And Proposal for a short term RampD effort Recent Events Conventional Facility Design for NLC Stanford Linear Accelerator Center March 10 to 28 2003 CAREELAN meeting CERN November 23 25 2005 ID: 797781
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Slide1
CLIC FFD
Final Focusing Magnet Assessment
And
Proposal for a short term R&D effort
Slide2Recent Events
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 2007Stabilisation day at CERN, March 18 2008Nanobeam 2008 (Novosibirsk, 27 May 2008)EUROTeV Scientific Workshop at Uppsala,August 2008CLIC08 Workshop @ CERN, 14-17 Oct. 08CLIC BDS WS @ CERN, Dec. 08
5 June. 2009
Detlef Swoboda @ CLIC
Slide3References
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/70/4SUPERFISH - 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-2008-01IP solenoid and SR studies, DALENA, Barbara, CLIC08 Workshop, CERN, 14-17 October 2008Permanent Magnet Work at Fermilab 1995 to Present, James T Volk, FNALA Super-Strong Permanent Magnet Quadrupole with Variable Strength, Y. Iwashita, (ICR, Kyoto U.) et al, LINAC2004 Lübeck
MODIFICATION AND MEASUREMENT OF THE ADJUSTABLE
PERMANENT MAGNET QUADRUPOLE FOR THE FINAL FOCUS IN A LINEAR COLLIDER*, Y. Iwashita et al., PAC07
Permanent magnet Final Focus
Quadrupole for ATF2, Y. Iwashita et al, ATF2 19-21 Dec 2007CONTINUOUSLY ADJUSTABLE PERMANENT MAGNET QUADRUPOLE FOR A FINAL FOCUS, Takanori Sugimoto, EPAC08NLC Superconducting Final Focus Magnets, Brett Parker, BNL-SMD, Nov. 2002COMPACT SUPERCONDUCTING FINAL FOCUS MAGNET OPTIONS FOR THE ILC*, B. Parker et al, PAC 2005Nested 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 1983Feasibility for Quadrupole for CLIC Final Focus, P. Sievers, 1988Conceptual design of a 5 T/mm Quadrupole for linear collider final focus, K.Egawa, T.Taylor, CERN LEP-MA 89-08Crab collisions for the CLIC final focus, J. Hagel, B. Zotter, CLIC Note 210, 14 Sep. 1993
5 June. 2009
Detlef Swoboda @ CLIC
Slide4Outline
Requirements and Technology Issues
FFD Magnet Technologies
Proposals and ProtosDesign IssuesConcluding Remarks5 June. 2009Detlef Swoboda @ CLIC
Slide55 June. 2009
Final Focusing
Use telescope optics to
demagnify beam by factor M = f1
/f
2
typically f
2= L*f1f2 (=L*)The final doublet FD requires magnets with very high quadrupole gradient exceeding ~250 Tesla/m superconducting or permanent magnet technology?
Detlef Swoboda @ CLIC
Requirements
magnets can be constructed, supported, and monitored
to
meet alignment tolerances
Slide6Global requirements
5 June. 2009
CLIC main parameters
valueCenter-of-mass energy3 TeVPeak Luminosity2·10^34 cm-2 s-1Repetition rate
50 HzBeam pulse length
230 ns
Average current in pulse
1 AHor./vert. IP beam size bef. pinch53 / ~1 nmStability~ nmSpot sizeSome nm (40 x 1)Beam measurement accuracy~1 %Q-pole strength accuracy~ 10^-3 beam miss-match dominated by measurement errors, not by magnetsTuning accuracy QD0~ 10^-6 (0.02 G)Alignment tuning frequenciesVibration/ripple t< 1/5 sStability/drift t < 1 hrDetlef Swoboda @ CLIC
Requirements
Slide7CLIC FF doublet parameters
5 June. 2009
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%
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]
G ~ 1/R²
Bpole
~ R
Doublet magnetic length:
α
=( h1*lFFD*dBZ/dx)/B0*ρ; l* ≈ h1/ αlFFD = (B0*ρ*dx/dBZ )/l* = (3.3356*1.5*10³/406.6)/3.5 = 3.51 [m]
Detlef Swoboda @ CLIC
Requirements
Slide8Max. Gradients
5 June. 2009
SC type
Temp [K ]Bcr [T]J [A/m2]
G [T/m]Nb-Ti
1.9
5
6*10^9300Nb3Sn1.951*10^10500Detlef Swoboda @ CLICRequirements
Slide9RT
Quadrupole
5 June. 2009
2 mm
Detlef Swoboda @ CLIC
Conventional Magnets
Slide10RT LHC type
Quadrupole
5 June. 2009
Detlef Swoboda @ CLICConventional Magnets
Slide11Conventional
Quadrupole
5 June. 2009
RT or SCTechnologyDetlef Swoboda @ CLICConventional Magnets
Slide12Conceptual 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.5 June. 2009Detlef Swoboda @ CLIC
Permanent Magnets
Slide13Design issues for 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 magnetCoating requirementsAcceptance tests or performance requirementsNot 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
Permanent Magnets
Slide14PM 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.5 June. 2009ParameterSr FerriteNd-FeSm-CoBr [T]
0.3851.230
1.050
H
ci [Oe]30501200011000BHmax [MGO]3.535.026.0Temp var. [%]0.180.110.045Cost [$/cm³]0.042.753.66Detlef Swoboda @ CLICPermanent Magnets
Slide15… PM materials
5 June. 2009
Material
State
Cost
Bhmax
Coercivity
TmaxMachinability
Index
MGOeHci
(KOe)
(
o
C)
Nd-Fe-B
(sintered)
65%
<45
<30
180
Fair
Nd-Fe-B
(bonded)
50%
<10
<11
150
Good
Sm-Co
(sintered)
100%
<30
<25
350
Difficult
Sm-Co
(bonded)85%<12<10150FairAlnicoHard30%<10<2550DifficultFlexible5%<4<3
300
Fair
Ferrite
2%
<2
<3
100
Excellent
Critical
Temperatures for Various Materials
Material
T
Curie
(degC)
T
max
(degC)
Neodymium Iron Boron
310
150
Samarium Cobalt
750
300
Alnico
860
540
Ceramic
460
300
Detlef Swoboda @ CLIC
Permanent Magnets
Slide16Studies on Radiation effects for PM
SmCo
and especially Sm
2Co17 withstand radiation 2 to 40 times better than NdFeB materials.SmCo exhibits significant demagnetization when irradiated with a proton beam of 10 MGy to 100 MGy. NdFeB test samples were shown to lose all of their magnetization at a dose of 7 x 100 kGy, and 50% at a dose of 4 x 10 kGy.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. 2009Detlef Swoboda @ CLIC
Permanent Magnets
Slide17Reluctance
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. 2009Detlef Swoboda @ CLICPermanent Magnets
Slide18PM Materials & Features
5 June. 2009
Material
Characteristics
samarium cobalt (Sm2Co17)
Brittle
anisotropic
corrosion resistant, no coating requiredSmx
Er
l-x
Co
Stability ~ 10
-6
/hr
neodymium iron boron (
NdFeB
)
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
MeV
electrons
irradiation by 200
MeV
protons does reduce the
remanence
considerably
Curie T ~ 300
degCStrontium Ferrite (SrFe )dT = -0.19%/°CBarium Ferrite (BaFe )obsoleteFeCrCoDuctile, low coercive force, isotropicAlnicoDuctile, low coercive force, isotropicProsConsNo pwr cablesAdjust. Range limitationNo cryoDemagnetization, requires shieldingNo vibrationTemperature gradient, requires temperature stabilizationHigh coercivityRadiation tolerance
Net force in Solenoid (μ > 1)
Detlef Swoboda @ CLIC
Permanent Magnets
Slide19Permanent 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 Pole Pieces (Flux Return Steel Not Shown)
Rotatable PM (
Nd
-Fe-B) Blockto Adjust Field (+/- 10%)PM (Strontium Ferrite) Section5 June. 2009Detlef Swoboda @ CLICPermanent Magnets
Slide20Double 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.5 June. 2009
High gradient
heat load
Detlef Swoboda @ CLIC
Permanent Magnets
Slide21PM strength adjustment
5 June. 2009
Detlef Swoboda @ CLIC
Permanent Magnets
Slide22The first prototype of
“
superstrong
” Permanent Magnet Quad.Integrated strength GL=28.5T (29.7T by calc.) magnet size. f10cm Bore f1.4cm Field gradient is about
300T/m
PHOTO
Cut plane view
Axial viewPMSoft iron
5 June. 2009
Detlef Swoboda @ CLIC
Permanent Magnets
Slide23Adjustable REC
Quadrupole
5 June. 2009
Detlef Swoboda @ CLICPermanent Magnets
Slide24Adjustable REC
Quadrupole
(ATF2 QD0)
5 June. 2009Detlef Swoboda @ CLICPermanent Magnets
Slide25Magnetic Center Shift
5 June. 2009
Detlef Swoboda @ CLIC
Permanent MagnetsDouble ring
Slide26Conceptual 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].5 June. 2009Detlef Swoboda @ CLIC
Superconducting Magnets
Slide27SC Magnet Features
5 June. 2009
Pros
Cons
Ramping, adjust setting
Services; i.e. cables, cryo lines)
Low sensitivity to external fields
Quench, Training, thermal movements, deformationsTemperature 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
Detlef Swoboda @ CLIC
Superconducting Magnets
Slide285 June. 2009
Detlef Swoboda @ CLIC
Superconducting Magnets
Slide29Serpentine winding
5 June. 2009
Detlef Swoboda @ CLIC
Superconducting Magnets
Slide30IP Magnet Development
5 June. 2009
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 degK sub-cooled, 2
degK
superfluid
, conduction cooled, …)
Detlef Swoboda @ CLICSuperconducting Magnets
Slide31Related 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 technologyHigh gradient ( N x 100 T/m) requires permanent/SC technologyCombination of both types?5 June. 2009Detlef Swoboda @ CLIC
Slide32Next Steps
Need to define strategy, resources, timescale.
Summary of proposals and R&D done on different technologies.
Comparative Synthesis of summaries and Recommendation.Design and R&D (Prototypes, test, measurement)5 June. 2009Detlef Swoboda @ CLIC
Slide33Resources & Timescale
5 June. 2009
Phase
ResourcesTime12 – 3 magnet experts1 -2 months2Idem1 month3Detlef Swoboda @ CLIC
Slide34Concluding 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
Concluding Remarks
Slide35FFD 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
Slide36FF doublet (NLC ZDR)
5 June. 2009
Detlef Swoboda @ CLIC
Slide37Measurements
Center Stability
Strength
Multipolar contentsRepeatability in TuningRadiation HardnessVibrationGeometry5 June. 2009Detlef Swoboda @ CLIC
Slide38CLIC Linear Collider (
~2019)
:
Final doublets in cantilever
2m50
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
Below 5Hz:
Beam position control with deflector magnets efficient
Above 5Hz:
Need to control relative motion between final doublets
5 June. 2009
Detlef Swoboda @ CLIC
Slide395 June. 2009
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
Slide40STUDY OF SOME OPTIONS FOR THE CLIC FINAL FOCUSING
QUADRUPOLE
CLIC Note 506
M. Aleksa, S. Russenschuck5 June. 2009Detlef Swoboda @ CLIC