| Paper | Title | Page |
|---|---|---|
| MPPT040 | The LHC Magnetic Field Model | 2648 |
|
||
| The compensation of the dynamic field changes during the proton and ion beam injection and acceleration in the LHC requires an accurate forecast and an active control of the magnetic field in the accelerator. The LHC Magnetic Field Model is the core of this magnetic prediction system. This open loop control scheme will provide the desired field components at a given time, magnet operating current, magnet ramp-rate, magnet temperature and magnet powering history to the required precision. The model is based on the identification and physical decomposition of the effects that contribute to the total field in the magnet aperture of the LHC dipoles. By using data obtained from series measurements, these components are then quantified theoretically or empirically depending on the complexity of the physical phenomena involved. This paper presents the developments of the newly fine-tuned magnetic field model and evaluates its accuracy, reproducibility and predicting capabilities. | ||
| MPPT041 | Improvement of the Geometrical Stability of the LHC Cryodipoles when Blocking the Central Support Post | 2675 |
|
||
| The LHC will be composed of 1232 horizontally curved 16 meter long super-conducting dipole magnets cooled at 1.9K, supported within their vacuum vessel by three Glass Fiber Resin Epoxy (GFRE) support posts. The two support posts at the dipole extremities were initially designed free to slide longitudinally with respect to the vacuum vessel and the central support post was designed free to slide transversally. However the magnet shape did not retain the tight geometrical tolerances, of the order of fractions of mm, imposed by machine aperture and magnetic corrector centering requirements. Thereafter a modification to the supporting system, removing the initial transversal degree of freedom of the lower flange of the central support post with respect to the vacuum vessel, was designed and implemented. This paper describes the design of the magnet/cryostat interface with and without blockage of the central support post, analyzes the additional mechanical loads related to the modification and reviews the experimental results with respect to the requirements for beam aperture and magnetic corrector centering. | ||
| MPPT042 | Field Quality and Alignment of the Series Produced Superconducting Matching Quadrupoles for the LHC Insertions | 2738 |
|
||
| The production of the superconducting quadrupoles for the LHC insertions is advancing well and about half of the magnets have been produced. The coil size and field measurements performed on individual magnets both in warm and cold conditions are yielding significant results. In this paper we present the procedures and results of steering the series production at the magnet manufacturers and the assembly of cold masses at CERN. In particular, we present the analysis of warm-cold correlations and hysteresis of the main field multipoles, the correlation between coil sizes and geometrical field errors and the effect of permeability of magnet collars. The results are compared with the target errors for field multipoles and alignment. | ||
| MPPT043 | Low-Beta Quadrupole Designs for the LHC Luminosity Upgrade | 2795 |
|
||
| Several candidate scenarios are considered for the upgrade of the LHC insertions in view of increasing the luminosity in excess of 1034 cm-2s-1. In all cases, superconducting low-beta quadrupoles with apertures in the range of 90-110 mm are required in view of increased heat loads and beam crossing angles. We present possible low-beta quadrupole designs based on Nb3Sn and NbTi superconducting cables, including existing LHC-class superconductors, present scaling laws for the magnet parameters and discuss relative advantages of the underlying triplet layouts. | ||
| MPPT044 | The Construction of the Low-Beta Triplets for the LHC | 2798 |
|
||
| The performance of the LHC depends critically on the low-beta triplets, located on either side of the four interaction points. Each triplet consists of four superconducting quadrupole magnets, which must operate reliably at up to 215 T/m, sustain extremely high heat loads and have an excellent field quality. A collaboration of CERN, Fermilab and KEK was set up in 1996 to design and build the triplet systems, and after nine years of joint effort the production will be completed in 2005. We retrace the main events of the project and present the design features and performance of the low-beta quadrupoles, built by KEK and Fermilab, as well as of other vital elements of the triplet. The experience in assembly of the first triplet at CERN and plans for tunnel installation and commissioning in the LHC are also presented. Apart from the excellent technical results, the construction of the LHC low-beta triplets has been a highly enriching experience combining harmoniously the different competences and approaches to engineering in a style reminiscent of physics experiment collaborations, and rarely before achieved in accelerator building. | ||
| MPPT045 | The Assembly of the LHC Short Straight Sections (SSS) at CERN: Project Status and Lessons Learned | 2890 |
|
||
| The series production of the LHC SSS has started in the beginning of 2004 and is foreseen to last until end 2006. The production consists in the assembly of 474 cold masses housing superconducting quadrupoles and corrector magnets within their cryostats. 87 cold mass variants, resulting from various combinations of main quadrupole and corrector magnets, have to be assembled in 55 cryostat types, depending on the specific cryogenic and electrical powering schemes required by the collider topology. The assembly activity features the execution of more than 5 km of leak-tight welding on 20-bar design pressure cryogenic lines in stainless steel and aluminium, according to high qualification standards and undergoing severe QA inspections. Some 2500 leak detection tests, using He mass spectrometry, are required to check the tightness of the cryogenic circuits. Extensive electrical control work, to check the integrity of the magnet instrumentation and electrical circuits throughout the assembly of the SSS, is also carried out. This paper presents the current status of production, the assembly facilities at CERN, work organisation and Quality Assurance issues, and the acquired assembly experience after one and a half years of production. | ||
| MPPT046 | Superconducting Helical Snake Magnet for the AGS | 2935 |
|
||
|
Funding: DOE A superconducting helical magnet has been built for polarized proton acceleration in the Brookhaven AGS. This "partial Snake" magnet will help to reduce the loss of polarization of the beam due to machine resonances. It is a 3 T magnet some 1940 mm in magnetic length in which the dipole field rotates with a pitch of 0.2053 degrees/mm for 1154 mm in the center and a pitch of 0.3920 degrees/mm for 393 mm in each end. The coil cross-section is made of two slotted cylinders containing superconductor. In order to minimize residual offsets and deflections of the beam on its orbit through the Snake, a careful balancing of the coil parameters was necessary. In addition to the main helical coils, a solenoid winding was built on the cold bore tube inside the main coils to compensate for the axial component of the field that is experienced by the beam when it is off-axis in this helical magnet. Also, two dipole corrector magnets were placed on the same tube with the solenoid. A low heat leak cryostat was built so that the magnet can operate in the AGS cooled by several cryocoolers. The design, construction and performance of this unique magnet will be summarized. |
||
| MPPT049 | Optimization of Open Midplane Dipole Design for LHC IR Upgrade | 3055 |
|
||
|
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-98CH10886. The proposed ten-fold increase in Large Hadron Collider (LHC) luminosity requires high field (~15 T) magnets that are subjected to the high radiation power of ~9 kW/per beam directed towards each interaction region. This has a major impact in the design of first dipole in the "Dipole First" optics. The proposed design allows sufficient clear space between coils so that most of the particle showers from the interaction points (concentrated at the midplane due to strong magnetic field) can be transported outside the coil region to a warm absorber thus drastically reducing the peak power density in the coils and removing heat at a higher (nitrogen) temperature. The concept, however, presents several new technical challenges: (a) obtaining good field quality despite a large midplane gap, (b) minimizing peak fields on coil, (c) dealing with large vertical forces with no structure between the coils, (d) minimizing heat deposition in the cold region, (e) designing a support structure. Designs with different horizontal and vertical coil spacing are presented that offer significant savings in the operating and infrastructure cost of the cryo-system, providing reliable quench-stable operation with a lifetime of the critical components of at least ten years. |
||
| MPPT050 | Test Results for LHC Insertion Region Dipole Magnets | 3106 |
|
||
|
Funding: U.S. Department of Energy. The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has made 20 insertion region dipoles for the Large Hadron Collider (LHC) at CERN. These 9.45 m-long, 8 cm aperture magnets have the same coil design as the arc dipoles now operating in the Relativistic Heavy Ion Collider (RHIC) at BNL and are of single aperture, twin aperture, and double cold mass configurations. They produce fields up to 3.8 T for operation at 7.56 TeV. Eighteen of these magnets have been tested at 4.5 K using either forced flow supercritical helium or liquid helium. The testing was especially important for the twin aperture models, which have the most challenging design. In these, the dipole fields in both apertures point in the same direction, unlike LHC arc dipoles. This paper reports on the results of these tests, including spontaneous quench performance, verification of quench protection heater operation, and magnetic field quality. Magnetic field measurements were done at 4.5K and at room temperature, and warm-cold correlations have been determined. Some dynamic measurements to study the effect of time decay and snapback at injection were also done, using a fast rotating coil. |
||
| MPPT051 | Reshimming of Tevatron Dipoles; A Process-Quality and Lessons-Learned Perspective | 3156 |
|
||
|
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-76CH03000. Over the last two years corrections have been made for the skew quadrupole moment in 530 of the 774 installed dipoles in the Tevatron. This process of modifying the magnets in situ has inherent risk of degrading the performance of the superconducting accelerator. In order to manage the risk, as well as to ensure the corrections were done consistently, formal quality tools were used to plan and verify the work. The quality tools used to define the process and for quality control are discussed, along with highlights of lessons learned. |
||
| MPPT053 | Restoring the Skew Quadrupole Moment in Tevatron Dipoles | 3244 |
|
||
|
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-76CH03000. In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 which will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets. |
||
| MPPT055 | The LANSCE Switchyard Kicker Project | 3310 |
|
||
| Until 2003, the existing configuration of the LANSCE switchyard did not allow simultaneous delivery of the H- beam to Lines D and X. In the late 1990’s, with increased activities in Areas B and C, which serve the ultracold neutron experiments (UCN) and proton radiography (PRad), respectively, planning began to increase beam availability to all areas by installing a kicker system, dubbed the "Switchyard Kicker." The Switchyard Kicker is a system of two pulsed and two direct current magnets that enables simultaneous, uninterrupted beam delivery to Line D for the Lujan Center and the Weapons Neutron Research (WNR) Facility and, on request, a tailored H- beam pulse to Line X for the pRad and UCN research areas. The project received funding in July 2001 for design and implementation. During the 2003 Extended Maintenance Period this upgrade was installed in the Switchyard and commissioned during the Accelerator Turn-On period in the summer of 2003. With the commissioning successful, LANSCE now routinely operates in "Kick" mode, delivering simultaneous beam to Line X and Line D, increasing beam availability to all areas and simplifying production scheduling. | ||
| MPPT056 | First Ideas Towards the Super-Conducting Magnet Design for the HESR at FAIR | 3354 |
|
||
| The Forschungszentrum Juelich has taken the leadership of a consortium being responsible for the design of the HESR going to be part of the FAIR project at GSI. The HESR is a 50 Tm storage ring for antiprotons, based on a super-conducting magnet technology. On basis of the RHIC Dipole D0 (3.6 T), the magnet design for the HESR has started recently. One key issue will be a very compact layout because of the rather short magnets (been 1.82 m for the dipoles and 0.5 m for the other magnets). This paper will present first ideas of the magnetic and cryogenic layout, give a status report on the achievements so far and discuss the need and possible solutions for a bent magnet with a radius of curvature of 13.2 m. |