[Show abstract][Hide abstract] ABSTRACT: The Large Hadron Collider has (LHC) 1572 superconducting circuits which are distributed along the eight 3.5 km LHC sectors . 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.
[Show abstract][Hide abstract] ABSTRACT: The LHC is a complex machine requiring more than 7400 superconducting corrector magnets distributed along a circumference of 26.7 km. These magnets are powered in 1446 different electrical circuits at currents ranging from 60Â A up to 600 A. Among the corrector circuits the 600 A corrector magnets form the most diverse and differentiated group. All together, about 60000 high current connections had to be made. A fault in a circuit or one of the superconducting connections would have severe consequences for the accelerator operation. All magnets are wound from various types of Nb-Ti superconducting strands, and many contain parallel protection resistors to by-pass the current still flowing in the other magnets of the same circuit when they quench. In this paper the performance of these magnet circuits is presented, focussing on the quench behaviour of the magnets. Quench detection and the performance of the electrical interconnects will be dealt with. The results as measured on the entire circuits are compared to the test results obtained at the reception of the individual magnets.
[Show abstract][Hide abstract] ABSTRACT: The commissioning activity which started in October 2005 consists in the short circuit tests, the commissioning of the non cryogenic systems and the finally the powering tests of the superconducting components of the LHC. During all theses phases, the infrastructure systems are brought into operation, their performance assessed and validated for the routine operation of the collider. This paper presents the experience gained during this activity and reports recent incidents with some infrastructure systems suggest that they could have a non negligible impact on the downtime of the LHC.
[Show abstract][Hide abstract] ABSTRACT: During hardware commissioning of the Large Hadron Collider (LHC), 8 main dipole circuits are tested at 1.9 K and up to their nominal current. Each dipole circuit contains 154 magnets of 15 m length, and has a total stored energy of up to 1.3 GJ. All magnets are wound from Nb-Ti superconducting Rutherford cables, and contain heaters to quickly force the transition to the normal conducting state in case of a quench, and hence reduce the hot spot temperature. In this paper the performance of the first three of these circuits is presented, focussing on quench detection, heater performance, operation of the cold bypass diodes, and magnet-to-magnet quench propagation. The results as measured on the entire circuits will be compared to the test results obtained during the reception tests of the individual magnets.
[Show abstract][Hide abstract] ABSTRACT: The LHC is an accelerator with unprecedented complexity where the energy stored in magnets and the beams exceeds other accelerators by one-to-two orders of magnitude. To ensure a safe and efficient machine start-up without being plagued by technical problems, a phase of "hardware commissioning" was introduced: a thorough commissioning of technical systems without beam. This activity started in June 2005 with the commissioning of individual systems, followed by operating a full sector, one eighth of the machine; the commissioning is expected to last until spring 2008 when commissioning with beam will start. The LHC architecture allows the commissioning of each of the eight sectors independently from the others, before the installation of other sectors is complete. An important effort went into the definition of the programme and the organization of the coordination in the field, as well as in the preparation of the tools to record and analyze test results. This paper discusses the experience with this approach, presents results from the commissioning of the first LHC sector and gives an outlook for future activities.
[Show abstract][Hide abstract] ABSTRACT: After the commissioning and the first powering of the main circuits in autumn 2001 in its shorter version, the facility was completed to a full cell of LHC in the regular part of an arc and commissioned in July 2002. During this second run, which accumulated more than 4000 hours below 2 K, a very dense experimental program was carried-out to validate the final versions of the technical systems and design choices such as the bus-bar cables running along the magnet cold masses inside the cryostats. The program included the investigation of thermo-hydraulics of quenches, quench propagation, power converter controls and tracking between power converters. The cryogenic process dynamics were studied in length; predictive control techniques were tested and their performance assessed. During a short shutdown starting in December 2002, the facility was stripped of all instrumentation contributing to increased heat loads and heat load measurements will be performed in a last run during the first half of 2003. The paper describes the facility and details the results obtained during the experimental program.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
[Show abstract][Hide abstract] ABSTRACT: String 2 is a full-size model of a regular cell in an LHC arc. In the first phase, three dipole magnets and two quadrupole magnets have been assembled in String 2 and commissioning started in April 2001. By the beginning of 2002 three pre-series dipole magnets will be added to complete the cell. As for its predecessor String 1, the facility was built to individually validate the LHC systems and to investigate their collective behavior for normal operation with the magnets at a temperature of 1.9 K, during transients as well as during exceptional conditions. String 2 is a precious milestone before installation and commissioning of the first LHC sector (1/8 of the machine) in 2004, with respect to infrastructure, installation, tooling and assembly procedures, testing and commissioning of individual systems, as well as the global commissioning of the technical systems. This paper describes the commissioning, and retraces the first powering history.
IEEE Transactions on Applied Superconductivity 04/2002; · 1.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: String 2 is a full-size model of an LHC cell of the regular part
of the arc. It is composed of six dipole magnets with their correctors,
two short straight sections with their orbit and lattice corrector
magnets, and a cryogenic distribution line running alongside the
magnets. The commissioning of String 2 Phase 1, with one half-cell and
the following quadrupole, has started in April 2001. As for String 1,
the facility was built to individually validate the LHC systems and to
investigate their collective behaviour during normal operation
(pumpdown, cool-down and powering) as well as during exceptional
conditions such as quenches. String 2 is a stepping stone towards the
commissioning of the first sector (one eight of LHC) planned for 2004.
It is expected to yield precious information on the infrastructures, the
installation, the tooling and the procedures for the assembly, the
testing and the commissioning of the individual systems, as well as the
global commissioning of the technical systems. This paper describes the
procedures followed for the commissioning and details the preparation
for the first cool-down and for the powering
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
[Show abstract][Hide abstract] ABSTRACT: The numerous complex activities required to prepare the
cryomagnets for the installation in String 2 are described. These
include the configuration of the mechanical interfaces, the conditioning
of the beam tubes, the installation of beam screens and the
instrumentation as well as the final checks. The preparation of the
cryomagnets for String 2 has been a dress rehearsal for the preparation
that the cryomagnets will undergo before their installation in the
tunnel. After a description of the interconnection procedures of the
components for String 2, the tests carried-out to release the String for
operation are described. A brief account of the lessons learnt is also
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
[Show abstract][Hide abstract] ABSTRACT: String 1, with one twin aperture quadrupole and three twin
aperture 10-m dipoles (MB1, MB2 and MB3) powered in series and operating
at 1.9 K, has recently been dismantled after four years of operation
interrupted by technical stops and shutdowns for upgrading or exchanging
equipment. Following the validation of the main LHC systems (cryogenics,
magnet protection, vacuum, powering and energy extraction) the
experimental programme was oriented towards the optimisation of the
design and the observation of artificially induced fatigue effects. The
design study for String 2 has been completed. This facility, which will
be commissioned in December 2000, is composed of two LHC half-cells each
consisting of one twin aperture quadrupole and three 15-m twin aperture
dipoles. A cryogenic distribution line housing the supply and recovery
headers runs parallel to the string of magnets. An electrical feedbox is
used to power, with high temperature superconductor current leads, the
circuits as in the regular part of an LHC arc. This paper reviews the
experiments carried-out with String 1 and summarises the results
obtained after more than 12800 hours of operation below 1.9 K and 172
quenches. It also describes the layout and the components of String 2
and explains the objectives pursued by its designers
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
[Show abstract][Hide abstract] ABSTRACT: As a continuation of the experimental program carried-out with String 1, project management decided toward the end of 1995 to construct an LHC prototype Full-Cell, also known as String 2. The present document reports on the outcome of the one-year design effort by the community of specialists contributing to the LHC Prototype Full-Cell: it informs specialists on the boundary areas with other syste ms and conveys to the general public a description of the facility.
[Show abstract][Hide abstract] ABSTRACT: The first version of the LHC Prototype Half-Cell has been in
operation since February 1995. It consists of one quadrupole and three
10-m twin aperture dipole magnets which operate at 1.9 K. One electrical
circuit powers all the magnets in series. This experimental set-up has
been used to observe and study phenomena which appear when the systems
are assembled in one unit and therefore influence one another
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
[Show abstract][Hide abstract] ABSTRACT: The LHC Conceptual Design Report issued on 20th October 1995 (CERN/AC/95-05 (LHC) - nicknamed "Yellow Book") introduced significant changes to some fundamental features of the LHC standard half-cell, composed of one quadrupole, 3 dipoles and a set of corrector magnets. A separate cryogenic distribution line was introduced, which was previously inside the main cryostat. The dipole length has been increased from 10 to 15 m and independent powering of the focusing and defocusing quadrupole magnets was chosen. Individual quench protection diodes were introduced in magnets interconnects and many auxiliary bus bars were added to feed in series the various families of correcting superconducting magnets. The various highly intricate basic systems such as: cryostats and cryogenics feeders, superconducting magnets and their electrical feeding and protection, vacuum beam screen and its cooling, support and alignment devices have been redesigned, taking into account the very tight space available. These space constraints are given by the necessity to have maximum integral bending field strength for maximum LHC energy, and the existing LHC tunnel. Finally, cryogenic and vacuum sectorisation have been introduced to reduce downtimes and facilitate commissioning.
[Show abstract][Hide abstract] ABSTRACT: The first version of the LHC prototype half-cell has been in operation since February 1995. It consists of one quadrupole and three 10-m twin aperture dipole magnets which operate at 1.8 K. This experimental set-up has been used to observe and study phenomena which appear when the systems are assembled in one unit and influence one another. The 18-month long experimental program has validated the cryogenic system and yielded a number of results on cryogenic instrumentation, magnet protection and vacuum in particular under non-standard operating conditions. The program was recently complemented by the cycling experiment: it consisted in powering the magnets following the ramp rates which will be experienced by the magnets during an LHC acceleration. In order to simulate 10 years of routine operation of LHC, more than 2000 1-hour cycles were performed interleaved with provoked quenches. The objective of this experiment was to reveal eventual flaws in the design of components. The prototype half-cell performed to expectations showing no sign of failure of fatigue of components for more than 2000 cycles until one of the dipoles started exhibiting an erratic quench behavior.
[Show abstract][Hide abstract] ABSTRACT: The increasing presence of industrial control systems in
high-energy physics laboratories raises the questions of their
integration into the general control infrastructure and the organisation
of the operation of the associated equipment. The method of integration
is dictated by the adopted operation strategy; in turn, the latter
determines the former. After an introduction to industrial control
systems this paper describes different communication mechanisms with
alien systems provided by manufacturers and reports on experience
acquired at CERN. The major operation strategies in terms of level of
coupling are described and their requirements on the integration methods
Particle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995
[Show abstract][Hide abstract] ABSTRACT: With its chain of accelerators and its large experimental physics
detectors, CERN is one of the world's most important research centres
for particle physics. CERN builds and operates a number of classical and
advanced technical utilities to serve its research activities. These
utilities are generally equipped with industrial control components
purchased with the equipment itself. This paper describes some of the
utilities and their controls and proposes a strategy for the integration
of diverse industrial control systems into a coherent industrial
environment of communication and supervision.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/1994; · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The magnetic measurement of more than 1300 LHC dipoles comprises
the content of higher harmonic field components, field direction and
field integrals. The measurements will be carried out along a warm bore
installed inside the magnet cold bore, thus allowing the use of rotating
coils at room temperature. This coil, together with Hall and NMR
detectors is mounted at one end of a 12.5 m long shaft which is
specially designed for very high rotational stiffness and which is
controlled from its far end by a motor, an angular encoder and a level
meter, all standard components placed outside the magnetic field without
space restrictions. Particular emphasis has been put on the
user-friendliness of the bench and its automated, computer-controlled
operation requiring a minimum of staff, an important issue during
production measurements of large series of magnets. The bench and its
performance and precision achieved during its commissioning are
IEEE Transactions on Magnetics 08/1994; · 1.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: At CERN a large number of systems providing services (cooling and ventilation, cryogenics, electricity distribution, personnel and building safety, etc.) are controlled by industrial PLCs. A commercial supervision package is used as a gateway to the accelerator control system. The integration of such a system in the CERN accelerator control environment addresses issues such as the connection to control-rooms and desktop computers, alarm logging and remote or alien man-machine interfaces. The paper describes the components of the system and reports the first operational experience.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/1994; · 1.14 Impact Factor