Radiation Issues in Fibers

Transcription

1 Radiation Issues in Fibers ICAN Workshop Jena, , Jochen Kuhnhenn AT&T MM 3A D=000 Gy GI F-doped (?) GI P-doped GI Ge-doped SI Pure silica Wavelength [nm] Dose [Gy] Radiation Issues in Fibers Radiation effects in optical fibers Radiation characterization Conclusions

2 Fraunhofer INT Nuclear effects in electronics and optics Fraunhofer INT works on radiation effects in electronics and optics since nearly 30 years Running several dedicated irradiation facilities, used and optimized only for conduction of test on optical fibers, optics, and electronics Three Co-60 sources Neutron generator Continuos 450 kev X-ray facility Pulsed flash X-ray facility (20 ns) Characterization for users and manufacturers of optical fibers in radiation environments Project partners: Accelerators (Desy, CERN), European fiber manufacturers, users in space or nuclear applications Slide 3 Radiation Issues in Fibers Radiation effects in optical fibers Radiation characterization Conclusions 2

3 Radiation effects in silica-based optical fibers Overview Radiation in this presentation means ionizing radiation, such as gammas, X-rays, high energy electrons, protons or other particles Photo darkening and Solarization are not topics of this presentation Radiation potentially changes every property of optical fibers Radiation-induced attenuation increase (RIA) Main problem Radiation-induced luminescence Only at higher dose rates Change of mechanical properties Change of bandwidth Mainly at higher doses Change of refractive index Slide 5 Radiation effects in optical fibers Introduction Dose quantifies the energy that is deposited in matter due to the interaction of the radiation with the target material Approximate examples of relevant dose levels (for gamma radiation) Mean exposition in Germany Gy/a Lethal dose (whole body) 0 Gy Optical fibers inside a satellite 0 3 Gy Typical dose for irradiation test of optical fibers 0 4 Gy Expected dose for optical fibers in LHC tunnel area 0 6 Gy Slide 6 3

4 Radiation effects in optical fibers Physical description Ionizing radiation generates free electron-hole pairs and breaks bonds Some of these released electrons get caught at positively charged precoursor defect centers These color centers provide additional absorption bands leading to increased attenuation Sylvain Girard, private communication Slide 7 Radiation effects in optical fibers Influences and dependencies of RIA Design parameters Fiber type (SM, GI, SI, PCF, ) CCDR Coating material Manufacturing parameters Preform process and quality Core dopants Cladding dopants (for SMF) OH-content Drawing speed, temperature and tension Environmental parameters Dose levels Dose rates Pre-irradiations Temperature Application parameters Wavelength Light power Launch conditions Exposed length Slide 8 4

5 Radiation Issues in Fibers Radiation effects in optical fibers Radiation characterization Conclusions of RIA Core dopants Example of influence of core dopants Two graded-index fibers were ordered from the same manufacturer Customer was not aware of different production methods within the manufacturer plants Large efforts were needed to implement radiation harder fiber and to exclude radiation sensitive Carefully check manufacturers or distributors knowledge and data Slide 0 5

6 Core dopants GI F-doped (?) GI P-doped GI Ge-doped SI Pure silica What does that mean for injected light of mw: Wavelength: ~830 nm Fibre length: 00 m Pure silica fibre: 0.89 mw F-doped fibre: 0.7 mw Ge-doped fibre: mw P-doped fibre: mw Dose [Gy] Slide Manufacturer of GI fibers Induced attenuation for 4 commercially available fibers of different manufacturers Measurements done from 995 to 2002 (Ge+P)-doped fibers show much higher induced attenuation The P-free fibers differ up to a factor of Commercial Fiber Commercial Fiber 2 Commercial Fiber 3 Commercial Fiber 4 (Ge+P)-doped core Ge-doped core 50/25 µm GI-Fibers = nm D = Gy/min Dose [Gy] Slide 2 6

7 Manufacturer of SM fibers 000 Commercial fiber (2005) Commercial fiber 2 (2005) j-fiber, Rad. Hard Std. SMF (2005) Siecor/Corning, SMF 28 (992) Lightspec (995) Comparison of three types of single-mode fibers: Pure silica core 00 0 SM-Fibers =550 nm Ge-doped core, P-doped cladding Ge-doped core Pure silica core Ge-doped core P-doped cladding Phosphorus-free (core) does not mean radiation resistant No improvement of radiation resistance with decrease of intrinsic attenuation up to Dose [Gy] Slide 3 Dopants and manufacturers in SM fibers =30 nm, D=0 4 Gy, D=0.2 Gy/s, T=24-28 C, l= m, P=0/40 µw Ge-doped,2,3 PSC,2 Unknown F-doped Kuhnhenn et al., doi 0.09/TNS Dose [Gy(SiO 2 )] Slide 4 7

8 Manufacturers of pure silica SI fibers 00 =854 nm, T=23 C 0 Oxford Electronics Ltd. (Polyimide Coating) Heraeus-Tenevo (CCDR.2) Oxford Electronics Ltd. (Acrylate Coating) j-plasma (CCDR.) Dose [Gy] Slide 5 Fiber type Photonic crystal fiber First results published on radiation-induced attenuation of hollow-core fiber in comparison to conventional fibers Extremely low RIA since much less material is involved in light guiding Commercial availability limited Crystal Fiber HC (2005) Commercial fiber 2 (2005) j-fiber, Rad. Hard Std. SMF (2005) Siecor/Corning, SMF 28 (992) Lightspec (995) SM-Fibers =550 nm Hollow core fiber Ge-doped core Pure silica core Dose [Gy] Slide 6 8

9 Wavelength AT&T MM 3A D=000 Gy Wavelength [nm] Slide 7 Dose rate High variation in dose rate response Consequences for test design with respect to application 3.0 Gy/s Ge-doped Unknown F-doped.4 Gy/s 0.2 Gy/s 0 0, 0.02 Gy/s Dose [Gy(SiO 2 )] Dose rate [Gy/s] Slide 8 9

10 Light power and temperature a b 0, a 0.2 Gy/s b c Parameter variation for 0.2 Gy/s (a): Wavelength (30 nm 550 nm) (b): Temperature (23 C 35 C) (c): Lightpower (0 µw 350 µw) c Dose [Gy(SiO 2 )] Slide 9 Geometry and Manufacturing Ratio of induced losses for. and.2 fibres 2.50 BE (AC+PI, nm) DD (AC+PI, nm) Dose [Gy] Slide 20 0

11 Rare earth doped fibers Radiation-induced attenuation Henschel et al., TNS 45, p. 552, 998 Very high absorption in REdoped fibers, RIAunit: db/m Main reason for high RIA is Al-co-doping New developments introducing co-dopants such as Ce show lower RIA Slide 2 Rare earth doped fibers Amplification consequences Girard et al., Presented at RADECS 20 RIA is not the only important factor Amplification reduces with irradiation Effective interaction length decreases Optimization has to consider full system Slide 22

12 Radiation Issues in Fibers Radiation effects in optical fibers Radiation characterization Conclusions Radiation characterization of optical fibers Sketch of experimental setup at Fraunhofer INT 60 Co Test fibre spool Fusion splices Lead box Lead tubes Gammamat TK000 (max. 600 Ci 60 Co) Coupler Concrete shielding Thermally stabilized measurement booth Fibre optic cables LED/LD Source Variable Attenuator Connectors 2-Ch optical Power meter A B GPIB Control computer for remote access Ethernet LabView controlled data acquisition system Slide 24 2

13 Radiation characterization of optical fibers Experimental setup at Fraunhofer INT Co-60 gamma irradiator Sample spool Lead fibers Shielding for lead fibers Slide 25 Radiation characterization Repeatability Five optical fibers were irradiated four times over a period of more than a year All samples were pristine and individually prepared Experimental setup from scratch for each test Results in agreement with each other within 5% Slide 26 3

14 Radiation characterization Quality assurance during production Re-Test of 2005 Sample [2.28 Gy/s] Sample #3 6S-0527/3 [2.28 Gy/s] Sample #4 7S-0005/3 Sample #5 7S-0005/4 Sample #6 7S-0030/4 [2.27 Gy/s] Sample #9 7S-058/3 Sample #0 7S-0204/5 Sample # 7S-0223/3 Sample #3 7S-0237/2 Sample #4 7S-0258/3 Sample #6 7S-0306/3 Sample #2 7S-0237/ Dose [Gy(SiO 2 )] Slide 27 Radiation characterization Test standards International standards [] Optical Fibres Part -54: Measurement Method and Test Procedures Gamma Irradiation, IEC , [2] Standard Guide for Procedure for Measuring Ionizing Radiation-Induced Attenuation in Silica-Based Optical Fibers and Cables for Use in Remote Fiber-Optic Spectroscopy and Broadband Systems ASTM E64-94, [3] Procedure for Measuring Radiation-Induced Attenuation in Optical Fibers and Optical Cables NATO Nuclear Effects Task Group A/C 243, Panel IV (RSG.2), Chair: E.J. Friebele, 992. [4] FOTP-64: Procedure for Measuring Radiation-Induced Attenuation in Optical Fibers and Optical Cables TIA , 997. [5] Fibre Optic Interconnecting Devices and Passive Components Basic Test and Measurement Procedures Part 2-3: Tests; Nuclear Radiation EN , 995. [6] Nuclear Radiation Fibre Optic Guidance IEC TR 62283, 2003, Technical Report. Some of these standards recommend details that do not lead to optimal results Detailed knowledge of application and test methodology needed Slide 28 4

15 Radiation characterization Guidelines It is difficult to compare laboratory results (even if all details are given) If is difficult to extrapolate laboratory data to the application Test conditions should be explicitly defined If the application is well defined, radiation testing should be as close as possible in all conditions Considerations for fiber irradiation tests: Uncertainty of dosimetry (dose rate, activation time, scattered radiation, shielding, homogeneity, ) Sample preparation (no mechanical stress in the fiber, bending radius, consideration of fiber leads irradiation, selection of sample length, ) Measurement conditions (stability of light sources, temperature stability, dynamic range of equipment, ) Slide 29 Conclusions Radiation effects in fibers can severely decrease system performance Nearly all manufacturing or operational parameters have influence of radiation sensitivity Differences of several orders of magnitude possible There exists no predictive model of RIA Testing the actual product under comparable (or standardized) conditions indispensable in critical applications Slide 30 5