1 Nanopositioning of the main linac quadrupole as means of laboratory pre-alignment David Tshilumba, Kurt Artoos, Stef Janssens D. Tshilumba, CERN, 03 February 2015

2 O BJECTIVES Investigate ways to combine alignment and nanopositioning into one actuation system Upgrade of Type 1 nanopositioning prototype Treatment of parasitic resonance modes Reduction of translation – roll motion coupling D. Tshilumba, CERN, 03 February 2015

3 C URRENT SYSTEM OVERVIEW Coarse stage (cams) Resolution : 0.35µm Stiffness: 50kN/µm Stroke: 3mm Fine stage (piezo stacks) Resolution: 0.25nm Stiffness : 460N/um (piezo) Stroke: 5µm Limitations: precision of coarse stage (~10µm) insufficient stroke of fine stage for thermal load in tunnel ( >100µm) D. Tshilumba, CERN, 03 February 2015

4 G OALS  Goals:  increase the range of fine stage  Perform nanopositioning ParametersValue Resolution<0.25nm Precision0.25nm step displacement0.25nm up to 50nm Speed10μm/s Rise time1ms Settling time5ms D. Tshilumba, CERN, 03 February 2015

5 D ISTURBANCE SOURCES Ground motion External forces (Water cooling, ventilation,…) D. Tshilumba, CERN, 03 February 2015

6 STIFFNESS REQUIREMENTS External forces (Water cooling, ventilation,…) High stiffness lateral stability requirement met passively (0.55kN/µm) Active control still needed for vertical direction (1kN/µm) D. Tshilumba, CERN, 03 February 2015

7 C ONTROL FORCE REQUIREMENTS Assuming P controller Control force for ground motion compensation (~10N integrated RMS) Nanopositioning force (~50N integrated RMS) D. Tshilumba, CERN, 03 February 2015

8 F UNCTIONAL AND PERFORMANCE REQUIREMENTS ParametersValue Resolution<0.25nm Precision0.25nm Stroke± 3mm step displacement0.25 up to 50nm Speed10μm/s Rise time1ms Settling time5ms Control bandwidth300Hz Stiffness (vertical/lateral) 1/0.55 kN/μm Vertical force (dynamic) 50N Horizontal force (dynamic) 30N D. Tshilumba, CERN, 03 February 2015

9 One single stage: Flexure lever mechanism Possible monolithic design No friction No backlash No wear Avoid plastic deformation! Effect on the dynamics of the system n benefic effect on the dynamics of the system Parameters to consider Coupling stiffness Pivot stiffness Intrinsic flexure stiffness Effect on the effective attenuation factor O PTIONS TO FULFIL THE REQUIREMENTS D. Tshilumba, CERN, 03 February 2015

10 One single stage: active feedback Features: Bandwidth increase Higher robustness to disturbance at low frequency Removal of steady state error O PTIONS TO FULFIL THE REQUIREMENTS D. Tshilumba, CERN, 03 February 2015

11 O PTIONS TO FULFIL THE REQUIREMENTS Coarse – fine resolution approach Improvement of Coarse stage (Juha Kemppinen) Improvement in the WPS measurement speed Improvement in precision via feedback loop Improvement of fine stage Higher stiffness Larger stroke (>200μm)  Compensation of thermal loads in tunnel  Beam time > 50 days D. Tshilumba, CERN, 03 February 2015

12 A CTUATORS Lorentz actuators Based on Lorentz force Linear: Zero stiffness Resolution dependent on amplifier Stroke: up to 75mm Heat dissipation Compatibility with collider environment? D. Tshilumba, CERN, 03 February 2015

13 A CTUATORS Hydraulic actuators Based on hydraulic pressure High stiffness achievable: Resolution dependent of control valves Stroke: >>1mm Friction between cylinder and piston Susceptible to leakage D. Tshilumba, CERN, 03 February 2015

14 A CTUATORS Piezoelectric actuators Based on inverse piezo effect Piezo stacks High stiffness (480N/μm) Limited stroke: up to 0.2% Piezo stepper Lower stiffness (150N/μm) Higher stroke (20mm) No Heat dissipation Compatible with collider environment D. Tshilumba, CERN, 03 February 2015

15 A CTUATORS C OMPARISON ResolutionStiffnessStrokeRemarks Lorentz++++ Compatibility to external magnetic field hydraulic++++ Reliability Piezo stack+++ +Lack in stroke Piezo stepper Lack in stiffness Piezo stepper: good candidate for mechanical attenuation D. Tshilumba, CERN, 03 February 2015

16 I NTERMEDIATE C ONCLUSION Overview of the current system Requirements for Nano-positioning summarized Alternatives to increase the range single stage Passive mechanical solution Active solution coarse-fine stage Comparison of classical actuators Piezo stepper + mechanical attenuation D. Tshilumba, CERN, 03 February 2015

17 U PGRADE T YPE 1 Parasitic resonance modes Unexpected eigen modes detected by EMA between 30Hz and 50Hz Suspect root cause: connection stiffness between components Bolting: up to 40% drop in eigen frequency Gluing: up to 8.5% drop in eigen frequency Courtesy of M. Guinchard D. Tshilumba, CERN, 03 February 2015

18 U PGRADE T YPE 1 Parasitic resonance modes Problematic region: base plate Improvement after gluing instead of bolting: lowest eigen mode at 50Hz Courtesy of M. Guinchard D. Tshilumba, CERN, 03 February 2015

19 U PGRADE T YPE 1 Parasitic resonance modes Further improvement: Monolithic base plate design Additional stiffeners D. Tshilumba, CERN, 03 February 2015

20 U PGRADE T YPE 1 Roll motion reduction: parallel kinematics Permissible roll displacement: 100μrad Aluminum eccentric shear pins 5.15μrad/μm coupling Alternative: rotational symmetry hinges 0.47μrad/μm coupling Features: Less components Tunable translational stiffness Design optimization required (Space availability) D. Tshilumba, CERN, 03 February 2015

21 U PGRADE T YPE 1 Roll motion reduction: parallel kinematics Permissible roll displacement: 100μrad Rotational symmetry hinges 0.47μrad/μm coupling Lost motion: 5% (vertical) High resonance frequencies D. Tshilumba, CERN, 03 February 2015

22 U PGRADE T YPE 1 Roll motion reduction: serial kinematics Permissible roll displacement: 100urad Further coupling reduction 0.094urad/um coupling Lost motion: 0.02% (vertical) Design optimization required More compact Avoid flexible deformation modes D. Tshilumba, CERN, 03 February 2015

23 C ONCLUSION Actuator requirements defined Existing actuation technologies Vs performance requirements Introduction of concepts for further study to increase the range Type 1 upgrade proposals under study D. Tshilumba, CERN, 03 February 2015

24 F UTURE WORK Optimize the presented alternative concepts for the kinematic decoupling in type 1 stage Design a 1dof extended nanopositioning stage with attenuation mechanism + Experimental validation Secondment at TUDelft and TNO almost finished D. Tshilumba, CERN, 03 February 2015

25 P IEZO STEPPER S PECS Linear Piezoelectric motor Motion specifications Value Nominal elongation without external force or restraint (closed loop) 20 mm Closed loop resolution 5 nm Open loop resolution 0.03 nm Minimal incremental displacement (in step mode) 10 nm Maximum velocity (in nano stepping mode) 0.4 mm/s Load and dimensional specifications Value Stiffness in motion direction 150 N/ μ m Holding force capacity (passive) 800 N Maximum lateral force allowed 20 N Maximum torque allowed in the direction of the driving rod 0.5 Nm Maximum torque allowed generated by lateral force 0.5 Nm Fully extended maximum length125 mm Maximum lateral dimension 80 mm Maximum mass of the actuator 1.5 kg D. Tshilumba, CERN, 03 February 2015

Presentation title _ Name of the student _ date of the presentation 26 I NCREASE IN RANGE Concept : mechanical amplification Perfect lever:

Presentation title _ Name of the student _ date of the presentation 27 I NCREASE IN RANGE Real lever mechanism Parameters to consider Coupling stiffness Pivot stiffness Intrinsic flexure stiffness Effect on the effective attenuation factor

Presentation title _ Name of the student _ date of the presentation 28 D ISTURBANCE SOURCES Ground motion External forces (Water cooling, ventilation,…)

Presentation title _ Name of the student _ date of the presentation 29 F UNCTIONAL AND PERFORMANCE REQUIREMENTS ParametersValue Resolution0.25nm Precision1nm Stroke± 3mm step displacement0.25 up to 1 Speed10μm/s Rise time1ms Settling time5ms Control bandwidth300Hz Stiffness (vertical/lateral) 1/0.55 kN/μm Vertical force (static/dynamic) 3MN/50N Horizontal force (static/dynamic) 1.7MN/30N FeedbackFeedforward StaticAlignment Magnetic measurement DynamicVibration isolation Nanopositioning

Presentation title _ Name of the student _ date of the presentation 30 O PTIONS TO FULFIL THE REQUIREMENTS One overall actuator low physical stiffness + control stiffness High physical stiffness enormous force required (~3MN) challenges in the dynamics (control bandwidth, stability of the controller)

Presentation title _ Name of the student _ date of the presentation 31 A CTUATORS Reluctance actuators

Presentation title _ Name of the student _ date of the presentation 32 D ISTURBANCES AND STABILITY REQUIREMENTS Ground motion local ground vibration (>1Hz) relative ground motion between distant points (<<1Hz) Water cooling vibrations Thermal load from power dissipation