1. 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. Inż. S.M. Kaczmarek Prof. dr hab. Ewa Weinert-Rączka 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 Main goals Processing and investigation of nonlinear optical materials: -Li 2 B 4 O 7 as SHG, 4HG, 5HG -Sr x Ba 1-x Nb 2 O 6 - pyroelectric -High glass transition temperature polyimides 2. Neutron SS scintillators based on Li 2 B 4 O 7 3. Fiber optical neutron and gamma sensors 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. Li 2 B 4 O 7, Sr x Ba 1-x Nb 2 O 6 )

2. Optoelektronika i fizyka materiałowa2 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, -, or - radiation. The representative conversion materials for slow-neutron detection are isotopes 6 Li and 10 B, and, for fast- neutron detection, 3 H and 6 LiF. Slow- and fast-neutron detectors. SN and FN = slow-and fast-neutron radiation, 1 = conversion material, 2 = transduction element for -, or -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.).

3. Optoelektronika i fizyka materiałowa3 Neutron Detectors What does it mean to detect a neutron? 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 Need to use nuclear reactions to convert neutrons into charged particles Then we can use one of the many types of charged particle detectors Then we can use one of the many types of charged particle detectors –Gas filled proportional counters, 3 He, BF 3, H 3 BO 3 and ionization chambers – efficient for thermal neutrons (0.025eV) –Scintillation detectors, Li glass (Ce), LiF (Eu), ZnS (Ag) – LiF, YAP:Ce –Semiconductor detectors n + 3 He 3 H + 1 H + 0.764 MeV n + 3 He 3 H + 1 H + 0.764 MeV n + 6 Li 4 He + 3 H + 4.79 MeV n + 6 Li 4 He + 3 H + 4.79 MeV n + 10 B 7 Li* + 4 He 7 Li + 4 He + 0.48 MeV +2.3 MeV (93%) 7 Li + 4 He +2.8 MeV ( 7%) - 10 B(n, ) 7 Li n + 10 B 7 Li* + 4 He 7 Li + 4 He + 0.48 MeV +2.3 MeV (93%) 7 Li + 4 He +2.8 MeV ( 7%) - 10 B(n, ) 7 Li n + 155 Gd Gd* -ray spectrum conversion electron spectrum n + 155 Gd Gd* -ray spectrum conversion electron spectrum n + 157 Gd Gd* -ray spectrum conversion electron spectrum n + 157 Gd Gd* -ray spectrum conversion electron spectrum n + 235 U fission fragments + ~160 MeV n + 235 U fission fragments + ~160 MeV n + 239 Pu fission fragments + ~160 MeV n + 239 Pu fission fragments + ~160 MeV Detection efficiency Detection efficiency

4. Optoelektronika i fizyka materiałowa4 Scintillation fiber detector develped by the Los Alamos National LaboratoryLos Alamos National Laboratory

5. Optoelektronika i fizyka materiałowa5 More recently, neutron detectors based on 6 LiF converters (LiF, Li 2 O, Li 6 Gd(BO 3 ) 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 detectors: Thermal or sub-thermal neutrons are absorbed in a thin 6 LiF converter. The reaction products reach the semiconductor and generate electron hole pairs. On average half of the kinetic energy of the reaction product 3 H is deposited in the depletion region of the silicon diode since the converter has a thickness of 16µm and the range of the 3 H 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.

6. Optoelektronika i fizyka materiałowa6 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 (Li 2 B 4 O 7 ) layer for thermal neutron detection via 10 B(n,alpha) 7 Li and 6 Li(n,alpha) 3 H 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. Li 2 B 4 O 7 neutronscintillator

7. Optoelektronika i fizyka materiałowa7 Optoelectronic Head IF SUT dr hab. inż. Prof. PS - Sławomir M. Kaczmarek dr hab. inż. Prof. PS - Sławomir M. Kaczmarek Scintillator materials made up in SUT: BGO – master scintillator material. SUT K05002 pixel (2*2*10 mm): horizontally LY hor = 828 phe/MeV vertically LY ver = 404 phe/MeV resolution R 0 = 8.59 % Light yield LY 0 = 1084 phe/MeV Absorption coefficient = 1.16 cm -1 PML BGO Photonic Materials N13363-8 pixel (2*2*10 mm): horizontally LY hor = 847 phe/MeV vertically LY ver = 471 phe/MeV Light yield LY 0 = 1057 phe/MeV !!! (bravo SUT!!!) Absorption coefficient = 0.90 cm -1 (tym oni górują) dr Winicjusz Drozdowski, Zakład Optoelektroniki, Uniwersytet im. M. Kopernika, Toruń BGO 1. Scintillators MetodaCzochralskiego

8. Optoelektronika i fizyka materiałowa8

9. 9 SHG of Nd:YVO laser 4 (1.06 m) with efficiency >30% : 3*3*18 mm made up from nonlinear Li 2 B 4 O 7 Nonlinear single crystal Sr x Ba 1-x Nb 2 O 6 : Cr – fotorefractive material, relaksor: Holographic imaging, piezotechnic, nonlinear optics (mixing of wavelengths) Langesites: LGT, LGT:Yb, Ho, LGT:Co Lithium tetraborate: LBO, LBO:Co, LBO:Mn 2. Nonlinear single crystals 1. D. Piwowarska, S.M. Kaczmarek, W. Drozdowski, M. Berkowski, A. Worsztynowicz, "Growth and optical properties of Li 2 B 4 O 7 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 wyższe harmoniczne lasera Nd:YAG na bazie Li 2 B 4 O 7, praca magisterska, promotor S.M.Kaczmarek 3. B. Felusiak, Liniowe i nieliniowe właściwości dielektryczne monokryształów Li 2 B 4 O 7, 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 Li 2 B 4 O 7 single crystals doped with Co 2+ ions, J. Cryst. Growth, in the print

10. Optoelektronika i fizyka materiałowa10 3. Second order non-linear optical polymers, polyimides Prof. Volozhyn Advantage over LiNbO 3 : - large second-order NLO properties: d 33 =30 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 T g (200-275 o C) results in an improved poled-order stability (stability SHG) 168 oC for >1000h Applications -high-speed light modulators and switches

11. Optoelektronika i fizyka materiałowa11 First goal of our project: Producing of nonlinear optical materials for 2HG, 4HG and 5HG – Li 2 B 4 O 7 and Sr x Ba 1-x Nb 2 O 6. 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 Li 2 B 4 O 7 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

12. Optoelektronika i fizyka materiałowa12 Lithium Doped Glass Fiber Scintillators Vehicle or helicopter mounted arrays of gamma ray and/or neutron detectors Vehicle or helicopter mounted arrays of gamma ray and/or neutron detectors –Usually contain large NaI(Tl) scintillator crystals and large 3 He or BF 3 neutron proportional counters –May be combined with GPS and mapping software Fiber Optic Neutron Detectors 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.

13. Optoelektronika i fizyka materiałowa13 Crossed-Fiber Position-Sensitive Scintillation Detector. All fibers installed and connected to multi-anode photomultiplier mount Size: 25-cm x 25-cm Size: 25-cm x 25-cm Thickness: 2-mm Thickness: 2-mm Number of fibers: 48 for each axis Number of fibers: 48 for each axis Multi-anode photomultiplier tube: Phillips XP1704 Multi-anode photomultiplier tube: Phillips XP1704 Coincidence tube: Hamamastu 1924 Coincidence tube: Hamamastu 1924 Resolution: < 5-mm Resolution: < 5-mm Shaping time: 300 nsec Shaping time: 300 nsec Count rate capability: ~ 1 MHz Count rate capability: ~ 1 MHz Time-of-Flight Resolution: 1 msec Time-of-Flight Resolution: 1 msec The scintillator screen for this 2-D detector consists of a mixture of 6 LiF and silver-activated ZnS powder in an epoxy binder. Neutrons incident on the screen react with the 6 Li 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 6 LiF:ZnS(Ag) was determined to be 1:3. 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/cm 2 of 6 LiF and 120 mg/cm 2 of ZnS(Ag) is used in this screen design. This mixture has a measured neutron conversion efficiency of over 90%.

14. Optoelektronika i fizyka materiałowa14 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 >1000 o C 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.

15. Optoelektronika i fizyka materiałowa15 1 - Recoil protons – polymer 2 – diffusion of hydrogen 3 – compaction effect Fiber optic neutron sensors

16. Optoelektronika i fizyka materiałowa16

17. Optoelektronika i fizyka materiałowa17 When pure quartz glasses are irradiated with e.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 (UV+VIS). There is known a proposition of use a differential circuit for the sensor build of quartz glass for -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 o C. Fiber optic gamma sensor

18. Optoelektronika i fizyka materiałowa18 1. S.M. Kaczmarek, A. Bensalah, G. Boulon, " -ray induced color centers in pure and Yb doped LiYF 4 and LiLuF 4 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 Yb 3+ /Yb 2+ conversion in CaF 2 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 CaF 2 :Yb single crystals", Proc. SPIE, vol. 5958 (2005), pp. 531-540 3. Analyzis of color centers in fluorides: CaF 2, LiLuF 4, LiYF 4, BaY 2 F 8, KY3F 10 doped with Yb 3+

19. Optoelektronika i fizyka materiałowa19 Influence of the annealing and -irradiation on the absorption of YAG:Nd 1% crystal WTW WAT ICHTJ

20. Optoelektronika i fizyka materiałowa20 Influence of the annealing and irradiation with protons of 20 MeV energy (cyclotron) and electrons (acceler.) of 1 MeV energy on the absorption of YAG:Nd 1% crystal IPJ Świerk

21. Optoelektronika i fizyka materiałowa21 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

22. Optoelektronika i fizyka materiałowa22 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.