Vibrations effect on 1nm focussing
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Vibrations effect on 1nm focussing. K. Evans-Lutterodt NSLS-II VTG Januaury 22 2007. Outline. Background and important optics metrics Simple optics layout How we see the source; some stability reqs More complex layout (Waveguide) Can we position with 1nm beam sufficient accuracy?.

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Vibrations effect on 1nm focussing

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Vibrations effect on 1nm focussing

Vibrations effect on 1nm focussing

K. Evans-Lutterodt

NSLS-II VTG

Januaury 22 2007


Outline

Outline

  • Background and important optics metrics

  • Simple optics layout

    • How we see the source; some stability reqs

  • More complex layout (Waveguide)

  • Can we position with 1nm beam sufficient accuracy?


Towards 1nm x ray optics

Towards 1nm X-ray Optics

Figure courtesy of C. Jacobsen

  • Future

  • It can be done: There is no physical reason we cannot get to 1nm

  • However, it will take resources and a targeted effort.


Basic issues

Basic Issues

  • Metrics

  • Numerical Aperture and resolution

  • Depth of field

  • Aperture

  • Efficiency

  • Chromaticity

  • Modulation Transfer Function

Resolution of 1nm at l=1A requires NA < 0.1

If resolution is 1nm

=> then DOF =27nm


Simplest configuration

Simplest configuration

Mono deleted for clarity


Order of magnitudes for stability

Order of magnitudes for stability

 ~ 10 microns(v) x 40 microns (h)

Slit down in the horizontal to get 10 by 10.

Demagnify by 104 to get 1nm.

For a source to lens of 50m, this implies 5mm focal length.

If you include details, we expect focal lengths of between 1 to 5mm

(We would really like to get out to 100mm, but this is probably too tough, Aperture)

Main point: Easy to integrate lens and sample stage monolithically.


We already mount optics and sample monolithically

We already mount optics and sample monolithically


Stability of e beam is crucial for effective source size

Stability of e-beam is crucial for effective source size

  • Position of electron beam translates directly into stability of image.

  • Typical tolerance is 10% if e-beam size; 0.3microns?.

  • Angular stability?

L

Angular uncertainty ~ (0.3 microns/ 3 meter) ~ 1e-7 radians


How the stability comes in

How the stability comes in

A: Size

If sigma stability is 10%, then stability adds negligibly to size

B: Intensity

If you are measuring fluorescence intensity, and we assume a gaussian profile

And we want to keep signal intensities within 1%:

1% criterion

5% criterian


Off axis abberrations

Off-axis Abberrations

Using zone plate as a guide: will have to revisit this in optics R&D

Aberration angular field of view , , is given by

Using N=1e5, F=0.1, =0.1nm

  1e-3 radians which is much bigger than everything else so not a problem.


More complicated optics layout

More complicated optics layout


Main advantages of waveguide geometry

Main advantages of waveguide geometry

  • More stable, but more optics so more loss.( 4.7% experimental state of the art, but not optimal)

  • Wave guide provides new source size (50nm)

  • Allows better working distances

  • All fluctuations in position,angle translate to intensity fluctuations

  • Attempt to do normalization, not invented yet for small WD.


Can we position with 1nm accuracy

Can we position with 1nm accuracy?

It is difficult, but possible.

Worry about materials, and temperature control.


Commercial 0 02nm positioner

Commercial 0.02nm positioner


Non commercial aps rd

Non Commercial (APS-RD)


Vibrations effect on 1nm focussing

Timescales

  • Time scale : 1second /scan.

  • If normalization invented then stability to 1 second ok

  • If not ~2 hour full scan stability.


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