Scandale, Walter
Bajko, M
Savary, F
Geometry and Alignment Requirements for the LHC Main Dipole
The 15 m long LHC superconducting dipole magnets, which contain two beam channels in a common mechanical structure, produce a magnetic field of 8.3 T required to deflect protons with 7 TeV/c momentum along a circular trajectory in the already existing LEP tunnel. The dipoles are bent in their horizontal plane to provide the largest possible mechanical aperture to the circulating beam. This paper describes the theoretical geometry of the dipole cold mass and the alignment requirements, which are imposed to satisfy the demands of LHC machine operation. A short description of the measuring and alignment procedures and of the measuring instruments is given. Results of a small series of prototype cold masses are presented and discussed.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A07.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-426;
http://cds.cern.ch/record/471343/files/lhc-project-report-426.pdf;
http://cds.cern.ch/record/471343/files/lhc-project-report-426.ps.gz;
Imported from Invenio.
Malyshev, O B
Rossi, A
Ion Desorption Vacuum Stability in the LHC: The Multigas Model
https://accelconf.web.cern.ch/e00/PAPERS/THP1B19.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-437;
http://cds.cern.ch/record/466538/files/lhc-project-report-437.pdf;
http://cds.cern.ch/record/466538/files/lhc-project-report-437.ps.gz;
Imported from Invenio.
Malyshev, O B
The Ion Impact Energy on the LHC Vacuum Chamber Walls
The proton beam circulating in the LHC vacuum chamber will ionise the residual gas. The created ions are accelerated away from the beam and reach the vacuum chamber wall with some stored energy. The value of the ion impact energy is very important for the estimation of the ion stimulated gas desorption. The ion energy is studied as function of beam parameters. It is shown that the ion energy increases for a higher beam current and a smaller b-function. The ion energy is also sensitive to the bunch length and the bunch spacing. The ion energies are estimated for a number of different elements of the LHC. The effect of the magnetic field has been also studied
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-436;
http://cds.cern.ch/record/466537/files/lhc-project-report-436.pdf;
http://cds.cern.ch/record/466537/files/lhc-project-report-436.ps.gz;
Imported from Invenio.
Baglin, V
Collins, I R
Grünhagel, C
Gröbner, Oswald
Jenninger, B
First Results from COLDEX Applicable to the LHC Cryogenic Vacuum System
A cold bore experiment (COLDEX) has been installed in the electron-positron accumulator (EPA) at CERN. The ~2 m long COLDEX cryostat, that may be cooled to below 3 K, is fitted with an actively cooled perforated beam screen to simulate the conditions in the cold arcs of the LHC. Initially, gas desorption yields were obtained using an external synchrotron radiation beam line by exposing the beam screen to grazing incident radiation with a critical energy of 194 eV. In an extended period of EPA operation and during a dedicated period for LHC studies, COLDEX was installed into the EPA ring to study more specifically the influence of the bunched positron and electron beams with the cold bore / beam screen vacuum system. The results from these experiments and some predictions applicable for the LHC will be presented.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-435;
http://cds.cern.ch/record/466536/files/lhc-project-report-435.pdf;
http://cds.cern.ch/record/466536/files/lhc-project-report-435.ps.gz;
Imported from Invenio.
Arduini, Gianluigi
Cornelis, Karel
Gröbner, Oswald
Hilleret, Noël
Höfle, Wolfgang
Jiménez, J M
Laurent, Jean Michel
Moulard, G
Pivi, M
Weiss, K P
Electron Cloud: Observations with LHC-Type Beams in the SPS
In August 1999, strong pressure increases were observed in the SPS in the presence of the new LHC-type beams. This paper reports on observations of the electron cloud phenomenon and the related pressure increase as a function of parameters such as the number of protons per bunch, the number of bunches per batch, the shape of the vacuum chamber and the electron current collected on pick-ups. Results of the observed clean-up, "beam scrubbing" will be presented as well as the consequences of the e-cloud phenomenon on the SPS operation with the LHC nominal beam intensity.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-434;
http://cds.cern.ch/record/466535/files/lhc-project-report-434.pdf;
http://cds.cern.ch/record/466535/files/lhc-project-report-434.ps.gz;
Imported from Invenio.
Baglin, V
Bojko, J
Gröbner, Oswald
Henrist, Bernard
Hilleret, Noël
Scheuerlein, C
Taborelli, M
The Secondary Electron Yield of Technical Materials and its Variation with Surface Treatments
Secondary electron emission of surfaces exposed to oscillating electromagnetic field is at the origin of the multipacting effect that could severely perturb the operation of particle accelerators. This contribution tries to illustrate by measurement results, the origin of the secondary electron emission as well as the main reasons for the discrepancies between technical materials and pure metals. The variation of the secondary electron yield with the incident electron energy will be discussed for various types of technical surfaces. The influence of a gas condensation on these surfaces will also be addressed in the context of the LHC accelerator. Various treatments aiming at a permanent reduction of the secondary electron yield will be presented. A special attention will be paid to the decrease of the secondary electron yield under electron or photon impact and to its possible beneficial consequences for the processing of devices prone to multipacting.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THXF102.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-433;
http://cds.cern.ch/record/466534/files/lhc-project-report-433.pdf;
http://cds.cern.ch/record/466534/files/lhc-project-report-433.ps.gz;
Imported from Invenio.
Pugnat, P
Schreiner, T
Siemko, A
Investigation of the Periodic Magnetic Field Modulation Inside Apertures of LHC Superconducting Dipole Models
The windings of high-field accelerator magnets are usually made of Rutherford-type superconducting cables. The magnetic field distribution along the axis of such magnets exhibits a pronounced periodic modulation with a wavelength equal to the twist pitch length of the cable used in the winding. Such an effect, resulting from quasi-persistent currents, was investigated with a Hall probe array inserted inside the aperture of 1-metre long LHC superconducting dipole models. The amplitude and the time dependence of this periodic field oscillation have been studied as a function of the transport current history. The impact on the magnet stability of the non-uniform current redistribution producing such a field modulation is discussed.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A03.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-432;
http://cds.cern.ch/record/466533/files/lhc-project-report-432.pdf;
http://cds.cern.ch/record/466533/files/lhc-project-report-432.ps.gz;
Imported from Invenio.
Bottura, L
Buzio, M
Schnizer, P
Smirnov, N
Walckiers, L
Sensitivity and Accuracy of the Systems for the Magnetic Measurements of the LHC Magnets at CERN
Beam optics of the LHC accelerator require stringent control of the field quality of the main dipole and quadrupole magnets. The field quality measurements need challenging accuracy given the small size of the aperture (50 mm) : relative strength of the magnets within 2×10-4, harmonics in the ppm range, axis determination within 0.1 mm, main field direction within 0.2 mrad. We present a detailed analysis of the accuracy and reproducibility obtained with the equipment presently available for the qualification tests of the first series magnets.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A17.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-431;
http://cds.cern.ch/record/466532/files/lhc-project-report-431.pdf;
http://cds.cern.ch/record/466532/files/lhc-project-report-431.ps.gz;
Imported from Invenio.
Modena, M
Artoos, K
Bajko, M
Bottura, L
Buzio, M
Fessia, P
Pagano, O
Perini, D
Savary, F
Scandale, Walter
Siemko, A
Spigo, G
Todesco, Ezio
Vanenkov, I
Vlogaert, J
Wyss, C
Manufacture and Performance of the LHC Main Dipole Final Prototypes
This paper reports about the program of six LHC main dipole final prototypes. This program, launched in summer 1998, relies on industrially manufactured collared coils and cold masses assembled at the CERN Magnet Assembly Facility. The magnet design for series manufacture features a "6-block" coil and austenitic steel collars, following design, stability and robustness studies. Results of mechanical and magnetic measurements are given and discussed, as well as the performances of the prototypes measured so far.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-430;
http://cds.cern.ch/record/466531/files/lhc-project-report-430.pdf;
http://cds.cern.ch/record/466531/files/lhc-project-report-430.ps.gz;
Imported from Invenio.
Wyss, C
The LHC Magnet Programme: From Accelerator Physics Requirements to Production in Industry
The LHC is designed to provide, at a beam energy of 7 TeV, a nominal peak luminosity of 1034 cm-2s-1 with simultaneous collisions at two high-luminosity insertions. This objective is being achieved by pushing the technology of superconducting accelerator magnets and cryogenics to its state-of-the-art limits, and by upgrading the existing CERN accelerators and infrastructures. In this paper, the parameters of the main dipole (1232 units) and quadrupole (392 units) magnets stemming from the LHC design considerations are presented and discussed. Subsequently, the R & D program undertaken at CERN and with industry, to experimentally validate magnet design assumptions, to assess the merits of design variants and to procure and commission the heavy tooling necessary for series manufacture, is described and its main difficulties and results highlighted. Finally a report is given about the procurement strategy, and the progress in manufacturing.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/MOZE01.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-429;
http://cds.cern.ch/record/466530/files/lhc-project-report-429.pdf;
http://cds.cern.ch/record/466530/files/lhc-project-report-429.ps.gz;
Imported from Invenio.
Billan, J
Bottura, L
Peyrot, M
Remondino, Vittorio
Rifflet, J M
Siemko, A
Simon, F
Tortschanoff, Theodor
Performance of Series-Design Prototype Main Quadrupoles for the LHC
After the successful construction of two first-generation prototypes of the main quadrupoles for the LHC, three series-design prototypes have been further manufactured at CEA-Saclay. Together with the sextupole-dipole corrector magnets and tuning quadrupoles, these twin-aperture main quadrupoles are assembled into the cold masses of the so-called short straight sections. Already during their fabrication, the collared coils and later the completed cold masses undergo warm magnetic measurements. Two of the main quadrupole cold masses have been mounted into their definitive machine cryostats and submitted to training and magnetic measurements. This paper presents the results of these cold tests by describing the quench behaviour, the transfer function in each of the apertures and the multipole components found at different levels of excitation. The field quality results, in cold conditions, will be compared to those measured at room temperature
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A15.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-428;
http://cds.cern.ch/record/466529/files/lhc-project-report-428.pdf;
http://cds.cern.ch/record/466529/files/lhc-project-report-428.ps.gz;
Imported from Invenio.
Tommasini, D
Arteche, F
Sanfilippo, S
Siemko, A
Vanenkov, I
Wyss, C
Status of the LHC Short Dipole Model Programme
The 1-m model program for the main LHC dipoles is now mainly focussed on double-aperture magnets. In the past years an intensive program based on single-aperture dipoles allowed to select the series-design features among several variants for the coil cross section, the material of the collars and of the coil end spacers, the coil pre-stress and the cable insulation. The recent double-aperture models are dedicated to the fine-tuning of the baseline design and the manufacture of the coil ends. This paper reports about the fabrication and testing of these magnets and the results relevant for the series production of the 15-m long full-size dipole cold masses.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A14.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-427;
http://cds.cern.ch/record/466528/files/lhc-project-report-427.pdf;
http://cds.cern.ch/record/466528/files/lhc-project-report-427.ps.gz;
Imported from Invenio.
Peyrot, M
Redaelli, S
Remondino, Vittorio
Rifflet, J M
Scandale, Walter
Simon, F
Todesco, Ezio
Tortschanoff, Theodor
Analysis of Warm Magnetic Measurements of the First Series-Design Prototypes of the LHC Main Quadrupoles
The room temperature magnetic measurements of the first series-design prototypes of the LHC main quadrupoles are analysed. Data relative to the collared coils and to the assembled cold mass are considered. The averages of the multipoles along the magnet axis are interpreted as the systematic components. The agreement with the nominal design is verified, and possible explanations for discrepancies with regard to the multipole allowed by symmetry are worked out. The standard deviations of the multipoles along the axis are interpreted as the random components. We show that the latter can be interpreted in terms of random movements of up to 25-35 µm of the coil blocks, because of components and assembly tolerances. A good correlation between measurements made on collared coil and the assembled cold mass is found. The influence on field quality of a systematic radial misalignment of the coil conductor is also evaluated.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A12.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-425;
http://cds.cern.ch/record/466527/files/lhc-project-report-425.pdf;
http://cds.cern.ch/record/466527/files/lhc-project-report-425.ps.gz;
Imported from Invenio.
Ferracin, P
Scandale, Walter
Todesco, Ezio
Tropea, P
Vanenkov, I
Modelization of the Thermo-Mechanical Structure of the LHC Main Dipole and Influence on Field Quality
The mechanical structure of the main LHC dipole is analysed. A finite element model is used to estimate the loads and the deformations at cryogenic temperature. The correct setting of the model parameters is crucial to obtain a reliable model to forecast the influence of design and tolerances on field quality. We discuss how the prestress loss from room to cryogenic temperature experimentally observed in the prototypes can be predicted using the finite element model. An estimate of the influence on field quality of deformations and tolerances due to manufacturing is given.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THOAF101.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-424;
http://cds.cern.ch/record/466526/files/lhc-project-report-424.pdf;
http://cds.cern.ch/record/466526/files/lhc-project-report-424.ps.gz;
Imported from Invenio.
Lucas, J
Bottura, L
Dariol, H
Ostojic, R
Sanfilippo, S
Siemko, A
Sonnemann, F
Tommasini, D
Vanenkov, I
Performance of the 1-m Model of the 6 kA Superconducting Quadrupole for the LHC Insertions
The LHC dispersion suppressors and matching sections will be equipped with individually powered superconducting quadrupoles with an aperture of 56 mm. In order to minimise the cost of the powering circuits, the quadrupole has been designed on the basis of an 8 mm wide NbTi Rutherford-type cable for a nominal current of 5300 A, corresponding to a gradient of 200 T/m at 1.9 K. In order to validate the design options a model magnet program has been launched. In this report we describe the construction features of the first 1-m long magnet, and present its training performance and the results of protection studies.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP1B18.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-423;
http://cds.cern.ch/record/466525/files/lhc-project-report-423.pdf;
http://cds.cern.ch/record/466525/files/lhc-project-report-423.ps.gz;
Imported from Invenio.
Siegel, N
Overview of the LHC Magnets other than the Main Dipoles
The Large Hadron Collider, due for commissioning in 2005, features a large and complex magnet system that includes about 3000 double aperture magnets and 5000 single aperture ones. Most of these magnets are super-conducting, using conductors made of NbTi alloy, with a coil bore of 56 mm and operating in a static bath of su-perfluid helium at 1.9 K, fully exploiting the conductor limit at these low temperatures. Only a few particular magnets will operate at 4.5 K. For special applications in the long straight sections and for beam injection and ex-traction, highly specialised room temperature magnets are used. The paper discusses the underlying concepts, which lead to the design and layout of the interaction region magnets, required to obtain the very demanding beam parameters at the four main LHC experiments. The focus will then be on the magnetic elements of matching re-gions, dispersion suppressors and main arcs, with a dis-cussion of the functionality of the different magnet fami-lies. The report will be concluded with a summary giving the present status of the design, procurement and testing of these magnets.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-422;
http://cds.cern.ch/record/466524/files/lhc-project-report-422.pdf;
http://cds.cern.ch/record/466524/files/lhc-project-report-422.ps.gz;
Imported from Invenio.
Dahlerup-Petersen, K
Kazmine, B
Popov, V
Sytchev, V V
Vasilev, L B
Zubko, V G
Energy Extraction Resistors for the Main Dipole and Quadrupole Circuits of the LHC
When the LHC will be operating at its maximum beam energy, its superconducting dipole chains store a total magnetic energy of more than 11 GJ. At the same time, the QF and QD quadrupole circuits store a total energy of 400 MJ. Even with the sectorisation of each of the three principal power circuits into eight individually powered segments, the stored energy of a single circuit is considerable. During normal operation the energy in the dipole circuits is safely returned to the mains grid, using the thyristor-based, 'booster' unit of the power converters, operating in inversion. For the quadrupole chains, where the converter is of a mono-polar topology, the stored energy is dissipated into the resistive part of the warm d.c. power lines (busbars and cables) in a slow, controlled run-down. When a magnet quenches, however, such a slow energy transfer, taking 20 minutes from the rated LHC current, will not be possible. The 'cold' diode, taking over the magnet current in case of a quench, will not survive this slow current decay. For this reason, energy extraction facilities will be inserted into the power circuits. These systems are being designed to absorb the total circuit energy and de-excite the chains with a current decay time constant of 104 s for the dipoles and 40 s for the quadrupoles. The resulting maximum decay rates (-125 A/s and -325 A/s respectively) are comfortably below the levels where quench-back will occur. The energy extraction systems are based on an array of special, mechanical d.c. circuit breakers and absorber resistors, which are switched into the circuit by opening of the breakers. The design and construction of these large power resistors of a unique concept are the topics of this paper. The project is being realised as collaboration between, IHEP-Protvino, CERN and European Industry.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-421;
http://cds.cern.ch/record/466523/files/lhc-project-report-421.pdf;
http://cds.cern.ch/record/466523/files/lhc-project-report-421.ps.gz;
Imported from Invenio.
Ballarino, A
Application of High Temperature Superconductors to Accelerators
Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high temperature superconductivity. The LHC, currently under construction at CERN, will transfer more than 3 million ampères of current through leads having high temperature superconducting sections, thus providing a unique opportunity to incorporate these materials into large scale systems. The status of this project and the cost-benefit consequence of its application will be reported.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/TUXF203.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-420;
http://cds.cern.ch/record/466522/files/lhc-project-report-420.pdf;
http://cds.cern.ch/record/466522/files/lhc-project-report-420.ps.gz;
Imported from Invenio.
Schmidt, R
Giloux, C
Hilaire, A
Ijspeert, Albert
Rodríguez-Mateos, F
Sonnemann, F
Protection of the Superconducting Corrector Magnets for the LHC
n the LHC about 6500 superconducting corrector magnets will be powered either in stand-alone mode or in electrical circuits of up to 154 magnets. Single corrector magnets are designed to be self-protected in case of a quench. The protection scheme of magnets powered in series depends on the energy stored in the magnet and on the number of magnets in the circuit. A quench is detected by measuring the resistive voltage of the circuit. The power converter is switched off, and for most circuits part of the energy is extracted with a resistor. Some magnets may require a resistor or possibly a diode parallel to the magnet in order to avoid overheating of the superconducting wire or an unacceptable voltage level. Experiments have been performed to understand quenching of prototype corrector magnets. In order to determine the adequate protection schemes for the magnet circuits the results have been used as input for simulations to extrapolate to the LHC conditions.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A08.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-419;
http://cds.cern.ch/record/466521/files/lhc-project-report-419.pdf;
http://cds.cern.ch/record/466521/files/lhc-project-report-419.ps.gz;
Imported from Invenio.
Rodríguez-Mateos, F
Pugnat, P
Sanfilippo, S
Schmidt, R
Siemko, A
Sonnemann, F
Quench Heater Experiments on the LHC Main Superconducting Magnets
In case of a quench in one of the main dipoles and quadrupoles of CERN's Large Hadron Collider (LHC), the magnet has to be protected against excessive temperatures and high voltages. In order to uniformly distribute the stored magnetic energy in the coils, heater strips installed in the magnet are fired after quench detection. Tests of different quench heater configurations were performed on various 1 m long model and 15 m long prototype dipole magnets, as well as on a 3 m long prototype quadrupole magnet. The experiments aimed at optimising the layout of the quench heater strips, minimising the complexity of the protection system and determining its redundancy. In this paper we discuss the results of the performed experiments and describe the optimised quench heater design for the LHC main magnets.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A04.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-418;
http://cds.cern.ch/record/466520/files/lhc-project-report-418.pdf;
http://cds.cern.ch/record/466520/files/lhc-project-report-418.ps.gz;
Imported from Invenio.
Bergot, J B
Dambre, P
Nielsen, L
Parma, Vittorio
Peyrot, M
Renaglia, T
Rifflet, J M
Rohmig, P
Roy, E
Simon, F
Tortschanoff, Theodor
Vincent, D
A Modular Design for the 56 Variants of the Short Straight Section in the Arcs of the Large Hadron Collider (LHC)
The 360 Short Straight Sections (SSS) necessary for the eight arcs of the LHC machine have to fulfil different requirements. Their main function is to house the lattice two-in-one superconducting quadrupole and various correction magnets, all operating at 1.9 K in a superfluid helium bath. The magnetic and powering schemes of the arcs and the fact that the two proton beams alternate between the inner and outer magnet channels impose 24 different combinations of magnet assemblies, all housed in an identical helium enclosure. The cryogenic architecture of the LHC machine is based on cryogenic loops spanning over one half-cell (53 m) for the 4.6-20 K circuit, over a full cell (107 m) for the 1.9 K circuits, up to the full arc (about 2.3 km) for the shield cooling line. This cryogenic layout, when superimposed to the magnetic scheme, further complicated by the cryostat insulation vacuum sectorisation every 2 cells, creates additional assembly variants, up to a total number of 56. The required flexibility in the manufacture and assembly, as well as economic considerations, have led to a modular design for the different SSS components and sub-assemblies. This modularity allows to "specialise" the SSS at the latest possible assembly step of the "just in time" production line. This paper presents the conceptual design considerations to achieve this modularity, the SSS design retained for the series manufacture, and the assembly procedures recently validated on a prototype program at CERN.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-417;
http://cds.cern.ch/record/466519/files/lhc-project-report-417.pdf;
http://cds.cern.ch/record/466519/files/lhc-project-report-417.ps.gz;
Imported from Invenio.
Hauviller, Claude
Ivanov, P M
Poncet, Alain
Sacré, P
Trilhe, P
The Electrical Distribution Feed Box for the LHC Prototype Cell
The Electrical Distribution Feed Box (DFB) for the Large Hadron Collider (LHC) Prototype Cell (String 2) is a 6 meter-long 4.6 K / 0.135 MPa liquid helium cryostat which supports and cools 13 kA and 600 A High-Temperature Superconductor (HTS) current leads. These are used for powering the String 2 main dipole and quadrupole superconducting magnets, together with their correctors. The DFB also incorporates the l-plate between its saturated liquid helium bath and the magnet pressurized superfluid helium bath at 1.9 K/ 0.13 MPa. The DFB is built within the frame of a collaboration between CERN and the Budker Institute of Nuclear Physics (Novosibirsk, Russian Federation). It is a complex cryostat satisfying a number of constraints (space available, accessibility, integration) and combining different technologies such as mechanical and electrical engineering, superconductivity, cryogenics and vacuum. The current status of the design and construction of the DFB for the LHC Prototype Cell, together with an outlook towards the LHC arc DFB's, is given.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP2A06.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-416;
http://cds.cern.ch/record/466518/files/lhc-project-report-416.pdf;
http://cds.cern.ch/record/466518/files/lhc-project-report-416.ps.gz;
Imported from Invenio.
Buenaventura, A
Hauviller, Claude
Skoczen, Blazej
Mechanical Behaviour of the LHC Cryodipoles
The LHC cryodipoles are slender and heavy objects more than 15-m long. The major components of the cryodipole assembly are the 28-tonne cold mass, supported on its three Glass-Fibre-Reinforced-Epoxy support posts and the 4-tonne vacuum vessel. The performance of the LHC depends very much upon the accurate positioning of the dipoles and the beam tubes, in particular to maximise the useful beam apertures. The cryodipoles will be conditioned and measured in surface assembly buildings, then handled and transported to their positions in the tunnel and, finally, aligned. This paper presents the static and dynamic studies of the cryodipole in different configurations. The tests and analyses carried out have led to a thorough understanding of the mechanical behaviour of the cryodipoles. From the static analysis, an hyperstatic supporting system is proposed in order to minimise the systematic deflections and the effects due to changing temperature conditions in the tunnel. The dynamic analysis has shown that the cryodipole resonates at a series of very low natural frequencies and, moreover, shows a low damping value. Since the dynamic loads during transport and handling are in the low frequency range, the cryodipole components are potentially susceptible to damage. Simulations have included the truck suspension for road transport and the lifting device for handling with a crane. Solutions coping with the transport and handling conditions are presented.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-415;
http://cds.cern.ch/record/466517/files/lhc-project-report-415.pdf;
http://cds.cern.ch/record/466517/files/lhc-project-report-415.ps.gz;
Imported from Invenio.
Chemli, S
Hauviller, Claude
Messerli, R
Muttoni, Y
Prin, H
Van Uytvinck, E
A Virtual CAD Model of the LHC
Integrating the large and complex LHC machine into the existing LEP tunnel is a major challenge. Space was not really a problem to fit the LEP machine into its tunnel, but LHC cryostats are much larger than the LEP quadrupoles and the external cryogenic line fills even more the tunnel. Space problems lead to small clearances. Possible conflicts, or at least the most penalising ones, between installed equipment or with transport, must be solved beforehand in order to avoid unacceptable delays and extra costs during the installation. Experience gained with LEP has already shown the help that Computer-Aided Engineering tools could provide for the integration. A virtual model of the LHC is presently prepared. The actual LEP tunnel, known with a quite good accuracy (centimetre level), has been modelled and all the elements of the machine constructed as 3D objects with the CAD system are positioned accurately on the basis of data generated from the theoretical definition. These layouts are used to generate the reference sections and to check the clearances. Examples of this powerful approach applied to engineering for accelerators are given.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-414;
http://cds.cern.ch/record/466516/files/lhc-project-report-414.pdf;
http://cds.cern.ch/record/466516/files/lhc-project-report-414.ps.gz;
Imported from Invenio.
Kowalczyk, P
Poncet, Alain
Skoczen, Blazej
Layout and Design of the Auxiliary Bus-Bar Line for the LHC Arc Main Cryostat
The superconducting multipole magnets housed in the cold mass of the LHC arc short straight sections, together with the arc dispersion suppressor and matching section quadrupole magnets, will be electrically fed along the 3 km arcs via 600 A and 6 kA superconducting flexible cables. These will be routed into a tube running parallel to the cold masses, placed inside their cryostat [1], from power converters located at each of the 16 arc extremities. The superconducting 53.5 m cable segments will be inserted in the pipeline at machine installation time in the tunnel, thus limiting the number of useless electrical interconnections to the minimum necessary. Cryogenically connected to the 1.9 K superfluid helium vessel of the cold masses at each main quadrupole location, this so-called auxiliary bus-bar tube (EAB) will be thermally and mechanically separated from the magnet main stream. The general layout of the pipeline, its thermo mechanical functional specification and the tight cryogenic, mechanical, electrical, interface and geometrical constraints imposed by the LHC arc cryostat are presented, together with its detailed design.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-413;
http://cds.cern.ch/record/466515/files/lhc-project-report-413.pdf;
http://cds.cern.ch/record/466515/files/lhc-project-report-413.ps.gz;
Imported from Invenio.
Tavian, L
Large Cryogenics Systems at 1.8 K
Cryogenics is now widely present in large accelerator projects using applied superconductivity. Economical considerations permanently require an increase of the performance of superconducting devices. One way to do this consists to lower their operating temperature and to cool them with superfluid helium. For this purpose, large cryogenic systems at 1.8 K producing refrigeration capacity in the kW range have to be developed and implemented. These cryogenic systems require large pumping capacity at very low pressure based on integral cold compression or mixed cold-warm compression. This paper describes and compares the different cooling methods with saturated or pressurised superfluid helium, gives the present status of the available process machinery with their practical performance, and reviews the different thermodynamical cycles for producing refrigeration below 2 K, with emphasis on their operational compliance.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-412;
http://cds.cern.ch/record/466514/files/lhc-project-report-412.pdf;
http://cds.cern.ch/record/466514/files/lhc-project-report-412.ps.gz;
Imported from Invenio.
Kotov, V.I.
Afonin, A.G.
Biryukov, V.M.
Chesnokov, Yu.A.
Galyaev, N.A.
Gres, V.N.
Maisheev, V.A.
Medvedev, V.A.
Minchenko, A.V.
Terekhov, V.I.
Troyanov, E.F.
Fedotov, Yu.S.
Zapolsky, V.N.
Zelenov, B.A.
Ivanov, Yu.M.
Scandale, W.
Application of Bent Crystals at IHEP 70-GeV Accelerator to Enhance the Efficiency of its Usage
364-366
Bent crystal was extracting 70-GeV protons with average intensity 4x10$^{11}$ (as measured in external beamline) per spill of ~1.6 s duration, in parallel to the simultaneous work of two internal targets in the accelerator ring. An additional crystal, placed in the external beamline, was deflecting a small part of the extracted beam with intensity ~10$^7$ protons toward another physics experiment. Crystal-extracted beam had a typical size of 4 mm by 4 mm fwhm at the end of the external beamline. Measurements for the extraction efficiency and other characteristics at the simultaneous work of four experimental set-ups are presented. With crystal working in the above-said regime during one month, no degradation of channeling was observed. The studies of extraction efficiency have been continued with new crystals.
eng
2000
http://weblib.cern.ch/abstract?CERN-LHC-2000-007;
http://accelconf.web.cern.ch/e00/PAPERS/MOP3A11.pdf;
http://cds.cern.ch/record/483650/files/arXiv:hep-ex_0111001.pdf;
http://cds.cern.ch/record/483650/files/lhc-2000-007.pdf;
http://cds.cern.ch/record/483650/files/lhc-2000-007.ps.gz;
Imported from Invenio.
Boscolo, I
Celona, L
Cialdi, S
Ciavola, G
Cipriani, D
Gammino, S
Handerek, J
Marletta, S
Riege, H
Somarè, G
Valentini, M
Application of Ferroelectric Cathodes to Enhance the Ion Yield in the Caesar Source at LNS
With increasing RF power the electron concentration in the plasma of ECR ion sources is decreasing in comparison to the ion concentration, so that the plasma is charging up positively. Direct injection of electrons into the ECR plasma can increase the electron charge density and the ion current yield. We have used ferroelectric cathodes to inject electrons into the Argon plasma of the CAESAR ion source at INFN-LNS (Catania, Italy). The cathode was placed at about 10 cm from the hot plasma and a bipolar high voltage pulse of 1.6 kV was used to trigger the electron emission. No additional acceleration has been provided. The use of the ferroelectric cathode leads to an increase of about 30% of the Ar8+ intensity, which has been monitored during the test. In addition, magneto-hydrodynamic instabilities in the ECR source were damped during and after electron injection.
eng
2000
https://accelconf.web.cern.ch/e00/PAPERS/THP7B03.pdf;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2000-003;
http://cds.cern.ch/record/453866/files/lhc-2000-003.pdf;
http://cds.cern.ch/record/453866/files/lhc-2000-003.ps.gz;
Imported from Invenio.
Billy, J C
Bojon, J P
Gröbner, Oswald
Hilleret, Noël
Jiménez, M
Laugier, I
Strubin, Pierre M
The LEP Vacuum System: A Summary of 10 Years of Successful Operation
he LEP accelerator is now operating regularly above 100 GeV and its vacuum system is submitted to the impact of energetic photons with a critical energy approaching 1 MeV. The consequences of this high energy on the photon induced desorption will be reviewed in the light of the various photon absorption mechanisms for aluminium. A review will also be given of the ten years of operation of the LEP vacuum system concerning more especially the evolution of the dynamic pressure with the beam dose and energy, the main difficulties experienced and the actions taken to overcome them.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2000-002;
http://cds.cern.ch/record/453865/files/lhc-2000-002.pdf;
http://cds.cern.ch/record/453865/files/lhc-2000-002.ps.gz;
Imported from Invenio.
Kuhn, H K
Gayet, P
Juillerat, A C
Rabany, Michel
Wollès, J C
Experience with the Multi-Year Implementation of an Industrial Control System
In 1990, CERN passed a multi-year purchasing and installation contract for the LEP 200 Cryogenics control system with ABB, one of the world's leading suppliers of integrated Distributed Control Systems (DCS). A financial framework provided over a period of eight years the required supplies. These were called up with so called "Release Orders", taking into account the latest technical developments. The issues and experiences with such a new approach and the resulting control system are described.
eng
2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2000-001;
http://cds.cern.ch/record/453864/files/lhc-2000-001.pdf;
http://cds.cern.ch/record/453864/files/lhc-2000-001.ps.gz;
Imported from Invenio.