Transcript Investigations on Applicability of Dielectric Mirrors for ITER

Investigations on Applicability
of Dielectric Mirrors for ITER
Ilya Orlovskiy, Konstantin Vukolov
10th ITPA Meeting Group, Moscow, Russia
Motivation
Multilayered dielectric mirrors could significantly improve light
transmission from plasma to detectors if used as the secondary mirrors for
optical diagnostics (CXRS, MSE, H-Alpha etc). However, diagnostic
elements in ITER will be exposed to significant neutron fluencies and
thermal load.
Calculated conditions for H-Alpha secondary mirrors in ITER
3rd mirror
4th mirror
Neutron flux*
2.2·1012 n/cm2s
4.7·1010 n/cm2s
Fluence (1 year**)
1.1·1019 n/cm2
2.4·1017 n/cm2
Temperature***
150 – 250ºC
150 – 250ºC
* Neutrons with energy more than 0.1 MeV
** 1000 shots of 500 seconds each, D-T operation
*** Will be provided by the cooling system in ITER
Samples 2003-2004
Label
Working
range, nm
PT#
Coating
Materials
Number
of layers
Manufacturer
590 – 740
TiO2 / SiO2
13
PZ#
590 – 670
ZrO2 / SiO2
15
“Luch”, Podolsk,
Russia
LT#
550 – 650
TiO2 / SiO2
17
LZ#
640 – 740
ZrO2 / SiO2
23
“LOGF”,
Lytkarino,
Russia
Low refraction
material
(SiO2)
Substrate
(SiO2 – KS-4V)
25 mm
at
different
wavelengths
depending on material and number
of layers.
alternating layers of TiO2/SiO2
and ZrO2/SiO2 on silica glass
substrate.
100
Specular reflectance, %
Reflectance of the samples reaches
99%
The samples were made of
2 mm ~0.002 mm
High refraction
material
(TiO2 or ZrO2)
PT
PZ
LT
LZ
80
60
40
20
0
400
500
600
700
800
wavelength, nm
900
1000
Heating in vacuum 2003-2004
Heating regime
“LOGF” samples after the heating
Temperature, C
300
250
200
150
100
50
0
0
1
2
3
4
5
Time, hours
Reflectance before and after the heating
Specular reflectance, %
100
80
The coatings of the “LOGF” samples
were damaged.
before
after
60
40
20
0
450
550
650
750
wavelength, nm
850
Working range of “Luch” samples
was
shifted
towards
short
wavelengths.
The
coatings
remained undamaged.
Neutron Irradiation
Reflectance before and after the
irradiation
0.020
0.015
0.010
0.005
0.000
0.1
1
Energy, MeV
10
Specular reflectance, %
Neutron flux, n*cm/s
2
Neutron spectrum in the
active zone of IR-8 reactor
100
before
after
80
60
40
20
0
400
500
600
700
800
900
1000
wavelength, nm
The coatings of the samples irradiated to 1019 n/cm2 remained undamaged.
The working range shifted slightly towards short wavelengths.
Specular reflrctance, %
Samples 2005-2006
100
80
60
40
20
0
200
400
600
800
1000
wavelength, nm
#
Sample
1
LF
2
LG
3
SF
4
SG
Working
range
Coating
Substrate
Fused silica KU-1
400-670 nm
TiO2/SiO2
Silica glass K-8
23 layers
Fused silica KU-1
Silica glass K-8
Size
100x10 mm
25x2 mm
Heating in vacuum 2006
Regime #1
Regime #2
Temperature, °C
300
250
200
150
100
50
0
00
02
04
06
08
10
12
Specular reflrctance, %
Time, hours
Initial
Heating 1
Heating 2
100
95
The coatings of all the samples
remained undamaged. The spectra of
both large and small samples show the
same behavior.
The working range shifted towards long
wavelengths.
The reflectance in the flat range
reduced from 98% down to 96%.
90
85
80
400
The samples were heated in vacuum
oven in two regimes under 103 Pa. The
heating in regime #1 was followed by
the heating in regime #2.
500
600
700
wavelength, nm
800
The reflectance in the negative peaks
reduced down to 80%.
Conclusions
• Thermal loads assumingly play the main role in damaging
of mirror coating, at least under tested fluences.
• Multilayered dielectric mirrors can sustain neutron fluences
and temperatures expected for secondary mirrors in ITER.
Presently, manufactures are able to provide sufficient
adhesion of coating to substrate for the mirrors of a large
size.
• Working range of dielectric mirrors can be shifted slightly
being exposed to the temperatures up to 250°C. Shift
direction depends on the coating.
• Heating can reduce the reflectance of dielectric mirrors,
especially in negative peaks of the spectrum.
Further plans
• Continuation of heating tests to find the limits of
reflectance degradation.
• Design and production of prototypes of dielectric mirrors
for H-alpha and CXRS diagnostics.
• Testing the prototypes in vacuum oven and nuclear
reactor.
• Developing specifications for production of diagnostic
mirrors for ITER.