the nanobender: a new x-ray mirror bender with nanometer ... · carles colldelram medsi2016...

Carles Colldelram MEDSI2016 Barcelona 16/09/2016

The Nanobender: a New X-Ray Mirror Bender with Nanometer Figure

CorrectionCarles Colldelram1, Josep Nicolas2, Claude Ruget1Llibert Ribo1, Albert Tomàs3, Carlos Martín-Nuño3,

David Úbeda31. ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

2. SLAC national accelerator laboratory, Menlo Park, United States3. Sener Ingenieria y Sistemas, Cerdanyola del Vallès, Barcelona, Spain


Summary 2

Presentation Summaryo Precedents

o New concepts

o Bender design

o Correctors design

o Construction

o Measurements & Results

o Next Steps

o Active Optics

o Conclusions


Precedents 3

o Protein Crystallography Beam Lineo Vertical Focusing Mirror: Outsourced

o Include a Gravity compensatorso We request to place more compensator

to play with figure correction

ALBA BL13 Beam Line


Precedents 2010 4

BL13 VFM Optimization

o We corrected the slope error by means the gravity compensatorso Optimization of the compensators positiono Manual compensatorso This compensators are not thought for this function: not friendly

adjustment

This 300 mm long mirror was optimized from 0,242 µrad to 0,055 µradBy means two of the gravity compensators both pushing from below

Mirror by InsyncBender by Irelec

Before Correction: 0,242 µradAfter Correction: 0,055 µrad


Precedents 2012 5

BL13 VFM In-Situ measurement

-150 -100 -50 0 50 100 150-2

-1

0

1

2

3

4

Position (mm)

Res

idua

l Pro

file

(nm

)

NOMIn situ

In-Situ measurement after 2 years agrees with the laboratory optimization and measurement

The simulation of the beam by means ray-tracing with the measured corrected mirror

figure


New concepts 6

Geometrical vs Force constrains

Applied Forces

Optical surface with slope error

The hard way The soft way

…By means of stable-force actuators”

By means Rigid mechanics which introduce the required deformation vs


Bender design

Bender Mechanism:Encapsulated

Correctors

Lay-out

Mirror

PusherPuller


Bender design

Bender Mechanismo Based on compression springs

o Convectional motion system for the compression

Range

o Force gauge measurement

o Off-axis relieving Force transmission

o Punctual contacts

o Flexion at 25 mm from the support

o Radius of curvature: 500 m

o Forces up to 500 N

o Force Resolution: 0,001 N

o Focus independent of figure correction


Bender design

The correctorso 22 mm width

o High resolution force correctors

o Ultra low k springs

o Forces up to 40 N, ±20 N.

o Resolution up to 0,001 N

o High stability:

o Independent to the set curvature, no

crosstalk

o No parasitic torsions

o UHV compatible (adaptive optics)


Construction


Measurements & results

ALBA NOMo This is a 1,5 m long highly accurate scanning

deflectometer by air bearings

o Ironless linear motor

o Optical set-upo Autocolimatoro Pentaprism

Date07/13 07/14 07/15 07/16

Tem

pera

ture

[deg

C]

22.3

22.305

22.31

22.315

22.32

22.325

22.33

22.335

22.34

22.345

22.35

The laboratory temperature is stabilized by means of a PID controlled post-heating system



Mathematical deformation Modelo LINEAR model, allows superposition

o Curvature of deformation is a piecewise linear function

o Surface deformation is a piecewise cubic polynomial

Euler – Bernoulli law

For an induced deformation of >600 nmafter removing curvature, the model isaccuarate below 1 nm



Bending performance

Strain Gauge [N]-55 -50 -45 -40 -35

E3-

Err

or [n

rad

RM

S]

-40

-30

-20

-10

0

10

20

30

40E3 vs Gauge

Strain Gauge [N]-55 -50 -45 -40 -35

E2-

Err

or [n

rad

RM

S]

-100

-80

-60

-40

-20

0

20

40

60

80

100E2 vs Gauge

Bending range 0-500 NBending resolution



Correctors performance

20 N is the force estimated to correct 0.5 μrad

rms mirrors for errors with period down to 22 mm

Resolution of 0.001N allows sub nanometer

correction, as well as stability

Measurement count5 10 15 20 25 30 35 40

Forc

e in

crem

ent [

mN

]

0

1

2

3

4

5

6

Resolution: 250 steps

Experiment count5 10 15 20

Forc

e D

evia

tion

[mN

]

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2Contact repeatability at 3.23 N, σ=0.47 mN



Correctors performance

Repeatability on recovering a position between

motions to random points

Stability for 130h



Mirror OptimizationInitial slope error: 0,87 µrad RMSCorrected slope error: 0,115 µrad RMS

Position [mm]-200 -100 0 100 200

Hei

ght e

rror [

nm]

-5

-4

-3

-2

-1

0

1

2

3

4

5

AchievedOptimalDifference

Position [mm]-200 -100 0 100 200

Hei

ght e

rror [

nm]

-50

-40

-30

-20

-10

0

10

20

30

40

50

Initial surface error: 23,2 nm RMS Corrected surface error: 0,858 nm RMS

The mathematical model:

• Optimizes the correctors position

• Optimizes the corrector force (and its sense)

The model predicts the deformation of the mirror with accuracy better than 0.08 nm RMS


Next steps

Corrector Improvements

o Corrector Repeatability: Done

o Remove the bender mechanics encapsulation

o Compact the bender mechanism

o Compact the correctors

Repeatability Long Range

Repeatability Short Range


Next steps

Corrector Improvementso -k magnet system for spring k compensation

o Insensibility to magnet position in a ±1 mm

Mirr. Position [mm]-3 -2 -1 0 1 2 3

Forc

e D

evia

tion

[N]

-0.02

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.162.92 N3.54 N4.09 N6.30 N10.95 N


Next steps

Corrector ImprovementsTo be implemented soon

o Spring length reduction by means the force compensation system:o Test prototype done and measured.o -k spring with magnet.

o Removal of the bearing friction on the spring articulation:o Test prototype doneo Zero-torque frictionless articulationo By means a flexure and magnet system

See the poster :ID: 2029 - MOPE01 Stabilization Methods for Force Actuators and Flexures

ES P201631142ES P201630506ES P201530735

Three patens


Next steps

Active Optics

o With such figure error accuracy and resolution it is possible to

correct beam wavefront distortions

o With a double spring the corrector can switch from pusher to

puller just by moving along the range.

o Change the Stepper motor for a UHV compatible one.

o mount as many correctors as space allows.


Conclusions

o The proposed solution of a bender with figure correctors based in force

constrains works at nanometer level

o A mirror bender with correctors without crosstalk is achieved.

o A very stable correctors have been design and implemented.

o New –k compensated correctors have been designed and tested. They keep

force constant within 1 mN in a range of motion of the mirror up to 2 mm.

o New, frictionless, torque free articulation has been designed, and is being

currently tested.


Acknowledgments

Joan Casas

Jose Ferrer

Gabriel Peña

Llibert Ribó

Pablo Pedreira

…


23

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