si - O + H
2
550 670 790
1030
1390
Wavelength [nm]

  Si - OH + H 0 + 0.4 eV
7
At “low” dose the H2-STU fibre showed
the best radiation-resistance
RIA [dB/m]
5x1015 n/cm2 ; 200 kGy
10
330 Gy/s ; 60°C
Radiation-hardness
factor @ 600 nm
STU
RIA ( STU )
 10
RIA ( STU + H 2)
~3 MGy (pre-ionised)
SSU+H2
(600 µm)
5
KU1+H2
Ranking @ 600 nm
KSV4+H2
1. STU-200 µm
+ H2
OH growth
2. KS4V-200 µm
3. KU1-200 µm
4. SSU-600 µm
5. STU-200 µm
0
400
600
STU+H2
1000
1400
Wavelength [nm]
8
When the H2 is exhausted RIA quickly
re-increases
RIA [dB/m]
30
KU1+H2 and STU
7.12x1017 n/cm2
KS4V+H2
23 MGY
80°C
With these Al-coated H2- 15
loaded fibres we can enter
the cryostat but probably
not far into the diagnostic
block, unless we could
5
change the fibres.
STU
STU+H2
0
Looking for improvement ?
600
1000
1400
Wavelength [nm]
9
How to keep
H2 into the glass network ?
10
We follow two complementary but
different strategies


The previous results demonstrate the clear advantage of treating silica
optical fibres with hydrogen to improve the radiation resistance of the
optical transmission in the visible spectral region.
However, the optical transmission start degrading again as soon as the
hydrogen is exhausted.
Heavy H2 PRE-LOADING

Hermetic coating

300°C, 300 bars
This approach is currently
on-going in Troistk, Moscow
(cf collaboration EU/RF)
in-situ H2 RE-FUELING

Permeable coating

H2 filling-line
This approach is currently
under study at SCKCEN
(cf TW5-TPDC/IRRCER-Del 1 & 2)
11
SMIRNOF VI – irradiation device upgrade for
handling depleted-H2 atmosphere in reactor
In-pile capsule
Fibres are protected in
stainless steal tubes filled
with H2-depleted in
anaerobic atmosphere
Fibres
Thermocouples
• pressure 10-20 bars
• temperature max 100°C
• Continuous H2 flow
=> licensing OK for reactor test
12
A two step irradiation
Irradiation conditions in BR2-SIDONIE
irradiation channel at full power (56 MW)
Irradiation 2
40 %
Neutron flux: 1.7x1014 n/cm2s
Epithermal flux: 4.6x1013 n/cm2s
Fast neutron flux (>1 Mev): 1.9x1013
Irradiation 1
10 %
n/cm2s
2h
Gamma Heating: 3 W/g[Al]
time
2h
neutron
(~ 1 MeV):
gamma
2h
1.5 1016 n/cm2
: 2.2 MGy
neutron
(~ 1 MeV):
gamma
5.7 1016 n/cm2
: 11 MGy
13
Overview

Progress in on-going EFDA-IRRCER fibre-related tasks
Development & Irradiation testing of radiation-resistant fibres
TW5-TPDC/IRRCER-Deliverable 1 & 2
IR fibres for thermography application: gamma radiation-sensitivity
TW4-TPDC/IRRCER-Deliverable 16
fiber current sensor behaviour at cryogenic temperature
TW5-TPDC/IRRCER-Deliverable 9

New fibre optic technology for ITER: a proposal
14
Divertor thermography with IR fibres
Divertor Cassette is a high
temperature
region
to
be
continuously
monitored
for
machine protection
IR thermography
proposed by CEACadarache Tore-Supra
IR fibre ?
Divertor Cassette
15
IR-Fibres could be used to transport IR
radiation from the divertor port to the bioshield
Line of Sight

Low OH Silica

Sapphire


ZrF4


Up to 250°C
Up to 150°C
1-11 µm
Low NA
PBG fibres / Bragg Fibres

mirrors
1-4 µm
Metal-coated fibres 3-17 µm


1-3.5 µm
Chalcogenide


max 3 m
1-2 µm
???
Fibres
At the divertor port
Cassegrain
~1019 n/cm2 (E>0.1 MeV)
Telescope
~ 1 Gy/s ; >10 MGy
• 8.5 m up to Bioshield
• Large Wavelength Span
16
Experimental set up to measure on-line
radiation-induced absorption in IR fibres
Fibre
Lock-in
IR Spectrometer
Lamp
RITA
Irradiation
container
Labview DAQ
CEA Acquisition (R. Reichle)
17
Radiation sensitivity depends on the wavelength
and type of “fluoride” compound material used
5.2 kGy
RIA
decreases
with
increasing wavelength
RIA in dB/m
RIA
dB/m
4
3
3 kGy
3 kGy
IR2
3
2 µm
2
3.5 µm
1
2
IR1
3.5 µm
0
recovery
0.0
1
4.0x104
recovery
8.0x104
1.2x105
1.6x105
Time in hours
IR1- Zirconiumfluoride
Recovery ~17 h
0
1500
2 µm
2000
2500
IR2- Hafniumfluoride
3000
Wavelength in nm
3500
4000
18
Similar RIA in ZrF4 fibre from other
manufacturer.
3 kGy
Zirconium Fluoride
(RA6) - Polymicro
2.0
RIA dB/m
120
5.2 kGy
100
1.5
80
2 µm
1.0
60
0.5
40
Recovery
Temperature
increase
favours RIA decrease.
0.0
4
-5.0x10
0.0
4
5
5
5
5
5
Temperature C°
2.5
20
5
5.0x10 1.0x10 1.5x10 2.0x10 2.5x10 3.0x10 3.5x10
Time in seconds
19
Hollow Waveguide Fibre: good radiation
resistance but extremely sensitive to bending
Hollow Waveguide: 750 µm core – 2 meters
Hollow Waveguide
From Polymicro
Transmission spectrum
0.0004
0.0003
0.0002
0.0001
0.0000
0
1000
2000
3000
4000
5000
Wavelength [nm]
No change observed after 27 kGy !
20
Preliminary Conlusion on IR fibres

For 1-2 µm, low-OH pure silica is a good candidate.
However, we need more data on neutron damage at 2 µm

Above 2 µm,
Zirconium/ Hafnium Fibre much more radiation-sensitive
than silica

Hollow-Waveguide, good candidate but high-intrinsic loss
and difficult to handle


Still to test Saphirre Fibre (and Chalcogenide ?)

Also looking for PBG (Bragg) silica fibre operating in 2-3 µm
21
Overview

Progress in on-going EFDA-IRRCER fibre-related tasks
Development & Irradiation testing of radiation-resistant fibres
TW5-TPDC/IRRCER-Deliverable 1 & 2
IR fibres for thermography application: gamma radiation-sensitivity
TW4-TPDC/IRRCER-Deliverable 16
fiber current sensor behaviour at cryogenic temperature
TW5-TPDC/IRRCER-Deliverable 9

New fibre optic technology for ITER: a proposal
22
Optical Fiber Current sensor in ITER ?
Conventional plasma current measurement system like Rogowski coils
looses sensitivity in quasi steady state plasma
Interest for Fibre Current Sensor ?
Faraday Effect
Need to assess the influence of
radiation and low temperature
on the Verdet Constant
Magnetic Field rotates the incident
polarization
state
by
an
amount
proportional to the Verdet Constant µV.
23
Few publications talking about Fibre current
sensor in TOKAMAK and …
S. Kasai, I. Sone, M. Abe, T. Nishitani, S. Tanaka, T. Yagi, N. Yokoo and
S. Yamamoto, On-line Irradiation Tests on Sensing Fiber of Optical-fiber
Current Transformer, JAERI-Research 2002-007, p130-144

N.M. Kozhevnikov, Y. Barmenkov, V.A. Belyakov, A. Medvedev, G.
Razdobarin, Fiber-optic sensor for plasma current diagnostic in
tokamaks, SPIE vol. 1584 Fiber Optic and Lasers IX (1991), p 138-144

Y. Barmenkov, F. Mendoza-Santoyo, Faraday plasma current sensor with
compensation for reciprocal birefringence induced by mechanical
perturbations, J. Appl. Research and Technology, Vol 1, No2, 2003, p157163

Commercially Available System exists
for electrical power industry

In the US, NxtPhase : http://www.nxtphase.com

In Switzerland, ABB, Baden-Dättwil CH-5405,
K.Bohnert, optics and lasers in Engineering, 43 (2005), 511-526
24
The fibre current performance will depend on
wavelengths, temperature and radiation…
Verdet constant in silica as
function of wavelengths
Faraday Effect
as l
We prefer to operate the fibre
current
sensor
in
the
low
sensitivity region, i.e. 1.3-1.5 µm,
because at these wavelengths:

we reduce the combined effect of
radiation and low temperature

we can more easily use an allfibre optic sensor system
A.H. Rose, JLT, Vol 15,n°5,1997
25
No data on Verdet Constant in Liquid
Nitrogen…
Mini-ITER
Fibre
Current
Source
Light
Source
Polarisation
controller
Liquid
Nitrogen
26
Fiber current sensitivity slightly decreases when
subjected to liquid nitrogen temperature
300 K
I = 40 A
=>
DOP ~ 3%
+I
0
5
10
15
Time in seconds
20
25
-I
30
35
Cryogenic Temperature
induces
•decrease in sensitivity
•additional noise
- 77 K
I = 40 A
=>
DOP ~ 2%
27
Preliminary conclusion on fibre
current sensor
Preliminary result is encouraging


At liquid nitrogen temperature we observed a slight
decrease of the fibre sensitivity with an increase of
the noise in the measure => need optimizatiion
Need to verify now
 the RIA of the fibre at 1.5 µm at -77K
 if
the radiation could degrade the
constant
Verdet
28
Overview

Progress in on-going EFDA-IRRCER fibre-related tasks
Development & Irradiation testing of radiation-resistant fibres
TW5-TPDC/IRRCER-Deliverable 1 & 2
IR fibres for thermography application: gamma radiation-sensitivity
TW4-TPDC/IRRCER-Deliverable 16
fiber current sensor behaviour at cryogenic temperature
TW5-TPDC/IRRCER-Deliverable 9

New fibre optic technology for ITER: a proposal
29
New fibre optic technology for
ITER ?
30
Photonic Crystal Fibres can be classified in
two different families
I. High Index Guiding Fibers - HICF




II. High Index Guiding Fibers - LICF


Light is guided in a solid core with
higher refractive index than cladding
Strong wavelength dependence of
the effective refractive index
Low intrinsic absorption
 1.5 dB/km @ 1550 nm
 30 dB/km @ 500 nm
High NA > 0.6
Due to the Band Gap feature, light is
exclusively guided into a hollow core
characterised by low index
Low intrinsic absorption is now
available
 0.1 dB/m @ 1550 nm
 1 dB/m @ 500 nm
31
Radiation induces Photo and Radio
Luminescence in silica based material
Function of fibre diameter
Luminescence in 200 µm core fibre
dB
600 µm
200 µm
600
Light intensity @
detector side [pW]
Cherenkov and Photoluminescence
Function of reactor power
Photoluminescence (O2)
80 %
0.1 nW level at detector side
Cerenkov
RIA
Wavelength [nm]
800
1200
60 %
40 %
20 %
Reactor Time
Wavelength [nm]
32
High-Index Core Fibres (HICF) should reduce
Cherenkov yield while holding good light coupling
With HICF we can reduce the fibre diameter
while increasing the numerical aperture
Cerenkov Yield
Y ~ D2
Coupled Power
P ~ D2
NA2
In addition holes provide a way to inject efficiently hydrogen to
“repair” the fibre transmission
Cf results of A.L. Tomashuk
(
F
O
R
C
)
33
Fibres might simplify design and maintenance
in many diagnostic …
• Small and compact space
• PMTs suffer Radiation and EMI
=> Move away PMTs and Use fibres
Liquid Scintillators response
Lower Vertical Neutron Camera -LVNC
10 collimators ;  35 mm
After D. Marocco, ENEA
34
Conclusion, perspectives and expectations

R&D work will carry on …



Hydrogen-loading technique with engineering
emphasis
Outlook to new fibre technology, like Photonic
Crystal Fibres…
Now, real need to interact with designers
to implement fibre pathways in ITER
35