Thermal Performance of Insulating Cryogenic Pin Spacers

Following the proposal to introduce an actively cooled radiation screen (5-10 K) for the LHC machine, the design of the LHC cryostat foresees the need for spacers between the cold mass and the radiati on screen. The thermal impedance of the chosen material should be very high and the shape selected to withstrand the contact stress due to the displacements induced by the coll-down and warm-up transi ent. A cryogenic experiment dedicated to studying the thermal behaviour of several proposed spacers was performed at the cryogenics laboratory of CERN before choosing the one to be used for further i nvestigation on the LHC full-scale Cryostat Thermal Model [1] [2]. This paper describes a quantitative analysis leading to the choice of the spacer

A Microcryostat for Refrigeration at 1.8 K

A microcryostat has been developed in the Central Cryogenic Laboratory at CERN with the purpose of cooling a prototype beam loss monitor for the LHC, based on bolometry at 1.8 K. Its characteristics a re the very compact volume (some cm3 LHe) ensuring short cooldown-warmup times, and its low heat losses (~ 8 mW). The cryostat can be mounted on top of a small dewar through a rigid straight transfer line for continuous feeding

A Large-scale Test Facility for Heat Load Measurements down to 1.9 K

Laboratory-scale tests aimed at minimizing the thermal loads of the LHC magnet cryostat have gone along with the development of the various mechanical components. For final validation of the industrial design with respect to heat inleaks between large surfaces at different temperatures, a full-scale test cryostat has been constructed. The facility reproduces the same pattern of temperature levels as the LHC dipole cryostat, avoiding the heat inleaks from local components like supports and feedthroughs and carefully minimizing fringe effects due to the truncated geometry of the facility with respect to the LHC cryostats serial layout. Thermal loads to the actively cooled radiation screen, operated between 50 K and 65 K, are measured by enthalpy difference along its length. At 1.9 K, the loads are obtained from the temperature difference across a superfluid helium exchanger. On the beam screen, the electrical power needed to stabilize the temperature at 20 K yields a direct reading of the heat losses. Precise in-situ calibration is achieved by subcooling the thermal screen, thereby zeroing radiative heat loads. Minimizing fringe effects has been rewarded by a high precision measurement, yielding one of the more accurate quantifications to date of an industrial application of MLI. The influence of possible openings in the thermal screen is monitored both at the 1.9 K bath and with a radiation sensitive bolometer

Molecular-dynamics study of collision, implantation, and fragmentation of Ag7 on Pd(100)

By using embedded-atom-method interatomic potentials and molecular-dynamics simulations, we study the collision of a single Ag/sub 7/ cluster on the Pd(100) substrate, at impact energies in the direction perpendicular to the (100) surface E/sub 1/=20 eV (2.86 eV/atom) and E/sub 2/=95 eV (13.6 eV/atom). Our results indicate that implantation occurs at both impact energies, but it is more important at E/sub 2/. As opposed to what is shown experimentally, little fragmentation takes place for E/sub 1/, while the calculated cluster fragmentation is in good agreement with the experimental data for E/sub 2/

Cryogenic R&D at the CERN Central Cryogenic Laboratory

The Central Cryogenic Laboratory operates since many years at CERN in the framework of cryogenic R&D for accelerators and experiments. The laboratory hosts several experimental posts for small cryogen ic tests, all implemented with pumping facility for GHe and vacuum, and is equipped with a He liquefier producing 6.105 l/year, which is distributed in dewars. Tests include thermomechanical qualifica tion of structural materials, cryogenic and vacuum qualification of prototypes, evaluation of thermal losses of components. Some of the most relevant results obtained at the laboratory in the last yea rs are outlined in this paper

Thermal Characterization of the HeII LHC Heat Exchanger Tube

The LHC magnet cooling scheme is based on a HeII bayonet heat exchanger, which acts as a quasi isothermal heat sink. In order to assess the thermal performance of the oxygen free, annealed/cold worked copper tube, measurements of the total thermal conductance of the tube were performed in a laboratory set-up. This paper describes the experimental technique, which permits to separate the contributio n of the Kapitza interface resistance from the total transverse conductance. The influence of the surface treatment on the Kapitza resistance is also discussed

Quantitative and Qualitative tools for a physical education program that increases inclusion of children with disabilities

Aim: New technologies in PE provide children with the opportunity (a) to improve motor learning and self-efficacy, (b) model and stucture new prospective of the educational process (Clapham et al.,2015). The purpose of this study is to evalute and compare (a) the development of motor coordination of primary school\u2019s children in relation to BMI, (b) effects of strategies that utilize interactive video game technology (T0 vs T1), (c) enjoyment and physical selfefficacy between EG and CG. Methods: The study has been conducted in a primary school of Puglia, Italy. The sample includes 65 children, separated into two groups in relation to sex and BMI: EG (M: 22, age,10.09 \ub1 0.30; F:19, age 10.10 \ub1 0.31) and CG (M: 12, age, 10 \ub1 0.42; F: 12, age 10 \ub1 0.0). The experimental program consists of 10 lessons, using specialised interactive video game technology to point out unusual motor responses. For the CG has been used teaching styles of production. The following tests have been proposed before and after the intervention: MOBAK 5 (Hermann and Seelig 2016), PSP_C (physical self-efficacy) and PACES (enjoyment). Results: Besides the descriptive statistics (M \ub1 DS), T-test was used in order to highlights significative differences between T0-T1, indipendently from sex differences. The significance value was set at p\0.05. Data analysis revealed significative differences between EG for boys and girls about (a) Control Object and Self-Movement (p\0.05); (b) and physical self efficacy scale (p\0.05). Conclusions: The use of modern technologies and different teaching styles in PE promote motor learning and self-efficacy in children. The trail of new and different instruments are needed to enhance educational environments and develop intrinsic motivation to motor activities. References 1. Clapham, E.D. et al. (2015). The Physical Educator. 72,1, 102\u2013116. 2. Hermann, C. & Seelig, H. (2016). Sportwissenschaft

Heat Flow Measurements on LHC Components

The refrigeration and liquefaction capacity necessary to operate at 1.9 K the 27 km long string of superconducting magnets of the LHC has been determined on the basis of heat load estimates, including static heat inleaks from ambient temperature, resistive heating and dynamic beam-induced heat loads. At all temperature levels, the static heat inleaks determine at least one third of the total heat loads in nominal operating conditions of the machine. Design validation of individual cryocomponents therefore requires a correct estimate of the heat inleaks they induce at all temperature levels, in order not to exceed the allocated heat budget. This paper illustrates the measurements of heat inleaks for several cold components of the future machine, including insulating supports, radiation shields, multi-layer insulation, instrumentation current leads. Distinct methods to determine the heat flow are chosen, depending on the expected heat loads, the temperature range spanned by the heat intercepts, and the working conditions of the component itself

“CoVidentary”: An online exercise training program to reduce sedentary behaviours in children with type 1 diabetes during the COVID-19 pandemic

Aim: We explored the physical activity (PA) level and the variation in glycaemic control in children with type 1 diabetes (T1D) before and during the lockdown. Then, we proposed an online training program supported by sport-science specialists. Methods: Parents of children with T1D (<18 years) filled out an online survey. Anthropometric characteristics, PA, play, sport and sedentary time and the medical related outcomes were recorded. An adapted online program “Covidentary” was proposed through full-training (FT) and active breaks (AB) modality. Results: 280 youth (11.8 ± 3.3 years) were included in the analysis. We reported a decline in sport (-2.1 ± 2.1 h/week) and outdoor-plays (-73.9 ± 93.6 min/day). Moreover, we found an increase in sedentary time (+144.7 ± 147.8 min/day), in mean glycaemic values (+25.4 ± 33.4 mg/dL) and insulin delivery (71.8% of patients). 37% of invited patients attended the training program, 46% took part in AB and 54% in FT. The AB was carried out for 90% of the total duration, while the FT for 31%. Both types of training were perceived as moderate intensity effort. Conclusion: A decline of participation in sport activities and a subsequent increase of sedentary time influence the management of T1D of children, increasing the risk of acute/long-term complications. Online exercise program may contrast the pandemic's sedentary lifestyle

Morphology and evolution of size-selected metallic clusters deposited on a metal surface: Ag19+ / Pd(100)

We study size-selected deposition of Ag/sub 19//sup +/ clusters on Pd(100) at total kinetic energies of 20 and 95 eV using thermal energy atom scattering and molecular-dynamics simulations. Contrary to the case of Ag/sub 7/ where fragmentation is crucial to explain the data, the deposition leads at low temperature to noncompact structures localized around the impact point. We propose a model in which morphology changes take place between 200 and 300 K resulting in well-separated compact structures