Towards robust PICOSEC Micromegas precise timing detectors

The PICOSEC Micromegas (MM) detector is a precise timing gaseous detector consisting of a Cherenkov radiator combined with a photocathode and a MM amplifying structure. A 100-channel non-resistive PICOSEC MM prototype with 10x10 cm^2 active area equipped with a Cesium Iodide (CsI) photocathode demonstrated a time resolution below 18 ps. The objective of this work is to improve the PICOSEC MM detector robustness aspects; i.e. integration of resistive MM and carbon-based photocathodes; while maintaining good time resolution. The PICOSEC MM prototypes have been tested in laboratory conditions and successfully characterised with 150 GeV/c muon beams at the CERN SPS H4 beam line. The excellent timing performance below 20 ps for an individual pad obtained with the 10x10 cm^2 area resistive PICOSEC MM of 20 MOhm/sq showed no significant time resolution degradation as a result of adding a resistive layer. A single-pad prototype equipped with a 12 nm thick Boron Carbide (B4C) photocathode presented a time resolution below 35 ps; opening up new possibilities for detectors with robust photocathodes. The results made the concept more suitable for the experiments in need of robust detectors with good time resolution

Diamond: a chemical sensor’s best friend!

International audienceDiamond has been grown in some laboratories by either HPHT process or Plasma-Enhanced Chemical Vapor Deposition (MP-CVD) since a few decades. Single crystal diamond exhibits outstanding properties including a high optical transparency over a broad electromagnetic spectrum, high thermal conductivity approx. five times higher than copper, and acoustic wave velocity close to 19 000 m.s-1. It displays also remarkable mechanical properties with e.g. a Young’s modulus exceeding 1000 GPa along with high resistance to fracture, to name a few. Some of these properties remain also remarkable in its polycrystalline form when compare to most other materials. Furthermore, diamond can be doped e.g. with nitrogen or boron during growth, offering electrical properties from semiconducting to quasi-metallic regimes. When heavily doped with boron (~2.1021 cm-3), the so-called Boron Doped Diamond (BDD) electrodes become attractive electrodes featuring a high potential window > 3V in water and low double-layer capacitance. Moreover, diamond is extremely resilient to corrosion and more generally to chemical attacks. It is also biocompatible, which makes it very attractive for in-vivo sensing applications. Finally, the carbon nature of the diamond offers wide opportunities for surface grafting of chemical or biochemical functional groups through highly stable covalent carbon-carbon bonding. One can take advantage of these properties to enhance the analytical performances and stability of chemical/biochemical sensors and this has motivated our research over the last 15 years. Our work focuses mainly on polycrystalline diamond thin films that can be grown typically on 4 inches silicon substrates, thus offering access to some clean-room processes and potentially large-scale production. As examples, diamond based MEMS devices (microcantilevers, SAW sensors) take advantage both of the mechanical properties of diamond, along with steady carbon interface for convenient bio-functionalization. Our work here focused mainly on the detection of odorant molecules, using biomolecular receptors involved in olfaction in Nature as sensitive layers, including Odorant Binding Proteins (OBPs), Major Urinary Proteins (MUPs) and Olfactory Receptors (OR). Multisensor array instrumentations were developed around this concept, for applications ranging from breathe analysis to security applications. Beside, heavily doped diamond electrodes were developed successfully both as macro- and micro-electrodes for biomedical, pharmaceutical or foodstuff analysis applications. These applications benefit both from the high analytical performances of diamond electrodes in particular due to their low background signals and high reactivity, and high stability and reliability. BDD electrodes offer also significant advantages in electrochemiluminescence (ECL) techniques, which are being investigated for various applications ranging from foodstuff analysis to narcotics detection. A key benefit of BDD electrodes for all of the above applications is certainly that they can be electrochemically reactivated following fouling, sometimes directly in the analytical medium, to maintain high reactivity thus opening the way to reusable sensors and online monitoring

Diamond-based Resonators for Chemical Detection (chapter 18)

International audienceDiamond materials feature a wide range of outstanding chemical and physical properties, which have interested scientists over the years. The oldest applications of diamond are certainly related to its mechanical properties, in particular its hardness, which has facilitated its use for cutting and polishing, and in drilling tools. The chemical resilience of diamond associated with its interesting semiconducting properties has also been exploited for the development of radiation detectors. In this chapter we focus on chemical or biochemical sensing applications. Here, the extreme properties of diamond, being chemical, electrochemical, optical, acoustic, and so forth, have more recently prompted excitement for the development of innovative sensors. The various forms of diamond, from particles at the nanoscale to bulk single crystals, exhibit real potential to enhance both the sensing performance of the devices and their robustness, as well as their reliability in field-operating conditions. A wide range of diamond-based chemical sensors have been reported in the form of solid state semiconductor sensors, field effect transistors, electrodes, etc. both in the gas phase and in the liquid phase. Such sensors have found various applications in environmental monitoring, security and medical diagnostics. Two types of transducer technologies, namely acoustic wave devices and cantilevers, are particularly interesting because they offer the possibility of high sensitivity detection of a wide range of analytes at a potentially low cost with a high level of miniaturisation. This chapter gives an insight into how these technologies may benefit from the exceptional assets of diamond materials through a few examples, ranging from DNA detection to artificial olfaction

Flexible soft diamond implant

Flexible implant (1) for electrically recording or stimulating a nerve structure, said flexible implant comprising: a first layer (5) of electrically insulating diamond; an electrode (3) of electrically conductive doped diamond, in contact with the first layer (5) of electrically insulating diamond; an electrically conductive layer (2) in contact with the electrode (3) and the first layer (5), so as to define a conductive track for the electrode (3); and a second layer (6) of electrically insulating diamond, at least in contact with the electrically conductive layer (2) and a remaining portion of the first layer (5), all of the above arranged such that: electrically insulating diamond/electrically conductive doped diamond sealing is provided at the electrode (3) by resumption of epitaxial growth; and the electrically conductive layer (2) is encapsulated by the electrode (3), the first layer (5) and the second layer (6), at the electrode (3) and over the entirety of the remaining surface thereof except over an area defining an electrical contact. The implant (1) has two faces, namely: a front face (11) comprising one of the two layers of electrically insulating diamond, open locally, providing access to the electrode (3) and to the area defining an electrical contact; and a rear face (12) comprising the other of the two layers of electrically insulating diamond

Odorant binding proteins based sniffing device for detection of tobacco

International audienceAffinity constants for a selection of Odorant Binding Proteins (OBPs) from mammalian and insect sources were determined toward volatile signature compounds from tobacco in the liquid phase using a fluorescent probe and competitive ligand binding. The most sensitive proteins were selected and these were immobilised on to diamond coated Surface Acoustic Wave (SAW) sensors to construct an array of eight sensors to detect tobacco volatiles. The system was then tested for its ability to detect vapours of tobacco itself as well as other markers. The results were positive, a pattern of responses across the array was observed as each sensor gave a specific response towards different analytes. To determine the stability of these OBP biosensors over time, the sensors were repeatedly exposed to pulses of saturated D(+)-carvone vapour over three months. Little degradation was observed and these sensors were able to sensitively detect the target analytes after this period

BDD electrodes modified with metal nano-catalysts for coffee discrimination in real samples

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Diamond-based active antireflective optical windows with omniphobic properties

International audienceInfrared windows are among the key optical components in infrared detection systems with military and civil applications, including land and sea surveillance systems, airborne sensors for the detection of threats, cameras of autonomous trains, etc. However, the optical properties of these systems, commonly used in severe environmental conditions, can be altered due to the formation of biofilms or contaminants deposition. To protect these systems, we propose to extend the functionality of these optical surfaces, by developing robust « active » diamond windows allowing them to be fitted with anti-dirt. Indeed, diamond is a promising material. In addition to having very good mechanical properties, it is transparent in the range from visible to long-wave infrared and it is an excellent thermal conductor1. Once boron-doped, diamond has remarkable electrochemical properties2, including the capacity of electrochemical auto-cleaning of its surface and therefore anti-dirt properties. It is known that boron doping enhances the electrical conductivity of diamond. Thus, the electrochemical character of the boron-doped diamond (BDD) is strongly dependent on the boron doping level. However, the high boron content also affects the optical transmission in diamond.The present work aims to design and build active diamond optical windows, combining anti-reflective, electrochemical auto-cleaning. For this need, we will investigate the boron doping level necessary to achieve the electrochemical auto-cleaning properties of the diamond surface without deteriorating the optical transmission of the windows. Thus, we will focus on (1) optimizing the growth of doped diamond films using microwave plasma-assisted chemical vapor deposition by taking into account the application constraints and (2) understanding the phenomena at stake during the self-cleaning mechanisms of these so-called « active windows »