Beam Physics Issues of Main Beam Stabilisation A.Jeremie (LAPP) C.Hauviller (CERN)

1) The requirements/basic parameters 2) The status of the design (lattices etc) 3) The tolerances, required instrumentation, alignment and feedback 4) The remaining critical issues 5) The planned actions

CLIC stabilization requirements A large number of luminosity loss sources exist –Need to allocate a budget for each of them Current luminosity loss allocated for magnet jiter: –1% for main linac magnets –1% for BDS magnets, except final doublet magnets –1% for final doublet magnet These are a large fraction of the overall luminosity loss O. Capatina et al., Novosibirsk, 27th of May 2008 L = 5.9 * 10^34 cm-2 s-1 ~40 nm1 nm

CLIC stabilization requirements Overview of the global alignment / stabilization strategy for main linac magnets Once / year: 1.Mechanical pre-alignment => 0.1 mm 2.Active pre-alignment using HLS, WPS, RASNIK => +/- 10  m on a sliding window of 200 m 3.Beam based active alignment with movers – complex procedure => 1  m 4.Beam based alignment with magnet correctors => few nm Once / few weeks –Repeat Once / couple of hours –Repeat but “simplified” procedure “Steady state” procedure presented before (mechanical stabilization ON or OFF depending on magnet) O. Capatina et al., Novosibirsk, 27th of May 2008 Beam OFF Beam ON Mech. Stabil. OFF Mech. Stabil. ON

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

CLIC stabilization requirements O. Capatina et al., Novosibirsk, 27th of May 2008 ? Linac repetition rate 50 Hz BBF<2Hz Final Focusing Quadrupoles Main beam quadrupoles Vertical0.1 nm > 4 Hz1 nm > 1 Hz Horizontal5 nm > 4 Hz5 nm > 1 Hz Numerical simulation: Ratio of the Beam based feedback On / feedback Off for the amplitude of the beam jitter at Interaction Point as a function of frequency f(Hz) Quadrupole magnetic axis vibration tolerances:

Environmental vibration levels – orders of magnitude, CERN site O. Capatina et al., Novosibirsk, 27th of May 2008 LEP ground motion during 1 year 300 µm – 1 mm Ground motion due to Lunar cycle (tides) Several µm 7 sec hum 100 nm, CLEX 10 nm, CLEX Alignment “Slow” motion“Fast” motion Correction with beam- based feedback Mechanical stability of main beam quadrupoles Cultural noise Acoustic noise becomes very important Geophones Accelerometers Required vertical stability for all main linac quads for CLIC: 1 nm Required vertical stability for Final Focus quads for CLIC: 0.1 nm

1) The requirements/basic parameters 2) The status of the design (lattices etc) 3) The tolerances, required instrumentation, alignment and feedback 4) The remaining critical issues 5) The planned actions

Status of design Simulations by N.Geffroy 0.13 nm with feedback and TMC table Acoustic noise effect Measurements of GM at DESY/CERN Multipoint study David’s set-up

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 canteliver beam resonances: home-made

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

 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 canteliver beam resonances: home-made  The two first resonances entirely rejected Experimental test

QD0 Shintake Monitor Table Laser Compact Straightness Monitor Very Schematic View of ATF2 Setup 10cm Vacuum vessel D.Urner et al, Oxford Intensity

Status of design Some quiet sites exist but is it enough? R.Amirikas et al : DESY/EUROTeV

Displacement of the beam: Factor 3 due to the clamping  Factor 8 due to the acoustic noise  Conclusion: High impact of acoustic noise up to at least 1000Hz Displacement VS Acoustic pressure [800; 1000]Hz  Clamping: 3.1pm to 10pm  Factor 3 of amplification  Beam: 15.4pm to 0.37nm  Exceed tolerances (1/10nm)  Factor 24 of amplification Acoustic noise: 49dB to 76dB Vibration study of a canteliver beam at high frequencies Effect of acoustic noise

1) The requirements/basic parameters 2) The status of the design (lattices etc) 3) The tolerances, required instrumentation, alignment and feedback 4) The remaining critical issues 5) The planned actions

Tolerances, required instrumentation, alignment, feedback Benoit’s sensor studies Chemical sensors? Actuators from CEDRAT OK (magnetic field and rad hard) PI?

How to measure vibrations/ dynamic displacements with amplitudes of 0.1 nm? Seismometers (geophones) Velocity Acceleration Accelerometers (seismic - piezo) Vibrometer et interferometer Déplacement MONALISA Streckeisen STS2 Guralp CMG 3T Guralp CMG 40T Eentec SP500 PCB 393B31 2*750Vs/m2*800Vs/m 30 s -50 Hz120 s -50 Hz360s -50 Hz 2*750Vs/m2000Vs/m 60 s -70 Hz 1.02Vs 2 /m x,y,z z 10 s -300 Hz z 13 kg 23 kCHF 13.5 kg7.5 kg0.750 kg0.635 kg 19 kCHF8 kCHF1.7 kCHF electrochemical O. Capatina et al., Novosibirsk, 27th of May 2008 Output measurement

Vibration sensors acquired by LAVISTA team Feasibility study of sub-nanometre measurements Sub-nanometre measurements < 100Hz> 100Hz Ground motion measurements Modal analysis Can be put on a small structure Non-magnetic

Active rejection: DAQ PCI6052E without integrated electronics  Real time acquisition of all sensor types: [1;15k]Hz  Modal analysis with impact testing hammer  16/24 bits with amplifiers of variable gains  Good resolution and high signal to ADC noise ratio Data analysis: PULSE system with state-of-the-art electronics Acquisition system acquired by LAVISTA team  Compatible with our algorithm  Active HP and LP filters and amplifiers  AC/DC, Single-ended/Differential  Low level card: very fast Signal conditioning DAQ PCI6052E Same positive points than PULSE system Feasibility study of sub-nanometre measurements

Real system: Multi degrees of freedom and several deformation modes with different structural damping Experimental modal analysis on CLEX girder Amplification of floor movement O. Capatina et al., Novosibirsk, 27th of May 2008 “Plant” characterization / optimization

Resolution, movement reproducibility? Friction Guiding systems with friction Real resolution 1 μm (0.1 μm ) Solution: Piezo actuators PZT + flexural guides + feedback capacitive sensor O. Capatina et al., Novosibirsk, 27th of May 2008 Actuators with 0.1 nm resolution? Stabilized structures and Piezo actuators with resolution of 0.05 nm exist! But only for few kg and rigid objects.... Techniques to be developed for heavier and larger structures Fernandez Lab, Columbia University NY Traction test on a protein

Different strategies Main beam: Demonstrate stability of 1 nm > 1 Hz for main beam quadrupoles : cheap and reproducible, reliable=> can’t replace thousands of sensors because of wrong initial choice – Main beam quadrupoles to be mechanically stabilized: A total of about 4000 main beam quadrupoles Of 4 types Magnetic length from 350 mm to 1850 mm With a realistic system, in an accelerator environment, to be checked using 2 different methods (seismic sensors/laser interferometry) FF: Demonstrate stability of 0.1 nm > 4 Hz for final doublets => more difficult requirements, unique system, but show stopper

Active WG An integrated approach: stabilization elements to be taken into account at the design phase of CLIC components, ground motion characterization, sensors, actuators, alignment compatibility with beam dynamics => stabilisation WG part of the CLIC Technical Committee: CERN Claude Hauviller and LAPP Andrea Jeremie (EuCARD task coordinator) – LAPP/CNRS: A.Jeremie, B.Bolzon, N.Geffroy, L.Brunetti – CERN: C. Hauviller, K. Artoos, O. Capatina, M. Guinchard, F.Lackner, D. Schulte – SYMME/Université de Savoie: J.Lottin, B.Caron, A.Badel – Oxford: D.Urner – Some other groups interested already several common meetings in 2008 and a task list

1) The requirements/basic parameters 2) The status of the design (lattices etc) 3) The tolerances, required instrumentation, alignment and feedback 4) The remaining critical issues 5) The planned actions

Remaining critical issues Make a compact design Make it work in an accelerator environment – In particular radiation effects have to be considered Radiation level at CLIC not yet estimated Radiation damage effects on electronics: – Total dose – Single event error Experience with other CERN projects have shown Single event error can produce important failures Compatibility with other systems Stability along the whole beam How do we validate the system: in beam line, or stand alone enough, only in vertical direction? Do we need to integrate into BBF or are we independent Do we want to validate by a damping ratio at each frequency or is a mean value enough?

Question from Daniel: how will the results be made available for simulations Do we need to give range and damping factor? We take displacement into account, not position What info is needed for simulation, just the position of magnet or does the simulation need to control the magnet position

1) The requirements/basic parameters 2) The status of the design (lattices etc) 3) The tolerances, required instrumentation, alignment and feedback 4) The remaining critical issues 5) The planned actions

Present goal for CLIC: –Demonstrate all key feasibility issues and document in a Conceptual Design Report by 2010 –CLIC stabilization feasibility to be demonstrated by 2010 Actions: –Characterize vibrations/noise sources in an accelerator and detectors Summary of what has been done up to now –CLIC Stabilization Website: Additional correlation measurements to be done at LHC interaction regions for distances from several m up to 1000 m Continue measurements in CLEX environment at different installation phases Work plan (planned actions) O. Capatina et al., Novosibirsk, 27th of May 2008

Actions: –Overall design Linac –Compatibility of linac supporting system with stabilization (including mechanical design) –Design of quadrupole (we have to stabilize the magnetic axis) and build a mock-up with all mechanical characteristics Final focus –Integration of all the final focus features: types of supporting structures, coupling with detector –Sensors Qualification with respect to EMC and radiation Calibrate by comparison. Use of interferometer to calibrate other sensors. Create a reference test set-up Work plan O. Capatina et al., Novosibirsk, 27th of May 2008

Actions: –Feedback Develop methodology to tackle with multi degrees of freedom (large frequency range, multi-elements) Apply software to various combinations of sensors/actuators and improve resolution (noise level) –Overall system analysis Stability, bandwidth,… Sensitivity to relaxed specifications –Integrate and apply to linac A mock-up should be ready to provide results by June 2010 with several types of sensors including interferometers Mock-up to be integrated in accelerator environment – Where? Work plan O. Capatina et al., Novosibirsk, 27th of May 2008

Back-up slides

Pulse separation 20 ms Bunch train length 156 ns Bunch separation length 0.5 ns (6 periods) 312 bunches / pulse CLIC stabilization requirements Some CLIC overall parameters Center of mass energy 3 TeV Main linac RF frequency 12 GHz Linac repetition rate 50 Hz O. Capatina et al., Novosibirsk, 27th of May 2008 BBF<2Hz

CLIC stabilization requirements Overview of the global alignment / stabilization strategy for main linac magnets “Steady state” procedure: But, before “Steady state”, alignment has to be carried out O. Capatina et al., Novosibirsk, 27th of May 2008 Beam position measurement with BPM Beam based feedback correction with magnet correctors Mechanical stabilization ON Isolation? What do they correct? position, magnetic center, magn field intensity?

Another approach of the problem Active compensation Test an intermediary solution : to control a larger bandwidth 3 - A local model of the structure : for the disturbances amplified by eigenfrequencies. 1 - A complete model of the structure : too complex 2 - A knowledge of the structure at strategic points : the initially developed algorithm f0f0 f1f1 fifi A complete model of the process A knowledge of the process at strategic points A local model of the process L.Brunetti

Active isolation  Test of active isolation on a small mock-up…  Passive isolation : attenuates all the high frequency disturbances but amplifies the low frequency disturbances (like a resonant filter).  Active isolation : attenuates the disturbance amplified by the passive isolation (low frequencies disturbances). (Thesis of S. Redealli) In the case of a possible partnership, we have no competence about active isolation. In the case of the development of a low cost table (this one is very expensive), we have no information about the mechanism (mainly the feedback loop). STACIS foot : Reasons of this study and the STACIS feet

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 Δf Passive isolation is efficient Resonant frequency of the rubber

Ground Plate on floor –Use shared platform and proximity –Glue to floor? Mount on table/girder –Can seismic sensors be mounted upside-down? –Is it necessary to clamp down seismic sensors? Ground Plate Interfero- Meter head Seismic sensor End of Interfero- Meter Table/Girder Seismic sensor 120cm Interferometer Vacuum tube Dia: 20 cm Optics directly mounted on ground plate Optics mounted Directly on table Compare laser interferometer and seismic sensors