Scintillator Pad Detector: Very Front End Electronics

El Laboratori d'Altes Energies de La Salle és un membre d'un grup acreditat per la Generalitat. Aquest grup està format per part del Departament d'Estructura i Constituents de la Matèria de la Facultat de Física de la Universitat de Barcelona, part del departament d'Electrònica de la mateixa Facultat i pel grup de La Salle. Tots ells estan involucrats en el disseny d'un subdetector en l'experiment de LHCb del CERN: el SPD (Scintillator Pad Detector). El SPD és part del Calorímetre de LHCb. Aquest sistema proporciona possibles hadrons d'alta energia, electrons i fotons pel primer nivell de trigger. El SPD està format per una làmina centellejeadora de plàstic, dividida en 600 cel.les de diferent tamany per obtenir una millor granularitat aprop del feix. Les partícules carregades que travessin el centellejador generaran una ionització del mateix, a diferència dels fotons que no la ionitzaran. Aquesta ionització, generarà un pols de llum que serà recollit per una WLS que està enrotllada dins de les cel.les centellejadores. La llum serà transmesa al sistema de lectura mitjançant fibres clares. Per reducció de costos, aquestes 6000 cel.les estan dividides en grups, usant MAPMT (fotomultiplicadors multiànode) de 64 canals per rebre la informació en el sistema de lectura. El senyal de sortida dels fotomultilplicadors és irregular degut al baix nivell de fotoestadística, uns 20-30 fotoelectrons per MIP, i degut també a la resposta de la fibra WLS, que té un temps de baixada lent. Degut a tot això, el processat del senyal, es realitza primer durant la integració de la càrrega total i finalment per la correcció de la cua que conté el senyal provinent del PMT. Aquesta Tesi està enfocada en el sistema de lectura de l'electrònica del VFE del SPD. Aquest, està format per un ASIC (dissenyat pel grup de la UB) encarregat d'integrar el senyal, compensar el senyal restant i comparar el nivell d'energia obtingut amb un llindar programable (fa la distinció entre electrons i fotons), una FPGA que programa aquests llindars i compensacions de cada ASIC i fa el mapeig de cada canal rebut en el detector i finalment usa serialitzadors LVDS per enviar la informació de sortida al trigger de primer nivell. En el disseny d'aquest tipus d'electrònica s'haurà de tenir en compte, per un costat, restriccions de tipus mecànic: l'espai disponible per l'electrònica és limitat i escàs, i per un altre costat, el nivell de radiació que deurà suportar és considerable i s'haurà de comprobar que tots els components superin un cert test de radiació, i finalment, també s'haurà de tenir en compte la distància que separa els VFE dels racks on la informació és enviada i el tipus de senyal amb el que es treballa en aquest tipus d'experiments: mixta i de poc rang.El Laboratorio de Altas Energías de la Salle es un miembro de un grupo acreditado por La Generalitat. Este grupo está formado por parte del departamento de Estructura i Constituents de la Matèria de la Facultad de Física de la Universidad de Barcelona, parte del departamento de Electrónica de la misma Facultad y el grupo de La Salle. Todos ellos están involucrados en el diseño de un subdetector en el experimento de LHCb del CERN: El SPD (Scintillator Pad Detector). El SPD es parte del Calorímetro de LHCb. Este sistema proporciona posibles hadrones de alta energía, electrones y fotones para el primer nivel de trigger.El SPD está diseñado para distinguir entre electrones y fotones para el trigger de primer nivel. Este detector está formado por una lámina centelleadora de plástico, dividida en 6000 celdas de diferente tamaño para obtener una mejor granularidad cerca del haz. Las partículas cargadas que atraviesen el centelleador generarán una ionización del mismo, a diferencia de los fotones que no la generarán. Esta ionización generará, a su vez, un pulso de luz que será recogido por una WLS que está enrollada dentro de las celdas centelleadoras. La luz será transmitida al sistema de lectura mediante fibras claras. Para reducción de costes, estas 6000 celdas están divididas en grupos, utilizando un MAPMT (fotomultiplicadores multiánodo) de 64 canales para recibir la información en el sistema de lectura. La señal de salida de los fotomultiplicadores es irregular debido al bajo nivel de fotoestadística, unos 20-30 fotoelectrones por MIP, y debido también a la respuesta de la fibra WLS, que tiene un tiempo de bajada lento. Debido a todo esto, el procesado de la señal, se realiza primero mediante la integración de la carga total y finalmente por la substracción de la señal restante fuera del período de integración. Esta Tesis está enfocada en el sistema de lectura de la electrónica del VFE del SPD. Éste, está formado por un ASIC (diseñado por el grupo de la UB) encargado de integrar la señal, compensar la señal restante y comparar el nivel de energía obtenido con un umbral programable (que distingue entre electrones y fotones), y una FPGA que programa estos umbrales y compensaciones de cada ASIC, y mapea cada uno de los canales recibidos en el detector y finalmente usa serializadores LVDS para enviar la información de salida al trigger de primer nivel. En el diseño de este tipo de electrónica se deberá tener en cuenta, por un lado, restricciones del tipo mecánico: el espacio disponible para la electrónica en sí, es limitado y escaso, por otro lado, el nivel de radiación que deberá soportar es considerable y se tendrá que comprobar que todos los componentes usado superen un cierto test de radiación, y finalmente, también se deberá tener en cuenta la distancia que separa los VFE de los racks dónde la información es enviada y el tipo de señal con el que se trabaja en este tipo de experimentos: mixta y de poco rango.Laboratory in La Salle is a member of a Credited Research Group by La Generatitat. This group is formed by a part of the ECM department, a part of the Electronics department at UB (University of Barcelona) and La Salle's group. Together, they are involved in the design of a subdetector at LHCb Experiment at CERN: the SPD (Scintillator Pad Detector). The SPD is a part of LHCb Calorimeter. That system provides high energy hadrons, electron and photons candidates for the first level trigger. The SPD is designed to distinguish electrons and photons for this first level trigger. This detector is a plastic scintillator layer, divided in about 6000 cells of different size to obtain better granularity near the beam. Charged particles will produce, and photons will not, ionisation on the scintillator. This ionisation generates a light pulse that is collected by a Wavelength Shifting (WLS) fibre that is twisted inside the scintillator cell. The light is transmitted through a clear fibre to the readout system. For cost reduction, these 6000 cells are divided in groups using a MAPMT of 64 channels for receiving information in the readout system. The signal outing the SPD PMTs is rather unpredictable as a result of the low number of photostatistics, 20-30 photoelectrons per MIP, and the due to the response of the WLS fibre, which has low decay time. Then, the signal processing must be performed by first integrating the total charge and later subtracting to avoid pile-up. This PhD is focused on the VFE (Very Front End) of SPD Readout system. It is performed by a specific ASIC (designed by the UB group) which integrates the signal, makes the pile-up compensation, and compares the level obtained to a programmable threshold (distinguishing electrons and photons), an FPGA which programs the ASIC thresholds, pile-up subtraction and mapping the channels in the detector and finally LVDS serializers, in order to send information to the first level trigger system. Not only mechanical constraints had to be taken into account in the design of the card as a result of the little space for the readout electronics but also, on one hand, the radiation quote expected in the environment and on the other hand, the distance between the VFE electronics and the racks were information is sent and the signal range that this kind of experiments usually have

Mobile robot guidance using cellular neural networks and fuzzy logic

We show how a Cellular Neural Networks based im­age processing system together with a Tuzzy Logic controller are capable of providing the necessary signal processing to guide an autonomous mobile robot in a maze drawn on the fl.oor. In this way, a non-trivial navigation task is obtained by very sim­ple hardware, making real autonomous operation feasible. An autonomous line-following robot has been first simulated and is currently being imple­roented by simulating the CNN with a DSP, while the fuzzy algorithms run on a 386-microprocessor ­based microcontroller

Tactile Fabric Panel in an Eight Zones Structure

By introducing a percentage of conductive material during the manufacture of sewing thread, it is possible to obtain a fabric which is able to detect variations in pressure in certain areas. In previous experiments the existence of resistance variations has been demonstrated, although some constrains of cause and effect were found in the fabric. The research has been concentrated in obtaining a fabric that allows electronic detection of its shape changes. Additionally, and because a causal behavior is needed, it is necessary that the fabric recovers its original shape when the external forces cease. The structure of the fabric varies with the type of deformation applied. Two kinds of deformation are described: those caused by stretching and those caused by pressure. This last type of deformation gives different responses depending on the conductivity of the object used to cause the pressure. This effect is related to the type of thread used to manufacture the fabric. So, if the pressure is caused by a finger the response is different compared to the response caused by a conductive object. Another fact that has to be mentioned is that a pressure in a specific point of the fabric can affect other detection points depending on the force applied. This effect is related to the fabric structure. The goals of this article are validating the structure of the fabric used, as well as the study of the two types of deformation mentioned before

LHCb inner tracker: Technical Design Report

The LHCb experiment [1] is designed to exploit the large bb production cross section at the LHC in order to perform a wide range of precision studies of CP violating phenomena. The copious production of Bd, Bs and Bc mesons and b-baryons, together with the unique particle-identification capabilities of the LHCb detector, will allow the experiment to perform sensitive measurements of CP violating asymmetries in a variety of channels that are beyond the reach of the current generation of CP-violation experiments. Since bb pairs at the LHC are predominantly produced at small angles with respect to the beam axis, the LHCb detector has been designed as a single-arm forward spectrometer. Its acceptance extends out to 300 mrad in the horizontal bending plane of the 4Tm dipole magnet and to 250 mrad in the vertical plane. The forward acceptance of the spectrometer is limited by the LHC beam-pipe which follows a 10 mrad cone. A side view of the LHCb detector is shown in Figure 1. The main tracking system consists of four planar tracking stations: one station (\TT") is located in between RICH1 and the magnet, three stations (\T1-T3") are located between the magnet and RICH2. Two detector technologies are employed in stations T1-T3: the outer region of these stations, away from the beam-pipe, is covered by the straw-tube drift chambers of the Outer Tracker, which has been described in an earlier TDR [2]. The innermost region around the beam-pipe, where particle densities are highest, is covered by silicon microstrip detectors | the Inner Tracker described in this document. An isometric view of the sensitive elements of one Inner Tracker station is shown in Figure 1.1. It covers a cross-shaped area around the beam pipe, approximately 120 cm wide and 40 cm high. Each station consists of four detection layers, with two ±5º stereo views sandwiched in between two layers with vertical strips. The overall sensitive surface of the three Inner Tracker stations amounts to approximately 4.2m2. Large strip pitches of approximately 200 μm and read-out strips of up to 22 cm length will be employed in order to minimise the number of read-out channels. The approximately 140 cm wide and 120 cm high TT station is entirely covered by silicon microstrip detectors. Inner Tracker and TT station together form the Silicon Tracker project, and in order to indicate the overall size of the project, a brief description of the layout of this station is given in section 1.2. However, the TT station is outside the scope of this document and will be described in a future TDR

LHCb reoptimized detector design and performance: Technical Design Report

The LHCb experiment has been conceived to study CP violation and other rare phenomena in B meson decays with very high precision. This should provide a profound understanding of quark flavour physics in the framework of the Standard Model, and may reveal a sign of the physics beyond. In order to achieve these goals, the LHCb detector must have a high track reconstruction efficiency, π– K separation capability from a few to ∼100 GeV/c, very good proper-time resolution of ∼ 40 fs and high trigger efficiencies, not only for final states including leptons but also for those with hadrons alone. The detector described in the Technical Proposal (TP) [1], approved in September 1998, was designed to fulfil those requirements. This document describes a reoptimization of the detector, that has been made to reduce the material budget and to improve the trigger performance. At the time of the TP the material budget up to the second Ring Imaging Cherenkov detector (RICH2) was 40% of X0 (10% of λI), where X0 (λI) is the radiation (nuclear interaction) length. This increased to 60% (20%) by the time the Outer Tracker Technical Design Report (TDR) [2] was submitted in September 2001, due to various technological constraints. Additional material deteriorates the detection capability of electrons and photons, increases the multiple scattering of charged particles, and increases occupancies of the tracking stations. With a larger fraction of nuclear interaction length, more kaons and pions interact before traversing the complete tracking system. The number of reconstructed B mesons therefore decreases, even if the efficiency of the tracking algorithm is maintained high for those tracks that do traverse the full spectrometer. This leads to a noticeable loss in the number of reconstructed B mesons from many-body final states. For example, one of the most promising CP violation measurements, from Bs → DsK decays, requires five charged tracks (including one for tagging) to be reconstructed. For these reasons, an effort has been made to reduce the material budget back to the level at the time of the TP. The trigger is one of the biggest challenges of the LHCb experiment1. It is designed to distinguish minimum-bias events from events containing B mesons through the presence of particles with a large transverse momentum (pT) and the existence of secondary vertices. Events are first triggered by requiring at least one lepton or hadron with a pT exceeding 1 to 3 GeV/c (Level-0) reducing the event rate to 1MHz. It was realised that the robustness and efficiency of the second trigger level (Level-1) could be significantly improved by not only using information from the Vertex Locator (VELO), as done in the TP, but also adding pT information to tracks with a large impact parameter. This can be achieved by associating the high-pT calorimeter clusters and muons obtained at Level-0 to the tracks found in the VELO [3]. A complementary approach that is more efficient for hadrons is to get a rough pT estimate from the tracking. This requires the introduction of a small amount of magnetic field in the region of RICH1. The design of RICH 1 then has to be modified in order to protect its photon detectors from the field