CLIC MDI Final Focusing Magnet Stabilisation Studies Recent History Conventional Facility Design for NLC Stanford Linear Accelerator Center, March 10 to 28, 2003 CARE/ELAN CERN November CLIC07 Workshop, October 2007 CLIC07 Workshop, Stabilisation day at CERN, March 18 Nanobeam 2008 (Novosibirsk, 27 May 2008 ) EUROTeV Scientific Workshop at Uppsala,August Oct Detlef CLIC MDI working group (Some) Literature Preliminary Results of the Ground Vibration Measurements at Potential Linear Collider Sites and Reference Places (2003 SLAC) Vibration stabilization for the final focus magnet of a future linear collider (November 2005) Status report on active stabilisation of a linear collider final focus quadrupole mock-up (2006) The stabilisation of final focus system (December 2007 Pramana) US Particle Accelerator School, January 22-26, 2007 in Houston, Texas Status of Mechanical Stabilization (2008 Uppsala) Vibration stabilization for a cantilever magnet prototype at the sub-nanometer scale (July 2008) Study of vibrations and stabilization at the sub-nanometre scale for clic final doublets (2008) CTF3 module and CLIC Final Doublet stabilization (??) 8 Oct Detlef CLIC MDI working group Global requirements Stability~ nm Spot sizeSome nm (40 x 1) Beam Measurement accuracy~ 1 % Q-pole strength accuracy ~ 10^-3 --> beam mismatch dominated by errors in measurement and not in magnets Tuning accuracy~ 10^-4 (0.1 mT) Alignment Tuning frequenciesvibration/ripple: t < 1/5 s stability/drift: t < 1 hr long-term stability: t < 1 week very long term stability: t < 1 month extremely long term stability: t < 1 year magnets can be constructed, supported, and monitored so as to meet alignment tolerances 8 Oct Detlef CLIC MDI working group CLIC main parametersvalue Center-of-mass energy3 TeV Peak Luminosity71034 cm-2 s-1 Repetition rate50 Hz Beam pulse length200 ns Average current in pulse1 A Hor./vert. IP beam size bef. pinch53 / ~1 nm 5 CLIC 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 8 Oct. 2008Detlef CLIC MDI working group FF doublet (NLC ZDR) 8 Oct Detlef CLIC MDI working group 8 Oct Final Focusing Use telescope optics to demagnify beam by factor M = f 1 /f 2 typically f 2 = L * f1f1 f 2 (=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 CLIC MDI working group 8 Oct. 2008Detlef CLIC MDI working group8 Chromaticity correction Minimization of chromatic distortions: factors that influence the solutions to this problem: 1.a reduction in the momentum spread (not always feasible) would reduce the magnitude of the problem 2.The chromatic distortion of a FFS lattice is a function of the distance L*. The closer and stronger the lens the smaller is the distortion. 3.Sextupoles in combination with dipoles (provide dispersion) can be used to cancel chromaticity. Sextupoles introduced as pairs, separated by a I transform do not generate second order geometric aberrations. However the dipoles introduce emittance growth and energy spread due to synchrotron radiation. Serious constraint. FF design Balance between these competing effects 8 Oct Novel local chromaticity correction scheme P.Raimondi, A.Seryi, originally NLC FF and now adopted by all LC designs. Detlef CLIC MDI working group 8 Oct. 2008Detlef CLIC MDI working group10 Elements of LC Final Focus System Summary In Linear Colliders, nanometer size beams are obtained by: Final Quadrupole Doublet telescopic system FD Collateral effects: generate strong chromatic aberrations Sextupoles to correct FD chromatic aberrations SEXT collateral effects: generate geometric aberrations Sextupoles located at beginning of -I transformer (or equivalent transform) then correct geometric aberrations Dipoles to supply dispersion for Sextupoles correction BEND collateral effects: generate synchrotron radiation STUDY OF SOME OPTIONS FOR THE CLIC FINAL FOCUSING QUADRUPOLE CLIC Note 506 M. Aleksa, S. Russenschuck 8 Oct Detlef CLIC MDI working group Permanent Magnets MaterialCharacteristics samarium cobalt (Sm2Co17)brittle neodymium iron boron (NdFeB) can lose strength under irradiation ultrahigh coercivity grades show very small remanence losses, 300Hz Amplification at resonances Impact of acoustic noise 8 Oct. 2008Detlef CLIC MDI working group 8 Oct integrated displacement RMS (with active table ON) Tests with the large prototype: quiet room 1 nm Actuator electronic noise at 50 Hz Detlef CLIC MDI working group 8 Oct Results : integrated displacement RMS Tests with the large prototype Active control CIM Detlef CLIC MDI working group 27 Conclusion and future prospects Vibration sensors and instrumentation Ground motion measurements from low to high frequencies (0.1Hz 2000Hz) Measurement chain found for active rejection of CLIC final doublets vibrations (1/10nm for f>5Hz) Collaboration with PMD Scientific company to test new electrochemical sensors tending toward the final specification of CLIC Test of small capacitive sensors with 0.1nm resolution (P75211C of PI) Vibration study of a canteliver beam at high frequencies (>300Hz) High impact of acoustic noise up to at least 1000Hz for CLIC FD Measurements to perform on canteliver magnets in an operating accelerator site 8 Oct. 2008Detlef CLIC MDI working group 28 Active stabilization of a canteliver beam down to the sub- nanometre level above 5Hz Feasibility of active isolation from the ground proven Active rejection feasibility of resonances proven On-going study: multi-sensors multi-actuators system in order to stabilize the beam all along its length Stabilization to do on a more complex structure closer to the FD design Conclusion and future prospects Simulations give us information about optimal location of sensors and actuators and their number Simulations will allow us to follow the evolution of final doublets design 8 Oct. 2008Detlef CLIC MDI working group Beam delivery system Crab XP 1 PM SC RM Magnet Technology IP concept 8 Oct Detlef CLIC MDI working group 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? 8 Oct Detlef CLIC MDI working group Summary (2) IP layout Push-pull vs. 2 nd IP? Need to define strategy, resources, timescale. 8 Oct Detlef CLIC MDI working group Reserve 8 Oct Detlef CLIC MDI working group Definition of Switched-On Length 16 series of outer ring switching No. 8 cm 4 cm 2 cm 1 cm Switched- on length 1 ON 15cm 2 ON OFF 14cm 3 ON OFFON 13cm 4 ON OFF 12cm 5 ONOFFON 11cm 6 ONOFFONOFF 10cm 7 ONOFF ON 9cm 8 ONOFF 8cm 9 OFFON 7cm 10 OFFON OFF 6cm 11 OFFONOFFON 5cm 12 OFFONOFF 4cm 13 OFF ON 3cm 14 OFF ONOFF 2cm 15 OFF ON 1cm 16 OFF 0cm ON Cut Plane View 8 Oct Detlef CLIC MDI working group Seismic Measurements 8 Oct Detlef CLIC MDI working group Ground CERN Oct Detlef CLIC MDI working group 8 Oct nm at 4Hz test No dedicated site in CTF3 Initial tests in Annecy CLEX with accelerator environment Mechanical measurement lab (not a stable zone) Work with survey to find a base-plate site (where alignment tests are made?) LHC tunnel had been suggested, but difficult to access (soon?) Material: old CERN/CLIC table (currently in Annecy) or buy a new one with more accessible control Sensor development Install final focus magnet mock-up on test support Use of different sensors compare with laser interferometer: reference on floor and measurement on mock-up Detlef CLIC MDI working group 8 Oct Association of active and passive isolation : Not heavy enough to use industrial products, but it is possible with a larger prototype. The small and elementary mock-up Active isolation The passive layer : Require active isolation f Passive isolation is efficient Resonant frequency of the rubber Detlef CLIC MDI working group 8 Oct FD stability Things we dont know: What is the FD configuration? Saclay? Is it normal or superconducting? (M.Aleksas work: Sm 2 Co 17 ) How close to detector? MDI issues=> free-fixed or fixed-fixed configuration? Simulations for different configurations: Free, free-fixed 1 support, multi-support Detlef CLIC MDI working group 8 Oct. 2008Detlef CLIC MDI working group39 Telescopic system In practice, to achieve a telescopic system in both planes we need at least two quadrupoles to simulate each lens of the telescope, and the magnification may be different in each plane. 8 Oct. 2008Detlef CLIC MDI working group40 Final focus chromaticity Strong FD lens has high degree of chromatic aberrations Typically L*~4m, ~0.01, ~0.1mm If uncorrected chromatic aberration of FD would completely dominate the IP spot size! Need compensation scheme. using FD 8 Oct. 2008Detlef CLIC MDI working group41 Chromatic corrections concepts particle with the same input coordinate but a different momentum p1 see the quadrupoles with strenghts than p0. to compensate for this chromatic difference a lattice can be designed where particles of greater momentum encounter an extra quadrupolar field to compensate for the increased momentum. This is achieved by the introduction sextupoles and dipoles into the lattice structures. 8 Oct. 2008Detlef CLIC MDI working group42 Chromatic corrections The magnetic induction of a quadrupole is a linear function of the variable x, y. A particle with momentum p will be affected differently than a particle with momentum p0. The corresponding strenghts of the quadrupole the focal strenght of the quadrupole decreases as the momentum increases. Chromatic properties of a sextupole may be interpreted similarly. Chromatic effects occur because particles with different momenta respond differently to a given magnetic field. 8 Oct. 2008Detlef CLIC MDI working group43 Chromatic corrections concepts This lattice has the potential of chromatic corrections. While a particle p0 follows the central trajectory, the particle p1 with 0 will follow the trajectory defined by the function d x (s). The function is nonzero after the first dipole. At position 1, p1 encountered slightly different quadrupolar strengths than p0. Lets arrange a sextupole at position 1, which is not affecting p0. Particle p1 will experience a gradient proportional to its displacement, therefore proportional to B1QF B2 8 Oct. 2008Detlef CLIC MDI working group44 If proper sextupole strength is chosen, the extra gradient exactly compensates the difference in gradient experienced by particles with different momenta in the preceding quadrupole. However, in this process the sextupoles will in general introduce geometric distortions. A procedure to eliminate chromatic aberrations without introducing second-order geometric aberrations is the following. Chromatic corrections concepts 8 Oct. 2008Detlef CLIC MDI working group45 IP beta bandwidth SLC measured beam size at IP with momentum 8 Oct. 2008Detlef CLIC MDI working group46 Interlaced pairs Ideally, from second-order geometric aberrations point of view, is to assemble I transformers that do not interfere between x, y planes (separated in space). This often requires prohibitively long and expensive sections. Consider interlaced sextupole pairs. A particle arrive at first sextupole S1 with displacement x1. As it gets to the first sextupole of pair S2, its motion is perturbed and particle reaches second sextupole S1 with a displacement not equal to x1. Not exact cancellation from the second sextupole S1. However, since the disturbance by sextupole S2 is of order two, the uncorrected geometric aberrations of the pair S1 are then of order three and four fine.