APRÈN. Portal de la producció docent del professorat de la UPC

The advancement of nuclear fusion technology has led to a growing need for accurate diagnostic instruments to ensure the safety and effectiveness of fusion reactors. This thesis focuses on the creation and evaluation of a dimensional measurement diagnostic system based on Light Detection and Ranging (LIDAR) specifically designed for the IFMIF-DONES (International Fusion Materials Irradiation Facility - Demo Oriented Neutron Source) facility. The IFMIF-DONES project, within which this system is developed, aims to test materials for nuclear fusion reactors. The DONES-FLUX (Demo Oriented Neutron Source Flux) project is a publicly funded project that allows the development of specific subsystems of the IFMIF-DONES facility which are concerned with fluxes within the facility, be they electrical neutrons of lithium focus. In this project, high-energy neutrons are produced by colliding deuterium ions accelerated in a linear accelerator with a liquid lithium jet. The resulting neutrons are then used to assess how materials perform under the extreme conditions inside a fusion reactor. The objective of the LIDAR system is to monitor the depth variations of the liquid lithium jet target in real time, which is crucial to maintain the stability and efficiency of neutron generation. The research involves the selection and implementation of an amplitude-modulated (AM) LIDAR system, recognized for its high precision, which are vital to achieve the desired measurement accuracy. The DONES-FLUX project requires the system to achieve both precision and accuracy of less than 0.3 mm, with the aim of achieving less than 0.1 mm precision and accuracy in laboratory tests. A series of experiments were conducted to rigorously test the system, including characterization of the flat surface, measurements of distance between various surfaces, and evaluations of periodic surfaces The performance of the system remained stable across different scanning speeds and lock-in amplifier time constants, preserving precision even in dynamic situations. Significant challenges, such as the “smiley face” effect inherent in the scanning methodology, were effectively mitigated through quadratic fitting methods, further enhancing the system's reliability. The system achieved an accuracy of less than 0.1 mm in controlled laboratory settings and demonstrated a precision of around 0.01 mm when measuring distances between different surfaces. However, when evaluating periodic surfaces, while the accuracy remained below 0.1 mm, the precision was around 0.2 mm due to the low voltage received from the surface, which increased with the time constant. This indicates the need for further optimization to improve the precision of periodic surfaces. Despite these challenges, the system performed efficiently with static targets, confirming its suitability for accurate depth measurements under controlled conditions. However, additional research is necessary to assess its performance with dynamic targets, such as the liquid lithium jet in operation within the IFMIF-DONES facility. The dynamic nature of the actual target in the testing facility environment introduces challenges that were not fully explored in this study, which warrants further investigation to ensure the system can maintain its precision and accuracy under real-world conditions. In summary, the developed LIDAR-based diagnostic system is well equipped for real-time monitoring of the lithium jet in a testing facility environment, providing a reliable and precise solution for depth measurement. The system not only meets the requirements of precision and accuracy, but also shows potential for further optimization, particularly in improving precision for periodic surfaces, and broader application in fusion diagnostics, making a significant contribution to the advancement of nuclear fusion technology

Nowadays, the technique of eye tracking is starting to be used for recording eye movements in patients suffering from some type of cognitive impairment, as various studies have suggested that these are altered in neurodegenerative diseases. Therefore, it is believed that in the future, such systems could serve as a diagnostic tool to early detect neurological alterations, particularly those that produce cognitive impairments. This work is part of a clinical study that began in 2020, which aims to study the alterations in oculomotor function and pupillary response in patients with post COVID condition who present cognitive impairment, and to compare the results obtained with control patients, that is, healthy patients who have never had COVID-19. To do this, various eye movements of patients have been measured, such as saccades, pursuit movements, and fixations with an eye tracker, also analysing their pupillary response (mydriasis and miosis). In total, 16 control participants, 31 who had a mild form of the disease (mild COVID), and 9 who had a severe form and even required hospitalisation (severe COVID) were included in the study. Thus, the characteristics of oculomotor alterations found in patients with persistent COVID (pursuit and fixation) could be useful for understanding different pathophysiological mechanisms of the disease and its impact on cognitive levels. It has been seen that the characteristics of oculomotor alterations found in patients with persistent COVID (pursuit and fixation) could be useful for understanding different pathophysiological mechanisms of the disease and its impact on cognitive levels.

Eye movements have been shown to be altered in neurological disorders with eye-tracking technology, and thus it has been recently proposed to use them as biomarkers for their early diagnosis. The eye-tracker EyeLink 1000 Plus is the current Gold Standard to record eye movements but has some limitations to be used in a clinical environment. The purpose of this work was to compare the performance of a new, less complex eye-tracker, the Tobii Pro Spectrum, with the EyeLink 1000 Plus for screening purposes. To do so, both eye-trackers were used to record eye movements of 10 participants when performing several visual tasks (saccades, smooth pursuit and fixation). A software was implemented to display the visual stimuli on a screen and to acquire and process the data with the Tobii Pro Spectrum. The results and the statistical analysis carried out suggest that both eye-trackers provide similar data for most of the parameters analysed, meaning that the Tobii Pro Spectrum is a useful tool to record eye movements with a precision similar to that of the Gold Standard and thus, that it could be used for clinical analyses.

In this work, we introduce and develop a new Near-Eye Display (NED) AR/VR switching prototype based on Holographic Optical Elements (HOEs) and retinal projection. In comparison to the commercially available devices and the state-of-the-art, the implemented NED system possess an extended and competitive field of view, a reduced form factor and high transparency when used on AR mode. Recording and reproduction processes of photopolymer HOE for single color cases were analyzed and carried out, as well as the study of its generalization to the multicolor (RGB) case. Lastly, the performance of the NED device is tested and discussed.

Recull de les ponències presentades al 13è Congreso Nacional del Color, celebrat en format híbrid els dies 29-30 de junio y 1 de julio de 2022