| Paper | Title | Page |
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| MOPEC003 | Operational Experience during Initial Beam Commissioning of the LHC | 456 |
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After the incident on the 19th September 2008 and more than one year without beam the commissioning of the LHC started again on November 20, 2009. Progress was rapid and collisions under stable beam conditions were established at 1.2 TeV within 3 weeks. In 2010 after qualification of the new quench protection system the way to 3.5 TeV was open and collisions were delivered at this energy after a month of additional commissioning. This paper describes the experiences and issues encountered during these first periods of commissioning with beam. |
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| MOPEC005 | Kick Response Measurements during LHC Injection Tests and Early LHC Beam Commissioning | 462 |
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The transfer lines from the SPS to the LHC, TI2 and TI8, with a total length of almost 6km are the longest ones in the world. For that reason even small systematic optics errors are not negligible because they add up and result in an injection mismatch in the LHC. Next to other lattice measurement methods Kick-response measurements were the most important sources of information during the early phases of beam commissioning of these transfer lines and the LHC ring. This measurement technique was used to verify orbit-corrector and BPM gains as well as to sort out optics errors. Furthermore fits to off-momentum kick response turned out to be an appropriate method to establish a model for systematic errors of the transfer line magnets. This paper shortly describes the tools and methods developed for the analysis of the taken data and presents the most important results of the analysis. |
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| MOPEC006 | JMAD - Integration of MADX into the JAVA World | 465 |
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MADX (Methodical Accelerator Design) is the de-facto standard software for modeling accelerator lattices at CERN. This feature-rich software package is implemented and maintained in the programming languages C and FORTRAN. Nevertheless the controls environment of modern accelerators at CERN, e.g. of the LHC, is dominated by JAVA applications. A lot of these applications, for example for lattice measurement and fitting, require a close interaction with the numerical models, which are all defined by the use of the proprietary MADX scripting language. To close this gap an API to MADX for the JAVA programming language (JMAD) was developed. Already the current implementation provides access to a large subset of the MADX capabilities (e.g. twiss-calculations, matching or querying and setting arbitrary model parameters) without any necessity to define the models in yet another environment. This paper describes shortly the design of this project as well as the current status and some usage examples. |
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| MOPEC007 | Operational Experience during the LHC Injection Tests | 468 |
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Following the LHC injection tests of 2008, two injection tests took place in October and November 2009 as preparation for the LHC restart on November 20, 2009. During these injection tests beam was injected through the TI2 transfer line into sector 23 of ring 1 and through TI8 into the sectors 78, 67 and 56 of ring 2. The beam time was dedicated to injection steering, optics measurements and debugging of all the systems involved. Because many potential problems were sorted out in advance, these tests contributed to the rapid progress after the restart. This paper describes the experiences and issues encountered during these tests as well as related measurement results. |
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| TUPEB062 | Beam Commissioning and Performance Characterisation of the LHC Beam Dump Kicker Systems | 1659 |
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The LHC beam dump system was commissioned with beam in 2009. This paper describes the operational experience with the kicker systems and the tests and measurements to qualify them for operation. The kicker performance was characterized with beam by measurements of the kicker waveforms using bunches extracted at different times along the kicker sweep. The kicker performance was also continuously monitored for each pulse with measurement and analysis of each kick pulse, allowing diagnostic of errors and of long-term drifts. The results are described and compared to the expectations. |
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| TUPEB064 | Comparison of Emittance Growth for 450 GeV Rigidity Pb82+ Ions and p+ in Thin Scatterers | 1665 |
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The beam profile screens in the long SPS to LHC transfer lines were used to measure with high precision the emittance growth arising from scattering. The effective thickness of the scatterer could be varied by adding thick Al2O3 fluorescent screens, with the emittance measurement made using very thin Ti OTR screens. The technique allows the intrinsic variation in the emittance from the injector chain to be factored out of the measurement, and was applied to Pb82+ and protons, both with 450 GeV rigidity. The results are presented and the possible applications to the accurate benchmarking of nuclear interaction codes discussed. |
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| TUPEB065 | Phase-dependant Coupling at Injection from Tilt Mismatch between the LHC and its Transfer Lines | 1668 |
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The tilt mismatch between the LHC and its transfer lines arises from the use of combined horizontal and vertical bends. The mismatch gives rise to several subtle optical effects, including a coupling at injection into the LHC which depends on the phase of the oscillation amplitude at the injection point. This coupling was observed for the first time in 2008, and in 2009 dedicated measurements were made. The results are described and compared with the expectations, and the operational implications detailed. |
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| TUPEB066 | Injection Beam Loss and Beam Quality Checks for the LHC | 1671 |
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The quality of the injection into the LHC is monitored by a dedicated software system which acquires and analyses the pulse waveforms from the injection kickers, and measures key beam parameters and compares them with the nominal ones. The beam losses at injection are monitored on many critical devices in the injection regions, together with the longitudinal filling pattern and maximum trajectory offset on the first 100 turns. The paper describes the injection quality check system and the results from LHC beam commissioning, in particular the beam losses measured during injection at the various aperture limits. The results are extrapolated to full intensity and the consequences are discussed. |
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| TUPEB067 | Beam Commissioning of the Injection Protection Systems of the LHC | 1674 |
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The movable LHC injection protection devices in the SPS to LHC transfer lines and downstream of the injection kicker in the LHC were commissioned with low-intensity beam. The different beam-based alignment measurements used to determine the beam centre and size are described, together with the results of measurements of the transverse beam distribution at large amplitude. The system was set up with beam to its nominal settings and the protection level against various failures was determined by measuring the transmission and transverse distribution into the LHC as a function of oscillation amplitude. Beam losses levels for regular operation were also extrapolated. The results are compared with the expected device settings and protection level, and the implications for LHC operation discussed. |
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| TUPEB068 | Aperture Measurements of the LHC Injection Regions and Beam Dump Systems | 1677 |
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The commissioning of the beam transfer systems for LHC included detailed aperture measurements in the injection regions and for the beam dump systems. The measurements, mainly single pass, were made using systematic scans of different oscillation phases and amplitudes, and the results compared with the expectations from the physical aperture model of the LHC. In this paper the measurements and results are presented and compared with the specified apertures in these critical areas. |
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| TUPEB069 | Results of 2009 Optics Studies of the SPS to LHC Transfer Lines | 1680 |
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In 2008, the SPS-to-LHC transfer line operation allowed for the first time to perform beam measurements in the last part of the lines and into the LHC. Beam parameters were measured and compared with expectation. Discrepancies were observed in the dispersion matching into the LHC, and also in the vertical phase advance along the line. In 2009, extensive theoretical and simulation work was performed in order to understand the possible sources of these discrepancies. This allowed establishing an updated model of the beam line, taking into account the importance of the full magnetic model, the limited dipole corrector strengths and the precise alignment of beam elements. During 2009, beam time was allocated in order to perform further measurements, checking and refining the optical model of the transfer line and LHC injection region and validating the different assumptions. Results of the 2009 optics measurements and comparison with the beam specification and model are presented. |
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| MOPEC009 | LHC Abort Gap Monitoring and Cleaning | 474 |
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Unbunched beam is a potentially serious issue in the LHC as it may quench the superconducting magnets during a beam abort. Unbunched particles, either not captured by the RF system at injection or leaking out of the RF bucket, will be removed by using the existing damper kickers to excite resonantly the particles in the abort gap. Following beam simulations, a strategy for cleaning the abort gap at different energies was proposed. The plans for the commissioning of the beam abort gap cleaning are described, and the first results from the beam commissioning are presented. |