Engineering the cooling and ventilation for the LHC

Early in the LHC-project, a decision was made to complete in-house, as much of the engineering for the new cooling and ventilation systems as was practicable. This is achieved using the competence of resident (CERN staff) engineers for the studies, project management, on-site installation, supervision, etc. The documentation has however, been compiled using the format of tender drawings in the technical office by industrial service personnel. This model, adopted by the Cooling and Ventilation (CV) group is attractive from the viewpoint of conservation of “know-how” within CERN. The main difficulty is however, to be able to absorb such an important project within available manpower. This paper will revisit the arguments behind this method as well as summarize the results to date. Finally, the author will outline other methods (followed by other groups within the project), for a comparison with the model chosen by ST/CV

Co-generation at CERN: Beneficial or not?

A co-generation plant for the combined production of electricity and heat has recently been installed on the CERN Meyrin site. This plant consists of: a gas turbine generator set (GT-set), a heat recovery boiler for the connection to the CERN primary heating network, as well as various components for the integration on site. A feasibility study was carried out and based on the argument that the combined use of natural gas -available anyhow for heating purposes- gives an attractively high total efficiency, which will, in a period of time, pay off the investment. This report will explain and update the calculation model, thereby confirming the benefits of the project. The results from the commissioning tests will be taken into account, as well as the benefits to be realized under the condition that the plant can operate undisturbed by technical setbacks which, incidentally, has not been entirely avoided during the first year of test-run and operation

New Trends in the Outsourcing of Maintenance/Operation Services

The contracting-experience of maintenance/operation work in our group can today be considered as rich with the first generation of contract implemented more than 15 years ago. The incumbent contract was started in 1997, so it is now into its 4th year. Certain improvements that have already been implemented has had a large impact on our contract culture e.g. performance indicators. The next re-tendering is now approaching and with this borne in mind, the author will discuss through various sections of this report the following main points: firstly, an overview of the trends today in this area; secondly, comparing these trends with implemented practices; and finally, what can be future development in the outsourcing of the maintenance/operation of the Cooling & Ventilation services

Cooling and ventilation for the LHC: status report

For the LHC project, investments for cooling and ventilation will exceed 100 MCHF over a period of six years. This report contains an outline of the group's mandate within the project, as well as a summary of the main design parameters. Furthermore, the author will explain the present status of the cooling and ventilation schedule, with some milestones already achieved and others soon ahead. In fact, two important construction projects prior to the civil engineering building sites were already successfully completed before the end of 1997. As the service infrastructure for the LHC needs to match recovered structures from the LEP project, the author will also discuss and compare the technical content in the light of optimized expenses, design parameters and constraints, as well as new and adaptable technologies and methods

ST Implications in the CNGS Project

The CNGS project concerns the construction of a neutrino beam facility (CNGS = CERN Neutrino beam to Gran Sasso). A 450 GeV proton beam will be extracted from the SPS accelerator. This proton beam will hit a target a few hundred metres downstream from the extraction point (BA4). In the debris of the proton beam we will find pions which continue down a 1000 m, evacuated tunnel and a fraction of which decay into a neutrino beam. After this decay tunnel (1.1 km), a 'hadron stop' will separate the neutrinos, after which they will resume their journey down to a detector pit, outside Rome (Gran Sasso). The CERN facility has a total length of approximately 3 km. The ST division has an important share in the construction work, both of the above-mentioned tunnels as well as of all other infrastructure services, and this work concerns most of the groups in the division. This report will outline the technical design of the facility and explain how we, in the ST division, are involved in the project. The CERN council approved the project on 17 December 1999 for a scheduled commissioning in 2005

Process Analysis of the CV Group's Operation

This report will give an explanation of the internal reorganization that has been done because of the necessity to optimize operation in the cooling and ventilation group. The basic structure for the group was defined at the end of 1998. We understood then that change was needed to accommodate the increased workload due to the LHC project. In addition, we face a relatively large turnover of personnel (retirements and some recruitment) with related integration issues to consider. We would also like to implement new approaches in the management of both operations and maintenance. After some running-in problems during the first half of 1999, we realized that much more could be gained with the analysis and the definition and documenting of each single function and generic activity within the group. The authors will explain how this analysis was carried out and give some feedback of the outcome, so far

Influence of annealing parameters on the ferromagnetic properties of optimally passivated (Ga,Mn)As epilayers

The influence of annealing parameters - temperature and time - on the magnetic properties of As-capped (Ga,Mn)As epitaxial thin films have been investigated. The dependence of the transition temperature (Tc) on annealing time marks out two regions. The Tc peak behavior, characteristic of the first region, is more pronounced for thick samples, while for the second (`saturated') region the effect of the annealing time is more pronounced for thin samples. A right choice of the passivation medium, growth conditions along with optimal annealing parameters routinely yield Tc-values of ~ 150 K and above, regardless of the thickness of the epilayers.Comment: 5 pages, 3 figure

Electronic structure and chemical bonding in Ti2AlC investigated by soft x-ray emission spectroscopy

The electronic structure of the nanolaminated transition metal carbide Ti2AlC has been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Ti L, C K and Al L emission spectra are compared with calculated spectra using ab initio density-functional theory including dipole matrix elements. The detailed investigation of the electronic structure and chemical bonding provides increased understanding of the physical properties of this type of nanolaminates. Three different types of bond regions are identified; the relatively weak Ti 3d - Al 3p hybridization 1 eV below the Fermi level, and the Ti 3d - C 2p and Ti 3d - C 2s hybridizations which are stronger and deeper in energy are observed around 2.5 eV and 10 eV below the Fermi level, respectively. A strongly modified spectral shape of the 3s final states in comparison to pure Al is detected for the buried Al monolayers indirectly reflecting the Ti 3d - Al 3p hybridization. The differences between the electronic and crystal structures of Ti2AlC, Ti3AlC2 and TiC are discussed in relation to the number of Al layers per Ti layer in the two former systems and the corresponding change of the unusual materials properties.Comment: 14 pages, 7 figures; PACS:78.70.En, 71.15.Mb, 71.20.-

Electronic structure and chemical bonding in Ti4SiC3 investigated by soft x-ray emission spectroscopy and first principle theory

The electronic structure in the new transition metal carbide Ti4SiC3 has been investigated by bulk-sensitive soft x-ray emission spectroscopy and compared to the well-studied Ti3SiC2 and TiC systems. The measured high-resolution Ti L, C K and Si L x-ray emission spectra are discussed with ab initio calculations based on density-functional theory including core-to-valence dipole matrix elements. The detailed investigations of the Ti-C and Ti-Si chemical bonds provide increased understanding of the physical properties of these nanolaminates. A strongly modified spectral shape is detected for the buried Si monolayers due to Si 3p hybridization with the Ti 3d orbitals. As a result of relaxation of the crystal structure and the charge-transfer from Ti (and Si) to C, the strength of the Ti-C covalent bond is increased. The differences between the electronic and crystal structures of Ti4SiC3 and Ti3SiC2 are discussed in relation to the number of Si layers per Ti layer in the two systems and the corresponding change of materials properties.Comment: 12 pages, 7 figures, 1 tabl

Electronic structure investigation of Ti3AlC2, Ti3SiC2, and Ti3GeC2 by soft-X-ray emission spectroscopy

The electronic structures of epitaxially grown films of Ti3AlC2, Ti3SiC2 and Ti3GeC2 have been investigated by bulk-sensitive soft X-ray emission spectroscopy. The measured high-resolution Ti L, C K, Al L, Si L and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L-emission of Ti3AlC2. As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si-layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2, respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.Comment: 15 pages, 8 figure