Tritium retention in W plasma-facing materials : Impact of the material structure and helium irradiation

This article has an erratum: DOI 10.1016/j.nme.2020.100729Plasma-facing materials for next generation fusion devices, like ITER and DEMO, will be submitted to intense fluxes of light elements, notably He and H isotopes (HI). Our study focuses on tritium (T) retention on a wide range of W samples: first, different types of W materials were investigated to distinguish the impact of the pristine original structure on the retention, from W-coated samples to ITER-grade pure W samples submitted to various annealing and manufacturing procedures, along with monocrystalline W for reference. Then, He and He-D irradiated W samples were studied to investigate the impact on He-damages such as nano-bubbles (exposures in LHD or PSI-2) on T retention. We exposed all the samples to tritium gas-loading using a gentle technique preventing any introduction of new damage in the material. Tritium desorption is measured by Liquid Scintillation counting (LSC) at ambient and high temperatures (800 degrees C). The remaining T inventory is then measured by sample full dissolution and LSC. Results on T inventory on He exposed samples highlighted that in all cases, tritium desorption as a gas (HT) increases significantly due to the formation of He damages. Up to 1.8 times more T can be trapped in the material through a competition of various mechanisms, but the major part of the inventory desorbs at room temperature, and so will most likely not take part to the long-term trapped inventory for safety and operational perspectives. Unfortunately, investigation of "as received" industrial W (used for the making of plasma-facing materials) highlighted a strong impact of the pre existing defects on T retention: up to 2.5 times more T is trapped in "as received W" compared to annealed and polish W, and desorbs only at 800 degrees C, meaning ideal W material studies may underestimate T inventory for tokamak relevant conditions.Peer reviewe

Residual Stress Relaxation Induced by Mass Transport Through Interface of the Pd/SrTiO3

Metal interconnections having a small cross-section and short length can be subjected to very large mass transport due to the passing of high current densities. As a result, nonlinear diffusion and electromigration effects which may result in device failure and electrical instabilities may be manifested. Various thicknesses of Pd were deposited over SrTiO3 substrate. Residual stress of the deposited film was evaluated by measuring the variation of d-spacing versus sin2ψ through conventional X-ray diffraction method. It has been found that the lattice misfit within film and substrate might be relaxed because of mass transport. Besides, the relation between residual intrinsic stress and oxygen diffusion through deposited film has been expressed. Consequently, appearance of oxide intermediate layer may adjust interfacial characteristics and suppress electrical conductivity by increasing electron scattering through metallic films

A Single-Photon Imager Based on Microwave Plasmonic Superconducting Nanowire

Detecting spatial and temporal information of individual photons by using single-photon-detector (SPD) arrays is critical to applications in spectroscopy, communication, biological imaging, astronomical observation, and quantum-information processing. Among the current SPDs1,detectors based on superconducting nanowires have outstanding performance2, but are limited in their ability to be integrated into large scale arrays due to the engineering difficulty of high-bandwidth cryogenic electronic readout3-8. Here, we address this problem by demonstrating a scalable single-photon imager using a single continuous photon-sensitive superconducting nanowire microwave-plasmon transmission line. By appropriately designing the nanowire's local electromagnetic environment so that the nanowire guides microwave plasmons, the propagating voltages signals generated by a photon-detection event were slowed down to ~ 2% of the speed of light. As a result, the time difference between arrivals of the signals at the two ends of the nanowire naturally encoded the position and time of absorption of the photon. Thus, with only two readout lines, we demonstrated that a 19.7-mm-long nanowire meandered across an area of 286 {\mu}m * 193 {\mu}m was capable of resolving ~590 effective pixels while simultaneously recording the arrival times of photons with a temporal resolution of 50 ps. The nanowire imager presents a scalable approach to realizing high-resolution photon imaging in time and space

A new method to determine the elastopalstic properties of ductile materials by conical indentation

Based on load-displacement curves, indentation is widely used to extract the elastoplastic properties of materials. It is generally believed that such a measure is non-unique and a full stress-strain curve cannot be obtained using plural sharp and deep spherical indenters. In this paper we show that by introducing an additional dimensionless function of DA / A (the ratio of residual area to the area of an indenter profile) in the reverse analysis, the elastoplastic properties of several unknown materials that exhibit visually indistinguishable load-displacement curves can be uniquely determined with a sharp indentation

TRPA1 Mediates Mechanical Currents in the Plasma Membrane of Mouse Sensory Neurons

Mechanosensitive channels serve as essential sensors for cells to interact with their environment. The identity of mechanosensitive channels that underlie somatosensory touch transduction is still a mystery. One promising mechanotransduction candidate is the Transient Receptor Potential Ankyrin 1 (TRPA1) ion channel. To determine the role of TRPA1 in the generation of mechanically-sensitive currents, we used dorsal root ganglion (DRG) neuron cultures from adult mice and applied rapid focal mechanical stimulation (indentation) to the soma membrane. Small neurons (diameter <27 µm) were studied because TRPA1 is functionally present in these neurons which largely give rise to C-fiber afferents in vivo. Small neurons were classified by isolectin B4 binding

Sexual health of ethnic minority MSM in Britain (MESH project): design and methods

Background: Men who have sex with men (MSM) remain the group most at risk of acquiring HIV infection in Britain. HIV prevalence appears to vary widely between MSM from different ethnic minority groups in this country for reasons that are not fully understood. The aim of the MESH project was to examine in detail the sexual health of ethnic minority MSM living in Britain. Methods/Design: The main objectives of the MESH project were to explore among ethnic minority MSM living in Britain: (i) sexual risk behaviour and HIV prevalence; (ii) their experience of stigma and discrimination; (iii) disclosure of sexuality; (iv) use of, and satisfaction with sexual health services; (v) the extent to which sexual health services (for treatment and prevention) are aware of the needs of ethnic minority MSM. The research was conducted between 2006 and 2008 in four national samples: (i) ethnic minority MSM living in Britain; (ii) a comparison group of white British MSM living in Britain; (iii) NHS sexual health clinic staff in 15 British towns and cities with significant ethnic minority communities and; (iv) sexual health promotion/HIV prevention service providers. We also recruited men from two “key migrant” groups living in Britain: MSM born in Central or Eastern Europe and MSM born in Central or South America. Internet-based quantitative and qualitative research methods were used. Ethnic minority MSM were recruited through advertisements on websites, in community venues, via informal networks and in sexual health clinics. White and “key migrant” MSM were recruited mostly through Gaydar, one of the most popular dating sites used by gay men in Britain. MSM who agreed to take part completed a questionnaire online. Ethnic minority MSM who completed the online questionnaire were asked if they would be willing to take part in an online qualitative interview using email. Service providers were identified through the British Association of Sexual Health and HIV (BASHH) and the Terrence Higgins Trust (THT) CHAPS partnerships. Staff who agreed to take part were asked to complete a questionnaire online. The online survey was completed by 1241 ethnic minority MSM, 416 men born in South and Central America or Central and Eastern Europe, and 13,717 white British MSM; 67 ethnic minority MSM took part in the online qualitative interview. In addition 364 people working in sexual health clinics and 124 health promotion workers from around Britain completed an online questionnaire. Discussion: The findings from this study will improve our understanding of the sexual health and needs of ethnic minority MSM in Britain