Alcalde Bessia, F., M. Pérez, M. Sofo Haro, I. Sidelnik, J. J. Blostein, S. Suárez, P. Pérez, M. Gómez Berisso, and J. Lipovetzky. "Displacement Damage in CMOS Image Sensors After Thermal Neutron Irradiation." IEEE Transactions on Nuclear Science 65, no. 11 (2018): 2793–2801.
Abstract: In this paper, CMOS image sensors were exposed to thermal neutrons observing an increase in the dark signal of many pixels. The effect was found to be similar to the damage caused by alpha particles irradiation. Rutherford backscattering spectroscopy (RBS) and SIMNRA simulation were used to confirm that the sensors contain boron in the insulation layers. The damage produced by thermal neutrons is explained as displacement damage caused by alpha particles and lithium-7 ions in the silicon active volume of the sensors after boron-10 thermal neutron capture.
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Haberkorn, N., S. Bengio, S. Suárez, P. D. Pérez, J. A. Hofer, and M. Sirena. "Effect of thermal annealing and irradiation damage on the superconducting critical temperature of nanocrystalline γ-Mo2N thin films." Materials Letters 236 (2019): 252–255.
Abstract: We report on the influence of the disorder and stoichiometry in the resulting superconducting critical temperature of γ-Mo2N thin films. Initially, three films (with Tc values of 7.6 K, 6.8 K and 6 K) were grown at room temperature by reactive sputtering, on Si (1 0 0) using different N2/(Ar+N2) mixtures. The influence of the thermal annealing up to 973 K and irradiation damage produced by 1 MeV Zr+(fluence up 2 × 1014 cm−2) is analyzed. The Tc of pristine films remains unchanged for increasing irradiation doses up 2 × 1014 cm−2. The Tc for annealed films decreases close to the value expected for bulk samples (≈5 K) for increasing the annealing temperature. Successive irradiations of the annealed films tend to increase their Tc up to its initial values (before annealing). The results indicate that the Tc in nanometric grain size γ-Mo2N thin films is affected by both nitrogen stoichiometry and disorder at the atomic scale.
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Haberkorn, N., S. Suárez, P. D. Pérez, H. Troiani, P. Granell, F. Golmar, J. - H. Lee, and S. H. Moon. "Effect of mixed pinning landscapes produced by 6 MeV oxygen irradiation on the resulting critical current densities Jc in 1.3 µm thick GdBa2Cu3O7-d coated conductors grown by co-evaporation." Physica C: Superconductivity and its Applications 542 (2017): 6–11.
Abstract: We report the influence of crystalline defects introduced by 6 MeV 16O3+ irradiation on the critical current densities Jc and flux creep rates in 1.3 µm thick GdBa2Cu3O7-δ coated conductor produced by co-evaporation. Pristine films with pinning produced mainly by random nanoparticles with diameter close to 50 nm were irradiated with doses between 2 × 1013 cm−2 and 4 × 1014 cm−2. The irradiations were performed with the ion beam perpendicular to the surface of the samples. The Jc and the flux creep rates were analyzed for two magnetic field configurations: magnetic field applied parallel (H║c) and at 45° (H║45°) to the c-axis. The results show that at temperatures below 40 K the in-field Jc dependences can be significantly improved by irradiation. For doses of 1 × 1014 cm−2 the Jc values at μ0H = 5 T are doubled without affecting significantly the Jc at small fields. Analyzing the flux creep rates as function of the temperature in both magnetic field configurations, it can be observed that the irradiation suppresses the peak associated with double-kink relaxation and increases the flux creep rates at intermediate and high temperatures. Under 0.5 T, the flux relaxation for H‖c and H||45° in pristine films presents characteristic glassy exponents μ = 1.63 and μ = 1.45, respectively. For samples irradiated with 1 × 1014 cm−2, these values drop to μ = 1.45 and μ = 1.24, respectively
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Mateos, H., J. Lipovetzky, F. Alcalde Bessia, M. Perez, P. Cappagli, and M. Gomez Berisso. "Characterization of sensors and design of an embedded photodetectors array for beam profile measurements in radiotherapy." In 2017 Eight Argentine Symposium and Conference on Embedded Systems (CASE), 1–6. 2017 Eight Argentine Symposium and Conference on Embedded Systems (CASE)., 2017.
Abstract: In this work, the dosimetric performance of several Commercial Of The Shelf photodiodes was studied. They were tested against gamma rays from a teletherapy source and were characterized with the aim of building a one-dimensional array of dosimeters able to measure the the spatial distribution of dose in a radiotherapy irradiation field. An embedded system comprising an array of 40 photodiodes and its acquisition electronics was built and tested. The dose resolution of each detector was 0.06 cGy and the spatial resolution of the system 0.5 cm.
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Perez, M., F. Alcalde, M. S. Haro, I. Sidelnik, J. J. Blostein, M. Gomez Berisso, and J. Lipovetzky. "Implementation of an ionizing radiation detector based on a FPGA-controlled COTS CMOS image sensor." In 2017 XVII Workshop on Information Processing and Control (RPIC), 1–6. 2017 XVII Workshop on Information Processing and Control (RPIC)., 2017.
Abstract: This work presents the development and implementation of an ionizing radiation detector based on a commercial off the shelf CMOS image sensor and a FPGA. The response of the system was tested in irradiations with gamma photons, beta and alpha particles using different configurations of the image sensor. Finally, we analyze the possible uses of such configurations in the discrimination of events produced by alpha particles in mixed radiation fields.
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