Parma, V
Rossi, L
Performance of the LHC magnet system
The LHC magnet system, essentially composed of superconducting magnets operating at 1.9 K, has been largely commissioned in 2007-08. Before the serious incident of 19th September 2008, the magnet system was commissioned up to 7 kA (4 TeV proton beam energy); six (out of eight) sectors were commissioned up to 5.5 TeV and one up to 6.6 TeV. For more than one week, both beams have been injected, circulated and captured in the RF bucket, thus assessing the optics at injection energy. The incident in sector 3-4, originated by a serious defect of a high-current joint between magnets with large collateral damage, has changed the plans: 53 magnets in the damaged zone have been substituted or repaired meanwhile a campaign of consolidation is under way to allow safe restart of the accelerator in fall 2009. All these points and other issues presented and discussed, with emphasis on the incident in sector 3-4.
eng
2010
http://cds.cern.ch/record/1204578/files/tu1rai03.pdf;
Imported from Invenio.
Laface, E
Scandale, Walter
Cavoto, G
Peggs, S
Simulation results for crystal collimation experiment in SPS UA9
The UA9 experiment will first take place in 2009 at the CERN-SPS and will evaluate the feasibility of silicon crystals as primary collimators for a storage ring. A crystal placed at 6 σ from the beam core will deviate protons towards two Roman Pots and a tungsten absorber (TAL). In this paper the authors show simulations of the expected beam dynamics and of the capture efficiency into the secondary collimator. The result of these simulations will guide us in interpreting the experimental data expected in UA9.
eng
2010
http://cds.cern.ch/record/1204555/files/we6rfp019.pdf;
Imported from Invenio.
Uythoven, J
Axensalva, J
Baggiolini, V
Carlier, E
Gallet, E
Goddard, B
Kain, V
Lamont, M
Experience with the LHC beam dump post-operational checks system
After each beam dump in the LHC automatic post-operational checks are made to guarantee that the last beam dump has been executed correctly and that the system can be declared to be ‘as good as new’ before the next injection is allowed. The analysis scope comprises the kicker waveforms, redundancy in kicker generator signal paths and different beam instrumentation measurements. This paper describes the implementation and the operational experience of the internal and external post-operational checks of the LHC beam dumping system during the commissioning of the LHC without beam and during the first days of beam operation.
eng
2010
http://cds.cern.ch/record/1199975/files/tu6rfp029.pdf;
Imported from Invenio.
Veness, R
The ATLAS beam vacuum system
The Large Hadron Collider (LHC) has recently started-up at CERN. It will provide colliding beams to four experiments installed in large underground caverns. A specially designed and constructed sector of the LHC beam vacuum system transports the beams though each of these collision regions, forming a primary interface between machine and experiment. ATLAS [1] is the largest of the four LHC colliding beam experiments, being some 40 m long and 22 m in diameter. Physics performance, geometry and access imposed a large number of constraints on the design of the beam vacuum system. This paper describes the geometry and layout of the ATLAS beam vacuum system. Specific technologies developed for ATLAS, and for the alignment and installation of the vacuum chambers are described as well as the issues related to the physical interfaces with the experiment.
eng
2010
http://cds.cern.ch/record/1199768/files/mo6rfp009.pdf;
Imported from Invenio.
Mahner, E
Chemli, S
Cruikshank, P
Forkel-Wirth, D
Jiménez, J M
Radiation zoning for vacuum equipment of the CERN Large Hadron Collider
Beam losses in high-energy particle accelerators are responsible for beam lifetime degradation. In the LHC beam losses will create a shower of particles while interacting with materials from the beam pipes and surroundings, resulting in a partial activation of material in the tunnel. Efforts have been made during the accelerator design to monitor and to reduce the activation induced by beam losses. Traceability for all vacuum components has been established providing a tool to follow-up individually each component or subcomponents installed in the tunnel, regardless of their future destination e.g. recycling or disposal. In the latter case, the history of vacuum components will allow calculating the beam-induced activation and permit comparisons with in-situ and ex-situ measurements. This zoning will also help to reduce collective and individual radiation doses to personnel during interventions. The paper presents the vacuum system layout and describes the LHC vacuum zoning and its implementation using an ORACLE© database.
eng
2010
http://cds.cern.ch/record/1199767/files/we6rfp048.pdf;
Imported from Invenio.
Barnes, M J
Caspers, Friedhelm
Kroyer, T
Métral, E
Roncarolo, F
Salvant, B
Measurement of the longitudinal and transverse impedance of kicker magnets using the coaxial wire method
Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, even above the Curie temperature of ferrite. In addition the impedance can contribute to beam instabilities. In this paper different variants of the coaxial wire method, both for measuring longitudinal and transverse impedance, are briefly discussed in a tutorial manner and do's and don'ts are shown on practical examples. In addition we present the results of several impedance measurements for SPS kickers using the wire method and compare those results with theoretical models.
eng
2010
http://cds.cern.ch/record/1199760/files/tu6rfp076.pdf;
Imported from Invenio.
Barnes, M J
Caspers, Friedhelm
Cornelis, K
Ducimetière, L
Mahner, E
Papotti, G
Rumolo, G
Senaj, V
Shaposhnikova, E
Measurement and analysis of SPS kicker magnet heating and outgassing with Different Bunch Spacing
Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, over several hours, even above the Curie temperature of the ferrite. At present the nominal bunch spacing in the SPS is 25 ns, however for an early stage of LHC operation it is preferable to have 50 ns bunch spacing. Machine Development (MD) studies have been carried out with an inter-bunch spacing of 25 ns, 50 ns or 75 ns. For some of the SPS kicker magnets the 75 ns bunch spacing resulted in considerable beam induced heating. In addition the MDs showed that 50 ns bunch spacing could result in a very rapid pressure rise in the kicker magnet and thus cause an interlock. This paper discusses the MD observations of the SPS kickers and analyses the available data to provide explanations for the phenomena: possible remedies are also discussed.
eng
2010
http://cds.cern.ch/record/1199759/files/fr2rac02.pdf;
Imported from Invenio.
Gianfelice-Wendt, E
Goddard, B
Höfle, Wolfgang
Kain, V
Meddahi, M
Shaposhnikova, E
Koschik, A
LHC Abort Gap Cleaning with the Transverse Damper
In the Large Hadron Collider, LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD X for various LHC optics configurations, including the estimated multipolar errors.
eng
2010
http://cds.cern.ch/record/1199758/files/CERN-ATS-2009-016.pdf;
http://cds.cern.ch/record/1199758/files/we6pfp017.pdf;
Imported from Invenio.
Goddard, B
Agapov, I
Carlier, E
Ducimetière, L
Gallet, E
Gyr, M
Jensen, L
Jones, R
Kain, V
Kramer, T
Lamont, M
Meddahi, M
Mertens, V
Risselada, Thys
Uythoven, J
Wenninger, J
Weterings, W
Initial results from beam commissioning of the LHC beam dump system
Initial commissioning of the LHC beam dump system with beam took place in August and September 2008. The preparation, setting-up and the tests performed are described together with results of the extractions of beam into the dump lines. Analysis of the first detailed aperture measurements of the extraction channels and kicker performance derived from dilution sweep shapes are presented. The performance of the other equipment subsystems is summarised, in particular that of the dedicated dump system beam instrumentation.
eng
2010
http://cds.cern.ch/record/1199756/files/tu6rfp024.pdf;
Imported from Invenio.
Kramer, T
Goddard, B
Uythoven, J
LHC beam dump system: Consequences of abnormal operation
The LHC beam dump system is one of the most critical systems concerning machine protection and safe operation. It is used to dispose of high intensity beams between 450 GeV and 7 TeV. Studies into the consequences of abnormal beam dump actions have been performed. Different error scenarios have been evaluated using particle tracking in MAD-X, including an asynchronous dump action, and the impact of different orbit and collimator settings. Losses at locations in the ring and the beam dump transfer lines have been quantified as a function of different settings of the dump system protection elements. The implications for the setting up and operation of these protection elements are discussed.
eng
2010
http://cds.cern.ch/record/1199755/files/tu6rfp031.pdf;
Imported from Invenio.
Meddahi, M
Agapov, I
Fuchsberger, K
Goddard, B
Herr, Werner
Kain, V
Mertens, V
Missiaen, D
Risselada, Thys
Uythoven, J
Wenninger, J
Gianfelice, E
Machine studies during beam commissioning of the SPS-to-LHC transfer lines
Through May to September 2008, further beam commissioning of the SPS-to-LHC transfer lines was performed. For the first time, optics and dispersion measurements were also taken in the last part of the lines, and into the LHC. Extensive trajectory and optics studies were conducted, in parallel with hardware checks. In particular dispersion measurements and their comparison with the beam line model were analysed in detail and led to propose the addition of a dispersion-free steering algorithm in the existing trajectory correction program. Its effectiveness was simulated and is briefly discussed.
eng
2010
http://cds.cern.ch/record/1199754/files/th6pfp040.pdf;
Imported from Invenio.
Mertens, V
Agapov, I
Goddard, B
Gyr, M
Kain, V
Kramer, T
Lamont, M
Meddahi, M
Uythoven, J
Wenninger, J
Beam commissioning of injection into the LHC
The LHC injection tests and first turn beam commissioning took place in late summer 2008, after detailed and thorough preparation. The beam commissioning of the downstream sections of the SPS-to-LHC transfer lines and the LHC injection systems is described. The details of the aperture measurements in the injection regions are presented together with the performance of the injection related equipment. The measured injection stability is compared to the expectations. The operational issues encountered are discussed.
eng
2010
http://cds.cern.ch/record/1199752/files/tu6rfp026.pdf;
Imported from Invenio.
Montabonnet, V
Pittet, S
Thurel, Y
Cussac, P
Earth current monitoring circuit for inductive loads
The search for higher magnetic fields in particle accelerators increasingly demands the use of superconducting magnets. This magnet technology has a large amount of magnetic energy storage during operation at relatively high currents. As such, many monitoring and protection systems are required to safely operate the magnet, including the monitoring of any leakage of current to earth in the superconducting magnet that indicates a failure of the insulation to earth. At low amplitude, the earth leakage current affects the magnetic field precision. At a higher level, the earth leakage current can additionally generate local losses which may definitively damage the magnet or its instrumentation. This paper presents an active earth fault current monitoring circuit, widely deployed in the converters for the CERN Large Hadron Collider (LHC) superconducting magnets. The circuit allows the detection of earth faults before energising the circuit as well as limiting any eventual earth fault current. The electrical stress on each circuit component is analyzed and advice is given for a totally safe component selection in relation to a given load.
eng
2010
http://cds.cern.ch/record/1199751/files/mo6pfp051.pdf;
Imported from Invenio.
Bottura, L
Buzio, M
Catalan-Lasheras, N
Deniau, L
Di Castro, M
Fartoukh, S
Giovannozzi, M
Hagen, P
Koutchouk, Jean-Pierre
Lamont, M
Miles, J
Remondino, V
Sammut, N
Sanfilippo, S
Schmidt, F
Sernelius, D
Steinhagen, R
Strzelczyk, M
Tomás, R
Todesco, E
Venturini-Delsolaro, W
Walckiers, L
Wenninger, J
Wolf, R
Xydi, P
First field test of FiDeL: The magnetic field description for the LHC
The start-up of the LHC has provided the first field test for the concept, functionality and accuracy of FiDeL, the Field Description for the LHC. FiDeL provides a parametric model of the transfer function of the main field integrals generated by the series of magnets in the LHC powering circuits, comprising superconducting and normal-conducting main optical elements and high-order harmonic correctors. The same framework is used to predict harmonic errors of both static and dynamic nature, and forecast appropriate corrections. In this paper we make use of beam-based measurements taken on the first LHC beams to assess the first-shot accuracy in the prediction of the current setting for the main arc magnets.
eng
2010
http://cds.cern.ch/record/1199588/files/CERN-ATS-2009-010.pdf;
http://cds.cern.ch/record/1199588/files/mo6pfp046.pdf;
Imported from Invenio.
Bailey, R
Bellesia, B
Catalan Lasheras, N
Dahlerup-Petersen, K
Denz, R
Robles, C
Koratzinos, M
Pojer, M
Ponce, L
Saban, R
Schmidt, R
Siemko, A
Solfaroli Camillocci, M
Thiesen, H
Vergara Fernandez, A
Flora, R H
Charifoulline, Z
Bednarek, M
Górnicki, E
Jurkiewicz, P
Kapusta, P
Strait, J
Methods to detect faulty splices in the superconducting magnet system of the LHC
The incident of 19 September 2008 at the LHC was caused by a faulty inter-magnet splice of about 200 nΩ resistance. Cryogenic and electrical techniques have been developed to detect other abnormal splices, either between or inside the magnets. The existing quench protection system can be used to detect internal splices with R>20 nΩ. Since this system does not cover the bus between magnets, the cryogenic system is used to measure the rate of temperature rise due to ohmic heating. Accuracy of a few mK/h, corresponding to a few Watts, has been achieved, allowing detection of excess resistance, if it is more than 40 nΩ in a cryogenic subsector (two optical cells). Follow-up electrical measurements are made in regions identified by the cryogenic system. These techniques have detected two abnormal internal magnet splices of 100 nΩ and 50 nΩ respectively. In 2009, this ad hoc system will be replaced with a permanent one to monitor all splices at the nΩ level.
eng
2010
http://cds.cern.ch/record/1199587/files/CERN-ATS-2009-009.pdf;
http://cds.cern.ch/record/1199587/files/mo6pfp049.pdf;
Imported from Invenio.
Denz, R
Dahlerup-Petersen, K
Formenti, F
Meß, K H
Siemko, A
Steckert, J
Walckiers, L
Strait, J
Upgrade of the protection system for superconducting circuits in the LHC
Prior to the re-start of the Large Hadron Collider LHC in 2009 the protection system for superconducting magnets and bus-bars QPS will be substantially upgraded. The foreseen modifications will enhance the capability of the system in detecting problems related to the electrical interconnections between superconducting magnets as well as the detection of so-called aperture symmetric quenches in the LHC main magnets.
eng
2010
http://cds.cern.ch/record/1199586/files/mo6pfp047.pdf;
Imported from Invenio.
Verweij, A
Sammut, N
Venturini Delsolaro, W
Wolf, R
Pre-cycle selection for the superconducting main magnets of the Large Hadron Collider
Pre-cycles for setting up the main magnets of the Large Hadron Collider are necessary for ensuring field reproducibility and low field-decay rates at injection. In this paper we propose standard pre-cycles for the main magnets of the LHC. We study the influence of the pre-cycle parameters on the field decay at injection by two different models. One already proven model is semi-empirical based on magnetic measurements of the magnets. The other is a new network based model of a Rutherford cable which directly calculates the current redistribution and associated magnetization change in the cable strands. The pre-cycle to be used may depend on the history of the machine or may have to be changed because of unforeseen phenomena in the machine. The choice of a new pre-cycle on the basis of magnetic measurements alone is a lengthy process. We confirm the usefulness of the network based model as a tool for selecting new pre-cycles, including decay-blocking degaussing pre-cycles, and compare with magnetic measurements.
eng
2010
http://cds.cern.ch/record/1199585/files/mo6pfp054.pdf;
Imported from Invenio.
Tavian, L
Helium II calorimetry for the detection of abnormal resistive zones in LHC sectors
Following the incident on a LHC sector due to an electrical arc on the main dipole bus-bar circuit, postmortem analysis of previous current plateaus has shown abnormal temperature drift in the helium II baths of some magnets in the concerned area. In order to identify other possible risky areas, a detection system based on calorimety using available precision cryogenic thermometers has been first validated by applying calibrated heating in the magnet cold-mass and then implemented in the different sectors. On the 3-km long continuous helium II cryostat of each LHC sector, this method allows detecting abnormal dissipation in the W-range, i.e. additional resistive heating due to abnormal resistance of about 40 nΩ at 7 kA and less than 15 nΩ at the nominal current of 12 kA. The paper describes the principle and the methodology of this calorimetric method and gives the results obtained on the LHC sectors.
eng
2010
http://cds.cern.ch/record/1199584/files/we6rfp003.pdf;
Imported from Invenio.
Veness, R
Ramos, D
Lepeule, P
Rossi, A
Schneider, G
Blanchard, S
Installation and commissioning of vacuum systems for the LHC particle detectors
The LHC collider has recently completed commissioning at CERN. At four points around the 27 km ring, the beams are put into collision in the centre of the experiments ALICE, ATLAS, CMS and LHCb which are installed in large underground caverns. The ‘experimental vacuum systems’ which transport the beams through these caverns and collision points are a primary interface between machine and experiment and were developed and installed as one project at CERN. Each system has a different geometry and materials as required by the experiment. However, they all have common requirements from the machine, and use many common technologies developed for the project. In this paper we give an overview of the four systems. We explain the technologies that were developed and applied for the installation, test, bakeout and subsequent closure of the experimental vacuum systems. We also discuss lessons learnt from the project.
eng
2010
http://cds.cern.ch/record/1199583/files/mo6rfp010.pdf;
Imported from Invenio.
The LHC phase II collimation project requires beam shock and impact tests of materials used for beam intercepting devices. Similar tests are also of great interest for other accelerator components such as beam entrance/exit windows and protection devices. For this purpose a dedicated High Radiation Material test facility (HiRadMat) is under study. This facility may be installed at CERN at the location of a former beam line. This paper describes the associated beam line which is foreseen to deliver a 450 GeV proton beam from the SPS with an intensity of up to 3×10**13 protons per shot. Different beam line designs will be compared and the choice of the beam steering and diagnostic elements will be discussed, as well as operational issues.
eng
2010
http://cds.cern.ch/record/1203210/files/th6pfp041.pdf;
Imported from Invenio.
Gyr, M
Bartmann, W
Benedikt, M
Goddard, B
Meddahi, M
Koschik, A
Mayani Parás, D
Resonant Third-Integer Extraction from the PS2
For the proposed PS2 accelerator several extraction systems are needed, including a slow third-integer resonant extraction. The requirements are presented together with the conceptual considerations for the sextupole locations and strengths, the separatrices at the extraction elements and the aperture implications for the overall machine. Calculations of the phase space separatrices have been computed with a new code for the physics of slow resonant extraction, which is briefly reviewed. Implications for the extraction equipment design and for the injection-extraction straight section optics are discussed.
eng
2010
http://cds.cern.ch/record/1203209/files/tu6rfp027.pdf;
Imported from Invenio.
Uythoven, J
Bartmann, W
Borburgh, J
Fowler, T
Goddard, B
Meddahi, M
Fast Injection into the PS2
The conceptual considerations of a fast injection system for protons and ions in the proposed PS2 accelerator are presented. Initial design parameters of the injection septum and kicker systems are derived, taking into account rise and fall times, apertures and machine optics. The requirements for an injection dump used for failures are described. Possible limitations and technical issues are outlined.
eng
2010
http://cds.cern.ch/record/1203208/files/tu6rfp030.pdf;
Imported from Invenio.
Bartmann, W
Barranco, J
Benedikt, M
Goddard, B
Kramer, T
Papaphilippou, Y
Vincke, Hel
Beam Loss Control for the Unstripped Ions from the PS2 Charge Exchange Injection
Control of beam losses is an important aspect of the H-injection system for the PS2, a proposed replacement of the CPS in the CERN injector complex. H- ions may pass the foil unstripped or be partially stripped to excited H0 states which may be stripped in the subsequent strong-field chicane magnet. Depending on the choice of the magnetic field, atoms in the ground and first excited states can be extracted and dumped. The conceptual design of the waste beam handling is presented, including local collimation and the dump line, both of which must take into account the divergence of the beam from stripping in fringe fields. Beam load estimates and activation related requirements of the local collimators and dump are briefly discussed.
eng
2010
http://cds.cern.ch/record/1203207/files/th6pfp039.pdf;
Imported from Invenio.
Goddard, B
Bartmann, W
Johnson, D
Danilov, V
Laser Stripping for the PS2 Charge-Exchange Injection System
Laser stripping for an H- injection system into the proposed PS2 accelerator could provide an attractive alternative to the use of a conventional stripping foil. In this paper possible concepts for a 4 GeV laser stripping system are outlined and compared, using either laser or magnetic initial stripping steps and a resonant excitation of the intermediate H0 atom, followed by a final magnetic stripping. Issues of laser power, overall efficiency and emittance growth are discussed.
eng
2010
http://cds.cern.ch/record/1203205/files/tu6rfp028.pdf;
Imported from Invenio.
Hessler, C
Eshraqi, M
Goddard, B
Lombardi, A M
Meddahi, M
The 4 GeV H- Beam Transfer Line from the SPL to the PS2
The proposed new CERN injector chain LINAC4, SPL, PS2 will require the construction of new beam transfer lines. A preliminary design has been performed for the 4 GeV SPL to PS2 H- transfer line. The constraints, beam parameters and geometry requirements are summarised and a possible layout proposed, together with the magnet specifications. First considerations on longitudinal beam dynamics and on beam loss limitations from H- lifetime are presented.
eng
2010
http://cds.cern.ch/record/1203201/files/th6pfp042.pdf;
Imported from Invenio.
Weterings, W
Aiba, M
Borburgh, J
Carli, C
Fowler, T
Goddard, B
Operational considerations for the PSB H- Injection System
For the LINAC4 project the PS Booster (PSB) injection system will be upgraded. The 160 MeV Hbeam will be distributed to the 4 superimposed PSB synchrotron rings and horizontally injected by means of an H- charge-exchange system. Operational considerations for the injection system are presented, including expected beam losses from unwanted field stripping of H- and excited H0 and foil scattering, possible injection failure cases and expected stripping foil lifetimes. Loading assumptions for the internal beam dumps are discussed together with estimates of doses on various components.
eng
2010
http://cds.cern.ch/record/1203023/files/tu6rfp025.pdf;
Imported from Invenio.
Wildner, E
Broggi, F
Cerutti, F
Ferrari, A
Mereghetti, A
Todesco, E
Energy Deposition Patterns in the LHC Inner Triplet and Their Impact on the Phase II Luminosity Upgrade
Recent studies show that the energy deposition for the LHC Phase I luminosity upgrade, aiming at a peak luminosity 2.5×10**34 cm**-2s**-1, can be handled by appropriate shielding. The Phase II upgrade aims at a further increase of peak luminosity by a factor 4, possibly using Nb$_{3}$Sn quadrupoles. This paper describes how the main features of the triplet layout, such as quadrupole lengths, gaps between magnets, and aperture, affect the energy deposition in the insertion. We demonstrate how the energy deposition patterns depend on the triplet lay-out. An additional variable which is taken into account is the choice of conductor, i.e. solutions with Nb-Ti and Nb$_{3}$Sn are compared. Nb$_{3}$Sn technology gives possibilities for increasing the magnet apertures and space for new shielding solutions. Our studies give an indication on the possibility of managing energy deposition for the Phase II upgrade.
eng
2010
http://cds.cern.ch/record/1203022/files/we6pfp025.pdf;
Imported from Invenio.
Sterbini, G
Study of a less invasive LHC early separation scheme
The LHC Early Separation Scheme consists of a four 8 to 15 T-m dipoles (D0s) installed in the two LHC high luminosity experiments. Its aim, in the framework of LHC Phase II Upgrade, is to improve the luminosity by reducing the crossing angle between the two colliding beams, mitigating and controlling at the same time their parasitic interactions. We investigate a less invasive implementation for the detectors (D0 at 14 from the IP) with respect to those already presented (D0 at 4 and 8 m from the IP). The luminosity performance is discussed and a tentative analysis on beam-beam effect impact is given. For the new D0 position, preliminary dipole design and power deposition results are shown.
eng
2010
http://cds.cern.ch/record/1203021/files/mo6pfp053.pdf;
Imported from Invenio.
Bellesia, B
Paz Casas Lino, M
Denz, R
Fernandez-Robles, C
Pojer, M
Saban, R
Schmidt, R
Solfaroli Camillocci, M
Thiesen, H
Vergara Fernández, A
Optimization of the powering tests of the LHC superconducting circuits
The Large Hadron Collider has (LHC) 1572 superconducting circuits which are distributed along the eight 3.5 km LHC sectors [1]. Time and resources during the commissioning of the LHC technical systems were mostly consumed by the powering tests of each circuit. The tests consisted in carrying out several powering cycles at different current levels for each superconducting circuit. The Hardware Commissioning Coordination was in charge of planning, following up and piloting the execution of the test program. The first powering test campaign was carried out in summer 2007 for sector 7-8 with an expected duration of 12 weeks. The experience gained during these tests was used by the commissioning team for minimising the duration of the following powering campaigns to comply with the stringent LHC project deadlines. Improvements concerned several areas: strategy, procedures, control tools, automatization, and resource allocation led to an average daily test rate increase from 25 to 200 tests per day. This paper describes these improvements and details their impact on the operation during the last months of LHC Hardware Commissioning.
eng
2010
http://cds.cern.ch/record/1212118/files/we6rfp049.pdf;
Imported from Invenio.
Garion, C
Kos, H
Design of the CLIC Quadrupole Vacuum Chambers
The Compact Linear Collider, under study, requires vacuum chambers with a very small aperture, of the order of 8 mm in diameter, and with a length up to around 2 m for the main beam quadrupoles. To keep the very tight geometrical tolerances on the quadrupoles, no bake out is allowed. The main issue is to reach UHV conditions (typically 10-9 mbar static pressure) in a system where the vacuum performance is driven by water outgassing. For this application, a thinwalled stainless steel vacuum chamber with two ante chambers equipped with NEG strips, is proposed. The mechanical design, especially the stability analysis, is shown. The key technologies of the prototype fabrication are given. Vacuum tests are carried out on the prototypes. The test set-up as well as the pumping system conditions are presented.
eng
2010
http://cds.cern.ch/record/1225495/files/mo6rfp007.pdf;
Imported from Invenio.
Barnes, M J
Fowler, T
Ravida, G
Design, Testing and Operation of the Modulator for the CTF3 Tail Clipper Kicker
The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues in the CLIC scheme. The extracted drive beam from the combiner ring (CR, of 35 A magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX). A Tail Clipper (TC) is required, in the CR to CLEX transfer line, to allow the duration of the extracted beam pulse to be adjusted. Fours sets of striplines are used for the tail clipper, each consisting of a pair of deflector plates driven to equal potential but opposite polarity. The tail clipper kick must have a fast field risetime, of not more than 5 ns, in order to minimize uncontrolled beam loss. High voltage MOSFETs have been chosen to meet the demanding specifications for the semiconductor switches for the modulator of the tail clipper. This paper discusses the design of the modulator; measurement data obtained during testing and operation of the tail clipper is presented and analyzed.
eng
CLIC;
CTF3;
kicker;
2010
http://cds.cern.ch/record/1225494/files/tu6rfp075.pdf;
Imported from Invenio.