Fully digital intensity modulated LIDAR

AbstractIn several applications, such as collision avoidance, it is necessary to have a system able to rapidly detect the simultaneous presence of different obstacles. In general, these applications do not require high resolution performance, but it is necessary to assure high system reliability also within critical scenarios, as in the case of partially transparent atmosphere or environment in presence of multiple objects (implying multiple echoes having different delay times.) This paper describes the algorithm, the architecture and the implementation of a digital Light Detection and Ranging (LIDAR) system based on a chirped optical carrier. This technique provides some advantages compared to the pulsed approach, primarily the reduction of the peak power of the laser. In the proposed architecture all the algorithms for signal processing are implemented using digital hardware. In this way, some specific advantages are obtained: improved detection performance (larger dynamics, range and resolution), capability of detecting multiple obstacles having different echoes amplitude, reduction of the noise effects, reduction of the costs, size and weight of the resulting equipment. The improvement provided by this fully digital solution is potentially useful in different applications such as: collision avoidance systems, 3D mapping of environments and, in general, remote sensing systems which need wide distance and dynamics

Radiation Tolerant 3D Laser Scanner for Structural Inspections in Nuclear Reactor Vessels and Fuel Storage Pools

Accurate and timely assessment of displacements and/or structural damages in nuclear reactor vessels' components is a key action in routine inspections for planning maintenance and repairs but also in emergency situations for mitigating consequences of nuclear incidents. Nevertheless, all these components are maintained underwater and reside in high-radiation fields thus imposing harsh operative conditions to inspection devices which must cope with effects such as Cerenkov radiation background, Total Ionizing Radiation (TID), and occlusions in the detectors' field of view. To date, ultrasonic techniques and video cameras are in use for inspection of components' integrity and with measurements of volumetric and surface crack opening displacements, respectively. The present work reports the realization of a radiation tolerant laser scanner and the results of tests in a nuclear research reactor vessel for acquisition of 3D models of critical components. The device, qualified for underwater operation and for withstanding up to 1 MGy of TID, is based on a 515 nm laser diode and a fast-scanning electro-optic unit. To evaluate performances in a significant but controlled environment, the device has been deployed in the vessel of a research reactor operated by ENEA in the Casaccia Research Centre in Rome (Italy). A 3D model of the fuel rods assembly through a cooling water column of 7 m has been acquired. The system includes proprietary postprocessing software that automatically recognizes components of interest and provides dimensional analysis. Possible application fields of the system stretch to dimensional analysis also in spent nuclear fuel storage pools

Oregano herb adulteration detection through rapid spectroscopic approaches: Fourier transform-near infrared and laser photoacoustic spectroscopy facilities

Oregano is a culinary herb known and used worldwide, whose demand and cost encourage illegal activities in terms of fraud, especially adulteration. The scope of this study is to provide a rapid, cost-effective and easy-to-use approach to detect the adulteration of oregano with a common matrix, the olive leaves. Two analytical solutions were considered, Fourier transform near infrared (FT-NIR), using two different instruments, and laser photoacoustic spectroscopy (LPAS). Different raw data preprocessing procedures were applied, Principal Component Analysis (PCA) was used for preliminary data visualisation, while Partial Least Squares Regression (PLS-R) and Discriminant Analysis (PLS-DA) allowed the authors to classify samples with different adulteration percentages. FT-NIR performed better than LPAS, perhaps also because the photoacoustic system is still an experimental prototype. For example, the coefficient of determination R2 between actual and predicted adulterant concentrations was in the range 0.93–1.00 for FT-NIR and in the range 0.86–0.96 for LPAS. Nevertheless, this allowed the use of a low level data fusion approach to increase the consistency of the statistical model. The fusion between raw data from the LPAS prototype and one of the FT-NIR instruments gave optimal results, confirming the potential of these analytical solutions for the identification of oregano adulterants. The approaches used in the present work could be applied to the identification of other adulterants in herbs and spices by food companies for quality control measurements, possibly for on line and in field analysis

A microwave interferometer for small and tenuous plasma density measurements

The non-intrusive density measurement of the thin plasma produced by a mini-helicon space thruster (HPH.com project) is a challenge, due to the broad density range (between 1016 m 123 and 10^19 m 123) and the small size of the plasma source (2 cm of diameter). A microwave interferometer has been developed for this purpose. Due to the small size of plasma, the probing beam wavelength must be small (\u3bb = 4 mm), thus a very high sensitivity interferometer is required in order to observe the lower density values. A low noise digital phase detector with a phase noise of 0.02\ub0 has been used, corresponding to a density of 0.5 7 10^16 m 123