Microplastics (MPs) have gained a high degree of public interest since they are associated with the global release of plastics into the environment. Various studies have confirmed the presence of MPs throughout the food chain. However, information on the ingestion of MPs via the consumption of many commonly consumed foods like dairy products are scarce due to the lack of studies investigating the “contamination” of this food group by MPs. This lack of occurrence data is mainly due to the absence of robust analytical methods capable of reliably quantifying MPs with size < 20 µm in foods. In this work, a new methodology was developed to accurately determine and characterize MPs in milk-based products using micro-Raman (μRaman) technology, entailing combined enzymatic and chemical digestion steps. This is the first time that the presence of relatively low amounts of small-sized MP (≥ 5 µm) have been reported in raw milk collected at farm just after the milking machine and in some processed commercial liquid and powdered cow’s milk products.
Superconducting radiofrequency (SRF) cavities that could provide a higher quality factor as well as a higher operational accelerating gradient at an affordable cost are in high demand for the future generation of particle accelerators. This study aims to demonstrate the potential of Nb3Sn as material of choice for such SRF applications. Due to its brittle nature, the only way to produce an Nb3Sn SFR cavity is to synthesise a thin layer inside a cavity made of niobium or copper. In this work, direct current magnetron sputtering using a stoichiometric target of Nb3Sn was employed to produce films on copper samples. Assessment of the morphology, microstructure and superconducting properties were performed in order to ensure that this approach is suitable for SRF applications. The potential of the method is proven by obtaining films, which exhibit a crack-free surface, dense morphology and critical temperatures (Tc) up to 16 K. The essential properties of the films have also been investigated with respect to the deposition and annealing conditions. The use of krypton as working gas during deposition increases the atomic percent of Sn in the film compared to argon. However, in contrast to argon, higher krypton pressures reduce the atomic percent of Sn. It was also found that long-lasting high-temperature annealing leads to higher superconducting critical temperatures due to an increased crystallographic order. Particular attention was given to the influence of the copper substrate on the film growth as well as the microstructural and superconducting characteristics. We discuss the main constraints introduced by the copper substrate, such as copper interdiffusion during annealing, lattice mismatch and difference in thermal expansion coefficients and methods to overcome them.
A target assembly, composed of several collinear molybdenum (Mo)‐based and tungsten (W)‐based cylindrical blocks, will reside in the core of the new beam dump facility (BDF) being designed at the European Laboratory for Particle Physics (CERN). The target blocks will be protected from the cooling water erosion‐corrosion by a tantalum (Ta)‐based cladding. In order to obtain intimate and reliable bonding between the several cylinders composing each target block and with the cladding, hot isostatic pressing (HIP) assisted diffusion bonding technique was explored. Several down‐scaled target block prototypes were conceived to investigate the bondings. Starting from the previously gained experience in Ta cladding on W from neutron spallation targets, here, we present results on Ta cladding on TZM (Mo alloy), Ta2.5W (Ta alloy) cladding on TZM and W, and on TZM to TZM and W to W self‐bondings. The resulting interfaces were systematically characterized with electron microscopy, tensile testing, and thermal conductivity measurements. Successful diffusion bonding was achieved for all the studied material combinations, resulting in homogeneous and defect‐free interfaces, strong interfacial bondings, and limited interfacial thermal contact resistance. The HIP parameters and diffusion interfacial aids were of great importance to optimize the interface and bulk material properties.
The Beam Dump Facility (BDF) project is a proposed general-purpose facility at CERN, dedicated to beam dump and fixed target experiments. In its initial phase, the facility is foreseen to be exploited by the Search for Hidden Particles (SHiP) experiment. Physics requirements call for a pulsed 400 GeV/c proton beam as well as the highest possible number of protons on target (POT) each year of operation (4.0 · 10 13 /year), in order to search for feebly interacting particles. The target/dump assembly lies at the heart of the facility, with the aim of safely absorbing the full high intensity Super Proton Synchrotron (SPS) beam, while maximizing the production of charmed and beauty mesons. High-Z materials are required for the target/dump, in order to have the shortest possible absorber and reduce muon background for the downstream experiment. The design of the production target is one of the most challenging aspects of the facility design, due to the high energy and power density deposition that are reached during operation, and the resulting thermomechanical loads. The nature of the beam pulse induces very high temperature excursions between pulses (up to 100 • C), leading to considerable thermally-induced stresses and long-term fatigue considerations. The high average power deposited on target (305 kW) creates a challenge for heat removal. During the BDF facility Comprehensive Design Study (CDS), launched by CERN in 2016, extensive studies have been carried out in order to define and assess the target assembly design. These studies are described in the present contribution, which details the proposed design of the BDF production target, as well as the material selection process and the optimization of the target configuration and beam dilution. One of the specific challenges and novelty of this work is the need to consider new target materials, such as a molybdenum alloy (TZM) as core absorbing material and Ta2.5W as cladding. Thermo-structural and fluid dynamics calculations have been performed to evaluate the reliability of the target and its cooling system under beam operation. In the framework of the target comprehensive design, a preliminary mechanical design of the full target assembly has also been carried out, assessing the feasibility of the whole target system.
For antiproton production at CERN, high‐energy (26 GeV/c), intense, and short proton beams are impacted into a small rod—target core—made of a dense metal. Temperature rises in the order of 2000°C, and subsequent dynamic stresses of several gigapascals are induced in this rod every time it is impacted by the primary proton beam. Several R&D activities have been launched with the goal of proposing and manufacturing a new design of such device (named AD‐Target). A summary of these activities is presented, including the last design stage, which involves the manufacturing and testing of six real‐scale prototypes of the new target design. These prototypes (named PROTAD) consist of air‐cooled Ti‐6Al‐4V assemblies filled by matrices made of isostatic graphite or expanded graphite (EG), containing target cores made of small rods with different diameters (from 2 to 10 mm) of multiple grades of Ta, Ta2.5W, and Ir.
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