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• 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

9 Feb. 2009 2Detlef Swoboda @ CLIC MDI working group

http://indico.cern.ch/conferenceDisplay.py?confId=17870

http://www5.tsl.uu.se/EUROTeV2008

http://cern.ch/CLIC08

References1. Introduction to Transfer lines and Circular Machines P.J. Bryant/CERN84-042. Selection of Formulae and Data useful for the Design of AG Synchrotrons C. Bovet et al,

CERN/MPS-SI/Int DL/70/43. Permanent Magnet Work at Fermilab 1995 to Present, James T Volk, FNAL4. A Super-Strong Permanent Magnet Quadrupole with Variable Strength, Y. Iwashita, (ICR, Kyoto

U.) et al, LINAC2004 Lübeck5. Vibration stabilization for a cantilever magnet prototype at the sub-nanometer scale L. Brunetti

et al. ,LAPP-TECH-2008-016. NLC Superconducting Final Focus Magnets, Brett Parker, BNL-SMD, Nov. 20027. COMPACT SUPERCONDUCTING FINAL FOCUS MAGNET OPTIONS FOR THE ILC*, B. Parker et al,

PAC 20058. Nested SC quad proto FNAL. ILC-Americas Workshop: SLAC, October 14-16, 2004.9. Estimating Field quality in low-B Superconducting Quadrupoles and its impact on Beam

Stability, E. Todesco et al, PAC 07 proceedings 353-355.10. SUPERFISH - A Computer Program, K. Halbach and R. F. Holsinger, Particle Accelerators 7 (1976)

213-222.11. IP solenoid and SR studies, DALENA, Barbara, CLIC08 Workshop, CERN, 14-17 October 2008

9 Feb. 2009 Detlef Swoboda @ CLIC MDI working group 3

f1 f2 f2

IP

final doublet

(FD)

9 Feb. 2009 4

Final Focusing

Use telescope optics to demagnify beam by factor M = f1/f2 typically f2= L*

f1 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

Global requirementsmagnets can be constructed, supported, and monitored so as to meet alignment tolerances


CLIC main parameters value

Center-of-mass energy 3 TeV

Peak Luminosity 7·1034 cm-2 s-1

Repetition rate 50 Hz

Beam pulse length 200 ns

Average current in pulse 1 A

Hor./vert. IP beam size bef. pinch 53 / ~1 nm

CLIC FF doublet parameters


QF1 QD0

L* 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/m3

Dodec. error 1016 T/m5

Peak field 0.94 - 2.20 T

Field stability 10^-4

Energy spread ± 1 %

STUDY OF SOME OPTIONS FOR THE CLIC FINAL FOCUSINGQUADRUPOLE CLIC Note 506

M. Aleksa, S. Russenschuck


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.


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.


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.


Sr Ferrite Nd-Iron SM-CobaltBr Gauss 3850 12300 10500

Hci Oersteds 3050 12000 11000BH(max) MGO 3.5 35.0 26.0

Temp variation % 0.18 0.11 0.045Cost $/ cc 0.04 7.75* 3.66

PM Materials & Features


Material Characteristicssamarium cobalt (Sm2Co17) Brittle

corrosion resistant, no coating requiredneodymium iron boron (NdFeB) Ductile

susceptible to corrosion, requires coatingcan lose strength under irradiationultrahigh coercivity grades show very small remanence losses, <0.4%±0.1%, for absorbed doses up to 3 Mgy from 17 MeV electronsirradiation by 200 MeV protons does reduce the remanence considerablyCurie T ~ 300 degC

SmxErl-xCo Stability ~ 10-6/hrStrontium Ferrite (SrFe ) dT = -0.19%/°CBarium Ferrite (BaFe ) obsoleteAlnico Lower performance

Pros ConsNo pwr cables Adjust. Range limitationNo cryo Demagnetization, requires shieldingNo vibration Temperature gradient, requires temperature

stabilizationHigh coercivity Radiation tolerance

Net force in Solenoid (μ > 1)

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

Steel

PM

PM

Steel Pole Pieces (Flux Return Steel Not Shown)

Rotatable PM (Nd-Fe-B) Blockto Adjust Field (+/- 10%)

PM (Strontium Ferrite) Section


Double Ring Structure –Adjustable PMQ-

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.


• High gradient heat load

The first prototype of “superstrong” Permanent Magnet Quad.

Integrated strength GL=28.5T (29.7T by calc.) 　　　　　　　　　　　　 magnet size. f10cmBore f1.4cmField gradient is about 300T/m

PHOTO

Cut plane view

Axial view

PM

Soft iron

dzdrdB

GL


Magnetic Center Shift


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].


SC Magnet Features


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 coilCoil dominated

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 degK superfluid, conduction cooled, …)


Measurements

• Center Stability• Strength• Multipolar contents• Repeatability in Tuning• Radiation Hardness• Vibration• Geometry


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.


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?


Summary (2)• IP layout

– Push-pull vs. 2nd IP?• Need to define strategy, resources, timescale.

Task Qualification Modeling (FEM), Simulation Mech. Eng. Optics, beam performance Beam optics specialist Design Draftsman Models, Prototypes, Test assemblies Technician, Mech. Eng. El. Magnetic measurements El. Eng. Survey, Expertise Survey Eng. Magnets Conception El. Eng. / Physicist


24

CLIC Linear Collider (~2019):

Final doublets in cantilever2m50

Detector

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

Interaction point

Scope of FFS

*yσ

Below 5Hz: Beam position control with deflector magnets efficient

Above 5Hz: Need to control relative motion between final doublets

9 Feb. 2009 Detlef Swoboda @ CLIC MDI working group

9 Feb. 2009 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?

2 pieds 23 41,543 pieds 62,38 79,834 pieds 119,33 133,565 pieds 191,63 213,073200200 900 1700 2500

500 1700 3000300 1300 2200 3200

répartition des pieds en mm Premières fréquences en Hz800 2700

libre encastré des deux cotés encastré d'un seul coté

1ere 23 23,7 3,7

2nd 63,4 65 23

3eme 123,4 126,3 64,2

4eme 202,3 206,5 124,9

libre encastré des deux cotés encastré d'un seul coté

1ere 41,1 39,5 10,6

2nd 109,6 107,9 46,4

3eme 210,2 208,9 115,1

4eme 341,2 340 215,3

Tubulaire

Conique

Fréq

uenc

e en

Hz

Fréq

uenc

e en

Hz

Simulations for different configurations:Free, free-fixed…1 support, multi-support…

Detlef Swoboda @ CLIC MDI working group

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.


FF doublet (NLC ZDR)


Documents

CLIC FFD