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 Experiment. Physics requirements call for a pulsed400GeV/cproton beam as well as the highest possible number of protons on target each year of operation (4.0×1019/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 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 to100°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, 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 as core absorbing material and Ta2.5W as cladding. Thermostructural 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.
The beam dump facility (BDF) is a project for a new facility at CERN dedicated to high intensity beam dump and fixed target experiments. Currently in its design phase, the first aim of the facility ...is to search for light dark matter and hidden sector models with the Search for Hidden Particles (SHiP) experiment. At the core of the facility sits a dense target/dump, whose function is to absorb safely the400GeV/cSuper Proton Synchrotron (SPS) beam and to maximize the production of charm and beauty mesons. An average power of 300 kW will be deposited on the target, which will be subjected to unprecedented conditions in terms of temperature, structural loads and irradiation. In order to provide a representative validation of the target design, a prototype target has been designed, manufactured, and tested under the SPS fixed-target proton beam during 2018, up to an average beam power of 50 kW, corresponding to 350 kJ per pulse. The present contribution details the target prototype design and experimental setup, as well as a first evaluation of the measurements performed during beam irradiation. The analysis of the collected data suggests that a representative reproduction of the operational conditions of the beam dump facility target was achieved during the prototype tests, which will be complemented by a postirradiation examination campaign during 2020.
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, 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 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.
The Beam Dump Facility (BDF) is a project for a new facility at CERN dedicated to high intensity beam dump and fixed target experiments. Currently in its design phase, the first aim of the facility ...is to search for Light Dark Matter and Hidden Sector models with the Search for Hidden Particles (SHiP) experiment. At the core of the facility sits a dense target/dump, whose function is to absorb safely the 400 GeV/c Super Proton Synchrotron (SPS) beam and to maximize the production of charm and beauty mesons. An average power of 300 kW will be deposited on the target, which will be subjected to unprecedented conditions in terms of temperature, structural loads and irradiation. In order to provide a representative validation of the target design, a prototype target has been designed, manufactured and tested under the SPS fixed-target proton beam during 2018, up to an average beam power of 50 kW, corresponding to 350 kJ per pulse. The present contribution details the target prototype design and experimental setup, as well as a first evaluation of the measurements performed during beam irradiation. The analysis of the collected data suggests that a representative reproduction of the operational conditions of the Beam Dump Facility target was achieved during the prototype tests, which will be complemented by a Post Irradiation Examination campaign during 2020.
The electrical behaviour of CdTe crystals is controlled by background impurity concentrations and stoichiometric deviations. The stoichiometry control is particularly important in vapour growth, in ...that even extremely reduced deviations in the starting polycrystalline charge give rise to large increases in excess-component partial pressure, thus limiting the crystal growth rate. A novel procedure was developed for preparing polycrystalline CdTe with highly reduced off-stoichiometry. The method is based on a heat treatment of the CdTe charge and on the control of the flux of the Cd and Te
2 vapours through an effusion hole. In situ monitoring of the vapour pressures, and thus of the stoichiometry of the charge was demonstrated. It was shown that the monitoring of the Te
2-partial pressure with time allows to interrupt the process when the desired stoichiometric ratio (Cd/Te≈1 or ≠1) has been reached. Nominally undoped single crystals could be grown from vapour and melt, with a resistivity of 10
8–10
9
Ω×cm, when the Cd/Te atomic ratio was close to unity. A correlation between resistivity and Te
2-partial pressure is reported and discussed.
In the frame of a research project aimed at preparing high-resistivity CdTe single crystals, the authors have developed as a first step, a new, low cost, fast technique which allows to synthesize ...from the elements polycrystalline CdTe with very low stoichiometric deviations and with a level of background impurities much lower than usually available in commercial materials. The material obtained by this technique as will be described and discussed, appears especially suitable for preparing source charges for physical vapour transport growth experiments.
Urea is an excellent nonlinear optical (NLO) medium. However, growth of large high-quality crystals for practical use still remains a challenge due to its unfavourable growth properties. Improved ...crystalline and optical quality could be expected in derivatives of urea. In this contribution we report on the growth of urea and its derivatives: monomethylurea (NMU), 1,1-dimethylurea (1,1-DMU), and 1,3-dimethylurea (1,3-DMU). Satisfactory quality and reasonable size of both urea and monomethylurea crystals have been achieved. Some evaluation of the quality of the grown crystals is reported. This work shows that NMU exhibits a better crystal habit than urea does, while preserving almost the same transparency window. This would suggest that NMU is a potentially promising material in nonlinear optical applications.
Monomethylurea (NMU), a methyl derivative of urea, has been focused recently as promising nonlinear optics (NLO) material. We grew NMU using long thin seeds capped at both ends. This kind of growth ...was successful, and gave crystals of high structural and optical quality. However, the useful cross section was limited due to the presence of a defected region surrounding the seed. For this reason, we tested an alternative growth method by which larger (25 × 25 mm) cross sections have been obtained. Here we report on this growth procedure, on morphological studies, and on some linear and nonlinear optical characterizations.
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