CLIC FFD Final Focusing Magnet Assessment And Proposal

CLIC FFD Final Focusing Magnet Assessment And Proposal for a short term R&D effort

Recent Events • Conventional Facility Design for NLC · Stanford Linear Accelerator Center, March 10 to 28, 2003 • CARE/ELAN meeting @ CERN November 23 - 25 2005. • CLIC 07 Workshop, 16 -18 October 2007 • Stabilisation day at CERN, March 18 2008 • Nanobeam 2008 (Novosibirsk, 27 May 2008) • EUROTe. V Scientific Workshop at Uppsala, August 2008 • CLIC 08 Workshop @ CERN, 14 -17 Oct. 08 • CLIC BDS WS @ CERN, Dec. 08 5 June. 2009 Detlef Swoboda @ CLIC

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. Introduction to Transfer lines and Circular Machines P. J. Bryant/CERN 84 -04 Selection of Formulae and Data useful for the Design of AG Synchrotrons C. Bovet et al, CERN/MPS-SI/Int DL/70/4 SUPERFISH - A Computer Program, K. Halbach and R. F. Holsinger, Particle Accelerators 7 (1976) 213 -222. Vibration stabilization for a cantilever magnet prototype at the sub-nanometer scale L. Brunetti et al. , LAPP-TECH-2008 -01 IP solenoid and SR studies, DALENA, Barbara, CLIC 08 Workshop, CERN, 14 -17 October 2008 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, LINAC 2004 Lübeck MODIFICATION AND MEASUREMENT OF THE ADJUSTABLE PERMANENT MAGNET QUADRUPOLE FOR THE FINAL FOCUS IN A LINEAR COLLIDER*, Y. Iwashita et al. , PAC 07 Permanent magnet Final Focus Quadrupole for ATF 2, Y. Iwashita et al, ATF 2 19 -21 Dec 2007 CONTINUOUSLY ADJUSTABLE PERMANENT MAGNET QUADRUPOLE FOR A FINAL FOCUS, Takanori Sugimoto, EPAC 08 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. ADJUSTABLE STRENGTH REC OUADRUPOLES, R. L. , , Gluckstern, R. F, Holsinger, IEEE Vol. NS-30, NO. 4, Aug 1983 Feasibility for Quadrupole for CLIC Final Focus, P. Sievers, 1988 Conceptual design of a 5 T/mm Quadrupole for linear collider final focus, K. Egawa, T. Taylor, CERN LEP-MA 89 -08 Crab collisions for the CLIC final focus, J. Hagel, B. Zotter, CLIC Note 210, 14 Sep. 1993 5 June. 2009 Detlef Swoboda @ CLIC

Outline • Requirements and Technology Issues • FFD Magnet Technologies – Proposals and Protos – Design Issues • Concluding Remarks 5 June. 2009 Detlef Swoboda @ CLIC

Final Focusing Requirements f 1 f 2 (=L*) Use telescope optics to demagnify beam by factor M = f 1/f 2 typically f 2= L* The final doublet FD requires magnets with very high quadrupole gradient exceeding ~250 Tesla/m magnets can be constructed, supported, and monitored to meet alignment tolerances superconducting or permanent magnet technology? 5 June. 2009 Detlef Swoboda @ CLIC

Global requirements Requirements 5 June. 2009 CLIC main parameters value Center-of-mass energy 3 Te. V Peak Luminosity 2· 10^34 cm-2 s-1 Repetition rate 50 Hz Beam pulse length 230 ns Average current in pulse 1 A Hor. /vert. IP beam size bef. pinch 53 / ~1 nm Stability ~ nm Spot size Some nm (40 x 1) Beam measurement accuracy ~1 % Q-pole strength accuracy ~ 10^-3 beam miss-match dominated by measurement errors, not by magnets Tuning accuracy QD 0 ~ 10^-6 (0. 02 G) Alignment tuning frequencies Vibration/ripple t< 1/5 s Stability/drift t < 1 hr Detlef Swoboda @ CLIC

CLIC FF doublet parameters QF 1 L* QD 0 3. 5 m Gradient 200 575 T/m Length 3. 26 2. 73 m Aperture (radius) 4. 69 3. 83 mm Outer radius < 35 - < 43 mm Octupolar error 106 T/m 3 Dodec. error 1016 T/m 5 Peak field Requirements 0. 94 2. 20 Field stability 10^-4 Energy spread ± 1 T G ~ 1/R² Bpole ~ R % IP*z = G * R^2/(2 * µº) = (575*14. 7*10^-6)/(2*4*π*10^-7)=105. 4*10^2/ π=3355 [A] – Ampere-turns/pole [Br (@ pole tip) = 2. 20 T] Doublet magnetic length: α =( h 1*l. FFD*d. BZ/dx)/B 0*ρ; l* ≈ h 1/ α l. FFD = (B 0*ρ*dx/d. BZ )/l* = (3. 3356*1. 5*10³/406. 6)/3. 5 = 3. 51 [m] 5 June. 2009 Detlef Swoboda @ CLIC

SC type Temp [K ] Bcr [T] J [A/m 2] G [T/m] Nb-Ti 1. 9 5 6*10^9 300 Nb 3 Sn 1. 9 5 1*10^10 500 5 June. 2009 Max. Gradients Requirements Detlef Swoboda @ CLIC

RT Quadrupole 2 mm 5 June. 2009 Detlef Swoboda @ CLIC Conventional Magnets

RT LHC type Quadrupole Conventional Magnets 5 June. 2009 Detlef Swoboda @ CLIC

Conventional Quadrupole Conventional Magnets RT or SC Technology 5 June. 2009 Detlef Swoboda @ CLIC

Conceptual proposal for permanent magnet Permanent Magnets • • • 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 pros. Cons). 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. 5 June. 2009 Detlef Swoboda @ CLIC

Design issues for permanent magnets Permanent Magnets The magnetic properties of PM material are altered by various external factors. These range from temperature variations over mechanical effects to ionizing radiation. • • • 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. 5 June. 2009 Detlef Swoboda @ CLIC

PM materials … • • • Permanent Magnets 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. Parameter Sr Ferrite Nd-Fe Sm-Co Br [T] 0. 385 1. 230 1. 050 Hci [Oe] 3050 12000 11000 BHmax [MGO] 3. 5 35. 0 26. 0 Temp var. [%] 0. 18 0. 11 0. 045 Cost [$/cm³] 0. 04 2. 75 3. 66 5 June. 2009 Detlef Swoboda @ CLIC

… PM materials Material Nd-Fe-B Sm-Co Alnico Permanent Magnets State Cost Bhmax Coercivity Tmax (sintered) (bonded) Hard Flexible Index 65% 50% 100% 85% 30% 5% 2% MGOe. Hci <45 <10 <30 <12 <10 <4 <2 (KOe) <30 <11 <25 <10 <2 <3 <3 (o. C) 180 150 350 150 550 300 100 Ferrite Critical Temperatures for Various Materials 5 June. 2009 Material TCurie (deg. C) Tmax (deg. C) Neodymium Iron Boron 310 150 Samarium Cobalt 750 300 Alnico 860 540 Ceramic 460 300 Detlef Swoboda @ CLIC Machinabi lity Fair Good Difficult Fair Excellent

Studies on Radiation effects for PM Permanent Magnets • Sm. Co and especially Sm 2 Co 17 withstand radiation 2 to 40 times better than Nd. Fe. B materials. • Sm. Co exhibits significant demagnetization when irradiated with a proton beam of 10 MGy to 100 MGy. • Nd. Fe. B test samples were shown to lose all of their magnetization at a dose of 7 x 100 k. Gy, and 50% at a dose of 4 x 10 k. Gy. • In general, it is recommended that magnet materials with high Hci values be used in radiation environments, that they be operated at high permeance coefficients, Pc, and that they be shielded from direct heavy particle irradiation. Stabilization can be achieved by pre-exposure to expected radiation levels. 5 June. 2009 Detlef Swoboda @ CLIC

Reluctance Permanent Magnets • Reluctance changes occur when a magnet is subjected to permeance changes such as changes in air gap dimensions during operation. These changes will change the reluctance of the circuit, and may cause the magnet's operating point to fall below the knee of the curve, causing partial and/or irreversible losses. The extents of these losses depend upon the material properties and the extent of the permeance change. Stabilization may be achieved by pre-exposure of the magnet to the expected reluctance changes. 5 June. 2009 Detlef Swoboda @ CLIC

PM Materials & Features Permanent Magnets Material samarium cobalt (Sm 2 Co 17) Smx. Erl-x. Co neodymium iron boron (Nd. Fe. B) Strontium Ferrite (Sr. Fe ) Barium Ferrite (Ba. Fe ) Fe. Cr. Co Alnico Pros No pwr cables No cryo No vibration High coercivity 5 June. 2009 Characteristics Brittle anisotropic corrosion resistant, no coating required Stability ~ 10 -6/hr Rather brittle, mostly anisotropic susceptible to corrosion, requires coating can lose strength under irradiation ultrahigh coercivity grades show very small remanence losses, <0. 4%± 0. 1%, for absorbed doses up to 3 Mgy from 17 Me. V electrons irradiation by 200 Me. V protons does reduce the remanence considerably Curie T ~ 300 deg. C d. T = -0. 19%/°C obsolete Ductile, low coercive force, isotropic Ductile, low coercive force, isotropic Cons Adjust. Range limitation Demagnetization, requires shielding Temperature gradient, requires temperature stabilization Radiation tolerance Net force in Solenoid (μ > 1) Detlef Swoboda @ CLIC

Permanent Quad Concepts Permanent Magnets • 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%) Steel Pole Pieces (Flux Return Steel Not Shown) 5 June. 2009 PM (Strontium Ferrite) Section Detlef Swoboda @ CLIC

Double Ring Structure –Adjustable PMQPermanent Magnets • 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. 5 June. 2009 Detlef Swoboda @ CLIC

PM strength adjustment Permanent Magnets 5 June. 2009 Detlef Swoboda @ CLIC

The first prototype of “superstrong” Permanent Magnet Quad. Permanent Magnets Cut plane view Soft iron PM Axial view PHOTO Integrated strength GL=28. 5 T (29. 7 T by calc. )　　 　　　　　　 magnet size. f 10 cm Bore f 1. 4 cm Field gradient is about 300 T/m 5 June. 2009 Detlef Swoboda @ CLIC

Adjustable REC Quadrupole Permanent Magnets 5 June. 2009 Detlef Swoboda @ CLIC

Adjustable REC Quadrupole (ATF 2 QD 0) Permanent Magnets 5 June. 2009 Detlef Swoboda @ CLIC

Magnetic Center Shift Double ring 5 June. 2009 Detlef Swoboda @ CLIC Permanent Magnets

Conceptual proposal for SC magnet Superconducting Magnets • • 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]. 5 June. 2009 Detlef Swoboda @ CLIC

SC Magnet Features Superconducting Magnets Pros Cons Ramping, adjust setting Services; i. e. cables, cryo lines) Low sensitivity to external fields Quench, Training, thermal movements, deformations Temperature stability Vibrations Knowledge base, state of the art Cryostat Cross-section, inner bore radius Iron free magnet, no external force High gradient multipole, geometrical tolerances SC back leg coil Coil dominated 5 June. 2009 Detlef Swoboda @ CLIC

Superconducting Magnets 5 June. 2009 Detlef Swoboda @ CLIC

Serpentine winding 5 June. 2009 Detlef Swoboda @ CLIC Superconducting Magnets

IP Magnet Development Superconducting Magnets • 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. 2 deg. K sub-cooled, 2 deg. K superfluid, conduction cooled, …) 5 June. 2009 Detlef Swoboda @ CLIC

Related Issues • 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? 5 June. 2009 Detlef Swoboda @ CLIC

Next Steps • Need to define strategy, resources, timescale. 1. Summary of proposals and R&D done on different technologies. 2. Comparative Synthesis of summaries and Recommendation. 3. Design and R&D (Prototypes, test, measurement) 5 June. 2009 Detlef Swoboda @ CLIC

Resources & Timescale Phase Resources Time 1 2 – 3 magnet experts 1 -2 months 2 Idem 1 month 3 5 June. 2009 Detlef Swoboda @ CLIC

Concluding Remarks • • • Concluding Remarks The present FFD parameters are not very suitable for a conventional electro magnet. SC and PM magnets can reach the magnetic requirements for the FFD. 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 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 it would be interesting of joining ongoing or starting development projects for SC and PM magnets in the field of FELs etc. A proposal for a study and R&D has been presented. What is the effort needed from current state of the art to final design; i. e. when do we find out if and how it can be done? 5 June. 2009 Detlef Swoboda @ CLIC

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). 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. 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. 5 June. 2009 Detlef Swoboda @ CLIC

FF doublet (NLC ZDR) 5 June. 2009 Detlef Swoboda @ CLIC