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

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

Robustness for a single railway line: Analytical and simulation methods

[EN] Railway scheduling has been a significant issue in the railway industry. Over the last few years, numerous approaches and tools have been developed to compute railway scheduling. However, robust solutions are necessary to absorb short disruptions. In this paper, we present the robustness problem from the point of view of railway operators and we propose analytical and simulation methods to measure robustness in a single railway line. In the analytical approach, we have developed some formulas to measure robustness based on the study of railway line infrastructure topology and buffer times. In the simulation approach, we have developed a software tool to assess the robustness for a given schedule. These methods have been inserted in MOM (More information can be found at the MOM web page http://www.dsic.upv.es/users/ia/gps/MOM), which is a project in collaboration with the Spanish Railway Infrastructure Manager (ADIF). © 2012 Elsevier Ltd. All rights reserved.This work has been partially supported by the research project TIN2010-20976-C02-01 (Min. de Economia y Competitividad, Spain) and project PIRSES-GA-2011-294931 (FP7-PEOPLE-2011-IRSES).Salido Gregorio, MA.; Barber Sanchís, F.; Ingolotti Hetter, LP. (2012). Robustness for a single railway line: Analytical and simulation methods. Expert Systems with Applications. 39(18):13305-13327. https://doi.org/10.1016/j.eswa.2012.05.071S1330513327391

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