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ABSTRACT: More than 1100 quadrupole magnets of different types are needed for the Large Hadron Collider (LHC) which is in the construction stage at CERN. The most challenging parameter to measure on these quadrupoles is the integrated gradient (Gdl). An absolute accuracy of 0.1% is needed to control the beta beating. In this paper we briefly describe the whole set of equipment used for Gdl measurements: Automated Scanner system, Single Stretched Wire system and Twin Coils system, concentrating mostly on their absolute accuracies. Most of the possible inherent effects that can introduce systematic errors are discussed along with their preventive methods. In the frame of this qualification some of the magnets were tested with two systems. The results of the intersystem cross-calibrations are presented. In addition, the qualification of the measurement system used at the magnet manufacturer's is based on results of more than 40 quadrupole assemblies tested in cold conditions at CERN and in warm conditions at the vendor site
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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S. Sanfilippo,
J. Beauquis,
L. Bottura,
M. Buzio,
M. Coccoli,
J. Garcia-Perez,
P. Pugnat,
N. Sammut,
A. Siemko, N. Smirnov,
A. Stafiniak,
E. Wildner
[show abstract]
[hide abstract]
ABSTRACT: The Short Straight Section (SSS) for the Large Hadron Collider arcs, containing in a common cryostat the lattice quadrupoles and correction magnets, have now entered series production. The foremost features of the lattice quadrupole magnets are a two-in-one structure containing two 56 mm aperture, two-layers coils wound from 15.1 mm wide NbTi cables, enclosed by the stainless steel collars and ferromagnetic yoke, and inserted into the inertia tube. Systematic cryogenic tests are performed at CERN in order to qualify these magnets with respect to their cryogenic and electrical integrity, the quench performance and the field quality in all operating conditions. This paper reports the main results obtained during tests and measurements in superfluid helium. The electrical characteristics, the insulation measurements and the quench performance are compared to the specifications and expected performances for these magnets. The field in the main quadrupole is measured using three independent systems: 10-m long twin rotating coils, an automatic scanner, and single stretched wire. A particular emphasis is given to the integrated transfer function which has a spread of around 12 units rms in the production and is a critical issue. The dodecapole harmonic component, which required trimming through a change in coil shims, is also discussed. Finally, the magnetic axis measurements at room temperature and at 1.9 K, providing the nominal vertical shift for installation are reported
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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M. Buzio,
L. Bottura,
G. Brun,
G. Fievez,
P. Galbraith,
J.G. Perez,
R. Lopez,
A. Masi,
S. Russenschuck, N. Smirnov,
A. Tikhov,
L. Walckiers
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ABSTRACT: This paper describes the design and operation of the "Polarity Checker", a scanning probe designed to check multipole field order, type and polarity of superconducting LHC magnets. First we introduce the measurement method, based on the harmonic analysis of the radial field component picked up by a rotating Hall sensor at different current levels. Then we describe the hardware and the software of the system, which features automatic powering, data acquisition and treatment, discussing the achieved sensitivity and performance. Finally we provide a summary of the test results on the first 505 cryoassemblies, showing how the system was usefully employed to detect some potentially harmful connection errors
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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M. Buzio,
J. Beauquis,
L. Bottura,
M. Coccoli,
G. Deferne,
N. Krotov,
E. Laface,
A. Ruccio,
J.G. Perez,
D. Missiaen,
P. Schnizer, N. Smirnov,
E. Wildner,
P. Winkes,
L. Walckiers
[show abstract]
[hide abstract]
ABSTRACT: This paper contains a summary of the results of the magnetic and mechanical alignment tests performed at CERN on the first 111 arc Short Straight Sections. These include the mechanical axis of the Cold Bore Tube at room temperature, the magnetic axis of main quadrupoles and correctors at both room and cryogenic temperature, and the field direction of the main quadrupoles. The measurements show that the quality of the assemblies is generally within the requirements for the machine
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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ABSTRACT: We review 19 measurement systems for the magnetic axis of accelerator magnets, used to align machine components. First, we provide some background information and we describe briefly the instruments and methods used for the magnetic and the geometric measurements. For all systems we give then a performance summary in terms of magnet parameters and measurement uncertainties. The dataset is analyzed statistically to identify the parameter with the most influence on the total uncertainty, which is magnet length. Finally we derive scaling laws relating uncertainties to magnet's parameters, and we discuss the relative performance of the various methods
Instrumentation and Measurement Technology Conference, 2006. IMTC 2006. Proceedings of the IEEE; 05/2006
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N.J. Sammut,
E. Benedico-Mora,
L. Bottura,
P. Galbraith,
D. Giloteaux,
G. Greco,
M. Haverkamp,
M. Marchesotti,
A. Masi,
J. Micallef,
T. Pieloni, N. Smirnov,
A. Tikhov
[show abstract]
[hide abstract]
ABSTRACT: The decay and snapback of the magnetic field multipoles in superconducting particle accelerators like the Large Hadron Collider (LHC) could result in a significant particle beam loss unless adequately compensated. Whilst standard instrumentation used to measure the field quality of the superconducting magnets is good enough to measure the harmonic decay, it is not fast enough to measure the snapback. Therefore, a state of the art instrument was recently developed at CERN to measure the most important harmonics with a high measurement frequency and hence improve the understanding of the snapback phenomenon. In this paper we describe the instrument's principle of operation, its mechanical arrangement, its compensation system and its digital acquisition system. We also compare the performance of two different techniques implemented to achieve the necessary measurement resolution of 6 orders of magnitude lower than the main superimposed dipole field
Instrumentation and Measurement Technology Conference, 2006. IMTC 2006. Proceedings of the IEEE; 05/2006
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S. Sanfilippo, N. Smirnov,
P. Schnizer,
N. Sammut,
P. Pugnat,
L. Bottura,
A. Siemko,
M. Calvi,
V. Chohan,
A. Stafiniak,
L. Walckiers,
P. Hagen,
E. Todesco,
T. Tortschanoff,
F. Simon,
M. Durante
[show abstract]
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ABSTRACT: The series testing at 1.9 K of the 360 Short Straight Sections (SSS) for the Large Hadron Collider have started at CERN in September 2003. The SSS contain the lattice quadrupoles and correction magnets in a common cryostat. The lattice quadrupoles feature two collared coils with 56 mm bore assembled in a common yoke. The coils are wound in two-layers from 15.1 mm wide NbTi cable, insulated with polyimide tape. The paper reviews the main test results performed in superfluid helium. The magnetic field and magnetic center position of the quadrupoles and associated correctors were measured with two independent systems, namely an automated scanner and a single stretched wire technique. The quench training, the field quality and the magnetic alignment measurements are presented and discussed in terms of the specifications and expected performances of these magnets in the LHC. We discuss in detail the field quality in terms of multipole errors measured at injection and nominal field and decomposed into geometric and persistent current magnetization errors. Warm/cold correlation for the geometric multipoles and the magnetic axis is also presented.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: More than 470 twin aperture lattice quadrupoles are needed for the large hadron collider (LHC) under construction at CERN. The lattice quadrupole, assembled with correction magnets in its helium enclosure - the cold mass and integrated in a common cryostat called the short straight section (SSS). All SSS cold mass prototypes have been developed and built by CEA (Saclay) in collaboration with CNRS (Orsay, France). The last SSS prototype (SSS5) was used to investigate the behavior of the magnetic axis through various steps of the installation cycle for the series quadrupoles: including transportation, thermal-cycles, and being lowered into the tunnel. Results of extensive measurements before and after each of these stages are presented here, showing that the effect of transport is weak and within the window of measurement resolution. Also shown is that the long-term stability observed during two years is comparable with the requirements from magnet tolerances. To minimize systematic errors, all tests were performed with two independent measurement systems: single-stretched wire (SSW) and automated scanner. A brief description of these systems is given, concentrating mostly on their accuracies. In addition, establishment of a reliable cold-warm correlation for the magnetic axis position is a very important issue because it can reduce the percentage of cold tests. Though this correlation will be based on proper statistics at the beginning of series production, magnetic axis behavior during thermal-cycle has been investigated for the SSS5 prototype, and these results are also presented.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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ABSTRACT: Considerable effort is spent at CERN on magnetic alignment measurements of main lattice LHC dipoles, including field direction, curved axis shape and position of in-built correctors, essential to verify the geometry of the assembly and to guarantee correct installation with respect to the reference beam orbit. The current baseline includes measurements of a statistically relevant percentage of cold masses and cryostated magnets before, during and after cryogenic tests. For this, we use a range of scanning probes based either on harmonic coils or fixed coils in AC mode, with laser and telescope trackers to measure position with respect to cryostat fiducials. The dipole is usually powered in "quadrupole mode" to create a convenient magnetic reference. In this paper, we first recall objectives, equipment and methods. Then, we report the status of the test activities, showing results obtained on the first pre-series dipoles, including cross-checks of various measurement systems and correlation between measurements at room and cryogenic temperatures.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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A. Siemko,
O. Berrig,
L. Bottura,
M. Buzio,
V. Chohan,
E. Floch,
V. Granata,
M. Pojer,
P. Pugnat,
L. Rossi,
S. Sanfilippo, N. Smirnov,
J. Vlogaert,
L. Walckiers
[show abstract]
[hide abstract]
ABSTRACT: The preseries production of the LHC main superconducting dipoles is presently being tested at CERN. The foremost features of these magnets are: twin structure, six block two layer coils wound from 15.1 mm wide graded NbTi cables, 56 mm aperture, polyimide insulation and stainless steel collars. The paper reviews the main test results of magnets tested to day in both normal and superfluid helium. The results of training performance, magnet protection, electrical integrity and the field quality are presented in terms of the specifications and expected performance of these magnets in the future accelerator.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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ABSTRACT: During beam injection the components of the magnetic field inside the magnets decay in time. At the re-start of the ramping, this decay is cancelled resulting in a fast change of the harmonics called "snapback". This sudden variation affects mainly the sextupole and decapole components and can induce significant changes in the machine chromaticity, thus causing particle beam loss. Standard magnetic measurements with rotating coils do not have a sufficient time resolution to properly characterize the snapback phenomenon. A system based on Hall probes has been developed from an existing prototype to measure with a moderate acquisition frequency (3-10 Hz) the decay and snapback of the sextupole and, for the first time, of the decapole fields. The present system also provides local measurements of these field harmonics along a wavelength of the superconducting cable twist pitch. In this paper, we describe the assembly features of this detector and of the measurement chain. The performances are demonstrated based on preliminary measurements performed on the LHC pre-series dipoles in operating conditions.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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[hide abstract]
ABSTRACT: When investigating the quality of a magnetic measurement system, one observes difficulties to identify the "trouble maker" of such a system as different effects can yield similar influences on the measurement results. We describe a tool in this paper that allows to investigate numerically the effects produced by different imperfections of components of such a system, including, but not limited to: vibration and movements of the rotating coil, influence of electrical noise on the system, angular encoder imperfections. This system can simulate the deterministic and stochastic parts of those imperfections. We outline the physical models used that are generally based on experience or first principles. Comparisons to analytical results are shown. The modular structure of the general design of this tool permits to include new modules for new devices and effects.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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[hide abstract]
ABSTRACT: We discuss the method developed for the verification of alignment of magnetic elements contained in the LUC cryodipole cold mass during series tests at CERN. First, we outline motivations and requirements and then we focus on test strategy, equipment and procedures. Our goal is to express the magnetic field of the dipole and of its associated correctors w.r.t. the reference beam line, not accessible during cryogenic tests. To do so, we use traveling harmonic coil probes ("moles") that allow simultaneous measurement of the field and of the coil position. A laser tracker is used to relate these measurements to fiducials. In the dipole, the axis of the quadrupole configured dipole is used as an intermediate reference for the transfer. We provide details on the devices used for measurements in warm and cold conditions, some results from prototypes and pre-series dipoles and an assessment of the precision expected for the series tests.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: More than 400 twin aperture lattice quadrupoles are needed for the Large Hadron Collider (LHC) which is under construction at CERN. The main quadrupole is assembled with correction magnets in a common cryostat called the Short Straight Section (SSS). We plan to measure all SSSs in cold conditions with an unprecedented accuracy: integrated gradient of the field within 150 ppm, harmonics in a range of 1 to 5 ppm, magnetic axis of all elements within 0.1 mm and their field direction within 0.2 mrad. In this paper we describe the automatic measurement system that we have designed, built, and calibrated. Based on the results obtained on the two first prototypes of the SSSs (SSS3 and SSS4) we show that this system meets all above requirements.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The construction of three prototype arc quadrupoles for the LHC
machine has been concluded successfully. These magnets underwent warm
and cold magnetic measurements as well as many other tests, both in
CEA-Saclay's laboratory and at CERN. Their training qualifies them for
use in the LHC machine and their measured field quality points to only
very minor corrections. An excellent correlation is found between warm
and cold magnetic measurements. The prototype quadrupole design has been
fully retained for the series fabrication of the 400 magnets and their
cold masses by industry. This paper describes the main tests and
measurement results of all three prototypes. It further explains the
logistics for the manufacturing of the series of cold masses. These cold
masses contain not only the main quadrupole but also different
combinations of corrector magnets. Thus, together with variants imposed
by the cryogenic configuration of the machine, 40 different types of
cold masses have to be fabricated by the firm, to which the contract has
been adjudicated
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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[show abstract]
[hide abstract]
ABSTRACT: In superconducting particle accelerators a fast change of the
magnetic field occurs during the first few seconds after the start of an
energy ramp. Standard magnetic measurements using a coil rotating at 1
Hz do not have the time resolution required to completely resolve this
phase, usually called snapback. For this reason we have developed a new
and fast system dedicated to sextupole measurements. The basic component
consists of three Hall plates mounted on a ring. In an ideal case this
arrangement compensates the main dipole field and produces a signal
proportional to the sextupole only. Mechanical tolerances and
differences in the sensitivity of the Hall plates are compensated by
instrumentation amplifiers and an in situ fine adjustment of the probe
orientation. Using this hybrid compensation technique we have measured
sextupole variations in an LHC dipole prototype during snapback at a
rate of 5 Hz. In this paper we present details on the device and the
results of our measurements
IEEE Transactions on Appiled Superconductivity 04/2000; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The construction of three prototype arc quadrupoles for the LHC machine has been concluded successfully. These magnets underwent warm and cold magnetic measurements as well as many other tests, both in CEA-Saclay's laboratory and at CERN. Their training qualifies them for use in the LHC machine and their measured field quality points to only very minor corrections. An excellent correlation is found between warm and cold magnetic measurements. The prototype quadrupole design has been fully retained for the series fabrication of the 400 magnets and their cold masses by industry. This paper describes the main tests and measurement results of all three prototypes. It further explains the logistics for the manufacturing of the series of cold masses. These cold masses contain not only the main quadrupole but also different combinations of corrector magnets. Thus, together with variants imposed by the cryogenic configuration of the machine, 40 different types of cold masses have to be fabricated by the firm, to which the contract has been adjudicated.
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[show abstract]
[hide abstract]
ABSTRACT: The superconducting twin aperture main dipole magnets of the LHC accelerator are equipped with pairs of sextupole and decapole correctors at their ends. Similarly, octupole correctors are aligned at t he end of the main quadrupole magnets. Dedicated stations have been built for tests of these correctors at room temperature as well as superfluid helium temperature. Measurements of the training behav iour and of the magnetic field quality are routinely performed. The search for the magnetic axis and the transfer of its position to fiducials are performed at room temperature. A description and the performances obtained with these two benches are also presented.
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M Buzio,
J Beauquis,
L Bottura,
M Coccoli,
G Deferne,
N Krotov,
E Laface,
A Ruccio,
J García-Pérez,
D Missiaen,
P Schnizer, N Smirnov,
E Wildner,
P Winkes
[show abstract]
[hide abstract]
ABSTRACT: This paper contains a summary of the results of the magnetic and mechanical alignment tests performed at CERN on the first 111 arc Short Straight Sections. These include the mechanical axis of the Cold Bore Tube at room temperature, the magnetic axis of main quadrupoles and correctors at both room and cryogenic temperature, and the field direction of the main quadrupoles. The measurements show that the quality of the assemblies is generally within the requirements for the machine.
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N J Sammut,
E Benedico-Mora,
L Bottura,
P Galbraith,
D Giloteaux,
G Greco,
M Haverkamp,
M Marchesotti,
A Masi,
J Micallef,
T Pieloni, N Smirnov,
A Tikhov
[show abstract]
[hide abstract]
ABSTRACT: The decay and snapback of the magnetic field multipoles in superconducting particle accelerators like the Large Hadron Collider (LHC) could result in a significant particle beam loss unless adequately compensated. Whilst standard instrumentation used to measure the field quality of the superconducting magnets is good enough to measure the harmonic decay, it is not fast enough to measure the snapback. Therefore, a state of the art instrument was recently developed at CERN to measure the most important harmonics with a high measurement frequency and hence improve the understanding of the snapback phenomenon. In this paper we describe the instrument's principle of operation, its mechanical arrangement, its compensation system and its digital acquisition system. We also compare the performance of two different techniques implemented to achieve the necessary measurement resolution of 6 orders of magnitude lower than the main superimposed dipole field.
