FF Stabilisation A.Jeremie (Summary of things learned and work done at LAPP, CERN, SYMME, Oxford, SLAC)

Some of the technical work shall be elaborated within the MDI WG, but most results will be obtained in other WGs (beam dynamics WG, LCD, CES WG, Stabilization WG) Highest priority for the work until end 2010 are those subjects linked to the “CLIC critical feasibility items”: - Choice of the magnet technology for the FF magnets - Integration of these magnets into the detectors, and their alignment - Feasibility study of sub-nm active stabilization of these magnets - Luminosity instrumentation - Spent beam disposal - Beam background backsplash from the post-collision collimators and dumps into the detector - Intrapulse-Beam feedback systems in the interface region Excerpt from MDI mandate

Status of design Simulations 0.13 nm with feedback and TMC table Laser-based stabilisation Measurements of GM at DESY/CERN Acoustic noise effect Several PhDs: –S.Redaelli (CERN) 2003 –B.Bolzon (LAPP) 2007 –M.Warden (Oxford) ~2010 –R. LeBreton (SYMME) ~2011 Each time a new team starts this study, there is a non negligible “learning period”. TolerancesFinal Focusing Quadrupoles Vertical0.1 nm > 4 Hz Horizontal5 nm > 4 Hz

Example of spectral analysis of different disturbance sources Acoustic disturbance : Amplified by the structure itself : the eigenfrequencies Ground motion : Seismic motion Cultural noise A pink noise on a large bandwidth =>mechanical stabilization means to isolate and compensate /reject

Mechanical structure and its instrumentation  Actuators used for active control 2.5 m long Force = 19.3 N Maximal displacement = 27.8 μm Resolution = 0.28 nm Can be made with magnetic shielding Resist to 100krad (accumulated dose) - A stacking of PZT patches - Active rejection of cantilever beam resonances: home-made Compensation CERN TMC active table for isolation

From the Finite Element Model to the State-Space Model Tests in simulation Active rejection of cantilever beam resonances: home-made Ex : force (actuator) applied to a point N.Gefffroy et al

 Instrumentation and algorithm efficient for an active rejection of wide vibration peaks down to the sub-nanometre level above 5Hz  Factor 60 of damping between 5Hz and 80Hz down to 0.13nm Active rejection of cantilever beam resonances: home-made  The two first resonances entirely rejected Experimental test L.Brunetti et al (EPAC/Genova 2008)

Instrumentation

How to measure vibrations/ dynamic displacements with amplitudes of 0.1 nm? Seismometers (geophones) VelocityAcceleration Accelerometers (seismic - piezo) Streckeisen STS2 Guralp CMG 3T Guralp CMG 40T Eentec SP500 PCB 393B31 2*750Vs/m2*800Vs/m 30 s -50 Hz120 s -50 Hz 360s -50 Hz 2*750Vs/m2000Vs/m 60 s -70 Hz 1.02Vs 2 /m x,y,z z 10 s -300Hz z 13 kg 13.5 kg 7.5 kg0.750 kg0.635 kg electrochemical Output measurement Endevco 86 PCB 393B12 B&K 450B3 10V/g 98mV/g 0.01Hz-100Hz0.3-6kHz0.05-4kHz modal analysis Prices range from 1keuro to 25keuros kg0.210 kg zzz 0.05nm 0.25nm 0.05nm 11.19nm100nm Measured noise >5Hz LAPP/CERN

Actuators APA actuator from Cedrat, tested at LAPP Characterisation of Accelerometer Reference test bench: Membrane Developped at CERN

Feedback 2 - A local model of the structure : for the disturbances amplified by eigenfrequencies. 3 - A complete model of the structure : for the entire structure 1 - A knowledge of the structure at strategic points : for lumped disturbances f0f0 f1f1 fifi A complete model of the process A knowledge of the process at strategic points A local model of the process

Complete simulation: multi-sensor/multi- actuator configuration Complete model reduced to 8 nodes B.Caron et al SYMME

Replace TMC table by a more compact system

ATF2 FF experience

Ground Shintake monitor Final doublets Beam Interference fringes We want the measurement to have a coherent behaviour with respect to the “beam” => Relative motion between Shintake monitor and final doublets: 6-7nm in the vertical axis above 0.1Hz 4m Good ground motion coherence: measured on KEK site  Separate stiff supports rigidly fixed to the floor Specifications Study the honeycomb block but without feet If Shintake Monitor and FD on separate active supports, coherence is lost

Is the honeycomb table rigid enough? Impact hammer on table Modal deformations  for each resonance (up to 150Hz)  In the three axis Modes1) T-X2) T-Y3) R-Z4) T-Z5) R-Y6) R-X Frequency (Hz) Damping (%) first modes: rigid body modes in 6 degrees of freedom 2 tri-axis accelerometers Michael GUINCHARD (CERN) Z X Y T: Translation R: Rotation  Fix table on whole surface to remove these modes Table fixed on 4 rigid supports at the 4 corners The table is a rigid body, but the feet are not

 Without any masses: 526.1Hz  Even higher than in free configuration!  With masses: 135.2Hz  Fall of the eigenfrequency but still high Table fixed directly to the floor on 1 entire side Choice of the ATF2 collaboration: Get the same table to send it to Japan and fix it to the floor Bees wax: good vibration transmission, can be unglued, stable in time, rad hard Honeycomb table 3 steel plates bolted to the floor Bees wax Set-up can be moved in the future simulation

Vibration measurements ToleranceMeasurement (between QD0) Measurement (between QF1) Vertical7 nm (for QD0) 20 nm (for QF1) 4.8 nm6.3 nm Perpendicular to the beam ~ 500 nm30.7 nm30.6 nm Parallel to the beam ~ 10,000 nm36.5 nm27.1 nm

SC magnet steps Motivation: have an active stabilisation as planned in ILC and CLIC => need to evaluate the usefulness of an active system at ATF2 /Benoit’s work plan/soon at KEK LAPP/CERN/LAL/KEK Need a magnet: – Test it with cryogenics/ B.Parker/ BNL/ soon – Measure vibrations with seismic and laser interferometry of cold mass mouvmt. LAPP/CERN / at BNL? When magnet ready/ Oxford (Urner) at BNL? – Identify vibration sources like GM, cryolines, acoustic LAPP/CERN / at BNL? When magnet ready Design support: – With stabilisation/isolation LAPP/BNL – Cryoline isolation CERN – With compensation (multisensor/multicatuator vs single sensor/single actuator) LAPP/UDS How many FD magnets in same cryostat? LAL/CERN/LAPP… Already achieved 0.13nm rms at 4Hz combining commercial isolation “x10”(CLIC table) and “single” compensation”x3” but in laboratory on a mock-up not in accelerator environment

CLIC FF configurations Courtesy Evgeny Solodko

Pending issues Available resources: – LAPP: A.Jeremie, G.Deleglise, L.Brunetti + mechanic ( all part time) – SYMME: R.LeBreton, A.Badel, B.Caron (part time) – CERN: Most effort in CERN contribution to “stabilisation” is on MB quad (even if we can learn from this work), H.Schmickler – Oxford: Monalisa team on MB quad, ATF2 and CLIC FF Financing: – EuCARD, White paper (although MB), CERN and CNRS Schedule: – Strongly influenced by CDR in 2010! Tasks: – Get a magnet prototype (not feasible before CDR!) – Demonstrate stability to desired level: On laboratory prototype (LAPP and SYMME): ongoing In an accelerator environment (CERN and ATF2): – possibly on CESRTA during 2010 (under discussion) – learn from MB quad stabilisation prototypes during 2010 – later ( ) on ATF2