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CLIC FFD

CLIC FFD. Final Focusing Magnet Assessment. Recent History. Conventional Facility Design for NLC · Stanford Linear Accelerator Center, March 10 to 28, 2003 CARE/ELAN meeting @ CERN November 23 - 25 2005. CLIC07 Workshop, 16-18 October 2007 Stabilisation day at CERN, March 18 2008

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CLIC FFD

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  1. CLIC FFD Final Focusing Magnet Assessment

  2. Recent History • Conventional Facility Design for NLC · Stanford Linear Accelerator Center, March 10 to 28, 2003 • CARE/ELAN meeting @ CERN November 23 - 25 2005. • CLIC07 Workshop, 16-18 October 2007 • Stabilisation day at CERN, March 18 2008 • Nanobeam 2008 (Novosibirsk, 27 May 2008) • EUROTeV Scientific Workshop at Uppsala,August 2008 • CLIC08 Workshop @ CERN, 14-17 Oct. 08 • CLIC BDS WS @ CERN, Dec. 08 Detlef Swoboda @ CLIC MDI working group

  3. References • Introduction to Transfer lines and Circular Machines P.J. Bryant/CERN84-04 • Selection of Formulae and Data useful for the Design of AG Synchrotrons C. Bovet et al, CERN/MPS-SI/Int DL/70/4 • Permanent Magnet Work at Fermilab 1995 to Present, James T Volk, FNAL • A Super-Strong Permanent Magnet Quadrupole with Variable Strength, Y. Iwashita, (ICR, Kyoto U.) et al, LINAC2004 Lübeck • Vibration stabilization for a cantilever magnet prototype at the sub-nanometer scale L. Brunetti et al. ,LAPP-TECH-2008-01 • NLC Superconducting Final Focus Magnets, Brett Parker, BNL-SMD, Nov. 2002 • COMPACT SUPERCONDUCTING FINAL FOCUS MAGNET OPTIONS FOR THE ILC*, B. Parker et al, PAC 2005 • Nested SC quad proto FNAL. ILC-Americas Workshop: SLAC, October 14-16, 2004. • Estimating Field quality in low-B Superconducting Quadrupoles and its impact on Beam Stability, E. Todesco et al, PAC 07 proceedings 353-355. • SUPERFISH - A Computer Program, K. Halbach and R. F. Holsinger, Particle Accelerators 7 (1976) 213-222. • IP solenoid and SR studies, DALENA, Barbara, CLIC08 Workshop, CERN, 14-17 October 2008 Detlef Swoboda @ CLIC MDI working group

  4. Final Focusing f1 f2 (=L*) Use telescope optics to demagnify beam by factorM = f1/f2 typically f2= L* The final doublet FD requires magnets with very high quadrupole gradient in the range of ~250 Tesla/m  superconducting or permanent magnet technology. Detlef Swoboda @ CLIC MDI working group

  5. Global requirements magnets can be constructed, supported, and monitored so as to meet alignment tolerances Detlef Swoboda @ CLIC MDI working group

  6. CLIC FF doublet parameters Detlef Swoboda @ CLIC MDI working group

  7. STUDY OF SOME OPTIONS FOR THE CLIC FINAL FOCUSINGQUADRUPOLE CLIC Note 506 M. Aleksa, S. Russenschuck Detlef Swoboda @ CLIC MDI working group

  8. Conceptual proposal for permanent magnet • PM quadrupoles might appear as an attractive option for the FFD. A variety of materials are available (table PM mat) which can be selected for a specific application. A comprehensive overview of the state of the art can be found in [3]. Flux density gradients in the order of magnitude required for CLIC have been achieved with short samples [4]. Machining to the necessary dimensional tolerances is not a fundamental problem and the cross-sectional dimensions are basically rather modest. Intrinsic drawbacks are however given by the environment through the exposure to external magnetic field, temperature variation and ionizing radiation (PM prosCons). • The design of the magnet must in addition take the magnetization spread of +- 10 % between individual PM material bricks into account. Longitudinal variation of # % have to be expected. For anisotropic materials the orientation direction can normally be held within 3° of the nominal with no special precautions. • In practice this requires an iterative adjustment of geometrical dimensions, selection of components and shimming. For quadrupoles a precise balancing between opposite poles is one of the difficult requirements. Since this tuning is exposed to environmental and operational changes, a recalibration, if necessary, would imply a full reconstruction and recommissioning of the magnet. Detlef Swoboda @ CLIC MDI working group

  9. Design issues for permanent magnets • Orientation direction (and tolerance of orientation direction is critical) • Anisotropic magnets must be magnetized parallel to the direction of orientation to achieve optimum magnetic properties. • Supply of components (bricks) magnetized or magnetization of assembled magnet • Coating requirements • Acceptance tests or performance requirements • Not advisable to use any permanent magnet material as a structural component of an assembly. • Square holes (even with large radii), and very small holes are difficult to machine. • Magnets are machined by grinding, which may considerably affect the magnet cost. • Magnets may be ground to virtually any specified tolerance. Detlef Swoboda @ CLIC MDI working group

  10. PM materials • Strontium Ferrite may be considered for the following features: • Cost, ease of fabrication, radiation hardness and stability over temperature and time. Drawback is certainly the reversible temperature coefficient of the residual field Br of -0.19%/°C. However, adding compensation shims allows to minimize the effect. This method requires a number of modify, measure, correct cycles. • Samarium cobalt is roughly 30 times more expensive and has suspect radiation resistance [4]. • Alnico is approximately 10 times more expensive and due to lower coercivity, an Alnico design will result in a tall, bulky magnet. • Barium Ferrite is a largely obsolete material with no advantages over Strontium Ferrite and should not be seriously considered. Detlef Swoboda @ CLIC MDI working group

  11. PM Materials & Features Detlef Swoboda @ CLIC MDI working group

  12. Permanent Quad Concepts • A new style of permanent magnet multipole has been described. • achieve linear strength and centerline tuning at the micron level by radially retracting the appropriate magnet(s). • Magnet position accuracies are modest and should be easily achievable with standard linear encoders Rotatable PM (Nd-Fe-B) Block to Adjust Field (+/- 10%) PM (Strontium Ferrite) Section Steel Pole Pieces (Flux Return Steel Not Shown) Detlef Swoboda @ CLIC MDI working group

  13. Double Ring Structure –Adjustable PMQ- • High gradient  heat load The double ring structure PMQ is split into inner ring and outer ring. Only the outer ring is rotated 90around the beam axis to vary the focal strength. Detlef Swoboda @ CLIC MDI working group

  14. The first prototype of “superstrong” Permanent Magnet Quad. Cut plane view Soft iron PM Axial view PHOTO Integrated strength GL=28.5T (29.7T by calc.) magnet size. f10cm Bore f1.4cm Field gradient is about 300T/m Detlef Swoboda @ CLIC MDI working group

  15. Magnetic Center Shift Detlef Swoboda @ CLIC MDI working group

  16. Conceptual proposal for SC magnet • Design and construction of SC low-B quadrupoles for particle accelerators can rely on widespread and large experience. The demanding tolerances for CLIC however are several magnitudes above already achieved performances. Whereas the field quality (multipole, homogeneity) might be manageable [9], stability issues (electrical, vibrations, temperature) are major issues. • Contrary to PM magnets tuning for different beam energies and compensation of external magnetic fields is possible but might require correction coils and consequently increase the complexity and cross-section. The required high field strength would however be rather demanding for the mechanical design and will also have an impact on the cross-section of the magnet. In addition the magnet aperture is determined by the space requirements for the inner bore of the cryostat and therefore obviously larger than in the case of a PM design. • In the framework of the GDE (global design effort) SC magnet concepts have been proposed and prototype work is in progress [7]. • By applying a serpentine winding technique the diameter for the cryostat of a prototype quadrupole could be reduced to the order of magnitude necessary for an equivalent PM [8]. Detlef Swoboda @ CLIC MDI working group

  17. SC back leg coil SC Magnet Features Coil dominated Detlef Swoboda @ CLIC MDI working group

  18. IP Magnet Development • ILC – Americas WS (14- 16 Oct. 2004 @ SLAC) • For Energy and Optics Tuning  adjustable magnet is desirable. • SC Quadrupole concept similar to HERA II meets basic requirements. • Not enough knowledge about stabilization on nm level. • Realistic Prototype required BUT cooling concept needs to be defined; i.e. (4.5 degK sub-cooled, 2 degKsuperfluid, conduction cooled, …) Detlef Swoboda @ CLIC MDI working group

  19. Detlef Swoboda @ CLIC MDI working group

  20. Measurements • Center Stability • Strength • Multipolar contents • Repeatability in Tuning • Radiation Hardness • Vibration • Geometry Detlef Swoboda @ CLIC MDI working group

  21. Conclusions • It is obvious, that substantial studies and prototyping will be necessary for both technologies in order to be able to make a firm statement about feasibility and cost. • Considerable work on SC magnets can be – and has been –done on existing magnets for evaluating vibration, repeatability and related issues. • PM magnets of large size which could be used for similar studies are not known. • A possible strategy could therefore consist in continuing work on existing SC magnets for early detection of major problems. • In parallel would be interesting of joining ongoing or starting development projects for SC and PM quadrupole magnets in the field of FELs etc. Detlef Swoboda @ CLIC MDI working group

  22. Summary (1) • Vibration & stabilization • Several studies and R&D • Passive damping & active compensation (table) • Modeling & active compensation (cantilever support) • Commercial equipment for controlled environment like IC production in accelerator noise > 10 x. • Suspension vs. support? • FF Quad magnet technology • High gradient ( N x 100 T/m) requires permanent/SC technology • Combination of both types? Detlef Swoboda @ CLIC MDI working group

  23. Summary (2) • IP layout • Push-pull vs. 2nd IP? • Need to define strategy, resources, timescale. Detlef Swoboda @ CLIC MDI working group

  24. Scope of FFS CLIC Linear Collider (~2019): Detector Interaction point 2m50 Final doublets in cantilever Vertical beam size at the interaction point: 1nm Tolerance of vertical relative positioning between the two beams to ensure the collision with only 2% of luminosity loss: 1/10nm Below 5Hz: Beam position control with deflector magnets efficient Above 5Hz: Need to control relative motion between final doublets Detlef Swoboda @ CLIC MDI working group

  25. FD stability Things we don’t know: What is the FD configuration? Saclay? Is it normal or superconducting? (M.Aleksa’s work: Sm2Co17) How close to detector? MDI issues=> free-fixed or fixed-fixed configuration? Simulations for different configurations: Free, free-fixed… 1 support, multi-support… Detlef Swoboda @ CLIC MDI working group

  26. FFD Support & Tuning • The FFD is subject to several severe constraints. One being the high beta function values required to satisfy the beam height of 1 nm specified at the CLIC interaction point. The resulting high gradient of the beta function makes it extremely difficult to obtain mechanical and magnetic tolerances over the length of more than 3 m for the quadrupole magnet. If permanent magnets are used a possible concept is the subdivision into a number of short sections which can independently be aligned and tuned (Figure 2).  • A stabilization study [5] used piezo electric elements to achieve an active alignment control in the nanometer range. This technology can be applied to an arrangement as shown in figure 2. It is suggested to insert piezo elements in the upper and lower support. This will allow to obtain vertical alignment as well as rotation around the magnet axis for each magnet element separately. • The decreasing values of the beta function close to the IP lead also to a relaxation of the alignment tolerances for the magnet sections close to the IP. • Another possibility would be a tuning by moving sections axially with respect to the IP. Detlef Swoboda @ CLIC MDI working group

  27. FF doublet (NLC ZDR) Detlef Swoboda @ CLIC MDI working group

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