The Radiation Tolerance of Specific Optical Fibers at −25 °C

1. The Radiation Tolerance of Specific Optical Fibers at −25 °C Joshua Abramovitch Southern Methodist University Faculty Advisors: Dr. Andy Liu, Dr. Jingbo Ye National Conference on Undergraduate Research Ithaca College Ithaca, NY April 1, 2011

2. Optical Fibers • Optical fibers are materials of high refractive index capable of transmitting data over long distances. • The two main types of optical fibers are multi-mode and single-mode fibers. • Multi-mode fibers can transmit multiple packets of data at high power, but over shorter distances. • Single-mode fibers transmit only one data packet at low power, but over longer distances. • Optical fibers are omnipresent in modern telecommunications. 2

3. ATLAS/CMS ATLAS and CMS are particle physics experiments at the Large Hadron Collider (LHC) at CERN. They are searching for new discoveries in the head-on collisions of protons of extraordinarily high energy. Both experiments have the same goals – discovering the Higgs Boson, extra dimensions, and dark matter – but utilize different technology with their respective detectors to achieve those goals. © CERN 2008 © CERN 2008 3

4. Optical Fibers at CERN • Optical fibers will transmit data between the various detectors and computers at monitoring stations, allowing scientists to observe particle collisions inside the Super Large Hadron Collider (SLHC). • The fibers must be able to transmit data bi-directionally at ~5 Gbps in the presence of low temperatures and high radiation. • To find radiation-tolerant fibers, experiments must be conducted to test their ability to retain signal integrity in a radioactive environment. 4

5. Versatile Link Project • The Versatile Link Project was initiated in April 2008. The project’s main goal is to develop a radiation-tolerant optical interface for upgrades to the SLHC. • One of the steps towards achieving this goal is to find suitable optical fibers to upgrade the SLHC’s fiber optic links at the ATLAS and CMS detectors. • The project employs scientists and engineers from CERN, Oxford, Fermi National Lab, and SMU [1]. 5

6. Previous Versatile Link Experiments In 2008, several optical fibers (SMF-28, Infinicor SX+, Draka-1, Draka-RHP-1, Draka-RHP-2) were tested at room temperature to 650 kGy at various dose rates (22.5, 1.01, 0.424, 0.343, 0.0265 kGy/hr). Two multi-mode fibers (the Infinicor SX+ and Draka-RHP-1) and one single-mode fiber (the SMF-28) were qualified for use in the SLHC environment for warm operations [2]. In 2009, two multi-meter fibers (Infinicor SX+ and Draka-RHP-1) were tested at -25 °C to 30 kGy at 0.5 kGy/hr. It was observed that radiation-induced absorption (RIA) is temperature-dependent [3]. In 2010, fibers (SMF-28e+, Infinicor SX+, Draka-SRH-SMF, X) were tested at -25 °C to 500 kGy at 27 kGy/hr. Two SM fibers (Draka-SRH-SMF and X) were qualified. The SMF-28e+ and Infinicor SX+ showed high levels of RIA during the experiment, but due to the high dose rate used these fibers cannot necessarily be excluded as SLHC detector candidates [4]. 6

7. Experiment Purpose • This experiment is a step towards attaining the Versatile Link Project’s goals. • The purpose was to determine the RIA of certain fibers subjected to a relatively low radiation dose rate at low temperatures. • Certain fibers have already been cleared for use at the SLHC during operations at room temperature. • These fibers were also evaluated at low temperature and high dose rates, but there is still not enough information to qualify them for use at low temperatures. • Also, this experiment tested two new optical fibers (the ClearCurve OM3 and SMF28) that will render some of the fibers previously tested obsolete. 7

8. Digital Multimeter Laptop Light Source 15m fiber (MM) Light Sensor Fiber Roll Freezer Lead 15m fiber Experiment Setup Co-60  at BNL 8

9. Fibers Tested • Fiber M1 was used as a control, at room temperature and outside of the radiation chamber. • Fiber M3 was removed from the radiation chamber early in the experiment for other purposes. 9

10. Temperature Control The fibers were put inside a chest freezer, to maintain an average temperature of -23.81 ± 0.27 °C throughout the experiment. For more information on this aspect of the project, please attend Nnadozie Tassie’s presentation at 4:20 pm today. 10

11. Light Sources Four Vertical Cavity Surface Emitting Lasers (VCSELs) generated 850 nm lasers for the multi-mode fibers. Two Fabry-Perot laser diodes generated 1310 nm lasers for single-mode fibers. 11

12. Light Power Measurement Monolithic photodiodes with on-chip transimpedance amplifiers (Part# OPT101 from TI) converted light into voltage. A digital multimeter (DMM, Model 2700 produced by Keithley) then acquired the data. For the single-mode fibers, an HP 8163 Lightwave multimeter and two HP81536A power sensors were used. 12

13. Calibration of Multi-Mode Light Meters I measured the optical powers with a commercial light meter at certain currents of a VCSEL. Then, I measured the output voltages of a light sensor at the same currents. I fitted each Power-Voltage curve with a 2nd degree polynomial; higher degrees resulted in very little improvement. I then used the fitting coefficients to calculate the optical powers from voltages. Under the assumption that the fits are adequate, I calculated fitting errors. Light source fluctuation is the dominant error source. 13

14. Results RIA = 10*log[P(t0)/P(t)] 14

15. Results – Attenuation vs. Dose Infinicor SX+ Clearcurve OM3 SMF28XB Clearcurve OM3 OSA SMF28 15

16. Comparison with Previous Results Infinicor SX+ -25 °C, 56 Gy/hr 25 °C, 424 Gy/hr 25 °C, 343 Gy/hr 25 °C, 26.5 Gy/hr 16

17. Conclusions • The newer fibers performed better than their counterparts. The ClearCurve OM3 experienced a RIA of 0.0344 dB/m, and the SMF28 experienecd a RIA of 0.0575 dB/m. • All fibers tested are viable candidates for use in the proposed SLHC upgrades, although still more tests are needed to qualify them. Future experiments will utilize radiation doses closer to the conditions likely to be found in the SLHC. • This experiment contributes to the knowledge pool of radiation tolerant optical fibers, opening the door for applications in particle physics and many other scientific endeavors. 17

18. Acknowledgements • I would very much like to thank the following for their contributions to this project: • The Hamilton Scholars program for its support of my participation in this research. • Dr. Stephen L. Kramer (BNL) and Peter Cameron (BNL) for their help during the experiment. • Mr. Kent Liu, Dr. Annie Xiang, Dr. Datao Gong, Dr. James Kierstead, and Ms. Cotty Kerridge for their collaboration. • My faculty advisors for allowing me to be a part of the Versatile Link Project. • Drs. Todd Huffman ‎(Oxford University), James Kierstead (BNL), Tony Weidberg (Oxford University), Jan Troska (CERN), Francois Vasey (CERN), and Alan Prosser (Fermi National Lab) for their collaboration and guidance. 18

19. References L. Amaral et al., The versatile link, a common project for super-LHC, JINST 4 P12003, Dec. 2009. B. Arvidsson et al., The radiation tolerance of specific optical fibres exposed to 650 kGy(Si) of ionizing radiation, JINST 4 P07010, Jul. 2009. C. Issever et al., The Radiation Hardness of Certain Optical Fibres for the LHC Upgrades at −25 ◦C, in proceedings of Topical Workshop on Electronics for Particle Physics, September, 2009 Paris, France. B.T. Huffman et al., The radiation hardness of specific multi-mode and single-mode optical fibres at -25°C beyond a full SLHC dose to a dose of 500 Gy(Si), JINST 5 C11023, Nov. 2010. 19

20. If you have any lingering questions, feel free to e-mail me at jabramovit@smu.edu.