Application of quartz glass, polyimide optical fiber sensors and crystal detectors to measurement of charged-particles, gamma and neutron dose in tokamak

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Application of quartz glass, polyimide optical
fiber sensors and crystal detectors to
measurement of charged-particles, gamma and
neutron dose in tokamak Group content Prof.
P.S. dr hab. Inz. S.M. Kaczmarek Prof. dr hab.
Ewa Weinert-Raczka Prof. Dr Arlen Valozhyn
(polyimides) Dr Hubert Fuks Dr Danuta
Piwowarska Dr Jerzy Gajda Mgr Adam
Worsztynowicz Mgr Grzegorz Leniec Partners MOL
group Espany group
Abstract. New optical fibre sensors of ionizing
radiation are proposed build of quartz glass and
polyimides with higher glass temperature limit
and the testing of the materials under high flux
irradiation with 14 MeV neutrons. Also classical
sensors (strain, temperature) build of quartz
glass we are going to test for their radiation
hardness. Moreover, some kinds of other crystal
detectors of the temperature, charge particles,
gammas and neutrons will be produced,
investigated and tested (e.g. Li2B4O7,
SrxBa1-xNb2O6)

• Main goals
• Processing and investigation of nonlinear optical
• materials
• Li2B4O7 as SHG, 4HG, 5HG
• SrxBa1-xNb2O6 - pyroelectric
• High glass transition temperature polyimides
• 2. Neutron SS scintillators based on Li2B4O7
• 3. Fiber optical neutron and gamma sensors

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Neutrons are always detected through nuclear
reactions that create charged particles. Slow-
and fast- neutron detectors contain conversion
materials that react to incident neutrons by
generating charged particles. The materials used
for this purpose (a fill gas, coating, foil,
etc.) are stable isotopes having a high
efficiency of conversion for the given type of
radiation. The produced charges are detected by
transduction elements having structures similar
to those used for a-, b-, or g-radiation. The
representative conversion materials for
slow-neutron detection are isotopes 6Li and 10B,
and, for fast- neutron detection, 3H and 6LiF.
Slow- and fast-neutron detectors. SN and FN
slow-and fast-neutron radiation, 1 conversion
material, 2 transduction element for a, b-, or
g-radiation, 3 case.
Sensing/Interaction Mechanisms Fundamental
mechanisms and interactions that allow detection
and measurement of nuclear/ionizing radiation
(e.g., free carrier generation in materials,
optical scintillation, optically active defect
creation in detectors, etc.).
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Neutron Detectors

• What does it mean to detect a neutron?
• Need to produce some sort of measurable
  quantitative (countable) electrical signal
• Cant directly detect slow neutrons
• Need to use nuclear reactions to convert
  neutrons into charged particles
• Then we can use one of the many types of charged
  particle detectors
• Gas filled proportional counters, 3He, BF3, H3BO3
  and ionization chambers efficient for thermal
  neutrons (0.025eV)
• Scintillation detectors, Li glass (Ce), LiF (Eu),
  ZnS (Ag) LiF, YAPCe
• Semiconductor detectors

• n 3He ? 3H 1H 0.764 MeV
• n 6Li ? 4He 3H 4.79 MeV
• n 10B ? 7Li 4He?7Li 4He 0.48 MeV ? 2.3
  MeV (93)? 7Li 4He 2.8 MeV ( 7) -
  10B(n,a)7Li
• n 155Gd ? Gd ? ?-ray spectrum ? conversion
  electron spectrum
• n 157Gd ? Gd ? ?-ray spectrum ? conversion
  electron spectrum
• n 235U ? fission fragments 160 MeV
• n 239Pu ? fission fragments 160 MeV
• Detection efficiency

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Scintillation fiber detector develped by the Los
Alamos National Laboratory
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More recently, neutron detectors based on 6LiF
converters (LiF, Li2O, Li6Gd(BO3)3 ) and silicon
semiconductor diodes have been tested. The
principle of this kind of neutron detection is
completely different from the method used with
scintillation detectorsThermal or sub-thermal
neutrons are absorbed in a thin 6LiF converter.
The reaction products reach the semiconductor and
generate electron hole pairs. On average half of
the kinetic energy of the reaction product 3H is
deposited in the depletion region of the silicon
diode since the converter has a thickness of 16µm
and the range of the 3H particle is 32µm. Under
construction are such one- and two-dimensional
detectors for slow neutrons for evaluating
detector properties. With this detector type a
high spatial resolution of e.g. 100µm is
achievable. The detector is insensitive to
varying magnetic fields, in contrast to a
detector based on photomultipliers. For two
dimensional detectors each x and y strip on the
diode needs its own amplifier chain in order to
determine the position of incidence.
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Nuclear Track Detectors were mounted with the
boron converter on their surface as one
compres-sed unit to assess accumulated low doses
of thermal neutrons around neutron source storage
area. The converter is a lithium tetraborate
(Li2B4O7) layer for thermal neutron detection via
10B(n,alpha)7Li and 6Li(n,alpha)3H nuclear
reactions. The study indicates that the area
passive neutron dosimeter was able to detect
accumulated doses as low as 40 nSv x h(-1), which
could not be detected with the available active
neutron dosimeters.
Li2B4O7 neutron scintillator
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Optoelectronic Head IF SUT dr hab. inz. Prof.
PS - Slawomir M. Kaczmarek
1. Scintillators
Scintillator materials made up in SUT BGO
master scintillator material. SUT K05002 pixel
(2210 mm) horizontally LYhor 828
phe/MeV vertically LYver 404 phe/MeV resolution
R0 8.59 Light yield LY0 1084
phe/MeV Absorption coefficient m 1.16 cm-1 PML
BGO Photonic Materials N13363-8 pixel (2210
mm) horizontally LYhor 847 phe/MeV vertically
LYver 471 phe/MeV Light yield LY0 1057
phe/MeV !!! (bravo SUT!!!) Absorption coefficient
m 0.90 cm-1 (tym oni góruja) dr Winicjusz
Drozdowski, Zaklad Optoelektroniki, Uniwersytet
im. M. Kopernika, Torun
Metoda Czochralskiego
BGO
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2. Nonlinear single crystals
Langesites LGT, LGTYb, Ho, LGTCo
Lithium tetraborate LBO, LBOCo, LBOMn
SHG of NdYVO laser4 (1.06 mm) with efficiency
gt30 3318 mm made up from nonlinear Li2B4O7
1. D. Piwowarska, S.M. Kaczmarek, W. Drozdowski,
M. Berkowski, A. Worsztynowicz, "Growth
and optical properties of Li2B4O7 single crystals
pure and doped with Yb, Co, Eu and Mn ions for
nonlinear applications", Acta Phys. Pol. A, 107
(2005) 507-516 2. R. Wyrobek, Przetwornik na
wyzsze harmoniczne lasera NdYAG na bazie
Li2B4O7, praca magisterska, promotor
S.M.Kaczmarek 3. B. Felusiak, Liniowe i
nieliniowe wlasciwosci dielektryczne
monokrysztalów Li2B4O7, praca magisterska,
promotor S.M. Kaczmarek 4. D. Piwowarska,
Dissertation, Szczecin 2005, promotor S.M.
Kaczmarek 5. D. Piwowarska, S.M. Kaczmarek, M.
Berkowski, I. Stefaniuk, Growth and EPR and
optical properties of Li2B4O7 single crystals
doped with Co2 ions, J. Cryst. Growth, in the
print
Nonlinear single crystal SrxBa1-xNb2O6 Cr
fotorefractive material, relaksor Holographic
imaging, piezotechnic, nonlinear optics (mixing
of wavelengths)
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• 3. Second order non-linear optical polymers,
  polyimides
• Prof. Volozhyn
• Advantage over LiNbO3
• - large second-order NLO properties d3330 pm/V
  for 1320 nm
• - high laser damage threshold
• - ease of processing and modification
• - have good film-forming properties for making
  waveguide structures
• - are compatible with existing semiconductor
  technologies
• - increasing the Tg (200-275oC) results in an
  improved poled-order stability (stability SHG)
  168oC for gt1000h
• Applications
• high-speed light modulators and switches

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First goal of our project Producing of
nonlinear optical materials for 2HG, 4HG and 5HG
Li2B4O7 and SrxBa1-xNb2O6. Investigation of
nonlinear and linear optical properties of the
crystals and the influence of neutron and gamma
radiation on the properties Producing of
nonlinear polyimides for 2HG, modulators,
switches. Investigation of nonlinear and linear
optical properties of the polymer and the
influence of neutron and gammas on the properties
Second goal of our project Producing of Li2B4O7
neutron scintillators checking of the influence
of different kind of doping on the scintillation
properties, Investigation of the influence of
neutrons and gammas on the properties of the
crystals
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Lithium Doped Glass Fiber Scintillators
The optical diagnostic system of future fusion
reactors must operate in high temperature and a
severe radiation environment. The use of optical
fibers is expected to significantly simplify the
design of such a system.

• Vehicle or helicopter mounted arrays of gamma ray
  and/or neutron detectors
• Usually contain large NaI(Tl) scintillator
  crystals and large 3He or BF3 neutron
  proportional counters
• May be combined with GPS and mapping software

Fiber Optic Neutron Detectors
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Crossed-Fiber Position-Sensitive Scintillation
Detector. All fibers installed and connected to
multi-anode photomultiplier mount

• Size 25-cm x 25-cm
• Thickness 2-mm
• Number of fibers 48 for each axis
• Multi-anode photomultiplier tube Phillips XP1704
• Coincidence tube Hamamastu 1924
• Resolution lt 5-mm
• Shaping time 300 nsec
• Count rate capability 1 MHz
• Time-of-Flight Resolution 1 msec

The scintillator screen for this 2-D detector
consists of a mixture of 6LiF and
silver-activated ZnS powder in an epoxy binder.
Neutrons incident on the screen react with the
6Li to produce a triton and an alpha particle.
Collisions with these charged particles cause the
ZnS(Ag) to scintillate at a wavelength of
approximately 450 nm. The 450 nm photons are
absorbed in the wavelength-shifting fibers where
they converted to 520 nm photons emitted in modes
that propagate out the ends of the fibers. The
optimum mass ratio of 6LiFZnS(Ag) was
determined to be 13. The screen is made by
mixing the powders with uncured epoxy and pouring
the mix into a mold. The powder then settles to
the bottom of the mold before the binder cures.
After curing the clear epoxy above the settled
powder mix is removed by machining. A mixture
containing 40 mg/cm2 of 6LiF and 120 mg/cm2 of
ZnS(Ag) is used in this screen design. This
mixture has a measured neutron conversion
efficiency of over 90.
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Fiber-optic Strain and Temperature Sensors based
on extrinsic Fabry-Perot interferometer The
interfering reflections are created outside the
fiber instead of internally and refractory
ceramic construction. Sensors are needed that can
operate at temperatures gt1000 oC for the control
and monitoring of high temperature systems such
as nuclear reactors. Advantages immunity to
electromagnetic interference, extremely long lead
lengths, a high level of multiplexing, and
extremely low mass. The transducing mechanism
used is a distance measurement technique based on
the formation of a Fabry-Perot cavity between the
polished end face of an optical fiber and a
reflective surface. Light is emitted from a
broadband source, transmitted through a coupler,
and passed through the fiber at the sensor, where
a portion of the light is reflected off the fiber
end face reference reflection (R1). The
remaining light propagates through the transducer
and is reflected back into the fiber sensing
reflection. These two light waves interfere
constructively or destructively. The resulting
interference pattern is interpreted in term of
absolute gap between the two reflectors. The
physical quantity measured is the optical path
length between R1 and R2.
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1 - Recoil protons polymer 2 diffusion of
hydrogen 3 compaction effect
Fiber optic neutron sensors
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Fiber optic gamma sensor
When pure quartz glasses are irradiated with e.g.
g-radiation, absorption bands with maxima at 4.8,
2 eV and 1.75 eV are formed. The absorption bands
are caused by centers formed by nonbridging
oxygen Si-O-. Irradiation of some glasses and
crystals with neutrons reveals the presence of
very similar bands (UVVIS). There is known a
proposition of use a differential circuit for the
sensor build of quartz glass for g-irradiation
detection. Laser radiation with 215 nm
(absorption maximum of the material) is
introduced into the optical fiber, after which
the fiber is separated into two fibers of
identical length, fabricated from a single
material. One of the fibers is placed in the
medium where the irradiation dose needs to be
measured, and the second remains under normal
conditions. Photodiodes that record the intensity
of the transmitted radiation are placed at the
output of both fibers. The radiation intensity in
a fiber acted on by irradiation (gamma) will be
smaller because of induced absorption
(proportional to radiation dose). The intensity
in the fiber that remains under normal conditions
is taken as the reference level. It is proposed
that the returning of irradiated fiber to initial
state will be possible due to cladding made from
a metal network (electric current), that will
heat the fiber above 200 oC.
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3. Analyzis of color centers in fluorides CaF2,
LiLuF4, LiYF4, BaY2F8, KY3F10 doped with Yb3
1. S.M. Kaczmarek, A. Bensalah, G. Boulon, "G-ray
induced color centers in pure and Yb doped LiYF4
and LiLuF4 single crystals, Optical Materials,
28/1-2 (2006) 123-128 (1.339) 2. S.M. Kaczmarek,
T. Tsuboi, M. Ito, G. Boulon, G. Leniec, "Optical
study of Yb3/Yb2 conversion in CaF2 crystals",
Journal of Physics Condensed Matter, 17 (2005)
3771-3786 (2.049) 3. G. Leniec, S.M. Kaczmarek,
G. Boulon, "EPR and optical properties of CaF2Yb
single crystals", Proc. SPIE, vol. 5958 (2005),
pp. 531-540
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Influence of the annealing and g-irradiation on
the absorption of YAGNd 1 crystal
WTW WAT
ICHTJ
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Influence of the annealing and irradiation with
protons of 20 MeV energy (cyclotron) and
electrons (acceler.) of 1 MeV energy on the
absorption of YAGNd 1 crystal
IPJ Swierk
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Third goal of our project Producing of the
fiber optic neutron and gamma sensors based on
quartz glass and polyimides. Investigation of the
influence of gamma and neutron doses on the
properties of the sensors
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• NEW KNOWLEDGE EXPECTED FROM THE PROJECT
• - more detailed data on charged particle, gamma
  and neutron emission,
• - extended knowledge concerning physical
  phenomena in larger tokamak facilities as a
  result of implementation of the proposed charged
  particle, gamma and neutron detectors,
• improvement of technology in the range of
  important subject concerning the application of
  new kind of optical fiber sensors based on
  polyimides and high quality crystals for neutron
  detection.
• It is assumed that the first steps will be a
  better recognition of the demands for charged
  particles, gammas and neutrons diagnostics at
  tokamak, gaining the knowledge about the
  technical details concerning implementation of
  the diagnostics in real experimental conditions
  and then choosing the best suitable detectors
  (optical fiber sensors and crystals). Then the
  irradiation of the strain, temperature and
  radiation optical fiber and crystal sensors with
  different kinds of radiation using especially 14
  MeV neutrons and measuring and recognizing of the
  induced effects. Parallel we are going to
  investigate samples produced from the crystal and
  glasses materials for their changes under charge
  particles, gammas and neutron radiation.
• After drawing conclusion from the first tests and
  analyzing the real needs in detail the improved
  detectors will be designed and fabricated and the
  next experimental session will be carried on.
  Simultaneously, the improving works with the main
  goal of obtaining the possible great spectral
  resolution will be carried on.

WORK PLAN The realization of the whole project is
planned for three years and the tasks will be
scheduled as follows The first year getting in
touch with the laboratories dealing with the
spectrometry of the fusion charged particles,
gammas and neutrons, choosing the proper
detectors for spectrometry, recognition the
problems connected with fabrication of polyimide
optical fiber and crystal detectors, finding
suitable materials (doping appropriately to the
kind of radiation) for the detectors (sensors).
The second year organization of the first
experimental session at tokamak, testing
different detectors, fabrication the improved
versions of optical fiber detectors. The third
year testing the improved version of the
improved polyimide optical fibre detectors
(sensors), diagnosing plasmas with the use of the
matrix detectors.