Quench protection of the Fermilab-built LHC inner triplet quadrupole MQXB

High-gradient quadrupoles (MQXB) are being developed at Fermilab within the framework of the US-LHC Accelerator project for the LHC interaction regions. These 5.5-m-long magnets have a single 70-mm aperture and operate in superfluid helium at a peak gradient of 215 T/m. Magnet quench protection is provided by quench heaters installed on the outer surface of the coil. This paper reports the results of quench protection studies on the first full length MQXB prototype (MQXP01). The measurements from these tests as well as results from the 1.9-m-long model magnet program are combined with computer generated quench simulations to predict the MQXB performance under LHC operating conditions.     

Field quality in Fermilab-built models of high gradient quadrupolemagnets for the LHC interaction regions

Superconducting quadrupole magnets for the interaction regions of the Large Hadron Collider are being developed by the US-LHC Accelerator Project. These 70 mm bore quadrupole magnets are intended to operate in superfluid helium at 1.9 K with a nominal field gradient of 215 T/m. A series of 2 m model magnets are being built and tested at Fermilab to optimize design and construction parameters. Measurements of the field quality of the model magnets tested to date and comparisons with the required field quality are reported in this paper     

Test results from the LQXB quadrupole production program at Fermilab for the LHC interaction regions

As part of the US-LHC Accelerator Project, Fermilab is producing fully cryostated assemblies that will be installed as the Q1, Q2 and Q3 optical elements for the LHC Inner Triplets. The main quadrupole magnets in the Q1 (LQXA) and Q3 (LQXC) assemblies are MQXA elements designed and fabricated by KEK and Toshiba, while those in the Q2 (LQXB) assemblies are MQXB quadrupoles designed and fabricated by Fermilab. The cryostat assemblies for all magnets are designed by Fermilab, and final assembly of the optical elements occurs at Fermilab. This paper describes the production test results for the second LQXB cryostat assembly.     

LHC interaction region quadrupole cryostat production, alignment, and performance summary

The cryostat of a large hadron collider (LHC) interaction region (IR) quadrupole magnet consists of all components of the inner triplet except the magnet assembly itself. It serves to support the magnet accurately and reliably within the vacuum vessel, to provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. The major components of the cryostat are the vacuum vessel, thermal shield, multi-layer insulation system, cryogenic piping, interconnections, and suspension system. While responsibility for the design and manufacture of the main quadrupole elements is divided between Fermilab and KEK, Fermilab alone is responsible for the design and final assembly of the cryostat for the LHC inner triplets. This paper describes the experience gained during fabrication of the first complete Q2 magnets, the alignment operation and results, and the cryogenic performance of the magnet on the test stand at Fermilab.     

Quench performance and field quality of the LHC preseries superconducting dipoles

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.     

Analysis of mechanical tolerances of a low-β quadrupole magnetfor the LHC

The development of high-gradient superconducting quadrupole magnets for the LHC interaction regions has been carried out. The mechanical design has been optimized with the two-shell coil structure tightly fixed by thin non-magnetic collars and by iron-yoke with keys. The mechanical rigidity is fully achieved at room temperature. The paper describes the mechanical design characteristics and analysis of mechanical tolerances and the influence on the field quality     

Field alignment of quadrupole magnets for the LHC interactionregions

High-gradient superconducting quadrupole magnets are being developed by the US LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Determination of the magnetic axis for alignment of these magnets will be performed using a single stretched wire system. These measurements will be done both at room and cryogenic temperatures with very long wire lengths, up to 20 m. This paper reports on the stretched wire alignment methodology to be employed: and the results of recent room-temperature measurements on a 2 m model magnet with long wire lengths     

Correction of high gradient quadrupole harmonics with magneticshims

Superconducting quadrupole magnets with 70 mm aperture and nominal field gradient of 215 T/m are being developed by the US-LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Due to large beam size and orbit displacement in the final focusing triplet, these magnets are subject to stringent field quality requirements. For this reason, a correction scheme based on design calculations, fabrication issues and tests results involving magnetic shims     

Quenching behaviour of quadrupole model magnets for the LHC innertriplets at Fermilab

The US-LHC Accelerator Project is responsible for the design and production of inner triplet high gradient quadrupoles for installation in the LHC Interaction Region. The quadrupoles are required to deliver a nominal field gradient of 215 T/m in a 70 mm bore, and operate in superfluid helium. As part of the magnet development program, a series of 2 m model magnets have been built and tested at Fermilab, with each magnet being tested over several thermal cycles. This paper summarizes the quench performance and analysis of the model magnets tested, including quench training, and the ramp rate and temperature of the magnet quench current     

Principles developed for the construction of the high performance, low-cost superconducting LHC corrector magnets

The Large Hadron Collider (LHC) needs more than 6000 superconducting corrector magnets. These must be sufficiently powerful, have enough margin, be compact and of low cost. The development of the 11 types of magnets was spread over several years and included the magnetic and mechanical design as well as prototype building and testing. It gradually led to the systematic application of a number of interesting construction principles that allow to realize the above mentioned goals. The paper describes the techniques developed and presently used in practically all the LHC corrector magnets ranging from dipoles to dodecapoles.     

Development of superconducting tuning quadrupole corrector (MQT) prototypes for the LHC

The main quadrupoles of the Large Hadron Collider (LHC) are connected in families of focusing and defocusing magnets. In order to make tuning corrections in the machine a number of quadrupole corrector magnets (designated MQT) are necessary. These 56 mm diameter aperture magnets have to be compact, with a maximum length of 395 mm and a coil radial thickness of 5 to 7.5 mm, while generating a minimum field gradient of 110 T/m. Two design options have been explored, both using the "counter-winding" system developed at CERN for the fabrication of low cost corrector coils. The first design, with the poles composed of two double-pancake coils, each counter-wound using a single wire, superposed to create 4-layer coils, was developed and built by ACCEL Instruments GmbH. A second design where single coils were counter-wound using a 3-wire ribbon to obtain 6-layer coils was developed at CERN. This paper describes the two designs and reports on the performance of the prototypes during testing.     

Magnetic field characteristics of the low-beta quadrupole magnets, MQXA, for LHC

As a part of the collaboration program between CERN and KEK for the LHC, KEK has developed a superconducting low-beta quadrupole magnet, MQXA. KEK will supply 18 MQXA magnets, and 16 magnets will be installed in total in the four interaction regions. The cold tests of 13 magnets have been completed. Systematic field measurements were performed on these magnets, and these 13 magnets had satisfactory field quality for the requirement of beam optics. This paper describes the magnetic field behavior of the 13 MQXA magnets from the viewpoint of accelerator operation.     

Construction and measurement of the pre-series twin aperture resistive quadrupole magnet for the LHC beam cleaning insertions

CERN's Large Hadron Collider (LHC) requires 48 twin aperture resistive quadrupoles in the beam cleaning insertions. Canada is contributing these magnets to CERN in the framework of the TRIUMF-LHC collaboration contracts. A pre-series magnet was produced by Canadian industry and delivered in March 2001. This magnet incorporates important design changes that resulted from experience with a prototype magnet. The construction of this pre-series magnet and the measurements made at ALSTOM and at CERN are reported. A comparison is made between high precision pole distance measurements and the magnetic measurements performed with a rotating coil mole. Conclusions for series production and possibilities for multipole corrections are outlined.     

Design and fabrication of a 1 m model of the 70 mm bore twinaperture superconducting quadrupole for the LHC insertions

For reasons of geometrical acceptance, 70 mm bore twin aperture quadrupoles are required in the LHC insertions. For an operating gradient of 160 T/m at 4.5 K, a design based on a four layer coil wound from two graded 8.2 mm NbTi conductors has been developed. Three 1 m single aperture quadrupoles of this design have been built and successfully tested. Thereafter, the magnets have been disassembled and the coils re-collared using self-supporting collars. In this paper, we describe the design features of the twin aperture quadrupole, and report on the initial collaring tests and procedures for collaring and final assembly of the 1 m magnet     

Influence of mechanical tolerances on field quality in the LHC maindipoles

We evaluate the influence of mechanical tolerances in the field quality in the LHC dipoles. We show that the most relevant effect is due to tolerances on the coil and on the internal part of the collars. The sensitivities of the field error multipoles on the mechanical tolerances are worked out using a finite element model of the dipole cross section. A Monte Carlo method is used to simulate the overall effect of both collar and coil tolerances on field quality. Correlation between random multipoles is worked out, and a comparison with the target table of the LHC field errors is given     

Experimental characterization of the mechanical behavior of two solder alloys for high temperature power electronics applications

An experimental investigation of two potential candidate materials for the diamond die attachment is presented in this framework. These efforts are motivated by the need of developing a power electronic packaging for the diamond chip. The performance of the designed packaging relies particularly on the specific choice of the solder alloys for the die/substrate junction. To implement a high temperature junction, AuGe and AlSi eutectic alloys were chosen as die attachment and characterized experimentally. The choice of the AlSi alloy is motivated by its high melting temperature T_m (577 °C), its practical elaboration process and the restrictions of hazardous substances (RoHS) inter alia. The AuGe eutectic solder alloy has a melting temperature (356 °C) and it is investigated here for comparison purposes with AlSi. The paper presents experimental results such as SEM observations of failure facies which are obtained from mechanical shear as well as cyclic nano-indentation results for the mechanical hardening/softening evaluation under cyclic loading paths.     

Platform level support for high throughput edge applications: the Twin Cities prototype

Even in the face of increasing network bandwidth, there is a desire among service providers to improve network security, availability, and performance. These improvements require increasingly complex computations on network packets. Current networking platforms cannot keep up, leading to less than desired throughput or functionality. Network processors deliver high networking throughput, but not the complex processing capabilities required. High-performance general-purpose processors deliver the complex processing needed, but not the network throughput. Combination platforms that include high-performance general-purpose CPUs and network processors hold the promise of greatly increasing platform performance, enabling desired edge application improvements. This article presents Twin Cities, a heterogeneous multiprocessor research platform we have constructed from a standard IXP1240 platform, a high-volume Intel/spl reg/ Pentium/spl reg/ III processor platform, and custom hardware. This platform provides a high-performance path (high throughput, low latency) between the two processors and presents a shared memory model to the programmer. We motivate and describe the Twin Cities platform, discuss the applications it targets, and present performance measurements.     

Design and performance of a product code turbo encoding-decoding prototype

This paper presents the latest results on a block turbo decoder design. We propose a block turbo decoder circuit for the error protection of small data blocks such asAtm cells on anAwgn (additive white Gaussian noise) channel with a code rate close to 0.5. A prototype was developed atEnst Bretagne. It allowsBer (bit error rate) measurements down to 10^?9 and uses programmable gate arrays (Fpga Xilinx circuits). The elementary extendedBch code and the data block size can be modified to fit specifications of different applications.