Artwork: A. Duncan Compact and Low Consumption Magnet Design for Future Linear and Circular Colliders CERN, November 2014

Talk Outline Introduction – CLIC quadrupole requirements Permanent Magnet Quadrupole prototypes –ZEPTO-Q1: high strength –ZEPTO-Q2: low strength Permanent Magnet Dipole design –ZEPTO-D1 Overview ●◉ Introduction ○○○○○○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

The CLIC Drive Beam The drive beam decelerates from 2.4 GeV to 0.24 GeV transferring energy to the main beam As the electrons decelerate, quadrupoles are needed every 1m to keep the beam focused The quadrupole strengths scale with the beam energy The CLIC accelerator length is ~42km so there are ~42,000 quadrupoles needed Overview ●● Introduction ◉○○○○○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Quadrupole Tunability The nominal maximum integrated gradient is 12.2T and the minimum is 1.22T For operational flexibility each individual quadrupole must operate over a wide tuning range –70% to 120% at high energy (2.4 GeV) –7% to 40% at low energy (0.24 GeV) 12.2 T 1.22 T Overview ●● Introduction ●◉○○○○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Quadrupole Specification ParameterHigh-energy endLow-energy endUnits Number of quadrupoles41400 Strength T Stability5x10 -4 Integrated gradient quality0.1% Good field region11.5mm Minimum bore radius13mm Maximum width390mm Maximum height390mm Maximum length270mm Overview ●● Introduction ●●◉○○○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Permanent Magnet Option The integrated magnet strength requirement is very challenging (given the space constraints) for a conventional electromagnet The nominal power consumption for the EM version will be ~8 MW in nominal mode and up to ~17 MW in tune-up mode Total Power Load limit to air within the tunnel is only 150 W/m (all components) A PM quad would potentially have many advantages –Vastly reduced electrical power –Very low operating costs –No cooling water needs –Very low power to air We have been investigating the PM option for the drive beam CERN-STFC collaboration: ZEPTO – Zero-Power Tunable Optics Overview ●● Introduction ●●●◉○○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Permanent Magnet Challenges There are many existing PM quadrupole examples The combination of high strength, large tunability, high field quality, and restricted volume meant that a new design was required Additional challenges for PM include possible radiation damage, field variation with temperature, PM strength variation from block to block (material and engineering tolerances) The complete tuning range (120% to 7%) could not be met by a single design We have broken the problem down into two magnet designs – one high energy and one low energy Overview ●● Introduction ●●●●◉○ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Quadrupole Types High energy quad – Gradient very high Low energy quad – Very large tuning range Erik Adli & Daniel Siemaszko Low Energy Quad High Energy Quad Overview ●● Introduction ●●●●●◉ Q1 ○○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

NdFeB magnets with B r = 1.37 T (VACODYM 764 TP) 4 permanent magnet blocks each 18 x 100 x 230 mm Mounted at optimum angle of 40° Max gradient = 60.4 T/m (stroke = 0 mm) Min gradient = 15.0 T/m (stroke = 64 mm) Pole gap = 27.2 mm Field quality = ±0.1% over 23 mm Stroke = 64 mm Poles are permanently fixed in place High Energy Quad Design Stroke = 0 mm Overview ●● Introduction ●●●●●● Q1 ◉○○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

High Energy Quad Animation Overview ●● Introduction ●●●●●● Q1 ●◉○○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Engineering of High Energy Quad Single axis motion with one motor and two ballscrews Rotary encoder on motor (linear encoders used during setup to check repeatability) Maximum force is 16.4 kN per side, reduces by x10 when stroke = 64 mm PM blocks bonded to steel bridge piece and protective steel plate also bonded Steel straps added as extra security Overview ●● Introduction ●●●●●● Q1 ●●◉○○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Assembled Prototype Overview ●● Introduction ●●●●●● Q1 ●●●◉○○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Measured Integrated Gradient Overview ●● Introduction ●●●●●● Q1 ●●●●◉○ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Magnet Centre Movement The magnet centre moves upwards by ~100 µm as the permanent magnets are moved away 3D modelling suggests this is due to the rails being ferromagnetic (µ r ~ 100, measured) and not mounted symmetrically about the midplane – should be easy to fix Motor/gearbox assembly may also be a contributing factor Overview ●● Introduction ●●●●●● Q1 ●●●●●◉ Q2 ○○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Low Energy Quad Design Lower strength easier but requires much larger tunability range (x12) Outer shell short circuits magnetic flux to reduce quad strength rapidly NdFeB magnets with B r = 1.37 T (VACODYM 764 TP) 2 permanent magnet blocks are 37.2 x 70 x 190 mm Max gradient = 43.4 T/m (stroke = 0 mm) Min gradient = 3.5 T/m (stroke = 75 mm) Pole gap = 27.6 mm Field quality = ±0.1% over 23 mm Stroke = 0 mm Stroke = 75 mm Poles and outer shell are permanently fixed in place. Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ◉○○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Low Energy Quad Animation Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●◉○○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Engineering of Low Energy Quad Simplified single axis motion with one motor and one ballscrew Rotary encoder on motor – linear encoders used during setup to check repeatability Maximum force is only 0.7 kN per side PM blocks bonded within aluminium support frame Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●◉○○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Assembled at Daresbury during 2013 Careful attention paid to pole positions Measurements –Early 2014: Hall probe at Daresbury –Late 2014: stretched wire, rotating coil at CERN Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●◉○○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Measured Integrated Gradient Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●◉○ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014 Higher than expected tuning range! Maximum gradient: 45.0 T/m Minimum gradient: 3.6 T/m

Measured Axis Movement Good agreement between measurement methods –stretched wire –rotating coil X axis moves in one direction –Possible misalignment of outer shell? Y axis moves up and then back down –Harder to explain this… X (horiz) Y (vert) Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●◉ D1 ○○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

PM dipoles: ZEPTO-D1 New STFC-CERN work package: investigate PM dipoles –Drive Beam Turn Around Loop (DB TAL) –Main Beam Ring to Main Linac (MB RTML) Total power consumed by both types: 15 MW Reduced-length DB TAL prototype to be constructed by Dec 2015 Several possible designs currently on the table TypeQuantityLength (m) Strength (T) Pole Gap (mm) Good Field Region (mm) Field Quality Range (%) MB RTML x 201 x ± 10 DB TAL x 401 x –100 Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ◉○○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Design Concept #1 Design used for a prototype at SPring-8* Steel top plate moves down to shunt flux from PMs and decrease field Tuning range: T *IPAC 2014 TUPRO092, Watanabe et al 160mm max 1.8T max 2.1T 5mm Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●◉○○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Design Concept #2 Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●●◉○ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014 Moving section in backleg – flux shunted between poles Tuning range: T

Design Concept #3 (Neil Marks) Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●●●◉ Summary ○○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014 Rotating cylinder in backleg (steel and PM) Rotate by 180° to get full range Tuning range: T Field quality (2D): 1.2x10 -4 Modelled as H-magnet (left) or C-magnet (right)

Summary PM driven quads have many advantages in terms of operating costs, infrastructure requirements, and power load in the tunnel We have shown that only two PM designs are required to cover the entire range of gradients required for the CLIC Drive Beam Two prototypes have been built and measured, demonstrating the required gradient range The magnetic centre moves vertically as the gradient is adjusted –We think we understand the reasons for this Modelling of dipole concepts for the DB-TAL is in progress Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●●●● Summary ◉○○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Acknowledgments Daresbury Laboratory team –Magnet design: Ben Shepherd, Jim Clarke, Neil Marks –Mechanical design: Norbert Collomb, James Richmond, Graham Stokes CERN team –Project lead: Michele Modena –Magnet measurements: Antonio Bartalesi, Mike Struik, Marco Buzio, Samira Kasaei, Carlo Petrone –Also starring: Alexandre Samochkine, Dmitry Gudkov, Evgeny Solodko, Alexander Aloev, Alexey Vorozhtsov, Guido Sterbini Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●●●● Summary ●◉○○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

References 1.Aicheler et al, Eds., A Multi-TeV linear collider based on CLIC technology: CLIC Conceptual Design Report. CERN, 2012.CLIC Conceptual Design Report 2.Volk et al, “Adjustable permanent quadrupoles for the Next Linear Collider,” PACS2001 Proc PAC Cat No01CH37268, vol. 1, 2002.Adjustable permanent quadrupoles for the Next Linear Collider 3.Tommasini et al, “Design, Manufacture and Measurements of Permanent Quadrupole Magnets for Linac4,” IEEE Trans. Appl. Supercond., vol. 22, no. 3, pp – , Jun Design, Manufacture and Measurements of Permanent Quadrupole Magnets for Linac4 4.Plostinar et al, “A hybrid quadrupole design for the RAL Front End Test Stand (FETS),” in Proc. of EPAC, 2008, vol. 8.A hybrid quadrupole design for the RAL Front End Test Stand (FETS) 5.Lim et al, “Adjustable, short focal length permanent-magnet quadrupole based electron beam final focus system,” Phys. Rev. Spec. Top. - Accel. Beams, vol. 8, no. 7, p , Jul Adjustable, short focal length permanent-magnet quadrupole based electron beam final focus system 6.Mihara et al, “Variable Permanent Magnet Quadrupole,” IEEE Trans. Appl. Supercond., vol. 16, 2006.Variable Permanent Magnet Quadrupole 7.Iwashita et al, “Permanent Magnet Final Focus Doublet R&D for ILC at ATF2,” PAC 2009 MO6PFP024.Permanent Magnet Final Focus Doublet R&D for ILC at ATF2 8.S. C. Gottschalk et al, “Performance of an Adjustable Strength Permanent Magnet Quadrupole,” PAC 2005.Performance of an Adjustable Strength Permanent Magnet Quadrupole 9.Clarke et al, “Novel Tunable Permanent Magnet Quadrupoles for the CLIC Drive Beam,” IEEE Trans. Appl. Supercond., vol. 24, no. 3, pp. 1–5, Jun Novel Tunable Permanent Magnet Quadrupoles for the CLIC Drive Beam 10.Shepherd, Collomb, and Clarke, “Permanent magnet quadrupoles for the CLIC Drive Beam decelerator,” CLIC-Note- 940, 2012.Permanent magnet quadrupoles for the CLIC Drive Beam decelerator 11.Bartalesi, Modena, and Struik, “Results of the first measuring campaign of the Daresbury Permanent Magnet High Gradient Quadrupole Prototype for the CLIC Drive Beam,” TE-MSC Internal Note , 2013.Results of the first measuring campaign of the Daresbury Permanent Magnet High Gradient Quadrupole Prototype for the CLIC Drive Beam 12.Shepherd et al, “Prototype Adjustable Permanent Magnet Quadrupoles For CLIC,” IPAC 2013 THMPE043.Prototype Adjustable Permanent Magnet Quadrupoles For CLIC 13.Shepherd et al, “Design And Measurement Of A Low-Energy Tunable Permanent Magnet Quadrupole Prototype,” IPAC 2014 TUPRO113.Design And Measurement Of A Low-Energy Tunable Permanent Magnet Quadrupole Prototype 14.Shepherd et al, "Tunable high-gradient permanent magnet quadrupoles," 2014 JINST 9 T11006 doi: / /9/11/T11006.Tunable high-gradient permanent magnet quadrupolesdoi: / /9/11/T11006 Overview ●● Introduction ●●●●●● Q1 ●●●●●● Q2 ●●●●●● D1 ●●●● Summary ●●◉○ Ben Shepherd — Compact & Low Consumption Magnet Design Workshop — CERN, Nov 2014

Artwork: P. Tenconi