— Magnetic cable project will extend the reach of CERN high energy physics collider
By Ian Pong and Joe Chew
Berkeley Lab has passed the halfway mark in the multi-year process of fabricating crucial superconducting cables as part of a project to upgrade the Large Hadron Collider (LHC) at CERN. This upgrade, now in progress, will greatly increase the collision rate and thus the scientific productivity of the facility. The High Luminosity-LHC Accelerator Upgrade Project, or HL-LHC AUP, is the multi-institutional, Fermilab-headquartered U.S. contribution to this upgrade. A group of much-stronger focusing magnets, known as the “inner triplet,” will be installed on either side of the interaction points where the otherwise separate proton beams collide. By squeezing the beams to higher density at the interaction points, these stronger focusing magnets will play a major role in increasing the number of collisions over the lifetime of the machine (“integrated luminosity”) by a factor of 10. This will significantly improve the opportunities for discovering new physics.
The coils for the HL-LHC AUP focusing magnets are made from advanced niobium-tin (Nb3Sn) superconductor in a copper matrix. One of Berkeley Lab’s key contributions is fabricating all the cables to be used in these AUP focusing quadrupoles. The task reached the halfway mark in January 2021.
Left: Ian Pong, Berkeley Lab cabling manager for the HL-LHC AUP, works with the machine that forms numerous strands of superconducting wire into “Rutherford-style” cables. Cabling is crucial to magnet performance and a longtime strength of Berkeley Lab’s superconducting magnet program. The unique and versatile cabling machine was first developed for the Superconducting Super Collider project and since updated with many state of-the-art quality assurance features designed to address DOE 413.3b project needs. Right: A detail of the part of the cabling machine, strands of superconducting wire enter the rollers of the cabling machine where strands of superconducting wire are shaped and formed into keystoned “Rutherford style” cable. [Marilyn Sargent/Berkeley Lab]
Fermilab’s Giorgio Apollinari, AUP Project Manager, said of the milestone, “This is a great “turning-of-the-buoy” achievement since it allows the Project to continue unimpeded in the production of these critical HL-LHC AUP magnets.”
Berkeley Lab Project Lead and Berkeley Center for Magnet Technology (BCMT) Director Soren Prestemon added, “This halfway mark is a tremendous milestone for our cabling team, who have delivered exceptionally for the project — even more remarkable given the complexities of on-site work under COVID constraints.”
The overall AUP was recently granted Critical Decision 3 (CD-3) approval in the Department of Energy’s project-management process, giving the go-ahead for series production of the magnets themselves. Cable fabrication had already begun under a management approach in which long-lead-time items, such as wire procurement and cable fabrication, received approvals to go ahead before the series production of the magnets themselves.
“The AUP project leverages extensive expertise and capabilities in advanced Nb3Sn magnet technology at Berkeley Lab,” said Cameron Geddes, Director of the Accelerator Technology and Applied Physics (ATAP) Division. ATAP and the Engineering Division formed the BCMT to join forces in advanced magnet design. Geddes added, “This critical milestone demonstrates the Lab’s commitment to the project and the team’s unique ability to deliver on its challenging requirements.”
From Conductor to Cable to Magnet
Cables and Magnets By The Numbers
Four magnets are needed on either side of each of the two major LHC detectors — ATLAS and CMS — to focus the proton beams. In addition to these 16 magnets, four spares will also be made, bringing the total to 20 magnets.
Each magnet contains four coils, and each coil is made from one continuous cable. Each cable needs 40 strands at 500 m each — that is 20 km of superconducting wire per cable, weighing about 100 kg.
It takes over 60 days to fully complete a cable fabrication process, which includes a high temperature reaction heat treatment and cryogenic temperature measurement of strand samples extracted from the cable. As many as ten cables can be in process at the various manufacturing and testing stages at any one time.
The project needs 80 cables and because the coil manufacturing process is challenging the production yield is a significant driver of project cost. The coil yield assumption was 85%, meaning that to produce the requisite 80 good coils, 94 coils will need to be produced and correspondingly 94 qualified cables are needed. Similarly, the yield assumption for cable fabrication is 90%, based on past experience. Thus, 104 cable manufacturing runs are planned in order to ensure 94 qualified cables can be delivered. To date, the cabling yield has been higher than assumed, standing at about 96% — a potential saving of millions of dollars.
Most people have seen or even built electromagnets made from coils of individual wire, a familiar item at school science fairs and in consumer products. However, there are geometric, thermo-mechanical, and electromagnetic reasons why these would not work well in accelerator magnets. Instead, accelerators use cables formed from multiple strands of superconducting wire. The cables are flat, with a rectangular or very slightly trapezoidal “keystoned” cross section, a profile known as “Rutherford style” after the Rutherford Appleton Laboratory in England, which developed the design.
Rutherford cables are flexible when bent on their broad face, which makes coil winding easy. However, the strands at the thin edges of the cable are heavily deformed and their thermoelectric stability (as reflected by the quality parameter “residual resistance ratio” or RRR) could be degraded, so the shaping must be carefully monitored and controlled.
The overall AUP team is supported by the DOE Office of Science and consists of six U.S. laboratories and two universities: Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, and Thomas Jefferson National Accelerator Facility (all DOE national laboratories), along with the National High Magnetic Field Laboratory, Old Dominion University, and the Florida State University. Each brings unique strengths to the challenges of designing, building, and testing these advanced magnets and their components. Industrial partners supply the superconducting wire.
Dan Cheng
Berkeley Lab ships the cables to Fermilab or Brookhaven to be fabricated into coils and reacted (heat treated) to activate their superconductivity. The reacted coils are returned to Berkeley Lab, which uses them to make the quadrupole magnets. This recent article gives an in-depth look at how multiple institutions use their complementary strengths to make magnets for the AUP.
“These magnets are a culmination of more than 15 years of technology development, starting with the LARP (LHC Accelerator Research Program) collaboration,” recounts the Engineering Division’s Dan Cheng, who is the Deputy Level-3 Control Account Manager for the Magnet Structures task at Berkeley Lab.
“Eagle eyes for quality and big collaborative hearts”
Berkeley Lab, which celebrates its 90th anniversary this year, has a strong history of national and international collaboration in building accelerators, and its superconducting-magnet expertise goes back to the early 1970s and the roots of the Experimental Superconducting Accelerator (ESCAR) project.
The planetary-motion cabling machine at Berkeley Lab was designed and installed in the early 1980s, and received continual upgrades over the years. It has contributed to large DOE projects such as the Fermilab Tevatron upgrade and the Superconducting Super Collider, and is key infrastructure for Berkeley Lab’s present superconducting-magnet activities.
The cabling facility also boasts a world-class suite of quality-assurance systems to monitor cable properties. These include an in-line cable measurement machine that can measure a cable’s dimensional parameters at a set pressure, an in-line camera system that can record every millimeter of all four sides of the fabricated cables and perform image analysis, and a specially designed cryo-cooler system for reproducibly measuring the RRR of extracted strand samples.
The people who put together and use this equipment come from the ATAP and Engineering Divisions. Ian Pong, Berkeley Lab cabling manager for the HL-LHC AUP, says, “We have not only world-class equipment for fabricating state-of-the-art superconducting cables, but most importantly a world-class team of people who have eagle eyes for quality and big collaborative hearts for projects.”
The cabling team has been led by Pong since 2014, following in the footsteps of now-retired leaders Ron Scanlan and Dan Dietderich. The cabling team members handling the AUP production over the years included former deputy leader Charlie Sanabria (now at Commonwealth Fusion Systems), incumbent deputies Elizabeth Lee and Mike Naus; former and present lead technicians Hugh Higley and Andy Lin, along with their fellow technicians Carlos Perez, Matt Kaiser, and Juan Rodriguez; and many student interns from the nearby University of California, Berkeley.
Apollinari says, “The LBNL group led by Ian has been outstanding in the high-quality production of the Nb3Sn cables, meeting not only the demanding QA/QC requirement but achieving a production yield very much above and beyond the expected yield for this kind of activities. This is obviously of great help for the AUP Project, both economically and from the schedule point of view.”
Throw your hands in the air like we’re halfway there: whether onsite or on Zoom, the Berkeley Lab HL-LHC AUP cabling team and management got together for a socially distanced celebration of the 50% milestone. Left, top to bottom: Mike Naus, Elizabeth Lee, and Thomas Schenkel. Second column from left, top to bottom: Andy Lin, Hugh Higley, Charlie Sanabria, and Cameron Geddes. Third column from left, top to bottom: Edward Stafford, Carlos Perez, Lea Rewinski (l.) and Pat Thomas (r.). Right, top to bottom: Soren Prestemon, Ian Pong, Asmita Patel (r.), Daryl Barth (l.), and Jonathan Lee. (Click for larger version)
Fermilab’s Giorgio Apollinari, AUP Project Manager, said of the milestone, “This is a great “turning-of-the-buoy” achievement since it allows the Project to continue unimpeded in the production of these critical HL-LHC AUP magnets.”
Berkeley Lab Project Lead and Berkeley Center for Magnet Technology (BCMT) Director Soren Prestemon added, “This halfway mark is a tremendous milestone for our cabling team, who have delivered exceptionally for the project — even more remarkable given the complexities of on-site work under COVID constraints.”
The overall AUP was recently granted Critical Decision 3 (CD-3) approval in the Department of Energy’s project-management process, giving the go-ahead for series production of the magnets themselves. Cable fabrication had already begun under a management approach in which long-lead-time items, such as wire procurement and cable fabrication, received approvals to go ahead before the series production of the magnets themselves.
“The AUP project leverages extensive expertise and capabilities in advanced Nb3Sn magnet technology at Berkeley Lab,” said Cameron Geddes, Director of the Accelerator Technology and Applied Physics (ATAP) Division. ATAP and the Engineering Division formed the BCMT to join forces in advanced magnet design. Geddes added, “This critical milestone demonstrates the Lab’s commitment to the project and the team’s unique ability to deliver on its challenging requirements.”
From Conductor to Cable to Magnet
Cables and Magnets By The Numbers
Four magnets are needed on either side of each of the two major LHC detectors — ATLAS and CMS — to focus the proton beams. In addition to these 16 magnets, four spares will also be made, bringing the total to 20 magnets.
Each magnet contains four coils, and each coil is made from one continuous cable. Each cable needs 40 strands at 500 m each — that is 20 km of superconducting wire per cable, weighing about 100 kg.
It takes over 60 days to fully complete a cable fabrication process, which includes a high temperature reaction heat treatment and cryogenic temperature measurement of strand samples extracted from the cable. As many as ten cables can be in process at the various manufacturing and testing stages at any one time.
The project needs 80 cables and because the coil manufacturing process is challenging the production yield is a significant driver of project cost. The coil yield assumption was 85%, meaning that to produce the requisite 80 good coils, 94 coils will need to be produced and correspondingly 94 qualified cables are needed. Similarly, the yield assumption for cable fabrication is 90%, based on past experience. Thus, 104 cable manufacturing runs are planned in order to ensure 94 qualified cables can be delivered. To date, the cabling yield has been higher than assumed, standing at about 96% — a potential saving of millions of dollars.
Most people have seen or even built electromagnets made from coils of individual wire, a familiar item at school science fairs and in consumer products. However, there are geometric, thermo-mechanical, and electromagnetic reasons why these would not work well in accelerator magnets. Instead, accelerators use cables formed from multiple strands of superconducting wire. The cables are flat, with a rectangular or very slightly trapezoidal “keystoned” cross section, a profile known as “Rutherford style” after the Rutherford Appleton Laboratory in England, which developed the design.
Rutherford cables are flexible when bent on their broad face, which makes coil winding easy. However, the strands at the thin edges of the cable are heavily deformed and their thermoelectric stability (as reflected by the quality parameter “residual resistance ratio” or RRR) could be degraded, so the shaping must be carefully monitored and controlled.
The overall AUP team is supported by the DOE Office of Science and consists of six U.S. laboratories and two universities: Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, and Thomas Jefferson National Accelerator Facility (all DOE national laboratories), along with the National High Magnetic Field Laboratory, Old Dominion University, and the Florida State University. Each brings unique strengths to the challenges of designing, building, and testing these advanced magnets and their components. Industrial partners supply the superconducting wire.
Dan Cheng
Berkeley Lab ships the cables to Fermilab or Brookhaven to be fabricated into coils and reacted (heat treated) to activate their superconductivity. The reacted coils are returned to Berkeley Lab, which uses them to make the quadrupole magnets. This recent article gives an in-depth look at how multiple institutions use their complementary strengths to make magnets for the AUP.
“These magnets are a culmination of more than 15 years of technology development, starting with the LARP (LHC Accelerator Research Program) collaboration,” recounts the Engineering Division’s Dan Cheng, who is the Deputy Level-3 Control Account Manager for the Magnet Structures task at Berkeley Lab.
“Eagle eyes for quality and big collaborative hearts”
Berkeley Lab, which celebrates its 90th anniversary this year, has a strong history of national and international collaboration in building accelerators, and its superconducting-magnet expertise goes back to the early 1970s and the roots of the Experimental Superconducting Accelerator (ESCAR) project.
The planetary-motion cabling machine at Berkeley Lab was designed and installed in the early 1980s, and received continual upgrades over the years. It has contributed to large DOE projects such as the Fermilab Tevatron upgrade and the Superconducting Super Collider, and is key infrastructure for Berkeley Lab’s present superconducting-magnet activities.
The cabling facility also boasts a world-class suite of quality-assurance systems to monitor cable properties. These include an in-line cable measurement machine that can measure a cable’s dimensional parameters at a set pressure, an in-line camera system that can record every millimeter of all four sides of the fabricated cables and perform image analysis, and a specially designed cryo-cooler system for reproducibly measuring the RRR of extracted strand samples.
The people who put together and use this equipment come from the ATAP and Engineering Divisions. Ian Pong, Berkeley Lab cabling manager for the HL-LHC AUP, says, “We have not only world-class equipment for fabricating state-of-the-art superconducting cables, but most importantly a world-class team of people who have eagle eyes for quality and big collaborative hearts for projects.”
The cabling team has been led by Pong since 2014, following in the footsteps of now-retired leaders Ron Scanlan and Dan Dietderich. The cabling team members handling the AUP production over the years included former deputy leader Charlie Sanabria (now at Commonwealth Fusion Systems), incumbent deputies Elizabeth Lee and Mike Naus; former and present lead technicians Hugh Higley and Andy Lin, along with their fellow technicians Carlos Perez, Matt Kaiser, and Juan Rodriguez; and many student interns from the nearby University of California, Berkeley.
Apollinari says, “The LBNL group led by Ian has been outstanding in the high-quality production of the Nb3Sn cables, meeting not only the demanding QA/QC requirement but achieving a production yield very much above and beyond the expected yield for this kind of activities. This is obviously of great help for the AUP Project, both economically and from the schedule point of view.”
Throw your hands in the air like we’re halfway there: whether onsite or on Zoom, the Berkeley Lab HL-LHC AUP cabling team and management got together for a socially distanced celebration of the 50% milestone. Left, top to bottom: Mike Naus, Elizabeth Lee, and Thomas Schenkel. Second column from left, top to bottom: Andy Lin, Hugh Higley, Charlie Sanabria, and Cameron Geddes. Third column from left, top to bottom: Edward Stafford, Carlos Perez, Lea Rewinski (l.) and Pat Thomas (r.). Right, top to bottom: Soren Prestemon, Ian Pong, Asmita Patel (r.), Daryl Barth (l.), and Jonathan Lee. (Click for larger version)
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