Development of diamond based KIDs

Kinetic Inductance Detectors (KIDs) have proven themselves as a very versatile cryogenic detector technology capable of applications in various fields due to their flexibility of design, sensibility and ease of production. We have recently proposed a polarization sensitive Lumped Elements KID as sensor for an innovative polarimetric diagnostics based on quantum cascade lasers (QCL) for application in the nuclear fusion. Each detector unit is composed by 4 pixels arranged at the vertices of a square, each pixels being sensible to only one polarization direction. The current system is based on niobium nitride (NbN) superconductor over High Resistivity Silicon (HRSi) substrate. Such material delivers good performances but its relatively high dielectric constant and loss tangent lead to increased substrate losses. Using a transparent substrate may improve this aspect and also the radiation resistance of such devices. Diamond is the substrate of choice, being a material already widely studied and used in the fusion environment as high power microwave window, due to its outstanding optical and mechanical performances. In this work we present the preliminary design study for a diamond based Kinetic Inductance Detector and subsequent characterization measurements of the first prototypes

Distal thoracic oesophageal perforation secondary to blunt trauma: Case report

BACKGROUND: Traumatic perforation of the distal oesophagus due to blunt trauma is a very rare condition and is still associated with a significant morbidity and mortality. This is further exacerbated by delayed diagnosis and management as symptoms and signs are often masked by or ascribed to more common blunt thoracic injuries. CASE REPORT: We present a case of a distal oesophageal perforation, secondary to a fall from a third storey window, which was masked by concomitant thoracic injuries and missed on both computed tomography imaging and laparotomy. The delay in his diagnosis significantly worsened the patient's recovery by allowing the development of an overwhelming chest sepsis that contributed to his death. CONCLUSION: Early identification of an intrathoracic oesophageal perforation requires deliberate consideration and is essential to ensure a favorable outcome. Treatment should be individualised taking into account the nature of the oesophageal defect, time elapsed from injury and the patient's general condition

The electronic structure of Amorphous Carbon Nanodots

We have studied hydrogen-passivated amorphous carbon nanostructures with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties. Amorphous structures were first constructed using periodic calculations in a melt/quench protocol. Pure periodic amorphous carbon structures and their counterparts doped with nitrogen and/or oxygen feature large electronic band gaps. Surprisingly, descriptors such as the elemental composition and the number of sp³-atoms only influence the electronic structure weakly. Instead, the exact topology of the sp²-network in terms of effective conjugation defines the band gap. Amorphous carbon nanodots of different structures and sizes were cut out of the periodic structures. Our calculations predict the occurrence of localized electronic surface states, which give rise to interesting effects such as amphoteric reactivity and predicted optical band gaps in the near-UV/visible range. Optical and electronic gaps display a dependence on particle size similar to that of inorganic colloidal quantum dots

Characterization of Boron-doped diamond and r-plane sapphire for plasma diagnostics in future nuclear fusion reactors -A survey of electrical and dielectric properties

p-Boron-doped polycrystalline CVD diamond samples were produced and delivered by the German company Diamond Materials in Freiburg (Germany). In a first step, main properties of this candidates for diagnostic and/or heating windows in future nuclear fusion reactors were investigated. By a special measurement technique, it was possible to determine the Boron doping concentration in Diamond by measurement of the resistive properties by using the van der Pauw method. So prepared, an irradiation campaign with neutrons and/or heavy ions on these samples will follow. The second material investigated, was r-plane single crystalline sapphire. For the first characterization the dielectric properties of a 3*-wafer in dependency of the frequency in a FABRY-PEROT resonator setup was performed. Also, this is the preparation for the next irradiation experiments in this project

Basic considerations for fracture toughness measurements of MPA CVD diamond to be used in nuclear fusion

In nuclear fusion, Microwave Plasma Assisted (MPA) Chemical Vapour Deposition (CVD) polycrystalline diamond is the only material allowing for transmission of high power microwave beams (1-2 MW) in long-pulse gyrotron operations. The reason lies in the combination of extraordinary thermal, mechanical and optical properties of diamond, which is used in the shape of disks having thickness of 1 to 2 mm for windows. Being diamond a brittle material, failure to fracture is the main failure mode. Accordingly, an appropriate mechanical characterization is required as diamond plays a major safety role in fusion machines. Due to limited body of work in literature, fracture toughness measurements have to be first carried out for this material and then a design criterion for structural integrity assessment has to be applied. In this work, the preliminary activities aiming to define the optimum experimental measurement method of fracture toughness for thin diamond samples are shown and discussed. An outlook to the next steps is also given