Browsing by Author "Loureiro, Custodio F. M."
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- An all-digital coincidence-selection and coincidence-trigger generation for a small animal RPC-PET cameraPublication . Clemêncio, Filomena; Loureiro, Custodio F. M.; Landeck, JorgeThe time resolution for gamma photon pairs of a detector based on resistive plate chamber technology is close to 300 ps FWHM. This allows a tight time window for coincidence detection, reducing the number of random coincidences observed and the overall noise of the acquired image. We implemented, inside a Xilinx Virtex-5 field programmable gate array, a fully programmable coincidence-trigger system with sub-nanosecond resolution and low latency for a small animal RPC-PET camera being built. An automatic procedure to construct a histogram of coincidences was implemented that helps characterizing the camera and allows compensating for different delays in the time channels. The time window for coincidences can then be placed at the optimal position helping rejecting coincidences from undesired sources.
- Data acquisition and laser scanning synchronism in SS-OCT — An experimental apparatusPublication . Domingues, Jose P.; Silva, Susana F.; Loureiro, Custodio F. M.; Bernardes, Rui; Morgado, A.M.; Clemêncio, FilomenaOptical Coherence Tomography (OCT) is a high-resolution, non-invasive and contactless imaging technique based on optical interferometry. After the Time Domain (TD) and the Spatially Encoded Frequency Domain (SEFD), the Swept-Source (SS) OCT, also known as Time Encoded Frequency Domain (TEFD) OCT, is the latest technology available. It is based on a fast wavelength-sweeping of a narrow laser line over the bandwidth of the source. SWEEP TRIGGER and K-CLOCK signals are provided by the laser source and establish the time base for the overall system. Data acquisition and the two-dimensional scanning of the object of interest must be accurately synchronized after those signals. The proposed solution for the overall scanning/acquisition/sweeping synchronism is an integrated and dedicated FPGA-based control system that is being developed and will generate the automatic, programmable and flexible operation that will replace the present, manually adjustable, system. This way, complete reproducibility of experimental conditions will be obtained, along with the possibility of optimizing the galvanometer/mirrors control. This system is being built around a Xilinx XC6SLX45 FPGA and will be integrated in the already developed control software of the OCT system
- Trigger system for a large area RPC TOF-trackerPublication . Clemêncio, Filomena; Blanco, Alberto; Carolino, Nuno; Loureiro, Custodio F. M.The TOF-tracker concept, the simultaneous measurement of accurate time and bi-dimensional space coordinates in a single gaseous detector, has been previously demonstrated. Recently, a larger area, 1550×1250 mm 2 , RPC detector has been constructed. Signals are induced in metallic strips located in each side of the RPC active volume and coupled to both charge-sensitive and timing circuits, that can be used to generate a coincidence trigger. In this work, the architecture and performance of the trigger system of the detector is reported. The system is based on off-the-shelf inexpensive modules and in a custom program written in VHDL running in a Xilinx Spartan-6 FPGA. It is fast, fully parameterized and supports several trigger strategies, allowing at the same time the collection of several information referring to the operating condition of the detector, relevant for tests and detector maintenance.