Variabilités des descripteurs physiques, chimiques et biologiques d'un réservoir de stokage (lagunage mixte, en Slimane - Maroc)

L'étude des variations des descripteurs physiques, chimiques et biologiques des eaux d'un réservoir de maturation du lagunage mixte (Ben Slimane, Maroc), a montré une augmentation des valeurs de certaines variables (oxygène dissous, transparence) après le 36ème jour de rétention en raison d'une remise en solution.A 36 jours de rétention, la chute des teneurs de la DBO5, de la DCO, des composés azotés (NH4+, NO3-, NTK) et phosphorés (PO43-, PT), et l'augmentation du pH, de l'oxygène dissous et de la transparence laissent présager une maturation à cette date de mesure. Les densités planctoniques enregistrées à ce niveau sont les plus basses.Au-delà de ce stade de maturation, le phytoplancton prolifère avec dominance d'Euglena viridis qui montre un pic de densité (4,1.106 Individus/m3) le 81ème jour. Le début de sa phase exponentielle de croissance est observé à partir du 18ème jour de maturation. La densité cellulaire est ensuite atténuée vraisemblablement en raison de la diminution de la charge organique (DBO5 et DCO) après le 81ème jour et de l'intensité de broutage par le zooplancton herbivore surtout Acanthocyclops robustus qui montre son maximum de croissance le 138ème jour.Après le 81ème jour de maturation, Euglena viridis est remplacée par deux espèces de Chlorophycées (Pediastrum boryanum et Ankyra judai) dont le maximum de densité (91% de la densité algale totale) est atteint le 138ème jour. La prolifération de ces espèces coïncide avec des valeurs en nitrates dépassant 10,6 mg N/L.A la fin de cette période d'étude (le 138ème jour), le zooplancton est à sa prolifération maximale (106 individus/m3). Il est dominé par Acanthocyclops robustus avec présence de Nauplii et de Daphnia magna. Les Rotifères présents depuis le début de la maturation disparaissent à 138 jours de rétention. L'étude bactériologique a révélé un rendement épuratoire remarquable atteignant 100% pour les coliformes fécaux et les streptocoques fécaux.A study of physical, chemical and biological descriptors of the water in the storage reservoir of a combined stabilization pond (Ben Slimane, Morocco), during maturation, showed an improvement of the purification output for some variables after 36 days of retention. Such an environment, rich with a range of different nutrients, allowed an optimal development of plankton characterized by a high species diversity that decreased with time. Zooplankton development seemed to be limited by poor phytoplankton biomass. However, trophic factors such as nutrients and temperature affected the evolution of planktonic species.After 36 days of retention, the decrease in BOD5, COD, NH4+, NO3-, total Kjeldahl nitrogen (TNK), PO43-, total phosphorus (TP), and the increase in pH, dissolved oxygen and transparency, suggested that maturation had been reached at this level. Simultaneously, phyto- and zooplankton were present in low densities. Nevertheless, beyond this stage of maturation, phytoplankton proliferation occurred, dominated by Euglena viridis whose exponential phase of growth began at the 18th day of maturation and reached a maximum density after 81 days (4.1x106 individus/m3). A low proportion of Chlorophyte species was observed, represented by Pediastrum boryanum and Ankyra judai. The zooplankton community was dominated by two species of Cladocera (Daphnia magna and Diaphanosoma sp).The increase in Euglena viridis density up to 81 days coincided with zooplanktonic proliferation constituted exclusively by Rotifers (Brachionus calyciflorus and Polyarthra remata). At 111 days of retention, the zooplankton community consisted of Copepods (Acanthocyclops robustus), which reappeared at this stage, as well as Nauplii Cladocera (Daphnia magna) and residual Rotifers (Brachionus calyciflorus and Polyarthra remata). The remarkable decrease in Euglena density on day 111 and their complete disappearance on day 138 was probably linked to grazing by herbivorous zooplankton and to low organic matter concentrations. Euglena viridis was replaced by two Chlorophytes (Pediastrum boryanum and Ankyra judai) reaching their maximum density (91% of total algal density) on day 138. The proliferation of these species coincided with values exceeding 10.6 mg N/L. Zooplankton were dominated by Acanthocyclops robustus with the presence of Nauplii and Daphnia magna (106individuals/m3). Rotifers were present since the beginning of the maturation, but were absent by 138 days of retention.The qualitative and quantitative changes in phyto- and zooplankton result from factors that control the growth and the loss of these populations. A low growth rate can lead to biomass accumulation if the growth exceeds loss. On the other hand, a low and stable biomass can result from a high growth rate that is compensated by important losses. Zooplankton grazing and algal sedimentation, which are the two main mechanisms related to phytoplankton decline, are two selective processes (POURRIOT et al., 1982). In stabilization ponds, food chains are established that allow water clarity and minimize algal proliferation. The bacteriological study showed a remarkable purification, with reductions reaching 100% for faecal coliforms and faecal Streptococcus

Radiation Tolerance of CMOS Monolithic Active Pixel Sensors with Self-Biased Pixels

CMOS Monolithic Active Pixel Sensors (MAPS) are proposed as a technology for various vertex detectors in nuclear and particle physics. We discuss the mechanisms of ionizing radiation damage on MAPS hosting the the dead time free, so-called self bias pixel. Moreover, we discuss radiation hardened sensor designs which allow operating detectors after exposing them to irradiation doses above 1 Mra

A fast monolithic active pixel sensor with pixel level reset noise suppression and binary outputs for charged particle detection

In order to develop precision vertex detectors for the future linear collider, fast active monolithic active pixel sensors are studied. Standard CMOS 0.25 mum digital process is used to design a test chip which includes different pixel types, column-level discriminators and a digital control part. In-pixel amplification is implemented together with double sampling. Different charge-to-voltage conversion factors were obtained using amplifiers with different gains or diode sizes. Pixel architectures with DC and AC coupling to charge sensing element were proposed. As far, hits from conversion of 35Fe photons were registered for the DC-coupled pixel. Double sampling is functional and allows almost a complete cancellation if fixed pattern noise

Optimization of Tracking Performance of CMOS Monolithic Active Pixel Sensors

CMOS Monolithic Active Pixel Sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. In these devices, a thin, moderately doped, undepleted silicon layer is used as the active detector volume with the readout electronics implemented on top of it. Recently, a new MAPS prototype was fabricated using the AMS 0.35 $mu$m OPTO process, featuring a thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particle beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry was also fabricated and tested. Each pixel circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode, followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration independently of full frame readout time and strongly reduces the pixel-to-pixel output signal dispersion. First measurements using this structure are also presented

A vertex detector for the International Linear Collider based on CMOS sensors

The physics programme at the International Linear Collider (ILC) calls for a vertex detector (VD) providing unprecedented flavour tagging performances, especially for c-quarks and τ leptons. This requirement makes a very granular, thin and multi-layer VD installed very close to the interaction region mandatory. Additional constraints, mainly on read-out speed and radiation tolerance, originate from the beam background, which governs the occupancy and the radiation level the detector should be able to cope with. CMOS sensors are being developed to fulfil these requirements. This report addresses the ILC requirements (highly related to beamstrahlung), the main advantages and features of CMOS sensors, the demonstrated performances and the specific aspects of a VD based on this technology. The status of the main R&D directions (radiation tolerance, thinning procedure and read-out speed) are also presented

CMOS pixel sensor development: a fast read-out architecture with integrated zero suppression

International audienceCMOS Monolithic Active Pixel Sensors (MAPS) have demonstrated their strong potential for tracking devices, particularly for flavour tagging. They are foreseen to equip several vertex detectors and beam telescopes. Most applications require high read-out speed, which imposes sensors to feature digital output with integrated zero suppression. The most recent development of MAPS at IPHC and IRFU addressing this issue will be reviewed. The design architecture, combining pixel array, column-level discriminators and zero suppression circuits, will be presented. Each pixel features a preamplifier and a correlated double sampling (CDS) micro-circuit reducing the temporal and fixed pattern noises. The sensor is fully programmable and can be monitored. It will equip experimental apparatus starting data taking in 2009/2010

A ten thousand frames per second readout MAPS for the EUDET beam telescope

Designed and manufactured in a commercial CMOS 0.35 μm OPTO process for equipping the EUDET beam telescope, MIMOSA26 is the first reticule size pixel sensor with digital output and integrated zero suppression. It features a matrix of pixels with 576 rows and 1152 columns, covering an active area of ~224 mm2. A single point resolution of about 4 μm was obtained with a pixel pitch of 18.4 μm. Its architecture allows a fast readout frequency of ~10 k frames/s. The paper describes the chip design, test and major characterisation outcome

Infrastructure for Detector Research and Development towards the International Linear Collider

The EUDET-project was launched to create an infrastructure for developing and testing new and advanced detector technologies to be used at a future linear collider. The aim was to make possible experimentation and analysis of data for institutes, which otherwise could not be realized due to lack of resources. The infrastructure comprised an analysis and software network, and instrumentation infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture

Status of the Micro Vertex Detector of the Compressed Baryonic Matter Experiment

The CBM experiment will investigate heavy-ion collisions at beam energies from 8 to 45 AGeV at the future accelerator facility FAIR. The goal of the experiment is to study the QCD phase diagram in the vincinity of the QCD critical point. To do so, CBM aims at measuring rare probes among them open charm. In order to identify those rare and short lived particles despite the rich combinatorial background generated in heavy ion collisions, a micro vertex detector (MVD) providing an unprecedented combination of high rate capability and radiation hardness, very light material budget and excellent granularity is required. In this work, we will discuss the concept of this detector and summarize the status of the R&D

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal